MORPHOMETRICS OF NORMAL AND HYPOPLASTIC LUNGS IN PRETERM LAMBS WITH GAS AND PARTIAL LIQUID VENTILATION

To test the hypothesis that perfluorochemical (PFC) instillation may r educe the pulmonary trauma commonly associated with conventional gas v entilation, we studied 12 lambs with normal lungs and 10 with pulmonar y hypoplasia secondary to congenital diaphragmatic hernia (CDH). We us ed mechanical ventilation for up to 3.5 h, with and without tracheal i nstillation of LiquiVent PFC liquid. At the end of experimentation lun gs were fixed for morphometrical analysis of their components and pulm onary trauma was evaluated by measurement of the perivascular compress ion index (PCI = % perivascular emphysema/% vessels). In normal lungs good gas exchange and respiratory mechanics were obtained with all mod es of ventilation, with no statistical difference in the index of pulm onary trauma with or without instillation of LiquiVent (P >0.05). In t he hypoplastic lungs, tracheal instillation of PFC liquid after 30 min of conventional gas ventilation significantly improved PaCO2 (from 10 7+/-8 to 55+/-6 mmHg, P <0.05), pH (from 7.00+/-0.03 to 7.29+/-0.04, P <0.05), compliance (from 0.08+/-0.01 to 0.25+/-0.03 ml/cmH(2)O . kg, P <0.05), and ventilatory index (from 1,445+/-148 to 794+/-139, P <0.0 5). Survival was 6/6 animals with PFC ventilation compared to 1/4 with conventional gas ventilation with no more pulmonary trauma (mean PCI 12.6+/-1.8 vs. 11.4+/-4.0%, P >0.05) for a longer mean ventilatory per iod in the PFC group. We conclude that the PFC liquid technique of ven tilation can improve respiratory physiology when conventional gas vent ilation alone is proving inefficient. There was no significant differe nce in pulmonary trauma at morphometrics between gas and partial liqui d ventilation.