Silent hypoxaemia in COVID-19 patients

Abstract

The clinical presentation of COVID-19 due to infection with SARS-CoV-2 is highly variable with the majority of patients having mild symptoms while others develop severe respiratory failure. The reason for this variability is unclear but is in critical need of investigation. Some COVID-19 patients have been labelled with 'happy hypoxia', in which patient complaints of dyspnoea and observable signs of respiratory distress are reported to be absent. Based on ongoing debate, we highlight key respiratory and neurological components that could underlie variation in the presentation of silent hypoxaemia and define priorities for subsequent investigation.

Keywords: COVID-19; SARS-CoV-2; dyspnoea; happy hypoxia; silent hypoxaemia.

Figure 1.. Individual variation in air hunger responses to hypoxia

Variable air hunger responses to different levels of steady-state hypoxia, with ${\stackrel{.}{V}}_{\mathrm{E}}$ set at resting levels by mechanical ventilation, in three individuals (A, B and C represent subjects 3, 1 and 5, respectively, from Moosavi et al. (2003)). Studies were conducted at eucapnia. The three selected individuals show the range of normal sensitivities in the sample of 10. A response similar to individual C could represent a patient with S_pO2 = 76% and no dyspnoea.