Abstract
Assessment of the cerebral blood-flow-reserve in patients with cerebrovascular diseases is extremely important in terms of making prognosis, determining treatment tactics, and controlling the revascularization outcome in the case of reconstructive interventions on the brain vessels. However, there is no easy-to-use, contactless method for either assessing the functional reserve of the cortical vascular network or intraoperative monitoring of surgical intervention. Our study aims to demonstrate feasibility of green-light imaging photoplethysmography (iPPG) to estimate cerebrovascular functional reserve in animal model of craniosurgical intervention. Custom-made iPPG system was exploited to visualize intracranial vessels in anesthetized Wistar rats (n = 15). Video frames of rat’s cortex were recorded concurrently with systemic blood pressure, end-tidal CO2, and electrocardiogram. We found that injection of dorzolamide (carbonic-anhydrase inhibitor) significantly increased the blood-pulsations amplitude in all animals by 35 ± 19% (p < 0.001). Such an increase negatively correlated with significant decrease in end-tidal CO2 by 32 ± 7% (p < 0.001). It is noteworthy that the dorzolamide injection did not lead to significant changes in systemic blood pressure. Concluding, pulsations amplitude is a marker of the vascular tone that can be used to evaluate the functional cerebrovascular reserve. Imaging PPG is a simple and convenient method to assess cerebral blood flow, including during various neurosurgical interventions.
Highlights
Optical methods are considered as very promising for noninvasive measurements of blood flow parameters
It was found that the amplitude of the pulsatile component of the PPG signal (APC) at green light is inversely related to cerebral vascular resistance, which was increasing in response to a decrease and decreasing in response to an increase in systemic arterial blood pressure (ABP)[14]
We demonstrated for the first time that imaging PPG technique made it possible to visualize cerebral blood flow and its variations through a thinned bone, without removing the dura mater and even without violating the integrity of the cranial cavity in all 15 rats under study
Summary
Optical methods are considered as very promising for noninvasive measurements of blood flow parameters. It was found that the amplitude of the pulsatile component of the PPG signal (APC) at green light is inversely related to cerebral vascular resistance, which was increasing in response to a decrease and decreasing in response to an increase in systemic arterial blood pressure (ABP)[14]. Such a behavior of APC is due to a cerebrovascular reflex aimed at maintaining the constancy of the volumetric velocity of cerebral blood flow in a changing blood pressure. The potential use of this method will be express-evaluation of the cerebrovascular reserve in different parts of the brain during neurosurgical operations
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