A variety of methods have been employed to help wean patients from prolonged ventilatory support. Although synchronized intermittent mandatory ventilation is probably the most widely used, it has not been shown to be clearly superior to T piece or pressure support weaning. Regardless of the method you choose, begin weaning before the patient's lung function has returned to normal or baseline levels and end when the patient shows the minimum capacity necessary to sustain himself off the ventilator. The patient's response to the change in the level of ventilatory support governs the rapidity of weaning. The rapid shallow breathing index can be useful in predicting weaning outcome, as is the patient's ability to tolerate a weaning trial.