Positive expiratory pressure prevents more exacerbations than high frequency chest wall oscillation via a vest in people with cystic fibrosis

Blikk på forskning i Fysioterapeuten 11/2014.


Blikk på forskning utarbeides i samarbeid med Journal of Physiotherapy (Australia), som trykker forskningspresentasjonene under betegnelsen Critically appraised Papers, CAPs.


Summary of: McIlwaine MP, et al (2013) Long-term multicenter randomised controlled study of high frequency chest wall oscillation versus positive expiratory pressure mask in cystic fibrosis. Thorax DOI: thoraxjnl-2012-202915. [Prepared by Mark Elkins, Journal Editor.]

Question: What are the relative effects of high frequency chest wall oscillation (HFCWO) and positive expiratory pressure (PEP) therapy on pulmonary exacerbations, lung function, and quality of life in people with cystic fibrosis?

Design: Randomised trial with concealed allocation and blinded outcome assessment.

Setting: Eight paediatric and four adult cystic fibrosis centres in Canada.

Participants: People over 6 years old with clinically stable cystic fibrosis and forced expiratory volume in 1 sec (FEV1) over 45% of the predicted value. Uncommon respiratory organisms and recent changes in medications were exclusion criteria. Randomisation allocated 56 participants to HFCWO and 51 to PEP.

Interventions: All participants used an airway clearance method other than HFCWO or PEP for 2 months prior to starting their intervention. The HFCWO group then used a pneumatic vest system to apply high frequency oscillations with a triangular wave form to the chest wall. A 30-min ramped protocol was used consisting of six 5-min cycles, with the participant performing 2–3 huffs between cycles. The PEP group breathed through a facemask with an expiratory resistor creating a back pressure of 10–20 cmH20, for six cycles of 15 breaths, also separated by 2–3 huffs. The allocated airway clearance regimen was prescribed twice daily for one year.

Outcome measures: The primary outcome was the number of pulmonary exacerbations, defined as when prespecified symptoms lasted longer than 3 days and required antibiotics. Secondary outcomes included time to first pulmonary exacerbation and changes in lung function and quality of life.

Results: 88 participants completed the study. At one year, the median number of pulmonary exacerbations per participant was 2 (IQR 1 to 3) in the HFCWO, which was significantly higher than in the PEP group at 1 (IQR 0 to 2), p = 0.007. Median time to first exacerbation was 115 days in the HFCWO group, which was significantly sooner than in the PEP group at 220 days, p = 0.02. Changes in lung function and quality of life did not significantly differ between the groups. PEP was rated as significantly better than HFCWO with respect to flexibility in where it could be performed (p < 0.001) and the duration of each treatment, which differed by a median of 10 min (p < 0.001). Self-reported adherence was over 90% in both groups.

Conclusion: When prescribed as a long-term airway clearance therapy, PEP has significantly better outcomes than HFCWO in terms of exacerbations, flexibility, and treatment duration.


This study is an excellent example of research designed to resolve a widespread clinical question. The marked difference in pulmonary exacerbations in this trial, alongside equivocal outcomes for lung function and quality of life, shows clearly the superiority of PEP over HFCWO as a regular airway clearance therapy for this population. PEP’s superiority is reinforced by the other characteristics on which it was rated as better than HFCWO by participants: treatment duration, and flexibility of treatment location. The paper does not provide much detail about the standard care received by both groups, apart from baseline respiratory medication use. Given that ordering and overlapping nebulised and physical therapies in an airway clearance session can influence the overall session duration (Bishop et al 2011, Dentice et al 2012, Dentice et al 2013), more information about how nebulised therapies were incorporated into the overall airway clearance sessions could have been providded..

Another crucial consideration is cost, with a HFCWO system being about 100 fold more expensive than a PEP mask system. With better outcomes for far less expense, physiotherapists should strongly recommend PEP over HFCWO.

Adherence to the therapies was very high at 94%. Although self-reported adherence can easily be inflated, this is much higher than in other studies using self-report (Modi et al 2006, Myers & Horn 2006). This may be due to a selection effect of participation in an airway clearance study and the monthly telephone calls to encourage good adherence. This study illustrates the importance of obtaining evidence about the effects of therapies that are prescribed for longterm use. Recent studies of new airway clearance and exercise interventions in CF continue to consider only single doses (Kuys et al 2011, Reix et al 2012), so clinicians should be wary of prescribing regular use of new interventions (especially expensive ones) before their long-term effects are known.

Louella O’Herlihy, Physiotherapy Department, Poole Hospital, UK


Abbott J et al (1996) Thorax 51: 1233–1238.

Bishop JR et al (2011) J Physiother 57: 223–229.

Dentice RL et al (2012) J Physiother 58: 33–40.

Dentice RL et al (2013) Cochrane Database Syst Rev:CD007923.

Kuys SS et al (2011) J Physiother 57: 35–40.

Modi AC et al (2006) J Cyst Fibrosis 5: 177–185.

Myers LB, Horn SA (2006) J Health Psychol 11: 915–926.

Reix P et al (2012) J Physiother 58: 241–247.


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