CEREBRAL HEMODYNAMIC-CHANGES IN SLEEP-APNEA SYNDROME AND EFFECT OF CONTINUOUS POSITIVE AIRWAY PRESSURE TREATMENT

Background and Objective: A clear association among snoring, sleep apn ea, and increased risk of stroke has been shown by previous studies. H owever, the possible role played by sleep apnea in the pathogenesis of cerebrovascular disease is subject to debate. To evaluate the influen ce of hemodynamic changes caused by obstructive sleep apnea syndrome ( OSAS), we investigated cerebrovascular reactivity to hypercapnia in pa tients with OSAS. Methods: The study was performed at baseline and aft er I night and 1 month of nasal continuous positive airway pressure (n -CPAP) therapy, with patients in the waking state (8:00 to 8:30 AM and 5:30 to 6:00 PM) with transcranial Doppler ultrasonography. Cerebrova scular reactivity was calculated with the breath-holding index (BHI). Results: In the baseline condition, compared with normal subjects, pat ients with OSAS showed significantly lower BHI values in both the morn ing (0.57 versus 1.40,p < 0.0001) and the afternoon (1.0 versus 1.51, p < 0.0001). Cerebrovascular reactivity was significantly higher in th e afternoon than it was in the morning in both patients (p < 0.0001) a nd controls (p < 0.05). In patients, the BHI returned to normal values , comparable with those of control subjects, after both 1 night and 1 month of n-CPAP therapy. Conclusions: These findings suggest an associ ation between OSAS and diminished cerebral vasodilator reserve. This c ondition may be related to the increased susceptibility to cerebral is chemia in patients with OSAS, particularly evident in the early mornin g.