Intra-arterial Blood Pump

Abstract

The disclosure illustrates an intra-aortic circulatory assist balloon pump, expanding and contracting in synchronism with a patient's heart rhythm to assist systemic circulation. The balloon pump comprises an elongated elastic membrane having a number of compartments supplied with pressure for expansion from an exterior source via a central tube and orifices between compartments. A second tube connects one of the end compartments and extends to an exterior flexible capacitance device that preferentially expands relative to the end compartment, thereby preventing "bubble blowing."

Description

The present invention relates to circulatory assist devices and more particularly to intra-arterial blood pumps.

In recent years the balloon pump has been used to aid a patient's systemic circulation when physiological processes result in a relatively inelastic aorta. Briefly, the balloon pump comprises an elongated elastic membrane inserted into the aorta of a patient and inflated and deflated in synchronism with the heart rhythm through a tube connected to a pressure control device. The membrane is deflated as the left ventricle of the heart contracts (systole) to discharge blood into the aorta. After contraction the aortic valve closes to prevent backflow into the heart and the membrane expands to force blood out of the aorta and through the arteries to the various organs of the body. While this type of pump is highly advantageous by reason of its simplicity, it poses a particular problem known as the "bubble blowing" effect. It has been found that during inflation of the membrane the blood near the center of the membrane requires a greater interior pressure for expulsion than the blood at the ends. With a uniform inflation pressure, both ends of the membrane preferentially expand and occlude the aorta, thus trapping blood between the ends of the membrane. This greatly reduces the pumping efficiency and can give rise to additional problems of clotting, etc.

There have been a number of balloon pump configurations designed to alleviate the ballooning effect. An excellent example may be found in the patient to R. T. Jones, U.S. Pat. No. 3,504,662, entitled "Intra-Arterial Blood Pump," and of common assignment with the present invention.

It is an object of the present invention to provide an intra-aorta balloon pump which efficiently aids in the systemic circulation and minimizes the tendency for occluding the aorta.

The above ends are achieved by an intra-arterial balloon pump having a plurality of compartments in a flexible membrane. Adjacent compartments are interconnected by orifices. A first tube extends from an exterior pressurizing and depressurizing source to one of the middle compartments of the membrane. A second tube connects with at lest one of the end compartments of the membrane and extends to a remote flexible capacitance device designed to preferentially inflate relative to the end compartment thereby eliminating the bubble-blowing effect.

The above and other related objects and features of the present invention will be apparent from a reading of the description of the disclosure shown in the accompanying drawing and the novelty thereof pointed out in the appended claims.

In the drawing:

FIG. 1 shows an intra-arterial pump embodying the present invention, along with pressurizing and depressurizing apparatus with which it is used;

FIG. 2 shows the intra-arterial pump of FIG. 1 in a partially inflated condition.

Referring particularly to FIG. 1 there is shown a patient's heart, generally indicated by reference character 10, and an aorta 12 extending from the hart to the circulatory system. A circulatory assist balloon-type pump, generally indicated by reference character 14, is positioned in the aorta 12. The pump 14 comprises an elastic elongated generally tubular closed end membrane 16 having an inflated outside diameter approximating the inner diameter of the aorta. The membrane 16 is divided into a plurality of compartments 15, 17, 19, 21 and 23 by annular flexible webs 18.

A central flexible tube 20 extends into membrane 16 and has an opening 22 for entry and discharge or fluid into one of the middle compartments of the membrane 16, herein shown as compartment 17. A check valve 26, shown in schematic form, permits one-way flow from another middle compartment 21 into tube 20. The webs 18 have orifices 28 of predetermined size to interconnect in series the chambers within membrane 16. The membrane 16 may be formed from a plastic material inert to body fluids, such as polyvinyl chloride, polyurethane latex, silicon rubber, a polysiloxane-polyurethane block copolymer, as disclosed in U.S. Pat. No. 3,562,352, or other materials. The tube 20 may also be formed from similar inert materials.

A pressure control system 30, located outside of the patient's body, pressurizes and depressurizes the membrane 16 with a gas, such as nitrogen, helium or carbon dioxide, in synchronism with the patient's heart rhythm as sensed by electrocardiogram electrodes. The apparatus shown in U. S. Pat. No. 3,266,487 is particularly suitable for this purpose.

A second elongated flexible tube 32, as shown herein, extends through the center of tube 20 and opens into at least one of the end compartments. As herein show, tube 32 connects with compartment 23. The remote end of tube 32 extends outside the aorta of the patient and connects with a flexible capacitance device 36, illustrated as an elastic membrane. The flexibility of the elastic membrane 36 is selected so that it preferentially expands relative to end compartment 23, as later described. A check valve 38 in tube 32 provides one-way flow from tube 32 to tube 20.

In operation, the pressure control device 30 deflates membrane 16 as the patient's left ventricle (not shown) of his heart 10 pumps blood into the aorta 12. The deflation of the membrane 16 greatly eases the effort required of the left ventricle because it does not have to contract against the pressure in the system. When the left ventricle has ceased contracting, the aortic valve closes to prevent backflow of blood into the heart and the membrane 16 is inflated by pressure control system 30 to push the blood out of the aorta and through the circulatory system. During pressurization of the membrane 16 gas enters through opening 22 into compartment 17. From there it flows to compartment 15 and in series relation from compartment 19 toward end compartment 23. This sequentially pressurizes the compartments, thus causing the compartments away from the heart 10 to inflate first, as shown in FIG. 2.

As noted above, the end compartment 23 has a tendency to blow up relative to the middle compartments because of the lower interior pressure required to expel blood from the region around compartment 23. The membrane outside the patient's body preferentially expands relative to end compartment 23, as shown in FIG. 2, to lower its interior pressure during inflation, thus preventing this early expansion. When the compartment are fully inflated they have a uniform pressure and the membrane 16 and capacitance device 36 assume the shapes shown in FIG. 1. It will be apparent to those skilled in the art that the flexibility of the membrane 36 can be precisely tailored to the conditions existing in the aorta to lower the pressure in compartment 23 during the transient inflation a sufficient amount to prevent the bubble effect.

During inflation of membrane 16 the pressure in tube 20 is higher than the pressure in tube 23 thereby opposing any flow of gas from tube 32 to tube 20. During deflation, however, the pressure in tube 20 is rapidly lowered by pressure control system 30 and the gas is discharged into tube 20 through opening 22, check valve 26 and check valve 38. The provision of the check vales greatly assists deflation of the membrane 16 and achieves a more uniform contraction.

The balloon pump arrangement described above blocks the lower portion of the aorta and pumps blood primarily to the carotid, coronary and subclavian arteries, generally designated by reference character 48. The reason for this is that in some cases it is felt that the blood in the aorta should be pumped to the arteries feeding the brain and the upper extremities rather than downward through the circulatory system. The end compartment 15 then expands preferentially relative to the rest of the compartments and the middle compartments inflate in sequence thereby providing a peristaltic action while the exterior member 36 prevents bubble blowing of the end compartment 23.

The above balloon-type pump provides a highly simplified and effective way of minimizing the bubble effect experienced by this type of intra-arterial pumps. The flexibility of the exterior elastic membrane 36 may be conveniently controlled as to its flexibility to precisely vary the rate at which it expands relative to the end compartment 34. While the arrangement shown illustrates a pump which preferentially supplies blood to the patient's brain and upper region extremities, it should be understood that a pump may be designed to pump blood in both directions by connecting the flexible membrane to both compartments and inflating the membrane through the center compartment 19.

While the preferred embodiment of the present invention has been illustrated, it should be apparent to those skilled in the art that other modifications may be utilized without departing from the spirit and scope thereof.

Claims

Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:

1. An intra-aortic circulatory assist balloon pump positionable in a patient's aorta for inflation and deflation by an exterior pressurizing means in synchronism with the patient's heart rhythm, said balloon pump comprising:

an elastic elongated generally tubular closed end membrane having an outside diameter approximating the inner diameter of the aorta:

a plurality of transverse flexible webs dividing said membrane into a pair of end compartments and a plurality of middle compartments, said webs having orifices of predetermined areas;

means for forming a first passageway extending from the interior of said elastic membrane and adapted to be coupled to said exterior pressurizing means, said passageway means having an opening into a middle compartment in said membrane;

means for forming a second passageway having a first end connecting with at least one of the end compartments of said membrane and a second end extending outside of said patient; and

a capacitance device connected to the second end portion of said second passageway means, said capacitance device being preferentially expandable relative to said end compartment during pressurization of said membrane thereby minimizing early inflation of said end compartment relative to said middle compartments.

2. Apparatus as in claim 1 wherein said capacitance device comprises an elastic membrane connected to the second end portion of said second passageway means.

3. Apparatus as in claim 1 wherein said second passageway means connects with the end compartment of said membrane adjacent to the patient's heart.

4. Apparatus as in claim 1 further comprising a first check valve connecting said first passageway means to another middle compartment of said membrane, said first check valve permitting fluid to pass only from said chamber to said first passageway means, thereby assisting the deflation of said membrane.

5. Apparatus as in claim 4 further comprising a second check valve connecting said second tube to said first tube, said second check valve only permitting flow from said second tube to said first tube whereby the deflation of said membrane is assisted.

6. Apparatus as in claim 5 wherein said first and second elongated tubes are coaxial with one another, said second tube being positioned through the interior of said tube.

7. Apparatus as in claim 1 wherein said first tube connects with a middle compartment adjacent the end of said membrane remote from said heart whereby inflation of said membrane expels blood toward the heart.