Oxygenators liquid membrane blood

The development of liquid-membrane extraction has been mainly in the fields of hydrometallurgy and waste-water treatment. There are also potential advantages for their use in biotechnology, such as extraction from fermentation broths, and biomedical engineering, such as blood oxygenation. 

As mentioned earlier, membrane blood oxygenators probably would qualify as the earliest form of membrane contactors. Reference [11] is a good illustration of a hollow fiber device. However, most work on liquid-gas membrane contactor over the years has focused mainly on two categories (1) separation, purification, and treatment of water or aqueous media and (2) absorption of gaseous species from air either for purification or for recovery, which will be discussed separately. Applications in multiple markets and industries have been investigated in each category. 

Blood Agents are compounds that stop the transfer of oxygen from the blood system to the rest of the body by inhibiting the enzyme cytochrome oxidase. The lack of oxygen rapidly affects all body tissues, especially the central nervous system. Some Blood Agents will also cause lung membranes to swell and become filled with liquid (pulmonary edema). 

N. N. Li and W. J. Asher, Blood Oxygenation by Liquid Membrane Parmeation, in Chemical Engineering in Medicine p, 1, American Chemical Society, Washington, DC, 1973. 

Liquids (either solvents or solvents plus surfactants) other than fluorocarbons might be used to form liquid membranes for blood oxygenation. However, the following criteria must be satisfied ... 

The rate of oxygen transfer per unit area of liquid membrane was estimated. The rate of oxygen uptake was measured from the initial slope of the curve for liquid membranes in Figure 2 and the measured 13 gm/100 ml hemoglobin content of the blood. The volume formation... 

To eliminate the possibility of a measurement artifact at low concentrations, the C02 partial pressure of some blood was increased to 100 mm Hg by bubbling C02 through the blood. The transfer of C02 from this blood is shown in Figure 4. Here the C02 partial pressure dropped from 85 mm Hg to 51 mm Hg in 154 min, using oxygen bubbles without liquid membranes (formed directly in the blood), and... 

The apparatus used for this study produced low transport rates for C02, as well as the previously discussed 02, with and without liquid membranes compared with developed oxygenators. The reason for this slow transport is the very large (approximately 0.4 cm) liquid membrane encapsulated bubbles contrasted with the small bubbles of developed oxygenator. A means is needed to produce small fluorocarbon liquid membranes in blood so that the rapid transport achieved in other liquid membrane applications using small diameter liquid membranes can be achieved for transferring gases to and from blood. 

Liquid Membrane Stability. While studies of other investigators have indicated that the blood has good compatibility with the liquid fluorocarbon surface, they also indicate that fluorocarbon droplets should not be introduced to the bloodstream of animals (6, 7, 8). Liquid membrane rupture in the oxygenator apparatus could produce droplets from the fluorocarbon which had formed the liquid membrane. These droplets would be entrained and returned to a test animal with the oxygenated blood. As a preliminary test for liquid membrane rupture and droplet formulation, the oxygen flow into apparatus was momentarily stopped, and blood samples were withdrawn for examination. 

Liquid membrane of fluorocarbons can be formed encapsulating oxygen bubbles in blood. The transfer of oxygen and carbon dioxide through the liquid membrane to and from the blood, respectively, have been shown. Very similar transfer rates with and without liquid membranes indicate that the resistance of the liquid membranes is small. 

The specific rate of oxygen transfer per unit of liquid membrane area seems to be quite reasonable. However, methods to form and utilize effectively much smaller diameter liquid membranes, perhaps similar to those used in other liquid membrane applications, would be required to obtain enough membrane area per unit blood volume for a practical blood oxygenator. The stability of the liquid membranes does not seem to be a major problem however, more definitive liquid membrane stability information would be required before the blood oxygenator application. 

A recent study with biotechnology applications relates to amino acid extraction. Schugerl and co-workers (71 ) used a quaternary ammonium carrier in an emulsion liquid membrane system for enzyme catalyzed preparation of L-amino acids. Frankenfield et al. (72) discuss a wide variety of biomedical ELM applications including enzyme encapsulation, blood oxygenation, and treatment of chronic uremia. 

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