Outside perfusion type blood oxygenator

Details Outside perfusion type blood oxygenator Outside perfusion type blood oxygenator

1990-01-23

1992-08-11

Kummert, Lynn M.

Chemical apparatus and process disinfecting, deodorizing, preser

Blood treating device for transfusible blood

Oxygenator

422 48, 128DIG3, 261DIG28, 21032179, 21032188, A61M 114

Patent

active

051375311

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to a blood oxygenator of the outside perfusion type using hollow-fiber membranes and to blood oxygenators having coextensive integral heat exchanging units.


DESCRIPTION OF THE PRIOR ART



Blood Oxygenator

In known blood oxygenators, hollow fibers are used as a means to bring blood into contact with oxygen and provide a means for removal of carbon dioxide from the blood. For simplicity, such gas exchange will be referred to herein with regards to the oxygenation only, it being understood that transfer of oxygen into and carbon dioxide out of the blood is taking place. The fibers are typically made of a homogeneous membrane of gas-permeable material such as silicone or of hollow fibers made of a microporous membrane of hydrophobic polymeric material such as polyolefins.
There are two types of hollow fiber blood oxygenators: the inside perfusion type in which blood is passed through the bores of the hollow fibers while oxygen is passed on the outside of the hollow fibers and the outside perfusion type. Blood oxygenators of the outside perfusion type pass oxygen through the bores of the hollow fibers while blood is flowed past the outside of the hollow fibers.
In blood oxygenators of the inside perfusion type, no channeling of the blood occurs provided the blood is uniformly distributed and fed to the interior of the large number of hollow fibers involved. However, since the blood flowing through the bores of the hollow fibers moves in a virtually perfect laminar flow, the internal diameter of the hollow fibers needs to be reduced to a small diameter in order to increase the oxygenation rate (i.e., the oxygen transfer rate per unit volume of blood per unit area of membrane).
The laminar flow phenomenon of the blood passing through the hollow fibers presents many problems even when very fine hollow fibers are used. The result is that the oxygenation rate of a blood oxygenator of the inside perfusion type is not as beneficial as might be expected. Effectiveness of oxygen transfer is in part determined by the surface area contact of the blood with hollow fiber. Obviously, a much larger surface area contact results when blood is on the outside of the hollow fiber than when the blood is internal to the fiber.
If the oxygen is not distributed uniformly into the blood, the carbon dioxide desorption rate from the blood (i.e., the carbon dioxide transfer rate out of the blood per unit volume of blood per unit area of membrane) will be reduced.
In the common configuration for inside perfusion blood oxygenators, a cylindrical housing is simply packed with a large number of hollow fibers for gas exchange arranged so that the hollow fibers are parallel to the longitudinal axis of the cylindrical housing. Blood oxygenators of this construction have lower than desired gas exchange rate per unit area of the hollow fiber membrane.
In contrast, in blood oxygenators of the outside perfusion type the oxygen can be distributed uniformly through the spaces between adjacent fibers and the blood can be expected to move with better mixing. However, outside perfusion has had the disadvantage of being subject to less than the desired oxygenation of the blood because of regional channeling of the blood as it passes transversely to the outsides of the hollow fibers.
The known outside perfusion type blood oxygenators in which the hollow fibers are in perpendicular orientation to the direction of blood flow produces more mixing of the blood as the blood flows than inside perfusion constructions. This arrangement can bring about an improvement in oxygenation rate, as compared with those inside perfusion types or construction in which the hollow fibers are arranged to have their length parallel to the direction of blood flow. However, if the number of fibers used in such a blood oxygenator is large (as is desirable) and/or the flow rate of blood is increased in order to treat large volumes of blood, problems arise. For example, unacceptable pressure drop of the blood between inlet and outlets

REFERENCES:
patent: 3794468 (1974-02-01), Leonard
patent: 3834544 (1974-09-01), Tyson, Jr. et al.
patent: 4639353 (1987-01-01), Takemura et al.
patent: 4659549 (1987-04-01), Hamada et al.
patent: 4749551 (1988-06-01), Borgione
patent: 4791054 (1988-12-01), Hamada et al.

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