Weaning from mechanical ventilation: comparison of two methods

Objectives

To compare two methods of weaning from mechanical ventilation - once-daily trial of spontaneous ventilation (ODT) and pressure support ventilation (PSV) - analyzing (1) total duration of mechanical ventilation, (2) duration of weaning and (3) frequency of successful weaning.

Design

Prospective, randomized trial.

Patients

All patients submitted to mechanical ventilation for at least 48 h that fulfilled criteria for weaning.

Measurements and main results

We studied 125 patients submitted to mechanical ventilation for at least 48 h and that had clinical and radiological evidence of improvement of the process that motivated artificial support of respiration in addiction to the following functional and gasometric criteria: PaO₂/FIO₂ >200 with PEEP of 5 cmH₂O or less; PI Max smaller than -30 cmH₂O; and f/VT <100. Patients could not be under deep sedation or curarization, and when using vasoactive drugs (dopamine or dobutamine) the dose could not exceed 5 μg/kg/min. Sixty-five patients were randomized to ODT and 60 to PVS using a simple randomization technique and sealed envelopes. Weaning was considered successful when the patient was liberated from mechanical ventilation, remaining well for at least 48 h. The two groups were comparable in relation to age, gender, APACHEIII score and cause of respiratory failure. The total duration of mechanical ventilation was 6.1 ± 6.8 days in the ODT group and 8.7 ± 7.5 days in the PSV group (P < 0.05). Weaning duration was 10.6 ± 25.4 h in the ODT group and 38.7 ± 33.0 h in the PSV group (P < 0.001). Fifty-seven patients (87.0%) were successfully weaned in the ODT group versus 45 (75.0%) in the PSV group (P = 0.6). Twelve (26.1%) patients died in the ODT group against 12 (20.0%) in the PSV group (P = NS).

Conclusions

This study, similarly to other recent publications, suggests that most patients submitted to mechanical ventilation can be rapidly removed from the ventilator if they present clinical, gasometric and functional conditions and tolerate well a 2-h trial of spontaneous breathing. This approach results in reduction in the duration of artificial airway, mechanical ventilation and weaning with expected reduction in the frequency of complications and cost of hospitalization.