THE CEREBRAL VASOMOTOR ANALYZER: A FREE, OPEN-SOURCE TOOL FOR THE ESTIMATION OF CEREBRAL CRITICAL CLOSING PRESSURE AND RESISTANCE AREA PRODUCT

Abstract

Cerebrovascular resistance/conductance indices (CVRi, CVCi) are common surrogates of cerebrovascular tone in vivo due to their ease of calculation. While a valid metric, these calculations cannot discern between changes in capillary tone or large arteriole resistance – both of which are prominent mechanisms of cerebrovascular control. Cerebral critical closing pressure (CrCP) and resistance area product (RAP) are linked to capillary and arteriole tone, respectively, proving a more physiologically relevant metric of vasomotor activity in the brain. Unfortunately, due to the computational burden required for these estimations, adoption of these metrics has been slow. Consequently, mean values of CrCP and RAP are also not established. Therefore, we aimed to develop a free, open-source application that lowers investigational burden when calculating CrCP and RAP and to establish mean sex-specific values for healthy, young adults. Using retrospective data in healthy, young adults, we compared estimations of CrCP and RAP (n = 30) generated by our application to those created by a leading expert in CrCP estimations. Lin’s concordance correlation, Bland-Altman analysis, and typical error all showed excellent agreement between methods (CrCP: ρc = 0.97, mean bias = -0.21 mmHg, limits of agreement (LoA) [-5.29, 4.88], %err = 6.35%; RAP: ρc = 0.99, mean bias = 0.06 mmHg·s·cm-1, LoA [-0.05, 0.06], %err = 2.17%). Interclass correlation (ICC, n = 32) showed perfect inter-rater reliability for all metrics (ICC: 1.0, p < 0.001). Although mean values were established for our cohort (n = 32; CrCP: 27.9 ± 11.1, RAP: 1.01 ± 0.26), there were no differences between the sexes (p > 0.05). Our application showed excellent agreement compared to expert-produced results, as well as consistency between users. Therefore, our tool can automatically produce accurate and precise estimations of CrCP and RAP while limiting human bias in these calculations. We recommend this tool for reporting CrCP and RAP in cerebrovascular research, thus increasing prevalence in the field of cerebrovascular physiology.