Silent Hypoxia in Coronavirus disease-2019: Is it more dangerous?-A retrospective cohort study

Background Hypoxia in patients with COVID-19 is one of the strongest predictors of mortality. Silent hypoxia is characterized by the presence of hypoxia without dyspnea.. Silent hypoxia has been shown to affect the outcomes in previous studies. Research Question Are the outcomes in patients presenting with silent hypoxia different from those presenting with dyspneic hypoxia? Study design and Methods This was a retrospective study of a cohort of patients with SARS-CoV-2 infection who were hypoxic at presentation. Clinical, laboratory, and treatment parameters in patients with silent hypoxia and dyspneic hypoxia were compared. Multivariate logistic regression models were fitted to identify the factors predicting mortality. Results Among 2080 patients with COVID-19 admitted to our hospital, 811 patients were hypoxic with SpO 2 <94% at the time of presentation. 174 (21.45%) did not have dyspnea since the onset of COVID-19 symptoms. 5.2% of patients were completely asymptomatic for COVID-19 and were found to be hypoxic only on pulse oximetry. The case fatality rate in patients with silent hypoxia was 45.4% as compared to 40.03% in dyspneic hypoxic patients ( P=0 . 202 ). The odds ratio of death was 1.1 (95% CI 0.41-2.97) in the patients with silent hypoxia after adjusting for baseline characteristics, laboratory parameters, treatment, and in-hospital complications, which did not reach statistical significance ( P =0.851). Interpretation Silent hypoxia may be the only presenting feature of COVID-19. Since the case fatality rate is comparable between silent and dyspneic hypoxia, it should be recognized early and treated as aggressively. Since home isolation is recommended in patients with COVID-19, it is essential to use pulse oximetry at the home setting to identify these patients.