Characterization of the microvascular cerebral blood

27 Obstructive apnea causes periodic changes in cerebral and systemic hemodynamics, which 28 may contribute to the increased risk of cerebrovascular disease of patients with obstructive 29 sleep apnea (OSA) syndrome. The improved understanding of the consequences of an apneic 30 event on the brain perfusion may improve our knowledge of these consequences and then 31 allow for the development of preventive strategies. Our aim was to characterize the typical 32 microvascular, cortical cerebral blood flow (CBF) changes in an OSA population during an 33 apneic event. 34 Sixteen patients (age 58 ± 8 years, 75% male) with a high risk of severe OSA were 35 measured with a polysomnography device and with di use correlation spectroscopy (DCS) 36 during one night of sleep with 1365 obstructive apneic events detected. All patients were 37 later confirmed to su er from severe OSA syndrome with a mean of 83 ± 15 apneas and 38 hypopneas per hour. 39 DCS has been shown to be able to characterize the microvascular CBF ::::::::: response ::: to ::::: each 40 ::::: event :::::: with :: a :::::::::: su cient :::::::::::::::::: contrast-to-noise :::::: ratio ::: to ::::::: reveal :::: its ::::::::::: dynamics. :: It has also revealed 41 that an apnea causes a peak increase of microvascular CBF (30 ± 17 %) at the end of the 42 event followed by a drop (-20 ± 12 %) similar to what was observed in macrovascular CBF 43 velocity of the middle cerebral artery. This study paves the way for the utilization of DCS 44 for further studies on these populations. 45