Suitable CO2 Solubility Models for Determination of the CO2 Removal Performance of Oxygenators

Abstract

CO2 removal via membrane oxygenators during lung protective ventilation has become a reliable clinical technique. For further optimization of oxygenators, accurate prediction of the CO2 removal rate is necessary. It can either be determined by measuring the CO2 content in the exhaust gas of the oxygenator (sweep flow-based) or using blood gas analyzer data and a CO2 solubility model (blood-based). In this study, we determined the CO2 removal rate of a prototype oxygenator utilizing both methods in in vitro trials with bovine and in vivo trials with porcine blood. While the sweep flow-based method is reliably accurate, the blood-based method depends on the accuracy of the solubility model. In this work, we quantified performances of four different solubility models by calculating the deviation of the CO2 removal rates determined by both methods. Obtained data suggest that the simplest model (Loeppky) performs better than the more complex ones (May, Siggaard-Anderson, and Zierenberg). The models of May, Siggaard-Anderson, and Zierenberg show a significantly better performance for in vitro bovine blood data than for in vivo porcine blood data. Furthermore, the suitability of the Loeppky model parameters for bovine blood (in vitro) and porcine blood (in vivo) is evaluated.

Water as a Blood Model for Determination of CO2 Removal Performance of Membrane Oxygenators

“…The in vivo and in vitro results displayed in this study represent a secondary analysis of previously published data [ 8 , 16 ]. In vivo tests using pigs as large animal models were conducted to validate a CFD model that allows to predict the CO 2 removal rate of oxygenators [ 16 ].…”

“…In vivo tests using pigs as large animal models were conducted to validate a CFD model that allows to predict the CO 2 removal rate of oxygenators [ 16 ]. In vitro tests with water were conducted to evaluate the accuracy of CO 2 removal prediction via blood gas analyzer measurements [ 8 ]. A comparison of the CO 2 removal rate of water and blood, as presented in this study, was not conducted in the previous publications.…”

“…The schematic structure of the tests can be seen in Figure 4 . Further experimental details can be found in our preceding publications (in vivo [ 16 ] and in vitro tests [ 8 ]).…”

“…Second, outside the red blood cells and in the absence of the catalyst carbonic anhydrase, the reaction from physically dissolved CO 2 to carbonic acid and vice versa is slow, compared to the short residence time of blood in an oxygenator. Consequently, mostly physically dissolved CO 2 is removed at the membrane [ 8 ].…”

Animal blood in translational research: How to adjust animal blood viscosity to the human standard

“…Therefore, we investigated whole blood viscosity of human, pig, sheep, and horse under a variety of different temperature, shear rate and PCV conditions. Pig was chosen as a species with comparable RBC aggregation and elongation to human blood and due to its use in forensic re-enactment studies (Raymond et al, 1996) and in vitro testing (Lukitsch et al, 2021). Based on the properties given in Table 1, we expected that pig blood would show the best comparability with human blood.…”