OXYGEN-CONSUMPTION AND CARBON-DIOXIDE PRODUCTION DURING LIQUID VENTILATION

Liquid ventilation with perfluorocarbon (PFCV) has advantages over conventional gas ventilation (GV) in premature and lung-injured newborn animals. Indirect calorimetric measurement of both oxygen consumption (V̇O2) and carbon dioxide production (V̇CO2) during PFCV has not been previously performed. In addition, comparison to indirect calorimetric measurement of V̇O2 and V̇CO2 during GV has not been evaluated. Ten fasted normal cats weighing 2.6 to 3.9 kg were anesthetized with pentobarbital and pancuronium. Tracheostomy was performed. Gas exchange was measured across the native lung during GV and across the membrane lung of the liquid ventilator during PFCV. V̇O2 was measured using a modification of a previously described, indirect, closed-circuit, volumetric technique. V̇CO2 was analyzed by capnographic assay of the mixed-expired closed-circuit air. The V̇CO2/V̇O2 ratio (RQ) was calculated. There was no change in V̇O2, V̇CO2, or RQ during PFCV when compared with GV (V̇O2: GV = 5.7 ± 0.3 mL/kg/min, PFCV = 5.6 ± 0.5 mL/kg/min [P = NS]; V̇CO2 : GV = 4.9 ± 1.1 mL/kg/min, PFCV = 4.8 ± 0.9 mL/kg/min [P = NS]; RQ: GV = 0.85 ± 0.21, PFCV = 0.86 ± 0.21 [P = NS]). During GV the PaO2 was higher than during PFCV (PaO2: GV = 335 ± 70 mm Hg, PFCV = 267 ± 83 mm Hg [P = .04]), as is expected because of the relative reduction in the inspiratory PiO2 of the perfluorocarbon during liquid ventilation. There was no significant change in the PaCO2 (PaCO2: GV = 37.3 ± 2.2 mm Hg, PFCV = 40.4 ± 5.3 mm Hg [P = NS] or the pH (pH: GV = 7.34 ± 0.04, PFCV = 7.35 ± 0.06 [P = NS]). This study demonstrates the efficacy of measuring V̇O2 and V̇CO2 during gas and liquid ventilation using an indirect calorimetric technique. The data demonstrate that V̇O2 and V̇CO2 do not change during liquid ventilation and that excellent gas exchange can be accomplished through PFCV. © 1993.