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

Abstract

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