Inferring Cerebrovascular Changes from Latencies of Systemic and Intracranial Pulses: a Model-Based Latency Subtraction Algorithm

摘要

Changes in cerebral blood flow velocity (CBFV) pulse latency reflect pathophysiological changes of the cerebral vasculature based on the theory of pulse wave propagation. Timing CBFV pulse onset relative to ECG QRS is practical. However, it introduces confounding factors of extracranial origins for characterizing the cerebral vasculature. The present work introduces an approach of reducing confounding influences on CBFV latency. This correction approach is based on modeling the relationship between CBFV latency and systemic arterial blood pressure (ABP) pulse latency. It is tested using an existing data set of CBFV and ABP from 14 normal subjects undergoing pressure cuff tests under both normoxic and acute hypoxic states. The results show that the proposed CBFV latency correction approach produces a more accurate measure of cerebral vascular changes with an improved positive correlation between beat-to-beat CBFV and the CBFV latency time series, e.g., correlation coefficient raised from 0.643 to 0.836 for group-averaged cuff-deflation traces at normoxia. In conclusion, the present work suggests that subtraction of systemic ABP latency improves CBFV latency measurements, which in turn improves characterization of cerebral vascular changes.