A physiologic comparison of proportional assist ventilation with load-adjustable gain factors (PAV+) versus pressure support ventilation (PSV)
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 (swingPdi), and pressure–time products of the transdiaphragmatic (PTPdi) pressures. Inspiratory (delaytrinsp) and expiratory (delaytrexp) trigger delays, time of synchrony (timesyn), and asynchrony index (AI) were assessed.
Compared to PAV+, during PSV trials, the mechanical inspiratory time (Tiflow) was significantly longer than patient inspiratory time (Tipat) (p < 0.05); Tipat showed a prolongation between PSV1 and PAV+, significant comparing PAV+ and PSV2 (p < 0.05). PAV+ significantly reduced delaytrexp (p < 0.001). The portion of tidal volume (VT) delivered in phase with Tipat (VTpat/VTmecc) 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.
KeywordsPatient–ventilator synchrony Proportional assist ventilation Pressure support ventilation
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