Study objective: To assess the effect of interval-based inspiratory muscle training (IMT) combined with breathing retraining (BR) in patients with generalized myasthenia gravis (MG) in a partial home 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 BR (diaphragmatic breathing [DB] and pursed-lips breathing [PLB]) three times a week for 8 weeks. The sessions included 10 min each of DB, interval-based IMT, and PLB. Interval-based IMT 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 IMT associated with BR is feasible and effective in patients with generalized MG. Improvements in respiratory muscle strength, chest wall mobility, respiratory pattern, and respiratory endurance were observed.