Genioglossus fatigue in obstructive sleep apnea

Obstructive sleep apnea (OSA) is a prevalent disorder that may cause cardiovascular disease and fatal traffic accidents but the pathophysiology remains incompletely understood. Increased fatigability of the genioglossus (the principal upper airway dilator muscle) might be important in OSA pathophysiology but the existing literature is uncertain. We hypothesized that the genioglossus in OSA subjects would fatigue more than in controls. In 9 OSA subjects and 9 controls during wakefulness we measured maximum voluntary tongue protrusion force (Tpmax). Using surface electromyography arrays we measured the rate of decline in muscle fiber conduction velocity (MFCV) during an isometric fatiguing contraction at 30% Tpmax. The rate of decline in MFCV provides an objective means of quantifying localized muscle fatigue. Linear regression analysis of individual subject data demonstrated a significantly greater decrease in MFCV in OSA subjects compared to control subjects (29.2 ± 20.8% [mean ± SD] versus 11.2 ± 20.8%; p = 0.04). These data support increased fatigability of the genioglossus muscle in OSA subjects which may be important in the pathophysiology of OSA.

► We measure muscle fiber conduction velocity (MFCV) of the human genioglossus. ► The MFCV decline during an isometric contraction is a measure of fatigue. ► We show a significantly greater decrease in MFCV in OSA versus control subjects. ► These data suggest increased fatigability of the genioglossus in OSA subjects.