Association Between Hypoxemia and Mortality in Patients With COVID-19

Abstract

Objective: To identify markers associated with in-hospital death in patients with coronavirus disease 2019 (COVID-19)-associated pneumonia.

Patients and methods: A retrospective cohort study was conducted of 140 patients with moderate to critical COVID-19-associated pneumonia requiring oxygen supplementation admitted to the hospital from January 28, 2020, through February 28, 2020, and followed up through March 13, 2020, in Union Hospital, Wuhan, China. Oxygen saturation (SpO₂) and other measures were tested as predictors of in-hospital mortality in survival analysis.

Results: Of 140 patients with COVID-19-associated pneumonia, 72 (51.4%) were men, with a median age of 60 years. Patients with SpO₂ values of 90% or less were older and were more likely to be men, to have hypertension, and to present with dyspnea than those with SpO₂ values greater than 90%. Overall, 36 patients (25.7%) died during hospitalization after median 14-day follow-up. Higher SpO₂ levels after oxygen supplementation were associated with reduced mortality independently of age and sex (hazard ratio per 1-U SpO₂, 0.93; 95% CI, 0.91 to 0.95; P<.001). The SpO₂ cutoff value of 90.5% yielded 84.6% sensitivity and 97.2% specificity for prediction of survival. Dyspnea was also independently associated with death in multivariable analysis (hazard ratio, 2.60; 95% CI, 1.24 to 5.43; P=.01).

Conclusion: In this cohort of patients with COVID-19, hypoxemia was independently associated with in-hospital mortality. These results may help guide the clinical management of patients with severe COVID-19, particularly in settings requiring strategic allocation of limited critical care resources.

Trial registration: Chictr.org.cn Identifier: ChiCTR2000030852.

Figure 1

Kaplan-Meier curves for in-hospital mortality by demographic and clinical data. A, Median (interquartile range [IQR]) follow-up for patients 60 years or older (n=71) was 12 days (5 to 19 days) and for those younger than 60 years (n=69) was 17 days (8 to 33 days). B, Median (IQR) follow-up for male patients (n=72) was 13 days (4 to 29 days) and for female patients (n=68) was15 days (8 to 24 days). C, Median (IQR) follow-up for patients with at least 1 comorbidity (n=69) was 14 days (6 to 32 days) and for patients without comorbidities (n=71) was 14 days (7 to 25 days). D, Median (IQR) follow-up for patients with hypertension (n=40) was 14 days (7 to 40 days) and for patients without hypertension (n=100) was 14 days (6 to 22 days).

Figure 2

Kaplan-Meier curves for in-hospital mortality by hypoxemia indices. A, Median (interquartile range [IQR]) follow-up for patients with dyspnea (n=69) was 10 days (6 to 26 days) and for those without dyspnea (n=71) was 16 days (8 to 26 days). B, Median (IQR) follow-up for patients with oxygen saturation (SpO₂) values of 90% or less (n=51) was 8 days (4 to 20 days) and for those with SpO₂ values greater than 90% (n=89) was 16 days (9 to 31 days).

Figure 3

Receiver operating characteristic curve of the oxygen saturation threshold for predicting death in patients with moderate to critical coronavirus disease 2019–associated pneumonia. AUC = area under the curve.

Figure 4

Kaplan-Meier curves for in-hospital mortality by laboratory markers. A, Median (interquartile range [IQR]) follow-up for patients with white blood cell (WBC) counts of 10×10⁹/L or higher (n=15) was 6 days (4 to 14 days) and for those with WBC counts less than 10×10⁹/L (n=121) was 15 days (8 to 29 days). B, Median (IQR) follow-up for patients with neutrophil counts of 6×10⁹/L or greater (n=40) was 12 days (5 to 37 days) and for those with neutrophil counts less than 6×10⁹/L (n=88) was 15 days (8 to 27 days). C, Median (IQR) follow-up for patients with C-reactive protein (CRP) levels of at least 27.8 mg/L (n=52) was 14 days (4 to 24 days) and for patients with CRP levels less than 27.8 mg/L (n=53) was 14 days (8 to 32 days). D, Median (IQR) follow-up for patients with D-dimer levels of 0.45 μg/mL or greater (n=42) was 18 days (8 to 40 days) and for patients with D-dimer levels less than 0.45 μg/mL (n=41) was 18 days (9 to 42 days).