US3898045A

US3898045A - Blood oxygenator

Info

Publication number: US3898045A
Application number: US295724A
Authority: US
Inventors: Wallace W Bowley
Original assignee: Intech Corp
Current assignee: BWXT Intech Inc
Priority date: 1972-10-06
Filing date: 1972-10-06
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05
Also published as: IL43375A0; IT997864B; SU559624A3; ES419384A1; JPS523236B2; BE805745A; LU68569A1; FR2252117A1; FR2201904B1; JPS4994191A; BR7307770D0; NL7313746A; JPS5148758A; FR2201904A1; DE2350379A1; AU6103373A; ZA737801B; DD114754A5

Abstract

An improved blood oxygenator having an oxygen ejector and diffuser for mixing venous blood with oxygen bubbles, and a lattice chamber of spherical beads for accelerating the oxygenation process as the blood/oxygen foam mixture passes through the chamber. The oxygenator also includes an improved non-contaminating defoaming means and a heat exchanger.

Description

United States Patent 1 1 1111 3,898,045

Bowley Aug. 5, 1975 [54] BLOOD ()XYGENATOR 3,513,845 5/1970 Chesnut et 31...... 23/2585 X 3,547,591 12/1970 Torres 1 23/2585 [75] 9 Bmvley, Stafford 3,578,411 5 1971 Bentley-ct al... 23/2585 Sprmgs, Conn- 3,729,377 4/1973 Leonard 23/2585 X [73] Assigneez Intech Inc. Manchester Conn 3,769,162 10/1973 Brumfleld 23/2585 X 22 i 6, 1972 FOREIGN PATENTS OR APPLICATIONS 1,089,125 9/1960 Germany 23/2585 [211 APPL 295724 302.125 6/1971 U.S.S.R 23 2585 [52] 1.8. CI. 23/258-5; 55/255; 55/256; Primary ExaminerBarry Richman 55/527; /5 128/ I 3; 195/l-8; Attorney, Agent, or FirmWeingarten, Maxham &

261/122; 261/D1G. 26; 26l/D1G. 28 Schurgin [51] Int. Cl. A6lm l/03 [58] Field of Search 23/2585; 261/122, DIG. 26,

261/D1G. 28; 55/255, 256-, 527, 528; [57] ABSTRACT 195/ 1 .8; 128/D1G. 3 An improved blood oxygenator having an oxygen ejector and diffuser for mixing venous blood with oxygen [56] References Cited bubbles, and a lattice chamber of spherical beads for UNITED STATES PATENTS accelerating the oxygenation process as the blood/oxy- 2,934,067 4/1960 Calvin 23/2585 gen mixture pfisses thmugh chamber The 3 175 555 3/1965 Ling 1 23/2585 oxygenam' @1150 Includes an improved 3:204:63l 9/1965 Fields 23/2585 contaminating defoaming means and a heat 3,291,568 12/1966 Sautter 1 23/2585 g 3,468,631 9/1969 Raible et a1 23/2585 3,488,158 1/1970 Bentley 61 al 23/2585 23 Clams, 3 Drawing Flgures BLOOD SHEET BLOOD BLOOD OXYGENATOR FIELD OF THE INVENTION This invention relates to blood oxygenators and more particularly concerns a simple, relatively inexpensive, disposable blood oxygenator and heat exchanger which can be used as a substitute for the lungs of an animal or human being during surgery.

DISCUSSION OF THE PRIOR ART Many devices have been developed for purposes of oxygenating a patients blood during cardiac or related surgery. Both bubble type and' film type oxygenators are known. The older film type devices in which the oxygen must pass through a semi-permeable membrane into the blood are characterized by a very slow rate of oxygenation. The bubble type oxygenators allow for di rect mixing of oxygen bubbles with the oxygen depleted blood. However, using a sufficient oxygen-blood ratio to produce an acceptable oxygen diffusion rate in such a device tends to create turbulence which causes trauma in the blood cells resulting in hemolysis, a physical breakdown of the blood cells themselves. It is evident that for patient safety, hemolysis must be kept to a minimum.

In bubble type oxygenators there is a relationship be tween bubble surface area and film resistance to diffusion which should be optimized in order to maximize the diffusion rate. For a given gas flow rate a small number of large bubbles has too small a mass transfer area for efficient diffusion, whereas a large number of very small bubbles has sufficient interface area but inefficient diffusion characteristics. As might be expected, there exists an optimum size bubble for most efficient diffusion. Certain well known physical proper ties have a bearing upon diffusion rate, an important one being surface film resistance. At the surface of each oxygen bubble there exists a layer of oxygen saturated blood. This is an effective boundary layer which reduces the rate at which the remainder of the oxygen bubble diffuses into the blood thereby reducing the overall oxygenation rate for a given gas flow rate. This boundary layer is more effective for reducing diffusion of small bubbles than of large bubbles. Diffusion rate also relates to the speed at which bubbles rise through the blood. It may thus be appreciated that attempts have been made to produce bubbles of relatively precise size in prior bubble type oxygenators. This gives rise to the present necessity of manufacturing the oxygen bubble diffuser to very close tolerances, a difficult and expensive task at best.

Apparatus has alsobeen devised where the diffusion chamber is filled withspherical bodies in order to provide a sufficient agitation for enhanced oxygenation (Russian Pat. No. 302,125). In that device the blood is made to flow in one direction and the oxygen in the opposite direction through the oxygenator for the stated reason of increasing the rate of diffusion. However, turbulence will likely occur when the oxygen and the blood travel in opposite directions and a significant amount of hemolysis may thereby result. That invention does notprovide a means for preventing hemolysis due to the movement or vibration of the spherical bodies in the chamber as the oxygen and blood move through. nor does it provide for a means to control bubble size. Further, due to the substantial resistance to blood flow caused by the opposite direction oxygen flow it would be necessary to pump the blood through the device, effectively sucking the blood from the patient. The dangers inherent in this practice are obvious. The increased resistance to blood flow tends to further reduce the efficiency and speed of operation of the Russian oxygenator.

In order to prevent injury to the patient, it is necessary that the blood returned to the arteries be entirely free of any gas bubbles. It is therefore necessary that the bubble-type oxygenators have additional provisions for. defoaming the blood after it has been oxygenated because at that point the blood is in the form of a foam. Several previous devices employ a cylinder packed with chips or fibers soaked in a conventional chemical defoaming or non-wetting agent to break down the bubbles. These structures do not have a uniform density defoamer so that defoaming action is different at different locations within the defoamer. Serious danger to the patient has resulted from this type of defoamer fortwo primary reasons. Excess defoaming agent has been known to have entered the blood, thus contaminating it an'dcausing permanent brain damage to patients. Also the defoaming agent in the defoamer eventu ally becomes exhausted and defoaming action de creases with time until it is too slow to be useful. Proposed methods of time-regulated discharge of the-defoaming agent are complicated and are not sufficiently reliable. The difficulties associated with the process of defoaming severly limit the rate of blood flow through many of the presently known oxygenators.

The devices of the prior art tend to have a limited flow rate efficiency. Present applications of these devices in cardiac and related surgery indicatethat an improvement in blood flow rate and oxygenation efficiency as well as reliability in defoaming would beof great benefit to the medical profession and to patients.

SUMMARY OF THE INVENTION Generally speaking, the invention herein disclosed is an improved blood oxygenator for use as a substitute for the lungs of a patient during cardiac and related surgery. It comprises a diffuser from which oxygen bubblesof relatively uniform predetermined size flow into an ejector filled with blood to make a mixture of blood and oxygen. This mixture flows through a chamber filled with spherical hard beads of uniform size forming L a lattice structure. As the oxygen bubbles and the blood move through the bead lattice, oxygen is diffused into the'blood and carbon dioxide is removed therefrom. This reaction is facilitated by frictional contact between the beads and the bubbles in the blood as they pass through the bead lattice. The resulting action may .properly be termed a wiped film bubble oxygenation process. The oxygenated blood foam thus generated leaves the lattice chamber and enters a defoaming section which has radially and axially uniform defoaming properties. Several defoamer embodiments are set forth in the detailed description hereinbelow. The oxygenated defoamed blood flowsover aheat exchanger in order to effect whatever' temperature changes are desired and from there it flows into a calibrated blood reservoir, ready to return to the arterial system of the patient.

The object of this invention is to provide a simple, relatively inexpensive, disposable blood oxygenator having significantly improved blood flow rate and oxygenation efficiency. Additionally, this'oxygenator includes a reliable and constant defoamer which substantially reduces the possibility of dangerous contamination of the blood by chemical antLfoaming agents.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE INVENTION With reference now to the drawing there is shown an oxygenator 11, preferably of cylindrical configuration, which comprises ejector 12, a diffuser 13 within the ejector, a lattice chamber 14 formed of a bed of rigid beads 15 in a cylinder 16, a diverter 17, a defoamer 18, a heat exchanger 21 having a core 22 supported by rings 23 therein, and a graduated reservoir 24.

Ejector 12 is essentially a mixing chamber and bubv.ble pump having side walls 25 which are concave inward. Oxygen is supplied through conduit 26 to the oxygenator from an outside source (not shown), entering gdiffuser 13. Diffuser head 27, shown in detail in FIG.

2, is constructed of a close weave fabric 28 having i -openings of uniform size secured to a retaining ring 29 ;=attached to the top of diffuser 13. The fabric may be Dacron (a registered trademark) or other suitable materiaI-having relatively uniform openings approximately forty microns across. Retaining ring 29 may be any non-corrosive relatively rigid material such as Lucite (a duPont trademark) or stainless steel. Since a relatively inexpensive, disposable yet sturdy structure is contemplated, a rigid plastic retaining ring is preferred. Of course, the oxygenator of this invention is not limited to being disposable and the materials used may vary due to different requirements of the users.

Referring again to FIG. 1, oxygen depleted venous blood enters the ejector through conduits 31. Note that there; are two inputs which enter the bottom of the ejector-at an angle in order to provide a gentle swirling motion. The ejector is normally full of blood and at the beginning of an operation must be primed with blood or a saline solution in the normal manner. Oxygen is released from diffuser head.2'7 forming bubbles of substantially uniform size in the blood. As will be seen later, the preciseness of bubble size is not critical. With the oxygen entering the blood at the location indicated at a relatively high velocity, the ejector with its concave walls 25 acts as a bubble pump. This structure not only moves the blood through the oxygenator, but effectively causes the oxygen bubbles to be mixed throughout the blood at the top of the ejector, as the mixture enters the lattice chamber.

The beads in the lattice chamber are tightly packed and are of uniform size. These beads are preferably 6 mm in diameter but beads ranging from 3 mm to lo mm may be used. The beads may be made of any suitable material which provide a relatively smooth, hard surface. While glass is the substance normally preferred, many other materials such as polyethylene and polytetrafluoroethylene may be used. The function of the lattice chamber will be discussed in detail hereinbelow. A coarse mesh cloth 33 separates the bead bed from the ejector and may be mounted to the bottom of cylinder 16 by a conventional retaining ring or other suitable means. Cloth 33 has a mesh opening sufficiently small so as to prevent any of the beads from escaping from the lattice chamber while permitting free flow of the blood/oxygen mixture from the ejector to the lattice chamber. The top of the lattice chamber is also fitted with a similar coarse mesh cloth 33 to prevent any of the beads from escaping into the defoamer.

It has been found that very little trauma is necessary to cause hemolysis, that is, injury to the blood cells. For this reason, the beads in the chamber are preferably secured together to prevent any vibration or movement within the lattice network. Ultrasonic welding is one good way of accomplishing this desired result Even with the beads secured together, mesh elements 33 are employed at eitherend of the cylinder 16 in case one of the beads should come loose.

When oxygen bubbles are mixed with blood and diffusion begins to take place, a boundary layer of oxygen saturated blood is formed at the surface of each bubble. This boundary layer resists further diffusion of oxygen into the oxygen depleted blood lying beyond the layer. To help counteract this resistance to complete oxygenation, this invention teaches that the bubble is made to traverse a long and tortuous path through the bead lattice. As the bubble encounters each solid bead, there is a wiping action at the diffusion resistant boundary layer of the bubble which physically dislodges or breaks down the boundary layer and results in decreased resistance to the diffusion of oxygen into the blood. The boundary layer reforms as the bubble retreats from each collision with a bead but as each oxygenbubble makes its way upward through the bead lattice, it has a large number of collisions with beads. In the course of each collision, the boundary layer is temporarily broken down and diffusion is facilitated. The rate of diffusion of oxygen in the venous blood isincreased by the presence of thebeads because of the greatly increased surface area for diffusion which the beads provide and by the wiping effect produced by the bubble-bead collisions. It may thus be appreciated that the terminology wiped film bubble oxygenation process is quite appropriate.

According to thisinvention, the flow of oxygen and venous blood is in the same upward direction through the center of the oxygenator, thus eliminating significant resistance to blood flow in opposite directions. In addition, the common directional flow of blood and oxygen bubbles means that blood and oxygen *are in contact tzlfirdughout the tirne thatthe blood is flowing through the lattice chamber, thus increasing the diffusion rate. Also, the co-directional flowof the blood and oxygen avoids the turbulence which would result from the collision of two oppositely directed flows.

According to the invention there a're'uniform size passageways between the beads 15 inthe lattice chamber 14 because the beads themselves are uniform in size. These constricted passageways regulate to a very closetolerance the size of the oxygen bubbles which can pass through the bead lattice. It is well known in the art that in bubble type oxygenators there is a balance between bubble area and film resistance which is difficult to achieve as has previously been stated. It is necessary to maintain a balance in bubble size in order 5. to maximize diffusion and this must be done accurately. In conventional bubble type oxygenators, th'is i's"at'- tempted by means of a diffuser with openings manufactured to very close tolerances. In the presentinvention, the uniform spacingsbetween the beads can be designed to permit only bubbles of the desired size to proceed through the bead lattice thereby providing maximim diffusion efficiency. Larger bubbles will be separated as they 'pass through the restricted passageways between the beads, thereby accomplishing the desired effect. Consequently, fabric 28 on diffuser'head 27 need not'be manufactured to extremely close tolerances since the bead bed will reduce bubble size as'the mixture passes'through it.

It is not apparent that several factors of the present invention contribute to increased diffusion speed and efficiency; Among these factors are the cumulatively large surface area of the heads, the wiping action produced by contact between the pliable bubbles and the hard beads, the'long mutual contact time resulting from co-directional flow of blood and oxygen and the long path of travel which results from the presence'of the closely packed beads. Such factors enable the oxygenator of the present'invention to be operated at a'lower oxygen/blood flow ratio than is possible in conventional oxygenato'rs. [t is well known in the art that when the oxygen/blood flow ratio is decreased, the turbulence which occurs in the blood-oxygen mixture also decreases. When turbulence decreases, hemolysis is significantly reduced. Thus animportant effect of the present invention is greatly reduced hemolysis, while maintaining an overall high diffusion efficiency.

The oxygenated blood foam contacts diverter 17 directly from the top of lattice chamber 14. The diverter consists of a concave conical surface preferably made of clear plastic although other shapes and materials may be used. The foam is directed'outward by the diverter and enters defoamer 18 which surrounds the top portion of the lattice chamber above the heat exchanger. Note that the defoamer fabric extends to the center of the oxygenator between the top of the lattice chamber and the diverter.

With reference not to FIG. 3, a top view of defoamer 18 is shown. It consists of a woven cloth 34 which is wound around the upper portion of the lattice chamber a predetermined number of turns in order to insure radial uniformity and consistency in production. Defoaming may be achieved in the well-known manner wherein bubbles containing carbon dioxide and oxygen collapse on fibers which have been coated by spraying or dipping with a chemical antifoam or nonwetting agent. A preferred embodiment of the defoamer is to wrap the lattice chamber with a material comprising two alternating layers of fabric, one wetting and one nonwetting. In this embodiment the bubbles are pulled apart by being repelled from the non-wetting material and attracted to the wetting material whereon it col lapses and drains to the reservoir 24. An alternative preferred embodiment of the defoamer is to use a cloth woven of wetting fibers running horizontally and nonwetting fibers running vertically. The bubbles are repelled and attracted as stated above, causing the bubbles to collapse in a single vertical plane drain to the reservoir. These two preferred embodiments utilize fibers whose wetting and non-wetting properties are inherent in the materials themselves ratherthan the result of treatment with chemical agents. Examples of nonwetting materials are nylon and polytetrafluoroethylene, while wetting materials may be glass fiber or fibersfrom the polycarbonate family such as Lexan (a registered trademark). These embodiments have the advantage of stability, that is the non-wetting and wetting properties of the fibers are constant in time. Further, there is no likelihood of dangerous contamination of the patients blood with anti-foam agent. The cloth of the defoamer is wound relatively tightly around the lattice chamber so thateach successive turn contacts the adjacent turns and there'is radial uniformity from the lattice chamber outw'ardto the wall of the oxygenator. The 'defoamerfillsall of the space between cylinder 16 and the walls of the oxygenator which lies between the heat exchanger and the diverter.

Carbon dioxide and excess oxygen released from the blood as it is defoamed is' exhausted from the oxygenator through vent 35 in the top of the defoamer. The vent may be equipped with a'conventional bacteriological filter (not shown) to prevent possible contamination ofthe atmosphere in the operating room..

The oxygenated blood drains from the defoamer and is allowed to flow over the heat exchanger 21. The heat exchanger is an annular cylindrical containerwith an annular core 22 of closedcell foam filling the bulk of the interior thereof. The core is held in place by means of rings 23 at the top and bottom of the'container. Heated or cooled water is pumpedthrough the heat exchanger, entering through conduit 36 and leaving through'conduit 37. The bloodis th'e'reby maintained at a predetermined desired temperature. Fluid other than water could be used if desired; This particular configuration for the heat e'xchangerpermits a large surface area for rapid temperature adjustment ofthe blood flowing over its sides while having a reduced interior volume to permit rapid fluid exchange within it. t

The oxygenated blood of desired temperature is stored in a reservoir' 24 which preferably has transparent walls. The reservoir is an annular configuration and surrounds the ejector and diffuser and the lower end of the lattice chamber. The reservoir'is calibratedtscale 38) as to volume in order that theamount of blood available can easily be'monitored 'duringthe operation. The oxygenated blood is removed from the reservoir through tubing 40 controlled by conventional ball-type check valve 39 which closes the outlet when insufficient blood is present in the reservoir. This prevents any air from getting into the patients arterial system in an emergency situation when the blood reservoir becomes empty. Note that the heat exchanger resides within the reservoir in order to 'rnaintain the'blood temperature as desired.

A ring 41 is secured to the top of the oxygenator to provide for attachment of the unit to a ring stand holder. Preferably the main shell and most of the interior parts of this oxygenator are made of substantially rigid transparent plastic so that its proper operation may be observed at all times. The plastic elements may be secured together by adhesive or by other suitable means. By being made'of plastic it is disposable, inex pensive to make and shatter resistant. The overall size of this oxygenator is approximately 18 inches in height and 7 inches in diameter for adults/Because thevolume necessary for babies is much lessfa reduced size oxygenator is available for pediatric purposes. Of course, the size specified above is by way of example only and is in no way limiting.

The invention herein disclosed is a very compact. vertically hung oxygenator. Installation time and operator training are minimal since the device is presterilized and disposable, while being very simple to set up and operate. Those skilled in the art will readily appreciate that various modifications and improvements to this oxygenator may be made to suit particular requirements which are within the scope of the invention.

What is claimed is:

l. A blood oxygenator comprising:

a housing;

means within said housing for mixing blood and oxygen together to form a foam and for pumping the foam through said oxygenator, said mixing and pumping means having at least one blood inlet port at one end and a blood foam outlet at the opposite end;

oxygen diffusing means within said mixing and pumping means, said oxygen diffusing means having an oxygen inlet port and having an oxygen outlet spaced from either end of said mixing and pumping means, said oxygen diffusing means further comprising: means at said oxygen outlet for discharging oxygen into the blood in said mixing and pumping means in the form of bubbles;

an elongated chamber within said housing, the walls of said chamber being laterally spaced from the interior surfaces of said housing;

a lattice bed comprising a multiplicity of hard beads of substantially uniform size being tightly packed within and substantially filling said chamber to thereby provide a relatively large collision surface area within said chamber and a plurality of tortuous paths therethrough, each of which is substantially longer than said chamber, said chamber having an outlet and having an inlet coupled to said blood foam outlet of said mixing and pumping means;

means for maintaining said lattice bed in tightly packed configuration within said chamber;

defoaming means within said housing adjacent said outlet of said chamber, said blood foam being separated into gases and fluid blood within said defoaming means;

fluid blood storage means below and in communication with said defoaming means; and

fluid blood outlet means mounted in the bottom of said storage means.

2. The oxygenator recited in claim 1 and further comprising means located at the outlet of said chamber for diverting the oxygenated blood foam away from the top of said chamber and to said defoaming means.

3. The oxygenator recited in claim 1 and further comprising an exhaust port for exhausting carbon dioxide and excess oxygen from said oxygenator.

4. The oxygenator recited in claim 1 wherein said blood inlet port enters said mixing and pumping means at an angle relative to the axis of said elongated chamber to provide gentle swirling action to the blood.

5. The oxygenator recited in claim 1 wherein said means for maintaining said lattice bed in tightly packed configuration comprises a substantially rigid coarse mesh cloth'at each end of said chamber confining said beads therein.

6. The oxygenator recited in claim 1 wherein said means for maintaining said lattice bed in tightly packed configuration comprises means forming a rigid bond between adjacent contacting beads within said chamher.

7. The oxygenator recited in claim 1 wherein said means for discharging oxygen into the blood in the form of bubbles comprises a fabric covering said oxygen outlet of said oxygen diffusing means, said fabric having a multiplicity of openings therethrough of substantially uniform size.

8. The oxygenator recited in claim 1 and further comprising safety valve means in said fluid blood outlet means operative to remain open only when there is fluid in said fluid blood storage means.

9. The oxygenator recited in claim 1 and further comprising means within said housing to adjust the blood temperature for reentry into a patient, said temperature adjusting means having an inlet and an outlet for temperature adjusting fluid to pass therethrough.

10. The oxygenator recited in claim 9 wherein said means for adjusting blood temperature is an annular cylindrical container surrounding said mixing and pumping means and wherein said fluid blood storage means is an annular cylindrical chamber surrounding said mixing and pumping means, said temperature adjusting means container being located within said fluid blood storage means chamber.

11. The oxygenator recited in claim 1 wherein said defoaming means comprises:

multiple layers of cloth wherein each such layer is in confronting relationship and touches the next adjacent layer, said cloth being formed of a multiplicity of fibers, a first portion of said fibers having nonwetting characteristics relative to blood, and a second portion of said fibers having a lesser degree of non-wetting characteristics relative to blood than said first portion of said fibers.

12. The oxygenator recited in claim 11 wherein:

said mixing and pumping means is elongated and has a longitudinal mid-point cross section which is substantially less than the cross section thereof at said outlet end; and

said oxygen outlet of said oxygen diffusing means is located substantially at said longitudinal mid-point of said mixing and pumping means.

13. A blood oxygenator comprising:

a housing;

oxygen diffusing means within said mixing and pumping means, said oxygen diffusing means having an oxygen inlet port and having an oxygen outlet spaced from either end of said mixing and pumping means, said oxygen diffusing means further comprising:

means at said oxygen outlet for discharging oxygen into the blood in said mixing and pumping means in the form of bubbles;

a lattice bed comprising a multiplicity of hard beads of substantially uniform size being tightly packed within and substantially filling said chamber to thereby provide a relatively large collision surface area within said chamber and a plurality of tortuous paths therethrough, said chamber having an outlet and having an inlet coupled to said blood foam outlet of said mixing and pumping means; means for maintaining said lattice bed in tightly packed configuration within said chamber; defoaming means within said housing adjacent said outlet of said chamber, said blood foam being separated into gases and fluid blood within said defoaming means, said defoaming means comprising: multiple layers of cloth wherein each such layer is in confronting relationship and touches the next adjacent layer, said cloth being formed of a multiplicity of fibers, a first portion of said fibers having non-wetting characteristics relative to blood, and a second portion of said fibers having a lesser degree of nonwetting characteristics relative to blood than said first portion of said fibers; fluid blood storage means below and in communication with said defoaming means; and fluid blood outlet means mounted in the bottom of said storage means,

14. The oxygenator recited in claim 13 wherein said first portion of said fibers having non-wetting characteristics comprises first layers of said multiple layers of cloth, and said second portion of said fibers having a lesser degree of non-wetting characteristics comprises second layers of said multiple layers of cloth, one of said first layers of cloth being located between two adjacent confronting second layers of cloth in alternating fashion throughout said defoaming means.

15. The oxygenator recited in claim 13 wherein said multiple layers of cloth fully occupy the space between the walls of said chamber and the interior surfaces of said housing adjacent to the outlet end of said chamber.

16. The oxygenator recited in claim 13 wherein said non-wetting characteristics are provided in said first portion of said fibers by means of a coating of nonwetting material.

17. The oxygenator recited in claim 13 wherein each of said layers of cloth is woven wherein said first portion of said fibers having non-wetting characteristics are oriented in one direction and said second portion of said fibers having a lesser degree of non-wetting characteristics are cross woven with said first portion of said fibers.

18. The oxygenator recited in claim 17 wherein said first portion of said fibers having non-wetting characteristics are arranged to lie along an axis substantially parallel to the axis of said elongated chamber to permit efficient draining of the liquid from said blood foam by force of gravity.

19. The oxygenator recited in claim 13 wherein the non-wetting characteristics of said first portion of said fibers is inherent in said fibers, and the lesser degree of non-wetting characteristics of said second portion of said fibers is inherent in said fibers.

20. The oxygenator recited in claim 19 wherein:

said first portion of said fibers having non-wetting characteristics relative to blood is a member of the group consisting of glass and polycarbonates; and said second portion of said fibers having a lesser degree of non-wetting characteristics relative to blood is a member of the group consisting of nylon and polytetrafluoroethylene.

21. A blood oxygenator comprising:

a housing;

means within said housing for mixing blood and oxygen together to form a foam and for pumping the foam through said oxygenator, said mixing and pumping means having at least one blood inlet port at one end and a blood foam outlet at the opposite end, said mixing and pumping means being elongated and having a midpoint cross section which is substantially less than the cross section thereof at said outlet end;

oxygen diffusing means within said mixing and pumping means, said oxygen diffusing means having an oxygen inlet port and having an oxygen outlet spaced from either end of said mixing and pumping means and located substantially at said mid-point thereof, said oxygen diffusing means further comprising: means at said oxygen outlet for discharging oxygen into the blood in said mixing and pumping means in the form of bubbles, the velocity of the oxygen being converted to a foam pressure at said outlet of said mixing and pumping means due to the expanding cross section thereof from the point of entry of the oxygen bubbles to said outlet;

a lattice bed comprising a multiplicity of hard beads of substantially uniform size being tightly packed within and substantially filling said chamber to 7 thereby provide a relatively large collision surface area within said chamber and a plurality of tortuous paths therethrough, said lattice chamber having an outlet and having an inlet coupled to said blood foam outlet of said mixing and pumping means;

defoaming means within said housing adjacent said outlet of said lattice chamber, said blood foam being separated into gases and fluid blood within said defoaming means;

fluid blood storage means within said housing and located below said defoaming means; and

fluid blood outlet means mounted in the bottom of said storage means.

22. The oxygenator recited in claim 21 wherein the blood foam outlet of said mixing and pumping means has substantially the same cross section as said inlet of said elongated lattice chamber.

23. The oxygenator recited in claim 22 wherein said oxygen outlet of said oxygen diffusing means is substantially smaller in cross sectional area than the cross section of said mixing and pumping means lying in the same plane as said oxygen outlet, whereby the mass flow of oxygen from said oxygen outlet is less than blood through said mixing and pumping means at the same plane as said oxygen outlet.

Claims

1. A BLOOD OXYGENATOR COMPRISING: A HOUSING MEANS WITHIN SAID HOUSING FOR MIXING BLOOD AND OXYGEN TOGETHER TO FORM A FOAM AND FOR PUMPING THE FOAM THROUGH SAID OXYGENATOR, SAID MIXING AND PUMPING MEANS HAVING AT LEAST ONE BLOOD INLET PORT AT ONE END AND A BLOOD FOAM OUTLET AT THE OPPOSITE END, OXYGEN DIFFUSING MEANS WITHIN SAID MIXING AND PUMPING MEANS, SAID OXYGEN DIFFUSING MEANS HAVING AN OXYGEN INLET PORT AND HAVING AN OXYGEN OUTLET SPACED FROM EITHER END OF SAID MIXING AND PUMPING MEANS, SAID OXYGEN DIFFUSING MEANS FURTHER COMPRISING: MEANS AT SAID OXYGEN OUTLET FOR DISCHARGING OXYGEN INTO THE BLOOD IN SAID MIXING AND PUMPING MEANS IN THE FORM OF BUBBLES, AN ELONGATED CHAMBER WITHIN SAID HOUSING, THE WALLS OF SAID CHAMBER BEING LATERALLY SPACED FROM THE INTERIOR SURFACES OF SAID HOUSING, A. LATTICE BED COMPRISING A MULTIPLICITY OF HARD BEADS OF SUBSTANTIALLY UNIFORM SIZE BEING TIGHTLY PACKED WITHIN AND SUBATANTIALLY FILLING SAID CHAMBER TO THEREBY PROVIDE A RELATIVELY LARGE COLLISION SURFACE AREA WITHIN SAID CHAMBER AND A PLURALITY OF TORTUOUS PATHS THERETHROUGH, EACH OF WHICH IS SUBSTANTIALLY LONGER THAN SAID CHAMBER, SAID CHAMBER HAVING AN OUTLET AND HAVING AN INLET COUPLED TO SAID BLOOD FOAM OUTLET OF SAID MIXING AND PUMPING MEANS, MEANS FOR MAINTAINING SAID LATTICE BED IN TIGHTLY PACKED CONFIGURATION WITHIN SAID CHAMBER, DEFOAMING MEANS WITHIN SAID HOUSING ADJACENT SAID OUTLET OF SAID CHAMBER, SAID BLOOD FOAM BEING SEPARATED INTO GASES SAID FLUID BLOOD WITHIN SAID DEFOAMING MEANS, FLUID BLOOD STORAGE MEANS BELOW AND IN COMMUNICATION WITH SAID DEFOAMING MEANS, AND FLUID BLOOD OUTLET MEANS MOUNTED IN THE BOTTOM OF SAID STORAGE MEANS,

5. The oxygenator recited in claim 1 wherein said means for maintaining said lattice bed in tightly packed configuration comprises a substantially rigid coarse mesh cloth at each end of said chamber confining said beads therein.

6. The oxygenator recited in claim 1 wherein said means for maintaining said lattice bed in tightly packed configuration comprises means forming a rigid bond between adjacent contacting beads within said chamber.

11. The oxygenator recited in claim 1 wherein said defoaming means comprises: multiple layers of cloth wherein each such layer is in confronting relationship and touches the next adjacent layer, said cloth being formed of a multiplicity of fibers, a first portion of said fibers having non-wetting characteristics relative to blood, and a second portion of said fibers having a lesser degree of non-wetting characteristics relative to blood than said first portion of said fibers.

12. The oxygenator recited in claim 11 wherein: said mixing and pumping means is elongated and has a longitudinal mid-point cross section which is substantially less than the cross section thereof at said outlet end; and said oxygen outlet of said oxygen diffusing means is located substantially at said longitudinal mid-point of said mixing and pumping means.

13. A blood oxygenator comprising: a housing; means within said housing for mixing blood and oxygen together to form a foam and for pumping the foam through said oxygenator, said mixing and pumping means having at least one blood inlet port at one end and a blood foam outlet at the opposite end; oxygen diffusing means within said mixing and pumping means, said oxygen diffusing means having an oxygen inlet port and having an oxygen outlet spaced from either end of said mixing and pumping means, said oxygen diffusing means further comprising: means at said oxygen outlet for discharging oxygen into the blood in saId mixing and pumping means in the form of bubbles; an elongated chamber within said housing, the walls of said chamber being laterally spaced from the interior surfaces of said housing; a lattice bed comprising a multiplicity of hard beads of substantially uniform size being tightly packed within and substantially filling said chamber to thereby provide a relatively large collision surface area within said chamber and a plurality of tortuous paths therethrough, said chamber having an outlet and having an inlet coupled to said blood foam outlet of said mixing and pumping means; means for maintaining said lattice bed in tightly packed configuration within said chamber; defoaming means within said housing adjacent said outlet of said chamber, said blood foam being separated into gases and fluid blood within said defoaming means, said defoaming means comprising: multiple layers of cloth wherein each such layer is in confronting relationship and touches the next adjacent layer, said cloth being formed of a multiplicity of fibers, a first portion of said fibers having non-wetting characteristics relative to blood, and a second portion of said fibers having a lesser degree of non-wetting characteristics relative to blood than said first portion of said fibers; fluid blood storage means below and in communication with said defoaming means; and fluid blood outlet means mounted in the bottom of said storage means.

16. The oxygenator recited in claim 13 wherein said non-wetting characteristics are provided in said first portion of said fibers by means of a coating of non-wetting material.

20. The oxygenator recited in claim 19 wherein: said first portion of said fibers having non-wetting characteristics relative to blood is a member of the group consisting of glass and polycarbonates; and said second portion of said fibers having a lesser degree of non-wetting characteristics relative to blood is a member of the group consisting of nylon and polytetrafluoroethylene.

21. A blood oxygenator comprising: a housing; means within said housing for mixing blood and oxygen together to form a foam and for pumping the foam through said oxygenator, said mixing and pumping means having at least one blood inlet port at one end and a blood foam outlet at the opposite end, said mixing and pumping means being elongated and having a Midpoint cross section which is substantially less than the cross section thereof at said outlet end; oxygen diffusing means within said mixing and pumping means, said oxygen diffusing means having an oxygen inlet port and having an oxygen outlet spaced from either end of said mixing and pumping means and located substantially at said mid-point thereof, said oxygen diffusing means further comprising: means at said oxygen outlet for discharging oxygen into the blood in said mixing and pumping means in the form of bubbles, the velocity of the oxygen being converted to a foam pressure at said outlet of said mixing and pumping means due to the expanding cross section thereof from the point of entry of the oxygen bubbles to said outlet; an elongated chamber within said housing, the walls of said chamber being laterally spaced from the interior surfaces of said housing; a lattice bed comprising a multiplicity of hard beads of substantially uniform size being tightly packed within and substantially filling said chamber to thereby provide a relatively large collision surface area within said chamber and a plurality of tortuous paths therethrough, said lattice chamber having an outlet and having an inlet coupled to said blood foam outlet of said mixing and pumping means; means for maintaining said lattice bed in tightly packed configuration within said chamber; defoaming means within said housing adjacent said outlet of said lattice chamber, said blood foam being separated into gases and fluid blood within said defoaming means; fluid blood storage means within said housing and located below said defoaming means; and fluid blood outlet means mounted in the bottom of said storage means.