What are the effects of using any airway clearance technique compared to not using an airway clearance technique for clearing excess mucus from the lungs of people with cystic fibrosis?
The lungs of people with cystic fibrosis produce excess mucus. This leads to repeated infection and tissue damage in the lungs. It is important to clear the mucus using medicines and airway clearance techniques (physiotherapy). There are different airway clearance techniques for clearing mucus, some of which may include the use of mechanical devices. Daily physiotherapy takes a lot of time and trouble, so it is important to know if it works. We searched for studies where the people taking part had equal chances of being in the group using airway clearance techniques or the group with no airway clearance techniques. This is an update of a previously published review.
The evidence is current to 17 October 2022.
We included 12 studies that enrolled 194 people with cystic fibrosis. The studies were very different and some looked at multiple treatments compared to no treatment. One study used autogenic drainage (a controlled breathing technique which uses different speeds and depths of exhaled breath to move mucus up the airways so it can be cleared by coughing); five studies used conventional chest physiotherapy (manual techniques of percussion and vibration applied to the chest wall, usually with the assistance of a physiotherapist or relative); nine used positive expiratory pressure (breathing out through a mask or mouthpiece against a resistance which causes pressure to build up in the lungs to move the mucus), and one of these varied pressure so used both standard and high-pressure positive expiratory pressure; three studies used oscillating positive expiratory pressure (positive expiratory pressure combined with vibrations within the airway to loosen mucus); two used exercise (on a treadmill); and two used high-frequency chest wall oscillation (high frequency vibrations applied outside the chest wall via an inflatable garment). We could not combine any results to analyse them statistically.
Summarising the findings of the 12 studies, we found limited evidence of a short-term impact on lung function. Only one study reported an improvement in lung function in some of the treatment groups, whilst six other studies found no improvement.
This review found that methods of clearing the airways may have short-term benefits for moving mucus. Four studies found that the people using airway clearance techniques coughed up more sputum, but one study reported no difference with or without using an airway clearance technique. Five studies reported increased radioactive tracer clearance (a test in which people are imaged continuously after inhaling a radioaerosol to assess the time for it to be cleared from the lung) when using airway clearance, but one study of positive expiratory pressure found no difference. At present, there is no clear evidence to show the long-term effects of performing airway clearance techniques on quality of life or survival.
Limitations of the evidence
We have little or very little confidence in the evidence, for several reasons. Most included studies had design problems, and in just under half of the studies, it was unclear whether all the results were reported. Also, in physiotherapy studies, the person receiving treatment and their physiotherapist know which treatment they are receiving, and this may affect some of the findings. For example, the amount of mucus coughed up and lung function tests (measured by half of the included studies) and a person's views on a particular technique (recorded in a quarter of the included studies) may be affected if a person is aware of which treatment they are receiving. Finally, it was not clear in most studies whether the individual was experienced with the technique they were using.
We were unable to find any studies looking at the effects of airway clearance techniques in people treated with the new cystic fibrosis transmembrane conductance regulator (CFTR) modulator treatments. Cystic fibrosis is caused by faulty proteins on the cell surface made by the mutated CFTR gene; these new medicines are designed to correct the function of the faulty proteins.