Outcome of weaning from mechanical ventilation may be due to differences in patient population and the weaning parameters used. In order to determine the accuracy of the weaning parameters and the relationship between the etiology of respiratory failure and the outcome of weaning trial, we prospectively studied 127 patients receiving mechanical ventilation who met standard weaning criteria. Successful weaning occurred in 85% (108 of 127 patients): 51 of 54 (94.4%) patients with cardiac failure, 26 of 30 (86.67%) patients with Obstructive disease, 12 of 22 (54.54%) patients with neurologic disorders, 19 0f 21 (90.48%) patients with Infections. Ventilatory support was reinstituted in 6.3% (8 of 127) patients: 1.85% (1 of 54) patients with cardiac failure, 6.7% (2 of 30) patients with COPD, 18.18% (4 of 22) patients with neurologic disorders,4.76% (1 of 21) patients with infections. Reintubation was required in 3.7% (2 of 54) patients with cardiac failure, 6.7% (2 of 30) patients with obstructive diseases, 27% (6 of 22) patients and 4.7% (1 of 21) patients with infections. The reintubation rate was 8.7%, of which the highest reintubation rate occurred in neurologic patients (27%). The mortality rate in the reintubated patients was 64%. The duration of mechanical ventilation (>7 days) prior to weaning and age (>70 years old) are factors, which contributed to weaning failure.
The CROP (Compliance, Rate, Oxygenation, Pressure) index had the highest predictive power for predicting the outcome of weaning and is the single most accurate predictor, followed by RSBI (Rapid Shallow Breathing). This observation holds true when the etiologic groups were considered. Majority of the patients who were successfully extubated had RSBI <100 and CROP index of 17 while majority of those who failed had RSBI ≥ 100 and CROP index of 12. In the whole study population, the RSBI and CROP index combination and CROP index and Pimax combination showed a greater predictive power than the rest of the combinations. In the neurologic group, the RSBI and CROP index combination, CROP and Cdyn, and CROP and Pimax combinations showed a greater predictive power than the rest of the combinations.
Our study recommends the use of CROP index and RSBI to predict weaning outcome.