INTRATRACHEAL PULMONARY VENTILATION VERSUS CONVENTIONAL MECHANICAL VENTILATION IN A RABBIT MODEL OF SURFACTANT DEFICIENCY

Intratracheal pulmonary ventilation (ITPV) enhances the clearance of CO2 from dead space and lungs by a bias flow of gas administered in the distal trachea. ITPV flow is continuously administered through a separate catheter placed within an endotracheal tube (ETT). After exiting from catheter's tip in the distal trachea, the flow of gas is redirected outward away from the lungs. We hypothesized that, compared with conventional mechanical ventilation (CMV), ITPV may increase minute CO2 clearance (Vover dot CO2), reduce the partial pressure of CO2 dioxide in arterial gas (PaCO2), and reduce distal tracheal peak inspiratory pressure (dPIP). We induced surfactant deficiency in 15 adult rabbits by lung lavage with 10 mL/kg normal saline. Animals were ventilated through a double-lumen 4.0 ETT, inserted through a tracheotomy incision. dPIP, distal positive end expiratory pressure, and distal mean airway pressure were monitored, and the mean exhaled CO2 concentration was measured. For ventilator rates (respiratory rate) of 30, 45, and 70 breaths/min, the study included two phases: phase I compared CO2 clearance and PaCO2 between ITPV and CMV using similar ventilatory pressures, phase II evaluated the effectiveness of ITPV in reducing dPIP and tidal volume (V-t), compared with CMV, while maintaining eucapnea. When comparing ITPV and CMV, the following results (mean +/- SD) were achieved at respiratory rate of 30, 45, and 70 breaths/min, respectively. Phase I ITPV resulted in mean percent reduction of PaCO2 by 31.4 +/- 10%, 37.1 +/- 9.7% and 38.3 +/- 9%; mean percent increase in Vover dot CO2 by 61.3 +/- 29%, 56 +/- 23%, and 98 +/- 40%, compared with CMV. Phase II ITPV resulted in mean percent reduction of dPIP by 35.5 +/- 14%, 38 +/- 10.8%, and 37.2 +/- 13.7%, and mean percent reduction in V-t by 34.7 +/- 12.9%, 36.4 +/- 15%, and 52.7 +/- 10.7%, compared with CMV. The changes in PaCO2, Vover dot CO2 (phase I), and dPIP and V-t (phase II) were all significantly more than 25% (p < 0.05). Oxygenation and pH were not significantly different between ITPV and CMV. We conclude that, in a surfactant deficiency rabbit model, ITPV is an efficient mode of assisted ventilation that increases CO2 clearance and reduces ventilator pressures required for adequate ventilation. We speculate that ITPV can minimize lung barotrauma associated with mechanical ventilation.