Inspiratory Muscle Training in Patients With Duchenne Muscular Dystrophy: Discussion
Our study shows the following results:
(1) In patients with DMD, respiratory muscles and in particular the diaphragm, are trainable in terms of strength and endurance, provided that their ventilatory function is not severely restricted.
(2) In patients with VC values less than 25 percent predicted and/or a PaC02 of more than 45 mm Hg, a specific training of the inspiratory muscles does not produce any benefit. On the other hand, a damaging effect could be excluded, at least for a training period of 1 month.
The significance of skeletal muscle training in patients with neuromuscular disease is controversial. There is a scarcity of data regarding whether or not diseased muscles can be strengthened by specific training programs at all, much less the exact extent and stage of the disease at which skeletal muscles can be strengthened. In one patient with Duchenne dystrophy, histologic examination showed that those muscles assuming the least degree of sustained physical activity had the least degeneration, implying that physical activity hastened muscle fiber degeneration. It was therefore suspectpd that overwork or heavy exercise may accelerate skeletal muscle weakness in neuromuscular disease. my canadian pharmacy phone number
Our study, however, shows that strength and endurance of the inspiratory muscles can be improved by selective training, provided that the patient’s ventilatory function is not severely impaired. The results of our study therefore differ substantially from other earlier studies. It may be that none of these published studies has examined how training actually stresses the inspiratory muscles and the diaphragm. In patients where the pressures generated by the inspiratory musculature have been measured, these were only obtained at the beginning and at the end of the training. It has to be stated that measurement of maximal inspiratory mouth pressure, though it is widely used, cannot be recommended in all cases. Especially patients with weak mouth and cheek muscles tend to have difficulties with this method and, besides, the normal range is quite wide. To our knowledge, ours is the first controlled study that evaluates the global inspiratory muscle function and the diaphragmatic function selectively using maximal sniff assessed esophageal and transdiaphragmatic pressure values, respectively. For the measurement of global inspiratory muscle strength and the strength of the diaphragm, the sniff maneuver without a noseclip has turned out to be a reliable and reproducible technique. Another advantage is that most patients, even those with weakness of the cheek muscles, can easily perform the maneuvers.
Many previous authors have failed to document improvement in strength and endurance of the respiratory muscles by training because they could not make sure that the subjects truly performed the prescribed work. Since airflow and minute ventilation were not controlled during the training, the patients could minimize the work of breathing through resistive orifices by reducing inspiratory flow and breathing frequency. The stimulus for training in these studies could have been too weak. In our study, inspiratory airflow and Ve were measured continuously to ensure that the work of breathing remained constantly high.