Assessing mental stress from the photoplethysmogram: a numerical study

Area of Science:

• Cardiovascular Physiology
• Biomedical Signal Processing
• Psychophysiology

Background:

• Mental stress poses a significant risk to cardiovascular health, contributing to coronary heart disease and triggering cardiac events.
• Current clinical practice lacks routine assessment methods for mental stress.
• Photoplethysmogram (PPG) pulse wave analysis offers a potential non-invasive method for stress monitoring.

Purpose of the Study:

• To identify specific features within the PPG pulse wave that are indicative of mental stress.
• To explore the potential of PPG signal analysis for non-invasive stress assessment.

Main Methods:

• A numerical model simulated blood pressure signals and PPG pulse waves under six levels of mental stress.
• Haemodynamic changes associated with stress were incorporated by adjusting model input parameters.
• Thirty-two PPG pulse wave features were extracted from simulated signals at brachial, radial, and temporal arteries and analyzed using the Mann-Kendall trend test.

Main Results:

• Seventeen PPG features demonstrated significant trends with increasing mental stress across at least one measurement site.
• Three features—time from pulse onset to peak, time from dicrotic notch to pulse end, and pulse rate—showed significant stress-related trends at all three arterial sites.
• The radial artery yielded a higher number of significant features (15) compared to the brachial (8) and temporal (7) arteries, suggesting site-specific sensitivity.

Conclusions:

• Identified PPG pulse wave features can potentially serve as biomarkers for monitoring mental stress in both clinical and consumer applications.
• PPG measurements at the radial artery may offer enhanced sensitivity for stress detection compared to brachial or temporal sites.
• Further in vivo validation studies are necessary to confirm the clinical utility and reliability of these findings.