Correction to: COVID-19: Pulse oximeters in the spotlight

Respiratory Drive, Dyspnea, and Silent Hypoxemia: A Physiological Review in the Context of COVID-19

Infection with SARS-CoV-2 in select individuals results in viral sepsis, pneumonia, and hypoxemic respiratory failure, collectively known as COVID-19. In the early months of the pandemic, the combination of novel disease presentation, enormous surges of critically ill patients, and severity of illness lent to early observations and pronouncements regarding COVID-19 that could not be scientifically validated owing to crisis circumstances. One of these was a phenomenon referred to as "happy hypoxia." Widely discussed in the lay press, it was thought to represent a novel and perplexing phenomenon: severe hypoxemia coupled with the absence of respiratory distress and dyspnea. Silent hypoxemia is the preferred term describing an apparent lack of distress in the presence of hypoxemia. However, the phenomenon is well known among respiratory physiologists as hypoxic ventilatory decline. Silent hypoxemia can be explained by physiologic mechanisms governing the control of breathing, breathing perception, and cardiovascular compensation. This narrative review examines silent hypoxemia during COVID-19 as well as hypotheses that viral infection of the central and peripheral nervous system may be implicated. Moreover, the credulous embrace of happy hypoxia and the novel hypotheses proposed to explain it has exposed significant misunderstandings among clinicians regarding the physiologic mechanisms governing both the control of breathing and the modulation of breathing sensations. Therefore, a substantial focus of this paper is to provide an in-depth review of these topics.

Venous blood gas analysis in patients with COVID-19 symptoms in the early assessment of virus positivity

Objectives

Coronavirus disease 2019 (COVID-19) is currently a worldwide major health threat. Recognizing hypoxia in patients early on can have a considerable effect on therapy success and survival rate.

Methods

We collected data using a standard blood gas analyzer from 50 patients and analyzed measurements of partial pressure of carbon dioxide-pCO2, partial pressure of oxygen-pO2 and oxygen saturation-sO2, bicarbonate concentrations-HCO3− as well as ionized calcium concentrations. We further examined PCR test results for SARS-CoV-2 of the patients and analyzed differences between patients tested positive and those tested negative for the virus.

Results

Venous pCO2 was significantly higher whereas pO2 and sO2 were significantly lower in patients who tested positive for SARS-CoV-2. The pH, and ionized calcium concentrations of patients tested positive for the virus were significantly lower than in those tested negative.

Conclusions

Symptomatic SARS-CoV-2-positive patients upon admission to the emergency room exhibit lower venous blood levels of oxygen, pH, and calcium and higher levels of carbon dioxide compared to symptomatic SARS-CoV-2-negative patients. This blood gas analysis constellation could help in identifying SARS-CoV-2-positive patients more rapidly and identifying early signs of hypoxia.