Sleep Apnea Syndrome and Other Ventilatory Disturbances

Abstract

Sleep apnea syndrome is characterized by recurrent cessations or substantial reductions of airflow in nose and mouth during sleep. In some patients the cessations (apneas) or reductions (hypopneas) occur because the upper airway is repeatedly sucked closed with inspiratory effort during sleep. In others, airflow may be reduced because of decreased ventilatory effort. Apneas and hypopneas with decreased or absent ventilatory effort are called non-obstructive or central, those with ongoing substantial effort obstructive. Sometimes, during an apnea there is initially no ventilatory effort, but then as the apnea continues ventilatory effort occurs before airflow resumes. This third type of apnea is called mixed. Often, patients with sleep apnea syndrome have more than one type of apnea. Commonly, both apneas and hypopneas occur in the same patient during a typical sleep period. Hypoxia, hypercarbia, or increased ventilatory effort alone trigger arousals and associated resumptions of air flow. These arousals, even when they last only a few seconds, disrupt sleep architecture, contributing to the nonrestorative quality of sleep in patients with sleep apnea syndrome.