EVALUATION OF GAS-EXCHANGE, PULMONARY COMPLIANCE, AND LUNG INJURY DURING TOTAL AND PARTIAL LIQUID VENTILATION IN THE ACUTE RESPIRATORY-DISTRESS SYNDROME

Objective: To investigate whether pulmonary compliance and gas exchang e will be sustained during ''total'' perfluorocarbon liquid ventilatio n followed by ''partial'' perfluorocarbon liquid ventilation when comp ared with gas ventilation in the setting of the acute respiratory dist ress syndrome (ARDS), Study Design: A prospective, controlled, laborat ory study, Setting: A university research laboratory, Subjects: Ten sh eep, weighing 12.7 to 25.0 kg, Interventions: Lung injury was induced in ten young sheep, utilizing a right atrial injection of 0.07 mL/kg o f oleic acid followed by saline pulmonary lavage, Bijugular venovenous extracorporeal life support access, a pulmonary artery catheter, and a carotid artery catheter were placed, When the alveolar-arterial O-2 gradient was greater than or equal to 600 torr and Pao(2) <50 torr (le ss than or equal to 6.7 kPa) with an Fio(2) of 1.0, extracorporeal lif e support was instituted, For the first 30 mins on extracorporeal life support, all animals were ventilated with gas, Animals were then vent ilated with equal tidal volumes of 15 mL/kg during gas ventilation (n = 5) over the ensuing 2.5 hrs, or with total liquid ventilation for 1 hr, followed by partial liquid ventilation for 1,5 hrs (total/partial liquid ventilation, n = 5), Measurements and Main Results: An increase in physiologic shunt (gas ventilation = 69 +/- 11%, total/partial liq uid ventilation = 71 +/- 3%) and a decrease in static total pulmonary compliance measured at 20 mL/kg inflation volume (gas ventilation = 0. 48 +/- 0.03 mL/cm H2O/kg, total/partial liquid ventilation = 0.50 +/- 0.17 mL/cm H2O/kg) were observed in both groups with induction of lung injury, Physiologic shunt was significantly reduced during total and partial liquid ventilation when compared with physiologic shunt observ ed in the gas ventilation animals (gas ventilation = 93 +/- 8%, total liquid ventilation = 45 +/- 11%, p <.001; gas ventilation = 95 +/- 3%, partial liquid ventilation = 61 +/- 12%, p <.001), while static compl iance was significantly increased in the total, but not the partial li quid ventilated animals when compared with the gas ventilated group (g as ventilation = 0.43 +/- 0.03 mL/cm H2O/kg, total liquid ventilation = 1.13 +/- 0.18 mL/cm H2O/kg, p <.001; gas ventilation = 0.41 +/- 0.02 mL/cm H2O/kg, partial liquid ventilation = 0.47 +/- 0.08, p = .151), In addition, the extracorporeal life support flow rate required to mai ntain adequate oxygenation was significantly lower in the total/partia l liquid ventilation group when compared with that of the gas ventilat ion group (gas ventilation = 89 +/- 7 mL/kg/min, total liquid ventilat ion = 22 +/- 10 ml/kg/min, p <.001; gas ventilation = 91 +/- 12 mL/kg/ min, partial liquid ventilation = 41 +/- 11 ml/kg/min, p <.001), Lung biopsy light microscopy demonstrated a marked reduction in alveolar he morrhage, lung fluid accumulation, and inflammatory infiltration in th e total/partial liquid ventilation animals when compared with the gas ventilation animals. Conclusions: In a model of severe ARDS, pulmonary gas exchange is improved during total followed by partial liquid vent ilation. ration, Pulmonary compliance is improved during total, but no t during partial liquid ventilation, Total followed by partial liquid ventilation was associated with a reduction in alveolar hemorrhage, pu lmonary edema, and lung inflammatory infiltration.