Respiratory muscles and pulmonary functions in muscle dystrophy

ABSTRACT

Respiratory muscle function was assessed in 15 patients with muscle dystrophy, the relationship between respiratory muscle efficiency, pulmonary functions and gaseous exchange has been identified. These patients were subjected to routine pulmonary function test, arterial blood gases and to specific respiratory muscle function test including maximal inspiratory pressure, PI max, maximal expiratory pressure PE max, respiratory muscle strength RMS, trans diaphragmatic pressure difference PDi and vital capacity in upright and supine position delta VC. Data of this work revealed reduction in all of the respiratory muscle function tests, increased difference in the vital capacity between upright and supine position and decrease in transdiaphragmatic pressure difference, which all reflect respiratory muscle weakness. Reduction in respiratory muscle efficiency produces a restrictive pattern of pulmonary function with reduction in the vital capacity and maximal voluntary ventilation which are highly dependent on RMS. Arterial blood gases revealed hypoxia and hypercapnia, this change reflects alveolar hypoventilation secondary to respiratory muscle weakness. It might be anticipated that decrements in VC, MVV, PaO2, would relate directly to the degree of respiratory muscle weakness. Objective measurement of respiratory functions are essential in the management of these patients and the most valuable are essential in the management of these patients and the most valuable are serial measurements of vital capacity and arterial carbon dioxide tension