Efficacy of proportional assist ventilation in weaning the patients from ventilator after cardiac surgery

Objective To evaluate the efficacy of proportional assist ventilation( PAV) in weaning the patients from ventilator after cardiac surgery as compared with pressure support ventilation (PSV) and continuous positive airway pressure (CPAP) in terms of respiratory and homodynamic parameters and gas exchange. Methods Forty-six ASAⅠorⅡpatients aged 18-72 yrs, weighing 40-65 kg were studied immediately after cardiac surgery including valve replacement and CABG. As soon as the patients regained consciousness and resumed spontaneous breathing, they were ventilated by PAV80, PSV and CPAP consecutively in randomized order. Each mode lasted for 30 minutes. VT, RR, peak inspiratory pressure (PIP), average airway pressure (Paw), PEEP, work of breathing (WOB), HR, MAP, CVP, and blood gases were monitored. Results During CPAP VT, PIP, Paw, PaO2 and SaO2 were significantly decreased while RR, rapid-shallow-breathing index (RSBI), Ti/Ttot, pressure-time product (PTP), patient's work of breathing (WOBp), pH and PaCO2 were significantly increased ( P 0.01) as compared with PAV80 and PSV modes. PAV80 resulted in a decrease in PIP and Paw and an increase in PTP as compared with PSV. There was no difference in arterial blood gases (PaO2, PaCO2) and MAP, HR and CVP between PAV80 and PSV modes. Conclusion PAV is a mode of choice in weaning the patients from ventilator after cardiac surgery.