The findings of this study contribute to the understanding of factors associated with successful extubation and the predictive capacity of various variables in the weaning process. Our results showed a significant association between a successful SBT and the objective measurement of cough and VDC. We also found a significant association between successful extubation and the presence of successful SBT, objective measurement of cough and VDC. Integrating our model would enhance clinicians' ability to identify SBT success, improving the weaning process. However, further refinement and validation are essential to maximize its clinical utility.
Most existing studies focus on determining a patient's suitability for an SBT individually, but to our knowledge, no model proposes the combined use of these tests (9–11, 14, 15). Our model demonstrated that the objective measurement of cough, often subjectively assessed by clinicians during the weaning process when combined with diaphragmatic ultrasound (as described in Eq. 1), can discriminate to some extent patients who are likely to have a successful SBT. The predictive model for successful SBT, derived from multivariate logistic regression analysis, exhibited limited discriminatory capacity, suggesting that the model can poorly predict successful SBT. Consequently, it is apparent that SBT cannot be fully replaced by alternative objective measures based on these results.
The use of clinical tests, severity scores, hemodynamic conditions, and ventilator weaning tests that may require patient input to improve the discriminatory ability of SBTs may be limited by factors such as residual sedative effects, delirium, or patient understanding (23, 24, 27). Regarding extubation success, our study identified several significant predictors, including SBT, objective measurement of cough, and VDC. The multivariate logistic regression model incorporating these variables showed excellent discriminatory capacity. The good calibration of the model, as indicated by the non-significant Hosmer-Lemeshow test, further supports its reliability.
Our study utilized both T-piece and pressure support ventilation as SBT, as they have been shown to have a comparable predictive power for successful extubation in critically ill patients (27). Failure to extubate is reported in approximately 20% of extubated patients. Our study revealed that while the SBT test remains the best predictor of successful extubation, the objective measurement of cough and VDC also show a significant correlation with extubation success. Although cough is recognized as a useful test for facilitating extubation decisions, it is rarely used in a standardized manner (28), we successfully standardized the objective measurement of cough, ensuring its validation and reproducibility among observers.
Diaphragmatic ultrasound has been evaluated in multiple publications to determine its usefulness in predicting extubation success, yielding conflicting results. However, a common factor among these studies is that the velocity of diaphragmatic contraction appears to be the measure most strongly correlated with successful extubation (24, 25). In our study, cough and VDC showed an association with extubation success, although with less discriminative capacity compared to SBT. However, when we included SBT, VDC, and the objective measurement of cough in our model (Eq. 2), the discriminative capacity significantly improved for predicting extubation success.
Limitations
This study was not a clinical experiment and may be influenced by confounding bias. Although the sample was representative, the data must be evaluated in the context of a prospective, multicenter observational study. Also, while internal validation was done, external validation has not yet been done. On the other hand, the strengths of the study lie in its prospective and multicenter design, the rigor of the measurements, the frequency of diaphragmatic ultrasounds with calculation of averages, the validation and reproducibility of the objective measurement of cough, and the lack of collaboration of the patient in different tests. All tests were performed by trained intensive care personnel, and transthoracic ultrasound was performed at the bedside by experienced physicians.