1. ¹Neural Systems and Dynamics Laboratory, Department of Neurosurgery, The David Geffen School of Medicine, University of California, Los Angeles, California, USA
2. ²Biomedical Engineering Graduate Program, Henry Samueli School of Engineering and Applied Science, University of California, Los Angeles, California, USA
3. ³Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado, USA
4. ⁴Altitude Research Center, School of Medicine, University of Colorado Denver, Denver, Colorado, USA
5. ⁵School of Life Science and Technology, University of Electronic Science and Technology, Chengdu, China

Correspondence: Dr X Hu, Department of Neurosurgery, University of California, Los Angeles, 10833 Le Conte, NPI 18-240, Los Angeles, CA 90095, USA. E-mail: xhu@mednet.ucla.edu

Received 7 August 2008; Revised 4 December 2008; Accepted 5 December 2008; Published online 14 January 2009.

Abstract

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 electrocardiogram QRS is practical. However, it introduces confounding factors of extracranial origins for characterizing the cerebral vasculature. This study introduces an approach to 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, for example, correlation coefficient increased from 0.643 to 0.836 for group-averaged cuff deflation traces at normoxia. In conclusion, this study suggests that subtraction of systemic ABP latency improves CBFV latency measurements, which in turn improve the characterization of cerebral vascular changes.