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 SpO2<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.

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Background: Due to the unprecedented speed of SARS-CoV-2 vaccine development, their efficacy trials and issuance of emergency use approvals and marketing authorizations, additional scientific questions remain that need to be answered regarding vaccine effectiveness, vaccination regimens and the need for booster doses. While long-term studies on the correlates of protection, vaccine effectiveness, and enhanced surveillance are awaited, studies on breakthrough infections help us understand the nature and course of this illness among vaccinated individuals and guide in public health preparedness. Methods: This observational cohort study aimed at comparing the differences in clinical, biochemical parameters and the hospitalization outcomes of 53 fully vaccinated individuals with those of unvaccinated (1,464) and partially vaccinated (231) individuals, among a cohort of 2,080 individuals hospitalized with SARS-CoV-2 infection. Results: Completing the course of vaccination protected individuals from developing severe COVID-19 as evidence by lower proportions of those with hypoxia, abnormal levels of inflammatory markers, requiring ventilatory support and death compared to unvaccinated and partially vaccinated individuals. There were no differences in these outcomes among patients who received either vaccine type approved in India. Conclusion: With a current rate of only 9.5% of the Indian population being fully vaccinated, efforts should be made to improve the vaccination rates as a timely measure to prepare for the upcoming waves of this highly transmissible pandemic. Vaccination rates of the communities may also guide in the planning of the health needs and appropriate use of medical resources.

Background and objective It has been observed that peripheral oxygen saturation (SpO 2 ) measured by pulse oximeter is consistently lower than arterial oxygen saturation (SaO 2 ) measured directly by blood gas analysis. In this study, we aimed to evaluate the correlation between SpO 2 and SaO 2 , and SpO 2 and partial pressure of oxygen (PaO 2 ), and compare the SpO 2 /FiO 2 (SF) and PaO 2 /FiO 2 (PF) ratios in patients with coronavirus disease 2019 (COVID-19). Methods In this observational study, SpO 2 was recorded and arterial blood gas analysis was performed among 70 COVID-19 patients presenting on room air (FiO 2 = 0.21). SaO 2 and PaO 2 were recorded from arterial blood gas analysis. The SF and PF ratios were then calculated. Results The strength of correlations between SpO 2 and SaO 2 , and SpO 2 and PaO 2 , were significant (p<0.001) and moderately positive [Pearson coefficient (r) = 0.68, 0.53]. SpO 2 value (85%), i.e., SF ratio (404.7 or below), was the best estimate for mild ARDS (acute respiratory distress syndrome) [PF ratio (300 or below)] with a sensitivity of 80.6% and specificity of 53%. Conclusion A pulse oximeter is a vital tool in the diagnosis and management of COVID-19. In our study, SpO 2 was found to have a positive correlation with SaO 2 and PaO 2 with acceptable sensitivity but low specificity in estimating mild ARDS. Therefore, pulse oximetry can be used as a tool for the early diagnosis of mild COVID-19 ARDS as per the given considerations and clinical correlation.