Long-Term Effects of Lung Volume Recruitment on Maximal Inspiratory Capacity and Vital Capacity in Duchenne Muscular Dystrophy

Rationale: Lung volume recruitment therapy slows rate of decline of lung function in neuromuscular disease, possibly due to enhanced airway clearance, reduced atelectasis, or prevention of chest wall contractures. Objectives: To determine if lung volume recruitment maintains maximal insufflation capacity (MIC), despite decline in VC. Methods: This was a retrospective cohort study (1991-2008) of individuals with Duchenne muscular dystrophy at pediatric and adult tertiary centers. Lung volume recruitment was prescribed twice daily, according to protocol. Changes over time in MIC, VC percentage predicted, the difference between MIC and VC, maximum inspiratory and expiratory pressures, and assisted and unassisted peak cough flow (PCF) were assessed using linear mixed effects models. Measurements and Main Results: Sixteen individuals, 8.6 to 33.0 years old at initiation of lung volume recruitment, with median VC percentage predicted of 13.5 (interquartile range, 8.0-20.3), were followed over a median of 6.1 years (range, 1.7-16.1 yr). MIC-VC differences were stable (change, 0.02 L/yr; P = 0.06). Post-lung volume recruitment, compared with pretreatment, rate of decline in VC decreased from 4.5% predicted/yr to 0.5% predicted/yr (P<0.001). Maximal inspiratory and expiratory pressures were unchanged (P = 0.08, 0.59 respectively). Assisted-spontaneous PCF difference was maintained (slope, 21.59 L/min/yr, P = 0.35). Conclusions: With lung volume recruitment therapy, MIC-VC differences were stable over time, indicating that respiratory system compliance remains stable, despite a loss in VC, in individuals with Duchenne muscular dystrophy. Decline in VC was significantly attenuated, and assisted PCF was maintained in a clinically effective range.