Study of cerebrovascular reactivity to hypercapnia by imaging photoplethysmography to develop a method for intraoperative assessment of the brain functional reserve

Abstract

Intraoperative assessment of cerebrovascular reactivity is a relevant problem of neurosurgery. To assess the functional reserve of cerebral blood flow, we suggest using imaging photoplethysmography for measuring changes in cortical perfusion caused by CO2 inhalation. Feasibility of the technique was demonstrated in three groups of anesthetized rats (n=21) with opened and closed cranial windows. Our study for the first time revealed that the hemodynamic response to hypercapnia strongly depends on the cranial state. However, it was shown that regardless of the direction of changes in local and systemic hemodynamics, the ratio of normalized changes in arterial blood pressure and cortical perfusion could be used as a measure of the cerebrovascular functional reserve.

Duality in response of intracranial vessels to nitroglycerin revealed in rats by imaging photoplethysmography

“…In a simplified sense, a decrease in the tone of the vascular wall should be accompanied by an increase in APC, whereas an increase in tone should lead to a decrease in APC 53 . The results of studies carried out by our group using both unconditional vasodilating agents, such as CO 2 41 or the carbonic anhydrase inhibitor dorzolamide 40 , and neurogenic dural vasodilation 42 fully confirm such a performance.…”

“…We have recently shown that a multimodal approach using imaging photoplethysmography (iPPG) at green illumination synchronized with the electrocardiogram (ECG) can serve as a reliable tool for studying intracranial blood flow in rats under various experimental conditions 39 – 41 . In particular, we identified new optical markers of trigeminal afferents activation and determined their sensitivity 42 to valproic acid and sumatriptan, two clinically effective drugs for preventive and abortive migraine treatment, respectively 43 .…”

Novel Method to Assess Endothelial Function via Monitoring of Perfusion Response to Local Heating by Imaging Photoplethysmography

“…In contrast, the method of imaging PPG (iPPG) has recently become increasingly used to estimate tissue perfusion in vivo, allowing for the quantification of the spatial distribution of the blood flow parameters [ 28 , 29 ]. Moreover, it was recently shown that iPPG allows for the assessment of the local distribution of arterial vascular tone [ 30 ], as well as vascular resistance [ 31 ].…”