Intratracheal Pulmonary Ventilation versus Conventional Mechanical Ventilation in a Rabbit Model of Surfactant Deficiency

Abstract

Intratracheal pulmonary ventilation (ITPV) enhances the clearance of CO, 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 CO, clearance (vco,), reduce the partial pressure of CO, dioxide in arterial gas (Paco,), 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 CO, concentration was measured. For ventilator rates (respiratory rate) of 30, 45, and 70 breathslmin, the study included two phases: phase I compared CO, clearance and Paco, between ITPV and CMV using similar ventilatory pressures; phase I1 evaluated the effectiveness of ITPV in reducing dPIP and tidal volume (V,), compared with CMV, while maintaining eucapnea. When comparing ITPV and CMV, the following results (mean t SD) were achieved at respiratory rate of 30, 45, and 70 breathslmin, respectively. Phase I ITPV resulted in mean percent reduction of Paco, by 3 1.4 i lo%, 37.1 i 9.7% and 38.3 +-9%; mean percent increase in Vco, by 61.3 i 29%, 56 i 23%, and 98 t 40%, compared with CMV. Phase I1 ITPV resulted in mean percent reduction of dPIP by 35.5 t 14%, 38 i 10.8%, and 37.2 t 13.7%, and mean percent reduction in V, by 34.7 t 12.9%, 36.4 i 15%, and 52.7 t 10.7%, compared with CMV. The changes in Paco,, vco, (phase I), and dPIP and V, (phase 11) 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 CO, clearance and reduces ventilator pressures required for adequate ventilation. We speculate that ITPV can minimize lung barotrauma associated with mechanical ventilation. (Pediatr Res 38: 878-885, 1995) Abbreviations CMV, conventional mechanical ventilation dP,,, distal mean airway pressure dPEEP, distal positive end expiratory pressure dPIP, distal peak inspiratory pressure ETT, endotracheal tube ITPV, intratracheal pulmonary ventilation PFT, pulmonary function test RR, respiratory rate Vco,, minute CO, clearance V,, dead space volume V,, tidal volume Paco,, partial pressure of CO, in arterial gas Pao,, partial pressure of 0, in arterial gas Fio,, fraction of inspired 0, I:E ratio, inspiratory:expiratory ratio F,CO,, mean exiting CO, concentration v,, expiratory minute volume TI, inspiratory time T,, expiratory time ECMO, extracorporeal membrane oxygenation Intratracheal pulmonary ventilation is...

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