Oscillating devices for airway clearance in people with cystic fibrosis
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To identify whether oscillatory devices, oral or chest wall, are effective for mucociliary clearance and whether they are equivalent or superior to other forms of airway clearance in the successful management of secretions in people with CF.
Background
Cystic fibrosis (CF) is a common inherited life‐limiting genetic disorder. The genetic defect causes mucus hypersecretion within the airways leading to airway obstruction and mucus plugging (Zach 1990). Airway damage and progressive loss of respiratory function is a consequence of persistent infection and inflammation within the lungs (Cantin 1995; Konstan 1997). Respiratory infections are the primary cause of morbidity and mortality in CF and therefore chest physiotherapy is considered to be an important treatment for the assistance and clearance of the sticky mucus found within the airways of people with CF.
Chest physiotherapy is currently implemented at initial diagnosis and, dependent on the age of the individual, will traditionally take the form of manual therapies. Conventional manual therapies would require the assistance of another person to perform the techniques of percussion and vibrations, with the addition of postural drainage when this was felt to add to the technique. With the advent of a more modern approach to physiotherapy, more self‐administered techniques are being used. These self‐administered techniques do not necessitate postural drainage or indeed the assistance of another person. They can be done in a sitting position (if preferred) and use different methods of breathing or different devices to assist mucus clearance. It is recommended that chest physiotherapy should be carried out for the maintenance of a clear chest with an additional recognition for altered or more aggressive therapies during times of respiratory exacerbation.
Other Cochrane Reviews have considered the benefits of different forms of chest physiotherapy in people with CF and have presented mixed results (Elkins 2006; Main 2005). They do not compare oscillatory devices with any other therapies apart from conventional chest physiotherapy (Main 2005) or positive expiratory pressure (PEP) (Elkins 2006). It is the intention of this review to complement the information previously provided. This review will examine the effect and acceptability of oscillatory devices when compared to other techniques currently used for airway clearance.
Objectives
To identify whether oscillatory devices, oral or chest wall, are effective for mucociliary clearance and whether they are equivalent or superior to other forms of airway clearance in the successful management of secretions in people with CF.
Methods
Criteria for considering studies for this review
Types of studies
Randomised controlled trials (RCTs) and controlled clinical trials (CCTs).
Types of participants
Children (aged up to 16 years) and adults (16 years and above) with any degree of disease severity, with defined CF, diagnosed clinically and by sweat or genetic testing. Trials with participants enrolled during a period of stability or during a pulmonary exacerbation will both be considered.
Types of interventions
Oscillatory devices, both oral and chest wall, for airway clearance compared with another recognised airway clearance technique either as a single technique (e.g. oscillation versus active cycle of breathing technique (ACBT)) or in conjunction with another recognised airway clearance technique (e.g. oscillation and ACBT versus ACBT alone).
Interventions of variable duration will be considered and separated according to term of intervention. Single dose interventions will not be considered.
Specific techniques considered for comparison are likely to fall in to one of the following categories:
(1) Oscillatory devices
Devices which have an oscillatory component consider intra‐ and extra‐thoracic oscillations.
Intra‐thoracic oscillations are generated orally and created using variable resistances within the airways generating controlled oscillating positive pressure which mobilises respiratory secretions. When the oscillation frequency approximates the resonance frequency of the pulmonary system, endobronchial pressure oscillations are amplified and result in vibrations of the airways. These vibrations loosen mucus from the airway walls. The intermittent increases in endobronchial pressure reduce the collapsibility of the airways during exhalation, increasing the likelihood of clearing mucus from the tracheobronchial tract. The airflow accelerations increase the velocity of the air being exhaled, facilitating the movement of mucus up the airways (Konstan 1994). Exhalation through these devices generates both oscillations of positive pressure in the airways and repeated accelerations of expiratory airflow that have been shown to result in improved sputum clearance (Rogers 2005).
The devices frequently employed for this purpose are:
(a) Flutter
A small plastic device containing a large ball bearing which repeatedly interrupts the outward flow of air (Konstan 1994; Pryor 1999).
(b) Acapella
A flow operated oscillatory PEP device, which uses a counterweighted plug and magnet to generate the oscillatory resistance (Volsko 2003).
(c) Cornet
A horn shaped tube which houses a rubber inner tube. The degree of rotation of this inner tube reflects the resistance generated. As the individual exhales through the horn the inner tube unfurls generating a rhythmic bending and unbending of the inner tube within the horn throughout the expiration phase (Pryor 1999).
(d) Intrapulmonary percussive ventilation (IPV)
This provides continuous oscillation to the airways via the mouth (Homnick 1995).
Extra‐thoracic oscillations are generated by forces external to the respiratory system, for example high frequency chest wall oscillation (HFCWO) (Warwick 1991). External chest wall oscillations are applied using an inflatable vest attached to a machine which vibrates at a variable frequencies and intensities as set by the operator to ensure the individual's comfort and associated concordance. This type of device can also be called the Vest or Hayek Oscillator.
(2) Positive expiratory pressure (PEP)
Positive expiratory pressure is another well‐recognised and well‐utilised clearance method. Devices can be used to open up and recruit obstructed lung, allowing air to move behind secretions and assist in mobilising them. Breathing out against a slight resistance (10 to 20 cmH2O) prevents the smaller bronchial tubes from collapsing down and thus permits the continuing upward movement of any secretions (Elkins 2006). Masks, mouthpieces or a more novel Bubble PEP system offer more choice when considering this approach.
Hi‐PEP is a modification of PEP which involves the full forced expiration against a fixed mechanical resistance usually between 80 to 140 cmH2O.
(3) Breathing techniques
When the individual is considered to be moving toward independence and chooses not to use a device, the techniques frequently adopted are autogenic drainage (AD) and the ACBT.
(a) Autogenic drainage
This term describes a series of breathing exercises devised by the Belgian physiotherapist Jean Chevaillier. The aim is to dislodge and collect mucus from the lungs and then clear these secretions by breathing at various lung volumes (Chevaillier 1984; Schöni 1989). There are three phases ‐ the Unstick, Collect and Evacuate when breathing at low, mid and high lung volumes to mobilise, collect and expectorate secretions respectively.
(b) Active cycle of breathing technique (Pryor 1999; Webber 1986; Webber 1990)
This consists of three breathing techniques: breathing control is used between other techniques to allow relaxation; thoracic (chest) expansion exercises with the emphasis on inspiration, expiration being quiet and relaxed; and the forced expiration technique or huff is used to mobilise and clear secretions. One or two forced expirations are combined with a period of breathing control. A huff from high lung volume (when a breath has been taken in) will clear secretions from the upper airways and a huff from mid to low lung volume will clear secretions from the lower more peripheral airways.
(4) Conventional chest physiotherapy
Conventional therapy techniques are likely to have been introduced in infancy, or when the initial diagnosis was made in childhood, and may also include huffing and directed cough (Main 2005). If the diagnosis of CF was made during adolescence or indeed adulthood, many people prefer to use techniques which enable independence from an operator and which can easily be fitted around an active lifestyle.
(5) Exercise
Where an individual with CF has few respiratory symptoms, exercise can often be the treatment of choice as a means of airway clearance or as an adjunct to other techniques. It has been recognised as contributing to enhanced quality of life and improvements in functional exercise tolerance in people with chronic respiratory diseases such as CF. In addition exercise has been shown to increase respiratory muscle endurance, increase sputum expectoration and preserve respiratory function in some individuals with CF, where a higher level of aerobic fitness also correlated with a decreased risk of mortality (Bradley 2002; Webb 1995).
Types of outcome measures
Primary outcome
(1) Respiratory function
(a) forced expiratory volume at one second (FEV1)
(b) mid expiratory flow (FEF25‐75 )
(c) forced vital capacity (FVC)
(d) expiratory reserve volume (ERV) or reserve volume (RV)
Secondary outcom es
(1) Sputum
(a) volume
(b) weight (dry or wet)
(2) Exercise tolerance (as measured by recognised standard exercise tests e.g. walk tests, step tests or cycle ergometry)
(3) Quality of life (QOL) indices, e.g. CF QOL questionnaire
(4) Level of oxygen saturation in response to treatment
(5) Frequency of exacerbations (as defined by Rosenfeld (Rosenfeld 2001)) as a consequence of the treatment intervention
(6) Participant reported satisfaction with treatment intervention
(7) Lung clearance index
We plan to group outcome data those measured at one, three, six, twelve months and annually thereafter. If outcome data is recorded at other time periods, then consideration will be given to examining these as well.
Search methods for identification of studies
We will identify relevant trials from the Group's Cystic Fibrosis Trials Register.
The Cystic Fibrosis Trials Register is compiled from electronic searches of the Cochrane Central Register of Controlled Trials (Clinical Trials) (updated each new issue of The Cochrane Library), quarterly searches of MEDLINE, a search of EMBASE to 1995 and the prospective handsearching of two journals ‐ Pediatric Pulmonology and the Journal of Cystic Fibrosis. Unpublished work is identified by searching the abstract books of three major cystic fibrosis conferences: the International Cystic Fibrosis Conference; the European Cystic Fibrosis Conference and the North American Cystic Fibrosis Conference. For full details of all searching activities for the register, please see the relevant sections of the Cystic Fibrosis and Genetic Disorders Group Module.
Data collection and analysis
Two authors (LM and JA) will independently review all citations and abstracts identified by the search to determine which papers assessed should be included. If disagreement occurs the authors will seek resolution by consensus.
Assessment of studies
The two authors will independently assess the methodological rigour and quality of selected studies using the following criteria on quality assessment described by Jüni (Jüni 2001).
(1) Generation of allocation sequence
We will consider this as adequate if a computer algorithm or a similar process based on chance is used to randomise participants to treatment groups. We will identify this as inadequate if sequences which could be attributed to prognosis, degree of disease severity, age etc are employed. We will consider this unclear where the generation of allocation sequence has not been identified.
(2) Concealment of allocation
We will consider concealment of allocation adequate where it was not possible for the investigators to foresee the allocation of participants to a particular treatment group, for example centralised or pharmacy‐controlled randomisation, pre‐numbered or coded identical containers administered serially to participants, on‐site locked computer system, or sequentially numbered, sealed , opaque envelopes. We will consider the concealment of allocation inadequate if the investigator was able to predict the allocation, for example, alternation; the use of case record numbers, dates of birth or day of the week. We will grade this as unclear if the concealment of allocation has not been described.
(3) Blinding
We will report on the degree of blinding employed in each study. Given the treatment interventions and the specific devices for chest clearance which we will consider in this review blinding of the investigator and participants will not be possible: however, blinding of the person analysing the data is possible.
(4) Intention‐to‐treat analysis
We will report on whether the original investigators employed an intention‐to‐treat analysis (analysis based on the initial treatment allocation, not on the treatment eventually administered). We will assess whether the numbers and reasons for dropouts and withdrawals in all intervention groups are described or whether it is specified that there were no dropouts or withdrawals.
Data Extraction
Both authors LM and JA will independently perform data extraction and record data on a form developed for this purpose.
Data Analysis
For binary outcome measures, we plan to seek data on the number of participants with each outcome event, by allocated treated group, irrespective of compliance and whether or not the individual was later thought to be ineligible or otherwise excluded from treatment or follow up. We aim to calculate a pooled estimate of the treatment effect for each outcome across studies using relative risk where appropriate.
For continuous outcomes, we plan to record either mean relative change from baseline for each group or mean post‐treatment or intervention values and their standard deviations (these will be presented separately). If standard errors are reported, we will calculate the standard deviations if possible. We will calculate a pooled estimate of treatment effect by calculating the weighted mean difference.
When conducting a meta‐analysis combining results from cross‐over trials we plan to use the methods recommended by Elbourne (Elbourne 2002). However, if only limited data are available, we may only be able to either use the first arm data only or to treat the cross‐over trials as if they are parallel trials. Elbourne states that this approach will produce conservative results as it does not take into account within‐patient correlation (Elbourne 2002). Also each participant will appear in both the treatment and control group, so the two groups will not be independent.
We will consider trials identifying interventions of varying duration separately; we will consider those of 1 to 12 weeks as short term; those over 12 to 24 weeks medium term; and those over 24 weeks considered long term. We will not consider single‐dose interventions as it is unlikely that an individual can be instructed in the appropriate usage of such devices or treatment techniques in a single session.
Heterogeneity and I 2 test (Higgins 2003)
The greater the consistency between the primary studies in a meta‐analysis, the more generalisable are the results. Heterogeneity refers to the genuine differences between studies rather than those that occur by chance. We will test for heterogeneity using the I2 statistic (Higgins 2003). This is a measure of consistency of results across studies, where values range from 0% to 100%. We plan to use a simplified categorization of heterogeneity such that we consider heterogeneity to be low if the I2 value is up to 25%, moderate up to 50% and high up to 75% . If we identify moderate or high degrees of heterogeneity and sufficient studies are included in the review, we plan to investigate this by performing sub‐group and sensitivity analyses.
Sub‐group and sensitivity analysis
We plan to investigate heterogeneity through subgroup analysis of the following:
(1) children (up to 16 years) compared to adults
(2) different treatment regimens and concomitant medications
We also plan to perform the following sensitivity analyses to assess how robust the results of our meta‐analysis are:
(1) study quality i.e. RCT compared to CCT
(2) differing baseline characteristics of studies (specifically disease severity as measured by FEV1 and defined as severely (FEV1 <45% predicted), moderately (FEV1 >46‐<65% predicted) and minimally affected (FEV1 >65% predicted))
