Sleep apnea syndromes: Impact of sleep and sleep states

Abstract

During the past decade, it has become evident not only that sleep itself but also different sleep states may have a marked effect on breathing. Sleep may reveal an abnormality of air exchange that can lead to important cardiovascular changes (sleep apnea syndromes), but it can also greatly worsen a mild daytime ventilatory problem related to a thoracic abnormality (Rizvi et al., 1974; Coccagna et al., 1975; Guilleminault and Motta 1978; Guilleminault et al., 1978a,c). The appearance of complete apnea may not be necessary, since 'hypopnea', defined as decrease in abdominal and thoracic movements and decreased airflow, is associated with a drop in oxygen saturation (Kurtz et al., 1971). These changes may be due to partial obstruction (increased effort as judged by the esophageal pressure) or to decreased central drive. The hypoxemia associated with hypopnea can result in disturbances of the cardiovascular system. This report presents some data demonstrating the impact of sleep, sleep states, and depression of the central nervous system on primary or secondary sleep apnea syndrome.