Abstract
This is a comparative study of two novel noninvasive cerebrovascular autoregulation (CA) monitoring methods based on intracranial blood volume (IBV) changes in the human brain. We investigated the clinical applicability of the new volumetric reactivity index (VRx2), reflected by intracranial ultrasonic attenuation dynamics for noninvasive CA monitoring. The CA was determined noninvasively on 43 healthy participants by calculating the volumetric reactivity index (VRx1 from time-of-flight of ultrasound, VRx2 from attenuation of ultrasound). The VRx was calculated as a moving correlation coefficient between the arterial blood pressure and noninvasively measured IBV slow waves. Linear regression between VRx1 and VRx2 (averaged per participants) showed a significant correlation (r = 0.731, p < 0.0001, 95% confidence interval [0.501–0.895]) in data filtered by bandpass filtering. On the other hand, FIR filtering demonstrated a slightly better correlation (r = 0.769, p < 0.0001, 95% confidence interval [0.611–0.909]). The standard deviation of the difference by bandpass filtering was 0.1647 and bias −0.3444; and by FIR filtering 0.1382 and bias −0.3669. This comparative study showed a significant coincidence of the VRx2 index compared to that of VRx1. Hence, VRx2 could be used as an alternative, cost-effective noninvasive cerebrovascular autoregulation index in the same way as VRx1 values are used.
Highlights
The mechanisms of cerebral autoregulation remain poorly understood, especially in humans.Cerebrovascular autoregulation refers to the brain’s ability to maintain constant cerebral blood flow (CBF) with changes in cerebral perfusion pressure (CPP) [1] based on cerebral metabolism independent of fluctuations in systemic arterial blood pressure (ABP)
Before slow wave filtering, hyperventilation and breath-holding tests were performed for vasoconstriction and vasodilation dynamics for a few seconds to determine if both channels reacted to the physiology in the same way, when arterial blood pressure (ABP) was the same
Hyperventilation and breath-holding tests were performed for vasoconstriction and vasodilation dynamics for a few seconds by time-of-flight and attenuation ultrasonic noninvasive Cerebral autoregulation (CA) monitoring
Summary
Cerebrovascular autoregulation refers to the brain’s ability to maintain constant cerebral blood flow (CBF) with changes in cerebral perfusion pressure (CPP) [1] based on cerebral metabolism independent of fluctuations in systemic arterial blood pressure (ABP). This process is controlled by multifactor mechanisms, including myogenic, metabolic, and neurogenic metabolic mechanisms [2,3,4]. Cerebral autoregulation (CA) is the primary factor that influences treatment outcomes in brain trauma patients [5,6]. When CA is impaired, the outcomes for traumatic brain injury (TBI) patients are significantly impacted. Autoregulation has been described as a balancing act between vasoconstriction and vasodilation because the resistance of the cerebrovascular bed accepts slow dynamic changes
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