OBSTRUCTIVE SLEEP APNEA: THE STATE OF CEREBRAL HEMODYNAMIC RESERVE

Abstract

Background: Individuals with obstructive sleep apnea syndrome (OSAS) have an increased risk of disabling disorders of the cardiovascular system, including stroke. The mechanisms of OSAS effects on cerebral blood flow and cerebral vascular autoregulation have not been clear enough. Aim: To study characteristics of cerebral blood flow in patients with OSAS and the effect of CPAP therapy on cerebral hemodynamic reserve. Materials and methods: One hundred and two patients with various OSAS severity (61 male and 41 female) and 20 healthy volunteers participated in the study. We performed ultrasound assessment of cerebral blood flow with functional tests and calculated reactivity indices. Results: With more severe OSAS, no significant differences in cerebral vascular reactivity compared to the control group were registered. However, there was a trend to some decrease in the index of constriction and dilation in the vertebral arteries and the basilar artery, as well as to its increase in the middle cerebral artery in severe and moderate OSAS. The index of vasomotor reactivity of cerebral arteries was significantly (р < 0.05) lower in patients with severe OSAS: for vertebral arteries, up to 38.9 ± 8.5 and for basilar artery, up to 36.8 ± 15.7, compared to the control group (52.1 ± 9.8 and 50.1 ± 11.2, respectively). In patients who initiated CPAP therapy, there were no changes in velosity, resistance and reactivity parameters of cerebral vessels after 2 months. Conclusion: We were able to confirm a significant impairment of cerebral vascular autoregulation in patients with severe OSAS, predominantly in the posterior circulatory region. CPAP-therapy of 2 months' duration did not lead to restoration of cerebral hemodynamic reserve.