Evaluation of the Effect of Heat Exposure on the Autonomic Nervous System by Heart Rate Variability and Urinary Catecholamines

Abstract

Evaluation of the Effect of Heat Exposure on the Autonomic Nervous System by Heart RateVariability and Urinary Catecholamines: Shinji YAMAMOTO, et al. Department of Hygiene, Yamaguchi University Graduate School of Medicine-The aim of this study was to investigate the usefulness of heart rate variability (HRV) and urinary catecholamines (CA) as objective indices of heat stress effect. We examined physiological responses, subjective symptoms, HRV and urinary CA to evaluate the effect of heat exposure on the autonomic nervous system. Six healthy male students volunteered for this study. They were exposed on different days to either a thermoneutral condition at wet bulb globe temperature (WBGT) 21°C, or a heated condition at WBGT 35°C for 30 min, while seated on a chair. In the thermoneutral condition, differences of all parameters between the values before and after 30 min exposure were not statistically significant. In the heated condition, heart rate, body temperature and scores for subjective symptoms (feverishness, sweating, mood, and face flushing) significantly increased after 30 min exposure (p<0.05). Also, the high frequency component (HF%) of HRV significantly decreased and the low frequency/high frequency (LF/ HF) ratio of HRV significantly increased after 30 min exposure to the heated condition (p<0.05). There were no significant differences between the amounts of urinary CA before and after the 30 min exposures; however, the norepinephrine amount after 30 min exposure to the heated condition was significantly greater than that of the thermoneutral condition (p<0.05). The heat exposure (WBGT 35°C) induced activation of the sympathetic nervous system and a withdrawal of the parasympathetic nervous system. These findings coincide with observed changes of heart rate, body temperature and subjective symptoms. It is suggested that HRV (HF% and LF/HF ratio) and urinary norepinephrine may be useful objective indices of heat stress; HRV seems to be more sensitive to heat stress than urinary CA.

Effects of Hypoxia on Heart Rate Variability in Healthy Individuals: A Systematic Review

“…14 Furthermore, other factors may interfere with the HRV even in normoxia, such as respiratory frequency (RF), change in corporal position, 15,16 physical capacity, 17 age, 18 temperature, 19 which if not controlled may lead to conflicts in the results and undermine the interpretation of the impact of hypoxia on HR modulation. In this sense, the objective of this study is to systematically review this issue to clarify the effects of hypoxia on cardiac autonomic modulation in unacclimatized healthy young adults at rest.…”

Effects of psychological stress test on the cardiac response of public safety workers: alternative parameters to autonomic balance

“…This parameter is known as R-wave amplitude, and is related to changes on the volume of the left ventricle [4,5]. The ECG signals are mediated by the autonomic nervous system (ANS) through the sympathetic (SNS) and parasympathetic (PSNS) nervous system [6]. Thus, stimuli that influence the ANS of an individual affect its electrocardiographic signal.…”

“…The ratio of the LF to the HF areas define what is known as (autonomic) balance index (BI) of the ANS, which is influenced for states of anxiety and stress [6,10,11]. Another common way to observe the ANS behavior is through the so-called Poincare plot of the HR, which is a graph that reflects the dispersion of the data.…”

Climacteric Cardiovascular Changes Evaluated by Heart Rate Variability and Detrended Fluctuation Analysis

“…The Heart Rate Variability (HRV), obtained from RR intervals from an ECG recording, is influenced by the Autonomous Nervous System [7]. Low frequency (LF) fluctuations, identified in the range from 0.04 to 0.15 Hz, are associated with the sympathetic nervous system, whereas the high frequency (HF) fluctuations, belonging to the range from 0.15 to 0.4 Hz, are influenced by parasympathetic system [8].…”