Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 99

Inclusion criteria: body mass index between 30 and 50 kg/m²; orotracheal intubation required for elective surgery

Exclusion criteria: no details

Baseline characteristics:

Pentax AWS

Age: 50 (SD ± 12)

Gender M/F: 11/39

BMI: 41.2 (SD ± 4.4)

ASA II: 15

ASA III: 32

ASA IV: 3

Mallampati 1: 21

Mallampati 2: 18

Mallampati 3: 7

Mallampati 4: 4

Macintosh

Age: 49 (SD ± 14)

Gender M/F: 10/39

BMI: 42.5 (SD ± 5.9)

ASA II: 7

ASA III: 40

ASA IV: 2

Mallampati 1: 14

Mallampati 2: 21

Mallampati 3:13

Mallampati 4: 0

Country: USA

Setting: hospital

Interventions

Pentax AWS (n = 50) vs Macintosh blade (n = 49)

Macintosh laryngoscope with a #4 blade

Outcomes

Continuous outcomes:

Time to intubation: defined as time from start of first attempt of insertion of laryngoscope until a capnogram signal was obtained. Median (Q1, Q3) time: Pentax 38 (31, 50) seconds vs Macintosh 26 (22, 29) seconds. Adjusted for Mallampati and ASA status: hazard ratio 0.35, 95% confidence interval 0.23 to 0.55, P < 0.001. No evidence of a learning curve on time to intubation with the Pentax AWS based on analysis of sequence quartiles

Ease of intubation on a scale of 0 to 100 (0 as easiest): VLS 52 (SD ± 31), Mac 40 (SD ± 28); P = 0.02

CL glottic view reported with CL 1 and 2: grouped as good; CL 3 and 4: grouped as poor. Data not reported for this outcome

Dichotomous outcomes:

Laryngeal/airway trauma

Sore throat

Successful first attempt

No. of attempts: 1 to 3

Notes

Baseline characteristics: more women than men in each group. More ASA II in Pentax group, more ASA III in Macintosh group. More Mallampati scores of 1 in Pentax group, more Mallampati scores of 2 in Macintosh group

Conclusions of study authors: Although Pentax AWS often provided a superb glottic view, time required for intubation was longer than for Macintosh. Success was better with Mactinosh blade. AWS should not be substituted routinely for a conventional Macintosh #4 blade in morbidly obese patients.

Funding/declarations of interest: supported by internal funds; Pentax on loan from manufacturers for duration of the study

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "Randomization was based on computer‐generated, random‐block codes"

Allocation concealment (selection bias)

Low risk

Quote: "sequentially numbered opaque envelopes"

Comment: assumed envelope was sealed

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Quote: "it was impossible to blind the operator to the device being used"

Comment: this will affect all outcomes for this domain.

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: Observers who looked at blood staining and postoperative sore throat were blinded to group allocation. However, it was not possible to blind outcome assessors to primary outcomes.

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Quote: "Of 105 randomized patients, 4 did not complete the study because of cancellation of surgery or because the laryngoscopist could not arrive to the operating room on time, and 2 patients in the Pentax group had missing primary outcomes"

Comment: few losses, unlikely to introduce any bias

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

High risk

Quote: "All patients’ tracheas were intubated by 1 of 2 attending anesthesiologists, each of whom had previously used the Pentax AWS 5 to 10 times before the study began"

Comment: it is likely that the balance of experience will favour the Macintosh group

Baseline characteristics

Low risk

Quote: "patients in the Pentax group were more likely to have better ASA physical status and better Mallampati scores (absolute standardized difference 0.25)"

Comment: small difference unlikely to be clinically relevant

Funding sources

Unclear risk

Comment: supported by internal funds; Pentax on loan from manufacturers for duration of study

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 50

Inclusion criteria: normal intraocular pressure, scheduled for ophthalmic surgery requiring tracheal intubation

Exclusion criteria: no details

Baseline characteristics: described as comparable but no details given; abstract only

Country: Saudi Arabia

Setting: hospital

Interventions

GlideScope vs Macintosh blade

Outcomes

Continuous outcomes:

Duration of intubation

Other outcomes:

MAP and HR, plus intraocular pressure

Notes

Additional: email sent to authors to request additional details; additions made to risk of bias tables following study author response

Funding/declarations of interest: none (confirmed by study authors in email)

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Quote: "randomly assigned"

Comment: Email information from study authors states use of sealed envelopes

Allocation concealment (selection bias)

Unclear risk

Comment: no details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: abstract only; insufficient details but no blinding assumed

Incomplete outcome data (attrition bias)
All outcomes

Unclear risk

Comment: abstract only; insufficient details

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Low risk

Comment: Email information from study authors states intubators had 5 years' experience with GlideScope and up to 20 years' experience with Macintosh blade

Baseline characteristics

Unclear risk

Comment: no details

Funding sources

Low risk

Comment: Email information from study authors states no additional funding used for study

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 100

Inclusion criteria: all patients scheduled for elective bariatric surgery, BMI > 35 kg/m² and age > 18 and < 60 years

Exclusion criteria: severe mental illness, ongoing alcohol or substance abuse, previous difficult intubation, patient considered by the anaesthesiologist to require a different procedure of anaesthesia or intubation (e.g. fibreoptic intubation) than prescribed by the study protocol

Baseline characteristics:

GlideScope

Age: 42 SD ± 10 (range 21–60)

Gender M/F: 15/35

BMI: 42 SD ± 6 (range 35–62)

Mallampati ≥ 3: 11

Height (cm): 171 SD ± 10 (range 150–195)

Weight (kg): 125 SD ± 10 (range 92–190)

Macintosh

Age: 41 SD ± 8 (range 28–59)

Gender M/F: 9/31

BMI: 41 SD ± 5 (range 35–56)

Mallampati 3: 16

Height (cm): 172 SD ± 7 (range 157–194)

Weight (kg): 122 SD ± 18 (range 90–167)

Country: Denmark

Setting: hospital

Interventions

GlideScope (n = 50) vs Macintosh blade (n = 50)

GlideScope participants in ramped position; #4 blade used; stylet bent at 90 degrees, as per manufacturer guidelines

Macintosh participants in ramped position; #3 or #4 blade at the intubator’s discretion; hockey‐stick‐shaped stylets

Outcomes

Continuous outcomes:

Time to intubation (time from gripping the laryngoscope until registration of expired CO₂): GlideScope (median (range)): 48 (22‐148); Mac 32 (17‐209)

Difficulty of intubation: no difference in subjective difficulty of intubation, but IDS scores significantly lower in GlideScope group; median IDS score: GlideScope group 1 (0–4); Mac 2 (0–7) (P = 0.01)

Dichotomous outcomes:

Failed intubation: defined as not achieving intubation in maximum 2 attempts

Hypoxia: defined as oxygen desaturation < 93%

Laryngeal/airway trauma: defined as mucosal injury, airway bleeding, dental trauma

Sore throat/hoarseness (assessed at 1 hour post extubation on a VAS): sore throat present in 40% in GlideScope group vs 42% in Macintosh group

No. of attempts: 4 participants in Macintosh group required more than 1 attempt at intubation vs 1 in GlideScope group (P = 0.36). Two of the 4 participants in the Macintosh group proved impossible to intubate within 2 attempts with direct laryngoscopy (i.e. failed intubation) and were subsequently intubated with the GlideScope with no problem.

CL glottic view: 1 to 4

Notes

Experience of intubator: all intubations performed by 1 of 5 certified nurse anaesthetists or 2 anaesthesiologists, all with prior experience with at least 20 GlideScope intubations and with wide experience in anaesthetizing obese patients

Funding/declarations of interest: departmental funding only

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "computer‐generated random numbers"

Allocation concealment (selection bias)

Low risk

Quote: "sealed opaque envelopes packed by an outside investigator"

Comment: does not state that envelopes are sequentially numbered, but low risk of bias assumed with use of outside investigator

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: no attempt to blind outcome assessors

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Quote: "One hundred consecutive patients were enrolled after which the trial was ended as planned. All eligible patients gave consent to participate, none were excluded or failed to complete, and all were included in the final analysis"

Selective reporting (reporting bias)

Low risk

Comment: copy of protocol on clinicaltrials.gov sought and compared with published trial (clinical trials ID NCT00917033); all outcomes reported

Experience of intubator

Low risk

Quote: "All intubations were performed by one of five certified nurse anaesthetists or two anaesthesiologists all with prior experience from at least 20 GS (GlideScope) intubations and with wide experience in anesthetizing obese patients"

Baseline characteristics

Low risk

Quote: "The patients in the two groups were comparable with regards to demographic and airway characteristics"

Funding sources

Low risk

Comment: departmental funding only

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 36

Inclusion criteria: patients between 20 and 80 years of age, ASA I or II, scheduled to undergo elective surgery requiring intubation

Exclusion criteria: risk factors for cardiopulmonary disease, predicted or history of difficult intubation (cervical spine abnormality, restricted neck mobility), gastric aspiration

Baseline characteristics:

Pentax AWS

Age: 61.7 (SD ± 8.8)

Gender M/F: 8/10

Height (m): 160.0 (SD ± 8.6)

Weight (kg): 59.7 (SD ± 14.1)

Mallampati 1: 10

Mallampati 2: 8

Mallampati 3: 0

Macintosh

Age: 56.7 (SD ± 17.3)

Gender M/F: 13/5

Height (m): 163.9 (SD ± 7.1)

Weight (kg): 63.5 (SD ± 11.3)

Mallampati 1: 8

Mallampati 2: 9

Mallampati 3: 1

Country: Japan

Setting: hospital

Interventions

Pentax AWS (n = 18) vs Macintosh (n = 18)

A pillow was placed under the participant's head, and an appropriately sized semirigid cervical collar was fitted around the neck to simulate limited neck movements.

Macintosh blade #3 or #4

Outcomes

Continuous outcomes:

Time for tracheal intubation: defined as time when the airway device was handed to the anaesthesiologist to time when the presence of carbon dioxide was confirmed in the exhaled breath on the vital sign monitor

Difficulty of intubation: IDS score distribution: AWS score of 0 in 14 participants, score of 1 in 3 participants; Mac score of 0 in 1 participant, score of 1 in 5 participants, score of 2 in 3 participants, 3 in 4 participants, 4 in 3 participants, 5 in 1 participant

Dichotomous outcomes:

Failed intubation (1 failure in AWS group due to insufficient interincisor space compared with thickness of the blade; 1 failure in Mac group due to tooth injury; failures excluded from CL data)

Laryngeal/airway trauma (lip injury, blood on device)

Participant reported sore throat (pharyngeal pain)

Hoarseness

No. of attempts: 1 to 4

CL glottic view: 1 to 4

Notes

Experience of intubator: In all cases, laryngoscopy was performed by 1 anaesthesiologist experienced in the use of both devices

Funding/declarations of interest: none

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Comment: described as randomized but no additional details given

Allocation concealment (selection bias)

Unclear risk

Comment: no details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: time measured by independent observer, but not possible to blind observer for other outcomes

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: one participant from each group had failed intubation, and subsequent analyses of outcomes did not include these missing participants. However, losses were few

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Low risk

Comment: all laryngoscopies performed by 1 anaesthetist experienced with both devices

Baseline characteristics

Low risk

Comment: baseline characteristics equivalent

Funding sources

Low risk

Comment: none

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 80

Inclusion criteria: pregnant patients undergoing caesarean section surgery under general anaesthesia

Exclusion criteria: presence of cardiovascular, hepatic, renal or neuromuscular disease, non‐co‐operation, restricted neck movements, retrognathia, ASA score of III or IV, Mallampati score of 4, history of airway‐related surgery, emergency surgery. Additionally, patients who had more than 2 of the following criteria were excluded: Mallampati score of 3, maximal mouth‐opening capacity < 35 mm, thyromental distance < 65 mm

Baseline characteristics:

McGrath

Age: 27.55 (SD ± 3.82)

Height (cm): 162.9 (SD ± 6.15)

Weight (kg): 77.90 (SD ± 13.71)

BMI: 29.45 (SD ± 5.6)

ASA I: 28

ASA II: 12

Mallampati 1: 19

Mallampati 2: 19

Mallampati 3: 2

Macintosh

Age: 29.25 (SD ± 4.41)

Height (cm): 160.8 (SD ± 6.0)

Weight (kg): 72.32 (SD ± 9.82)

BMI: 27.98 (SD ± 3.22)

ASA I: 24

ASA II: 16

Mallampati 1: 21

Mallampati 2: 19

Mallampati 3: 0

Country: Turkey

Setting: hospital

Interventions

McGrath series 5 (n = 40) vs Macintosh (n = 40)

McGrath blade: use of stylet to guide tube during videolaryngoscopy

Macintosh blade #3 or #4

Outcomes

Continuous outcomes:

Time for tracheal intubation: defined as time from anaesthesiologist taking the laryngoscope in his hand until first upward deflection on the capnograph after connection of the anaesthetic ventilation system to the tracheal tube

POGO

Dichotomous outcomes:

Failed intubation

Laryngeal/airway trauma: no palatoglossal arch nor dental injuries in either group

Successful first attempt

CL glottic view: 1 to 4

Other outcomes: haemodynamic outcomes

Notes

Funding/declarations of interest: none apparent

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "computer‐generated random numbers"

Allocation concealment (selection bias)

Unclear risk

Quote: "sealed‐envelope technique"

Comment: no additional details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetists

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: assumed no attempts made to blind outcome assessors

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no apparent losses

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Unclear risk

Quote: "All intubations were performed by an experienced anesthesiologist"

Baseline characteristics

Low risk

Quote: "There was no significant difference in the demographic data and preprocedural intubation conditions between the groups"

Funding sources

Low risk

Comment: none apparent

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 109

Inclusion criteria: age ≥ 18 years and requiring emergency tracheal intubation in the prehospital setting only during the day shift

Exclusion criteria: none given

Baseline characteristics:

Pentax AWS

Age: 74.4 (SD ± 13.6)

Gender M/F: 34/22

Cardiac arrest participants: 54/56

Macintosh

Age: 74.1 (SD ± 13.0)

Gender M/F: 38/15

Cardiac arrest participants: 47/53

Country: Japan

Setting: prehospital; paramedics/physicians travel together in ambulance to calls

Interventions

Pentax AWS (n = 56) vs Macintosh (n = 53)

A suction device and Magill forceps were available for use at any time

Outcomes

Continuous outcomes:

Difficulty of tracheal intubation(measured on IDS): median IDS (IQR): Pentax 0 (0‐1); Mac 1 (0‐2)

Number of attempts (before switching from AWS to Macintosh): 0 in 3 cases, 1 in 14 cases, 2 in 1 case, 3 in 2 cases; data not reported for switching from Macintosh to AWS (Note: In 3 cases, the alternative device was used before the procedure was even started)

Time for tracheal intubation (measured from insertion of the blade between the teeth to confirmation of endotracheal tube placement by capnograph. If intubation failed and the device for intubation was changed, time was measured from insertion on the first attempt to success on the second or successive attempts): median time (IQR) seconds: Pentax 155 (71–216); Mac 120 (60–170)

Dichotomous outcomes:

Failed intubation

Successful first attempt

Other: ultimate success of intubation (if intubation achieved within 600 seconds, even if change of device had taken place): Pentax 54/56; Mac 53/53

Notes

Experience of intubator: 6 physicians had previously worked as anaesthetists with an estimated range of 15 to 30 AWS intubations or > 100 Macintosh intubations per year. The remaining 5 had at least 50 Macintosh experiences but relatively fewer experiences with AWS intubation (but had received manikin training sessions)

Funding/declarations of interest: none

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Quote: "allocation was changed in a serial manner and was controlled by personnel at the physician car system center"

Allocation concealment (selection bias)

Unclear risk

Quote: "The operators were told which of the two devices had been allocated to them to use only when en route to the incident in the ambulance"

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind physician

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: all outcomes assessed by physician who was not blinded. Some potential for bias in the outcomes as operators were encouraged to complete intubation as quickly as possible, even if it was achieved by switching devices. Operators could be biased to familiar equipment; therefore change to an alternative device made frequently

Incomplete outcome data (attrition bias)
All outcomes

High risk

Quote: "Of 121 patients enrolled in this study, 12 were excluded due to missing data, age < 18 years, or problems with the device used, leaving 109 for final analysis"

Comment: high level of losses; no explanation about what problems with the device led to the exclusion of some patients

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Unclear risk

Quote: "6 physicians had generally performed N 100 intubations per year as they had previously worked as anesthetists. The number of AWS intubations they have performed is not precisely known, but is estimated to be in the range of 15 to 30 AWS intubations per physician per year. The remaining 5 physicians had done an anesthesia rotation and had performed at least 50 intubations, but with relatively fewer experiences with AWS intubation"

Comment: some variety of experience among personnel; unclear if these personnel were balanced between intervention and comparison groups

Baseline characteristics

Low risk

Comment: most baseline characteristics equivalent, except for differences in types of cases

Funding sources

Low risk

Comment: none

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 296

Inclusion criteria: patients with objective predictors of potentially difficult tracheal intubation: reduced cervical motion from pathological condition or cervical spine precautions (limited capacity to flex or extend the neck or managed with a cervical collar, but with negative imaging), Mallampati classification score of 3 or 4, reduced mouth opening (< 3 cm), history of difficult direct laryngoscopy

Exclusion criteria: a documented easy tracheal intubation (success on first attempt), history of failed intubation and failed bag‐mask ventilation, known unstable cervical spine injury, age < 18 years, presentation for an emergency surgical procedure

Baseline characteristics:

C‐MAC

Age: 54 (SD ± 14)

Gender M/F: 74/75

BMI: 34 (SD ± 10)

ASA I: 3

ASA II: 60

ASA III: 80

ASA IV: 6

Macintosh

Age: 55 (SD ± 15)

Gender M/F: 83/64

BMI: 34 (SD ± 10)

ASA I: 2

ASA II: 53

ASA III: 87

ASA IV: 5

Country: US

Setting: hospital

Interventions

C‐MAC (n = 149) vs Macintosh (n = 147)

External laryngeal manipulation, use of gum‐elastic bougie

Outcomes

Continuous outcomes:

Number of attempts: no details on number of attempts provided in the paper

Time for tracheal intubation: defined as time between blade insertion into the mouth and inflation of the endotracheal tube cuff

Dichotomous outcomes:

Failed intubation: defined as removal of laryngoscope from the mouth, then device selected at discretion of anaesthetist. Data taken only when an alternative device had been used

Laryngeal/airway trauma

Patient‐reported sore throat

Hypoxia: defined as oxygen desaturation < 90%

Successful first attempt: defined as confirmation of endotracheal tube placement by end‐tidal carbon dioxide with a single blade insertion

CL view achieved: 1 to 4

Success also given per providers:anaesthesiologists: C‐MAC 9/10, Mac 10/12; per residents: C‐MAC 64/67, Mac 78/91; per CRNAs: C‐MAC 65/72, Mac 36/44

Notes

Experience of intubator: C‐MAC: anaesthesiologist 10; resident 67; CRNA (supervised) 72; Macintosh: anaesthesiologist 12; resident 91; CRNA (supervised) 44

Funding/declarations of interest: supported by an investigator‐initiated grant (no. 00520743‐2) from Karl Storz Endoscopy‐America

Additional: contact made with study author to confirm denominator figures in Table 3; email response in file

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "Randomization was performed in a 1:1 allocation ratio via specialized computer software"

Allocation concealment (selection bias)

Unclear risk

Quote: "Individual randomization cards were placed in concealed envelopes"

Comment: unclear if envelope was opaque, numbered or sealed

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Quote: "Both the study team and the anesthesia team remained blinded until the patient entered the operating room"

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Quote: "One of the investigators or a study nurse followed each patient into the operating room to record the relevant intubation and post intubation data"

Comment: for patient reported outcomes; no details of whether other outcome assessors were blinded or not

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Quote: "Three hundred patients were consented and enrolled in this randomized controlled study. There were four randomization failures that were excluded from analysis"

Comment: losses too few to create bias

Selective reporting (reporting bias)

Low risk

Quote: "pre‐registered online as NCT00956592"

Comment: clinical trial register protocol sourced; protocol outcomes comparable with study‐reported outcomes

Experience of intubator

High risk

Quote: "In three cases, the anesthesia team deviated from randomization to DL (Macintosh) and intubated with a video laryngoscope because of provider preference"

Comment: does not state whether all operators had equivalent experience with C‐MAC, but it is known that some operators preferred a particular device. Also, the level of qualification of the operators differed between devices, with more resident anaesthetists using the Macintosh, and more CRNAs using the C‐MAC

Baseline characteristics

Low risk

Comment: baseline characteristics largely comparable

Funding sources

High risk

Comment: supported by an investigator‐initiated grant (no. 00520743‐2) from Karl Storz Endoscopy‐America

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 68

Inclusion criteria: > 18 years, ASA I or II, scheduled for elective thoracic surgery

Exclusion criteria: rapid sequence induction, anticipated difficult airway, contraindication against use of double‐lumen tube

Baseline characteristics:

X‐lite

Age: 41.8 (SD ± 9)

Gender M/F: 28/6

BMI: 24 (SD ± 2.9)

ASA I: 23

ASA II: 11

Mallampati 1: 26

Mallampati 2: 8

Macintosh

Age: 44.6 (SD ± 10)

Gender M/F: 29/5

BMI: 22.98 (SD ± 2.19)

ASA I: 20

ASA II: 14

Mallampati 1: 24

Mallampati 2: 10

Country: Morrocco

Setting: hospital

Interventions

X‐lite videolaryngoscope (n = 34) vs Macintosh (n = 34)

Stylet used in both groups

Double‐lumen tube used in both groups

Outcomes

Continuous outcomes:

Time for tracheal intubation (from insertion of blade into mouth to capnography reading)

Dichotomous outcomes:

Failed intubation: defined as not successful after 3 attempts followed by intubation with alternative device

Laryngeal/airway trauma (dental trauma, oesophageal or vocal cord trauma or bleeding)

Hypoxia

No. of attempts: 1 to 2

CL glottic view: 1 to 4

Notes

Experience of intubator: intubator with at least 5 years' experience, including experience with X‐lite. No experience with double‐lumen tube with X‐lite

Funding/declarations of interest: none

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: computer‐generated randomization

Allocation concealment (selection bias)

Unclear risk

Comment: numbers concealed in envelopes until moment of intubation; no additional details about envelopes

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: assumed outcome assessors were not blinded from outcomes measured in theatre

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no losses

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

High risk

Comment: Anaesthetist had more than 5 years' experience with use of DLT and training in the use of X‐lite but no experience in use of X‐lite with double‐lumen tube. No details of experience with Macintosh provided

Baseline characteristics

Low risk

Comment: baseline characteristics comparable

Funding sources

Low risk

Comment: none

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 70

Inclusion criteria: > 18 years old, ASA I or II, scheduled for elective thyroid surgery

Exclusion criteria: anticipated difficult intubation, limited interdental distance, limited cervical mobility, limited thyromental difficulty or Mallampati 4. Those needing rapid sequence induction, those with gastro‐oesophageal reflux, hiatus hernia, diabetes, obesity

Baseline characteristics:

X‐lite

Age: 43.5 (SD ± 11.1)

Gender M/F: 11/24

Height (cm): 172.7 (SD ± 3.4)

Weight (kg): 71.1 (SD ± 8.3)

BMI: 23.9 (SD ± 2.9)

ASA I: 28

ASA II: 7

Mallampati 1: 16

Mallampati 2: 13

Mallampati 3: 5

Mallampati 4: 1

Macintosh

Age: 48.8 (SD ± 12.7)

Gender M/F: 8/27

Height (cm): 172.1 (SD ± 3.7)

Weight (kg): 73.9 (SD ± 8.2)

BMI: 25.0 (SD ± 3.1)

ASA I: 25

ASA II: 10

Mallampati 1: 15

Mallampati 2: 10

Mallampati 3: 8

Mallampati 4: 2

Country: Morrocco

Setting: hospital

Interventions

X‐lite videolaryngoscope (n = 35) vs Macintosh (n = 35)

External laryngeal manoeuvres used, with gum‐elastic bougie

Macintosh blade #3

Outcomes

Continuous outcomes:

Difficulty of tracheal intubation: IDS scores for difficulty of tracheal intubation ‐ X‐lite 0: 13/35; 1 to 5: 20/35; > 5: 2/35; Mac 0: 7/35; 1 to 5 19/35; > 5: 9/35)

Time for tracheal intubation: defined as sum of times for glottic visualization plus time from glottic visualization to tracheal intubation

Dichotomous outcomes:

Failed intubation (1 participant in Macintosh group was intubated with Airtraq after 3 attempts with Macintosh)

Laryngeal/airway trauma (blood on scope; "no dental or laryngeal trauma was noted in either group")

Hypoxia: defined as oxygen saturation < 92%

CL glottic view: 1 to 4

Notes

Experience of intubator: 3 intubators with experience of more than 500 intubations with Macintosh and more than 60 with X‐lite

Funding/declarations of interest: none

Addtional: study also included use of Airtraq scope ‐ excluded from this review

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: computer‐generated randomization

Allocation concealment (selection bias)

Unclear risk

Comment: concealed in envelopes, but no additional details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: outcome assessors independent but not possible to blind assessors in theatre

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no losses after randomization

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Low risk

Comment: although intubators had less experience with X‐lite, they were still sufficiently experienced in both devices

Baseline characteristics

Low risk

Comment: baseline characteristics comparable

Funding sources

Low risk

Comment: none

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 78

Inclusion criteria: patients scheduled for elective CABG

Exclusion criteria: patients with renal, hepatic disease, bleeding diathesis, diabetes mellitus, Mallampati score of 3 or 4, history of a difficult intubation and ASA class IV

Baseline characteristics:

GlideScope

Age: 57.28 (SD ± 9.91)

Gender M/F: 23/17

Height (cm): 163.73 (SD ± 10.15)

Weight (kg): 71.45 (SD ± 12.16)

Mallampati 1: 21

Mallampati 2: 16

Mallampati 3: 3

Mallampati 4: 0

Macintosh

Age: 58.58 (SD ± 10.87)

Gender M/F: 29/9

Height (cm): 165.47 (SD ± 8.10)

Weight (kg): 72.26 (SD ± 15.47)

Mallampati 1: 25

Mallampati 2: 12

Mallampati 3: 1

Mallampati 4: 0

Country: Iran

Setting: hospital

Interventions

GlideScope (n = 40) vs Macintosh (n = 38)

Use of stylet in both groups when required

Macintosh blade #3 or #4

Outcomes

Continuous outcomes:

Number of attempts

Time for tracheal intubation: defined as time from opening mouth to filling the tube cuff ‐ measured in seconds

Dichotomous outcomes:

Failed intubation

Respiratory complications

Laryngeal/airway trauma

Patient‐reported sore throat (sore throat and odynophagia reported together)

Successful first attempt

Notes

Experience of intubator: experienced, but no details on level of experience

Funding/declarations of interest: none apparent

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "Using online software (http://www.graphpad.com/quickcalcs/randomize1.cfm), patients were randomly allocated"

Comment: computer generated

Allocation concealment (selection bias)

Unclear risk

Comment: no details given

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: no mention of blinding; unlikely as timing of intubation was involved

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Quote: "Two patients were excluded because of long postoperative intubation period"

Comment: low number unlikely to cause bias

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Unclear risk

Quote: "all of tracheal intubations were performed by experienced anesthesiologists"

Comment: no information on whether amount of experience with each device was equivalent

Baseline characteristics

Low risk

Comment: baseline characteristics comparable

Funding sources

Low risk

Comment: none apparent

Study characteristics

Methods

Randomized controlled trial

Cross‐over

Participants

Total number of participants: 30

Inclusion criteria: adult patients scheduled for elective surgery under general anaesthesia, aged > 18 years to < 65 years, ASA I or II

Exclusion criteria: patient likely to be difficult to intubate according to SIAARTI recommendations

Baseline characteristics:

GlideScope followed by Macintosh

Age: 44 (SD ± 11)

Gender M/F: 8/7

BMI: 25.5 (SD ± 3)

Macintosh followed by GlideScope

Age: 41 (SD ± 12)

Gender M/F: 8/7

BMI: 26.4 (SD ± 2.8)

Country: Italy

Setting: hospital

Interventions

GlideScope (n = 15) vs Macintosh (n = 15)

GlideScope blade #4; "hockey stick" stylet used in GlideScope group

Macintosh blade #3 or #4

Outcomes

Continuous outcomes:

Time for tracheal intubation: defined as time from insertion of blade between incisors until tube cuff was inflated

Dichotomous outcomes:

Failed intubation

Laryngeal/airway trauma ("no injuries or dental damage were recorded")

"All were successfully intubated" ‐ but no definition of success given

Notes

Experience of intubator: 1 intubator experienced in both techniques; > 100 intubations with each device

Funding/declarations of interest: department funding only; no conflicts of interest

Additional: Study aimed to measure forces but also reported data on relevant outcomes. Study authors have not reported on CL grades, although this information is included in the Methods section.

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: use of a random number generator

Allocation concealment (selection bias)

Unclear risk

Quote: "numbered coded vehicles was the method used to achieve allocation concealment"

Comment: not clear what this means and whether this is sufficient

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetists

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: participants blinded to group assignment, but intraoperative data collected by non‐blinded anaesthetists and caregivers

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no apparent losses

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought. Methods section stated that CL grades were recorded, but they were not reported in the Results section

Experience of intubator

Low risk

Comment: 1 intubator experienced in both techniques; > 100 intubations with each device

Baseline characteristics

Low risk

Comment: baseline characteristics comparable

Funding sources

Low risk

Comment: departmental funding only

Study characteristics

Methods

Randomized controlled trial

Cross‐over

Participants

Total number of participants: 150

Inclusion criteria: ASA I to III scheduled for elective surgery in supine position with general anaesthesia, requiring tracheal intubation

Exclusion criteria: pathology of the upper respiratory or alimentary tract known or suspected, a rapid sequence induction indicated, an awake intubation appropriate because of a suspected or known difficult airway

Baseline characteristics:

C‐MAC3

Age: median (range) 54 (20‐74)

Gender M/F: 10/27

Height (cm): median (range) 168 (150‐186)

Weight (kg): median (range) 76 (54‐98)

BMI: median (range) 27 (20‐40)

Mallampati 1: 8

Mallampati 2: 23

Mallampati 3: 6

Mallampati 4: 0

Macintosh

Age: median (range) 49 (23‐82)

Gender M/F: 21/29

Height (cm): median (range) 170 (156‐196)

Weight (kg): median (range) 81 (60‐179)

BMI: median (range) 27 (20‐63)

Mallampati 1: 16

Mallampati 2: 20

Mallampati 3: 13

Mallampati 4: 1

C‐MAC4

Age: median (range) 46 (34‐72)

Gender M/F: 11/7

Height (m): median (range) 173 (163‐188)

Weight (kg): median (range) 82 (54‐150)

BMI: median (range) 27 (20‐40)

Mallampati 1: 4

Mallampati 2: 6

Mallampati 3: 7

Mallampati 4: 1

C‐MAC4/SBT

Age: median (range) 58 (27‐79)

Gender M/F: 28/17

Height (cm): median (range) 173 (155‐193)

Weight (kg): median (range) 78 (48‐135)

BMI: median (range) 27 (19‐44)

Mallampati 1: 9

Mallampati 2: 21

Mallampati 3: 15

Mallampati 4: 0

Country: Germany

Setting: hospital

Interventions

C‐MAC 3 (n = 37) vs C‐MAC4 (n = 18) vs C‐MAC/STB (n = 45) vs Macintosh (50)

Participants underwent 3 separate laryngoscopies with Macintosh or #3 or #4 C‐MAC blade. After 50 participants, C‐MAC #4 was changed to a straight blade technique (C‐MAC/STB). Order of laryngoscopies was determined by randomization.

Macintosh blade #3 or #4

Outcomes

Continuous outcomes:

Time for tracheal intubation: defined as time from touching tube to performing successful endotracheal placement

Dichotomous outcomes:

Failed intubation: defined as intubated with alternative device owing to limited glottic visualization

Laryngeal/airway trauma (any palatoglossal arch or dental injury)

Number of intubation attempts: 1 to 3

CL glottic view: not possible to interpret data from graphs

Notes

Experience of intubator: 1 of 3 anaesthesiologists with ≥ 8 years' experience (after training with manikins for C‐MAC scope)

Funding/declarations of interest: equipment supplied by Storz manufacturer. One study author is a member of the Storz advisory team and receives grant support for airway management studies.

Additional: cross‐over study with 3 arms, changed to 4 arms part of the way through the study. High risk of bias was introduced with changing of the protocol part of the way through

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: computer generated

Allocation concealment (selection bias)

Unclear risk

Comment: no details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: not possible to blind outcome assessors

Incomplete outcome data (attrition bias)
All outcomes

High risk

Comment: protocol changed part of the way through the study ‐ data not provided before and after protocol change. Therefore, not possible to assess whether high levels of bias were introduced by the decision. An additional group was introduced part of the way through the study, which led to exclusion of some participants from C‐MAC groups

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Unclear risk

Comments: 1 of 3 anaesthesiologists with ≥ 8 years' experience (after training with manikins for C‐MAC scope). Although personnel are described as experienced, the level of experience with C‐MAC is unclear

Baseline characteristics

Low risk

Comment: baseline characteristics reported according to intubating device; some differences in male and female ratios between groups, but not anticipated to make a difference

Funding sources

High risk

Comment: equipment supplied by Storz manufacturer. One study author is a member of the Storz advisory team and receives grant support for airway management studies

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 60

Inclusion criteria: ASA I or II, scheduled to undergo general anaesthesia between the ages of 15 and 60 years

Exclusion criteria: thyroid‐to‐chin length ≤ 5 cm, Mallampati class ≥ 3, mouth opening < 3 cm, restriction in neck extension or protruding front teeth, predicted to be difficult in intubation. Also, airway difficulty score > 8, including the evaluation criteria mentioned above, were predicted to be difficult to intubate

Baseline characteristics:

GlideScope

Age: 39.5 (SD ± 13.4)

Gender M/F: 16/14

Height (cm): 166.0 (SD ± 8.2)

Weight (kg): 64.5 (SD ± 9.2)

Macintosh

Age: 43.0 (SD ± 14.9)

Gender M/F: 15/15

Height (cm): 162.8 (SD ± 10.5)

Weight (kg): 61.2 (SD ± 11.7)

Country: Korea

Setting: hospital

Interventions

GlideScope (n = 30) vs Macintosh (n = 30)

Macintosh blade #3

Use of cricoid pressure by assistant in both groups

Outcomes

Continuous outcomes:

Difficulty of tracheal intubation (airway difficulty score (ADS) on VAS by anaesthesiologist: 0 is most easy and 10 is most difficult. GlideScope 6.7 (SD ± 0.9); Macintosh 6.6 (SD ± 0.6))

Improved visualization (POGO score (%): GlideScope 89.6 (SD ± 20.0); Macintosh 67.6 (SD ± 24.7), P < 0.05)

Time for tracheal intubation (measured in seconds): defined as time from when anaesthesiologist grabbed handle to when tube passed vocal cords

Notes

Experience of intubator: all intubations performed by 1 anaesthetist ‐ fully experienced and familiar with GlideScope

Funding/declarations of interest: none apparent

Note: Some participants were younger than 18 years of age and were not separated in the data

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Quote: "All patients were randomly allocated"

Comment: no additional details

Allocation concealment (selection bias)

Unclear risk

Comment: no mention of concealment method

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: all outcomes assessed during intubation period were assumed to be not blinded

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no apparent losses

Selective reporting (reporting bias)

Unclear risk

Comment: protocol not sought

Experience of intubator

Low risk

Quote: "study was carried out by a fully experienced anesthesiologist familiar with the GVL (GlideScope)"

Baseline characteristics

Low risk

Quote: "no statistical differences in age, sex, height, weight and ADS between the two groups"

Funding sources

Low risk

Comment: none apparent

Study characteristics

Methods

Randomized controlled trial

Cross‐over design

Participants

Total number of participants: 44

Inclusion criteria: undergoing elective surgery under general anaesthetic with tracheal intubation, ≥ 1 risk factor for a difficult laryngoscopy (from unpublished data: ASA I to III; over 18 years of age; requiring single‐lumen tracheal intubation)

Exclusion criteria:

(from unpublished data: rapid sequence induction or other alternative intubation methods indicated; known or suspected oral, pharyngeal or laryngeal masses. Or, if patients had poor dentition, symptomatic gastro‐oesophageal reflux, cervical spine instability, unstable hypertension, coronary artery disease, cerebral disease, lack of resources available to conduct the procedure on scheduled date of surgery)

Baseline characteristics (taken from unpublished data):

Intubation with GlideScope

Age: 56.5 (SD ± 11.6)

Gender (M/F): 11/13

Height (cm): 165.3 (SD ± 12.1)

Weight (kg): 79.9 (SD ± 15.1)

BMI (kg/m²): 29.2 (SD ± 4.6)

Mallampati ≥ 3: 24

Intubation with Macintosh

Age: 54.0 (SD ± 11.2)

Gender (M/F): 12/8

Height (cm): 167.0 (SD ± 8.6)

Weight (kg): 74.7 (SD ± 13.4)

BMI (kg/m²): 26.8 (SD ± 4.3)

Mallampati ≥ 3: 20

Country: Toronto, Ohio, USA

Setting: hospital

Interventions

GlideScope (n = 24) vs Macintosh (n = 20)

Outcomes

Continuous outcomes:

Time for tracheal intubation: defined as time from when laryngoscope passed between the participant's teeth to when laryngoscopy enabled placement of a styletted tracheal tube at, not through, laryngeal inlet. Results reported as median (IQR) seconds: GlideScope 30 (22‐47); Macintosh 18 (14‐28)

Dichotomous outcomes:

Failed intubation: defined as when laryngoscope was withdrawn beyond the teeth or lasting longer than 60 seconds

Notes

Experience of intubator: laryngoscopists experienced in both devices on ≥ 25 occasions (from unpublished manuscript)

Funding/declarations of interest: none apparent

Comments: study authors provided unpublished manuscript of study on email request. Data above and in risk of bias table were taken from this manuscript.

Study of forces, includes relevant outcomes

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: computer‐generated randomization code

Allocation concealment (selection bias)

Unclear risk

Comment: randomization revealed immediately before induction of anaesthesia (but no other details on how it was concealed)

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: outcome assessors and data analysts blinded to forces outcome but this outcome not relevant for this review. Assumed other outcome assessments were not blinded

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: few losses after randomization due to study equipment failure, but data still collected for all outcomes when possible

Selective reporting (reporting bias)

Low risk

Comment: copy of protocol on clinicaltrials.gov sought and compared with published trial (clinical trials ID NCT01814176). All outcomes were reported

Experience of intubator

Low risk

Comment: laryngoscopists experienced in both devices, with use of GlideScope on at least ≥ 25 occasions

Baseline characteristics

Low risk

Comment: baseline characteristics comparable

Funding sources

Low risk

Comment: none apparent

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 59

Inclusion criteria: 40 to 60 years of age, untreated hypertension, undergoing elective surgery

Exclusion criteria: blood pressure > 180/110 mmHg, predicted difficult airway, history of drug abuse, dehydration, history of other cardiovascular disease, history of consumption of any drugs known to affect cardiovascular system, diabetes mellitus, end‐organ damage due to hypertension

Baseline characteristics:

GlideScope

Age: 54.82 (SD ± 5.76)

Gender (M/F): 19/11

Weight (kg): 72.14 (SD ± 9.72)

Macintosh

Age: 57.82 (SD ± 4.83)

Gender (M/F): 15/14

Weight (kg): 66.25 (SD ± 6.15)

Country: Iran

Setting: hospital

Interventions

GlideScope (n = 30) vs Macintosh (n = 29)

Outcomes

Continuous outcomes:

Time for tracheal intubation: defined as time from grasping endotracheal tube until passing tube through vocal cords

Notes

Experience of intubator: all intubations performed by 1 experienced anaesthesiology resident

Funding/declarations of interest: none apparent

Additional: Study aimed to assess haemodynamic changes but included relevant outcomes

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: randomized using permutated blocks

Allocation concealment (selection bias)

Unclear risk

Comment: no details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: not possible to blind outcome assessor for relevant outcome

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: only 1 exclusion; not likely to affect outcome data

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Unclear risk

Quote: "The patients were intubated by a single experienced anesthesiology resident"

Comment: no details on whether experience is equivalent with both devices

Baseline characteristics

Low risk

Comment: baseline characteristics comparable

Funding sources

Low risk

Comment: none apparent

Study characteristics

Methods

Randomized controlled trial

Cross‐over

Participants

Total number of participants: 203

Inclusion criteria: scheduled for elective surgery

Exclusion criteria: pathology of the neck, upper respiratory tract or upper alimentary tracts, at risk of pulmonary aspiration of gastric contents

Total baseline characteristics:

Age: mean 57 (SD ± 16) (range 18–86)

Gender M/F: 117/86

Height (cm): mean 160 (SD ± 9) (range 130–181)

Weight (kg): mean 61 (SD ± 12) (range 34–105)

BMI: mean 24 (SD ± 3.9) (range 16–37)

ASA I: 62

ASA II: 140

ASA III: 1

Mallampati 1: 154

Mallampati 2: 40

Mallampati 3: 8

Mallampati 4: 1

Country: Japan

Setting: hospital

Participant's head and neck stabilized by assistants using in‐line manual method

Interventions

Pentax AWS vs Macintosh

Macintosh blade #3 or #4. Use of gum‐elastic bougie allowed in Macintosh group

Outcomes

Continuous outcomes:

Improved visualization

Time for tracheal intubation (for Macintosh, time from tracheal tube passing gap between upper and lower incisors to confirmation of carbon dioxide waveforms after tracheal intubation; for Pentax, time from touching tracheal tube (attached to scope) to confirmation of carbon dioxide waveforms)

Dichotomous outcomes:

Failed intubation: defined as not complete within 120 seconds, then tried with another device. Some inconsistencies within study report with denominator figures for successful tracheal intubation.

CL glottic view: 1 to 4

Notes

Funding/declarations of interest: 1 study author given an honorarium from manufacturer for writing a lecture and was loaned an AWS for the study. Other departments had to provide their own

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "The order was randomized by tossing a coin"

Allocation concealment (selection bias)

Unclear risk

Comment: no details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetists

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: no blinding possible

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no loss of participants

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Unclear risk

Comment: no details of operator experience

Baseline characteristics

Unclear risk

Comment: not divided by group, as cross‐over design

Funding sources

High risk

Comment: one study author given an honorarium from manufacturer for writing a lecture and was loaned an AWS for the study. Other departments had to provide their own

Study characteristics

Methods

Randomized controlled trial

Parallel design

Participants

Total number of participants: 60

Inclusion criteria: ASA I to III, scheduled for elective surgical procedure requiring tracheal intubation

Exclusion criteria: no details

Baseline characteristics not included in abstract

Country: Ireland

Setting: hospital

Interventions

McGrath vs Macintosh

Type of McGrath not specified in the paper

Optimization manoeuvres used in both groups as required (readjustment of head, use of bougie, use of external laryngeal manipulation and use of second assistant)

Outcomes

Continuous outcomes:

Tme for tracheal intubation (reported in study without SD)

Difficulty of intubation

Dichotomous outcomes:

Successful first attempt

Larngeal/airway trauma (dental trauma)

CL glottic view: 1 to 3

Number of attempts: 1 to 3

Notes

Experience of intubator: experience with McGrath on ≥ 5 occasions. Ten anaesthetists in total. Does not say if stratified

Funding/declarations of interest: 1 McGrath VLS on loan from manufacturer

Other: published only as an abstract

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Comment: participants described as "randomly assigned", but no additional details

Allocation concealment (selection bias)

Unclear risk

Comment: no details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Quote: "All data were collected by an independent unblinded observer"

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no apparent losses

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Unclear risk

Quote: "Ten anaesthetists, who had received prior instruction and had experienced use of the McGrath videolaryngoscope on at least five previous occasions"

Comment: unclear if this is sufficient equivalent experience

Baseline characteristics

Low risk

Quote: "There were no significant differences in baseline characteristics between the groups"

Funding sources

Unclear risk

Comment: 1 McGrath VLS on loan from manufacturer

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 40

Inclusion criteria: over 16 years of age requiring urgent tracheal intubation in the critical care unit

Exclusion criteria: requirement for immediate endotracheal intubation (within 5 minutes) as anticipated by the ICU team, spontaneous breathing endotracheal intubation technique or cervical spine precautions, history of (or anticipated) difficult intubation, previous cardiac arrest or cardiopulmonary instability (oxygen saturation 90% or systolic blood pressure 80 mmHg despite oxygen or fluid and vasopressor therapy), prior clinical deterioration requiring immediate tracheal intubation while awaiting randomization or deemed inappropriate for enrolment by the attending physician (e.g. patient considered unsuitable for either technique)

Baseline characteristics:

GlideScope

Age: 68 (SD ± 16)

Gender M/F: 15/5

BMI: 26 (SD ± 4)

Mallampati 1: 5

Mallampati 2: 6

Mallampati 3: 2

Mallampati 4: 1

Macintosh

Age: 61 (SD ± 16)

Gender M/F: 13/7

BMI: 24 (SD ± 6)

Mallampati 1: 3

Mallampati 2: 4

Mallampati 3: 3

Mallampati 4: 0

Note: 16 participants were not tested for their Mallampati score.

Country: Canada

Setting: hospital, ICU or emergency department

Interventions

GlideScope (n = 20) vs Macintosh (n = 20)

GlideScope blade #4; site of intubation ICU (19), ward (1), ED (0)

Macintosh blade #3 or #4; site of intubation ICU (14), ward (3), ED (3)

Outcomes

Continuous outcome:

Time for tracheal intubation: defined as time from when tip of laryngoscope entered the participant's mouth until detection of end‐tidal carbon dioxide waveform on capnography)

Dichotomous outcomes:

Failed intubation (unsuccessful on first attempt and required use of alternative device). Data presented for failure of first attempts. Not possible to combine data with those of other studies. In the GlideScope group, 5 of 12 (42%) first attempts failed, resulting in use of the Macintosh for subsequent attempts. In the Macintosh group, only 1 of 13 (5%) first attempts failed, resultingin use of the GlideScope for subsequent attempts (P = 0.03). The supervisor took over in 8 of 12 (67%) failed first attempts with Macintosh (data missing from 1 participant) compared with 4 of 12 (33%) in the GlideScope group (P = 0.22).

Mortality (30 days)

Successful first attempt

CL glottic view: 1 to 4 (results reported for 19 participants only)

No. of attempts: 1 to 4

Time for successful intubation, median (IQR): GlideScope 221 (103‐291), Mac 156 (67‐220), P = 0.15

Notes

Experience of intubator: all inexperienced in endotracheal intubation, defined as fewer than 5 endotracheal intubations in the preceding 6 months (medical students, or PGY 1‐4) Supervisor could take over if initial attempt exceeded 1 minute.

Funding/declarations of interest: Canadian Anesthesiologists' Society 2009 Research Award; Clinician Scientist Award from Vancouver Coastal Health Research Institute

Additional: pilot study

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: random allocation table in permutated blocks of 4

Allocation concealment (selection bias)

Low risk

Comment: numbered opaque sealed envelopes opened by research co‐ordinator at time of randomization

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetists

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: research co‐ordinators not blinded

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: data for CL scores not reported for 1 participant in each group

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Low risk

Comment: both groups included inexperienced operators

Baseline characteristics

Low risk

Comment: baseline characteristics comparable

Funding sources

Low risk

Comment: Canadian Anesthesiologists' Society 2009 Research Award; Clinician Scientist Award from Vancouver Coastal Health Research Institute

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 120

Inclusion criteria: 18 to 65 years of age, either gender, ASA I or II undergoing elective cervical spine surgery for cervical compressive myelopathy

Exclusion criteria: risk factors for difficult mask ventilation, gastric aspiration (obesity, pregnancy), difficult airway such as previous neck surgery and mouth opening < 3 cm

Baseline characteristics:

C‐MAC + stylet

Age: 40 (SD ± 12)

Gender M/F: 25/5

BMI: 23.1 (SD ± 2.6)

ASA I: 22

ASA II: 8

Mallampati 1: 4

Mallampati 2: 14

Mallampati 3: 12

Macintosh + stylet

Age: 39 (SD ± 16)

Gender M/F: 26/4

BMI: 21.6 (SD ± 2.1)

ASA I: 21

ASA II: 9

Mallampati 1: 6

Mallampati 2: 11

Mallampati 3: 13

C‐MAC non‐stylet

Age: 39 (SD 16)

Gender M/F: 24/6

BMI: 21.6 (SD 2.7)

ASA I: 23

ASA II: 7

Mallampati 1: 6

Mallampati 2: 15

Mallampati 3: 9

Macintosh non‐stylet

Age: 41 (SD 16)

Gender M/F: 28/2

BMI: 22.0 (SD 2.4)

ASA I: 25

ASA II: 5

Mallampati 1: 4

Mallampati 2: 15

Mallampati 3: 11

Country: India

Setting: hospital

Interventions

C‐MAC with stylet (n = 30) vs Macintosh with stylet (n = 30) vs C‐MAC non‐stylet (n = 30) vs Macintosh non‐stylet (n = 30)

Gum‐elastic bougies used if required

Additional: The neck of all participants was immobilized with MILS by holding the sides of the neck and the mastoid processes, thus preventing flexion/extension or rotational movements of the head and neck.

Outcomes

Continuous outcomes:

Difficulty of tracheal intubation: measured on IDS; reported as median (IQR): C‐MAC + stylet 2 (1‐3); Macintosh + stylet 3 (2‐4); C‐MAC non‐stylet 4 (2‐6); Macintosh non‐stylet 3 (2‐8)

Time for tracheal intubation: defined as time from insertion of laryngoscope blade between the teeth until ETT was placed through the vocal cords, as evidenced by visual confirmation; reported as median (IQR): C‐MAC + stylet 27 (23‐31); Macintosh + stylet 34 (22‐53); C‐MAC non‐stylet 52 (28‐76); Macintosh non‐stylet 34 (22‐70)

Dichotomous outcomes:

Failed intubation: defined as an attempt in which the trachea was not intubated, or that required longer than 120 seconds to perform

Laryngeal/airway trauma (upper lip trauma, tooth damage, soft tissue bleeding, supraglottic trauma)

Successful first attempt

CL glottic view: 1 to 3

No. of attempts: 1 to 2

Notes

Experience of intubator: 1 of 2 anaesthesiologists experienced in the use of both laryngoscopes in patients requiring MILS, having done > 50 intubations with each device before the study

Funding/declarations of interest: none apparent

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Quote: "computer‐generated randomization"

Allocation concealment (selection bias)

Unclear risk

Comment: no details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetists

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Quote: "Data were collected by a single independent observer"

Comment: not possible for all outcomes to be blinded;unclear if independent observer is blinded

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Quote: "Four patients were excluded because of alternative intubation techniques preferred by the attending anesthesiologist"

Comment: small number excluded prior to randomization

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Low risk

Quote: "two anesthesiologists...experienced in the use of both laryngoscopes in patients requiring MILS, having done more than 50 such intubations with each device before this study"

Baseline characteristics

Low risk

Comment: baseline characteristics comparable

Funding sources

Low risk

Comment: none apparent

Study characteristics

Methods

Randomized controlled trial

Cross‐over design ‐ participants intubated with both types of scopes in random order

Participants

Total number of participants: 14

Inclusion criteria: adults undergoing elective surgery requiring general anaesthesia and oral endotracheal intubation, patients who were likely to be easy to intubate, Mallampati airway class 1 or 2, thyromental distance ≥ 6.0 cm, sternomental distance ≥ 12.5 cm, age 18 to 80 years, height between 1.52 and 1.83 m, BMI ≤ 30 kg/m²

Exclusion criteria: maxillary incisors that were loose or in poor condition; previous difficult intubation; any cervical spine anatomical abnormalities such as disc disease, instability, myelopathy and/or any previous cervical spine surgery; symptomatic gastro‐oesophageal reflux or reactive airway disease; any history of coronary artery disease or cerebral aneurysm; any history of vocal cord and/or glottic disease or dysfunction; preoperative systolic blood pressure > 180 mmHg or diastolic blood pressure > 80 mmHg; ASA > III

Baseline characteristics: reported for all participants, not by group

Age: 47 (SD ± 20)

Gender M/F: 9/5

BMI: 25.9 (SD ± 2.6)

ASA I: 3

ASA II: 11

Mallampati 1: 8

Mallampati 2: 6

Country: USA

Setting: hospital

Interventions

Airtraq vs Macintosh

Airtraq used with video camera attachment

Outcomes

Continuous outcomes:

Time for tracheal intubation (definition not given): not included in meta‐analysis but study authors report results as mean (± SD): Airtraq 19.6 (± 7.0); Macintosh 21.6 (± 7.8)

Dichotomous outcomes:

Success of intubation (not included in meta‐analysis because of increased risk of bias due to study design, but study authors report that all intubations were successful except for 1 in a participant intubated with a Macintosh blade)

Glottic view (POGO scores: "POGO scores at stage 3 were less during intubations with the Macintosh than with Airtraq, based on both anaesthesiologist report (P = 0.0007) and video analysis (P = 0.0002)")

Adverse effects, but not reported by group. "On postoperative day 7, two patients reported very mild voice changes that were intermittent and nonbothersome"

Notes

Experience of intubator: 2 study anaesthesiologists, both with more than 27 years' experience of direct laryngoscopy and ≥ 50 successful intubations with Airtraq

Funding/declarations of interest: supported by a National Institutes of Health grant

Additional: study designed to measure forces but includes relevant outcomes for this review

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: use of an independent biostatistician to develop randomization sequence

Allocation concealment (selection bias)

Low risk

Comment: use of sealed opaque envelopes with matching patient identification number

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: not possible to blind outcome assessors to relevant outcomes

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: only 1 loss; reasons for loss reported

Selective reporting (reporting bias)

Low risk

Comment: registered with clinicaltrials.gov NCT01369381; protocol sourced and appears equivalent to full published report

Experience of intubator

Low risk

Comment: 2 study anaesthesiologists, each with more than 27 years' experience of direct laryngoscopy and ≥ 50 successful intubations with Airtraq

Baseline characteristics

Unclear risk

Comment: more women than men enrolled in the study; unclear if this affects results. All participants underwent laryngoscopy with each scope; therefore baseline characteristics were not presented separately

Funding sources

Low risk

Comment: supported by a National Institutes of Health grant

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 200

Inclusion criteria: ASA I or II undergoing general anaesthesia using tracheal intubation

Exclusion criteria: history of previous difficult intubation, cervical spine fracture or cervical spine instability

Baseline characteristics:

Baseline characteristics not sufficiently supplied in short report. Author quote: "Patients were comparable with respect to age, weight and height"

Country: Japan

Setting: hospital

Interventions

Pentax AWS (n = 100) vs Macintosh (n = 100)

Outcomes

Continuous outcome:

Time for tracheal intubation

Dichotomous outcomes:

Successful first attempt

No. of attempts: 1 to 3

Notes

Experience of intubator: 26 non‐anaesthesia residents, with median clinical training of 5 weeks (range 1‐24 weeks)

Funding/declarations of interest: none

Additional: limited detail ‐ short report only

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Comment: computer random number table

Allocation concealment (selection bias)

Unclear risk

Comment: no details

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Quote: "an independent observer recorded the duration of tracheal intubation attempts"

Comment: independent but not blinded

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no losses reported

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

Low risk

Comment: 26 residents, all with equivalent limited experience

Baseline characteristics

Low risk

Comment: described by study authors as comparable

Funding sources

Low risk

Comment: none

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 521

Inclusion criteria: required general anaesthesia with tracheal intubation for surgery

Exclusion criteria: history of previous difficult intubation, cervical spine fracture or cervical spine instability

Baseline characteristics:

Pentax AWS

Age: 53 (SD ± 16)

Height (cm): 159 (SD ± 9)

Weight (kg): 59 (SD ± 12)

BMI: 23 (SD ± 4)

Macintosh

Age: 54 (SD ± 17)

Height (cm): 159 (SD ± 9)

Weight (kg): 59 (SD ± 11)

BMI: 23 (SD ± 4)

Country: Japan

Setting: hospital

Interventions

Pentax AWS (n = 265) vs Macintosh (n = 256)

Outcomes

Continuous outcomes:

Time for tracheal intubation: defined as time from interruption of intermittent positive‐pressure ventilation to connection of the endotracheal tube to an anaesthesia circuit. If the first intubation attempt failed, duration of the subsequent attempt was added to time of the first attempt to secure the airway.

Dichotomous outcomes:

Successful first attempt

No. of attempts: 1 to 4

Notes

Experience of intubator: all medical residents with anaesthesia training of 9 (SD 6) weeks, 48 operators in total, supervised by anaesthesiologist, available for verbal information if necessary

Funding/declarations of interest: departmental funding only

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Quote: "randomly assigned via table of random numbers as generated by a personal computer"

Comment: However, study authors also state: "availability of the Pentax‐AWS was slightly limited compared with the standard Macintosh laryngoscope." Unclear if this may have introduced bias

Allocation concealment (selection bias)

Unclear risk

Comment: no details given

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: all outcomes were assessed during intubation process; therefore not blinded

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no apparent losses

Selective reporting (reporting bias)

Unclear risk

Comment: published protocol not sought

Experience of intubator

High risk

Quote: "each participant had taken part in a smaller number of intubations with the Pentax‐AWS than the Macintosh laryngoscope"

Comment: all operators had limited experience

Baseline characteristics

Low risk

Comment: baseline characteristics equivalent

Funding sources

Low risk

Comment: departmental funding only

Study characteristics

Methods

Randomized controlled trial

Parallel group

Participants

Total number of participants: 60

Inclusion criteria: adult patients, ASA I or II, requiring a DLT for thoracic surgery

Exclusion criteria: risk of regurgitation and pulmonary aspiration, history of gastro‐oesophageal reflux, pregnancy, scheduled tracheostomy and planned postoperative ventilation in ICU, a potentially difficult laryngoscopy as suggested by limited neck extension (< 35°), distance between tip of the patient’s mandible and thyroid notch < 7 cm, sternomental distance < 12.5 cm with the head fully extended and the mouth closed

Baseline characteristics:

GlideScope

Age: 40.1 (SD ± 18.7)

Gender M/F: 7/23

Height (cm): 168 (SD ± 6.8)

Weight (kg): 60.1 (SD ± 9.5)

BMI: 21.3 (± 3.4)

ASA I: 14

ASA II: 16

Mallampati 1: 1

Mallampati 2: 27

Mallampati 3: 2

Macintosh

Age: 37.2 (SD ± 15.4)

Gender M/F: 11/19

Height (cm): 165.6 (SD ± 8.4)

Weight (kg): 62. 4 (SD ± 12)

BMI: 23.0 (± 5.6)

ASA I: 12

ASA II: 18

Mallampati 1: 3

Mallampati 2: 27

Mallampati 3: 0

Country: Taiwan

Setting: hospital

Interventions

GlideScope (n = 30) vs Macintosh (n = 30)

BURP manoeuvre used when required

Use of double‐lumen tubes for all participants

Outcomes

Continuous outcome:

Time of intubation (time of DLT insertion calculated from time when the laryngoscope passed between participant's lips until 3 complete cycles of end‐tidal carbon dioxide displayed on the capnograph)

Dichotomous outcomes:

Laryngeal/airway trauma (blood on the device or oral bleeding)

Patient‐reported sore throat (combined data for mild/moderate/severe classifications). Hoarseness data also presented but not reported in this review

Successful first attempt

No. of attempts: 1 to 3 or more

Notes

Experience of intubator: 2 experienced anaesthetists with experience of ≥ 300 tracheal intubations with each device

Funding/declarations of interest: none

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Quote: "Patients were randomly assigned"

Comment: no mention of method

Allocation concealment (selection bias)

Unclear risk

Quote: "opening a sealed envelope"

Comment: no mention if opaque

Blinding of participants and personnel (performance bias)
All outcomes

High risk

Comment: not possible to blind anaesthetist

Blinding of outcome assessment (detection bias)
All outcomes

High risk

Comment: some outcomes were assessed by an independent observer, but study authors did not state whether this person was blinded. For theatre outcomes, assumed the assessor was not blinded

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Comment: no apparent losses

Selective reporting (reporting bias)

Low risk

Comment: clinical trial register protocol sourced (unique identifier: NCT 014249605). Protocol outcomes comparable with study‐reported outcomes

Experience of intubator

Low risk

Quote: "two experienced anaesthesiologists with experience of at least 300 tracheal intubations with each device"

Baseline characteristics

Unclear risk

Comment: more men in Macintosh group. Impact of this difference is uncertain

Funding sources

Low risk

Comment: none

Study characteristics

Methods

Randomized controlled trial

Cross‐over design

Participants

Total number of participants: 128

Inclusion criteria: age > 18 years, ASA I to III, full upper dentition at front

Exclusion criteria: requiring awake fibreoptic intubation, with known laryngeal pathology or at risk of pulmonary aspiration

Baseline characteristics: reported according to device with which participants were intubated

McGrath Series 5

Age: 42.3 (SD ± 14.0)

Gender M/F: 35/29

BMI: 28.5 (SD ± 5.0)

ASA I: 21

ASA II: 37

ASA III: 6

Mallampati 1: 30

Mallampati 2: 26

Mallampati 3: 7

Mallampati 4: 1

Macintosh

Age: 42.5 (SD ± 13.1)

Gender M/F: 25/39

BMI: 27.9 (SD ± 6.0)

ASA I: 23

ASA II: 39

ASA III: 2

Mallampati 1: 24

Mallampati 2: 34

Mallampati 3: 6

Mallampati 4: 0

Country: Australia

Setting: hospital

Interventions

McGrath Series 5 (n = 64) vs Macintosh (n = 64)

Alternative device was used initially to record laryngoscopic view, then was removed. Device to which participants were randomized was then used to re‐record laryngoscopic view, then intubation was performed

Outcomes

Continuous outcomes:

Time of intubation: defined as time from when laryngoscope entered the mouth until first capnographic square wave

Intubation difficulty score: reported as median (IQR (range)): McGrath 0 (0‐3 (0‐7)); Macintosh 2 (0‐3 (0‐7)); P = 0.0024

Dichotomous outcomes:

Failed intubation

Sore throat/hoarseness

Laryngeal/airway trauma (dental damage, blood on blade, mucosal laceration, other airway trauma)

CL glottic view: reported as differences between intubations with each device. Study authors state that view was worse when Macintosh was used as opposed to McGrath laryngoscope

Notes

Experience of intubator: experienced anaesthetists; all were "clinically familiar with both devices and had undergone training in the use of the McGrath Series 5 before the start of the trial"

Funding/declarations of interest: no external funding received

Additional: manual in‐line stabilization performed on all participants

Risk of bias