Can exercise replace other methods of airway clearance for people with cystic fibrosis (CF)?
CF affects many systems in the body, mainly the respiratory system. It causes a build-up of thick, sticky mucus in the lungs which causes irritation and damage to the lining of the airways. CF treatment involves chest physiotherapy, also called airway clearance, which uses a range of devices or techniques to get rid of this mucus. It has been suggested that exercise may have a similar effect. Exercising results in a person taking different volumes and depths of breaths. This leads to pressure changes and forces within the airways that move secretions out of the lungs. We compared the effect on lung function of exercise versus other techniques, to see if exercise is a suitable alternative for people with CF. We wanted to answer our review question to potentially reduce their treatment burden.
The evidence is current to 15 February 2022.
We searched the literature for studies where people received at least two treatment sessions of exercise or another airway clearance technique, and report on four studies including 86 people with CF in the review. The people in the studies were aged between 7 and 41 years and had varying degrees of disease severity. Three studies included people who were clinically well and one study included people admitted to hospital for a chest infection. The studies lasted between four days and six months and compared exercise (alone or in combination with another airway clearance technique) to other techniques. Two studies compared exercise with postural drainage and percussion (PD&P), one study compared exercise with the active cycle of breathing technique (ACBT) and one study compared exercise with underwater positive expiratory pressure (uPEP), also known as bubble PEP. Three studies received financial support from funding bodies such as the Cystic Fibrosis Trust, the Buffalo Foundation and the Romanian National Council for Scientific Research in Higher Education.
We did not find enough evidence to conclude whether or not exercise can replace other methods of airway clearance. We did not find any evidence to suggest that exercise was either better or worse than other methods to improve lung function or clear mucus from the airways, although exercising did improve people's exercise ability, and it was the preferred choice of treatment in one study. None of the studies reported any negative effects of exercise therapy. None of the studies evaluated quality of life or the need for extra antibiotic treatment. One study did suggest that exercise alone was less effective at clearing sputum than ACBT.
Exercise versus ACBT
One study (18 participants) found that a measure of lung function temporarily (up to 30 minutes) increased in the exercise group only, otherwise there was no difference between the ACBT or the exercise group. No adverse events were reported, and it is not certain if ACBT was thought to be more effective or was preferred. The exercise group produced less sputum than the ACBT group. The study did not report on exercise capacity, quality of life, adherence, hospitalisations and need for additional antibiotics.
Exercise plus PD&P versus PD&P alone
Two studies (55 participants) compared exercise plus PD&P to PD&P alone. At two weeks, one trial described a greater increase in lung function with PD&P alone, while at six months the second study reported a greater increase with exercise plus PD&P (but did not provide data for the PD&P group). One study reported no side effects at all, and also reported no difference between groups in exercise capacity (maximal work rate), sputum volume or the average length of time spent in hospital. Conversely, the second study reported fewer hospitalisations due to exacerbations in the exercise and PD&P group. Neither study reported on quality of life, preference and the need for antibiotics.
Exercise versus uPEP
One study (13 participants) compared exercise to uPEP (also known as bubble PEP). No adverse events were recorded in either group and investigators reported that those taking part thought that, while exercise was more tiring, it was also more enjoyable than bubble PEP. We found no differences in the total weight of sputum collected during treatment sessions. The study did not report on lung function, quality of life, exercise capacity, adherence, need for antibiotics or hospitalisations.
Certainty of the evidence
Overall, we had very little confidence in the evidence because all four studies had few participants and two studies only presented results as a shortened report given at a conference.
We do not think the fact that participants and people measuring the outcomes knew which treatment the participants were receiving influenced the results of outcomes such as lung function and sputum weight. We do not think the fact that these studies were financed should influence the interpretation of the results in this review.
As one of the top 10 research questions identified by clinicians and people with CF, it is important to systematically review the literature regarding whether or not exercise is an acceptable and effective ACT, and whether it can replace traditional methods. We identified an insufficient number of trials to conclude whether or not exercise is a suitable alternative ACT, and the diverse design of included trials did not allow for meta-analysis of results. The evidence is very low-certainty, so we are uncertain about the effectiveness of exercise as an ACT. Longer studies examining outcomes that are important to people with CF are required to answer this question.
There are many accepted airway clearance techniques (ACTs) for managing the respiratory health of people with cystic fibrosis (CF); none of which demonstrate superiority. Other Cochrane Reviews have reported short-term effects related to mucus transport, but no evidence supporting long-term benefits. Exercise is an alternative ACT thought to produce shearing forces within the lung parenchyma, which enhances mucociliary clearance and the removal of viscous secretions.
Recent evidence suggests that some people with CF are using exercise as a substitute for traditional ACTs, yet there is no agreed recommendation for this. Additionally, one of the top 10 research questions identified by people with CF is whether exercise can replace other ACTs.
Systematically reviewing the evidence for exercise as a safe and effective ACT will help people with CF decide whether to incorporate this strategy into their treatment plans and potentially reduce their treatment burden. The timing of this review is especially pertinent given the shifting landscape of CF management with the advent of highly-effective small molecule therapies, which are changing the way people with CF are cared for.
To compare the effect of exercise to other ACTs for improving respiratory function and other clinical outcomes in people with CF and to assess the potential adverse effects associated with this ACT.
On 28 February 2022, we searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched the reference lists of relevant articles and reviews.
We searched online clinical trial registries on 15 February 2022.
We emailed authors of studies awaiting classification or potentially eligible abstracts for additional information on 1 February 2021.
We selected randomised controlled studies (RCTs) and quasi-RCTs comparing exercise to another ACT in people with CF for at least two treatment sessions.
Two review authors independently extracted data and assessed risk of bias for the included studies. They assessed the certainty of the evidence using GRADE. Review authors contacted investigators for further relevant information regarding their publications.
We included four RCTs. The 86 participants had a wide range of disease severity (forced expiratory volume in one second (FEV1) ranged from 54% to 95%) and were 7 to 41 years old. Two RCTs were cross-over and two were parallel in design. Participants in one RCT were hospitalised with an acute respiratory exacerbation, whilst the participants in three RCTs were clinically stable. All four RCTs compared exercise either alone or in combination with another ACT, but these were too diverse to allow us to combine results. The certainty of the evidence was very low; we downgraded it due to low participant numbers and high or unclear risks of bias across all domains.
Exercise versus active cycle of breathing technique (ACBT)
One cross-over trial (18 participants) compared exercise alone to ACBT. There was no change from baseline in our primary outcome FEV1, although it increased in the exercise group before returning to baseline after 30 minutes; we are unsure if exercise affected FEV1 as the evidence is very low-certainty. Similar results were seen for other measures of lung function. No adverse events occurred during the exercise sessions (very low-certainty evidence). We are unsure if ACBT was perceived to be more effective or was the preferred ACT (very low-certainty evidence). 24-hour sputum volume was less in the exercise group than with ACBT (secondary outcome). Exercise capacity, quality of life, adherence, hospitalisations and need for additional antibiotics were not reported.
Exercise plus postural drainage and percussion (PD&P) versus PD&P only
Two trials (55 participants) compared exercise and PD&P to PD&P alone. At two weeks, one trial narratively reported a greater increase in FEV1 % predicted with PD&P alone. At six months, the other trial reported a greater increase with exercise combined with PD&P, but did not provide data for the PD&P group. We are uncertain whether exercise with PD&P improves FEV1 as the certainty of evidence is very low. Other measures of lung function did not show clear evidence of effect. One trial reported no difference in exercise capacity (maximal work rate) after two weeks. No adverse events were reported (1 trial, 17 participants; very low-certainty evidence). Adherence was high, with all PD&P sessions and 96% of exercise sessions completed (1 trial, 17 participants; very low-certainty evidence). There was no difference between groups in 24-hour sputum volume or in the mean duration of hospitalisation, although the six-month trial reported fewer hospitalisations due to exacerbations in the exercise and PD&P group. Quality of life, ACT preference and need for antibiotics were not reported.
Exercise versus underwater positive expiratory pressure (uPEP)
One trial (13 participants) compared exercise to uPEP (also known as bubble PEP). No adverse events were recorded in either group (very low-certainty evidence). Trial investigators reported that participants perceived exercise as more fatiguing but also more enjoyable than bubble PEP (very low-certainty evidence). There were no differences found in the total weight of sputum collected during treatment sessions. The trial did not report the primary outcomes (FEV1, quality of life, exercise capacity) or the secondary outcomes (other measures of lung function, adherence, need for antibiotics or hospitalisations).