Purpose: The aim of our study was to assess the long-term effects of specific inspiratory muscle training (IMT) in patients with neuromuscular disorders (NMDs) who have various degrees of respiratory impairment.
Patients and methods: Twenty-seven patients with NMDs (Duchenne's muscular dystrophy, 18 patients; spinal muscular atrophy, 9 patients) underwent 24 months of IMT. Patients were divided into three groups according to their vital capacity (VC) values. VC was measured as the parameter for the respiratory system involvement of the disease. Maximal inspiratory pressure (PImax) was assessed as the parameter for respiratory muscle strength, and the results of the 12-s maximum voluntary ventilation test (12sMVV) were assessed as the parameter for respiratory muscle endurance. Pulmonary and inspiratory muscle function parameters were assessed 6 months before training, at the beginning of training, and then every 3 months.
Results: The PImax values improved in group A (VC, 27 to 50% predicted) from 51.45 to 87.00 cm H(2)O, in group B (VC, 51 to 70% predicted) from 59.38 to 94.4 cm H(2)O, and in group C (VC, 71 to 96% predicted) from 71.25 to 99.00 cm H(2)O. The 12sMVV values improved in group A from 52.69 to 69.50 L/min, in group B from 53.18 to 62.40 L/min, and in group C from 59.48 to 70.5 L/min. For all three groups, there was a significant improvement of PImax (p < 0.007) and 12sMVV (p < 0.015) until the 10th month when a plateau phase was reached with no decline in the following month until the end of training.
Conclusion: With IMT, respiratory muscle function can be improved in the long term of up to 2 years.