Synchronized Intermittent Mandatory Ventilation With and Without Pressure Support Ventilation in Weaning Patients With COPD From Mechanical Ventilation: Discussion
At the end of this study, all patients with COPD were extubated as they had undergone long periods of SB without clinical or/and blood gas value deterioration. The duration of the weaning period appeared lower in group 1 than in group 2: 4.2 ±0.8 days (SIMV/PSV) vs 5.3±1.0 days (SIMV), but the difference did not reach the significance level (p=0.0545) Link canadian neighbor pharmacy. Two patients of group 2 were reintubated less than 72 h after initial extubation, placed under SIMV mode for 2 more days, and thereafter extubated. In group 1, no patient needed reintubation. No significant difference was found in the need for reintubation between the two groups.
This study compares two modes of mechanical ventilation: SIMV/PSV vs SIMV for weaning 19 patients with COPD. Whereas our patients satisfied the widely accepted criteria for weaning success, they could not tolerate any reduction in SIMV rate without clinical and/or blood gas value deterioration. This is not surprising since it has been shown previously that conventional bedside weaning criteria have poor predictive capacity in patients requiring prolonged MV (>24 h). Multiple weaning criteria have been proposed and evaluated but no one has proved useful enough to obtain wide consensus.
Indeed, Morganroth and coworkers have shown that conventional parameters did not significantly change when patients requiring long-term MV progressed from a period of respirator dependence to a period of successful weaning. Tobin has recently predicted that three factors could account for the poor performance of these conventional predictors: (1) populations and their derived weaning criteria may differ from one study to another; (2) the method of making the measurements may differ between studies; and (3) conventional indices might be inaccurate. We did not validate in our hospital the weaning criteria we used. Nevertheless, these criteria are taken from the accepted literature and are widely used in the clinical setting throughout the world. Newer weaning criteria have been proposed since this work was begun. However, even these new criteria have not been independently validated.
Because we had been unable to successfully wean or extubate these patients, we decided to propose a gradual decrease in both the volumetric (SIMV) and barometric (PSV) assistances of ventilation during the weaning period. The SIMV rate was decreased in a standard way, once or twice a day, depending on the patient’s tolerance. This was based on published clinical signs of respiratory muscle fatigue (which have been questioned), but also on the concomitant presence of respiratory acidosis, a more objective index of ventilatory failure.