Silent hypoxia is not an identifiable characteristic in patients with COVID-19 infection

Nicholas Russell Plummer; Andrew Fogarty; Dominick Shaw; Timothy Card; Joe West; Colin Crooks

doi:10.1016/j.rmed.2022.106858

Silent hypoxia is not an identifiable characteristic in patients with COVID-19 infection

Respir Med. 2022 Jun:197:106858. doi: 10.1016/j.rmed.2022.106858. Epub 2022 Apr 26.

Authors

Nicholas Russell Plummer¹, Andrew Fogarty², Dominick Shaw², Timothy Card³, Joe West⁴, Colin Crooks⁵

Affiliations

¹ Adult Critical Care, Nottingham University Hospitals NHS Trust, NG7 2UH, UK. Electronic address: nickplummer@nhs.net.
² NIHR Respiratory Biomedical Research Centre, University of Nottingham, NG7 2UH, UK.
³ Nottingham Digestive Diseases Centre, School of Medicine, University of Nottingham, NG7 2UH, UK; Population and Lifespan Sciences, School of Medicine, University of Nottingham, NG7 2UH, UK; NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, NG7 2UH, UK.
⁴ Population and Lifespan Sciences, School of Medicine, University of Nottingham, NG7 2UH, UK; NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, NG7 2UH, UK.
⁵ Nottingham Digestive Diseases Centre, School of Medicine, University of Nottingham, NG7 2UH, UK; NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, NG7 2UH, UK.

Abstract

Background: We aimed to assess whether asymptomatic ("happy") hypoxia was an identifiable physiological phenotype of COVID-19 acute respiratory distress syndrome (ARDS), and associated with need for ICU admission.

Methods: We performed an observational cohort study of all adult patients admitted with hypoxaemic respiratory failure to a large acute hospital Trust serving the East Midlands, UK. Patients with confirmed COVID-19 were compared to those without. Physiological response to hypoxaemia was modelled using a linear mixed effects model.

Results: Of 1,586 patients included, 75% tested positive for SARS-CoV-2. The ROX index was 2.08 min^-1 lower (1.56-2.61, p < 0.001) in the COVID-19 cohort when adjusted for age and ethnicity, suggesting an enhanced respiratory response to hypoxia compared to the non-Covid-19 patients. There was substantial residual inter- and intra-patient variability in the respiratory response to hypoxaemia. 33% of the infected cohort required ICU, and of these 31% died within 60 days. ICU admission and mortality were both associated with an enhanced respiratory response for all degrees of hypoxaemia.

Conclusions: Patients with COVID-19 display a more symptomatic phenotype in response to hypoxaemia than those with other causes of hypoxaemic respiratory failure, however individual patients exhibit a wide range of responses. As such although asymptomatic hypoxaemia may be a phenomenon in any individual patient with hypoxaemic respiratory failure, it is no more frequently observed in those with SARS-CoV-2 infection than without.

Keywords: ARDS; COVID-19; Clinical deterioration; Hypoxaemia.

Publication types

Observational Study
Research Support, Non-U.S. Gov't

MeSH terms

COVID-19* / complications
Humans
Hypoxia / etiology
Respiratory Distress Syndrome* / etiology
Respiratory Insufficiency* / complications
SARS-CoV-2