Proportional assist ventilation with load-adjustable gain factors in critically ill patients: comparison with pressure support.

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.