Effects of chronic electrical stimulation on paralyzed expiratory muscles

Following spinal cord injury, the expiratory muscles develop signif-icant disuse atrophy characterized by reductions in their weight, fiber cross-sectional area, and force-generating capacity. We determined the extent to which these physiological alterations can be prevented with electrical stimulation. Because a critical function of the expira-tory muscles is cough generation, an important goal was the mainte-nance of maximal force production. In a cat model of spinal cord injury, short periods of high-frequency lower thoracic electrical spinal cord stimulation (SCS) at the T10 level (50 Hz, 15 min, twice/day, 5 days/wk) were initiated 2 wk following spinalization and continued for a 6-mo period. Airway pressure (P)-generating capacity was determined by SCS. Five acute, spinalized animals served as controls. Compared with controls, initial P fell from 43.9 1.0 to 41.8 0.7 cmH2O (not significant) in the chronic animals. There were small reductions in the weight of the external oblique, internal oblique