Outcomes and measures in studies of techniques to promote secretion clearance in individuals with neuromuscular conditions: a scoping review.

Background: Techniques to support secretion clearance for individuals with neuromuscular conditions and respiratory muscle weakness include mechanical insufflation-exsufflation and chest wall vibrations. Assessing the comparative efficacy of these techniques is challenging due to the absence of a core outcome set. We sought to describe outcomes and measurement instruments reported in studies of airway clearance techniques for individuals with neuromuscular conditions living in the community. Methods: We conducted a scoping review of primary research studies. We searched six databases from inception to 22 February 2024. Two reviewers independently screened citations against the inclusion criteria and extracted data on outcomes and measurement characteristics. Outcomes were categorised according to the Core Outcome Measures in Effectiveness Trials (COMET) 38-domain taxonomy. Results: We identified 75 eligible studies describing 55 outcomes. We grouped outcomes deemed overlapping and categorised them using the COMET 38-domain taxonomy, resulting in 34 distinct outcomes. Common physiological/clinical outcomes were cough strength (n=48 studies, 64%), lung volume (n=48, 64%) and insufflation capacity (n=22, 29%). The most common measurement tools for these outcomes were spirometer (n=38, 51%), peak flow meter (n=24, 32%) and pneumotachograph (n=20, 27%). The most common resource-use outcome was hospitalisation due to respiratory illness (n=13, 17%). Few studies reported on life impact outcomes, with the most common being comfort (n=6, 8%) and patient satisfaction (n=4, 5%). Conclusion: We identified 34 outcomes from 75 studies, which were most commonly physiological/clinical, with resource-use and life impact outcomes being seldom reported. The number and range of outcomes and measures demonstrates the need for a core outcome set.