Evaluation of the oxygenation index in adult respiratory failure

BACKGROUND: The oxygenation index (mean airway pressure × FIO2 divided by PaO2) was originally devised to measure severity of illness and predict outcome in neonatal respiratory failure. We evaluated the discrimination of a modified oxygenation index (modified with age) for predicting 28-day mortality in adults with respiratory failure (adult respiratory distress syndrome [ARDS]) using the ALVEOLI section of the ARDSNet database and validated the results in the full ARDSNet database. METHODS: We compared age-adjusted oxygenation index (AOI) on ventilator Days 1 to 4 with 28-day mortality. RESULTS: AOI correlated positively with mortality (area under the receiver operating characteristic curve, 0.70-0.74, for ARDS Days 1-4). Following initial development, AOI related to mortality was validated in two other ARDSNet databases producing similar results (area under the receiver operating characteristic curve, 0.70-0.78). CONCLUSION: The observed sensitivity and specificity analysis demonstrated that AOI is equivalent to or better than other mortality prediction systems used for ARDS. LEVEL OF EVIDENCE: Prognostic, level III.