Prediction of extubation outcome in mechanically ventilated patients: Development and validation of the Extubation Predictive Score (ExPreS)

Abstract

Despite the best efforts of intensive care units (ICUs) professionals, the extubation failure rates in mechanically ventilated patients remain in the range of 5%-30%. Extubation failure is associated with increased risk of death and longer ICU stay. This study aimed to identify respiratory and non-respiratory parameters predictive of extubation outcome, and to use these predictors to develop and validate an "Extubation Predictive Score (ExPreS)" that could be used to predict likelihood of extubation success in patients receiving invasive mechanical ventilation (IMV). Derivation cohort was composed by patients aged ≥18 years admitted to the ICU and receiving IMV through an endotracheal tube for >24 hours. The weaning process followed the established ICU protocol. Clinical signs and ventilator parameters of patients were recorded during IMV, in the end phase of weaning in pressure support ventilation (PSV) mode, with inspiratory pressure of 7 cm H2O over the PEEP (positive end expiratory pressure). Patients who tolerated this ventilation were submitted to spontaneous breathing trial (SBT) with T-tube for 30 minutes. Those who passed the SBT and a subsequent cuff-leak test were extubated. The primary outcome of this study was extubation success at 48 hours. Parameters that showed statistically significant association with extubation outcome were further investigated using the receiver operating characteristics (ROC) analysis to assess their predictive value. The area under the curve (AUC) values were used to select parameters for inclusion in the ExPreS. Univariable logistic regression analysis and ROC analysis were performed to evaluate the performance of ExPreS. Patients' inclusion and statistical analyses for the prospective validation cohort followed the same criteria used for the derivation cohort and the decision to extubate was based on the ExPreS result. In the derivation cohort, a total of 110 patients were extubated: extubation succeeded in 101 (91.8%) patients and failed in 9 (8.2%) patients. Rapid shallow-breathing index (RSBI) in SBT, dynamic lung compliance, duration of IMV, muscle strength, estimated GCS, hematocrit, and serum creatinine were significantly associated with extubation outcome. These parameters, along with another parameter-presence of neurologic comorbidity-were used to create the ExPreS. The AUC value for the ExPreS was 0.875, which was higher than the AUCs of the individual parameters. The total ExPreS can range from 0 to 100. ExPreS ≥59 points indicated high probability of success (OR = 23.07), while ExPreS ≤44 points indicated low probability of success (OR = 0.82). In the prospective validation cohort, 83 patients were extubated: extubation succeeded in 81 (97.6%) patients and failed in 2 (2.4%) patients. The AUC value for the ExPreS in this cohort was 0.971. The multiparameter score that we propose, ExPreS, shows good accuracy to predict extubation outcome in patients receiving IMV in the ICU. In the prospective validation, the use of ExPreS decreased the extubation failure rate from 8.2% to 2.4%, even in a cohort of more severe patients.

Fig 1. Flowchart of the derivation cohort.

SBT: Spontaneous Breathing Trial.

Fig 2. ROC curves for RSBI in SBT (A), Dynamic Lung Compliance (B), Days of Mechanical Ventilation (C), Muscle Strength (D), Estimated GCS (E), Hematocrit (F), and Creatinine (G) used to distinguish the extubation success group from the failure group.

In the ROC curve analysis, the AUC was highest for RSBI in SBT (0.778), followed by the Dynamic Lung Compliance (0.700), Days of Mechanical Ventilation (0.686), Muscle Strength (0.662), Estimated GCS (0.630), Hematocrit (0.614), and Creatinine (0.587). ROC curve: receiver operating characteristic curve; RSBI in SBT: Rapid Shallow Breathing Index in Spontaneous Breathing Trial; Estimated GCS: Glasgow Coma Scale; AUC: area under the curve, CI: confidence interval.

Fig 3. Extubation Predictive Score—ExPreS.

Fig 4. ROC curves for ExPreS from derivation cohort, used to distinguish the extubation success group from the failure group.

In the ROC curve analysis, the AUC was 0.875. ROC curve: receiver operating characteristic curve; ExPreS: Weaning and Extubation Predictive Index; AUC: area under the curve, CI: confidence interval.

Fig 5. Extubation success probability of ExPreS.

The sensitivity, specificity and success rate (%) of ExPreS ≤ 44 points, ExPreS from 45 to 58 points, and ExPreS ≥ 59 points.

Fig 6. Flowchart of the validation cohort.

SBT: Spontaneous Breathing Trial.

Fig 7. ROC curves for ExPreS from validation cohort, used to distinguish the extubation success group from the failure group.

In the ROC curve analysis, the AUC was 0.971. ROC curve: receiver operating characteristic curve; ExPreS: Weaning and Extubation Predictive Index; AUC: area under the curve, CI: confidence interval.