Pulmonary function in moderate neuromuscular disease without respiratory complaints.

Pulmonary function studies were carried out in 29 patients with moderate neuromuscular disease who had virtually no respiratory complaints. The earliest and most pronounced abnormalities were decreased transrespiratory pressures. Next a restrictive pulmonary defect with increased residual volume and a proportional decrease of maximal expiratory flows occurred, together with a decrease in static lung compliance. Because of a decrease in transpulmonary pressure at total lung capacity and often an increase in diffusing capacity per unit lung volume the above mentioned restrictive defects were attributed to muscular weakness and interstitial lung disease was excluded. Finally, some ventilation inequality could be found, probably originating in the poorly ventilated supradiaphragmatic regions.