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 SpO2 during pulmonary rehabilitation is recommended. This study aimed to examine the accuracy of SpO2 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 SpO2 in participants with COPD when SpO2 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.