Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada.
Research Unit of Internal Medicine, Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
Eur J Appl Physiol. 2018 Oct;118(10):2233-2240. doi: 10.1007/s00421-018-3957-1. Epub 2018 Aug 1.
The aim of this study was to examine the effect of passive heat stress on heart rate variability parameters in healthy children.
Fifteen children (9.3 ± 1.6 years) of both sexes (eight male) participated in two randomized experimental conditions separated by 5-12 days. Children were seated for 2 h in an environmental chamber for two sessions: neutral (22.4 ± 0.1 °C, 40.4 ± 6.5% RH) and hot (34.9 ± 0.3 °C, 36.6 ± 6.2% RH) conditions. Electrocardiogram, mean skin temperature, tympanic temperature, and blood pressure were recorded. Five min epochs were averaged for analysis of cardiac autonomic function over the 2-h protocol.
Mean skin and tympanic temperatures and heart rate increased during the hot condition (all p < 0.01) while mean arterial pressure decreased (p < 0.01). During the hot condition, root-mean-square difference of successive normal RR intervals (45 ± 9 to 38 ± 7 ms), and low- (LF, 1536 ± 464 vs. 935 ± 154 ms) and high-frequency power (HF, 1544 ± 693 vs. 866 ± 355 ms) decreased, whereas LF/HF ratio increased (1.64 ± 0.24 vs. 2.40 ± 0.23 au); all indices were different from neutral (all p < 0.05). These were all unchanged throughout the neutral condition (all p > 0.05), except for LF/HF ratio which decreased during the neutral condition (p < 0.05).
Mild hyperthermia elicited marked changes in cardiac autonomic control in young children. These data suggest that, in healthy children, vagal withdrawal is responsible for the cardiac autonomic response to hyperthermia.
本研究旨在探讨健康儿童被动热应激对心率变异性参数的影响。
15 名儿童（9.3±1.6 岁；8 名男性）参与了两项随机实验条件，间隔 5-12 天。儿童在环境室中静坐 2 小时，共进行两次：中性（22.4±0.1°C，40.4±6.5%RH）和热（34.9±0.3°C，36.6±6.2%RH）条件。记录心电图、平均皮肤温度、鼓膜温度和血压。在 2 小时的方案中，平均 5 分钟的片段用于分析心脏自主功能。
在热环境中，平均皮肤和鼓膜温度以及心率增加（均 p<0.01），而平均动脉压降低（p<0.01）。在热环境中，连续正常 RR 间期的均方根差（45±9 至 38±7 ms）、低频（LF，1536±464 至 935±154 ms）和高频功率（HF，1544±693 至 866±355 ms）降低，而 LF/HF 比值增加（1.64±0.24 至 2.40±0.23 au）；所有指数与中性条件均不同（均 p<0.05）。所有这些在中性条件下均无变化（均 p>0.05），除了 LF/HF 比值在中性条件下降低（p<0.05）。
轻度体温升高引起幼儿心脏自主控制的明显变化。这些数据表明，在健康儿童中，迷走神经传出的抑制是热应激对心脏自主神经反应的原因。
