Comparison of intratracheal pulmonary ventilation and hybrid intratrachealpulmonary ventilation with conventional mechanical ventilation in a rabbitmodel of acute respiratory distress syndrome by saline lavage

Objectives: To study changes in PaCO2 and PaO2 during intratracheal pulmona ry ventilation (ITPV) and hybrid intratracheal pulmonary ventilation (h-ITP V) compared with conventional mechanical ventilation (CWV) in a rabbit mode l of respiratory failure, and to define the technique of h-ITPV that combin es conventional mechanical ventilation and ITPV. Design: Prospective, interventional study. Subjects: Twelve adult New Zealand White rabbits. Interventions: Surfactant deficiency was induced by saline lavage, and rabb its were randomized to either ITPV or h-ITPV. The study consisted of four p hases: phase 0, CMV after saline lavage, ventilator rate 30 breaths/min; ph ase I, ITPV or h-ITPV initiated at the same pressure and rate as in phase 0 ; phase II, ITPV or 1.0 L/min h-ITPV bias flow, with peak inspiratory press ure (PIP) decreased and ventilator rate increased to achieve the lowest tid al volume while maintaining adequate gas exchange; and phase III, animals r eturned to CMV. Measurements and Main Results: In phase I, no difference in PaCO2 was obser ved between ITPV, h-ITPV, or CMV. There was a decrease in PaO2 when switchi ng from CMV to ITPV but not to h-ITPV. In phase II, it was possible to decr ease PIP (average of 37% for ITPV and 36% for h-ITPV) and tidal volume (ave rage of 64% for ITPV and 53% for h-ITPV) without compromising gas exchange (p < .05). Oxygenation tended to improve from phase 0 to the end of phase I I. In phase III, PaCO2 increased (average of 71% for ITPV and 79% for h-ITP V) and ph decreased (p < .05). Normocapnia was achieved using significantly higher PIP and tidal volume, compared with phase 0 (p < .05). Conclusions: ITPV and h-ITPV can effectively ventilate and oxygenate rabbit s with surfactant-deficient lungs at tidal volumes and therefore pressures tower than required with CMV. Maximum benefit appears to occur at high vent ilator rates. These findings suggest that both modes of ventilation may rep resent powerful new tools in the management of patients with acute respirat ory failure.