ARTERIOVENOUS EXTRACORPOREAL CARBON-DIOXIDE REMOVAL - A MATHEMATICAL-MODEL AND EXPERIMENTAL EVALUATION

To explore the feasibility and operating limits of arteriovenous extra corporeal CO2 removal (AVCO(2)R) for support of acute respiratory fail ure, the authors developed a mathematical model to simulate (AVCO(2)R) , evaluate the effects of several parameters used in its application, and predict the feasibility and necessary conditions for total CO2 rem oval. The mathematical model incorporated compartments representing bl ood, pulmonary alveoli, pulmonary capillaries, peripheral tissues and capillaries, and an extracorporeal gas exchange device. The model was validated against an animal model of extracorporeal CO2 removal. This model consisted of anesthetized and mechanically ventilated piglets. A n extracorporeal CO2 removal device was placed by cannulation of a fem oral artery and vein. Dynamic and steady state measurements of CO2 tra nsfer were made and compared with simulations using the mathematical m odel. There was good agreement between experimental and simulated data , validating the mathematical model under a variety of conditions. The mathematical model was used to determine operating parameters for tot al CO2 removal. Relationships between extracorporeal blood flow, devic e diffusing capacity, and device gas sweep flow were established for C O2 removal at various levels of CO2 production. These simulations indi cate that it is possible to achieve total CO2 removal using an extraco rporeal shunt fraction of 10%-15% of cardiac output, a device diffusin g capacity of 0.5 mi min(-1) torr(-1) (kg body weight)(-1), and a gas: blood flow of 5 or greater.