Prone Positioning Improves Oxygenation Without Adverse Hemodynamic Effects during Partial Liquid Ventilation in a Canine Model of Acute Lung Injury

BACKGROUND : Partial liquid ventilation (PLV) and prone positioning can improve the arterial oxygenation (PaO(2)) in acute lung injury (ALI). We evaluated the effect of prolonged prone positioning during partial liquid ventilation (PLV) in a canine model of acute lung injury. METHODS : Six mongrel dogs (weighing 17.4±0.7 kg each) were anesthetized, intubated and mechanically ventilated. After 1 hour of baseline stabilization, the dogs’ lungs were instilled with 40 mL/kg perfluorocarbon (PFC). PLV was first performed in the supine position for 1 hour (S1), then in the prone position for 3 hours with hourly measurements (P1, P2, P3), and finally, PLV was performed with the animal turned back to the supine position for 1 hour (S2). RESULTS : After instillation of the PFC, the PaO(2) significantly increased from 99.2±32.6 mmHg at baseline to 198.1±59.2 mmHg at S1 (p=0.001). When the dogs were turned to the prone position, the PaO(2) further increased to 288.3±80.9 mmHg at P1 (p=0.008 vs. S1): this increase was maintained for 3 hours, but the PaO(2) decreased to 129.4±62.5 mmHg at S2 (p<0.001 vs. P3). Similar changes were seen in the shunt fraction. There were no significant differences for the systemic hemodynamic parameters between the prone and supine positions. CONCLUSION : Prolonged prone positioning during PLV in an animal model of ALI appears to improve oxygenation without any hemodynamic compromise.