Effect of continuous positive airway pressure on regional cerebral blood flow during wakefulness in obstructive sleep apnea

The alteration of regional cerebral blood flow (rCBF) during wakefulness after the treatment for obstructive sleep apnea syndrome (OSA) using continuous positive airway pressure (CPAP) has not been elucidated. The aim of this study was to investigate rCBF characteristics and the effects of nasal CPAP in OSA patients. Fifteen severe OSA patients (apnea-hypopnea index, 62.7 +/- 22.4/h), when awake, underwent Technetium-99m ethyl cysteinate dimer single photon emission computed tomography before and after CPAP treatment, and the findings were compared to those of nine healthy controls matched for age and sex. Compared to controls, patients with OSA before CPAP treatment showed a significantly lower rCBF in the frontal lobe. After the treatment, no difference in rCBF was observed between the good CPAP compliance group and the controls. In the former group, there was a positive correlation between the 3 % oxygen desaturation index on diagnostic polysomnogram and the increase of rCBF after CPAP treatment in the frontal lobe. When awake, patients with severe OSA were shown to have reversible decreases in rCBF, especially in the frontal lobe, and an appropriate CPAP treatment was thought to improve rCBF in this area. Our results support the importance of appropriate CPAP treatment for severe OSA patients.