• Todd W Rice, Arthur P Wheeler, Gordon R Bernard, Douglas L Hayden, David A Schoenfeld, Lorraine B Ware, and National Institutes of Health, National Heart, Lung, and Blood Institute ARDS Network.
• MSc, Division of Allergy, Pulmonary, and Critical Care Medicine, T-1218 MCN, Nashville, TN 37232-2650, USA. todd.rice@vanderbilt.edu
• Chest. 2007 Aug 1;132(2):410-7.

BackgroundThe diagnostic criteria for acute lung injury (ALI) and ARDS utilize the Pao(2)/fraction of inspired oxygen (Fio(2)) [P/F] ratio measured by arterial blood gas analysis to assess the degree of hypoxemia. We hypothesized that the pulse oximetric saturation (Spo(2))/Fio(2) (S/F) ratio can be substituted for the P/F ratio in assessing the oxygenation criterion of ALI.MethodsCorresponding measurements of Spo(2) (values ResultsIn the derivation data set (2,613 measurements), the relationship between S/F and P/F was described by the following equation: S/F = 64 + 0.84 x (P/F) [p < 0.0001; r = 0.89). An S/F ratio of 235 corresponded with a P/F ratio of 200, while an S/F ratio of 315 corresponded with a P/F ratio of 300. The validation database (2,031 measurements) produced a similar linear relationship. The S/F ratio threshold values of 235 and 315 resulted in 85% sensitivity with 85% specificity and 91% sensitivity with 56% specificity, respectively, for P/F ratios of 200 and 300.ConclusionS/F ratios correlate with P/F ratios. S/F ratios of 235 and 315 correlate with P/F ratios of 200 and 300, respectively, for diagnosing and following up patients with ALI and ARDS.

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