Session PC1.8

Probability Trends in the Assessment of Cardiovascular Autonomic Fluctuations during Cold Pressor Tests

F Ng, S Wong*, P Gomis, J Lim,
G Passariello, JM Ansermino

University of British Columbia
Vancouver, BC, Canada

The Cold Pressor Test (CPT) is a well known instrument capable of inducing a reproducible sympathetic activation by way of nociceptive and temperature receptors. Heart Rate Variability (HRV) analysis has been widely used to interpret autonomic activity but its clinical utility is limited when acute and transient phenomena are assessed. To overcome this limitation we propose a probabilistic method to analyze brief changes in the sympathovagal balance during autonomic provocative tests. Eighteen healthy volunteers between 23 and 53 years of age (mean age 35 ± 9.8 years) were exposed to CPT while continuous ECG recordings were collected. CPT ended after 180 seconds or when the subject was no longer able to tolerate the discomfort. HRV parameters, including root mean square of successive differences (RMSSD) and low frequency (LF) and high frequency (HF) components, were obtained during baseline and each stage of CPT using an autoregressive (AR) model with Burg’s method to evaluate short windows of observation while preserving adequate frequency resolution. HRV parameters obtained during immersion of the hand in cold water, after withdrawal, and every 3 minutes after withdrawal were compared to baseline parameters. A probability trend was updated every 10 seconds for each parameter and p < 0.05 was considered significant. Preliminary results show that probability trends from RMSSD and HF provide consistent and prompt information about the sympathetic activation. These findings have importance in the setting of critical care monitoring where sympathovagal imbalances can provide an early warning of physiological stress and thus facilitate timely interventions.

(Abstract Control Number: 173)