Utility of peripheral blood oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) ratio and arterial partial oxygen pressure (PaO2)/FiO2 ratio in the diagnosis of acute respiratory distress syndrome: A comparative study.

Our study determined the reliability of using the ratio of peripheral blood oxygen saturation (SpO₂) and the fraction of inspired oxygen (FiO₂) rather than the ratio of arterial partial oxygen pressure (PaO₂) and FiO₂ for diagnosing acute respiratory distress syndrome (ARDS). Pulse oximetry and arterial blood gas analysis were performed to obtain both ratios, respectively, in 70 patients who fulfilled the Berlin definition criteria of ARDS. A detailed history, clinical examination, and relevant evaluation were done. There was a significant correlation between the two ratios. The former had a lower sensitivity and specificity than the latter. Thus, the SpO₂/FiO₂ ratio is a reliable, straightforward, non-invasive, and readily available marker for diagnosing the presence and severity of ARDS, and may be used as an alternative to the PaO₂/FiO₂ ratio in resource-limited settings.