Inspiratory Muscle Training in Patients With Duchenne Muscular Dystrophy: Methods
One of the main problems in the treatment of patients with neuromuscular diseases is the progressive impairment of inspiratory muscle function. Since chest wall and pulmonary compliance are reduced in neuromuscular diseases, the mechanical load on the weakened respiratory muscles is increased. Imbalance between load and capacity of the respiratory muscles may lead to fatigue and respiratory failure, which is the most important cause of death in these patients. Therefore, the treatment of diseased respiratory muscles to improve their strength and endurance presents a great challenge in the treatment of patients with neuromuscular diseases. Pharmacologic therapy was reported to possibly strengthen the respiratory muscles and make them less susceptible to fatigue. Also, periodic respiratory muscle rest and training were used to prevent the decline in respiratory muscle function. canadianfamilypharmacy
Previous studies have shown that strength and endurance of the respiratory muscles can be improved through specific training programs in normal subjects, patients with COPD, patients with cystic fibrosis, and quadriplegics. However, the role of inspiratory muscle training remains controversial in patients with neuromuscular diseases. On the one hand, it is alleged that inspiratory muscle training is potentially hazardous, since it may accelerate fatigue in the already very weak respiratory muscles by overwork and therefore cannot be recommended. On the other hand, improvement of inspiratory muscle function by specific training programs has been reported, but these studies were uncontrolled. The question of whether the use of inspiratory muscle training is sensible remains unanswered. And if the answer is yes, when should we intervene in the course of the patient’s disease?
The goal of our study is to answer the following questions: (1) Does respiratory muscle training in patients with Duchenne muscular dystrophy (DMD) improve inspiratory muscle function or does it do more harm? (2) Does the severity of the existing pulmonary function impairment affect the obtainable training effects?
Subjects
Thirty patients with DMD participated in our study. Before entering the study, they were randomly assigned to receive or not receive inspiratory muscle training. The age in the training group ranged from 10 to 24 years (mean, 13.6 ± 4.5 years), in the control group from 9 to 20 years (mean, 14.5 ± 3.8 years); all had the onset of their disease between 3 and 5 years of age. In the training group, 12 patients, and in the control group, 11 patients were wheelchair bound, corresponding to functional capacity stage 9, according to the criteria of Inkley et al. All patients were free from respiratory tract infections. None of them had symptoms or signs of inspiratory muscle fatigue, such as exertional dyspnea, orthopnea, or paradoxic breathing, which are obligatory indications for rest. No patient described sleep disturbance, daytime hypersomnolence, or morning headache, and none had an episode of acute respiratory failure requiring endotracheal ventilation. The diagnosis of DMD had been made on clinical, enzymatic, electromyographic, and muscle biopsy specimen criteria. Informed consent was obtained from all subjects and the study was approved by the Human Subject Committee of the hospital.