Assessment of Noninvasive Oxygen Saturation in Patients With COPD During Pulmonary Rehabilitation: Smartwatch versus Pulse Oximeter

Background: Patients with COPD can have hypoxemia; hence, monitoring peripheral S_pO2 during pulmonary rehabilitation is recommended. This study aimed to examine the accuracy of S_pO2 readings in patients with COPD as measured by wearable devices at rest and after physical exercise.

Methods: Thirty-six participants with COPD (20 women), ages 52-89 years, participated in this cross-sectional study. Oxygen saturation was concurrently measured by using the Contec Pulse Oximeter CMS50D as a comparator, and the Apple Watch Series 7 and the Garmin Vivosmart 4 at rest and immediately after the 30-s sit-to-stand test and the 6-min walk test (6MWT).

Results: For the Apple Watch, the root mean squared error showed a deviation of 3.5% at rest, 4.1% after the 30-s sit-to-stand test, and 3.9% after the 6MWT. The level of agreement was 2.8 ± 2.4 (7.6, -1.9) at rest, 3.1 ± 2.8 (8.6, -2.3) after the 30-s sit-to-stand test, and 2.8 ± 2.9 (8.6, -2.9) after the 6MWT. For the Garmin Vivosmart, the root mean squared error showed a deviation of 3.3% at rest, 6.1% after the 30-s sit-to-stand test, and 5.4% after the 6MWT. Level of agreement was 1.9 ± 2.7 (7.2, -3.3) at rest, 2.9 ± 5.4 (13.5, -7.7) after the 30-s sit-to-stand test, and 2.3 ± 5.0 (12.1, -7.4) after the 6MWT. The limits of agreement showed considerable measurement variance and a tendency for the devices to be less accurate at lower saturation levels.

Conclusions: The Apple Watch Series 7 and Garmin Vivosmart 4 overestimated S_pO2 in participants with COPD when S_pO2 was < 95% and underestimated oxygen saturation when saturation was > 95%. These findings suggest that wearable devices should not be used to monitor oxygen saturation during pulmonary rehabilitation.