Evaluation of Two Microporous Polypropylene Membrane Lungs for Extracorporeal Carbon Dioxide Removal during Apneic Oxygenation

Abstract

Five Capiox II 33 (Terumo Corporation) and nine M-2000 (Shiley Incorporated) microporous polypropylene membrane lungs were evaluated for dynamic operating characteristics during apneic oxygenation. Particular emphasis was placed on carbon dioxide and oxygen transfer (VCO2 and VO2 respectively). The lungs were incorporated into extracorporeal venovenous bypass circuits used with the pigs of 36.5 kg average weight. VCO2 was determined by analyzing outlet gas composition and VO2 was determined with the Fick technique. Blood flow rate was held constant at 1 L/min in all trials. Peak VCO2 occurred at gas flow rates of 4 L/min and 6 L/min for the Capiox II 33 and M-2000 respectively. Both lungs eliminated CO2 in quantities sufficient for complete ventilatory support during apneic oxygenation over the 5-8 hour experiments. VO2 for the Capiox II 33 was 18.2 and 45.6 ml/min with an inlet oxygen saturation of 70% and FiO2 of 0.209 and 1.0 respectively. Under the same conditions, the VO2 for the M-2000 was 27.2 and 43.1 ml/min. Both lungs operated with low gas inlet pressures over the gas flow rates used and the blood path pressure drop averaged 42.2 and 20.7 mmHg for the Capiox II 33 and M-2000 respectively.