COMPARISON OF 3 METHODS OF GRADUAL WITHDRAWAL FROM VENTILATORY SUPPORT DURING WEANING FROM MECHANICAL VENTILATION

Several modalities of ventilatory support have been proposed to gradually withdraw patients from mechanical ventilation, but their respective effects on the outcome of weaning from mechanical ventilation are not known. We conducted a randomized trial in three intensive care units in mechanically Ventilated patients who met standard weaning criteria. Those who could not sustain 2 h of spontaneous breathing were randomly assigned to be weaned with T-piece trials, with synchronized intermittent mandatory ventilation (SIMV), or with pressure support ventilation (PSV). Specific criteria for performing tracheal extubation were defined for each modality. The number of patients who could not be separated from the ventilator at 21 d (i.e., who failed to wean) was compared between the groups. Patients in whom tracheal intubation was required in a 48-h period following extubation were also classified as failures. Among 456 mechanically ventilated patients who met weaning criteria, 109 entered into the study (35 with T piece, 43 with SIMV, and 31 with PSV). The three groups were comparable in terms of etiology of disease or characteristics at entry in the study. When all causes for weaning failure were considered, a lower number of failures was found with PSV than with the other two modes, with the difference just reaching the level of significance (23% for PSV, 43% for T piece, 42% for SIMV; p = 0.05). After excluding patients whose weaning was terminated for complications unrelated to the weaning process, the difference became highly significant (8% for PSV Versus 33% and 39%, p < 0.025). Also, the probability of remaining on mechanical ventilation, calculated using the Kaplan-Meier estimate, was found to be significantly lower with PSV (p < 0.03). Weaning duration was shorter with PSV (p < 0.05), as was total length of stay in the intensive care unit (p < 0.01). The duration of weaning was explained first by the etiology of the disease and second by the mode of ventilation. We conclude that in this study, the outcome of weaning from mechanical ventilation was influenced by the ventilatory strategy chosen, and the use of PSV resulted in significant improvement compared with other strictly defined weaning protocols using T piece or SIMV.