Critical care medicine
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Critical care medicine · Apr 2022
The Influence of Hypercapnia and Atmospheric Pressure on the PaO2/FIO2 Ratio-Pathophysiologic Considerations, a Case Series, and Introduction of a Clinical Tool.
The ratio between Pao2 and Fio2 is used as a marker for impaired oxygenation and acute respiratory distress syndrome classification. However, any discrepancy between Fio2 and o2 fraction in the alveolus affects the Pao2/Fio2 ratio. Correcting the Pao2/Fio2 ratios using the alveolar gas equation may result in an improved reflection of the pulmonary situation. This study investigates the difference between standard and corrected Pao2/Fio2 in magnitude, its correlation with the mortality of acute respiratory distress syndrome classification, and trends over time. ⋯ Correcting the Pao2/Fio2 ratio for the alveolar gas equation predominantly affects patients with high ratios between Pao2 and Fio2 and Paco2 and at low atmospheric pressure. Using the corrected Pao2/Fio2 ratio for acute respiratory distress syndrome classification results in improved correlation with the 7-day ICU mortality and increases generalization among acute respiratory distress syndrome studies. The authors provide a free, web-based tool.