Chemical apparatus and process disinfecting – deodorizing – preser – Blood treating device for transfusible blood – Oxygenator
Patent
1994-09-02
1995-12-12
Warden, Robert J.
Chemical apparatus and process disinfecting, deodorizing, preser
Blood treating device for transfusible blood
Oxygenator
422 47, 4283044, 521 99, 521155, 521905, 128DIG3, 210496, A61M 116, B01D 7154, B32B 518
Patent
active
054747406
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to apparatus for transferring constituents into and out of blood. More particularly, the invention uses a biphasic foam as a blood oxygenator or dialyzer.
BACKGROUND OF THE INVENTION
The field of this invention is blood mass transfer devices, particularly oxygenators, wherein some desirable constituent (e.g., oxygen) is transferred into the blood and/or some undesirable constituent (e.g., carbon dioxide) is transferred out of the blood. Three basic types of oxygenators have developed over time: film oxygenators (e.g., U.S. Pat. No. 3,070,092); bubble oxygenators (e.g., U.S. Pat. Nos. 3,915,650 and 4,428,934); and membrane oxygenators (e.g., U.S. Pat. No. 4,698,207).
Film oxygenators are characterized by exposing a continuous thin film of blood to an oxygen atmosphere. The surface upon which the blood is filmed must be chemically inert and not damage the blood. Additionally, the surface must sustain a very thin film in order to maximize the diffusion of oxygen into the blood. In bubble oxygenators, oxygen is introduced into the blood as bubbles which oxygenate the blood and drive off carbon dioxide. In these oxygenators, the bubbling or foaming mixture must be passed through a "defoamed" to eliminate gas bubbles from the oxygenated blood before it is returned to the patient. In a typical membrane oxygenator, blood is carried in or around hollow membrane fibers. Oxygen passes through the membrane from an oxygen-rich gas stream to the bloodstream, and carbon dioxide passes through the membrane from the blood to the gas stream. The number and size of the hollow membrane fibers are selected to transfer sufficient oxygen to satisfy the metabolic requirements of the patient. Before the blood is returned to the patient from the membrane oxygenator, it is usually passed through a filter to remove any particulate emboli or gas bubbles. The filter is usually in the arterial line outside of the oxygenator itself.
Various types and configurations of foam have been used for specific purposes in bubble and film oxygenators. Blood oxygenators which use foam material to "defoam" the blood-oxygen mixture, i.e., remove bubbles from the blood, are well known as illustrated by the blood oxygenator in U.S. Pat. No. 4,158,693 to Reed et al. Foam material is also used in the Reed et al. bubble oxygenator to provide an enlarged surface area for oxygen-blood contact, and to disperse the blood so it will rise uniformly through the oxygenating chamber. The film oxygenator in U.S. Pat. No. 3,070,092 to Wild et al. uses a porous sponge material as the surface on which the blood is filmed. None of these types of oxygenators contemplates using a foam material as both the blood pathway and the membrane across which oxygenation occurs.
Certain parameters must be considered when designing an oxygenator, whether of the film, bubble, or membrane type. Parameters which must be considered include the overall size and geometry of the oxygenator, blood volume that can be oxygenated, damage to the blood, the rate of gas exchange, and the volume of blood physically held by the oxygenator (known as "priming volume").
The physical size of an oxygenator is determined in large part by the effective exchange surface area, that is, the exchange surface area the blood is exposed to for oxygenation. The total volume of blood that can be oxygenated must be sufficient to satisfy the metabolic requirements of a patient. As discussed in U.S. Pat. No. 4,698,207 to Bringham et al., this can require using 41,000 to 71,000 hollow fibers in a hollow fiber membrane oxygenator. In order to minimize the size of a blood oxygenator, a large exchange surface area must be contained in a small volume. As a result, the exchange surface area may have to assume intricate geometries which is made difficult by the structures of conventional membrane oxygenators. Intricate geometries are also difficult to achieve with conventional film and bubble oxygenators, as illustrated by the grid of plates in the film oxygenator in U
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Trudell Leonard A.
Whittemore Anthony D.
Dawson E. Leigh
Warden Robert J.
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