The Presence of Ambulatory Hypoxia as an Early Predictor of Moderate to Severe COVID-19 Disease

Background The importance of ambulatory hypoxia without resting hypoxia in COVID-19 is unknown. Ambulatory hypoxia without resting hypoxia may help objectively identify high-risk patients hospitalized with COVID-19. Interventions may be initiated earlier with sufficient lead-time between development of ambulatory hypoxia and other outcome measures. Methods We performed a retrospective study of adult patients hospitalized with COVID-19 from March 1, 2020 to October 30, 2020 in ten hospitals in an integrated academic medical system in the Chicagoland area. We analyzed patients who had daily ambulatory oximetry measurements, excluding patients who had first ambulatory oximetry measurements after the use of oxygen therapies (nasal cannula or advanced oxygen therapies). We determined the association of ambulatory hypoxia without resting hypoxia with the eventual need for nasal cannula or advanced oxygen therapies (defined as high flow nasal cannula, Bi-PAP, ventilator, or extracorporeal membrane oxygenation). We also calculated the time between development of ambulatory hypoxia and the need for oxygen therapies. Results Of 531 patients included in the study, 132 (24.9%) had ambulatory hypoxia. Presence of ambulatory hypoxia was strongly associated with subsequent use of nasal cannula (OR 4.8, 95% CI 2.8 – 8.4) and advanced oxygen therapy (IRR 7.7, 95% CI 3.4 – 17.5). Ambulatory hypoxia preceded nasal cannula use by a median 12.5 hours [IQR 3.25, 29.25] and advanced oxygenation therapies by 54 hours [IQR 25, 82]. Conclusion Ambulatory hypoxia without resting hypoxia may serve as an early, non-invasive physiologic marker for the likelihood of developing moderate to severe COVID-19 and help clinicians triage patients and initiate earlier interventions.