Calibration of Contactless Pulse Oximetry

Area of Science:

• Biomedical Engineering
• Physiological Measurement

Background:

• Contactless photoplethysmography (PPG) uses shallower skin layers than traditional methods.
• This raises questions about the accuracy and calibration of camera-based pulse oximetry.

Purpose of the Study:

• To assess the calibratability and feasibility of camera-based contactless pulse oximetry.
• To compare remote PPG signals with reference pulse oximetry measurements.

Main Methods:

• Video recordings of adult foreheads were taken at 660 and 840 nm.
• Remote PPG signals were extracted under normoxic, hypoxic, and low-temperature conditions.
• Data were compared to reference SpO2 from contact probes.

Main Results:

• A calibration curve yielded a root mean square error of 1.15% (99% CI 1.65%) for SpO2 83-100%.
• Low temperatures caused minimal calibration error (0.1% ±1.3%).
• Individual PPG signal strengths varied significantly.

Conclusions:

• Camera-based pulse oximetry is fundamentally feasible for healthy adults, with long-term errors below ISO standards.
• Short-term errors (A**rms = 2.54%) and challenges like low signal and motion need addressing for practical use.