Agreement and Accuracy of a Commercial Pulse Oximeter Compared with Arterial Oxygen Saturation During Controlled Hypoxemia in Healthy Volunteers

Purpose: Pulse oxygen saturation (SpO 2 ) is widely used for continuous non-invasive oxygenation monitoring, but its accuracy can be affected by sensor design, probe placement, peripheral perfusion, skin pigmentation, motion artifacts, and device algorithms. This study evaluated the accuracy and agreement of a commercial pulse oximetry system (model M201 SpO 2 module, Shenzhen Witleaf Medical Electronics Co. Ltd.) with a matched fingertip sensor during non-motion controlled hypoxemia in healthy volunteers, using arterial oxygen saturation (SaO 2 ) measured by arterial blood gas/co-oximetry analysis as the reference standard. Material and Methods: Eighteen healthy volunteers underwent two phases of controlled hypoxemia. Each phase comprised three target SpO 2 plateau ranges (90– 100%, 80– 89%, and 70– 79%). Phase 1 was the desaturation phase, and Phase 2 was a re-oxygenation and repetition phase. After each target plateau stabilized, SpO 2 values from the investigational system were recorded, and paired arterial blood samples were collected for SaO 2 measurement. Measurement error was defined as SpO 2 −SaO 2 . Bias, mean absolute error (MAE), accuracy root mean square (ARMS), 95% limits of agreement (LOA), and proportions of absolute errors exceeding predefined thresholds were calculated. Results: A total of 432 paired SpO 2 –SaO 2 observations were analyzed. SpO 2 showed strong correlation with SaO 2 (Pearson r = 0.990; Spearman r = 0.986; both p < 0.001). Overall bias was − 0.061%, with 95% LOA from − 2.65% to 2.53%. MAE and ARMS were 1.05% and 1.32%, respectively. Absolute errors exceeding ± 2%, ± 3%, and ± 4% occurred in 11.57%, 2.55%, and 0% of observations, respectively. ARMS values were 1.03%, 1.19%, and 1.66% across the 90– 100%, 80– 89%, and 70– 79% platform phases, respectively, with increased error dispersion and mild SaO 2 underestimation in the 70– 79% phase. Conclusion: The commercial pulse oximetry system showed good overall agreement with reference SaO 2 during controlled hypoxemia, with an ARMS of 1.32% (well below the 4% threshold). Error dispersion increased in the 70– 79% saturation range, with mild underestimation of SaO 2 by SpO 2 . These findings support the clinical performance of this device within the tested saturation range. Keywords: pulse oximetry, SpO2, SaO2, controlled hypoxemia, co-oximetry, agreement analysis