Abstract
.Obstructive apnea causes periodic changes in cerebral and systemic hemodynamics, which may contribute to the increased risk of cerebrovascular disease of patients with obstructive sleep apnea (OSA) syndrome. The improved understanding of the consequences of an apneic event on the brain perfusion may improve our knowledge of these consequences and then allow for the development of preventive strategies. Our aim was to characterize the typical microvascular, cortical cerebral blood flow (CBF) changes in an OSA population during an apneic event. Sixteen patients (age , 75% male) with a high risk of severe OSA were measured with a polysomnography device and with diffuse correlation spectroscopy (DCS) during one night of sleep with 1365 obstructive apneic events detected. All patients were later confirmed to suffer from severe OSA syndrome with a mean of apneas and hypopneas per hour. DCS has been shown to be able to characterize the microvascular CBF response to each event with a sufficient contrast-to-noise ratio to reveal its dynamics. It has also revealed that an apnea causes a peak increase of microvascular CBF () at the end of the event followed by a drop () similar to what was observed in macrovascular CBF velocity of the middle cerebral artery. This study paves the way for the utilization of DCS for further studies on these populations.
Highlights
Obstructive sleep apnea (OSA) is characterized by the intermittent and repetitive collapse of the upper airway during sleep with simultaneous respiratory effort
The microvascular cerebral blood flow (CBF) during the whole night of sleep was continuously assessed by diffuse correlation spectroscopy (DCS) with a range of 0.9 to 3.1 (1.5 Æ 0.5, mean Æ standard deviation) second time-resolution in order to maximize the signal-to-noise ratio
We have demonstrated the successful assessment of microvascular CBF during individual obstructive apneic events by noninvasive, continuous DCS measurements
Summary
Obstructive sleep apnea (OSA) is characterized by the intermittent and repetitive collapse of the upper airway during sleep with simultaneous respiratory effort. The apnea-induced changes of cerebral hemodynamics have been studied and characterized by several groups through the measurement of the cerebral blood flow velocity (CBFV) in the middle cerebral artery by transcranial Doppler (TCD).[10,11,12,13,14] In Bålfors and Franklin[10] study, both CBFV and the mean arterial blood pressure showed a biphasic pattern, where during the apnea a gradual increase of both CBFV and mean arterial blood pressure was observed followed by a sudden drop after the end of the apneic event. Few studies have used microvascular cerebral blood oxygenation measured by near-infrared diffuse optical spectroscopy (NIRS-DOS) as a surrogate.[15,16,17,18]
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