Reflectance Forehead Pulse Oximetry: Effects of Contact Pressure During Walking

Steady progress has been made towards the development of a reliable wearable pulse oximeter to aid first responders in remote monitoring and triage operations. This study was undertaken to assess how varying contact pressures affects the photoplethysmographic (PPG) signal, and arterial oxygen saturation (SpO₂) and heart rate (HR) measurement errors during motion artifact inducing activity. The study revealed that contact pressures ranging from 8-12 kPa resulted in the largest PPG amplitude for a reflectance sensor attached to the forehead region above the eye, although the signal-to-noise ratio (SNR) did not improve significantly. However, SpO₂ and HR errors increased when insufficient contact pressure was applied. This information may be helpful in the design of a more robust pulse oximeter sensor for use in remote monitoring applications