Title: Variations in cardiac associated sympathovagal oscillations under short-term heat exposure

Authors: Kumari Akanksha; Rahul Kumar; Nitya Garg; Yogender Aggarwal; Rakesh Kumar Sinha

Addresses: Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Jharkhand, India ' Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Jharkhand, India ' Sarala Birla University, Ranchi, Jharkhand, 835103, India ' Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Jharkhand, India ' Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Jharkhand, India

Abstract: Heat stress results in significant cardiovascular adjustments for temperature regulation through heat dissipation. The body employs autonomic and behavioural responses mediated by autonomic nervous system (ANS) to prevent hyperthermia. Therefore, the present study aimed to examine the ANS oscillations to significant heat stress stimuli. Digital lead-II electrocardiogram (ECG) and pulse plethysmogram (PPG) were recorded from control and heat-stressed groups under anesthetised conditions. Tachograms were generated from both ECG and PPG signals. The fast Fourier transform (FFT) was used to analyse the bands using Kubios 3.5.0 software. An unpaired t-test and Bland-Altman test were employed to compare the differences between the two groups. The results demonstrated a significant shift of oscillations toward sympathetic dominance with the withdrawal of parasympathetic activity under heat exposure. The LF oscillations increased and exhibited strong associations between HRV and PRV parameters under the heat stress group. PRV and HRV assess the ANS oscillations and aided with valuable insights into cardiac autonomic function.

Keywords: autonomic nervous system; ANS; fast Fourier transform; FFT; heat exposure; heart rate variability; HRV; pulse rate variability; PRV; sympathovagal balance.

DOI: 10.1504/IJBET.2025.149316

International Journal of Biomedical Engineering and Technology, 2025 Vol.48 No.4, pp.393 - 407

Received: 02 Dec 2024
Accepted: 20 Mar 2025
Published online: 24 Oct 2025 *

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