Abstract: Our search identified 62 studies, of which 19 (440 participants) met the inclusion criteria. Five randomised controlled studies (192 participants) were included in the meta-analysis; three 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 22.33 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 the active cycle of breathing technique with autogenic drainage, airway oscillating devices, high frequency chest compression devices, conventional chest physiotherapy, and positive expiratory pressure. Preference of technique varied: more participants preferred autogenic drainage over the active cycle of breathing technique; more preferred the active cycle of breathing technique over airway oscillating devices; and more were comfortable with the active cycle of breathing technique versus high frequency chest compression. No significant difference was seen in quality of life, sputum weight, exercise tolerance, lung function, or oxygen saturation between the active cycle of breathing technique and autogenic drainage or between the active cycle of breathing technique and airway oscillating devices. There was no significant difference in lung function and the number of pulmonary exacerbations between the active cycle of breathing technique alone or in conjunction with conventional chest physiotherapy. All other outcomes were either not measured or had insufficient data for analysis. There is insufficient evidence to support or reject the use of the active cycle of breathing technique over any other airway clearance therapy. Five studies, with data from eight different comparators, found that the active cycle of breathing technique was 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 the active cycle of breathing technique on outcomes important for people with cystic fibrosis such as quality of life and preference.

Plain-language summary: While 19 studies comparing the active cycle of breathing technique with other airway clearance therapies are included in the review, only five studies (192 participants) reported data that we could include in the analysis. Each of the five studies compared different techniques: the active cycle of breathing technique was compared with autogenic drainage, airway oscillating devices, high-frequency chest compression devices, positive expiratory pressure, and conventional chest physiotherapy. Most studies lasted a single day, but there were two studies that lasted between one and three years. Participants ranged in age from six to 63 years and most (63%) were male. We found that the active cycle of breathing technique was comparable with other treatments in outcomes such as quality of life, personal preference, exercise tolerance, lung function, sputum weight, oxygen saturation, and the number of pulmonary exacerbations. We were not able to show that any single technique was better than another. Longer studies are needed to better assess the effects of the active cycle of breathing technique on outcomes important for people with cystic fibrosis such as quality of life and personal preference. Many of the studies did not provide enough details of their methods to determine if there were any biases that might have affected the results. Many studies did not report how they decided who would get which treatment and how they made sure that the people who were putting people into the different treatment groups and those who were assessing the results did not know which group each individual was in. Most of the included studies had a cross-over design (where people have one treatment and then switch to the second), and many of these did not report the length of time in between different treatments. As it is possible that the first treatment might affect the results of the next treatment, we only included results from the first treatment period. Many of the studies did not report separate results for just the first treatment period, so we did not include their results in our review. All participants knew which treatment group they were in (it is not possible to disguise different physiotherapy techniques). This could have affected the results for some of the self-reported outcomes, such as quality of life, personal preference, or exercise tolerance, but is unlikely to have affected the more objective outcomes, such as lung function. Most of the studies followed those taking part for less than one month and did this for most of the participants for the entire study period. In two out of the three longer studies more than 10% of the people taking part dropped out. The study results could be affected if the people who dropped out of the studies were not evenly spread across the different treatment groups. Over half of the studies checked that participants were using the airway clearance therapy they were supposed to. Most of the studies reported on all their planned outcomes. The findings of the review were limited as not many studies made the same comparisons; also, there were not many long-term studies and the studies we included did not report enough data.