Blood oxygenator

Abstract

A blood oxygenator is provided with a preformed defoaming member of open-cell sponge material of synthetic plastic disposed in the defoaming chamber in series between the oxygenating chamber and the blood reservoir chamber of the oxygenator. Spaces are provided between the defoaming member and the upper and lower walls of the defoaming chamber to produce a reduced resistance to the flow of gas and blood. A fine mesh filter and funnel are connected to the defoaming chamber to gently transfer and filter blood flowing to the reservoir.

Description

BACKGROUND OF THE INVENTION

This invention relates to blood oxygenators and more particularly to oxygenators of the "bubble" type which are used in extracorporeal circulation systems which assume the functions of the heart and lungs during cardiac and other surgery.

Oxygenators of this type generally include an oxygenating chamber in which blood and gas are mixed to produce a blood foam, a defoaming chamber containing a defoaming member, and a reservoir chamber for receiving the defoamed oxygenated blood for return to the arterial system of the patient. Obviously, undisolved gas and gas bubbles must be eliminated from the oxygenated blood before returning it to the patient. While the defoaming member removes most of the gas from the oxygenated blood foam, some past constructions tended to produce blood churning and blood bubbles due to the transfer of blood from the downstream end of the defoaming chamber to the reservoir chamber. Even small heights between the lowermost tip of the defoaming chamber and the reservoir sometimes caused blood to splash and trap air with the danger that such trapped air may enter the arterial system of the patient. Past constructions have not been entirely satisfactory in transfering the blood from the defoaming chamber to the pool of blood in the reservoir without introducing air bubbles into the blood, or they have failed to provide means for eliminating such bubbles that might occur as a result of the transfer of blood to the reservoir.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a blood oxygenator with means to substantially ensure against the possibility of air being trapped in the blood contained in the blood reservoir.

In accordance with one form of the present invention a funnel and filter assembly in disposed at the downstream end of the defoaming chamber of an oxygenator with the lower ends of both submerged in the blood within the blood reservoir.

These as well as other objects and advantages of the present invention will become apparent from the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of an oxygenator in accordance with a preferred embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is an enlarged cross-sectional view taken along line 3--3 of FIG. 1;

FIG. 4 is an enlarged side view of the defoaming member of the oxygenator of FIG. 1;

FIG. 5 is a cross-sectional view taken along the line of 5--5 of FIG. 4;

FIG. 6 is a bottom view of the defoaming member of FIG. 4;

FIG. 7 is an enlarged view of a sheet of material from which the funnel of FIG. 1 is formed;

FIG. 8 is a side view of the funnel formed by folding the sheet of FIG. 7;

FIG. 9 is an enlarged plan view of a sheet of material from which the filter of FIG. 1 is formed; and

FIG. 10 is an enlarged side view showing the funnel and filter assembly used in the oxygenator of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, and particularly to FIGS. 1-3, there is shown an oxygenator 10 of the "bubble" type which is adapted for connection in an extracorporeal circulation system of a patient during surgery. The oxygenator 10 includes a pair of translucent sheets 12 and 14 of a synthetic plastic material, such as thermoplastic polyurethane sheet material. The sheets are heat sealed or welded together along a predetermined path forming a seam 16 which appears in cross-section in FIG. 1. Seam 16 forms an elongated defoaming chamber 18 and a blood reservoir chamber 20. The reservoir chamber has its upper portion connected in fluid communication with the defoaming chamber 18, and is provided with an outlet 22 at the bottom adapted for connection through a suitable blood pump to the arterial system of the patient. In the illustrated embodiment, a blood oxygenating chamber 24 is provided by a seperate open ended plastic tube 26 formed of the same material as sheets 12 and 14 and heat sealed at its upper end by a peripheral seam 28 to the upper end portion of the defoaming chamber 18.

An oxygenating gas diffuser 30 is disposed in tube 26 in fluid tight sealing engagement with its walls. A plastic tube 32 has one end connected to the diffuser 30 and is adapted to be connected at the other end with the venous system of the patient for supplying venous blood to oxygenating chamber 24. A plastic tube 34 has one end connected to the diffuser 30 and is adapted to be connected at the other end to a source of oxygenating gas. Diffuser 30 has an internal chamber connected with tube 34, and an upper plate 36 at the top of the chamber. Plate 36 is preferably formed with a plurality of small holes (not shown) through which the oxygenating gas must bass. The tube 32 extends through the plate 36 so that the blood will flow over the plate. In this way, the gas will be evenly distributed in the venous blood and cause blood foam to rise in the oxygenating chamber 24.

Disposed in the defoaming chamber 18 is a preformed defoaming member 38 for removing bubbles and undissolved gas from the blood. A funnel and filter assembly 40 is connected to chamber 18 at the downstream end for gently transferring oxygenated blood from chamber 18 to the reservoir 20 and removing any gas bubbles that might flow out of chamber 18, as will be fully described hereafter. The defoaming chamber 18 is provided with a vent 42 in the upper wall adjacent the downstream end of defoaming member 38 to permit the escape of excess and undissolved gas to the atmosphere.

The defoaming chamber 18 and member 38 are the subject matter of an application Ser. No. 406,501 filed on the same day as this application and having the same assignee.

Referring now also to FIGS. 4-6, defoaming member 38 is a unitary member formed of a synthetic plastic sponge material of open-cell construction. Preferably, it is formed of a polyurethane sponge material and coated throughout with an anti-foam agent, such as a silicone grease wellknown for this purpose. The defoaming member is shown elongated and having an upper wall 44 which is flat and parallel with the longitudinal axis of the member, and a bottom wall 45 having a pair of arcuate recesses 46 and 48. As seen in FIG. 5, the upper and lower walls 44 and 45 are beveled so that the overall cross-sectional configuration of member 38 is somewhat eliptical as is the defoaming chamber 18 as seen in FIG. 2. Also, the downstream tip, indicated at 50, is tapered. With this configuration the member 38 fits snugly within the defoaming chamber 18 with tip 50 within the funnel and filter assembly 40 as seen in FIG. 1.

When the defoaming member 38 is in the oxygenator of FIG. 1, the recesses 46 and 48 provide radial spaces between the bottom wall of chamber 18 and member 38 to provide free flow portions in the blood flow path to increase the rate of blood flow through the defoaming chamber. The defoaming member 38 engages the bottom wall of chamber 18, on each side of each of the recesses so that any gas flowing with the blood in these spaces will flow through defoaming member 38 and be released from the blood. The upper wall of chamber 18 is defined by an undulating portion of the seam 16 producing three indentations 52 which provide longitudinally spaced, radial spaces 54 and 56 between the upper walls of the chamber 18 and defoaming member 38 which enhance the flow of excess or undisolved gas through the defoaming chamber 18 to the vent 42 to reduce operating pressures and improve the defoaming action.

The funnel and filter assembly 40 includes a funnel 58 of synthetic plastic, such as polyurethane, and a pocket-like filter member 60 which is formed of a suitable fine-mesh cloth material such as a synthetic plastic, perferably nylon, for example, 100 micron nylon filtration cloth. FIG. 7 shows the pattern or cutout 58' which is folded to form the funnel shown in FIG. 8, the funnel having a seamless bottom wall and being generally triangular in side view. Similarly, a cut-out or pattern 60' shown in FIG. 9 is folded to form the pocket filter seen in FIG. 10.

The cutouts 58' and 60' may be placed in face-to-face relation and the sides 62 and 64 of the cutout 58' heat-sealed to the sides 66 and 68, respectively, of the filter pattern 60' to provide a circumferential heat seam 70 which is partially seen in FIG. 10. The two connected cutouts are then folded and the opposed free edges of the filter pattern are heat sealed together by a heat seam indicated at 72 in FIG. 10 to form the pocket which is open only at the top at seam 70. Seam 72 also seals, the opposed relatively small corners 73 and 74 (FIG. 7) of the funnel together. Thus, the funnel 58 is completely received in the filter 60. Before heat sealing the two plastic sheets 12 and 14 to form the chambers 18 and 20, the funnel and filter assembly 40 is heat sealed to the sheets by a circumferential seam partially shown in FIG. 1 at 75 which seals seam 70 to the downstream end of the defoaming chamber 18.

As seen in FIG. 1, the bottom wall of the defoaming chamber 18 is inclined downwardly from the oxygenating chamber 24 toward the reservoir 20. Likewise, the lower wall of the funnel 58 is inclined downwardly toward the reservoir, it being inclined somewhat less than that of the bottom wall of chamber 18 so as to provide a substantially smooth connection with chamber 18 and gently transfer blood to the reservoir 20.

Before connecting the oxygenator 10 for operation, a predetermined amount of priming blood is introduced into the reservoir 20, such as through a port 76. the reservoir 20 is filled with priming blood up to a level indicated by the indicia or arrow 77 provided on the oxygenator so that the lower tips of the funnel 58 and filter 60 extend into the blood slightly below the blood level indicated also by line 78 in FIG. 1. In this way, the funnel 58 prevents blood from dripping from the walls of the defoaming chamber and from the defoaming member into the pool of blood in the reservoir, and thereby avoids splashing and entrapment of gas. While the funnel gently transfers oxygenated blood from the defoaming chamber 18 to the blood in the reservoir, the filter 60, which is downstream of the funnel and surrounds it, removes any bubbles that might reach it or that might be created by blood leaving the funnel. The filter will also remove any debris or blood clots.

In operation, venous blood flows through tube 32 and over the diffuser 30 and oxygenating gas flows from tube 34 producing a foam which rises in the oxygenating chamber 24. As the foam rises, carbon dioxide is released from the blood and oxygen is disolved in the blood to provide a desired oxygenation of the blood. The defoaming member 38 removes bubbles from the foam and allows gas and blood to pass through it. Gas tends to rise in the defoaming member 38 so that some flows downwardly along the upper wall of the defoaming chamber 18 through spaces 54 and 56 toward the vent 42, the spaces serving to lower the resistance to gas flow through chamber 18. The oxygenated blood and foam tend to flow downwardly through the defoaming member to the lower wall of chamber 18. Blood flows along the lower wall with some blood able to flow through the free flow portions of the blood path formed by recesses 46 and 48, which lower the resistance to blood flow through the chamber 18 to obtain a desired relatively high rate of blood flow through the oxygenator. All of the blood flowing from chamber 18 flows into the funnel 58 where it is gently transferred to the blood pool in reservoir 20 and all of the blood from the funnel must flow through the filter 60 before it is returned to the patient. As previously mentioned, any debris, blood clots, or bubbles reaching the filter 60 will be removed and the gas from any bubbles released to the atmosphere by vent 42. The oxygenated blood is, of course, returned to the arterial system of the patient by way of outlet 22.

As seen in FIG. 3, the bottom inclined wall of the funnel 58 and its lower tip are spaced laterally from the sheets 12 and 14 and this permits the blood that is flowing out of the funnel to readily circulate in the pool around the funnel tip and obtain good mixing of blood to avoid stagnant blood. With the lowermost ends of the funnel and filter spaced downstream of the defoaming member 38, the funnel provides a channel or path for the defoamed blood beyond the defoaming member.

While a preferred form of the invention has been described herein, it will be apparent that various changes and modifications thereto may be made without departing from the true spirit and scope of the invention as defined in the claims which follow.

Claims

What is claimed is:

1. A blood oxygenator comprising an oxygenating chamber, means for delivering venous blood and oxygenating gas to said oxygenating chamber for producing foamed blood in said oxygenating chamber to oxygenate the blood, a reservoir for receiving oxygenated blood and having an outlet for discharging oxygenated blood, said reservoir being normally filled with blood to an operating blood level, indicia means including a visual mark in fixed relation to said chamber providing a visual indication of said operating blood level, defoaming means including a defoaming chamber connected between said oxygenating chamber and said reservoir, and a defoaming member in said defoaming chamber for removing gas from said foamed blood, a funnel member connected to the downstream end of said defoaming chamber and inclined downwardly toward said reservoir with the lower end thereof disposed below said indicia means to gently transfer blood from said defoaming chamber to said reservoir, said funnel member being disposed to receive and pass all of the blood flowing from said defoaming means to said reservoir and said outlet, and a filter member extending below said lower end of said funnel and said indicia means so that all of the blood flowing from said funnel member to said reservoir and said outlet flows through said filter member.

2. The blood oxygenator of claim 1 wherein said funnel member extends beyond the lowermost end of said defoaming means.

3. The blood oxygenator of claim 1 wherein said funnel and filter members each has opposed side wall with the side walls of said funnel member disposed between the side walls of said filter member.

4. The blood oxygenator of claim 1 wherein said reservoir has opposed side walls, and the lower end of said funnel member is spaced from the side walls of said reservoir.

5. The blood oxygenator of claim 4 wherein said filter member comprises a pocket of fine mesh filtering material, and said funnel member is disposed in and surrounded by said pocket.

6. The blood oxygenator of claim 5 wherein said funnel member and said filtering material are of synthetic plastic.

7. The oxygenator of claim 5 wherein said funnel member is a unitary sheet folded to provide a seamless bottom wall for transfering blood from said defoaming chamber to said reservoir.

8. The oxygenator of claim 7 further including a pair of synthetic plastic sheet members predeterminately heat sealed along a seam to define said defoaming chamber and said reservoir, and wherein said filter member is open only at the upper end thereof, said funnel member has an upper open end heat sealed to said upper end of said filter member to provide a funnel and filter assembly open at the upper end, and said upper end of said assembly is heat sealed to said sheet members at the lower end of said defoaming chamber.