[Chest wall mechanics in neuromuscular disease]

Chest wall movement and respiratory muscle strength in patients with neuromuscular diseases was studied. Amyotrophic lateral sclerosis, myasthenia gravis and polymyositis were included. Anterior-posterior (AP) and lateral (LT) diameters of the chest wall were measured at the levels of the 2nd and 5th rib, and the abdomen, using 6 pairs of pneumo-magnetometer. Paradoxical movement of LT was often observed in most diseases. Furthermore, both AP and LT of the abdomen showed a paradoxical movement. This paradoxical movement was augmented in resistive loaded breathing and maximum voluntary ventilation. Baseline pulmonary function was minimally disturbed, except for an increase in RV. However, maximum respiratory muscle strength of both inspiratory and expiratory muscles was decreased to approximately 40% of the predicted. This study suggests that neuromuscular diseases may involve the respiratory muscle in the relatively early stage of the disease.