RESPIRATORY EFFORT - A FACTOR CONTRIBUTING TO SLEEP PROPENSITY IN PATIENTS WITH OBSTRUCTIVE SLEEP-APNEA

To test the hypothesis that respiratory effort during obstructive apne as contributes, together with hyperemia and sleep fragmentation, to ex cessive daytime sleepiness, we investigated the relationship between d aytime sleepiness and polysomnographic variables in 44 patients with o bstructive sleep apnea (OSA). In all patients, daytime sleep propensit y was assessed by an 11-item standardized self-questionnaire yielding a sleepiness score and by a modified sleep latency test yielding a mea n sleep latency. Respiratory effort during apneas was evaluated by mea suring esophageal pressure swings using an esophageal balloon. Within each apneic cycle, we measured the esophageal pressure swings during t he first three and the last three occluded efforts during the apnea to define the overall increase, its ratio to apnea duration, and the max imal effort developed during obstruction. In the group of patients as a whole, the sleepiness score was negatively correlated with the mean sleep latency (r=-0.38, p=0.01). The sleepiness score was correlated w ith the indexes of respiratory effort during apneas (ie, the overall i ncrease, its ratio to apnea duration, and the maximal end-apneic swing in esophageal pressure) and with the apnea+hypopnea index. The mean s leep latency was correlated with all indexes of nocturnal hypoxemia (i e, the mean lowest oxyhemoglobin saturation [SaO(2)] and the index of apnea associated with a fall in SaO(2) below 90% and 80%). We conclude that the degree of respiratory effort during obstructive apneas contr ibutes to self-rated sleep propensity in patients with OSA.