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Dynamic blood oxygen indices in mechanically ventilated COVID-19 patients with acute hypoxic respiratory failure: a cohort study

Dynamic blood oxygen indices in mechanically ventilated COVID-19 patients with acute hypoxic respiratory failure: a cohort study
Dynamic blood oxygen indices in mechanically ventilated COVID-19 patients with acute hypoxic respiratory failure: a cohort study

Background: acute hypoxic respiratory failure (AHRF) is a hallmark of severe COVID-19 pneumonia and often requires supplementary oxygen therapy. Critically ill COVID-19 patients may require invasive mechanical ventilation, which carries significant morbidity and mortality. Understanding of the relationship between dynamic changes in blood oxygen indices and clinical variables is lacking. We evaluated the changes in blood oxygen indices-PaO2, PaO2/FiO2 ratio, oxygen content (CaO2) and oxygen extraction ratio (O2ER) in COVID-19 patients through the first 30-days of intensive care unit admission and explored relationships with clinical outcomes.

Methods and findings: we performed a retrospective observational cohort study of all adult COVID-19 patients in a single institution requiring invasive mechanical ventilation between March 2020 and March 2021. We collected baseline characteristics, clinical outcomes and blood oxygen indices. 36,383 blood gas data points were analysed from 184 patients over 30-days. Median participant age was 59.5 (IQR 51.0, 67.0), BMI 30.0 (IQR 25.2, 35.5) and the majority were men (62.5%) of white ethnicity (70.1%). Median duration of mechanical ventilation was 15-days (IQR 8, 25). Hospital survival at 30-days was 72.3%. Non-survivors exhibited significantly lower PaO2 throughout intensive care unit admission: day one to day 30 averaged mean difference -0.52 kPa (95% CI: -0.59 to -0.46, p<0.01). Non-survivors exhibited a significantly lower PaO2/FiO2 ratio with an increased separation over time: day one to day 30 averaged mean difference -5.64 (95% CI: -5.85 to -5.43, p<0.01). While all patients had sub-physiological CaO2, non-survivors exhibited significantly higher values. Non-survivors also exhibited significantly lower oxygen extraction ratio with an averaged mean difference of -0.08 (95% CI: -0.09 to -0.07, p<0.01) across day one to day 30.

Conclusions: as a novel cause of acute hypoxic respiratory failure, COVID-19 offers a unique opportunity to study a homogenous cohort of patients with hypoxaemia. In mechanically ventilated adult COVID-19 patients, blood oxygen indices are abnormal with substantial divergence in PaO2/FiO2 ratio and oxygen extraction ratio between survivors and non-survivors. Despite having higher CaO2 values, non-survivors appear to extract less oxygen implying impaired oxygen utilisation. Further exploratory studies are warranted to evaluate and improve oxygen extraction which may help to improve outcomes in severe hypoxaemic mechanically ventilated COVID-19 patients.

adult, COVID-19/therapy, cohort studies, female, humans, hypoxia, male, oxygen, respiration, artificial, respiratory distress syndrome, respiratory insufficiency/therapy, retrospective studies, SARS-CoV-2
1932-6203
e0269471
Bracegirdle, Luke
a23d4bd0-eab9-4d0b-a2bc-fc02b5130511
Jackson, Alexander
cff0f006-7903-4f95-929c-f4962156ef20
Beecham, Ryan
f930648f-5bcb-4c56-ae34-61db6d54b251
Burova, Maria
ce82b538-760f-446a-8c01-803c818ddb84
Hunter, Elsie
15769f4c-9a09-4e1c-8ae3-e50ad631b74e
Hamilton, Laura G
3bd9f419-f3b5-4aa6-8c63-6a4be80c2ed1
Pandya, Darshni
547f248e-077b-44bc-8a7b-65a11d7da712
Morden, Clare
9fd388c3-a4cb-43f9-a5de-a636c30dcf7b
Grocott, Michael P.W.
1e87b741-513e-4a22-be13-0f7bb344e8c2
Cumpstey, Andrew
cd040417-5e62-41d2-8640-1ec8905858a7
Dushianthan, Ahilanandan
013692a2-cf26-4278-80bd-9d8fcdb17751
REACT COVID-19 investigators
Bracegirdle, Luke
a23d4bd0-eab9-4d0b-a2bc-fc02b5130511
Jackson, Alexander
cff0f006-7903-4f95-929c-f4962156ef20
Beecham, Ryan
f930648f-5bcb-4c56-ae34-61db6d54b251
Burova, Maria
ce82b538-760f-446a-8c01-803c818ddb84
Hunter, Elsie
15769f4c-9a09-4e1c-8ae3-e50ad631b74e
Hamilton, Laura G
3bd9f419-f3b5-4aa6-8c63-6a4be80c2ed1
Pandya, Darshni
547f248e-077b-44bc-8a7b-65a11d7da712
Morden, Clare
9fd388c3-a4cb-43f9-a5de-a636c30dcf7b
Grocott, Michael P.W.
1e87b741-513e-4a22-be13-0f7bb344e8c2
Cumpstey, Andrew
cd040417-5e62-41d2-8640-1ec8905858a7
Dushianthan, Ahilanandan
013692a2-cf26-4278-80bd-9d8fcdb17751

REACT COVID-19 investigators (2022) Dynamic blood oxygen indices in mechanically ventilated COVID-19 patients with acute hypoxic respiratory failure: a cohort study. PLoS ONE, 17 (6), e0269471. (doi:10.1371/journal.pone.0269471).

Record type: Article

Abstract

Background: acute hypoxic respiratory failure (AHRF) is a hallmark of severe COVID-19 pneumonia and often requires supplementary oxygen therapy. Critically ill COVID-19 patients may require invasive mechanical ventilation, which carries significant morbidity and mortality. Understanding of the relationship between dynamic changes in blood oxygen indices and clinical variables is lacking. We evaluated the changes in blood oxygen indices-PaO2, PaO2/FiO2 ratio, oxygen content (CaO2) and oxygen extraction ratio (O2ER) in COVID-19 patients through the first 30-days of intensive care unit admission and explored relationships with clinical outcomes.

Methods and findings: we performed a retrospective observational cohort study of all adult COVID-19 patients in a single institution requiring invasive mechanical ventilation between March 2020 and March 2021. We collected baseline characteristics, clinical outcomes and blood oxygen indices. 36,383 blood gas data points were analysed from 184 patients over 30-days. Median participant age was 59.5 (IQR 51.0, 67.0), BMI 30.0 (IQR 25.2, 35.5) and the majority were men (62.5%) of white ethnicity (70.1%). Median duration of mechanical ventilation was 15-days (IQR 8, 25). Hospital survival at 30-days was 72.3%. Non-survivors exhibited significantly lower PaO2 throughout intensive care unit admission: day one to day 30 averaged mean difference -0.52 kPa (95% CI: -0.59 to -0.46, p<0.01). Non-survivors exhibited a significantly lower PaO2/FiO2 ratio with an increased separation over time: day one to day 30 averaged mean difference -5.64 (95% CI: -5.85 to -5.43, p<0.01). While all patients had sub-physiological CaO2, non-survivors exhibited significantly higher values. Non-survivors also exhibited significantly lower oxygen extraction ratio with an averaged mean difference of -0.08 (95% CI: -0.09 to -0.07, p<0.01) across day one to day 30.

Conclusions: as a novel cause of acute hypoxic respiratory failure, COVID-19 offers a unique opportunity to study a homogenous cohort of patients with hypoxaemia. In mechanically ventilated adult COVID-19 patients, blood oxygen indices are abnormal with substantial divergence in PaO2/FiO2 ratio and oxygen extraction ratio between survivors and non-survivors. Despite having higher CaO2 values, non-survivors appear to extract less oxygen implying impaired oxygen utilisation. Further exploratory studies are warranted to evaluate and improve oxygen extraction which may help to improve outcomes in severe hypoxaemic mechanically ventilated COVID-19 patients.

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Accepted/In Press date: 22 May 2022
e-pub ahead of print date: 10 June 2022
Keywords: adult, COVID-19/therapy, cohort studies, female, humans, hypoxia, male, oxygen, respiration, artificial, respiratory distress syndrome, respiratory insufficiency/therapy, retrospective studies, SARS-CoV-2

Identifiers

Local EPrints ID: 478384
URI: http://eprints.soton.ac.uk/id/eprint/478384
ISSN: 1932-6203
PURE UUID: 3bbbc3c4-7fe5-4ca5-8733-a81ff8de77c5
ORCID for Michael P.W. Grocott: ORCID iD orcid.org/0000-0002-9484-7581
ORCID for Andrew Cumpstey: ORCID iD orcid.org/0000-0001-6257-207X
ORCID for Ahilanandan Dushianthan: ORCID iD orcid.org/0000-0002-0165-3359

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Date deposited: 29 Jun 2023 16:52
Last modified: 10 Dec 2024 18:36

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Contributors

Author: Luke Bracegirdle
Author: Alexander Jackson
Author: Ryan Beecham
Author: Maria Burova
Author: Elsie Hunter
Author: Laura G Hamilton
Author: Darshni Pandya
Author: Clare Morden
Author: Andrew Cumpstey ORCID iD
Author: Ahilanandan Dushianthan ORCID iD
Corporate Author: REACT COVID-19 investigators

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