Hospitalised COVID-19 outcomes are predicted by hypoxaemia and pneumonia phenotype irrespective of the timing of their emergence

Abstract

Despite the known clinical importance of hypoxemia and pneumonia, there is a paucity of evidence for these variables with respect to risk of mortality and short-term outcomes among those hospitalised with COVID-19.

Objective: Describe the prevalence and clinical course of patients hospitalised with COVID-19 based on oxygenation and pneumonia status at presentation and determine the incidence of emergent hypoxaemia or radiographic pneumonia during admission.

Methods: A retrospective study was conducted using a Canadian regional registry. Patients were stratified according to hypoxaemia/pneumonia phenotype and prevalence. Clinical parameters were compared between phenotypes using χ² and one-way Analysis of variance (ANOVA). Cox analysis estimated adjusted Hazard Ratios (HR) for associations between disease outcomes and phenotypes.

Results: At emergency department (ED) admission, the prevalence of pneumonia and hypoxaemia was 43% and 50%, respectively, and when stratified to phenotypes: 28.2% hypoxaemia⁺/pneumonia⁺, 22.2% hypoxaemia⁺/pneumonia^-, 14.5% hypoxaemia^-/pneumonia⁺ and 35.1% hypoxaemia^-/pneumonia^-. Mortality was 31.1% in the hypoxaemia⁺/pneumonia^- group and 26.3% in the hypoxaemia⁺/pneumonia⁺ group. Hypoxaemia with pneumonia and without pneumonia predicted higher probability of death. Hypoxaemia either <24 hours or ≥24 hours after hospitalisation predicted higher mortality and need for home oxygen compared with those without hypoxaemia. Patients with early hypoxaemia had higher probability of Intensive care unit (ICU) admission compared with those with late hypoxaemia.

Conclusion: Mortality in COVID-19 infection is predicted by hypoxaemia with or without pneumonia and was greatest in patients who initially presented with hypoxaemia. The emergence of hypoxaemia was predicted by radiographic pneumonia. Patients with early and emergent hypoxaemia had similar mortality but were less likely to be admitted to ICU. There may be delayed identification of hypoxaemia, which prevents timely escalation of care.

Keywords: COVID-19; adult intensive & critical care; adult thoracic medicine; public health; respiratory infections; thoracic medicine.

Figure 1

Kaplan-Meier survival analysis based on pneumonia and hypoxaemia. (A) Patients in the hypoxaemia⁺/pneumonia⁺ group were more likely to require ICU admission, whereas the hypoxaemia⁻/pneumonia⁻ group was least likely. In terms of mortality (B), patients in the hypoxaemia⁺/pneumonia⁻ group were least likely to survive compared with the hypoxaemia⁻/pneumonia⁻ group. At discharge, the group most likely to require home oxygen therapy (C) was the hypoxaemia⁺/pneumonia⁺ group compared with the hypoxaemia⁻/pneumonia⁻ group. (D) Patients with hypoxaemia in under 24 hours of hospital presentation were more likely to require Intensive Care Unit (ICU) admission sooner, whereas those who developed hypoxaemia after 24 hours of presentation were less likely to require ICU admission (p<0.001). (E) Regardless of the development of hypoxaemia in <24 or >24 hours, patients had a lower probability of survival compared with those without hypoxaemia during their hospital stay (p<0.001). (F) Similarly, patients who were hypoxaemic at any point during their hospital admission were more likely to require home oxygen compared with patients without hypoxaemia (p<0.001).

Figure 2

OR of adverse outcomes in COVID-19 patients logistic regression was used to develop forest plots showing the OR and 95% CI for various adverse outcomes including death (A), use of high-flow nasal cannula (HFNC) (B), Intensive Care Unit (ICU) admission (C), use of invasive mechanical ventilation (IMV) (D), and requirement of home oxygen at discharge (E). The OR for these outcomes was adjusted for number of comorbidities (CM), age, sex, hypoxaemia (H) and/or pneumonia (P).