Photoplethysmographic Waveform and Pulse Rate Variability Analysis in Hyperbaric Environments

Area of Science:

• Physiological responses to extreme environments
• Cardiovascular system dynamics
• Biomedical signal analysis

Background:

• Hyperbaric environments can significantly impact physiological functions.
• Understanding Autonomic Nervous System (ANS) responses is crucial in extreme conditions.
• Photoplethysmogram (PPG) signals offer insights into cardiovascular changes.

Purpose of the Study:

• To investigate alterations in PPG signal morphology under hyperbaric conditions.
• To analyze Pulse Rate Variability (PRV) for characterizing Autonomic Nervous System (ANS) response.
• To assess the suitability of PPG for monitoring physiological changes in hyperbaric settings.

Main Methods:

• 28 volunteers were exposed to sequential hyperbaric stages (1-5 atm).
• Nineteen morphological parameters of the PPG signal were analyzed.
• Time and frequency domain parameters of PRV were computed.

Main Results:

• Significant widening of pulse width and increased PPG area were observed with increasing pressure.
• PPG morphology changes suggest peripheral vasoconstriction and sympathetic activation.
• PRV analysis indicated augmented parasympathetic activity and reduced sympathetic response parameters.

Conclusions:

• PPG morphology changes reflect peripheral sympathetic activation in hyperbaric environments.
• Conflicting signals from PPG morphology and PRV analysis suggest a complex ANS response.
• PPG is a suitable tool for studying physiological responses in hyperbaric conditions, even in wet environments.