Studies published by Brochard et al. and by Esteban et al. came to different conclusions about the best technique of weaning from mechanical ventilation. Although the association of synchronized intermittent mandatory ventilation (SIMV) with pressure support ventilation (PSV) is frequently used and considered as a physiologic form of weaning, no prospective randomized study compared this technique to synchronized intermittent mandatory ventilation or to pressure support ventilation used singly. The authors compared these three weaning methods to determine the one that is associated with the shortest weaning time and the smallest frequency of unfavorable outcome. Methods: The authors analyzed prospectively 72 consecutive patients submitted to mechanical ventilation for at least 24 hours and that had clinical, gasometric, and respiratory criteria for weaning. The patients were randomized in three groups (SIMV, PSV, SIMV+PSV). Stringent criteria were used in the application of each technique to define success or failure of the procedure. Results: The groups (SIMV = 21, PSV = 25 and SIMV+PSV = 26 patients) were similar with respect to age, score APACHE III and diseases. Mean duration of weaning was 1.7 ± 1.2 days with SIMV, 2.5 ± 1.6 days with PSV, and 2.1 ± 1.5 days with SIMV+PSV. Four (19.0 %) patients failled to wean in the SIMV group, nine (36.0%) in PSV and two (7.7%) in SIMV+PSV. Conclusions: This study shows a good performance of SIMV+PSV for weaning patients from mechanical ventilation and unfavorable results with support ventilation that can not be attributed to homogeneity between the groups, nor to the methodologies or equipments used.

Keywords: Weaning. Synchronized intermittent mandatory ventilation. Pressure support ventilation.