Active cycle of breathing technique for cystic fibrosis

People with cystic fibrosis (CF) experience chronic airway infections as a result of mucus buildup within the lungs. Repeated infections often cause lung damage and disease. Airway clearance therapies aim to improve mucus clearance, increase sputum production, and improve airway function. The active cycle of breathing technique (ACBT) is an airway clearance method that uses a cycle of techniques to loosen airway secretions including breathing control, thoracic expansion exercises, and the forced expiration technique. This is an update of a previously published review.

To compare the clinical effectiveness of ACBT with other airway clearance therapies in CF.

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched clinical trials registries and the reference lists of relevant articles and reviews. Date of last search: 29 March 2021.

We included randomised or quasi-randomised controlled clinical studies, including cross-over studies, comparing ACBT with other airway clearance therapies in CF.

Two review authors independently screened each article, abstracted data and assessed the risk of bias of each study. We used GRADE to assess our confidence in the evidence assessing quality of life, participant preference, adverse events, forced expiratory volume in one second (FEV₁) % predicted, forced vital capacity (FVC) % predicted, sputum weight, and number of pulmonary exacerbations.

Our search identified 99 studies, of which 22 (559 participants) met the inclusion criteria. Eight randomised controlled studies (259 participants) were included in the analysis; five were of cross-over design. The 14 remaining studies were cross-over studies with inadequate reports for complete assessment. The study size ranged from seven to 65 participants. The age of the participants ranged from six to 63 years (mean age 18.7 years). In 13 studies follow up lasted a single day. However, there were two long-term randomised controlled studies with follow up of one to three years. Most of the studies did not report on key quality items, and therefore, have an unclear risk of bias in terms of random sequence generation, allocation concealment, and outcome assessor blinding. Due to the nature of the intervention, none of the studies blinded participants or the personnel applying the interventions. However, most of the studies reported on all planned outcomes, had adequate follow up, assessed compliance, and used an intention-to-treat analysis. Included studies compared ACBT with autogenic drainage, airway oscillating devices (AOD), high-frequency chest compression devices, conventional chest physiotherapy (CCPT), positive expiratory pressure (PEP), and exercise. We found no difference in quality of life between ACBT and PEP mask therapy, AOD, other breathing techniques, or exercise (very low-certainty evidence). There was no difference in individual preference between ACBT and other breathing techniques (very low-certainty evidence). One study comparing ACBT with ACBT plus postural exercise reported no deaths and no adverse events (very low-certainty evidence). We found no differences in lung function (forced expiratory volume in one second (FEV₁) % predicted and forced vital capacity (FVC) % predicted), oxygen saturation or expectorated sputum between ACBT and any other technique (very low-certainty evidence). There were no differences in the number of pulmonary exacerbations between people using ACBT and people using CCPT (low-certainty evidence) or ACBT with exercise (very low-certainty evidence), the only comparisons to report this outcome.

There is little evidence to support or reject the use of the ACBT over any other airway clearance therapy and ACBT is comparable with other therapies in outcomes such as participant preference, quality of life, exercise tolerance, lung function, sputum weight, oxygen saturation, and number of pulmonary exacerbations. Longer-term studies are needed to more adequately assess the effects of ACBT on outcomes important for people with cystic fibrosis such as quality of life and preference.