Emerging Technology for Noninvasively Measuring Oxygen Saturations.

Abstract

Measurement of blood oxygen saturation (Spo₂) and tissue oxygenation (Sto₂) is routinely performed in clinical practice. Arterial blood gas analysis, although considered the gold standard for Spo₂ estimation, requires arterial puncture, trained personnel, and laboratory backup. Currently, there is a lack of universally accepted and widely used methods for Sto₂ measurement. Available noninvasive methods for Spo₂ and Sto₂ estimation have several limitations. Many technologies are under development to address this unmet clinical need. Currently marketed oximeters for the measurement of Spo₂ are based on optics-based technologies. They typically use red or infrared light spectra. Apart from the red-infrared spectra, attempts have been made using white light, incorporating artificial intelligence and image analysis captured by a camera for the noninvasive percutaneous measurements of blood oxygen. Several techniques are available for Sto₂ measurement based on chemical, optical, or nuclear-magnetic principles. Their use is mostly limited to specific clinical settings such as oncology, wound healing, or cerebral oxygen assessment. Emerging technologies with use of green light have shown preliminary potential and are under clinical development. Optics-based technologies have shown the most promise for noninvasive measurement of oxygen in arterial blood or at the tissue level. Both red-infrared as well as blue-green light spectra are absorbed by melanin, oxyhemoglobin, and deoxyhemoglobin. Thus, these optics-based methods have the intrinsic limitation of skin tone (melanin) confounding their effect. Accuracy for these measurements could be enhanced following incorporation of a correction factor for the absorption of the light by skin melanin.