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Review
. 2023 Nov 1;11(4):70.
doi: 10.3390/medsci11040070.

Alveolar Hyperoxia and Exacerbation of Lung Injury in Critically Ill SARS-CoV-2 Pneumonia

Ahilanandan Dushianthan  1   2 , Luke Bracegirdle  1   2 , Rebecca Cusack  1   2 , Andrew F Cumpstey  1   2 , Anthony D Postle  1   2 , Michael P W Grocott  1   2
Affiliations
Review

Alveolar Hyperoxia and Exacerbation of Lung Injury in Critically Ill SARS-CoV-2 Pneumonia

Ahilanandan Dushianthan et al. Med Sci (Basel). .

Abstract

Acute hypoxic respiratory failure (AHRF) is a prominent feature of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) critical illness. The severity of gas exchange impairment correlates with worse prognosis, and AHRF requiring mechanical ventilation is associated with substantial mortality. Persistent impaired gas exchange leading to hypoxemia often warrants the prolonged administration of a high fraction of inspired oxygen (FiO2). In SARS-CoV-2 AHRF, systemic vasculopathy with lung microthrombosis and microangiopathy further exacerbates poor gas exchange due to alveolar inflammation and oedema. Capillary congestion with microthrombosis is a common autopsy finding in the lungs of patients who die with coronavirus disease 2019 (COVID-19)-associated acute respiratory distress syndrome. The need for a high FiO2 to normalise arterial hypoxemia and tissue hypoxia can result in alveolar hyperoxia. This in turn can lead to local alveolar oxidative stress with associated inflammation, alveolar epithelial cell apoptosis, surfactant dysfunction, pulmonary vascular abnormalities, resorption atelectasis, and impairment of innate immunity predisposing to secondary bacterial infections. While oxygen is a life-saving treatment, alveolar hyperoxia may exacerbate pre-existing lung injury. In this review, we provide a summary of oxygen toxicity mechanisms, evaluating the consequences of alveolar hyperoxia in COVID-19 and propose established and potential exploratory treatment pathways to minimise alveolar hyperoxia.

Keywords: COVID-19; hyperoxia; intensive care; lung injury; oxygen therapy.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The SARS-CoV-2 infection exacerbated by alveolar hyperoxia leading to worsening systemic hypoxemia.
Figure 2
Figure 2
Increased oxidative stress as a result of a combination of SARS-CoV-2 viral infection and alveolar hyperoxia. * Reactive oxygen species.
Figure 3
Figure 3
The renin–angiotensin/Mas system and the potential consequences of downregulation of ACE2 receptors.
See this image and copyright information in PMC

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