Study conducted by University of São Paulo compared Apple Watch Series 6 with commercial oximeter devices. Results show that oxygen saturation and heart rate reported by Apple Watch are on par with typical industry devices.
Our results indicate that Apple Watch 6 is a reliable way to obtain heart rate and SpO2 in patients with lung diseases under controlled conditions. The advance of smartwatch technology continues to improve and studies to assess accuracy and reliability in various types of disease should be carried out."Conclusion" section of the study