Photoplethysmographic Waveform in Hyperbaric Environment

Area of Science:

• Physiology
• Biomedical Engineering
• Hyperbaric Medicine

Background:

• The photoplethysmographic (PPG) signal reflects cardiovascular changes.
• Understanding PPG signal behavior in extreme environments like hyperbaric chambers is crucial for monitoring physiological responses.

Purpose of the Study:

• To identify significant morphological variations in the PPG signal during exposure to increased atmospheric pressure.
• To investigate the relationship between hyperbaric exposure and PPG signal parameters.

Main Methods:

• Recorded PPG signals from 26 subjects exposed to pressures up to 5 atm in a hyperbaric environment.
• Analyzed 4-minute PPG segments from basal (1 atm) and hyperbaric states (3 atm descending, 5 atm, 3 atm ascending, 1 atm ascending).
• Extracted six morphological parameters: pulse width, amplitude, anacrotic and catacrotic phase widths, and upward/downward slopes.

Main Results:

• Significant increases observed in PPG pulse width parameters, particularly the anacrotic phase width, across all analyzed hyperbaric states.
• Significant decreases noted in PPG signal amplitude and pulse slopes, especially during prolonged exposure (1 atm ascending state).
• PPG width rapidly responded to pressure increases, suggesting sympathetic system activation.

Conclusions:

• Hyperbaric pressure significantly alters PPG signal morphology, with pulse width being a sensitive indicator of acute pressure changes and sympathetic response.
• Prolonged hyperbaric exposure leads to decreased PPG amplitude and slopes, indicating potential physiological adaptations or stress.
• PPG analysis offers a valuable, non-invasive tool for monitoring cardiovascular adjustments in hyperbaric environments.