AUTHOR=Damiani Elisa , Casarotta Erika , Carsetti Andrea , Mariotti Giulia , Vannicola Sara , Giorgetti Rachele , Domizi Roberta , Scorcella Claudia , Adrario Erica , Donati Abele 

TITLE=Too much tolerance for hyperoxemia in mechanically ventilated patients with SARS-CoV-2 pneumonia? Report from an Italian intensive care unit

JOURNAL=Frontiers in Medicine

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2022.957773

DOI=10.3389/fmed.2022.957773

ISSN=2296-858X

ABSTRACT=Background 
In COVID-19 patients requiring mechanical ventilation, high oxygen (O2) doses for prolonged time periods may be necessary. Although life-saving in most cases, too much O2 may exert deleterious effects. We aimed to describe the prevalence of hyperoxemia and excessive O2 administration in mechanically ventilated patients with SARS-CoV-2 pneumonia and determine whether hyperoxemia is associated with mortality in the Intensive Care Unit (ICU) or ventilator-associated pneumonia (VAP).
Methods 
Retrospective single-center study on adult patients with SARS-CoV-2 pneumonia requiring invasive mechanical ventilation for ≥48 hours. Patients undergoing extracorporeal respiratory support were excluded. We calculated the excess O2 administered based on the ideal arterial O2 tension (PaO2) target of 55-80 mmHg. We defined hyperoxemia as PaO2 >100 mmHg and hyperoxia+hyperoxemia as an inspired O2 fraction (FiO2) >60% + PaO2 >100 mmHg. Risk factors for ICU-mortality and VAP were assessed through multivariate analyses.
Results
One hundred thirty-four patients were included. For each day of mechanical ventilation, each patient received a median excess O2 of 1121 [829-1449] L. Hyperoxemia was found in 38 [27-55] % of arterial blood gases, hyperoxia + hyperoxemia in 11 [5-18] % of cases. The FiO2 was not reduced in 69 [62-76] % of cases of hyperoxemia. Adjustments were made more frequently with higher PaO2 or initial FiO2 levels. ICU-mortality was 32%. VAP was diagnosed in 48.5% of patients. Hyperoxemia (OR 1.300 95% CI [1.097-1.542]), time of exposure to hyperoxemia (OR 2.758 [1.406-5.411]), hyperoxia+hyperoxemia (OR 1.144 [1.008-1.298]) and daily excess O2 (OR 1.003 [1.001-1.005]) were associated with higher risk for ICU-mortality, independently of age, Sequential Organ failure Assessment score at ICU-admission and mean PaO2/FiO2. Hyperoxemia (OR 1.033 [1.006-1.061]), time of exposure to hyperoxemia (OR 1.108 [1.018-1.206]), hyperoxia+hyperoxemia (OR 1.038 [1.003-1.075]) and daily excess O2 (OR 1.001 [1.000-1.001]) were identified as risk factors for VAP, independently of body mass index, blood transfusions, days of neuromuscular blocking agents (before VAP), prolonged prone positioning and mean PaO2/FiO2 before VAP.
Conclusions
Excess O2 administration and hyperoxemia were common in mechanically ventilated patients with SARS-CoV-2 pneumonia. The exposure to hyperoxemia may be associated with ICU-mortality and greater risk for VAP.