The severe compromise of daytime alertness that accompanies OSAS has a profound impact on the patient’s ability to function on a daily basis. This accounts for the fact that the most prevalent presenting complaint for OSAS is EDS. While the potential cardiopulmonary complications associated with this syndrome have severe long-term implications, the impact of EDS on the economic, social, and emotional life of the patient is immediate and often debilitating. One dramatic consequence of EDS is the elevated risk of automobile accidents. Thus, evaluation of the efficacy of treatments for OSAS should carefully address both the nocturnal and daytime aspects of this condition. Several therapies have been utilized to treat OSAS, including tracheostomy, UPPP, and CPAP. An objective measure of daytime sleepiness, the Multiple Sleep Latency Test, is a reliable instrument for gauging the effectiveness of these various treatments in alleviating the EDS associated with OSAS. website
While these studies have shown that alertness is recovered in OSAS patients treated with CPAP and UPPP, there are no studies, to our knowledge, assessing the time course of this recovery. However, there are data regarding the recovery of alertness following sleep loss. Some investigators view the EDS in OSAS as being due to a functional sleep loss, ie, sleep is fragmented by frequent arousals associated with apnea, which has an effect on alertness comparable to that of sleep deprivation. Thus, it is likely that, like sleep loss, OSAS will also produce a chronic sleep debt. As regards recovery of alertness, one study found that two 8-h sleep periods were required before normal subjects levels of alertness returned to baseline following two nights of sleep deprivation. Two other studies examined the effects of extending time in bed by 2 h on levels of daytime alertness in normal subjects with no complaint of daytime sleepiness. Subjects were measured after one, three, and six nights of extended sleep. The MSLT scores continued to progressively improve across time, suggesting that even a nominal sleep debt is not quickly reversed.
CPAP is the treatment of choice for OSAS because it is highly effective, safe, and noninvasive. Establishing a correct pressure of CPAP pressure immediately eliminates all of the nocturnal characteristics of OSAS, including the repetitive cessation of breathing and the affiliated hypoxemia and cardiac arrhythmias. The associated EEC arousals are also instantly eliminated, producing normal sleep staging. In view of the importance of the symptom of daytime somnolence, an issue of critical interest is the time course relation between the resolution of severely fragmented sleep and the accompanying EDS.