SpO2 (Blood Oxygen Saturation)

SpO2, or peripheral oxygen saturation, is a measure of the percentage of hemoglobin molecules in the blood that are carrying oxygen. Normal SpO2 levels for healthy individuals are typically between 95% and 100%. Values below 90% are generally considered clinically significant and may indicate hypoxemia, a condition where insufficient oxygen reaches the body's tissues.

Traditional SpO2 measurement uses pulse oximetry, which works by shining red and infrared light through tissue (usually a fingertip) and measuring the ratio of absorbed light. Oxygenated and deoxygenated hemoglobin absorb these wavelengths differently, enabling calculation of oxygen saturation. This same optical principle underlies both contact PPG-based and contactless rPPG-based SpO2 estimation.

Contactless SpO2 estimation using rPPG leverages multi-wavelength analysis of facial video, taking advantage of the different spectral properties of oxygenated and deoxygenated hemoglobin in visible and near-infrared light. While contactless SpO2 is intended for wellness monitoring and screening rather than clinical diagnosis, it provides a convenient way to track oxygenation trends during telehealth encounters and remote monitoring.