Using a forehead reflectance pulse oximeter to detect changes in sympathetic tone.

Area of Science:

• Biomedical Engineering
• Physiological Monitoring
• Emergency Medicine

Background:

• Field triage in combat and disaster zones is challenging and risky for responders.
• Massive blood loss or shock causes arterial pressure changes, activating the sympathetic system.
• Current methods may not adequately assess physiological status in extreme environments.

Purpose of the Study:

• To evaluate a forehead reflectance pulse oximeter as a sensor for detecting sympathetic tone changes.
• To assess the viability of the automated remote triage system (ARTEMIS) for battlefield and disaster use.
• To explore signal processing techniques for analyzing photoplethysmogram (PPG) data.

Main Methods:

• Collected continuous PPG waveforms using a forehead reflectance pulse oximeter during a supine-standing experiment.
• Processed raw PPG signals and derived pulse statistics (height, beat-to-beat interval) using spectral analysis (FFT, AR) in Matlab.
• Analyzed the low frequency power/high frequency power ratio to detect changes in sympathetic tone.

Main Results:

• Preliminary results indicate that relative ratio analysis of PPG signals is effective in detecting sympathetic tone changes.
• Both raw PPG data and derived pulse statistics showed changes correlating with positional changes.
• The forehead reflectance pulse oximeter demonstrated potential as a sensor for sympathetic tone monitoring.

Conclusions:

• A forehead reflectance pulse oximeter is a viable sensor for detecting sympathetic tone fluctuations.
• Relative ratio analysis of PPG signals offers a useful technique for assessing physiological changes in emergency settings.
• The ARTEMIS system shows promise for improving field triage and emergency management.