Diurnal Change of Respiratory Muscle Strength in Patients with Sleep-disordered Breathing

Background: Obstructive sleep apnea is characterized by repetitive pharyngeal collapse,which increases inspiratory resistive load, and causes intermittent oxygendesaturation and frequent arousals during sleep. This could be damaging torespiratory muscles and result in their weakness. Therefore, we investigatedrespiratory muscle strength before and after nocturnal sleep in patients withsleep-disordered breathing (SDB).Methods: Forty eight male patients with SDB undergoing overnight polysomnographywere enrolled. Maximal expiratory pressure (MEP) and maximal inspiratorypressure (MIP) were measured before and after the sleep study. Correlationbetween polysomnographic data and diurnal changes in maximal respiratorypressures were also assessed.Results: After nocturnal sleep, MEP increased from 94.6