Validation of a model for flow-dependent carbon dioxide exchange in artificial lungs

The exchange rate of CO2 in artificial lungs depends on the sweep gas flow rate. Control of the amount of CO2 removed by an artificial lung requires q uantitative knowledge of the flow dependence. A simple model of the depende nce of CO2 exchange on sweep gas flow rate in artificial lungs has been pre viously presented (1). For a given partial pressure of CO2 in the blood pha se, sweep gas flow rate, and CO2 exchange rate, the model indicates how clo se the CO2 exchange rate is to the maximum level attainable by the artifici al lung. The focus of this study was to validate the model experimentally b y testing 2 commercial artificial lungs in an in vitro test loop. The CO2 e xchange rate for each artificial lung was measured over a range of sweep ga s flow rates. Linear regression was used to fit the data to the model and e stimate the maximum possible CO2 exchange rate and the average water-side P -CO2 ((P) over bar(CO2)(w)). The difference between the measured and regres sed values of (P) over bar(CO2)(w) was used as an indicator of the ability of the model to quantitatively predict the dependence of CO2 exchange on ga s flow rate. This difference was less than 5% for each experiment, indicati ng that the model can be used to guide control of CO2 exchange rates in art ificial lungs.