The effect of positive end-expiratory pressure during partial liquid ventilation in acute lung injury in piglets

Objectives: To investigate the effects of positive end-expiratory pressure (PEEP) application during partial liquid ventilation (PLV) on gas exchange, lung mechanics, and hemodynamics in acute lung injury. Design: Prospective, randomized, experimental study. Setting: University research laboratory. Subjects: Six piglets weighing 7 to 12 kg. Interventions: After induction of anesthesia, tracheostomy, and controlled mechanical ventilation, animals were instrumented with two central venous c atheters, a pulmonary artery catheter and two arterial catheters, and an ul trasonic flow probe around the pulmonary artery. Acute lung injury was indu ced by the infusion of oleic acid (0.08 mL/kg) and repeated lung lavage pro cedures with 0.9% sodium chloride (20 mL/kg), The protocol consisted of fou r different PEEP levels (0, 5, 10, and 15 cm H2O) randomly applied during P LV. The oxygenated and warmed perfluorocarbon liquid (30 mL/kg) was instill ed into the trachea over 5 mins without changing the ventilator settings. Measurements and Main Results: Airway pressures, tidal volumes, dynamic and static pulmonary compliance, mean and expiratory airway resistances, and a rterial blood gases were measured. In addition, dynamic pressure/volume loo ps were recorded. Hemodynamic monitoring included right atrial, mean pulmon ary artery, pulmonary capillary wedge, and mean systemic arterial pressures and continuous flow recording at the pulmonary artery. The infusion of ole ic acid combined with two to five lung lavage procedures induced a signific ant reduction in PaO2/FIO2, from 485 +/- 28 torr (64 +/- 3.6 kPa) to 68 +/- 3.2 torr (9.0 +/- 0.4 kPa) (p < .01) and in static pulmonary compliance fr om 1.3 +/- 0.06 to 0.67 +/- 0.04 mL/cm H2O/kg (p < .01). During PLV, PaO2/F IO2 increased significantly from 68 +/- 3.2 torr (8.9 +/- 0.4 kPa) to >200 torr (>26 kPa) (p < .01). The highest Pac, values were observed during PLV with PEEP of 15 cm H2O. Deadspace ventilation was lower during PLV when PEE P levels of 10 to 15 cm H2O were applied. There were no differences in hemo dynamic data during PLV with PEEP levels up to 10 cm H2O. However, PEEP lev els of 15 cm H2O resulted in a significant decrease in cardiac output. Dyna mic pressure/volume loops showed early inspiratory pressure spikes during P LV with PEEP levels of 0 and 5 cm H2O. Conclusions: Partial liquid ventilation is a useful technique to improve ox ygenation in severe acute lung injury. The application of PEEP during PLV f urther improves oxygenation and long mechanics. PEEP levels of 10 cm H2O se em to be optimal to improve oxygenation and lung mechanics.