Ventilation & weaning · Predicting weaning success
A prospective study of indexes predicting the outcome of trials of weaning
| Design | Prospective diagnostic accuracy study within a controlled clinical trial |
|---|---|
| Treatment | Rapid shallow breathing index (f/VT) measured before a weaning trial |
| Control | Other weaning predictors including maximal inspiratory pressure, minute ventilation and compliance |
| Population | 100 mechanically ventilated patients undergoing weaning trials |
| Follow-up | Weaning outcome |
| Primary endpoint | Accuracy in predicting weaning success or failure |
| Result | Sensitivity was highest for maximal inspiratory pressure (1.00) and close behind for the f/VT ratio (0.97). Specificity was highest for f/VT (0.64) and lowest for maximal inspiratory pressure (0.11). The f/VT ratio was the best predictor of successful weaning, and f/VT together with maximal inspiratory pressure the best predictors of failure. |
| Secondary endpoints | Receiver operating characteristic curve area for each index |
Rapid shallow breathing, as reflected by the f/VT ratio, was the most accurate predictor of failure, and its absence the most accurate predictor of success, in weaning patients from mechanical ventilation.
The trial authors, in the published abstract
Gave the world f/VT below 105, still quoted at the bedside 35 years on. Its specificity was only 0.64 in the original data, so it was never the decisive test it became in practice — a screening aid, not a gate.
Yang KL, Tobin MJ. A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med 1991 May 23;324(21):1445-50.