US2981253A - Oxygenator - Google Patents

Description

April 25, 1961 DE WALL 2,981,253

OXYGENATOR Filed July 17, 1957 INVENTORS RICHARD/4. DEMLL BY (2 nRs/vcsmz ro/vl/ums/ 147- TORNE Y5 OXYGENATOR Richard A. De Wall, Minneapolis, and Clarence Walton Lillehei, St. Paul, Minn., assignors to The Regents of the University of Minnesota, Minneapoiis, Minn, a corporation of lilinnesota Filed July 17, 1957, Ser. No. 672,438 11 Claims. (Cl. 128214) This invention relates to an oxygenating system for use in an extra corporeal circulation device for temporarily assuming or assisting the functions of the heart and lungs in a human being or other animal. More particularly this invention relates to a simple disposable device for filming blood for oxygenation and release of carbon dioxide outside of the body of a human or other animal during cardiac surgery. The oxygenating device of this invention, which temporarily assumes the functions of the lungs, is used with a standard blood pump which temporarily assumes the function of the heart by circulating the blood through the oxygenator.

The desirability and necessity of temporarily relieving the heart of its normal function of pumping blood during cardiac surgery have long been recognized and the con cept of extracorporeal circulation is generally old in the art. In our Patent No. 2,854,002, issued September 30, 1958, from copending application Serial No. 656,175, filed April 22, 1957, which in turn is a continuation of our application Serial No. 598,284, filed July 18, 1956, now Patent 2,898,568, there is described and claimed a simple inexpensive disposable artificial oxygenator and the method of oxygenating blood by the use of that device. According to the method of our earlier application oxygen is introduced into venous blood from a patient by directly dispersing bubbles of oxygen in a column of blood, the mixed blood and oxygen is discharged into a debubbling chamber provided with a coating of anti-foam agent to dissipate the gas bubbles in the blood, and the oxygenated blood is permitted to flow downwardly by gravity in a slow laminar flow whereby heavier gas-free blood is permitted to flow beneath and continuously displace upwardly gas-containing blood of lesser density to insure liberation of entrained gas bubbles before return of the oxygenated blood to the patient.

The oxygenator, according to the present invention, utilizes the same pumping apparatus and receives and returns the blood in substantially the same manner described in our previous applications. Oxygenation, according to the present invention, is accomplished however by a filming technique; that is, by maintaining a continuous film of flowing blood and exposing that film to an atmosphere of pure oxygen.

It is the principal object of this invention to provide a simple, economical, disposable, film oxygenating and carbon dioxide releasing device for use in direct vision intracardiac surgery.

Other objects of the invention will become apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, this invention t-hen comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a fewof the various ways in which the principles of the invention may be employed.

- The invention is illustrated by the drawings in which 2,981,253 Patented Apr. 25, 1961 the same numerals refer to corresponding parts and in which:

Figure l is an elevation of the film oxygenator according to this invention shown with the front surface partly broken away to reveal the inner construction;

Figure 2 is a transverse, horizontal section taken on the line 2-2 of Figure 1 and in the direction of the arrows, showing in greater detail the construction of this disposable film oxygenator; and

Figure 3 is a transverse, vertical section taken on the line 33 of Figure 1 and in the direction of the arrows, to illustrate in detail the construction of the oxygenator.

Referring to the drawings, the oxygenator of this invention includes a generally rectangular plastic film envelope indicated generally at 10, having a front face film panel 11 and a back face film panel 12. The top of the oxygenator is provided with hanging means in the form of an elongated loop 13 of plastic film extending across the top of the oxygenator and adapted to receive the rod 14 of any suitable supporting and tensioning rack. Similarly, the bottom of the oxygenator envelope 18 is provided with an elongated loop member 15 adapted to receive the rod 16 of the supporting rack. The opposite side edges of the oxygenator are provided with loop members 17 and 19 respectively, adapted to receive rods 18 and 20 respectively. The interior of the plastic envelope 10 includes a pair of foraminous filming elements here shown as fine mesh screen members 21 and 22 disposed between the front and back face film panels of the plastic envelope.

The screens 21 and 22 are held spaced apart in order to provide a thin channel 23 for the how of blood through the oxygenator. According to the illustrated form of construction, the opposed marginal edge portions of the side loop member 17 are sealed to a spacer 24 of appropriate thickness such that the total thickness corresponds to the desired-spacing between the screens. Similarly, the op posed marginal edge portions of the loop member 19 are sealed to a spacer 25 and the opposed marginal edge portions of loop member 13 are sealed to a spacer 26. The marginal edges of screen members 21 and 22 are stitched or heat sealed or otherwise secured to the opposite sides of the composite spacers thus produced. The composite spacer along one side edge of the pair of oxygenator screens is made somewhat wider and is provided with a plurality of openings 27 adjacent to the edge of the pair of screens for passage of gas from one side of the envelope to the other for a purpose hereafter explained.

A manifold tube 28 is disposed between the screen members 21 and 22 at the top of the oxygenator. The manifold 28 is in the form of a plastic tube provided with a stopper 29 closing one end and a stopper 30 fitted with a blood inlet tube 31 at the other end. The manifold 28 is provided with a plurality of small openings 32 along its bottom surface for flow of blood between the screens and a few vent openings 33 along its topsurface. Optionally, the manifold is also provided with a fine mesh filter 34- in the form of a V-shaped trough below the bottom of the manifold tube.

Because the thickness of the manifold 28 tends to separate the screen members 21 and 22 spacer elements 35 and 36 extending the width of the screens are provided between the screen members on opposite sides of the depending portion of the filter element 34. This provides for maintaining the spacing of the screened members 21 and 22 substantially the same at the top as along the side edges. In order to maintain the spacerelements 35 and 36 in place Without choking off the flow of blood through the filter the spacers are spot-stitched or otherwise secured to the screen members at a plurality of points,

indicated at 37, across the width of the screens. The

provided with similar spacers to hold the screens apart without shutting off the flow of blood between the screen members, although in most instances this precaution is not necessary at the bottom of the oxygenator.

The front and back face panels of the oxygenator envelope are applied over the screen and sealed to the opposite inside marginal portions of the loop members. Blood inlet tube 31 is sealed between the panels. One face panel is provided with an oxygen inlet tube 38 sealed into the panel and the opposite face panel is provided with a similar gas discharge tube 39 sealed into that panel. Both the oxygen. inlet tube 38 and the gas vent 39 are disposed generally along the side edge opposite to that containing the gas passage openings 27 and intermediate of the top and the bottom of the screen members. The front panel 11 and the screen member 21 define a space between them into which oxygen is introduced from the oxygen inlet 38. Similarly, the back panel 12 and screen 22 define a space 41 into which carbon dioxide is released from the blood and excess oxygen from the space 40 passes through vent openings 27 to the discharge outlet 39.

The face panels 11 and 12 are sealed together at the bottom so as to form a reservoir 42 for collecting oxygenated blood for return to the patient through a blood outlet tube 43 sealed between the film panels. The reservoir 42 and blood outlet 43 may be disposed centrally in the bottom of the oxy-genator envelope, but, desirably, they are offset to one side as illustrated in the preferred embodiment of the oxygenator shown in Figure 1 wherein an inclined passage 44 is. formed between the sealed surfaces of the panels. The inclined passage 44 is an added precautionary measure. As blood flows from between the screens 21 and 22 at the bottom of the oxygenator, means is thus provided for laminar flow whereby heavier gas-free blood is permitted to flow beneath and displace upwardly any gas-containing blood of lesser density, if such be present. A vertical gas escape tube 45 communicating with the upper portion of the offset blood reservoir 42 is sealed between the panels and the front panel 11 is split adjacent the upper end of tube 45 to permit escape of gas to the atmosphere.

The film oxygenator of this invention is designed to be efficient while at the same time being simple, economical and disposable. The oxygenator envelope and its supporting loops are formed from a continuous, impervious, plastic film, such as for example: polyethylene, plasticized polyvinyl chloride, vinylidene chloride polymers, tetra fluoroethylcne polymers, trifiuorochloroethylene polymers, rubber hydrochloride and the like. The plastic films should be pure, nontoxic, strong, preferably at least partially transparent and capable of being sterilized. Preferably, the synthetic resin films should also be heat scalable for ease in manufacture of the oxygenator.

The screen members 21 and 22 must be of fine mesh, non-wettable by blood, and, of course, pure, non-toxic, strong and capable of undergoing sterilization. screens are desirably woven and many suitable synthetic resinous fiber cloths are available. Among these may be mentioned: nylon fabric; fabrics woven from polyester filaments available under the trademark Dacron; vinylidene chloride polymer screening available under the trademark Saran; fabrics woven from acrylonitrile filaments available under the trademark Orion; fabrics woven from acrylonitrile-vinyl chloride copolymers available under the trademarks Dynel and Vinylon, Type N; and the like. Perforated film and foraminous nonwoven fabric possessing the other requisite characteristics and having suitable porosity may also be used. Screen members having from about 400 to 6400 openings per square inch have been used. A preferred material is nylon mesh having from about 2000 to 3000 openings per square inch. In addition to synthetic resinous screens, metal screening (such as, for example, stainless steel) may also be used. The filter element 34 when used The may be formed of similar mesh material, preferably somewhat finer than that of the screen members.

The manifold tube 28 is also preferably formed of synthetic resinous material such as, for example: polyvinyl chloride; the transparent tubing sold under the trademark Tygon; trifiuorochloroethylene polymers available under the trademark Kel-F; tubing formed of vinylidene chloride polymers available under the trademark Saran; tubing made from tetrafluoroethylene polymers and available under the trademark Teflon and the like.

In use the oxygenator of this invention is suspended vertically in a suitable supporting rack and held under four-way tension. Supporting rods 14, 16, 18 and 20 are inserted in their respective loo-p members and tension is placed upon the rods in order to hold the oxygenator envelope taut. T he oxygenator is, of course, sterile at the time of use. The oxygen inlet 38 is connected to a suitable source of pure oxygen, preferably through a humidifier.

In a typical cardiac operation, as described in some detail in our previous applications, the patients heart is first exposed and the two large veins at the right side of the heart which return the body blood to the heart are loosely looped with tape ready to be tied. Catheters to the great veins of the heart are inserted through a slit in the right atrium and a catheter to the systemic artery is inserted through a transected subclavian artery. The oxygenator is primed by pouring a quantity of whole arterial blood into the oxygenator envelope or by arterializing venous blood through the oxygenator and then admitting it into the blood reservoir 42. The tube from the veins of the patient passes through a standard blood pump and is connected to the blood inlet tube 31 of the oxygena'tor. The blood discharge tube 43 is connected through a similar standard blood pump to return the oxygenated blood to the artery system of the patient.

With the oxygenator thus connected to the circulatory system of the patient the blood pumps are turned on and the tapes looping the blood vessels are tightened. The heart, still beating, empties of blood. The venous blood, instead of going through the heart and lungs, passes through the blood pump and into the blood inlet 31 of the oxygenator. Blood flows from the manifold 28 through the manifold openings 32 (into the filter 34 when used) and into the narrow space 23 between the screen members 21 and 22. The openings 33 at the top of the manifold prevent any airlock and any air or other gases escaping through the openings 33, pass out into the envelope from where they may escape through the discharge vent 39.

The blood flowing down between the screen members 21 and 22 forms and maintains a thin, substantially uniform film of blood. The surface tension of the blood combined with the non-wetting characteristics of the screen and the positive gas pressure against the screen insures against passage of any blood through the screen so that the only flow is downward. The thickness of the blood film is determined and maintained by the spacer elements inserted between the taut screen members. It has been found that for adequate oxygenation the film thickness (and consequently the screen spacing) should be maintained at between about 0.015 and 0.045 of an inch and preferably between about 0.025 and 0.035 of an inch.

As pure oxygen is introduced under pressure into the oxygenator envelope through the oxygen inlet tube 38 the space 40 is maintained under slight positive pressure and there is a slight ballooning effect. The entire film of blood in the space 23 between the screen is thus in intimate contact with oxygen under pressure through the multitudinous openings in the screened member 21. The opposite side of the blood film is in contact with the space 41 through the multitudinous openings in the screen 22 to permit escape of carbon dioxide from the oxygenated blood. The space 41 is likewise maintained under slight positive pressure. The excess oxygen from the oxygen inlet 38 sweeps through the space 40 in intimate contact with the blood film through the screen 21, through the plurality of vent openings 27 at the opposite side of the oxygenator envelope. It then sweeps out through the space 41 along the back face. of the blood film, carrying with it carbon dioxide displaced from the blood film, and escapes through the vent 39.

The oxygenated blood fiows downwardly through the space 23 between the screens as a continuous film to the bottom of the oxygenator where it is collected in the reservoir 42 and returned to the patient through the blood outlet tube 43. When the preferred form of oxygenator construction,.as shown in Figure 1, is employed the oxygenated blood flows from between the bottom of the oxygenator screens to the inclined passage 44 in which a downward laminar flow may take place. The heavier gas-free blood flows beneath and continuously displaces upwardly gas-containing blood of lesser density to liberate entrained gas bubbles, if any be present, and any such gas may then escape through the vent 45. This added safeguard may be used out of an abundance of caution to insure against any gas emboli, but under usual circumstances and normal operations no such added precaution should be necessary.

The oxygenator may, of course, be made in a variety of sizes inorder to provide the oxygenating capacity required by patients of varying age and Weight groups from infants to adults. In order to standardize manufacturing procedures, however, it is preferred that the oxygenator be made of a size having adequate oxygenating capacity for most infants, and then, when greater oxygenating capacity may be required, a plurality of these standard size units connected in parallel may be used. Thus, as a typical example, the oxygenator may be constructed so as to have an effective oxygenating screen surface of about 18 by 24 inches and as need for greater capacity arises a plurality of two or more of such standard size units are used connected in parallel with each other.

A circulation system incorporating the oxygenator of this invention may be provided with means for introducing supplemental venous blood as described in our previous applications. Similarly, the coronary sinus suction device for returning cardiotomy loss to the patient through the oxygenator as disclosed in our previous applications may be utilized in connection with the oxygenator of this invention.

It is apparent that many modifications and variations of this invention as herernbefore set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

We claim:

1. A blood oxygenator comprising a pair of parallel spaced apart foraminous blood filming elements enclosed within an envelope, inlet means for introducing oxygen into said envelope on one side of said pair of filming elements, gas discharge means for venting gases from said envelope on the other side of said pair of filming elements, blood inlet means for introducing blood to be oxygenated between said pair of filming elements, said blood inlet means comprising a perforated manifold tube disposed adjacent to the top of said oxygenatorenvelope and between said pair of blood filming elements, and outlet means for discharging oxygenated blood from said envelope.

2. A blood oxygenator according to claim 1 further characterized in that said pair of blood filming elements is composed of fine mesh woven screens.

3. A blood oxygenator according to claim 2 further characterized in that such screens are composed of synthetic resinous filaments non-wettable by blood.

4. A blood oxygenator according to claim 1 further characterized in that said blood filming elements are the Mechanical held substantially uniformally spaced apart by means of spacer elements between said filming elements.

5. A blood oxygenator according to claim 1 further characterized in that said oxygen inlet means and said gas discharge means are disposed generally adjacent to one side edge of said oxygenator envelope in opposite faces thereof and gas passage means to permit flow of gas around one side edge of said pair of filming elements are disposed within the envelope adjacent the side of the marginal edge of the pair of filming elements which is opposite thereto.

6. A blood oxygenator according to claim 1 further characterized in that means are provided adjacent to the side edge portion of said oxygenator for supporting and tensioning said oxygenator to maintain the pair of blood filming elements taut and substantially uniformally spaced apart.

7. A blood oxygenator according to claim 1 further characterized in that oxygenator envelope is composed of thin, relatively transparent, heat sealable synthetic resinous film.

8. A blood oxygenator comprising a pair of parallel closely spaced apart foraminous blood filming elements composed of synthetic resinous filaments woven into a fine mesh screen and enclosed within a generally transparent synthetic resinous film envelope, oxygen inlet means in one face of said envelope adjacent to one side edge thereof for introducing oxygen into said envelope on one side of said pair of filming elements, gas discharge means in the opposite face of said envelope adjacent to the same side edge as the oxygen inlet for venting gases from said envelope on the other side of said pair of filming elements, a plurality of gas passages within said envelope adjacent the side edge of said pair of filming elements opposite to said oxygeninlet and gas discharge, blood inlet means for introducing blood into the oxygenator between said pair of filming elements, said blood inlet means including a perforated manifold tube disposed between said blood filming elements ad jacent the top of the oxygenator envelope, spacer means between the opposite vertical side edges of said blood filming elements and between the upper portion thereof below said manifold tube, tensioning means adjacent the marginal edges of said oxygenator for applying tension thereto to hold the blood filming elements taut and substantially uniformly spaced apart, and a blood outlet adjacent the bottom of said envelope for discharging oxygenated blood from said envelope.

9. A blood oxygenator according to claim 8 further characterized in that said outlet means includes an inclined passage extending from adjacent the bottom of said pair of filming elements to a blood collecting reservoir, the top of said rservoir being open to the atmosphere to permit the escape of gases.

10. A blood oxygenator according to claim 8 further characterized in that said filming elements are spaced apart between about 0.015 and 0.045 of an inch.

11. A blood oxygenator according to claim 8 further characterized in that said foraminous screen filming elements are provided with between 400- and per square inch.

OTHER REFERENCES Recent Advances in the Development of Heart and Lung Apparatus Annals of Surgery, vol. 134, No. 4, October 1951, pp. 694-708 (pp. 695-702 relied on).

Brown et al.: A Simple Expendable Blood Oxygen Gas Exchanger, Surgery, vol. 40, No. 1, July 1956, pp. -112' (pp. 100-103 relied on). (Available in Science Library.) Y

Miller et al.:

6400 openings 4 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 2 981 253 April 25 1961 Richard A., De Wall et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the sai d Letters Patent should read as corrected below.

Column 3 line 66 for Vinylon'" read me Vinyon Signed and sealed this 19th day of September 1961 SEA L) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOM M-DC

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