A Cochrane review [Abstract] 1 included 26 studies with a total of 733 subjects. Most included studies were of low quality. 18 studies (n=296) were cross-over in design. Positive expiratory pressure (PEP) was compared to active cycle of breathing techniques (ACBT), autogenic drainage (AD), oral oscillating PEP devices, high frequency chest wall oscillation (HFCWO) and Bi level PEP devices (BiPaP) and exercise. Single interventions or series of treatments continued for up to three months demonstrated no significant difference in effect between PEP and other methods of airway clearance on FEV1. Long-term studies had equivocal or conflicting results regarding the effect on FEV1. There was a lower exacerbation rate in participants using PEP compared to other techniques when used with a mask for at least one year. In all studies with an intervention period of at least one month, measures of participant preference were in favour of PEP.
Comment: The quality of evidence is downgraded by limitations in study quality, by imprecise results (limited study size for each comparison) and by inconsistency (heterogeneity in interventions and outcomes).
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