Effects of 8-week, interval-based inspiratory muscle training and breathing retraining in patients with generalized myasthenia gravis

Study objective: To assess the effect of interval-based inspiratory muscle training (IMT) combined with breathing retraining (1311) in patients with generalized myasthenia gravis (MG) in a partial homed program. Design: A randomized controlled trial with blinding of outcome assessment. Setting: A secondary-care respiratory clinic. Patients: Twenty-seven patients with generalized MG were randomized to a control group or a training group. Interventions: The training group underwent interval-based IMT associated with Bill (diaphragmatic breathing [1313] and pursed-lips breathing [PLB]) three times a week for 8 weeks. The sessions included 10 min each of 1313, interval-based IMT, and PLB. Interval-based INIT consisted of training series interspersed with recovery time. The threshold load was increased from 20 to 60% of maximal inspiratory pressure (PImax) over the 8 weeks. Measurements and results: Lung function, respiratory pattern, respiratory muscle strength, respiratory endurance, and thoracic mobility, were measured before and after the 8 weeks. The training group improved significantly compared to control group in PImax (p = 0.001), maximal expiratory pressure (PEmax) [p = 0.01], respiratory rate (RR)/tidal volume (VT) ratio (p = 0.05), and upper chest wall expansion (p = 0.02) and reduction (p = 0.04). Significant differences were seen in the training group compared to baseline PImax (p 0.001), PEmax (p = 0.01), maximal voluntary, ventilation (p = 0.02), RR/VT ratio (p = 0.003), VT (p = 0.02), RR (p = 0.01), total time of RR (p = 0.01), and upper chest wall expansion (p = 0.005) and reduction (p = 0.005). No significant improvement was seen in lower chest wall or lung function. Conclusions: The partial home program of interval-based INIT associated with Bill is feasible and effective in patients with generalized MG. Improvements in respiratory muscle strength, chest wall mobility, respiratory pattern, and respiratory endurance were observed.