Rationale: Oxygen saturation to fraction of inspired oxygen ratio (SpO2/FiO2) has been described as potential predictor of poor outcome for COVID-19, without considering its time-varying behavior though.
Methods: Prognostic value of SpO2/FiO2 was evaluated by jointly modeling the longitudinal responses of SpO2/FiO2 and time-to-event data retrieved from 280 severe and critically ill (intensive care) patients with COVID-19.
Results: A sharply decrease of SpO2/FiO2 from the first to second measurement for non-survivors was observed, and a strong association between square root SpO2/FiO2 and mortality risk was demonstrated, with a unit decrease in the marker corresponding to 1.82-fold increase in mortality risk (95% CI: 1.56-2.13).
Conclusions: The current study suggested that SpO2/FiO2 could serve as a non-invasive prognostic marker to facilitate early adjustment for treatment, thus improving overall survival.
Keywords: COVID-19; Joint model; Prognostic marker; SpO2/FiO2.