Caution against precaution: A case report on silent hypoxia in COVID-19

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 characterised by the presence of hypoxia without dyspnoea. Silent hypoxia has been shown to affect the outcome in previous studies.

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 dyspnoeic 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. Among them, 174 (21.45%) did not have dyspnoea since the onset of COVID-19 symptoms. Further, 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 dyspnoeic 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).

Conclusion

Silent hypoxia may be the only presenting feature of COVID-19. As the case fatality rate is comparable between silent and dyspnoeic hypoxia, it should be recognised early and treated as aggressively. Because home isolation is recommended in patients with COVID-19, it is essential to use pulse oximetry in the home setting to identify these patients.

Predictors and clinical outcomes of silent hypoxia in COVID-19 patients, a single-center retrospective cohort study

Background

Patients with COVID-19 usually present with fever and respiratory symptoms such as cough, sputum production, and dyspnea. However, they may suffer from severe hypoxemia without a clinical correlation with the respiratory symptoms, also known as silent or apathetic hypoxia. The aim of the study was to assess the predictors and clinical outcomes of COVID-19 patients without dyspnea.

Methods

A single-center retrospective cohort study, based on data extracted from the electronic hospital information system, with COVID-19 patients over a 10-month period in Riyadh, Saudi Arabia.

Results

Of the COVID-19 patients presenting at the Emergency Department with a SpO₂ < 90%, 13% had silent hypoxia. The majority of the patients required BiPAP, 34% were intubated and 60% were admitted to an intensive care unit. There was no association between dyspnea and gender, age group, body mass index, or comorbidity. Cough, fever, and chronic cardiac diseases were predictive for dyspnea in a regression analysis. There was no difference in the clinical outcome between patients with silent dyspnea or dyspnea. Age and obesity were significantly associated with a decrease in survival, and an increase in the initial SpO₂ increased survival.

Conclusion

Patients with cardiac disease are more likely to present with silent hypoxia. The SpO₂ saturation in COVID-19 may be an independent predictor of survival. Silent hypoxia in COVID-19 patients does not appear to have an association with increase in mortality.

Different Outcomes of "Silent Hypoxia" in Patients with COVID-19 Pneumonia: A Case Series and Literature Review

COVID-19 has been declared a pandemic since March 2020 and it has been responsible for millions of deaths worldwide. The SARS-CoV-2 causes a spectrum of diseases mainly affecting the respiratory system. It can also complicate other systems causing thromboembolic phenomena and myocardial ischaemia. An entity of hypoxia has been described in these patients which show no clinical signs and symptoms of respiratory distress despite being extremely hypoxic. This is called silent or happy hypoxia. The exact mechanism for this is not known. We report 4 cases which had similar presentations of silent hypoxia but had different course of illness and different outcomes. All 4 patients did not show any signs of respiratory distress, but had oxygen saturation less than 82%. 3 of them needed intensive care unit support for oxygen therapy and subsequently needed noninvasive ventilation. Only one required invasive ventilation. The fourth patient did not require intensive care support. The patient who required invasive ventilation succumbed due to severe COVID pneumonia whereas the other 3 patients were discharged from the hospital. Silent hypoxemia can go undetected in COVID-19 patients particularly in the time of a pandemic. This case series highlights the importance of meticulous clinical examination including oxygen saturation measurements in suspected or confirmed patients with COVID-19. The course of illness can be different in different populations, and this needs further clinical evidence.

Non-invasive ventilation versus mechanical ventilation in hypoxemic patients with COVID-19

Purpose

Limited mechanical ventilators (MV) during the Coronavirus disease (COVID-19) pandemic have led to the use of non-invasive ventilation (NIV) in hypoxemic patients, which has not been studied well. We aimed to assess the association of NIV versus MV with mortality and morbidity during respiratory intervention among hypoxemic patients admitted with COVID-19.

Methods

We performed a retrospective multi-center cohort study across 5 hospitals during March–April 2020. Outcomes included mortality, severe COVID-19-related symptoms, time to discharge, and final oxygen saturation (SpO2) at the conclusion of the respiratory intervention. Multivariable regression of outcomes was conducted in all hypoxemic participants, 4 subgroups, and propensity-matched analysis.

Results

Of 2381 participants with laboratory-confirmed SARS-CoV-2, 688 were included in the study who were hypoxemic upon initiation of respiratory intervention. During the study period, 299 participants died (43%), 163 were admitted to the ICU (24%), and 121 experienced severe COVID-19-related symptoms (18%). Participants on MV had increased mortality than those on NIV (128/154 [83%] versus 171/534 [32%], OR = 30, 95% CI 16–60) with a mean survival of 6 versus 15 days, respectively. The MV group experienced more severe COVID-19-related symptoms [55/154 (36%) versus 66/534 (12%), OR = 4.3, 95% CI 2.7–6.8], longer time to discharge (mean 17 versus 7.1 days), and lower final SpO2 (92 versus 94%). Across all subgroups and propensity-matched analysis, MV was associated with a greater OR of death than NIV.

Conclusions

NIV was associated with lower respiratory intervention mortality and morbidity than MV. However, findings may be liable to unmeasured confounding and further study from randomized controlled trials is needed to definitively determine the role of NIV in hypoxemic patients with COVID-19.

Supplementary Information

The online version contains supplementary material available at 10.1007/s15010-021-01633-6.