Whole body heating significantly reduced dynamic baroreflex regulation of heart rate within the high-frequency range compared to normothermic conditions (0.54 vs 1.04 beats/min/mmHg; P<0.001).
Does whole body heating alter dynamic baroreflex regulation of heart rate in humans?
Whole body heating reduces high-frequency dynamic baroreflex regulation of heart rate, which may contribute to reduced orthostatic tolerance during heat stress.
Absolute Event Rate: 0.54% vs 1.04%
p-value: p=<0.001
The purpose of this project was to identify whether dynamic baroreflex regulation of heart rate (HR) is altered during whole body heating. In 14 subjects, dynamic baroreflex regulation of HR was assessed using transfer function analysis. In normothermic and heat-stressed conditions, each subject breathed at a fixed rate (0. 25 Hz) while beat-by-beat HR and systolic blood pressure (SBP) were obtained. Whole body heating significantly increased sublingual temperature, HR, and forearm skin blood flow. Spectral analysis of HR and SBP revealed that the heat stress significantly reduced HR and SBP variability within the high-frequency range (0.2-0.3 Hz), reduced SBP variability within the low-frequency range (0.03-0.15 Hz), and increased the ratio of low- to high-frequency HR variability (all P < 0.01). Transfer function gain analysis showed that the heat stress reduced dynamic baroreflex regulation of HR within the high-frequency range (from 1.04 +/- 0.06 to 0.54 +/- 0.6 beats. min(-1). mmHg(-1); P < 0.001) without significantly affecting the gain in the low-frequency range (P = 0.63). These data suggest that whole body heating reduced high-frequency dynamic baroreflex regulation of HR associated with spontaneous changes in blood pressure. Reduced vagal baroreflex regulation of HR may contribute to reduced orthostatic tolerance known to occur in humans during heat stress.
Crandall et al. (Wed,) reported a other. Whole body heating vs. Normothermic conditions was evaluated on Dynamic baroreflex regulation of heart rate within the high-frequency range (transfer function gain) (p=<0.001). Whole body heating significantly reduced dynamic baroreflex regulation of heart rate within the high-frequency range compared to normothermic conditions (0.54 vs 1.04 beats/min/mmHg; P<0.001).