RT Journal Article SR Electronic T1 Predictive validity of effective shunt fraction in critically ill patients JF bioRxiv FD Cold Spring Harbor Laboratory SP 491167 DO 10.1101/491167 A1 Emma M Chang A1 Andrew Bretherick A1 Gordon B Drummond A1 J Kenneth Baillie YR 2018 UL http://biorxiv.org/content/early/2018/12/10/491167.abstract AB Accurate measurement of pulmonary oxygenation is important for classification of disease severity and quantification of outcomes in clinical studies. We compared predictive validity of established tension-based methods with two new measures of shunt fraction: (1) a non-invasive effective shunt (ES); and (2) inferred values from an integrated mathematical model of gas exchange (DB). Median absolute error (MAE) values for the four measures considered were: alveolar-arterial difference, 7.30kPa; PaO2/FIO2 ratio, 2.41kPa; DB, 2.13kPa; ES: 1.88kPa. ES performed significantly better than other measures (p<10−10 in all comparisons). While the simplicity of P/F is suitable for routine use, the superior predictive validity of ES should make this measure the preferred choice where physiological accuracy is important, such as for use as surrogate outcome in clinical research.