Patterns of Adherence to Lung Volume Recruitment Therapy Amongst Individuals With Duchenne Muscular Dystrophy: A Secondary Analysis of the STEADFAST Randomized Controlled Trial

BACKGROUND: Duchenne muscular dystrophy (DMD) is associated with impaired airway clearance and chest wall restriction, treated with lung volume recruitment (LVR) therapy. This study evaluated adherence patterns to LVR over 2 years in a cohort of boys with DMD. METHODS: Participants were included from the intervention arm of STEADFAST, a multi-centre randomized controlled trial of twice-daily LVR over 2 years in boys with DMD, 6-16 years with baseline forced vital capacity percent predicted (FVC%) ≥ 30% (Clinicaltrials. gov # NCT01999075). Adherence data were downloaded from a data logger on the LVR equipment and defined as LVR use at least daily on >50% of days. Logistic regression models evaluated associations between adherence and change in FVC%, rate of symptoms and change in quality of life (QOL) over 24 months. RESULTS: Fourteen of 33 boys (42.4%) were adherent to LVR. Among those non-adherent in the first 3 months, only one became adherent to LVR. Adherent participants tended to have lower baseline FVC % predicted than non-adherent individuals (median 77.2 (IQR (17.8) vs 89.7 (18.8) %; p = 0.08). The odds ratio for adherence was 1.02 (95% CI 0.97-1.08, p = 0.4) per unit increase in FVC%, and 0.08 (95% CI 0.001-11.7, p = 0.307) for each additional symptom/month over 24 months, adjusting for baseline age and ambulatory status. Adherence was not associated with QOL. CONCLUSIONS: Long-term LVR adherence was associated with early LVR usage pattern, but not change in lung function, symptoms or QOL. These findings underscore the importance of early support and education to promote long-term LVR adherence.