Commercial smartwatch with pulse oximeter detects short-time hypoxemia as well as standard medical-grade device: Validation study

OBJECTIVE: We investigated how a commercially available smartwatch that measures peripheral blood oxygen saturation (SpO(2)) can detect hypoxemia compared to a medical-grade pulse oximeter. METHODS: We recruited 24 healthy participants. Each participant wore a smartwatch (Apple Watch Series 6) on the left wrist and a pulse oximeter sensor (Masimo Radical-7) on the left middle finger. The participants breathed via a breathing circuit with a three-way non-rebreathing valve in three phases. First, in the 2-minute initial stabilization phase, the participants inhaled the ambient air. Then in the 5-minute desaturation phase, the participants breathed the oxygen-reduced gas mixture (12% O(2)), which temporarily reduced their blood oxygen saturation. In the final stabilization phase, the participants inhaled the ambient air again until SpO(2) returned to normal values. Measurements of SpO(2) were taken from the smartwatch and the pulse oximeter simultaneously in 30-s intervals. RESULTS: There were 642 individual pairs of SpO(2) measurements. The bias in SpO(2) between the smartwatch and the oximeter was 0.0% for all the data points. The bias for SpO(2) less than 90% was 1.2%. The differences in individual measurements between the smartwatch and oximeter within 6% SpO(2) can be expected for SpO(2) readings 90%–100% and up to 8% for SpO(2) readings less than 90%. CONCLUSIONS: Apple Watch Series 6 can reliably detect states of reduced blood oxygen saturation with SpO(2) below 90% when compared to a medical-grade pulse oximeter. The technology used in this smartwatch is sufficiently advanced for the indicative measurement of SpO(2) outside the clinic. TRIAL REGISTRATION: ClinicalTrials.gov NCT04780724