The Sequential Organ Failure Assessment (SOFA) score is validated as a measure of severity of illness over time in intensive care unit (ICU) patients and can be used to follow the course of organ dysfunction and response to treatment1. SOFA has become a frequently used scoring system of patients in multi-organ failure, given its high sensitivity and specificity as a predictor of morbidity and mortality in critically ill patients2. The severity of respiratory dysfunction is measured in the SOFA score by PaO2/FiO2 (PF) ratio, which is also used as a measure of severity of hypoxemia in patients with acute respiratory distress syndrome (ARDS).