The most important clinical application of pressure support ventilation is probably the weaning of patients from mechanical ventilation. In one study, the efficacy of pressure support was greater than with other techniques such as T-piece trials or synchronized intermittent mandatory ventilation. This multicenter prospective randomized trial showed that the probability of complete withdrawal of mechanical ventilation 21 days after commencement of weaning was twice as high with pressure support ventilation than with synchronized intermittent mandatory ventilation. The period of weaning was also significantly decreased from a mean duration of 9.3 days for the other two techniques to 5.7 days using pressure support ventilation ( Brochard ef a/ 1.994).
The above results were not reproduced in another prospective multicenter randomized trial published some months later (.Esteban 1995). This second study showed that a single daily trial of spontaneous breathing with a T-piece was able to shorten the period of weaning significantly (median of 3 days compared with a median of 4 days with pressure support and 5 days with synchronized intermittent mandatory ventilation).
The contradictory results found in these two studies could be accounted for by the different methodologies used. In particular, modification of the pressure support level and criteria to extubate the patient under pressure support ventilation differed between the two studies. These criteria were more conservative in the second study. However, these investigations do indicate that the way a technique is used is as important as the technique itself; too rigid criteria for extubation probably lengthen the period of weaning.
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