Proportional assist ventilation with load-adjustable gain factors in critically ill patients: comparison with pressure support
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It is not known if proportional assist ventilation with load-adjustable gain factors (PAV+) may be used as a mode of support in critically ill patients. The aim of this study was to examine the effectiveness of sustained use of PAV+ in critically ill patients and compare it with pressure support ventilation (PS).
Design and setting
Randomized study in the intensive care unit of a university hospital.
A total of 208 critically ill patients mechanically ventilated on controlled modes for at least 36 h and meeting certain criteria were randomized to receive either PS (n = 100) or PAV+ (n = 108). Specific written algorithms were used to adjust the ventilator settings in each mode. PAV+ or PS was continued for 48 h unless the patients met pre-defined criteria either for switching to controlled modes (failure criteria) or for breathing without ventilator assistance.
Failure rate was significantly lower in PAV+ than that in PS (11.1 vs. 22.0%, P = 0.040, OR 0.443, 95% CI 0.206–0.952). The proportion of patients exhibiting major patient–ventilator dyssynchronies at least during one occasion and after adjusting the initial ventilator settings, was significantly lower in PAV+ than in PS (5.6 vs. 29.0%, P < 0.001, OR 0.1, 95% CI 0.06–0.4). The proportion of patients meeting criteria for unassisted breathing did not differ between modes.
PAV+ may be used as a useful mode of support in critically ill patients. Compared to PS, PAV+ increases the probability of remaining on spontaneous breathing, while it considerably reduces the incidence of patient–ventilator asynchronies.
KeywordsControlled modes Assisted modes Patient–ventilator interaction
The following ICU physicians participated in the study by supervising data collections: M. Anastasaki, G. Prinianakis, S. Koumiotaki, G. Xatzakis. We are grateful to the head nurse K. Makrogambraki for her support and cooperation. We are also indebted to the nursing staff of the unit. Many thanks to Professor M. Younes (University of Manitoba) for the helpful suggestions provided.
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