Performance of Wearable Pulse Oximetry During Controlled Hypoxia Induction

Oxygen saturation is a crucial metric used for monitoring patients with lung disease or respiratory illness who are at risk of hypoxemia (low blood oxygen saturation). Early and accurate identification of abnormal oxygen saturation is important for these patients who may develop significant desaturation and hypoxemia symptoms during their daily activities. To investigate the performance of two pulse oximeters during desaturation, we recruited nine healthy participants and performed a controlled oxygen desaturation study that reduces the blood oxygen saturation levels from 100% to 60% using a gas delivery system. We calculated the oxygen desaturation rate (ODR) of each measurement and conducted a comparative analysis of the displayed oxygen saturation readings from both the Masimo MightySat Rx finger pulse oximeter and Apple Watch Series 7 with arterial blood oxygen saturation readings obtained from a blood gas analyzer. Both the Masimo MightySat Rx pulse oximeter and the Apple Watch Series 7 tended to overestimate oxygen saturation. The pulse oximeter readings were more likely to fall within 2% of the acceptable (as specified by Masimo) peripheral oxygen saturation (SpO2) error range than the Apple Watch (49.03% compared to 32.14%). Notably, both devices had limitations under low oxygen saturation levels (<88%) with an accuracy root mean square difference (Arms) of 3.52 [3.18-3.86]% and 5.82 [5.32-6.31]% for the Masimo MightySat Rx and Apple Watch Series 7, respectively. Among the blood oxygen measurements taken during a high oxygen desaturation rate (ODR) (i.e., [&ge;] 2% SpO2 per minute), which is a rate clinically correlated with sleep apnea, the Arms increased slightly by 0.75% for the Masimo MightySat Rx and decreased by 0.28% for the Apple Watch Series 7. However, no statistically significant relationship was found between the oxygen desaturation rate and the device measurement errors.