Abstract: The searches identified 157 studies, of which eight cross-over studies (data from 96 participants) met the inclusion criteria. There were differences between studies in the way that interventions were delivered, with several of the intervention groups combining more than one treatment modality. One included study looked at autogenic drainage, six considered conventional chest physiotherapy, three considered oscillating positive expiratory pressure, seven considered positive expiratory pressure and one considered high pressure positive expiratory pressure. Of the eight studies, six were single-treatment studies and in two, the treatment intervention was performed over two consecutive days (once daily in one, twice daily in the other). This enormous heterogeneity in the treatment interventions prevented any meta-analyses from being performed. Blinding of participants, caregivers or clinicians in airway clearance studies is impossible; therefore this was not considered as a high risk of bias in the included studies. Lack of protocol data made assessment of risk of bias unclear for the majority of other criteria. Four studies, involving 28 participants, reported a higher amount of expectorated secretions during chest physiotherapy as compared to a control. One study, involving 18 participants, reported no significant differences in sputum weight. In five studies radioactive tracer clearance was used as an outcome variable. In three of these (28 participants) it was reported that chest physiotherapy, including coughing, increased radioactive tracer clearance as compared to the control period. One study (12 participants) reported increased radioactive tracer clearance associated with all interventions compared to control, although this was only reported to have reached significance for postural drainage with percussion and vibrations; and the remaining study (eight participants) reported no significant difference in radioactive tracer clearance between chest physiotherapy, without coughing, compared to the control period. Three studies, involving 42 participants reported no significant effect on pulmonary function variables following intervention; but one further study did report significant improvement in pulmonary function following the intervention in some of the treatment groups. The results of this review show that airway clearance techniques have short-term effects in the terms of increasing mucus transport. No evidence was found on which to draw conclusions concerning the long-term effects.

Plain-language summary: We included eight studies in the review reporting results from a total of 96 people with cystic fibrosis. All the studies were very different and some looked at multiple treatments compared to no treatment. One study looked at autogenic drainage, six considered conventional chest physiotherapy, three considered oscillating positive expiratory pressure, seven considered positive expiratory pressure and one considered high pressure positive expiratory pressure. We could not combine the results to analyse them statistically. Summarising the findings of these eight studies, we found that methods of clearing the airways have short-term benefits for moving mucus. Three studies measured sputum which had been coughed up and found those people using chest physiotherapy coughed up more sputum; four studies measured radioactive tracer clearance and found increased clearance with chest physiotherapy. Only one study reported an improvement in lung function in some of the treatment groups; but three other studies who reported this outcome did not find any significant effect from chest physiotherapy. At present there is no clear evidence of long-term effects in chest clearance, quality of life or survival with chest physiotherapy. Most of the included studies had some design problems which may affect confidence in the results. In just under half of the studies it was not clear as to whether all of the results were reported. In physiotherapy studies the person and their physiotherapist will know which treatment they are receiving and this may affect some of the findings. Half the studies looked at amount of sputum coughed up and lung function testing, with a quarter asking the person's views on the treatment and these results may have been affected by being aware of the treatment. In all of the studies it was not clear if the person was experienced in carrying out the treatment. This may affect how well they were able to do the treatment which could affect confidence in the results.