Changes of Radial Pressure Pulse in Cold-Stressed Humans; A Clinical Study

Abstract

Purpose: Human body under cold stress (CS) causes physiological responses through autonomic nerve reaction (ANR); it accompanies cardiovascular changes and thus will be reflected on radial pressure pulse (RPP). This study aims to explore the effects of CS on RPP and investigate some indices which can reflect ANR. Methods: Sixty subjects participated in the study at normothermic conditions by immersing their legs into 15 ◦C water for 5minutes. RPP and respiration signals were recorded before the CS and immediately after the CS. Finally, we analyzed the pulse power, pulse depth, pulse rate (P), respiration rate (R), pulse rate per respiration (P/R ratio), heart rate variability (HRV), power spectral density (PSD) within 0∼13Hz (PSD0-13Hz) and 13∼30Hz (PSD13-30Hz). Results: Immersing legs into cold water caused pulse to be more powerful and shallower which implies the study was designed for a proper CS for humans. P/R ratio showed a consistently decreasing tendency (p<0.01) through the CS stimulation process, while heart rate generally used as a primary diagnostic indicator showed no significant difference. Other parameters behaved more complex and in subjectspecific ways. It implies that, among candidate parameters, the P/R ratio is a simple ANR indicator. In addition, PSD ratio (PSD0-13Hz/PSD13-30Hz) (p<0.01) was shown to be another potential ANR indicator. Conclusion: We studied the RPP responses through a CS clinical study and showed that the P/R ratio and PSD ratio are potentially good indicators for ANR under a CS environment. Especially, the P/R ratio was shown to be more appropriately associated with the ANR than heart rate or respiration rate alone. Further studies including clinical study for heatstressed humans will help confirm our results. Contact: Jang Han Bae, fcbest11@kiom.re.kr