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The impact of skin tone on performance of pulse oximeters used by NHS England COVID Oximetry @home scheme: measurement and diagnostic accuracy study
Arterial haemoglobin oxygen saturation (SaO2) indicates the fraction of oxygenated haemoglobin, relative to total haemoglobin, in arterial blood and provides a useful indicator of hypoxaemia (low blood oxygen levels). The gold standard measurement for SaO2 is an arterial blood sample analysed by the co-oximeter of a blood gas machine. Pulse oximetry is a technology developed to estimate SaO2 non-invasively by measuring the absorbance of two wavelengths of light (660 and 940 nm) transmitted across the vascular bed of a tissue. Differential light absorbance characteristics between oxygenated and deoxygenated haemoglobin permits the calculation of a ratio, allowing estimation of SaO2. Pulse oximetry is widely used throughout the world to monitor patients in healthcare settings and, more recently, in the community.