The active cycle of breathing technique: A systematic review and meta-analysis

Question: What is the best available research evidence (volume, quality, consistency, generalisability) for the active cycle of breathing technique (ACBT)? Design: Systematic review with meta-analysis. Participants: Participants with respiratory conditions characterised by chronic sputum production. Intervention: The active cycle of breathing or forced expiratory technique. Comparator: All comparators including control conditions. Outcome measures: All outcomes providing continuous data. Results: Twenty-four studies were included. Ten comparators were identified with the most common being conventional chest physiotherapy, positive expiratory pressure and a control. The outcomes most frequently assessed were sputum wet weight (n = 17), forced vital capacity (n = 12) and forced expiratory volume in 1 s (n = 12). Meta-analysis was completed on the primary outcome of sputum wet weight. The standardised mean difference (SMD, random effects) showed an increase in sputum wet weight during and up to 1 h post ACBT compared to conventional physiotherapy (SMD 0.32, 95%CI 0.05-0.59), external oscillatory devices (0.75, 0.48-1.02), and control (0.24, 0.02-0.46). Conclusion: The overall body of evidence was classified as good (good volume, quality and consistency, excellent generalisability). High level, variable risk of bias research evidence favours ACBT over most alternatives for short-term improvements in secretion clearance.