Control of ventilation, respiratory muscle strength, and granulomatous involvement of skeletal muscle in patients with sarcoidosis.

Granulomatous involvement of skeletal muscle occurs in 50 to 80 percent of patients with sarcoidosis. How this may affect respiratory muscle function in sarcoidosis is not known. To attempt to answer this question, we compared respiratory function and muscle force generation, and control of ventilation in 12 untreated patients with 12 healthy, nonsmoking subjects. While seated, room air breathing, measurements included expiratory reserve volume (ERV), components of breathing pattern, and occlusion pressure at 1 s (P0.1). Three of nine patients who consented to muscle biopsy demonstrated granulomatous involvement on histologic examination, and Pmax values less than the group mean; however, some patients without muscle granulomas also demonstrated low Pmax values. Breathing pattern in the sarcoid patients was rapid and shallow, but not related to the degree of radiographic infiltration or respiratory elastance. Mean inspiratory flow (VT/TI), minute ventilation, and P0.1 were, in general, greater than in the control subjects, indicating an increase in central drive. There was a significant inverse correlation between FVC and P0.1, and a weak inverse relationship between ERV and P0.1. With no significant difference between group "effective impedances" (P0.1/(VT/TI)), findings indicate that in the sarcoidosis group, decreased muscle force generation was compensated for by an increase in central drive. Granulomatous infiltration may be one of many factors contributing to respiratory muscle weakness in sarcoidosis.