Cerebral blood flow (CBF) response to orthostatic stress in patients with obstructive sleep apnea (OSA)

Background: In OSA patients the impairment of cerebrovascular reactivity (CVR) likely contributes to the increased incidence of stroke. The technique "Diffuse Correlation Spectroscopy" (DCS) allows non-invasive, continuous measurements of the microvascular cerebral 1,2, blood flow to evaluate CVR. Objective: The aim of the study was to evaluate the effect of orthostatic stress in relative cerebral blood flow (rCBF) measured by DCS in OSA patients. Method: We utilized a modified version of a protocol involving orthostatic stress induced by head-of-bed positioning, used in acute ischemic stroke patients 2 and a cohort of healthy subjects 1 . Cerebral hemodynamics were monitored by DCS for 5 min at the following postures: head-of-bed angle 0o to 30o to 0o to 20o to −8o to 0o. Results: 57 OSA patients were included: mean age: 55 (10) years; mean body mass index (BMI): 31 (6) kg/m 2 . The mean AHI was 39 (33) and the mean nighttime SpO 2 : 93(2,5) %. At 0o to 30o, mild OSA patients showed a similar rCBF response , -18 (9,5)%, as previous data published in healthy subjects 1 .Severe OSA presented lower but not significant rCBF (%) change, -15(10,8)%. There was a significant correlation between rCBF (%) change at 0o to 30owith mean SpO 2 % (r: 0,29; p=0,03) and with BMI (r:- 0,3; p=0,025). Conclusions: These preliminary results suggest an impairment cerebral vascular reactivity in severe OSA patients related with obesity and oxygen saturation. Diffuse optical techniques may allow noninvasive assessment of the involvement of the cerebral microvasculature. 1) B. L. Edlow et al, Physiological Meas 2010. 2) T. Durduran et al, Optics Express 2009. This work was funded by SOCAP ( 2011) and SEPAR (2012).