Low-Oxygen-Saturation Quantification in Human Arterial and Venous Circulation

Conventional pulse oximetry has limited accuracy in measuring blood oxygen saturation in low-saturation and -perfusion scenarios. This limits the application of pulse oximetry in patients suffering from peripheral vascular afflictions. We present a novel pulse oximetry system that proposes solutions to these low-saturation and -perfusion scenarios by inducing an artificial pulse in the detected photoplethysmograph (PPG). A novel arteriovenous hypothesis was formulated to extract arterial and venous saturation data from the artificial PPG using arterial-to-venous compliance ratios. Sensor wavelengths were selected to provide high- and low-saturation accuracy, followed by an in vitro sensor calibration procedure. System performance was validated by means of an in vivo procedure. In vivo results indicate good accuracy for high saturation, with limited accuracy in low-saturation scenarios. The arteriovenous hypothesis was validated, indicating that venous saturation can be extracted from the artificial PPG. The results indicate that the proposed system might be able to accurately monitor arterial and venous saturation in low- or no-perfusion scenarios. It is recommended that further studies into the system´s performance are conducted.