Prognostic value of the oxygenation index measured during mechanical ventilation and weaning. A retrospective cohort study.

The aim of this study was to investigate the predictive value of the ratio of oxygen saturation (ROX) index calculated during mechanical ventilation (MV) and the weaning period in evaluating readiness to weaning and the success of the spontaneous breathing trial (SBT), extubation, and mortality. We also compared the results of the ROX index calculated with partial arterial oxygen pressure (PaO2), arterial oxygen saturation (SaO2%), and probe oxygen saturation (SpO2%). In this retrospective cohort study, the ROX index was calculated by SpO2%, PaO2, and SaO2% separately using the ROX index formula (PaO2 or SaO2 or SpO2 /FiO2)/respiratory rate. ROX was calculated during the first three days of MV treatment and the weaning period daily (SBT). Positive end-expiratory pressure and peak inspiratory pressure values were also recorded during these measurements. These ROX values were used to analyze whether they predict weaning readiness, SBT, extubation failure (EF), and mortality. The study included 107 mechanically ventilated patients. Weaning could be tried in 64 (60%) of the 107 patients; 44 (69%) of the 64 patients succeeded, and extubation was performed. 19 (43%) of 44 patients had EF. ROX values calculated with PaO2 during MV and SBT predicted readiness to wean, EF, and mortality better than ROX values calculated with SaO2 and SpO2. ROX values calculated with PaO2 during the third day of MV had the highest sensitivity and specificity for EF (sensitivity: 81%, specificity: 70% for the ROX<11 value). The results of this study suggest that the calculation of ROX index, not only with SpO2% but also with arterial blood gas PaO2 and SaO2% values, may be helpful in predicting the weaning readiness evaluation, SBT, and extubation success and mortality. Further studies with more patients are necessary to verify and standardize these results.