Partial liquid ventilation (PLV) compared to inhaled nitric oxide (INO) in an animal model of acute lung injury (ALI): Effects on pulmonary gas exchange

Introduction: In ALI, iNO is effective in improving arterial oxygenation by vasodilating ventilated lung regions and thereby reducing intrapulmonary shunt (Q_s/Q_t). PLV has been suggested to reduce Q _s/Q_t mainly by recruitment of collapsed alveolar regions. In this study we compared the effects of iNO and PLV on arterial oxygenation and Q_s/Q_t in an animal model of ALI. Methods: 22 piglets (25±5 kg) were anesthetized and ventilated in a volume-controlled mode (FIO₂ 1.0). After induction of ALI by surfactant depletion, the animals were randomly assigned to either receive PLV (30 ml/kg initially followed by 4 ml/kg hourly, PF 5080, 3M, Neuss, Germany, n=7), or to inhale 20 ppm NO continuously (n=7), or to receive no further treatment (n=8, controls). Hemodynamics and pulmonary gas exchange were measured hourly. Statistical analysis was performed by Kruskal-Wallis-ANOVA with post-hoc comparisons using Mann-Whitney-U test and Bonferroni correction (* denotes p<0.05 compared to controls, # denotes p*0.05 compared to iNO). Results: (Mean ± SEM) Induction of ALI decreased PaO₂ from 547±12 mmHg (pre-lavage) to 61±3 mmHg, and increased Q_s/Q_t from 12±1 to 52±3 %. PLV induced an increase in PaO₂ to 142±50, 233±54*, 301±36*#, and 319±41*# mmHg (corresponding changes in Q_s/Q_t from All were -15±6, -25±5*, -28±4*, and -31±5* %; values at 1,2,3,and 4 h after induction of ALI). In the iNO group PaO₂ increased to 107±12*, 108±9*, 109±10*, and 115±15 mmHg (changes in Q_s/Q_t were -16±4*, -15±4*, -14±6, and -13±9 %). Controls remained at low PaO₂ levels of 66±5, 56±5, 58±7, and 65±9 mmHg, corresponding changes in Q_s/Q_t from ALI were -1±2, 3±4, 4±4, and 5±9 %. During the protocol, n=4 controls and n=1 animal from the iNO group died. Conclusion: In this animal model of ALI, both PLV and iNO significantly improved pulmonary gas exchange compared to controls. However. PLV appears to be more effective possibly due to its abibility to recruit atelectatic lung regions.