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

Benjamin Lukitsch,Christoph Janeczek,Christian Jordan,Markus Pekovits,Martin Elenkov,Bahram Haddadi,Margit Gfoehler,Raffael Koller,Paul Ecker,Michael Harasek

doi:10.3390/membranes11050356

Abstract

CO2 removal via membrane oxygenators has become an important and reliable clinical technique. Nevertheless, oxygenators must be further optimized to increase CO2 removal performance and to reduce severe side effects. Here, in vitro tests with water can significantly reduce costs and effort during development. However, they must be able to reasonably represent the CO2 removal performance observed with blood. In this study, the deviation between the CO2 removal rate determined in vivo with porcine blood from that determined in vitro with water is quantified. The magnitude of this deviation (approx. 10%) is consistent with results reported in the literature. To better understand the remaining difference in CO2 removal rate and in order to assess the application limits of in vitro water tests, CFD simulations were conducted. They allow to quantify and investigate the influences of the differing fluid properties of blood and water on the CO2 removal rate. The CFD results indicate that the main CO2 transport resistance, the diffusional boundary layer, behaves generally differently in blood and water. Hence, studies of the CO2 boundary layer should be preferably conducted with blood. In contrast, water tests can be considered suitable for reliable determination of the total CO2 removal performance of oxygenators.

Highlights

Blood oxygenators, known as artificial lungs, are needed to supplement respiratory function during cardiopulmonary bypass or to support patients with respiratory failure
The CO2 removal rate of the prototype oxygenator determined in vivo with porcine blood and in vitro with water is compared
The CO2 removal determined with porcine blood is generally higher than the CO2 removal of water

Summary

Introduction

Known as artificial lungs, are needed to supplement respiratory function during cardiopulmonary bypass or to support patients with respiratory failure. To provide a large gas-exchange surface at the lowest possible priming volume, hollow fiber membrane packings are used [1]. Great efforts have been made to improve the biocompatibility of oxygenator circuits [3], serious side effects occur due to contact of blood with the artificial polymer surfaces. These side effects include reduced platelet function and survival as well as prolonged bleeding times after perfusion [4]. The optimization of oxygenators aims for increasing gas exchange efficiency while reducing the membrane surface and blood priming volume [5]

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