The Ventilatory Effect of Hybrid Ventilation in Rabbits

ABSTRACT

PURPOSE: Intratracheal pulmonary ventilation (ITPV) is developed to decrease dead space ventilation. A reverse thrust catheter (RTC) is introduced into an endotracheal tube through an adapter. Bias gas through the RTC exits from the catheter tip. The flow of gas is redirected outward away from the lung. Gas is intermittently introduced into the lung as tidal volume (VT) by an expiratory valve. ITPV can be combined with pressure control mode, resulting in hybrid ventilation (HV). We hypothesized that HV might decrease VT, compared with volume controlled ventilation (VCV) or pressure controlled ventilation (PCV) alone. METHODS: HV was compared with VCV and PCV in 7 tracheostomized rabbits. We aimed at maintaining PaCO2 levels normal as the respiratory rates (RR) were set at 20, 40, 80, and 120/min. Blood pressure and airway pressures were monitored and dead space ratio was calculated. RESULTS: The dead spaces (VD) of VCV are 30+/-4 mL, 18+/-4 mL, 14+/-4 mL, and 12+/-5 mL and the VD of PCV are 24+/-6 mL, 16+/-3 mL, 15+/-4 mL and 12+/-4 mL at the respiratory rates of 20/min, 40/min, 80/min, and 120/min, respectively. The VD of HV are 13+/-6 mL, 9+/-3 mL, 7+/-2 mL, and 5+/-1 mL, respectively. The VT and PIP of HV are significantly lower than those of VCV and PCV at the same RR. CONCLUSION: It can be concluded that HV can be applied to minimize the airway pressures and dead space ventilation of VCV and PCV.