What are the effects of active cycle of breathing technique (ACBT) compared with other methods of airway clearance in people with cystic fibrosis?
Chronic infections are common in cystic fibrosis, and repeated infections can cause lung damage and disease. People with cystic fibrosis use airway clearance therapies to clear mucus and improve lung function. The ACBT uses a combination of three breathing methods to loosen and clear mucus. This is an update of a previously published review.
The evidence is current to: 29 March 2021.
While we included 22 studies comparing ACBT with other airway clearance therapies in the review, only eight studies (259 participants) reported data that we could include in the analysis. Each of the eight studies compared different techniques: ACBT was compared with autogenic drainage, airway oscillating devices, high-frequency chest compression devices, positive expiratory pressure, conventional chest physiotherapy, and ACBT together with exercise. 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 (59%) were male.
We found that ACBT 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 ACBT on outcomes important for people with cystic fibrosis such as quality of life and personal preference.
Certainty of the evidence
We have little or no confidence in the evidence and think that further research is very likely to affect our conclusions of this review for any of the interventions analysed.
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.
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.
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.