Development of a membrane for an intravenous carbon dioxide removal catheter

Abstract

Up to 10% of intensive care unit patients develop ARDS, and therefore requireassistance in ventilation. Although initially lifesaving, commonly applied prolongedmechanical ventilation, causes lung injuries (VILI), that contributes to amortality rate of 27% to 45%. The main subject of this thesis is to develop anoptimized hollow fiber membrane, which is minimal-invasively inserted into thevena cava, in order to avoid the disadvantages of mechanical ventilation. Hollow fibers made of Polymethylpentene are used to construct this membrane. Blood releases CO2 through the hollow fiber membrane while owing outside thehollow fibers. Because of their inert character and the extraordinary solubilityof gases, Peruorocarbon liquids (PFCs), were used as CO2 absorbing phase. Different membrane designs with varying membrane areas, length of the fibers,number of membrane segments and diameter of the membrane casing tube, areinvestigated. In addition, different conditions, such as ow ratio and varyingguidance of the blood and the PFC liquid (inside and outside the hollow fibers), are tested. The membrane design was limited by the high pressure drop in theliquid inside the hollow fibers, which is due to the inner diameter of only 0.2 mm.CO2 diffusion rates of 3.75 ml/min, when blood owed outside the fibers, and12.91 ml/min (3.44 times higher), when blood owed inside the fibers were achievedwith a membrane area of 0.019 m2. The project goal of approximately 60 mlCO2 =min was not reached, but it was proven that the PFC liquid has a high potentialas CO2 absorption phase in an intravenous catheter. Using hollow fibers with larger diameter might increase design possibilities and improve performance.