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

BACKGROUND: In COVID-19 patients requiring mechanical ventilation, the administration of high oxygen (O(2)) doses for prolonged time periods may be necessary. Although life-saving in most cases, O(2) may exert deleterious effects if administered in excessive concentrations. We aimed to describe the prevalence of hyperoxemia and excessive O(2) 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 the onset of ventilator-associated pneumonia (VAP). MATERIALS AND METHODS: Retrospective single-center study on adult patients with SARS-CoV-2 pneumonia requiring invasive mechanical ventilation for ≥48 h. Patients undergoing extracorporeal respiratory support were excluded. We calculated the excess O(2) administered based on the ideal arterial O(2) tension (PaO(2)) target of 55–80 mmHg. We defined hyperoxemia as PaO(2) > 100 mmHg and hyperoxia + hyperoxemia as an inspired O(2) fraction (FiO(2)) > 60% + PaO(2) > 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 O(2) of 1,121 [829–1,449] L. Hyperoxemia was found in 38 [27–55]% of arterial blood gases, hyperoxia + hyperoxemia in 11 [5–18]% of cases. The FiO(2) was not reduced in 69 [62–76]% of cases of hyperoxemia. Adjustments were made more frequently with higher PaO(2) or initial FiO(2) 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 O(2) (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 PaO(2)/FiO(2). 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 O(2) (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 PaO(2)/FiO(2) before VAP. CONCLUSION: Excess O(2) 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.