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Intensive Care Med. 2011 Sep;37(9):1494-500. doi: 10.1007/s00134-011-2297-y. Epub 2011 Jul 1.

A physiologic comparison of proportional assist ventilation with load-adjustable gain factors (PAV+) versus pressure support ventilation (PSV).

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Department of Intensive Care and Anaesthesia, Catholic University of Rome, Policlinico Agostino Gemelli, Largo F.Vito 1, 00168 Rome, Italy.



To compare patient-ventilator interaction during PSV and PAV+ in patients that are difficult to wean.


This was a physiologic study involving 11 patients. During three consecutive trials (PSV first trial--PSV1, followed by PAV+, followed by a second PSV trial--PSV2, with the same settings as PSV1) we evaluated mechanical and patient respiratory pattern; inspiratory effort from excursion Pdi (swing(Pdi)), and pressure-time products of the transdiaphragmatic (PTPdi) pressures. Inspiratory (delay(trinsp)) and expiratory (delay(trexp)) trigger delays, time of synchrony (time(syn)), and asynchrony index (AI) were assessed.


Compared to PAV+, during PSV trials, the mechanical inspiratory time (Ti(flow)) was significantly longer than patient inspiratory time (Ti(pat)) (p < 0.05); Ti(pat) showed a prolongation between PSV1 and PAV+, significant comparing PAV+ and PSV2 (p < 0.05). PAV+ significantly reduced delay(trexp) (p < 0.001). The portion of tidal volume (VT) delivered in phase with Ti(pat) (VT(pat)/VT(mecc)) was significantly higher during PAV+ (p < 0.01). The time of synchrony was significantly longer during PAV+ than during PSV (p < 0.001). During PSV 5 patients out of 11 showed an AI greater than 10%, whereas the AI was nil during PAV+.


PAV+ improves patient-ventilator interaction, significantly reducing the incidence of end-expiratory asynchrony and increasing the time of synchrony.

[Indexed for MEDLINE]

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