The purpose of this study was to determine if the daytime cognitive dysfunction experienced by subjects with obstructive or mixed sleep apnea was due to sleep fragmentation or oxygen desaturation. An experimental, randomized, cross-over, test-retest design was used to evaluate 11 male subjects with obstructive sleep apnea and hypoxemia. Each subject had one week of low flow oxygen and one week of continuous positive airway pressure (CPAP) treatment or visa versa. Between each treatment there was one week without any treatment.

Subjects were evaluated using overnight polysomnographs with oximetry before and after each treatment. Neurocognitive evaluations were also done at these same intervals using the Neurobehavioral Cognitive Status Examination, Trailmaking A and B and the Benton Visual Retention Test.

Results demonstrated that low flow oxygen therapy reversed hypoxemia although the mean apnea hypopnea index (AHI) was worse and the sleep arousal index (SAI) was unchanged. The CPAP treatment reversed hypoxemia and significantly improved the AHI and SAI as can be seen below.

Apnea Hypopnea Index, Oxygen Desaturation and Sleep Arousal Index Before and After One Week Treatment (N = 11):(UNFORMATTED TABLE OR EQUATION FOLLOWS)

Results indicated that CPAP is the better treatment for obstructive sleep apnea, improving apnea, hypoxemia and arousals. After one week of treatment, CPAP improved cognitive skills in visual memory, set changes and construction. These findings suggest that cognitive disability with obstructive sleep apnea is not due to hypoxemia but related to sleep fragmentation and microarousals.