Radial Pressure Pulse and Heart Rate Variability in Heat‐ and Cold‐Stressed Humans

Abstract

This study aims to explore the effects of heat and cold stress on the radial pressure pulse (RPP) and heart rate variability (HRV). The subjects immersed their left hand into 45°C and 7°C water for 2 minutes. Sixty healthy subjects (age 25 ± 4 yr; 29 men and 31 women) were enrolled in this study. All subjects underwent the supine temperature measurements of the bilateral forearms, brachial arterial blood pressure, HRV and RPP with a pulse analyzer in normothermic conditions, and thermal stresses. The power spectral low-frequency (LF) and high-frequency (HF) components of HRV decreased in the heat test and increased in the cold test. The heat stress significantly reduced radial augmentation index (AIr) (P < .05), but the cold stress significantly increased AIr (P < .01). The spectral energy of RPP did not show any statistical difference in 0 ~ 10 Hz region under both conditions, but in the region of 10 ~ 50 Hz, there was a significant increase (P < .01) in the heat test and a significant decrease in the cold test (P < .01). The changes in AIr induced by heat and cold stress were significantly negatively correlated with the spectral energy in the region of 10 ~ 50 Hz (SE10−50 Hz) but not in the region of 0 ~ 10 Hz (SE0−10 Hz). The results demonstrated that the SE10−50 Hz, which only possessed a small percentage in total pulse energy, presented more physiological characteristics than the SE0−10 Hz under the thermal stresses.

Evaluation of vascular wall elasticity of human digital arteries using alternating current-signal photoplethysmography

“…In the meantime, no significant influence of the cold-stress stimulation on the ΔP was observed. In this experiment, the cold-stress stimulation mainly induced vasoconstriction, raising vascular resistance without changes in heart rate 21,47. When cardiac output remains constant during cold exposure,48 the unchanged heart rate maintains the constant level of the stroke volume.…”

“…The cold exposure induces a rise in skin sympathetic nerve activity,43 reduction of endothelial nitric oxide synthase activity, and higher affinity for noradrenaline on the plasma membrane 36. These neurogenic and vascular responses lead to a vasoconstriction observed by a decrease in vascular conductance,44 an increase in the P m ,20,21,45 and reduction of cutaneous perfusion 46. Furthermore, the higher P m may be affected by the increase in myocardial oxygen demand, raising the oxygen uptake during body cooling 47.…”

“…Although the cold exposure induced the reduction of amplitudes of the PPG AC signal,46 this stimulation did not influence the arterial elasticity analysis using the ΔV/ΔV 0 index. On the contrary, some arterial stiffness parameters are influenced by vasoconstriction and vasodilation, such as the volume elastic modulus and the AIx 20,21,26,47,49…”

“…Nonetheless, PWV depends on the mean blood pressure of subjects 10,18,19. Vasodilation and vasoconstriction due to sympathetic nervous stimulation, such as heat- and cold-stress stimulations, also obviously influence the AIx 20,21. Thus, using PWV and AIx for the arterial stiffness measurement under various conditions of mean blood pressure and vascular stimulations cannot definitely indicate the arterial stiffness, due to the structural peculiarities of the arterial wall.…”

New Assessment Model of Pulse Depth Based on Sensor Displacement in Pulse Diagnostic Devices

“…Further progress has been made in pulse-signal processing and noise reduction [16–20]. In addition, studies verifying pulse characteristics of palpitation patients [21], dyspepsia and rhinitis patients [22], and cold/heat-stressed humans [23] and studies explicitly comparing pulse characteristics among the three pulse-diagnostic locations [24–26] were recently reported. All of these research activities will move up the development of objective and reliable pulse diagnostic devices.…”