Ultrasonography for confirmation of gastric tube placement

  • Review
  • Diagnostic

Authors


Abstract

Background

Gastric tubes are commonly used for the administration of drugs and tube feeding for people who are unable to swallow. Feeding via a tube misplaced in the trachea can result in severe pneumonia. Therefore, the confirmation of tube placement in the stomach after tube insertion is important. Recent studies have reported that ultrasonography provides good diagnostic accuracy estimates in the confirmation of appropriate tube placement. Hence, ultrasound could provide a promising alternative to X-rays in the confirmation of tube placement, especially in settings where X-ray facilities are unavailable or difficult to access.

Objectives

To assess the diagnostic accuracy of ultrasound for gastric tube placement confirmation.

Search methods

We searched the Cochrane Library (2016, Issue 3), MEDLINE (to March 2016), Embase (to March 2016), National Institute for Health Research (NIHR) PROSPERO Register (to May 2016), Aggressive Research Intelligence Facility Databases (to May 2016), ClinicalTrials.gov (to May 2016), ISRCTN registry (May 2016), World Health Organization International Clinical Trials Registry Platform (to May 2016) and reference lists of articles, and contacted study authors.

Selection criteria

We included studies that evaluated the diagnostic accuracy of naso- and orogastric tube placement confirmed by ultrasound visualization using X-ray visualization as the reference standard. We included cross-sectional studies, and case-control studies. We excluded case series or case reports. Studies were excluded if X-ray visualization was not the reference standard or if the tube being placed was a gastrostomy or enteric tube.

Data collection and analysis

Two review authors independently assessed the risk of bias and extracted data from each of the included studies. We contacted authors of the included studies to obtain missing data.

Main results

We identified 10 studies (545 participants and 560 tube insertions) which met our inclusion criteria.

No study was assigned low risk of bias or low concern in every QUADAS-2 domain. We judged only three (30%) studies to have low risk of bias in the participant selection domain because they performed ultrasound after they confirmed correct position by other methods.

Few data (43 participants) were available for misplacement detection (specificity) due to the low incidence of misplacement. We did not perform a meta-analysis because of considerable heterogeneity of the index test such as the difference of echo window, the combination of ultrasound with other confirmation methods (e.g. saline flush visualization by ultrasound) and ultrasound during the insertion of the tube. For all settings, sensitivity estimates for individual studies ranged from 0.50 to 1.00 and specificity estimates from 0.17 to 1.00. For settings where X-ray was not readily available and participants underwent gastric tube insertion for drainage (four studies, 305 participants), sensitivity estimates of ultrasound in combination with other confirmatory tests ranged from 0.86 to 0.98 and specificity estimates of 1.00 with wide confidence intervals.

For the studies using ultrasound alone (four studies, 314 participants), sensitivity estimates ranged from 0.91 to 0.98 and specificity estimates from 0.67 to 1.00.

Authors' conclusions

Of 10 studies that assessed the diagnostic accuracy of gastric tube placement, few studies had a low risk of bias. Based on limited evidence, ultrasound does not have sufficient accuracy as a single test to confirm gastric tube placement. However, in settings where X-ray is not readily available, ultrasound may be useful to detect misplaced gastric tubes. Larger studies are needed to determine the possibility of adverse events when ultrasound is used to confirm tube placement.

Résumé scientifique

Les ultrasons pour confirmer le positionnement d'une sonde gastrique

Contexte

Les sondes gastriques sont couramment utilisées pour administrer des médicaments ou une alimentation entérale aux personnes ne pouvant plus avaler. Une alimentation au travers d'un tube placé dans la trachée peut entraîner une pneumonie grave. Par conséquent, confirmer le placement de la sonde dans l'estomac après son insertion est important. De récentes études ont rapporté que les ultrasons fournissent une bonne précision diagnostique pour confirmer que le placement de la sonde est approprié. Ainsi, les ultrasons pourraient fournir une alternative prometteuse à la radiographie pulmonaire pour confirmer le placement de la sonde, en particulier dans des contextes où des services de radiographie ne sont pas disponibles ou difficiles d'accès.

Objectifs

Évaluer la précision diagnostique des ultrasons pour confirmer la mise en place des sondes gastriques.

Stratégie de recherche documentaire

Nous avons consulté la Bibliothèque Cochrane (2016, numéro 3), MEDLINE (jusqu'en mars 2016), Embase (jusqu'en mars 2016), le registre PROSPERO du National Institute for Health Research (NIHR) (jusqu'en mai 2016), les bases de données de l'Aggressive Research Intelligence Facility (jusqu'en mai 2016), ClinicalTrials.gov (jusqu'en mai 2016), le registre ISRCTN (mai 2016), l'ICTRP de l'OMS (jusqu'en mai 2016), les références bibliographiques des articles et nous avons contacté les auteurs des études.

Critères de sélection

Nous avons inclus les études ayant évalué la précision diagnostic du positionnement de sondes naso-gastriques ou oro-gastriques confirmée par visualisation d'ultrasons avec la visualisation de radiographies comme référence. Nous avons inclus les études transversales et les études cas-témoins. Nous avons exclus les séries de cas ou les rapports de cas. Les études ont été exclues lorsque la visualisation de radiographies n'était pas la norme de référence ou si la sonde placée était une sonde de gastrostomie ou une sonde entérique.

Recueil et analyse des données

Deux auteurs de la revue ont indépendamment évalué le risque de biais et extrait les données de chacune des études incluses. Nous avons contacté les auteurs des études incluses afin d'obtenir les données manquantes.

Résultats principaux

Nous avons identifié 10 études (545 participants et 560 insertions de sondes) répondant à nos critères d'inclusion.

Aucune étude n'a été évaluée comme étant à faible risque de biais ou présentant de faibles inquiétudes dans tous les domaines de l'évaluation QUADAS-2. Nous avons jugé que seules trois (30 %) des études étaient à faible risque de biais de sélection des participants car les ultrasons avaient été réalisés après confirmation du positionnement suite au recours à d'autres méthodes.

Peu de données (43 participants) étaient disponibles concernant la détection d'un mauvais placement (la spécificité) en raison de la faible incidence des mauvais placements. Nous n'avons pas réalisé de méta-analyse en raison de l'hétérogénéité considérable des tests d'indice tels que la différence d'écho fenêtre, la combinaison des ultrasons à d'autres méthodes (par ex. la confirmation par irrigation saline visualisée par ultrasons) et les ultrasons au cours de l'insertion de la sonde. Dans tous les contextes, les estimations de la sensibilité pour les études individuelles allaient de 0,50 à 1,00 et les estimations de la spécificité de 0,17 à 1,00. Dans les contextes où les rayons X n'étaient pas facilement disponibles et où les participants ont subi l'insertion d'une sonde gastrique pour un drainage (quatre études, 305 participants), les estimations de la sensibilité des ultrasons en combinaison à d'autres tests de confirmation variaient de 0,86 à 0,98 et les estimations de la spécificité de 1,00 avec de larges intervalles de confiance.

Pour les études utilisant les ultrasons seulement (quatre études, 314 participants), les estimations de la sensibilité allaient de 0,91 à 0,98 et les estimations de la spécificité de 0,67 à 1,00.

Conclusions des auteurs

Parmi les 10 études ayant évalué la précision diagnostique du positionnement des sondes gastriques, peu d'études avaient un faible risque de biais. Sur la base de ces preuves limitées, les ultrasons n'ont pas suffisamment de précision en tant que test unique pour confirmer la mise en place des sondes gastriques. Cependant, dans des contextes où des radiographies ne sont pas facilement disponibles, les ultrasons peuvent être utiles pour détecter un positionnement incorrect d'une sonde gastrique. Des études à plus grande échelle sont nécessaires pour déterminer la possibilité d'événements indésirables lorsque les ultrasons sont utilisés pour confirmer le positionnement des sondes.

アブストラクト

超音波診断装置による胃管留置の確認

背景

胃管は嚥下が困難な人々の薬剤や栄養剤投与に広く用いられている。気管に誤って留置されたチューブで栄養剤投与を行うと重篤な肺炎の原因となりうる。それゆえ、胃管チューブの挿入のあとにチューブが胃内に留置できているかの確認は重要である。最近の研究では、超音波診断装置は適切な胃管チューブの位置確認においてよい診断精度を示すと報告している。よって超音波診断装置は胃管チューブの位置確認のレントゲンの代替として、期待が持てる可能性があるといえる。それは特に放射線診断装置が利用できないセッティングにおいて特に期待される。

目的

超音波診断装置の胃管チューブの位置確認における診断精度を評価する。

検索戦略

コクランライブラリー (2016, Issue 3), MEDLINE ( 2016年 3月まで), Embase (2016年3月まで), National Institute for Health Research (NIHR) PROSPERO Register (2016年5月まで), Aggressive Research Intelligence Facility Databases (2016年5月まで), ClinicalTrials.gov (2016年5月まで)ISRCTN registry (2016年5月まで), World Health Organization International Clinical Trials Registry Platform (2016年5月まで)を検索した。さらに、文献のリファレンスリストの参照と著者への問い合わせを行った。

選択基準

経鼻または経口の胃管チューブの位置確認を超音波診断装置で行った際の診断精度を放射線診断装置をリファレンススタンダードとして評価している研究をレビューに組み入れた。横断研究とケースコントロール研究を組み入れた。症例報告、ケースシリーズは除外した。超音波診断装置をリファレンススタンダードにしていない研究や、胃瘻チューブや胃を超えて腸管に留置されたチューブに関する研究を除外した。

データ収集と分析

組み入れ研究に対して、2人のレビュー著者が独立してバイアスリスクの評価とデータ抽出を行った。組み入れ研究の足りないデータは著者に問い合わせを行った。

主な結果

組み入れ基準を満たす10の研究があった(545人の研究参加者の560のチューブ留置)。

QUADAS-2のバイアスリスクがすべてのドメインにおいて低と評価された研究はなかった。患者選択のドメインにおいて3つの研究(30%)のみでバイアスリスクを低と評価した。なぜなら他の研究は他の方法でチューブの位置が正しいことを確認した後に超音波検査を行っていたからである。

誤ったチューブの位置の確認においてのデータはわずかであった(43人)。これは誤留置のインシデントが少なかったことが原因である。研究の異質性が無視できないため、メタアナリシスは行うことができなかった。異質性はたとえば、エコーウインドウの違い、超音波検査を他の確認方法と組み合わせて行っているなどであった。(生理食塩水をチューブにフラッシュして超音波で可視化するなど)また、エコーガイドでチューブの挿入に行っている方法などである。すべてのセッティングにおいての個別の研究の感度の推定値は0.50から1.00であった。特異度は0.17から1.00であった。放射線診断装置が迅速に利用できない場所での胃内ドレナージ目的の胃管チューブ挿入を受けた患者を対象とした場合(4つの研究、305人の研究参加者)での他の確認方法と組み合わせた感度の推定値は0.86から0.98であった。特異度は1.00であったが、信頼区間は広かった。

超音波診断装置のみでの診断精度を評価した研究(4つの研究、314の研究参加者)は、感度の推定値は0.91から0.98であった。特異度の推定値は0.67から1.00であった。

著者の結論

評価された10の胃管留置の診断精度を調べた研究のうち、バイアスリスクが低い研究は少なかった。限られたエビデンスに基づいたものではあるが、超音波診断装置の単独では胃管留置の確認のためのテストとして不十分であるといえる。しかしながら、放射線診断装置が迅速に利用できないセッティングにおいて、誤留置されたチューブの検出のために有用といえるかもしれない。超音波診断装置が胃管の留置に用いられた場合の有害事象の可能性に対してさらなる大規模な研究が求められる。

Plain language summary

Ultrasound scan for confirmation of gastric tube placement

Background

Each year approximately one million people receive a tube feeding (gastric tube) in the US. Gastric tubes are commonly used for giving drugs and nutrition directly into the gastrointestinal tract (tube that digests food) for people who are unable to swallow. Feeding via a tube that is misplaced in the trachea (wind pipe) can result in severe pneumonia (infection of the lungs). Therefore, confirmation of tube placement in the stomach after tube insertion is important. Gastric tubes are also used to reduce the pressure of the stomach after providing breathing assistance through masks, which is mainly used in resuscitation. Medical ultrasound is one of the diagnostic imaging techniques using sound waves to create images of the inside of the body. Recent studies suggest that ultrasound provides good diagnostic accuracy in the confirmation of appropriate tube placement. Hence, ultrasound could provide a promising alternative to X-rays in confirming tube placement, especially where X-ray facilities are unavailable or difficult to access.

Study characteristics

Studies included in this review are current to March 2016. We included 10 studies involving 545 participants for evaluation of the diagnostic accuracy of ultrasound for confirmation of gastric tube placement.

Key results

Most studies showed good performance for correct placement of the tube. However, few data were available for incorrect placement of the tube and the possible complications of a misplaced tube. Among the included studies, only 43 participants had a misplaced tube. None of the studies reported complications during ultrasound use. Three methods of ultrasound were reported: neck approach, upper abdominal (tummy) approach and a combination of both. No included studies indicated that ultrasound had sufficient accuracy as a single test for the confirmation of gastric tube placement for feeding. In contrast, ultrasound combined with other tests (e.g. saline flush visualization (pushing salt solution through the tube and seeing it inside the stomach by ultrasound)) might be useful for the confirmation of tubes used for gastric drainage.

Limitations of the review

Generally, the studies were of low or unclear methodological quality. We considered only three (30%) of the 10 included studies to be representative of patients in practice because they performed ultrasound after they confirmed correct position by other methods. The studies reported a variety of results for incorrect tube placement.

Future research

Larger studies are needed to investigate whether ultrasound could replace X-rays for confirming gastric tube placement, as well as whether ultrasound could decrease severe complications, such as pneumonia, from a misplaced tube.

Résumé simplifié

Les ultrasons pour confirmer le positionnement d'une sonde gastrique

Contexte

Chaque année, environ un million de personnes reçoivent une alimentation au travers d'un tube (une sonde gastrique) aux États-Unis. Les sondes gastrique sont couramment utilisées pour administrer des médicaments et de la nourriture directement dans le tractus gastro-intestinal (un tube permettant de digérer les aliments) pour les personnes ne pouvant pas avaler. L'alimentation offerte au travers d'un tube placé par erreur dans la trachée (un conduit où passe l'air respiré) peut entraîner une pneumonie grave (une infection des poumons). Par conséquent, la confirmation du positionnement de la sonde dans l'estomac après l'insertion est importante. Les tubes gastriques sont également utilisés pour réduire la pression dans l'estomac après avoir offert une assistance respiratoire au travers d'un masque, principalement en cas de réanimation. Les ultrasons médicaux sont une des techniques d'imagerie diagnostique utilisant des ondes sonores pour créer des images de l'intérieur du corps. De récentes études suggèrent que les ultrasons permettent une bonne précision diagnostique pour confirmer que le placement de la sonde est approprié. Par conséquent, les ultrasons pourraient être une alternative prometteuse à la radiographie pulmonaire pour confirmer le placement des sondes, en particulier lorsque les services de radiographie ne sont pas disponibles ou difficiles d'accès.

Caractéristiques de l'étude

Les études incluses dans cette revue sont à jour en mars 2016. Nous avons inclus 10 études portant sur 545 participants et ayant pour objectif d'évaluer la précision diagnostique des ultrasons pour confirmer le positionnement des sondes gastriques.

Principaux résultats

La plupart des études ont montré une bonne performance pour placer correctement les sondes. Cependant, peu de données étaient disponibles concernant les sondes placées incorrectement et les complications possibles d'une sonde mal placée. Parmi les études incluses, seuls 43 participants avaient une sonde mal placée. Aucune des études n'a rapporté de complications pendant l'utilisation des ultrasons. Trois techniques de réalisation des ultrasons ont été rapportées : l'approche par le cou, l'approche par la partie supérieure de l'abdomen (le ventre) et une combinaison des deux. Aucune des études incluses n'a indiqué si les ultrasons étaient suffisamment précis en tant que test unique pour confirmer le positionnement de la sonde gastrique pour une alimentation. En revanche, les ultrasons associés à d'autres tests (par exemple, la visualisation de l'irrigation saline (injecter une solution saline à travers la sonde et l'observer à l'intérieur de l'estomac par ultrasons)) pourraient être utiles pour confirmer le placement des tubes utilisés pour le drainage gastrique.

Limitations de la revue

Généralement, les études étaient de qualité méthodologique faible ou incertaine. Nous avons considéré que seules trois (30 %) des 10 études incluses étaient représentatives des patients dans la pratique, car dans celles-ci les ultrasons ont été réalisés après que le positionnement normal ait été confirmé par d'autres méthodes. Les études ont rapporté une variété de résultats lorsque les sondes étaient placées incorrectement.

Recherches futures

Des études à plus grande échelle sont nécessaires pour déterminer si les ultrasons pourraient remplacer les rayons X pour confirmer la mise en place d'une sonde gastrique, et pour évaluer si les ultrasons pourraient permettre de réduire les complications graves, telles que la pneumonie résultant d'un tube mal placé.

Notes de traduction

Traduction réalisée par Martin Vuillème et révisée par Cochrane France

平易な要約

超音波検査による胃管の位置確認

背景

毎年、およそ100万人の人々が米国において胃管留置を受けているといわれている。胃管は薬や栄養を消化管(食事を消化する場所)に直接投与するために一般的に用いられている。誤った位置である気管(のどの空気の通り道)に留置されたチューブによって栄養投与された場合、重篤な肺炎(肺の感染症)になりうる。それゆえ、チューブを留置した後に場所をチューブが胃にあることを確認することは重要である。また、胃管は蘇生処置においてマスクによる呼吸補助のあとに上昇した胃の中の空気圧を減らすためにも用いられている。医療用の超音波装置は音の波を利用して体の中を可視化する画像診断技術の一つである。最近の研究では、超音波診断装置は胃管の適切な位置の確認において良い診断精度をもつと報告されている。よって超音波診断装置は胃管チューブの位置確認のレントゲンの代替として、期待が持てる可能性があるといえる。それは特に放射線診断装置が利用できないセッティングにおいて特に期待される。

研究の特性

このレビューは2016年の3月までの研究を含んでいる。545人の参加者を含む胃管の位置確認における超音波診断装置の診断精度を評価した10個の研究をレビューに組み入れた。

主な結果

ほとんどの研究は胃管が正しい位置にある際によい精度で検出できていた。しかしながら、誤った位置にある胃管を検出することや誤った位置に胃管が挿入されることにより起こりうる有害事象に関してのデータはわずかであった。レビューに組み入れられた研究のうちでは、チューブが誤った位置に挿入された参加者は43人のみであった。超音波診断装置による有害事象を報告している研究はなかった。超音波診断装置の使用に際して3つの方法が報告されていた。それは、首からのアプローチ、上腹部(みぞおち)からのアプローチ、両方を行うアプローチであった。組み入れられた研究のうち、栄養投与のためのチューブの位置確認のためには、単一の検査として十分な診断精度を示している研究はなかった。それに対して、他の検査と組み合わせて超音波検査を行っている場合(チューブを通した生理食塩水の胃内への注入による可視化など)胃のドレナージ目的のチューブの位置確認としては有用かもしれない。

レビューのリミテーション

概して、レビューされた研究は方法論的に質が不明や低いものであった。10個の組み入れられた研究のうち、3つの研究(30%)しか、実際の臨床現場での状況に近いといえるものがなかった。なぜなら、その他の研究は正しい位置が他の検査で確認できてから超音波検査の診断精度を評価していたからである。それらの研究は誤った位置にあるチューブの検出において統一性のない結果を示していた。

今後の研究

超音波診断装置が用いられた場合に誤ったチューブによる肺炎などの重篤な有害事象を減らすことができるのかだけでなく、超音波診断装置が胃管の位置確認において、レントゲンの代替となりうるのかの点に関して調査したさらなる大規模な研究が求められる。

訳注

《実施組織》辻本 啓、片岡裕貴 翻訳[2017.9.26]
《注意》この日本語訳は、臨床医、疫学研究者などによる翻訳のチェックを受けて公開していますが、訳語の間違いなどお気づきの点がございましたら、コクランジャパンまでご連絡ください。なお、2013年6月からコクラン・ライブラリーのNew review、Updated reviewとも日単位で更新されています。最新版の日本語訳を掲載するよう努めておりますが、タイム・ラグが生じている場合もあります。ご利用に際しては、最新版(英語版)の内容をご確認ください。《CD012083》

Background

Gastric tubes are commonly used for the administration of drugs and delivery of nutrition directly into the gastrointestinal tract (enteral feeding) for people who are unable to swallow (e.g. people after stroke, or who need respirator support) (NICE 2006; Samuels 2013). Placement of a gastric tube is performed by inserting the tube through the nose (nasogastric tube) or mouth (oral gastric or orogastric tube), down the oesophagus and into the stomach (ENA 2015; Samuels 2013). Generally, doctors or nurses insert the tubes by pushing the tube into the nose or mouth. Gastrectomy tubes (G-tubes) are a type of gastric tube inserted into the stomach; however, they are inserted via the abdominal wall rather than the nose or mouth. This review will focus on nasogastric and orogastric tubes.

Each year approximately one million people receive tube feeding in the US (Metheny 1999). Gastric tubes are also used for the decompression of the gastrointestinal tract after the application of a bag valve mask, which is mainly used in resuscitation (Chenaitia 2012). Gastric tubes, made primarily from flexible polyurethane, and sometimes latex, silicone or polyurethane, require regular replacement if used for extended periods (Samuels 2013). In addition, tubes sometimes require unscheduled replacement due to dislodgement caused by vomiting or blockages (Thomson 2000). Gastric feeding tubes are associated with the recognised risk of misplacement into the trachea (airway) through the larynx due to the close proximity of the larynx to the oesophagus. During insertion, the tubes might enter the trachea through the larynx. Feeding via a tube misplaced in the trachea can result in severe pneumonia, pneumothorax, empyema and pulmonary haemorrhage. Therefore, the confirmation of tube placement in the stomach after insertion is important (Kawati 2005). Recommended methods to confirm correct tube placement are X-ray visualization and suction of gastric fluids (AACCN 2009). In a prehospital situation, a combination of the suction method and auscultation is used (Chenaitia 2012).

Medical ultrasound is one of the diagnostic imaging techniques using ultrasound wave. Studies from the same research group have demonstrated that ultrasonography provides good diagnostic accuracy estimates in the confirmation of appropriate tube placement (Brun 2014; Chenaitia 2012). These studies focused on tube placement for decompression of the stomach after the administration of a bag valve mask in a prehospital situation where X-ray was not available. Therefore, ultrasound could provide a promising alternative to X-rays in the confirmation of tube placement, especially in settings where X-ray facilities are unavailable or difficult to use.

Target condition being diagnosed

Appropriate gastric tube placement for any reason.

Index test(s)

Ultrasound test for gastric tube confirmation that visualizes the tubes via both the neck and abdomen, regardless of frequency of ultrasound, probe shape (linear or convex) or probe size. The test is performed in both prone and sitting position and can also be performed at the bedside. Visualization of the tubes is generally from the neck, abdomen, or both. Direct visualization of tubes in the oesophagus or stomach is interpreted as correct placement. During visualization, saline or air flush of the tube may help to visualize it by showing dynamic fogging in the stomach (Kim 2012).

Clinical pathway

People may need a gastric tube for the administration of drugs, enteral feeding or drainage. In these situations, the gastric tube is inserted via the nose or mouth, down the oesophagus and into the stomach.

After the gastric tube is inserted, its location should be promptly confirmed before proceeding with feeding or drug administration (AACCN 2009). This is by either suction of gastric fluids (visual inspection of aspirate contents or checking of pH) or the auscultation method (instillation of air in the tube with sounds heard simultaneously through a stethoscope placed over the stomach region) or both may be performed as prior tests (AACCN 2009; Chenaitia 2012). Tube placement is usually confirmed by X-ray visualization of the tube (e.g. chest X-ray).

Ultrasound may be used as a replacement test for X-ray. During the test, saline or air flush of the tube may help to visualize it.

In addition, if the person with the tube placement has vomited, retched or coughed, or if oropharyngeal suction was needed, the tube will require regular checking every four hours during daily feeding or in cases of suspected tube dislodgement (Holland 2013).

Prior test(s)

Either suction of gastric fluids (visual inspection of aspirate contents) or the auscultation method (instillation of air in the tube with sounds heard simultaneously through a stethoscope placed over the stomach region), or both are possibly performed as prior tests (AACCN 2009; Chenaitia 2012). In a prehospital situation, a combination of the suction and the auscultation method is possibly used (Chenaitia 2012). If one of these tests showed misplacement, reinsertion of the tube is needed.

Role of index test(s)

The role of ultrasound is assumed as a replacement test for X-ray visualization. The downstream consequences according to the four test accuracy categories are as follows:

  • no need for further testing for TP (true positive) = correct gastric tube placement and correct visualization by ultrasound;

  • serious accidents of feeding via a tube misplaced in the trachea or no effective drainage of gastric contents via a tube misplaced in the trachea for FP (false positive) = incorrect gastric tube placement but not visualized by ultrasound;

  • useless reinsertion of the tube and retesting for FN (false negative) = correct gastric tube placement but not visualized by ultrasound;

  • safe feeding or effective drainage of gastric contents for TN (true negative) = incorrect gastric tube placement and correct visualization by ultrasound.

Alternative test(s)

X-ray visualization is generally used to assess appropriate tube placement (Bourgault 2009). Although the risk of cancer from X-rays is not conclusive, concerns regarding the risks associated with frequent exposure to X-rays exist (Berrington 2004).

In addition, pH test of aspirate is used. The National Patient Safety Agency reported if pH is between 1 and 5.5, it is safe to start feeding (Lamont 2011; National Patient Safety Agency 2011). If pH is between 5 and 6, it is recommended that checking of the pH with a competent colleague (double checking is needed because misinterpretations of pH is possible) (Lamont 2011).

Rationale

The use of ultrasonography to assess appropriate tube placement has the potential to reduce patient discomfort. Confirmation by X-ray visualization can be difficult for people with tube placement because they have to change their body position to have a hard film plate placed on their back, or stand up for scanning while dealing with uncomfortable tubes hanging from their nose or mouth. An ultrasound test, by comparison, can be performed at the bedside without the need for the person to sit up or change position, and can, therefore, reduce the discomfort of the procedure for the patient (Vigneau 2005).

Ultrasonography can also widen accessibility to confirmatory testing outside of the hospital environment. As some ultrasound devices are portable, medical care providers who visit patients in the home can use ultrasound to check appropriate tube placement. Patients need not visit the hospital for insertion and confirmation of nasogastric or orogastric feeding tubes, which is an important consideration in the primary care setting (Mariani 2010).

The National Patient Safety Agency recommends that before using feeding tubes, repeated placement checks should be performed by X-ray or pH of aspirate measured at least once daily (National Patient Safety Agency 2011). X-rays should be avoided for children as much as possible due to concerns about the risk of irradiation (Frush 2003). Although the dose of irradiation by chest or abdominal X-rays is small according to the linear non-threshold model used in risk assumption, reducing irradiation as much as possible is of value to people of all ages (Berrington 2004; CNSC 2013).

We hypothesized that ultrasound could be a beneficial alternative to X-ray visualization since ultrasound devices have become common not only in critical care but also in primary care or prehospital settings.

Objectives

To assess the diagnostic accuracy of ultrasound for gastric tube placement confirmation.

Secondary objectives

To assess the diagnostic accuracy of ultrasound for gastric tube placement confirmation in children (aged 16 years or less).

To investigate the potential sources of heterogeneity, we planned to assess the effects of the following factors on the diagnostic accuracy of ultrasound: body mass index (BMI), clinical setting (emergency setting or not), tube diameter and area of visualization (the neck, abdomen, or both).

Methods

Criteria for considering studies for this review

Types of studies

We included studies that evaluated the diagnostic accuracy of naso- and orogastric tube placement confirmed by ultrasound visualization and using X-ray visualization as the reference standard. We included cross-sectional studies and case-control studies. We excluded case series or case reports (Bossuyt 2008). We excluded studies where X-ray visualization was not the reference standard or if the tube being placed was a gastrostomy or enteric tube. We defined gastrostomy tubes as tubes for percutaneous enteric access and enteric tubes as both nasal or oral gastrojejunal tubes and small bowel tubes (Schattner 1997). We excluded studies if we could not extract TP, FN, FP and TN values.

Participants

Both adults (aged greater than 16 years) and children (aged 16 years or less) who needed gastric tube placement.

Index tests

Ultrasonographic confirmation of gastric tube placement. We included all studies regardless of where the ultrasound test was performed (e.g. bedside or X-ray department) or who performed and interpreted the test (e.g. ultrasonographer or physician).

Target conditions

The target condition was appropriate gastric tube placement for any reason.

Reference standards

The reference standard was X-ray of the chest or abdomen (X-ray visualization). If misinterpretation of the X-ray was not reported in the included studies, we considered X-ray of the chest or abdomen to have 100% sensitivity and 100% specificity.

Search methods for identification of studies

Electronic searches

We systematically searched the following databases:

  • the Cochrane Library databases (Cochrane Reviews and other reviews, the Cochrane Central Register of Controlled Trials (CENTRAL) and technology assessments) (2016, issue 2) (Appendix 2)

  • MEDLINE (Ovid MEDLINE(R) In-Process & Other Non-Indexed Citations and Ovid MEDLINE(R) 1946 to 2016 February) (Appendix 3);

  • Embase (OvidSP) (1974 to 2016 February) (Appendix 4);

  • National Institute for Health Research (NIHR) PROSPERO Register (up to 2016 May) (www.crd.york.ac.uk/prospero/);

  • Aggressive Research Intelligence Facility Databases (ARIF) (up to 2016 May) (www.arif.bham.ac.uk/databases.shtml);

  • ClinicalTrials.gov (up to 2016 May) (clinicaltrials.gov/);

  • the International Clinical Trials Registry Platform (ISRCTN) registry (up to 2016 May) (www.isrctn.com/);

  • World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (up to 2016 May) (www.who.int/ictrp/en/).

We used controlled indexing terms and free-text terms as well as variations of root words. Key terms related to 'ultrasound' were combined using the set operator "AND" with key terms related to 'stomach tube'. We excluded animal studies.

We applied no language restrictions.

Searching other resources

We searched for additional references by cross-checking bibliographies of retrieved full-text papers. We searched citations and references using Scopus (www.elsevier.com/solutions/scopus). We contacted common manufacturers of ultrasound devices to seek additional or unpublished studies.

We contacted the top five manufacturing companies according to their global market share in ultrasound devices: GE Healthcare, Philips, Hitachi-Aloka, Toshiba and Siemens (Ministry of Economy, Trade and Industry 2013).

Data collection and analysis

Selection of studies

We undertook the systematic review using the methods outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011) and the Cochrane Handbook for Reviews of Diagnostic Test Accuracy (Deeks 2010). Two review authors (HT and YK or MU) independently reviewed titles and abstracts identified by the search strategy. HT and YT retrieved the full text of potentially relevant studies and independently assessed the full text against the eligibility criteria outlined in the Criteria for considering studies for this review section. We resolved differences by consensus. We provided details of both included and excluded studies in the Characteristics of included studies and Characteristics of excluded studies tables.

Data extraction and management

The two review authors (HT and YK) independently extracted data on study characteristics, participant demographics, sample size, test methods, methodological quality, sensitivity and specificity. Then, both review authors extracted data to construct a 2 × 2 contingency table including TP = correct gastric tube placement and correct visualization by ultrasound; FP = incorrect gastric tube placement but failure to visualize by ultrasound; FN = correct gastric tube placement but failure to visualize by ultrasound; TN = incorrect gastric tube placement and correct visualization by ultrasound. We resolved disagreements by consensus and with the help of the other investigator (YT).

Assessment of methodological quality

We used the QUADAS-2 tool to assess the quality of studies (Whiting 2011). We recorded the assessment on in the Characteristics of included studies table. The qualities assessed were described in detail in Appendix 5. For each item in the quality assessment form, we included a description of how the study addressed the issue and entered a judgement of 'low', 'high' or 'unclear' for an overall risk of bias for each of the four domains. In addition, we added a judgement of 'low', 'high' and 'unclear' for the overall concern of applicability to the review question for domains one, two and three. We presented an Assessment of methodological quality, which showed all judgements made for all included studies. Two review authors (HT and YK or YT) independently assessed methodological quality. We resolved disagreements by discussion between the review authors, with a further review author acting as an arbiter (YT or YK).

Statistical analysis and data synthesis

We planned to analyze data using the methods recommended in the Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy (Deeks 2010). We assumed that the data were binary (either appropriate placement, or not). Therefore, no threshold or cut-off value for positivity was required. For each study, the sensitivity, specificity, positive and negative likelihood ratios, and diagnostic odds ratio (Glas 2003) for the detection of appropriate gastric tube placement were calculated from the 2 × 2 contingency table. If these counts were unavailable, we contacted the original authors of the study.

If any misinterpretation of the X-ray was reported, we planned to construct another 2 × 2 contingency table that took the misinterpretation into account. For the table, if misplacement of the tubes was interpreted as correct placement by X-ray, we planned to ignore the X-ray result and treat the outcome as misplacement. If appropriate placement of the tubes was interpreted as misplacement by X-ray, we planned to ignore the X-ray result and treat the outcome as appropriate placement. In addition, we planned to perform sensitivity analyses.

For the meta-analysis, if quantitative data synthesis was acceptable, we planned to use a bivariate random-effects model to determine summary estimates of sensitivity and specificity with 95% confidence and prediction regions (Reitsma 2005). We planned to create a summary receiver-operator curve (sROC).

We planned to present the bivariate mean estimates of sensitivity and specificity graphically along with their corresponding 95% confidence ellipses.

All analyses were to be undertaken using Review Manager 5 (RevMan 2014), or STATA software, version 13.0 (Stata).

Investigations of heterogeneity

If sufficient studies were available, we planned to investigate the following potential sources of heterogeneity by adding variables to the meta-regression model and using the command xtmelogit in Stata (Harbord 2009; Takwoingi 2013): effects of obesity (BMI over 30 or not), effects of tube diameter (up to 14 Fr or 16 Fr and above) and area of visualization (the neck, abdomen, or both).

Sensitivity analyses

We planned to perform sensitivity analyses stratified by methodological quality as per the QUADAS-2 tool domain and planned to carry out the following sensitivity analyses to explore the robustness of the results:

  • excluding studies of non-sedated people;

  • excluding studies of intubated people;

  • excluding studies of orogastric tubes;

  • excluding studies including reported X-ray misinterpretation.

The reason for excluding non-sedated people was because the gag reflex of non-sedated people may suggest tracheal insertion of the gastric tube which may affect the diagnostic accuracy of the ultrasound. For intubated people, the tube may be difficult to visualize in the oesophagus behind the trachea, or the tracheal tube itself may block the gastric tube from entering the trachea. We anticipated that there were no differences between the diagnostic accuracy of the nasogastric and orogastric tubes and confirmed the assumption using sensitivity analysis. In addition, we anticipated that we would identify other relevant factors to include in the sensitivity analyses as we went through the process of reviewing the identified studies. We specified the criteria for the sensitivity analyses in the review rather than to predefine them at the protocol stage.

Assessment of reporting bias

We did not explore reporting bias due to a lack of suitable statistical methods (Deeks 2013).

Results

Results of the search

We identified 953 references through the electronic searches of CENTRAL (26 records), MEDLINE (330), and Embase (597). One record was identified through other sources (citation search of relevant guidelines). No additional reports were identified through NIHR Prospero Register, ARIF, ClinicalTrials.gov, ISRCTN registry or WHO ICTRP.

We excluded 147 duplicates from the electronic searches. We then excluded 791 records through reading the titles and abstracts. We retrieved 19 references for further assessment. Of the 19 references, we excluded nine for the reasons listed in the Characteristics of excluded studies table. This resulted in the inclusion of 10 references of 10 studies. Results of the search are displayed in Figure 1. We identified no additional reports through citation search of included studies or inquiry of manufacturing companies.

Figure 1.

Study flow diagram.

Methodological quality of included studies

The methodological quality of the included studies is shown in the Characteristics of included studies table, Figure 2, and Figure 3.

Figure 2.

Risk of bias and applicability concerns graph: review authors' judgements about each domain presented as percentages across included studies.

Figure 3.

Risk of bias and applicability concerns summary: review authors' judgements about each domain for each included study.

No study was assigned low risk of bias or low concern in every QUADAS-2 domain assessed. Two studies presented high risk of participant selection bias because they performed the index test after they confirmed correct position by whoosh test or auscultation (Brun 2014; Chenaitia 2012), five had unclear risk (Basile 2015; Brun 2012; Lock 2003; Nikandros 2006; Radulescu 2015), and three demonstrated low risk (Gok 2015; Kim 2012; Vigneau 2005).

One study presented high risk of index test interpretation bias because a single examiner interpreted the index test and the reference standard (Radulescu 2015), two had unclear risk (Basile 2015; Nikandros 2006), and seven demonstrated low risk (Brun 2012; Brun 2014; Chenaitia 2012; Gok 2015; Kim 2012; Lock 2003; Vigneau 2005).

We considered that one study has high risk of bias in the reference standard because the use of prespecified criteria was unclear and the same person interpreted all the results of X-ray and ultrasound (Radulescu 2015). Seven studies presented unclear risk of reference standard interpretation bias (Basile 2015; Brun 2012; Brun 2014; Chenaitia 2012; Kim 2012; Lock 2003; Nikandros 2006), and two demonstrated low risk (Gok 2015: Vigneau 2005).

One study presented high risk of bias in the 'flow and timing' domain because they reported the possibility of long time gap (greater than four hours) between the index test and the reference standard (Lock 2003), four had unclear risk (Basile 2015; Brun 2014; Nikandros 2006; Radulescu 2015), and five demonstrated low risk (Brun 2012; Chenaitia 2012; Gok 2015; Kim 2012; Vigneau 2005). In the 'flow and timing' domain, time gap presents a risk of bias because a person may feel uncomfortable when a tube remains in a misplaced position for a long time.

Findings

Characteristics of participants

Overall, we included 545 participants and 560 tube insertions for this review. The number of appropriate tube placements was 492 insertions (88%) and the number of misplacements was 68 insertions (12%). The mean age of participants in the included studies was about 50 to 60 years old (some studies did not report the range) (Table 1). None of the included studies assessed the diagnostic accuracy of ultrasound for gastric tube placement confirmation in children (aged 16 years or less).

Table 1. Baseline characteristics of included studies
  1. BMI: body mass index; EMS: emergency medical service; ICU: intensive care unit; NR: not reported; SD: standard deviation.

    a Reports from the same research group.

Study IDMale:femaleAge
(mean ± SD)
BMI
(mean ± SD)
ChildrenNon-sedatedSedatedIntubatedDiameter
of tube (Fr)
Setting
Basile 2015NRNRNRNRNRNRNRNRNR
Brun 2012 a56:2452 ± 23NR00969614 or 16Prehospital
Brun 2014 a18:1457 ± 17NR022103214 or 16Prehospital
Chenaitia 2012 a77:5355.7 ± 19.8NR0013013014-18Prehospital
Gok 201532:2448.4 ± 28.927.1 ± 6.400565610-14ICU
Kim 201228:1957.6 ± 17.2NR00472716EMS
Lock 2003NR59.2 ± 16.2NRNRNRNR5014 or 16ICU
Nikandros 20069:766.3 ± 7.1NRNR01616NRICU
Radulescu 2015NRN/RNRNRNRNRNRNRNR
Vigneau 200518:1662.2 ± 19.824.8 ± 5.8014192612ICU

Participants of five studies were all intubated (Brun 2012; Brun 2014; Chenaitia 2012; Gok 2015; Nikandros 2006). Over half of participants of two studies were intubated (78.8% of Vigneau 2005; 57.4% of Kim 2012). One study of 55 participants reported that 50 (83.3%) of 60 of tube insertions were performed in intubated participants (Lock 2003). The number of intubated participants in two studies was unclear (Basile 2015; Radulescu 2015). One study included 14 (42.4%) non-sedated participants (Vigneau 2005). One study of 55 participants reported that nine (15.0%) from 60 tube insertions were performed in non-sedated participants (Lock 2003). Participants of seven studies were either sedated or intubated (Brun 2012; Brun 2014; Chenaitia 2012; Gok 2015; Kim 2012; Lock 2003; Nikandros 2006). The number of non-sedated participants in two studies was unclear (Basile 2015; Radulescu 2015). Studies that provided demographic details of participants reported roughly equal numbers of males and females. Four studies were an intensive care unit (ICU) setting (Gok 2015; Lock 2003; Nikandros 2006; Vigneau 2005). Three studies were prehospital settings (Brun 2012; Brun 2014; Chenaitia 2012). One study was in the emergency medical service (EMS) (Kim 2012). It was considered that ultrasound was performed at the bedside in eight studies (Brun 2012; Brun 2014; Chenaitia 2012; Gok 2015; Kim 2012; Lock 2003; Nikandros 2006; Vigneau 2005). Two studies had an unknown setting (Basile 2015; Radulescu 2015). Two studies reported mean participant BMI of 27.1 (Gok 2015) and 24.8 (Vigneau 2005). Diameter of inserted tubes ranged from 10 Fr to 18 Fr.

Characteristics of the index test and the reference standard

We found several methods of ultrasound to confirm gastric tubes using ultrasound (see Summary of findings 1). Four studies reported the diagnostic accuracy of ultrasound alone (Brun 2012; Chenaitia 2012; Gok 2015; Radulescu 2015), while the others reported the diagnostic accuracy of ultrasound combined with other confirmation method (Basile 2015; Brun 2014; Kim 2012; Lock 2003; Nikandros 2006; Vigneau 2005). One study reported the diagnostic accuracy of ultrasound during tube insertion (ultrasound-guide insertion) (Gok 2015). We found three visualization methods (echo window) of ultrasound: neck approach (Gok 2015), epigastric approach (Brun 2012; Chenaitia 2012; Kim 2012; Lock 2003; Vigneau 2005), and a combination of both (Brun 2014; Radulescu 2015). Two studies used air injection during ultrasound (Basile 2015; Brun 2014). One study used saline injection (Vigneau 2005). One study used both air and saline injection (Kim 2012). One study used dextrose and air injection (Nikandros 2006). Two studies did not report the echo window (Basile 2015; Nikandros 2006). None of the studies reported any complications related to ultrasound test. One study reported the performers of ultrasound were trained nurses (Basile 2015). In other studies, the performers of the ultrasound were emergency medicine specialists (Kim 2012), experienced examiners/practitioners (Lock 2003), emergency physicians (Brun 2014), intensive care physicians following two-hour training course (Vigneau 2005), emergency physician following a one-day training course (Chenaitia 2012), staff experienced in ultrasonography (Gok 2015), prehospital services doctors trained in extended Focused Assessment with Sonography for Trauma (eFAST) examination (Brun 2012), and unclear (Nikandros 2006; Radulescu 2015). It was considered that the performers interpreted the results. All included studies used X-ray as a reference standard. No misinterpretation of X-ray among gastric tube position (revealed by other reliable clinical tests) was reported.

Diagnostic accuracy estimates of included studies

We considered the studies to differ in important ways clinically, therefore, we did not perform a meta-analysis to determine summary diagnostic accuracy estimates of ultrasound. We described diagnostic accuracy estimates of the individual studies in any settings in Summary of findings 1 and Figure 4 . We separately described the diagnostic accuracy of ultrasound for confirmation of gastric tube placement for drainage in settings where X-ray facilities were not readily available for the clinical implications (Summary of findings 2). Three studies had lower accuracy estimates than those of the other studies (Basile 2015; Kim 2012; Lock 2003) (Summary of findings 1; Figure 4). Basile and colleagues reported a sensitivity of 0.50 (95% confidence interval (CI) 0.32 to 0.68) and specificity of 0.17 (95% CI 0.02 to 0.48) (Basile 2015). Kim and colleagues reported a sensitivity of 0.86 (95% CI 0.73 to 0.95) and specificity of 0.67 (95% CI 0.09 to 0.99) (Kim 2012). Lock and colleagues reported a sensitivity of 0.74 (95% CI 0.61 to 0.85) and specificity of 1.00 (95% CI 0.16 to 1.00) (Lock 2003).

Figure 4.

Forest plot of diagnostic accuracy of ultrasound in different ways. Four studies reported the diagnostic accuracy of ultrasound (Brun 2012; Chenaitia 2012; Gok 2015; Radulescu 2015), while the others reported the diagnostic accuracy of ultrasound combined with other methods. Gok 2015 reported the diagnostic accuracy of ultrasound during tube insertion (ultrasound-guide insertion). We found three visualization methods (echo window) of ultrasound: neck (Gok 2015), epigastric (Brun 2012; Chenaitia 2012; Kim 2012; Lock 2003; Vigneau 2005), and a combination (Brun 2014; Radulescu 2015). Studies used air injection during ultrasound (Basile 2015; Brun 2014), saline injection (Vigneau 2005), both air and saline injection (Kim 2012), and dextrose and air injection (Nikandros 2006). Two studies did not report the echo window (Basile 2015; Nikandros 2006).

Summary of findings

Summary of findings 1. Accuracy of ultrasound for confirmation of gastric tube placement
Accuracy of ultrasound for confirmation of gastric tube placement
PopulationAdults in any settings (prehospital, ICU, EMS or unclear)
Index testUltrasound (any methods)
Reference standardX-ray
StudiesCross-sectional study or unclear study designa
Study IDTPbFPbFNbTNbParticipantsSensitivity
(95% CI)
Specificity
(95% CI)
MethodcEcho windowc
Basile 20151710172460.50 (0.32 to 0.68)0.17 (0.02 to 0.48)Ultrasound + air injection after insertionNR
Brun 2012 a,d80088960.91 (0.83 to 0.96)1.00 (0.63 to 1.00)Ultrasound after insertionEpigastric
Brun 2014 d27014320.96 (0.82 to 1.00)1.00 (0.40 to 1.00)Ultrasound + air injection after insertionNeck + epigastric
Chenaitia 2012 d11602121300.98 (0.94 to 1.00)1.00 (0.74 to 1.00)Ultrasound after insertionEpigastric
Gok 201552040560.93 (0.83 to 0.98)Not estimableUltrasound during insertionNeck
Kim 201238162470.86 (0.73 to 0.95)0.67 (0.09 to 0.99)Ultrasound + saline and air injectionNeck + epigastric
Lock 2003 a43015255 (60 measurements)e0.74 (0.61 to 0.85)1.00 (0.16 to 1.00)Ultrasound + air injection after insertionEpigastric
Nikandros 2006 a15010160.94 (0.70 to 1.00)Not estimableUltrasound + dextrose and air injection after insertionNR
Radulescu 2015 a28022320.93 (0.78 to 0.99)1.00 (0.16 to 1.00)Ultrasound after insertionNeck + epigastric
Vigneau 200534010350.97 (0.85 to 1.00)Not estimableUltrasound + saline injection after insertionEpigastric
CI: confidence interval; EMS: emergency medical service; ICU: intensive care unit: FN: false negative; FP: false positive; NR: not reported; TN: true negative; TP: true positive.
a Unclear study design (either case-control or cross-sectional study).
b TP: correct gastric tube placement and correct visualization by ultrasound; FP: incorrect gastric tube placement but not visualized by ultrasound; FN: correct gastric tube placement but not visualized by ultrasound; TN: incorrect gastric tube placement and correct visualization by ultrasound.
c We found several methods of ultrasound to confirm gastric tubes using ultrasound.
d Reports from the same research group.
e 60 tube insertions to 55 participants.
Summary of findings 2. Accuracy of ultrasound for confirmation of gastric tube placement for drainage in settings where X-ray facilities are not readily available
Accuracy of ultrasound for confirmation of gastric tube placement for drainage in settings where X-ray facilities are not readily available
PopulationAdults underwent gastric tube insertion for drainage in settings where X-ray facilities are not readily available (prehospital or EMS)
Index testUltrasound (any methods)
Reference standardX-ray
StudiesCross-sectional study or unclear study designa
Study IDTPbFPbFNbTNbParticipantsSensitivity
(95% CI)
Specificity
(95% CI)
MethodcEcho windowc
Brun 2012 c,d80088960.91 (0.83 to 0.96)1.00 (0.63 to 1.00)Ultrasound after insertionEpigastric
Brun 2014 d27014320.96 (0.82 to 1.00)1.00 (0.40 to 1.00)Ultrasound+ air injection after insertionNeck + epigastric
Chenaitia 2012 d11602121300.98 (0.94 to 1.00)1.00 (0.74 to 1.00)Ultrasound after insertionEpigastric
Kim 201238162470.86 (0.73 to 0.95)0.67 (0.09 to 0.99)Ultrasound + saline and air injectionNeck + epigastric
CI: confidence interval; EMS: emergency medical service; FN: false negative; FP: false positive; TN: true negative; TP: true positive.
a Unclear study design (either case-control or cross-sectional study).
b TP: correct gastric tube placement and correct visualization by ultrasound; FP: incorrect gastric tube placement but not visualized by ultrasound; FN: correct gastric tube placement but not visualized by ultrasound; TN: incorrect gastric tube placement and correct visualization by ultrasound.
c We found several methods of ultrasound to confirm gastric tubes using ultrasound.
d Reports from the same research group.

Discussion

Summary of main results

This review assessed the diagnostic accuracy of ultrasound for gastric tube placement confirmation. Most results showed high point estimates for correct tube detection (sensitivity) (Figure 4). However, there was a variety of point estimates for misplacement detection (specificity) and their CIs were wide due to the small sample of misplacement (Figure 4). We found considerable clinical heterogeneity among the included studies in terms of the difference of echo window, combination of ultrasound with other methods (e.g. saline flush visualization by ultrasound) and ultrasound during insertion of the tube. Thus, we could not obtain summary diagnostic accuracy (Summary of findings 1; Figure 4).

Among studies that evaluated the diagnostic accuracy of ultrasound on its own, we found three different visualization methods reported: neck approach (Gok 2015), epigastric approach (Brun 2012; Chenaitia 2012; Lock 2003), and a combination of both neck and epigastric approaches (Brun 2014; Radulescu 2015).

The authors of the studies reported mostly high sensitivity; however, the CIs of specificity were too wide to apply to clinical practice. We hypothesized that ultrasound could be an alternative to X-ray. However, studies included only a small number of participants for the purpose of determining tube misplacement (specificity) (Figure 4). In addition, there were limited data on the accuracy of tube placement in children.

Strengths and weaknesses of the review

Strengths and limitations of included studies

We contacted the authors of included studies and some authors provided us with unpublished details of studies for the review. The authors who provided additional information are presented in Acknowledgements. The weakness of our review is the inclusion of three studies from the same research group (see Table 1; Summary of findings 1) (Brun 2012; Brun 2014; Chenaitia 2012). In addition, we calculated diagnostic accuracy based on the number of tube insertions, rather than the number of participants, using 60 tube insertions among 55 participants.

Strengths and limitations of the search strategy

A strength of this review is that we placed no restrictions on the language of publication and we conducted a comprehensive search using both controlled term and free words (de Vet 2008). We avoided using search filters because of their limited sensitivity (Beynon 2013). We undertook additional searches to find related articles by inquiring major companies of ultrasound devises to obtain unpublished data. We also performed a citation search of included studies, major guidelines (ENA 2015; ESPEN Guidelines 2009; JSPEN Guideline 2013; SCCM and ASPEN Guidelines 2016), and previous related reviews (Irving 2014; Milsom 2015), regarding gastric tube placement or parenteral feeding. Therefore, we minimized the risk of missing relevant studies. Little is known about the mechanisms of publication bias for diagnostic accuracy studies and so it is not possible to estimate the impact of unpublished studies on our findings. Nevertheless, the studies included in this systematic review are likely to be the majority of studies that provided evidence on this topic.

We did not employ Web of Science (apps.webofknowledge.com/) for our citation search strategy, and acknowledge that we may have missed some studies despite the otherwise comprehensive search.

Quality assessment

Our review had several weaknesses in terms of the methodological quality of the included studies (Figure 2; Figure 3). Two studies presented high risk of participant selection bias because they performed the index test after they confirmed correct position by whoosh test or auscultation (Brun 2014; Chenaitia 2012); however, if the assumed prior test were whoosh test or auscultation, the risk of participant selection bias would be low. One study presented high risk of index test interpretation bias because a single examiner interpreted the index test and the reference standard (Radulescu 2015). We considered that one study had a high risk of bias in the reference standard because the use of prespecified criteria was unclear and the same person interpreted all the results of X-ray and ultrasound (Radulescu 2015).

Limitations in the review analyses

We could not synthesize the estimates of diagnostic accuracy (e.g. summary sensitivity, sROC curve) because of the heterogeneity of the included studies. This might make our findings relatively difficult to apply to clinical practice.

Within- and between-study comparisons

One study had extremely poor diagnostic performance with a sensitivity of 0.50 (95% CI 0.32 to 0.68) and specificity of 0.17 (95% CI 0.02 to 0.48) than those of the other studies (Basile 2015) (Summary of findings 1). The performers of ultrasound were trained personnel (nurses); however, they presented poor diagnostic accuracy. The reason was unclear; we inquired about the detailed information from the authors but we could not get sufficient information for this study.

Comparison with previous research

Milsom and colleagues systematically reviewed the methods to confirm the tube location regardless of gastric or enteric tubes and identified one study of gastric tubes. Their electronic search strategies were restricted publications to English language and they did not use controlled terms (Milsom 2015). In addition, they used a date filter for diagnostic accuracy studies restricting the search to 1985 to 2012. We could have identified additional studies by broadening the search methods but could not identify any relevant studies in children. Similarly, Irving and colleagues systematically reviewed ultrasound confirmation of gastric tube placement among children but found no studies of interest (Irving 2014).

Applicability of findings to the review question

Population and setting

Most included participants were unconscious, which may reduce the sensitivity to the tube being misplaced in the trachea. Misplaced tubes usually cause discomfort and conscious people may complain about it. Most included studies were in a prehospital setting (unconscious due to severe trauma), ICU setting (mechanical ventilated) or EMS setting. This is consistent with the population we expected to find; however, diagnostic accuracy may change according to the clinical setting, for example, clinicians may be able to perform the test more carefully in convalescent wards.

We considered that the mixture of gastric and transpyloric tube insertions had high concern regarding to applicability to the review question in 'patient selection domain' (Vigneau 2005). In addition, among include studies of 560 tube confirmations, misinterpretation of X-ray was not reported. In reality, misinterpretation of X-rays occurs especially when non-radiologists read the X-rays (ECRI and ISMP 2006; Lamont 2011).

Index test

We found various ultrasound methods regarding this review question. Brun 2014 used two-point ultrasound; they first observed the tube in the oesophagus through the neck and then confirmed the depth of the tube through the epigastric area. In contrast, Chenaitia 2012 only observed the tube through the epigastric area. Gok 2015 reported the diagnostic accuracy of real-time ultrasound during gastric tube insertion. Kim 2012 reported the diagnostic accuracy of ultrasound combined with saline and air insertion and Lock 2003 reported the accuracy of ultrasound combined with air injection. In addition, some studies did not report the method details ( Basile 2015; Nikandros 2006). Such heterogeneity of the index test might be a concern for the applicability of the findings to clinical practice.

We considered that the diagnostic accuracy of real-time ultrasound during gastric tube insertion had high concern regarding to applicability to the review question (Gok 2015).

Reference standard

Most included studies used chest or abdominal X-rays. Some reported just "X-ray". No study reported misinterpretation or unclear results of X-ray; however, in clinical settings, misinterpretation of X-ray sometimes possible. Taking into account the misinterpretations, misplacement of tubes (especially in unconscious participants) might not be detected by X-ray. These differences of reference standard may affect the diagnostic accuracy of ultrasound in this review.

Authors' conclusions

Implications for practice

How is the test positioned in the clinical pathway?

For possible implication for practice, the gastric tube is first inserted into the patient via the nose or mouth, down the oesophagus and into the stomach. Next, tube placement is confirmed by ultrasound combined with other tests (whoosh test, auscultation, inflation of air, etc.) followed by X-ray visualization of the tube (e.g. chest X-ray). If a tube is misplaced and detected by X-ray visualization, the tubes would be reinserted and a second X-ray would confirm the position. If ultrasound detects obvious misplacement of the tube with this sensitivity, they would reinsert the tubes and confirm it by X-ray.

How does the index test perform in relation to its intended role (add, replace, triage)?

Available evidence suggests that ultrasound could play an important role in detecting gastric tube position combined with other confirmation methods (e.g. saline flush visualization by ultrasound). However, when we expect ultrasound to detect misplaced tubes, it is suggested that we could not use it alone as an alternative to X-rays for the feeding tube (Summary of findings 1). However, ultrasound could play an important role as one of the confirmation methods for gastric drainage tubes, especially in settings where X-ray facilities are not readily available (Summary of findings 2).

Implications for research

Additional research needed on aspects of tests beyond their accuracy

Available evidence suggests that ultrasound would mostly detect misplacement and possibly reduce repeated X-ray scan. Confirmation by X-ray scan can be difficult for people with tube placement because they have to change their body position to have a hard film plate placed on their back, or stand up for scanning while dealing with uncomfortable tubes hanging from their nose or mouth. Further research is needed to investigate whether it would reduce repeated X-ray confirmations, patient's discomfort from the procedure and severe complications of tube feeding (e.g. feeding via a tube misplaced in the trachea resulting in severe pneumonia, pneumothorax, empyema or pulmonary haemorrhage). In addition, investigation into cost to healthcare is needed to determine if ultrasound could reduce expenditure on repeated X-rays. We consider research comparing X-ray and ultrasound considering diagnostic accuracy, patient outcome and cost is needed.

Further studies of test accuracy that need to be undertaken

Larger studies are needed to investigate whether ultrasound could replace X-rays for confirming gastric tube placement, as well as decrease severe complications, such as aspiration pneumonia, from a misplaced tube. Studies are also needed in children. We consider that investigation of the potential factors modifying the diagnostic accuracy of ultrasound is needed if data are obtained and acceptable for integration.

Acknowledgements

We would like to thank the editorial team of the Cochrane Upper Gastrointestinal and Pancreatic Diseases Group for their excellent advice and support. We wished to thank Emma Barber of the National Center for Child Health and Development, Tokyo, Japan, for her editorial support of the protocol and Yuhong (Cathy) Yuan, Trials Search Co-ordinator of the Cochrane Upper Gastrointestinal and Pancreatic Diseases Review Group for designing our search strategy. The methods section of this manuscript was based on the Cochrane protocol, Holland 2013, as a template. We would like to thank Dr Laurie Dontigny-Duplain of the Department of General Surgery, Université Laval, Quebec City, Canada, for translation, data extraction and QUADAS-2 assessment of the French article through the Cochrane TaskExchange (taskexchange.cochrane.org). We are grateful to Dr Mbah Okwen Patrick of the Centre for the Development of Best Practices in Health (CDBPH) Yaoundé Central Hospital Yaoundé Cameroon and Alexis Turgeon MD MSc (Épid) FRCPC of the Département d'Anesthésiologie et de Soins Intensifs, Division de Soins Intensifs Adultes Faculté de Médecine, Université Laval, Quebec City, Canada, for data extraction of the French article (for cross-checking) through the Cochrane TaskExchange. We are also grateful to Dr Eric Maury and Dr Funda Gok for kindly providing additional information about their studies. We wish to thank Mrs Katharina Kunzweiler of Cochrane Germany for translation and data extraction of the German article. We would like to thank Dr Matthias Rinderknecht for data extraction (for cross-checking) of the German article through the Cochrane TaskExchange.

Data

Presented below are all the data for all of the tests entered into the review.

Table Tests. Data tables by test
TestNo. of studiesNo. of participants
1 Ultrasound10550
Test 1.

Ultrasound.

Appendices

Appendix 1. Additional characteristics of included studies

Study IDBasile 2015
Report ID2-26
Review author nameHT and YK
AuthorsBasile V, Cresci A, Brondi D, Solinas D, Cei M, Mumoli N
Contact addressDepartment of Internal Medicine, Ospedale Civile Livorno, Livorno, Italy
Country of the studyItaly
Language of publicationEnglish
Participants
Age (mean, median, range)Unclear
Sex (male numbers/%)Unclear
BMIUnclear
Study characteristics
Single or multicentre?Single
Inclusion criteria of participantsConsecutive
Total number of participants46
Total number of adultsUnclear
Total number of childrenUnclear
Total number of non-sedated participantsUnclear
Total number of intubated participantsUnclear
Types of tubes (nasogastric or orogastric)Nasogastric
Diameter of gastric tubeUnclear
Reference standard (chest or abdominal X-ray visualization)Chest X-ray
Detail reference standard process (if available)Blind
Index test (where was the echo window of the tube?)Unclear
Index test (where the ultrasound test was performed)Unclear
Index test (who performed the test)Nurses
Time gap between index test and reference standardUnclear
Study outcome (number of people)
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)17
Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)10
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)17
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)2
Number of X-ray misinterpretationNot reported
Additional information-
Conflict of interestUnclear
Study IDBrun 2012
Report ID2-21
Review author nameDr Laurie Dontigny-Duplain, Dr Mbah Okwen Patrick (for data extraction of the French article)
AuthorsBrun PM, Chenaitia H, Bessereau J, Leyral J, Barberis C, Pradel-Thierry AL, Stephan J, Benner P, Querellou E, Topin F
Contact addressE-mail: brunpierremarie@voila.fr
Country of the studyFrance
Language of publicationFrance
Participants
Age (mean, median, range)Mean: 52 years; median: 53.5 years; SD: 23 years
Sex (male numbers/%)56/58.3%
BMINot available
Study characteristics
Single or multicentre?Single
Inclusion criteria of participantsPeople intubated by prehospital services that required an NG tube
Total number of participants96
Total number of adults96
Total number of children0
Total number of non-sedated participants0
Total number of intubated participants96
Types of tubes (nasogastric or orogastric)NG
Diameter of gastric tube14 or 16 Fr
Reference standard (chest or abdominal X-ray visualization)Chest X-ray on arrival at hospital
Detail reference standard process (if available)-
Index test (where was the echo window of the tube?)Transverse left subcostal
Index test (where the ultrasound test was performed)Prehospital setting
Index test (who performed the test)Prehospital services doctor trained in eFAST examination
Time gap between index test and reference standardNot available
Study outcome (number of people)
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)80
Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)0
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)8
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)8
Number of X-ray misinterpretation0
Additional information-
Conflict of interestNone
Study IDBrun 2014
Report ID2-01
Review author nameHT and YK
AuthorsBrun PM, Chenaitia H, Lablanche C, Pradel AL, Deniel C, Bessereau J, Melaine R
Contact addressDepartment of Emergency Medicine and Intensive Care, Desgenettes Military Hospital, Lyon, France
Country of the studyFrance
Language of publicationEnglish
Participants
Age (mean, median, range)mean: 57 years, median: 59 years, range unclear
Sex (male numbers/%)18/56.3%
BMIUnclear
Study characteristics
Single or multicentre?Single
Inclusion criteria of participants

Aged ≥ 18 years receiving prehospital care and requiring GT insertion.

Exclusion criteria: aged < 18 years, pregnant, contraindication at GT insertion, interhospital transfers and absence of X-ray control.

Total number of participants32
Total number of adults32
Total number of children0
Total number of non-sedated participants0
Total number of intubated participants32
Types of tubes (nasogastric or orogastric)Either nasogastric or orogastric tubes used
Diameter of gastric tube14 Fr: 12, 16 Fr: 20
Reference standard (chest or abdominal X-ray visualization)X-ray
Detail reference standard process (if available)Protocol also required final confirmation of GT placement by X-ray on arrival at hospital, X-ray was the test method reference to confirm correct GT placement.
Index test (where was the echo window of the tube?)Portable ultrasound system (Titan, Sonosite, Bothell, WA) with a microconvex probe (2-A MHz). Technique standardized; probe placed transversely on anterior neck just superior to suprasternal notch in midline at level of thyroid gland and focused on visible part of the oesophagus (Figure 1 of publication), with longitudinal and transversal viewing, then probe placed in subxiphoid area and oriented towards left upper abdominal quadrant to visualize stomach (Figure 2 of publication), with transverse and longitudinal viewing. The antrum was imaged in transversal plane in epigastric area using left lobe of liver as an internal landmark, angling the transducer towards left subcostal area to image gastric body. Ultrasound examination was considered as positive when GT was visualized, appearing as an hyperechogenic circle posterior to the thyroid tissue adjacent to the trachea (Figure 1 of publication), and as a hyperechogenic line in stomach (Figure 2 of publication). When GT was seen in oesophagus and not in stomach, 50 mL of air were injected through the GT, if ultrasonography showed dynamic fogging in the stomach, GT was considered in stomach.
Index test (where the ultrasound test was performed)Prehospital setting
Index test (who performed the test)Emergency physician
Time gap between index test and reference standardUnclear
Study outcome (number of people)
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)

Echo + fogging 28

Echo only 27

Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)

Echo + fogging 0

Echo only 0

Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)

Echo + fogging 0

Echo only 1

Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)

Echo + fogging 4

Echo only 4

Number of X-ray misinterpretation0
Additional information-
Conflict of interestUnclear
Study IDChenaitia 2012
Report ID2-05,11
Review author nameHT and YK
AuthorsChenaitia H, Brun PM, Querellou E, Leyral J, Bessereaud J, Aimée C, Bouazize R, Georgesf A, Louisf F; WINFOCUS (World Interactive Network Focused On Critical Ultrasound) Group France
Contact address

Service de Médecine d'Urgence et de Radiologie, Centre Hospitalier General de Clavary, Grasse, France

Tel.: +33 4 91499191; fax: +33 4 91386943

Country of the studyFrance
Language of publicationEnglish
Participants
Age (mean, median, range)Mean ± SD: 55.7 ± 19.8 years
Sex (male numbers/%)77/59%
BMIUnclear
Study characteristics
Single or multicentre?Multicentre
Inclusion criteria of participants

Inclusion criteria: aged ≥ 18 years in prehospital settings and requiring GT insertion

Exclusion criteria: aged < 18 years, pregnant, interhospital transfers and absence of X-ray control

Total number of participants130
Total number of adults130
Total number of children0
Total number of non-sedated participants0
Total number of intubated participants130
Types of tubes (nasogastric or orogastric)Both
Diameter of gastric tube7 × 18-Fr GTs were inserted and all were visible, 94 × 16-Fr GTs were inserted and 98% were visible, and 29 × 14-Fr GTs were inserted and 81% were visible.
Reference standard (chest or abdominal X-ray visualization)X-ray
Detail reference standard process (if available)X-ray on arrival at hospital
Index test (where was the echo window of the tube?)Subxiphoid area
Index test (where the ultrasound test was performed)Prehospital
Index test (who performed the test)2 emergency physicians who performed ultrasound examination were experienced and certified in emergency ultrasound, had 1-day of training dedicated to study the specificities of this type of ultrasound examination.
Time gap between index test and reference standardUnclear
Study outcome (number of people)
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)116
Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)0
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)2
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)12
Number of X-ray misinterpretation0
Additional information-
Conflict of interestNone
Study IDGok 2015
Report ID2-06,07,09
Review author nameHT and YK
AuthorsGok F, Kilicaslan A, Yosunkaya A
Contact address

Necmettin Erbakan University, Meram Faculty of Medicine, Department of Anesthesiology and
Reanimation, Intensive Care Unit, Konya 42080, Turkey

Email: fundagok@gmail.com

Country of the studyTurkey
Language of publicationEnglish
Participants
Age (mean, median, range)Mean ± SD: 48.4 ± 28.9 years
Sex (male numbers/%)32/57.1%
BMIMean ± SD: 27.1 ± 6.4
Study characteristics
Single or multicentre?Single
Inclusion criteria of participants

56 mechanically ventilated participants monitored in the ICU between February and July 2014 who received ultrasound-guided NG tube placement were included in the study.

Exclusion criteria: histories of neck surgery (e.g. tracheotomy), anatomic deformity, nasal fracture or severe coagulopathy.

Total number of participants56
Total number of adults56 (author's reply)
Total number of children0 (author's reply)
Total number of non-sedated participants0
Total number of intubated participants56
Types of tubes (nasogastric or orogastric)Nasogastric, guidewire
Diameter of gastric tube10-14 Fr
Reference standard (chest or abdominal X-ray visualization)

After ultrasound-guided tube insertion, gastric placement of the NG tube tip confirmed with abdominal X-ray (author's reply).

All reference standard results interpreted by a single person (author's reply).

Used prespecified criteria of the correct position; i.e. NG tube tip below the diaphragm; should follow straight course down midline of chest to a point below diaphragm (author's reply).

Detail reference standard process (if available)-
Index test (where was the echo window of the tube?)Transversely placed over the suprasternal notch. Images obtained of isthmus and 2 lobes of thyroid gland. By shifting the
probe to the left, the concentric layers of the oesophagus under thyroid lobe left to trachea were attempted to be viewed.
Index test (where the ultrasound test was performed)ICU
Index test (who performed the test)Ultrasound examination performed by the same operator, experienced in ultrasonography.
Time gap between index test and reference standard10 minutes to 1 hour (author's reply)
Study outcome (number of people)
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)52
Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)0
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)4
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)0
Number of X-ray misinterpretation0
Additional information4 unclear result of ultrasound
Conflict of interestNone reported
Study IDKim 2012
Report ID2-12,13,14
Review author nameHT and YK
AuthorsKim HM, So BH, Jeong WJ, Choi SM, Park KN
Contact address

Department of Emergency Medicine, College of Medicine, The Catholic
University of Korea, St. Mary's Hospital, Seoul, South Korea.

Email: emsky@catholic.ac.kr

Country of the studyKorea
Language of publicationEnglish
Participants
Age (mean, median, range)Mean ± SD: 57.6 ± 17.2 years
Sex (male numbers/%)28/59.6%
BMIUnclear
Study characteristics
Single or multicentre?Single
Inclusion criteria of participants

Unclear criteria

Prospective study performed between May and September 2011 in a local emergency centre. Included participants with low consciousness in whom correct placement of NG tube was ultimately verified by chest X-ray.

Aged > 18 years, undergoing NG tube insertions for reasons including drug overdose, suspicion of gastric bleeding, endotracheal intubation and others.

17 patients with normal levels of consciousness were excluded.

10 participants did not undergo X-ray examination.

Total number of participants47
Total number of adults47
Total number of children0
Total number of non-sedated participants0
Total number of intubated participants27
Types of tubes (nasogastric or orogastric)Nasogastric
Diameter of gastric tube16 Fr
Reference standard (chest or abdominal X-ray visualization)Chest X-ray
Detail reference standard process (if available)

Final confirmation of gastric placement of tube by chest X-ray, i.e. test method reference standard to confirm correct NG tube placement.

Chest X-rays interpreted by emergency medicine specialist who did not perform ultrasound examinations.

Index test (where was the echo window of the tube?)In oesophagogastric junction, NG tube directly visualized with longitudinal and angled scans of the epigastrium. Visualization of NG tube in separate scans of fundus and antrum of stomach.
Index test (where the ultrasound test was performed)EMS
Index test (who performed the test)Ultrasound examinations conducted by 2 emergency medicine specialists.
Time gap between index test and reference standardUnclear
Study outcome (number of people)-
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)38
Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)1
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)6
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)2
Number of X-ray misinterpretation0
Additional information-
Conflict of interestNone reported
Study IDLock 2003
Report ID2-08
Review author nameMs Katharina Kunzweiler, Dr Matthias Rinderknecht (translation and data extraction of the German article)
AuthorsLock G, Reng CM, Köllinger M, Rogler G, Schölmerich J, Schlottmann K
Contact address

Medizinische Klinik Albertinenkrankenhaus Süntelstr. 11a, 22457 Hamburg, Germany

Tel.: 040/5588-2262, Email: guntram.lock@albertinen.de

Country of the studyGermany
Language of publicationGermany
Participants
Age (mean, median, range)Mean ± SD: 59.2 ± 16.2 years; range: 16-84 years
Sex (male numbers/%)Not reported
BMINot reported
Study characteristics
Single or multicentre?Single (internal ICU of a university hospital)
Inclusion criteria of participants

Inclusion criteria: people in ICU, endotracheal intubation and ventilation or independent breathing

Exclusion criteria: percutaneous endoscopic gastrostomy

How were participants' coughs managed: not reported.

How were auscultation findings dealt with: auscultation in the epigastrium after insufflation of 50 mL of air by a bladder syringe; localization counted as correct if sound of incoming air in epigastrium could clearly be auscultated.

Prior testing: not reported.

Presentation: in 50/60 procedures, participants were endotracheally intubated and ventilated; in 10/60 procedures, participants were breathing spontaneously, none had a tracheostomy.

In 51/60 procedures, participants were unable to co-operate; in 8/60 procedures, participants were partly able to co-operate and in 1 procedure fully able to co-operate. In 49/60 procedures, tube placed for feeding, in 11/60 procedures, for drainage.

Total number of participants55 participants with in 60 gastric tube insertions
Total number of adultsNot reported
Total number of childrenNot reported
Total number of non-sedated participants9 procedures
Total number of intubated participantsParticipants were intubated in 50 gastric tube insertions
Types of tubes (nasogastric or orogastric)Nasogastric (in exceptional cases orogastric)
Diameter of gastric tube

58 times soft silicon tube, diameter 14.6 Charrière

2 times drainage tube, diameter not reported

Reference standard (chest or abdominal X-ray visualization)

Reference standard: X-ray

X-ray of lower thorax or upper abdomen. Incorrect localization of tube defined as localization of tube in oesophagus or lungs. X-ray usually carried out routinely on next morning after procedure or because of another medical indication. Period between placement of gastric tube and radiological control was within 24 hours.

Detail reference standard process (if available)Not reported
Index test (where was the echo window of the tube?)In ultrasound, correct placement of tip of tube in stomach was ascertained by detecting a 50 mL air jet applied with a syringe via the gastric tube.
Index test (where the ultrasound test was performed)ICU
Index test (who performed the test)Ultrasound performed by 10 experienced examiners/practitioners.
Time gap between index test and reference standardAfter auscultation in the epigastrium, pH measurement of aspirate or ultrasound, examiner decided, if correct placement of gastric tube was documented by these methods. Period between placement of gastric tube and radiological control always within 24 hours.
Study outcome (number of people)
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)43
Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)0
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)15
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)2
Number of X-ray misinterpretation-
Additional information-
Conflict of interestNot reported
Study IDNikandros 2006
Report ID3-01
Review author nameHT and YK
AuthorsNikandros M, Skampas N, Theodorakopoulou M, Ioannidou S, Theotokas M, Armaganidis A
Contact addressNot reported (we contacted the journal Critical Care and Prof Armaganidis Apostles)
Country of the studyGreece
Language of publicationEnglish
Participants
Age (mean, median, range)Mean ± SD: 66.3 ± 7.1 years
Sex (male numbers/%)9/56%
BMIUnclear
Study characteristics
Single or multicentre?Single
Inclusion criteria of participantsUnclear
Total number of participants16
Total number of adultsUnclear
Total number of childrenUnclear
Total number of non-sedated participants0
Total number of intubated participants16
Types of tubes (nasogastric or orogastric)NG tube
Diameter of gastric tubeUnclear
Reference standard (chest or abdominal X-ray visualization)X-ray
Detail reference standard process (if available)-
Index test (where was the echo window of the tube?)Unclear
Index test (where the ultrasound test was performed)ICU
Index test (who performed the test)Unclear
Time gap between index test and reference standardUnclear
Study outcome (number of people)
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)15
Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)0
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)1
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)0
Number of X-ray misinterpretation0
Additional information-
Conflict of interestUnclear
Study IDRadulescu 2015
Report ID2-27
Review author nameHT and YK
AuthorsRadulescu V, Ahmad S
Contact addressStony Brook University Hospital, St James, NY
Country of the studyUS
Language of publicationEnglish
Participants
Age (mean, median, range)Unclear
Sex (male numbers/%)Unclear
BMIUnclear
Study characteristics
Single or multicentre?Unclear
Inclusion criteria of participantsUnclear
Total number of participants32
Total number of adultsUnclear
Total number of childrenUnclear
Total number of non-sedated participantsUnclear
Total number of intubated participantsUnclear
Types of tubes (nasogastric or orogastric)Gastric tube
Diameter of gastric tubeUnclear
Reference standard (chest or abdominal X-ray visualization)Chest X-ray
Detail reference standard process (if available)Unclear
Index test (where was the echo window of the tube?)Anterolateral neck scanned in high frequency to visualize the gastric tube's characteristic echogenic surface with posterior anechoic shadow in oesophagus. Then, right diaphragm location identified by low-frequency imaging.
Index test (where the ultrasound test was performed)Unclear
Index test (who performed the test)Unclear
Time gap between index test and reference standardUnclear
Study outcome (number of people)
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)28
Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)0
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)2
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)2
Number of X-ray misinterpretation0
Additional information-
Conflict of interestUnclear
Study IDVigneau 2004
Report ID2-3,28
Review author nameHT and YK
AuthorsVigneau C, Baudel JL, Guidet B, Offenstadt G, Maury E
Contact addressService de Reanimation Medicale, Hôpital Saint -Antoine, Assistance Publique-Hôpitaux de Paris, 184 rue du Faubourg Saint-Antoine, 75571 Paris Cedex 12, France
Country of the studyFrance
Language of publicationEnglish
Participants
Age (mean, median, range)Mean ± SD: 62.2 ± 19.8 years
Sex (male numbers/%)18/54.5%
BMIMean 24.8 ± 5.8
Study characteristics
Single or multicentre?Single
Inclusion criteria of participantsAll consecutive participants during a 2-month period who received a weighted NG tube (12CH, Cair, France) for enteral feeding between 8:30 a.m. and 8:00 p.m.
Total number of participants33
Total number of adultsUnclear
Total number of childrenUnclear
Total number of non-sedated participants14
Total number of intubated participants26
Types of tubes (nasogastric or orogastric)NG (weighted-tip NG tube)
Diameter of gastric tube12 Fr
Reference standard (chest or abdominal X-ray visualization)X-ray
Detail reference standard process (if available)As soon as tube was correctly inserted, radiology department performed confirmatory X-ray. Times required to obtain the X-ray and ultrasound results were recorded.
Index test (where was the echo window of the tube?)Epigastric area
Index test (where the ultrasound test was performed)ICU
Index test (who performed the test)Principal investigator (CV) was an intensive care physician who had not graduated in sonography, and who therefore followed a specific 2-hour training course with a radiologist.
Time gap between index test and reference standardNot recorded
Study outcome (number of people) 
Correct gastric tube placement and correct visualization by ultrasound (i.e. true-positive test)

Echo only 26

Echo + saline injection 8

Incorrect gastric tube placement but failure to visualize by ultrasound (i.e. false-positive test)0
Correct gastric tube placement but failure to visualize by ultrasound (i.e. false-negative test)1 unclear result of ultrasound, but successful insertion (author's response)
Incorrect gastric tube placement and correct visualization by ultrasound (i.e. true-negative test)0
Number of X-ray misinterpretation0
Additional information1 unclear result of ultrasound (gas interposition)
Conflict of interestNone (author's response)

BMI: body mass index; eFAST: extended Focused Assessment with Sonography for Trauma; GT: gastric tube; ICU: intensive care unit; NG: nasogastric; SD: standard deviation.

Appendix 2. CENTRAL search strategy

  1. MeSH descriptor: [Ultrasonography] explode all trees

  2. (ultrason* or ultrasound* or echotomograph* or echo tomograph* or echograph* or sonograph* or ultra sound or acoustic):ti,ab,kw (Word variations have been searched)

  3. #1 or #2

  4. MeSH descriptor: [Intubation, Gastrointestinal] explode all trees

  5. ((stomach or gastric or gastro* or nasogastric or feeding or fine bore or Ryles) near/3 (tube* or intubat*)):ti,ab,kw (Word variations have been searched)

  6. #4 or #5

  7. #3 and #6

Appendix 3. MEDLINE search strategy

  1. exp Ultrasonography/

  2. (ultrason* or ultrasound* or echotomograph* or echo tomograph* or echograph* or sonograph* or ultra sound or acoustic).ti,ab,kw.

  3. 1 or 2

  4. exp Intubation, Gastrointestinal/

  5. ((stomach or gastric or gastro* or nasogastric or feeding or fine bore or Ryles) adj3 (tube* or intubat*)).ti,ab,kw.

  6. 4 or 5

  7. 3 and 6

  8. animals/ not human/s

  9. 7 not 8

Appendix 4. Embase search strategy

  1. exp ultrasound/

  2. (ultrason* or ultrasound* or echotomograph* or echo tomograph* or echograph* or sonograph* or ultra sound or acoustic).ti,ab,kw.

  3. 1 or 2

  4. exp stomach tube/

  5. exp nasogastric tube/

  6. ((stomach or gastric or gastro* or nasogastric or feeding or fine bore or Ryles) adj3 (tube* or intubat*)).ti,ab,kw.

  7. 4 or 5 or 6

  8. 3 and 7

  9. animal/not human/

  10. 8 not 9

Appendix 5. Study quality assessment details

Domain 1: participant selection

Risk of bias: could the selection of participants have introduced bias?

Signalling question 1: was a consecutive or random sample of participants enrolled?

Signalling question 2: was a case-control design avoided?

Signalling question 3: did the study avoid reinsertion of the tube when participants coughed too much?

Signalling question 4: did the study avoid reinsertion of the tube when participants did not make a bubbling sound?

Signalling question 5 and 6: did the study avoid inappropriate exclusions?

Coughing or the absence of bubbling sounds indicates misplacement of tubes into the airway. If participants experience these tests and receive reinsertion based on the results, referral bias is suspected. In addition, anatomical variation of the neck structure (e.g. larynx, pharynx) may make insertion of gastric tubes more difficult (Der Kureghian 2011; Holland 2013). This point may also affect the difficulty of visualizing the tubes by ultrasound. We classified as 'yes' those studies that excluded people who had difficulties with nasogastric tube insertion or visualization, 'no' for those studies where people did not experience such difficulties and 'unclear' where this information was not clear.

Applicability: were there concerns that the included participants and the setting did not match the review question?

The inclusion criteria for this review specified studies in which the participants were considered to require gastric tube insertion (not including transpyloric tube) for any reason. Therefore, we anticipated that all the studies in the review were judged as 'low' concern.

Domain 2: index test

Risk of bias: could the conduct or interpretation of the index test have introduced bias?

Signalling question 1: were the index test results interpreted without knowledge of the results of the reference standard?

We classified the study as 'yes' if ultrasound test results were interpreted without knowledge of the reference standard or if ultrasound test results were interpreted before the X-ray test, 'no' if the ultrasound tests were interpreted with knowledge of the reference standard results and 'unclear' if this information was not clear.

Applicability: were there concerns that the index test, its conduct or interpretation differed from the review question?

Confirmation of gastric tube placement by ultrasound was an inclusion criterion for this review, so we anticipated that all studies were classified as 'low' concern.

Domain 3: reference standard

Risk of bias: could the reference standard, its conduct or its interpretation have introduced bias?

Signalling question 1: is the reference standard likely to correctly classify the target condition?

Signalling question 2: were the reference standard results interpreted without knowledge of the results of the index test?

Signalling question 3: were the criteria of reference standard for target condition prespecified?

We classified the studies as 'yes' if the criteria for appropriate gastric tube placement were checked by X-ray visualization, 'no' if the criteria for verification of placement were by any other methods and 'unclear' if this information was not clear. We classified the study as 'yes' if X-ray visualization results were interpreted without knowledge of the index test, 'no' if the X-ray visualization was interpreted with knowledge of the index test results and 'unclear' if this information was not clear. We classified the study as 'yes' if the criteria of reference standard for target condition were prespecified, 'no' if the criteria of reference standard for target condition were not prespecified and 'unclear' if this information was not clear.

Applicability: were there concerns that the target condition as defined by the reference standard did not match the review question?

The target condition is the appropriate placement of a gastric tube in the stomach via the nose or mouth, which may be improved by the use of prespecified diagnostic criteria for chest X-ray interpretation (Lamont 2011). We evaluated those studies that used clear diagnostic criteria for X-ray visualization interpretation as 'low' concern, those that did not use any criteria or where the interpretation was based on an individual clinician's interpretation as 'high' concern and 'unclear' concern if this information was not clear.

Domain 4: flow and timing

Risk of bias: could the participant flow have introduced bias?

Signalling question 1: did all participants receive the same reference standard?

Signalling question 2: was there an appropriate interval between the index test and reference standard?

Signalling question 3: were all participants included in the analysis?

We classified the study as 'yes' if all participants had the same reference standard, 'no' if the reference standard was different from chest or abdominal X-ray and 'unclear' if this information was not clear. If a gastric tube was correctly inserted and initial gastric tube placement was confirmed, continual assessment is still required because some routine activities (e.g. vomiting, coughing, retching) may cause tube displacement (Simons 2012). Therefore, any delay in testing may influence results. However, we set an arbitrary time delay between tests in line with the AACCN 2009, which recommends tube location to be checked at four-hourly intervals (Simons 2012). We classified the study as 'yes' if the delay was less than four hours, 'no' if the delay was four hours or more and 'unclear' if the information was not clear.

Uninterpretable results may be present (e.g. unclear chest X-ray or ultrasound). Additionally, withdrawals from the study may be present. We classified the study as 'yes' if uninterpretable results were reported and the study had no withdrawals or the withdrawals were unlikely to affect the results, 'no' if uninterpretable results were not reported or there were withdrawals that were likely to affect the results, or both, and 'unclear' if this information was not clear.

Contributions of authors

HT drafted the protocol and review with contributions from YK and Emma Barber (from the National Center for Child Health and Development).

HT and YK devised the study selection criteria.

HT, YK, YT, MA and Yuhong (Cathy) Yuan (Trials Search Co-ordinator) undertook the search strategy.

HT, YK and YT developed the study design and research question.

HT, YK and YN developed the statistical analysis/synthesis of data plan.

HT and Yuhong (Cathy) Yuan ran the search strategy.

HT, YK and MA screened the search results.

HT and YK extracted the data and assessed the methodological quality.

All review authors contributed to revising the manuscript, reviewed all drafts and agreed on the final version.

Declarations of interest

HT: none known.

YT: none known.

YN: none known.

MA: none known.

YK: none known.

Sources of support

Internal sources

  • Hyogo Prefectural Amagasaki General Medical Center, Japan.

  • Kyoto University, Japan.

  • University of Tokyo, Japan.

  • Shiga University of Medical Science Hospital, Japan.

External sources

  • No sources of support supplied

Differences between protocol and review

We planned to present the sensitivity, specificity, positive and negative likelihood ratios, and diagnostic odds ratio for the detection of appropriate gastric tube placement (Glas 2003); however, we did not calculate the positive predictive value or negative predictive value because these values of individual studies were profoundly affected by the incidence of their studies and might cause confusion for readers when they apply the findings to their own setting. We did not calculate the diagnostic odds ratio because of the sparse data. We did not synthesize the diagnostic accuracy estimates of included studies because of the heterogeneity of the index test (the difference of echo window, combined with other confirmation methods and ultrasound during insertion of the tube). Alternatively, we presented true positive = correct gastric tube placement and correct visualization by ultrasound; false positive = incorrect gastric tube placement but failure to visualize by ultrasound; false negative = correct gastric tube placement but failure to visualize by ultrasound; true negative = incorrect gastric tube placement and correct visualization by ultrasound in Summary of findings 1. We tailored the QUADAS-2 tool before application to all included studies in our published protocol for the review because the agreement had been poor and we considered further refinement of the tool was needed (e.g. omitted unimportant signalling questions) (Whiting 2011).

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Basile 2015

Study characteristics
Patient samplingConsecutive enrolment, no information available regarding participant exclusion.
Patient characteristics and settingNo information available among participant characteristics and setting.
Index tests

Ultrasound (with and without 60 mL of air injected) by trained nurses.

Blinded to whoosh test.

Target condition and reference standard(s)No detailed information available.
Flow and timing

Participants were first tested with ultrasound (with and without 60 mL of air injected) as compared with whoosh test performed by other nurses.

No information available regarding timing of reference standard or dropout of participants.

Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Yes  
Was a case-control design avoided?Yes  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?Unclear  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Unclear  
  UnclearUnclear
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Unclear  
  UnclearLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?Unclear  
Were the criteria of reference standard for target condition prespecified?Unclear  
  UnclearLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Unclear  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewUnclear  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsUnclear  
  Unclear 

Brun 2012

Study characteristics
Patient sampling

No detailed information available regarding random or consecutive sampling.

Inclusion criteria: people benefiting from the prehospital insertion of an NG tube after tracheal intubation.

Exclusion criteria: aged < 18 years; supported during an interhospital transportation; presenting a suspected fracture of the bones of the skull base; and who absorbed detergents, oil or foam products.

Patient characteristics and settingAged ≥ 18 years, intubated in prehospital setting by EMS team which included a physician. Excluded people with suspicion of cranial base fracture and who had a history of caustic agent ingestion.
Index testsTitan ultrasound machine in all ambulances. Physicians on board, who were e-FAST trained, received 1-day training for ultrasound verification of NG tube placement. Standardized method included a left subcostal view with the ultrasound probe while NG tube inserted by EMS staff. If not initially seen on ultrasound, 50 mL of air injected through NG tube. X-ray control carried out at hospital and compared with prehospital results.
Target condition and reference standard(s)Chest X-ray on arrival at the hospital.
Flow and timing

No exclusions described.

Ultrasound test performed. If not initially seen on ultrasound, 50 mL of air was injected through the NG tube. X-ray control carried out at hospital and compared with the prehospital results.

Comparative 
Notes2 review authors (HT and YT) assessed based on the extracted data.
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?No  
Was a case-control design avoided?Unclear  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?Yes  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?No  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Unclear  
  UnclearLow
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Yes  
  LowLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?Unclear  
Were the criteria of reference standard for target condition prespecified?Unclear  
  UnclearLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Yes  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewYes  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsYes  
  Low 

Brun 2014

Study characteristics
Patient sampling

Prospective single-centre observational study performed between November 2012 and May 2013 in mobile emergency and resuscitation service.

Inclusion criteria: aged ≥ 18 years receiving prehospital care and requiring GT insertion.

Exclusion criteria: aged ≤ 18 years, pregnant women, contraindication at GT insertion, interhospital transfers and absence of X-ray control.

After verification of correct GT placement by the auscultation method or whoosh test (instillation of air in the tube with sounds heard simultaneously through a stethoscope placed over the stomach region) combined with the aspirate method (visual inspection of aspirate contents), ultrasound test was performed.

Patient characteristics and setting

Prior test: auscultation method or whoosh test (instillation of air in tube with sounds heard simultaneously through stethoscope placed over stomach region) combined with aspirate method (visual inspection of aspirate contents).

Presentation: in prehospital setting, emergency physician checked GT placement using ultrasonography during GT insertion by nurse or just after epigastric auscultation and aspirate method was realized.

Intended use of index test: to determine whether or not the GT could be viewed in the oesophagus, stomach, or both.

Index tests

Probe placed transversely on the anterior neck just superior to the suprasternal notch midline at level of thyroid gland and focused on visible part of oesophagus, with longitudinal and transversal viewing, then probe placed in subxiphoid area and oriented towards left upper abdominal quadrant to visualize stomach, with transverse and longitudinal viewing.

Antrum imaged in a transversal plane in epigastric area using left lobe of liver as an internal landmark, angling transducer towards left subcostal area imaged the gastric body. Ultrasound examination considered positive when GT was visualized, appearing as an hyperechogenic circle posterior to the thyroid tissue adjacent to trachea, and as a hyperechogenic line in stomach. When GT was seen in oesophagus and not in stomach, 50 mL of air injected through GT, if ultrasonography showed dynamic fogging in stomach, GT considered in stomach.

Target condition and reference standard(s)

X-ray on arrival at hospital.

Details of interpretation: unclear.

Flow and timing

No participants excluded.

After verification of correct GT placement by auscultation method or whoosh test (instillation of air in tube with sounds heard simultaneously through stethoscope placed over stomach region) combined with the aspirate method (visual inspection of aspirate contents), ultrasound test was performed. If not initially seen on ultrasound, 50 mL of air injected through NG tube.

X-ray control carried out at hospital and compared with prehospital results.

Unclear time interval.

No information comparing index test and reference standard.

Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Yes  
Was a case-control design avoided?Yes  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?Unclear  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?No  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Yes  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Yes  
  HighLow
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Yes  
  LowLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?Unclear  
Were the criteria of reference standard for target condition prespecified?Unclear  
  UnclearLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Yes  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewUnclear  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsYes  
  Unclear 

Chenaitia 2012

Study characteristics
Patient sampling

Prospective multicentre study in people undergoing GT insertion in prehospital setting conducted in 2 French towns (Marseille and Grasse) over 1-year period from May 2010 to May 2011.

Inclusion criteria: aged ≥ 18 years, prehospital settings and requiring GT insertion.

Exclusion criteria: aged < 18 years, pregnant, interhospital transfers and absence of X-ray control.

After insertion and securing of GT by auscultation or whoosh test, emergency physician verified correct placement of GT by ultrasound.

Patient characteristics and setting

Prior test: auscultation method or whoosh test (instillation of air in tube with sounds heard simultaneously through stethoscope placed over stomach region) combined with aspirate method (visual inspection of aspirate contents).

Presentation: after insertion and securing of GT, emergency physician verified correct placement of GT by ultrasound.

Intended use of index and setting: confirming accurate GT placement.

Setting: prehospital.

Index tests

After insertion and securing of GT, emergency physician verified correct placement of GT by ultrasound.

Technique standardized; probe placed in the subxiphoid area then oriented towards left upper abdominal quadrant to visualize stomach, with transverse viewing, antrum imaged in a transversal plane in epigastric area using left lobe of liver as internal landmark, gastric body imaged by angling transducer towards left subcostal area. Ultrasound examination considered positive when GT appeared as a hyperechogenic line in stomach.

Videorecorded showing GT tip; 2 radiologists reviewed each video to confirm results.

Target condition and reference standard(s)Final confirmation of GT placement was X-ray on arrival at hospital.
Flow and timing

No participants excluded.

Time interval and interventions between index tests and reference standard not described.

Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Yes  
Was a case-control design avoided?Yes  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?Unclear  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?No  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Yes  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Yes  
  HighLow
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Yes  
  LowLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?Unclear  
Were the criteria of reference standard for target condition prespecified?Unclear  
  UnclearUnclear
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Yes  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewUnclear  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsYes  
  Low 

Gok 2015

Study characteristics
Patient sampling

Inclusion criteria: mechanically ventilated participants monitored in ICU between February and July 2014 who received ultrasound-guided NG tube placement.

Exclusion criteria: history of neck surgery (e.g. tracheotomy), anatomic deformity, nasal fracture or severe coagulopathy; aged < 16 years.

Tube removed if coughing and dyspnoea occurred during placement.

Patient characteristics and setting

Prior test: none.

Presentation: 56 mechanically ventilated participants monitored in ICU between February and July 2014 who received ultrasound-guided NG tube placement.

Intended use of index test: 'real-time' imaging of passage of NG tube through oesophagus.

Setting: ICU.

Index tests

Image of empty oesophagus obtained, then inserted NG tube 10-14 Fr in thickness from appropriate nostril by adjusting nasal passage. Subsequently, NG tube gently advanced, and passage visualized with ultrasound. Oesophagus primarily viewed in transverse plain then attempt made to obtain a longitudinal view.

Ultrasound performed to obtain sonographic image of oesophagus before removing guidewire of NG tube.

Target condition and reference standard(s)

After ultrasound-guided tube insertion, gastric placement of the NG tube tip confirmed with abdominal X-ray.

All reference standard results interpreted by a single person.

Used prespecified criteria of correct position, i.e. NG tube tip below the diaphragm; should follow straight course down midline of chest to a point below diaphragm.

Flow and timing

No participants excluded.

Unclear time interval. No test performed between index tests and reference standard.

Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Yes  
Was a case-control design avoided?Yes  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?No  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Yes  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Yes  
  LowLow
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Yes  
  LowHigh
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?No  
Were the criteria of reference standard for target condition prespecified?Yes  
  LowLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Yes  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewUnclear  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsYes  
  Low 

Kim 2012

Study characteristics
Patient sampling

Prospective study performed between May and September 2011 in a local emergency centre. Included participants with low consciousness in whom correct placement of NG tube was ultimately verified by chest X-ray.

Inclusion criteria: aged > 18 years, undergoing NG tube insertions for reasons including drug overdose, suspicion of gastric bleeding, endotracheal intubation and others.

10 participants excluded because they did not receive X-ray confirmation.

Patient characteristics and setting

Prior test: auscultation, pH testing and ultrasound performed in random order.

Presentation: participants with low consciousness in whom correct placement of NG tube was ultimately verified by chest X-ray.

Intended use of index test: to verify gastric intubation.

Setting: EMS.

Index tests

Ultrasound examinations included a transversal scan performed prior to tube insertion from either right or left side of the participant's neck to verify that oesophagus was located behind respiratory tract.

Attempted visualization of NG tube in separate scans of fundus and antrum of stomach. Used linear probe for study of neck and convex probe for stomach. If visualization not possible, 40 mL of normal saline and 10 mL of air were injected through NG tube and if ultrasonography showed dynamic fogging in stomach, gastric placement of tube was verified.

Target condition and reference standard(s)Chest X-rays interpreted by emergency medicine specialist who did not perform ultrasound examinations.
Flow and timing

10 participants excluded because they did not receive X-ray confirmation; no other participants excluded from analysis.

Auscultation, pH testing and ultrasound performed in random order. If ultrasound visualization not possible, 40 mL of normal saline and 10 mL of air were injected through NG tube and if ultrasonography showed dynamic fogging in stomach, gastric placement of tube was verified. After these tests, an emergency medicine specialist who did not perform ultrasound examinations interpreted chest X-rays.

Unclear time interval.

Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Yes  
Was a case-control design avoided?Yes  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?Unclear  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Unclear  
  LowLow
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Yes  
  LowLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?Unclear  
Were the criteria of reference standard for target condition prespecified?Unclear  
  UnclearLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Yes  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewUnclear  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsYes  
  Low 

Lock 2003

Study characteristics
Patient sampling

Inclusion criteria: people in ICU, endotracheal intubation and ventilation or independent breathing.

Exclusion criteria: percutaneous endoscopic gastrostomy tube.

How were participants' coughs managed: not reported.

Patient characteristics and setting

Adults aged 16-84 years.

In 50/60 procedures, participants were endotracheally intubated and ventilated. In 10/60 procedures, participants were breathing spontaneously, none had a tracheostomy.

Prior test: not reported.

Presentation: people in ICU, endotracheal intubation and ventilation or independent breathing.

Intended use of index test: to replace X-ray for verification of GTs.

Setting: ICU.

Index tests

Correct placement of tip of tube in stomach ascertained by ultrasound by detecting a 50 mL air jet applied with a syringe via the GT.

Ultrasound performed by 10 experienced examiners/practitioners.

Reference standard test (radiological control) done after index test (ultrasound).

Results of ultrasound and other control methods compared to radiological control of tube.

Target condition and reference standard(s)X-ray of the lower thorax or upper abdomen. Incorrect localization of tube defined as localization of tube in oesophagus or lungs.
Flow and timing

In 60 GT insertions (with 50 participants on artificial ventilation) performed on a medical ICU, correct placement of tube was controlled by auscultation, pH measurement of aspirate and ultrasound. In ultrasound, correct placement of tip of tube in stomach ascertained by detecting a 50 mL air jet applied with a syringe via GT. Results of ultrasound and other control methods compared to radiological control of tube.

Period between placement of GT and radiological control was within 24 hours.

Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Unclear  
Was a case-control design avoided?Unclear  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?Unclear  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?No  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?No  
  UnclearLow
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Yes  
  LowLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?Unclear  
Were the criteria of reference standard for target condition prespecified?Unclear  
  UnclearLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Yes  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewNo  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsYes  
  High 

Nikandros 2006

Study characteristics
Patient samplingProspective study in a 5-bed ICU performed between May and September 2005.
Patient characteristics and setting

Included 16 participants, 9 men and 7 women, mean (± SD) age 66.3 ± 7.1 years, mean (± SD) APACHE II score 21 ± 5.2. All participants intubated and mechanically ventilated.

Prior test: not reported.

Presentation: people in ICU over 5-month period.

Intended use of index test: to replace radiology for verification of GTs.

Setting: ICU.

Index tests

Ultrasound confirmation of NG tube position by identifying air bubbles after injecting a 10 mL mixture of 5% dextrose and air and by standard X-ray.

No detailed information available regarding interpretation of results.

Target condition and reference standard(s)NG tube position also confirmed by X-ray. No detailed information available.
Flow and timing

Median (± SD) procedure time 14.93 ± 1.71 minutes for ultrasound and 84 ± 30.64 minutes for X-ray (P < 0.001).

No detailed information regarding timing, time gap, withdrawals and any intervention between index test and reference standard available.

Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Unclear  
Was a case-control design avoided?Yes  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?Unclear  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Unclear  
  UnclearLow
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Unclear  
  UnclearLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?Unclear  
Were the criteria of reference standard for target condition prespecified?Unclear  
  UnclearLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Yes  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewUnclear  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsUnclear  
  Unclear 

Radulescu 2015

Study characteristics
Patient samplingNo detailed information available.
Patient characteristics and settingNo detailed information available.
Index testsAnterolateral neck scanned in high frequency to visualize GT tube's characteristic echogenic surface with posterior anechoic shadow in oesophagus. Then, right diaphragm location identified by low-frequency imaging. Comparisons of ultrasound findings made to chest X-ray findings. Data collected by a single internal medicine resident.
Target condition and reference standard(s)No detailed information available. Data collected by a single internal medicine resident.
Flow and timingNo detailed information regarding timing, time gap, withdrawals and any intervention between index test and reference standard.
Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Unclear  
Was a case-control design avoided?Unclear  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?Unclear  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Unclear  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Unclear  
  UnclearUnclear
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?No  
  HighLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?No  
Were the criteria of reference standard for target condition prespecified?Unclear  
  HighLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Unclear  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewUnclear  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsUnclear  
  Unclear 

Vigneau 2005

  1. a

    APACHE II: Acute Physiology and Chronic Health Evaluation II; eFAST: extended Focused Assessment with Sonography for Trauma; EMS: emergency medical service; GT: gastric tube; ICU: intensive care unit; n: number of participants; NG: nasogastric; SD: standard deviation.

Study characteristics
Patient sampling

Consecutive participants during a 2-month period who received a weighted tip NG tube (12CH, Cair, France) for enteral feeding between 8:30 a.m. and 8:00 p.m.

Exclusion criteria: NG tubes inserted during other periods, when only 1 physician was on duty.

When participants coughed too much, tube removed and reinserted (author's reply). Examiner did not reinsert the tube when there was no auscultation (author's reply).

Patient characteristics and setting

35 weighted tip NG tubes inserted in 33 participants (18 men, 15 women; mean (± SD) age 62.2 ± 19.8 years; mean (± SD) Simplified Acute Physiology Score II score 48 ± 20.7; mean (± SD) body mass index 24.8 ± 5.8).

26 (79%) participants mechanically ventilated at the time tube insertion and 19 (73%) sedated. Main diagnoses on ICU admission were acute aggravation of chronic respiratory failure (n = 8), community-acquired pneumonia (n = 4), pulmonary pneumocystosis (n = 1), acute respiratory distress syndrome (n = 3), septic shock (n = 6), myasthenia gravis (n = 1), stroke (n = 3) and other disorders (n = 5).

Prior test: none described.

Presentation: daytime weighted NG tube insertion.

Intended use of index: ensuring correct tube placement.

Setting: ICU.

Did not differentiate gastric or enteric tube (i.e. possibly passing through pyloric ring to the duodenum).

Index tests

Duodenum examined in middle epigastric area; if duodenum or NG tip (or both) not visualized, probe oriented towards left upper abdominal quadrant to visualize gastric area. If NG tip still not visible, 5 mL normal saline mixed with 5 mL air injected into tube to visualize the hyperechogenic 'fog' exiting tip. NG tube tip considered correctly located when surrounded by hydric and echogenic moving formations (related to peristalsis).

Did not specifically record cases of pneumothorax or intrabronchial NG tube location or precise gastric/duodenal location of tip.

Examiner did not use prespecified criteria of ultrasound (author's reply).

Target condition and reference standard(s)

As soon as tube was correctly inserted, radiology department performed confirmatory X-ray.

Blinded design of study required NG tube tip verification by 2 physicians, 1 to interpret X-rays and 1 to perform ultrasound examination. Each physician was unaware of the other's findings. Examiner did not use prespecified criteria of X-ray (author's reply).

Flow and timingNo detailed information regarding timing, withdrawals and any intervention between index test and reference standard. Time gap between index test and reference standard not recorded (author's response).
Comparative 
Notes 
Methodological quality
ItemAuthors' judgementRisk of biasApplicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?Yes  
Was a case-control design avoided?Yes  
How were participants' coughs managed? Did the study avoid reinsertion of the tube when participants coughed too much?No  
How were auscultation findings (e.g. bubbling sounds) dealt with? Did the study avoid reinsertion of the tube when auscultation was not found?Yes  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom the GT was difficult to place?Yes  
Did the study avoid inappropriate exclusions? Did the study avoid excluding participants for whom tubes were difficult to visualize?Yes  
  LowHigh
DOMAIN 2: Index Test Ultrasound
Were the index test results interpreted without knowledge of the results of the reference standard?Yes  
  LowLow
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?Yes  
Were the reference standard results interpreted without knowledge of the results of the index tests?Yes  
Were the criteria of reference standard for target condition prespecified?No  
  LowLow
DOMAIN 4: Flow and Timing
Did all patients receive the same reference standard?Yes  
Was there an appropriate interval between the index test and reference standard? We set an arbitrary 4 hours for this reviewYes  
Were all participants included in the analysis? Consider withdrawals and withdrawals who were likely to impact on study results. Also consider the exclusion of 'difficult' participantsYes  
  Low 

Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion
Blaivas 2012Editorial.
Dagli 2015Nasoenteric tubes inserted into the postpyloric area.
Greenberg 1993Transpyloric tube.
Hernandez-Socorro 1996Not a diagnostic test accuracy study. Compared method for placing feeding tubes.
Kerforne 2013Case report.
Lock 1997Letter.
Tamhne 2006pH-specific paper used as reference standard.
Wagai 1981Case series.
Xiao-feng 2015Nasal-jejunal tube.

Ancillary