Assessment of ARDS Severity: PaO2 /FiO2 versus PaO2 /Lactate - Abstract
Background: Among other limitations of the ratio of partial pressure of oxygen in arterial blood (PaO2) to the fraction of inspiratory oxygen concentration (FiO2) is the fact that it is influenced by Positive End-Expiratory Pressure (PEEP). Among those with ratio of the same value, the risk of lung damage is much higher in the patients with a higher PEEP. This leaves the way open for adaptations of this score. The aim of this study is to measure the correlation between a new proposed index, the PaO2/lactate index and the current golden standard, the PaO2/FiO2 index. Methods: Blood gas samples from 100 patients with Acute Respiratory Distress Syndrome (ARDS) (PaO2/FiO2 < 300), who were intubated and ventilated, in the surgical intensive care unit of Emile Muller Hospital in Mulhouse, France, from January 2021 to July 2022 were analysed. Data on gasometry, mainly FiO2, PaO2 and lactate, were collected. The Spearman’s rank-order (Rho) test was used to determine the correlation between the PaO2/FiO2 and PaO2 /lactate index and the area under the area under the ROC curve was used to compare the prediction of mortality. Results: The median age of the patients was 65.5 [21-90] years, and 70% of them were male (M/F 2.33). Spearman’s Rho was 0.764 (p = 0.01). The area under the ROC curve was 0.687 (95% CI: 0.612 – 0.761) and p < 0.001 for the PaO2/FiO2 index and 0.716 (95% CI: 0.646 – 0.787) and p < 0.001 for the PaO2 /lactate index. Conclusion: The PaO2/lactate index not only correlates well with the PaO2 /FiO2 index, it a much more accurate predictor of mortality. For this reason, it could be used instead of the PaO2 /FiO2 index to assess the severity of ARDS