Posted on May 2, 2017
This blog is a critical appraisal of the randomised controlled trial: Dwyer, T. (2015) Non-invasive ventilation used as an adjunct to airway clearance treatments improves lung function during an acute exacerbation of cystic fibrosis: a randomised trial. Journal of Physiotherapy. Vol 61. (Issue 3). P. 142 – 147.
Cystic fibrosis (CF) is a common condition seen by respiratory physiotherapists. Affecting approximately 1 in 2500 people, CF is the most common inherited disease in the UK amongst white populations. CF accounts for 9,500 hospital admissions and over 100,000 hospital bed days a year (BLF, 2016), highlighting the importance of effective management within an acute setting.
Current practice focuses on symptom management, with mucus clearance at the forefront of physiotherapy (CSP, 2016). Techniques including active cycle breathing technique (ACBT), autogenic drainage (AD), postural drainage, exercise and airway clearance devices all contribute to managing patient symptoms.
The purpose of this study was to determine if non-invasive ventilation (NIV) could be considered as an adjunct to airway clearance, following the onset of acute CF exacerbation to improve lung function. Non-invasive ventilation (NIV) refers to the provision of ventilatory support through the patient’s upper airway using a mask or similar device.
This study recruited 40 patients who were all over 17 years old, and screened against eligibility criteria, with one excluded due to poor tolerance of non-invasive ventilation (NIV). 39 patients were included overall, with 20 in the control group, and 19 in the experimental group. As an intervention, NIV was used in the experimental group, as well as using pre-existing techniques for mucus clearance. The control group continued to implement pre-existing airway clearance techniques, without the use of NIV. Including a control group and including a single variable (NIV) enhances the validity of the study (Brewer, 2000).
All 39 patients were randomly allocated to either NIV treatment or the control condition by computer-generated block randomisation. Randomisation was performed by a person not involved in the study and stored in sealed envelopes which were opened after the participant had provided their consent to participate. The participants, treating therapists and independent assessors were not blinded to group allocation.
The outcome measures used for this study were Spirometry (FEV1; which measures lung function), Subjective symptom severity (including breathlessness, sputum volume, energy levels), Schwartz Fatigue Scale and 25-level modified shuttle, with the primary measure being the rate of change in FEV1 (% of predicted per day) from admission to discharge from hospital (this is the volume of air that has been exhaled at the end of the first second of forced expiration). The experimental group used NIV during chest physiotherapy from Day 2 of admission until discharge. Spirometry and symptom severity were recorded daily. All other outcome measures were collected on admission to, and discharge from, hospital.
Analysed as the primary outcome, the experimental group had a greater rate of improvement in FEV1 than the control group, but this was not statistically significant (MD 0.13% predicted per day, 95% CI –0.03 to 0.28). However, the experimental group showed a significantly higher FEV1 at discharge than the control group (MD 4.2% predicted, 95% CI 0.1 to 8.3).
The experimental group reported significantly lower levels of fatigue on the Schwartz fatigue scale at discharge than the control group (MD 6 points, 95% CI 1 to 11). There was no significant difference between the experimental and control groups in any of the other outcome measures.
To aid the evaluation of this study, the CASP RCT tool was used to guide the process. On evaluation, the study was clear in identifying the target population, intervention, comparator used against the intervention and the outcome measures implemented.
In relation to sample size, this study was small, with only 39 patients included. 3 of these patients included withdrew, however the data was still used after the 26-month period. For the study to have clinical relevance, there would need to be a larger number of patients included. The inclusion and exclusion criteria were clear.
This study has attempted to minimise bias by using computer generated block randomisation. This helps to rule out the ‘nuisance factor’ and improve accuracy within the study. However, there was no blinding as it was not possible to achieve due to the nature of the study. This is a significant limitation to the study as there may be potential bias present, which impacts on validity.
This study has shown that use of NIV as an adjunct to physiotherapy during a hospital admission for an acute exacerbation of CF significantly improved lung function and fatigue on discharge from hospital. This improvement in lung function, however, was not matched by improvements in symptom severity, exercise capacity, length of hospital stay, or the exacerbation-free period after discharge from hospital.
With increased FEV1 and lower fatigue levels identified, using NIV as an adjunct to mucus clearance may be an option in the future. However, the cost of routinely using NIV for CF patients is potentially a major limitation and may not be suitable for clinical practice within an already resource-limited NHS.
This study could be deemed more generalizable to broader clinical populations if it had targeted more severe CF patients or those with increased work of breathing and who did not tolerate standard chest physiotherapy. Therefore, this study should ideally have had a larger sample size and a larger range of CF severity in order for it to be of greater clinical relevance and to have enhanced its contribution to the physiotherapy evidence base.