A Study Of The Clinical Significance Of Proportional Assist Ventilation

ObjectiveTo investigate the clinical significance of proportional assist ventilation (PAV) by comparing the work of breathing, breathing pattern, hemodynamics and arterial blood gas (ABG) associated with PAV, pressure support ventilation (PSV) and continuous positive airway pressure (CPAP) in intubated and spontaneously breathing post-operation patients. MethodsThirty intubated patients after undergoing cardiac surgery were studied, during early weaning. Elastance and resistance were measured by the inspiratory-hold technique during volume control ventilation. The patients were ventilated in the following order: PAV80;PSV;CPAP, each of the steps lasting for 30 mins. During PAV80, volume assistance (VA) and flow assistance (FA) were set to counterbalance 80% of both elasticand resistive loads, respectively. During PSV, inspiratory positive airway pressure was adjusted to maintain the same tidal volume (VT) as that in PAV80. Work of breathing, breathing pattern, hemodynamics and ABG were monitored. ResultsBoth PAV80 and PSV entailed higher peak inspiratory pressure (PIP, PO.01), higher mean away pressure (Pawm, PO.01), higher VT (PO.01), lower respiratory rate (RR, P<0.01), lower pressure-time product (PTP, PO.01), lower patient work of breathing (WOBp, PO.01), lower ratio of patient work of breathing and total work of breathing (WOBp/WOBt, PO.01), higher PaO2(P<0.01), lower PaCO2(P<0.01) than CPAP. Compared with PSV, PAV80 resulted in a decrease in PIP (PO.05) and a increase in PTP (PO.05), WOBp(P<0.05), WOBp/WOBt(P<0.01). PAV80 and PSV had the same effect on breath pattern and ABG. Hemodynamics remained unchanged during three steps. ConclusionIn intubated patients after undergoing cardiac surgery, PAV was able to provide sufficient respiratory assistance. Compared with PSV, PAV is associated with lower PIP and higher patient work of breathing. They had the same effect on hemodynamics and ABG.