Validation of Withings ScanWatch as a Wrist-Worn Reflective Pulse Oximeter: Hypoxia Study.

BACKGROUND: A decrease in the pulse oxygen saturation (SpO2) level is an indicator of hypoxemia that may occur in various respiratory diseases such as chronic obstructive pulmonary disease (COPD), sleep apnea syndrome (SAS) and COVID-19. There is currently no mass-market wrist-worn SpO2 monitor meeting the medical standards for pulse oximeters.

OBJECTIVE: The main objective of this monocentric and prospective clinical study with single-blind analysis was to test and validate the accuracy of the Withings ScanWatch's reflective pulse oximeter function to measure SpO2 levels at different stages of hypoxia. The secondary objective is to confirm the safety of this device when used as intended.

METHODS: To achieve these objectives, we included 14 healthy participants aged 23 to 39, and we induced several stable plateaus of arterial oxygen saturation (SaO2) ranging from 100% to 70% to mimic non-hypoxic conditions and then mild, moderate, and severe hypoxic conditions. We measured the SpO2 level with a Withings ScanWatch on each participant's wrist and the SaO2 from blood samples with a co-oximeter, the ABL90 hemoximeter.

RESULTS: After removal of the inconclusive measurements, we had 275 and 244 conclusive measurements with the two ScanWatches on the participants' right and left wrists, evenly distributed among the 3 predetermined SpO2 groups: SpO2 ≤ 80%, 80% < SpO2 ≤ 90% and 90% < SpO2. We found a strong association and a high level of agreement between the measurements collected from the devices, with a high Pearson correlation coefficient (PCC) of r = 0.944 and r = 0.954 on correlation plots, a low PCC of r = 0.083 (P=.17) and r = 0.23 (P=.001) on Bland-Altman plots, a bias of 0.98% (95% CI [0.65, 1.32]) and 1.56% (95% CI [1.24, 1.87]), and a Root Mean Square Error (RMSE) of 2.97% and 3.00% from the participants' right and left hands, respectively.

CONCLUSIONS: In conclusion, the Withings ScanWatches is able to measure SpO2 levels with an adequate accuracy at a clinical grade. No undesirable effects or adverse events were reported during the study.

CLINICALTRIAL: This clinical study, "Accuracy of ScanWatch Pulse Oximeter With Profound Hypoxia" (Clinicaltrials.gov NCT04380389, https://clinicaltrials.gov/ct2/show/NCT04380389), was conducted in compliance with Good Clinical Practices (ISO 14155:2011, ICH guidelines) and the declaration of Helsinki after approval from the Institutional Review Board (IRB), Laurel Heights Panel, on March 9, 2020. (NIRB: 10-00437, N Reference: 272720 I). The selected eligible participants were informed and gave their signed consent prior to enrollment.