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 (SpO2) 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% O2), which temporarily reduced their blood oxygen saturation. In the final stabilization phase, the participants inhaled the ambient air again until SpO2 returned to normal values. Measurements of SpO2 were taken from the smartwatch and the pulse oximeter simultaneously in 30-s intervals. Results There were 642 individual pairs of SpO2 measurements. The bias in SpO2 between the smartwatch and the oximeter was 0.0% for all the data points. The bias for SpO2 less than 90% was 1.2%. The differences in individual measurements between the smartwatch and oximeter within 6% SpO2 can be expected for SpO2 readings 90%–100% and up to 8% for SpO2 readings less than 90%. Conclusions Apple Watch Series 6 can reliably detect states of reduced blood oxygen saturation with SpO2 below 90% when compared to a medical-grade pulse oximeter. The technology used in this smartwatch is sufficiently advanced for the indicative measurement of SpO2 outside the clinic. Trial Registration ClinicalTrials.gov NCT04780724

Accuracy of the Apple Watch Oxygen Saturation Measurement in Adults: A Systematic Review

“…The remaining five articles were included [2,[14][15][16][17]. A summary of extracted characteristics is available in Table 2.…”

“…All publications declared that no conflict of interest was present. Two publications declared that no funding for the project had been received [ 2 , 16 ], and one publication declared a grant from the university as a funding source [ 17 ], while the remaining two publications did not mention funding [ 14 , 15 ].…”

“…Littell and colleagues were the only author group that uploaded data to a public repository [ 16 ]. Two of the remaining publications mentioned the data being available from the corresponding author upon reasonable request [ 2 , 17 ], while the others did not mention data availability [ 14 , 15 ].…”

“…Rafl et al evaluated the performance of an Apple Watch Series 6 in 24 healthy adults that were exposed to hypoxic conditions [ 17 ]. The watch measurements were taken from the left wrist according to the manufacturer's instructions with the conventional pulse oximeter being attached to the middle finger of the same hand.…”

The Apple Watch spO2 sensor and outliers in healthy users

“…The spO 2 measurement is one of these features, and previously published studies that compare spO 2 measurements by the watch to those by a conventional, medical-grade pulse oximeter found no strong systematic bias between the two 2 – 6 .…”