Intra-aortic Balloon System

Abstract

An intra-aortic balloon system includes a balloon adapted to be disposed within an aorta and to change from a minimum volume to a maximum volume at which the balloon substantially but not entirely fills the aorta. The change in balloon volume is effected by connecting the balloon through a catheter to a slave casing cup covered by a diaphragm. The balloon, catheter and covered slave casing cup constitute a substantially closed volume filled with physiologically acceptable gas. Movement of the diaphragm portion of the closed volume produces a substantially equal volume variation of the balloon. A master casing cup is disposed against the other side of the diaphragm and is supplied with a working gas, the pressure of which is changed according to a program. Leakage of physiologically acceptable gas is detected and made up when necessary. The slave casing cup volume is changeable to match different balloons or to match the same balloon under changed operating conditions.

Description

The invention described herein was made in the course of, or under, a contract with the Department of Health, Education, and Welfare.

In recent years successful techniques have been provided for assisting the action of the heart in individuals having heart difficulties. One of the ways is by means of a catheter to introduce a relatively elongated, flexible balloon, connected to the catheter, into the aorta of an individual. By appropriately expanding and contracting the balloon there is effectuated a blood pumping action assisting the natural pumping action of the heart. The variation in balloon volume is timed to afford the best results.

While this technique is valuable and is increasingly acceptable, there are still some difficulties. The balloon is expanded and contracted in response to variations in pressure of a contained actuating gas. Care must be taken that this gas is physiologically acceptable and readily dissolved in blood. A poorly absorbed gas such as air or helium is dangerous and even fatal in the event any part of the structure within the aorta or connecting blood vessels fails and releases the air or helium to the blood. Variation in pressure and volume of the balloon must be carefully regulated and timed according to a program. Overexpansion of the balloon obstructs or blocks the aorta, hinders rather than helps the heart action, and damages the contacted aorta surface.

There is sometimes difficulty in properly selecting the balloon for the particular aorta with which it is momentarily utilized. Not only does the aorta size vary from individual to individual but also the aorta size varies from time to time in a specific individual, depending largely upon his condition of health and the pressure of his blood. In fact, it is sometimes necessary to have multiple insertions and removals to change the size of intra-aortic balloons used as the patient recovers. As his blood pressure increases, the diameter or size of the aorta may increase also.

It is therefore an object of the invention to provide an intra-aortic balloon system in which the volume variation of the balloon can be very carefully regulated to afford a substantially predetermined or maximum pumping effect without the risk or danger of expanding the balloon to an extent that the aorta is entirely occluded.

Another object of the invention is to provide an intra-aortic balloon system in which the periodic variation in balloon size can be carefully controlled and regulated, particularly as to maximum balloon size.

A further object of the invention is to provide an intra-aortic balloon system in which a mechanical rupture or failure of the balloon or its connecting catheter is not of a dangerous or serious nature.

Another object of the invention is to provide an intra-aortic balloon system in which the balloon volume change can be varied from time to time from the outside and without the necessity of changing balloons.

A further object of the invention is to provide an intra-aortic balloon system in which a substantially constant, small volume of actuating gas is maintained in the balloon catheter system.

A further object of the invention is to afford special actuation of the system in the event there is an excessive leakage of actuating gas.

Another object of the invention is to use air or a common gas as the principal working gas.

A further object of the invention is in general to provide an improved intra-aortic balloon system.

Other objects together with the foregoing are attained in the embodiment of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIG. 1 is a diagram, many parts being in cross-section on a median plane, showing an intra-aortic balloon system pursuant to the invention as it is actually employed;

FIG. 2 is a cross-section, the plane of which is indicated by the line 2--2 of FIG. 1;

FIG. 3 is a cross-section through a part of a modified master and slave unit employed in the system; and

FIG. 4 is a view similar to FIG. 3 showing a further modified form of master and slave mechanism utilized in the intra-aortic balloon system, parts being shown in cross-section, parts being broken away and other parts being diagrammatic.

In a preferred form and as it has been worked out and adapted for use in a human aorta 6 having a reasonably well known but perhaps variable cross-section or diameter, I preferably provide a flexible catheter 7 of a recognized sort that is readily introduced through a blood vessel and extends into the aorta. The distal end 8 of the catheter is preferably closed and in the vicinity of that end the catheter is provided with a number of apertures 9 affording access from the interior of the catheter to the interior volume 11 of a balloon 12. The ends of the balloon are preferably firmly attached to the catheter end 8 and also to an intermediate zone of the catheter so that while the interior volume 11 of the balloon is in free communication with the interior volume of the catheter, the balloon itself is substantially closed and is not in communication with the interior of the aorta 6.

The catheter 7 on the outside of the body is preferably provided with a connection 13 to a mechanism for varying the pressure within the catheter and within the balloon 12 so as correspondingly to expand and contract the balloon. Particularly in accordance with the invention, it is preferred to provide a substantially closed system for this purpose. Consequently, the catheter connection 13 extends to a slave gas connector 14 on a slave casing cup 16. As an example, this is a conical body having a peripheral flange 17. The interior of the cup is in free communication through the catheter 7 with the balloon interior 11. Extending across the slave casing cup is a flexible diaphragm 18 on one side exposed to the interior volume of the slave cup. On the other side the diaphragm is exposed to the interior volume of a master casing cup 21. This cup has a flange 22 appropriately secured to the flange 17, preferably with the diaphragm 18 clamped therebetween. The master casing cup 21 has a fitting 23 receiving a tube 24 which extends to an actuator 26.

The actuator is a power driven mechanism subject to the control of an input signal received through a line 27 either from a timing device or from the patient himself, such as a signal from his heart. When appropriately signaled the actuator 26 takes in a working gas such as atmospheric air from an inlet 28 and forces the working gas out through the tube 24 and into the master cup 21. The effect of this is to increase the pressure within the cup 21 acting against the diaphragm 18. The momentarily superior pressure distorts the diaphragm 18 and displaces it into the slave casing cup 16 until the diaphragm comes into contact with the walls of that casing cup. This limits the volume change due to the diaphragm entering the slave casing cup to a predetermined or set value. Stated differently, it is immaterial how high the pressure may happen to rise within the master chamber 21, the diaphragm can displace through a certain volume only and that is all since thereafter the diaphragm simply rests against and is supported by the walls of the slave casing cup.

Use of atmospheric air on the master side of the diaphragm is safe since all of that part of the structure is outside the body and breakage or leakage is not critical. Large volumes of air can be used, if desired, without an economic penalty.

The balloon volume system, including the slave casing cup, the catheter and the balloon, is preferably substantially closed in order to maintain a fixed or constant volume. The gas therein utilized is either an inert gas or a gas that is physiologically acceptable, such as carbon dioxide. The volume is small so that the cost of a special gas is not great. In the event of rupture of the balloon or of the catheter within the body, the amount of gas that can escape is thus strictly limited. Since the gas is innocuous its escape, although perhaps unwanted, is not dangerous.

To supply the substantially closed balloon gas volume with a proper gas, the slave casing cup 16 is provided with a tube 31 extending to a suitable source 32 of an acceptable gas under some small pressure. A valve 33 is interposed in the tube 31 so that the slave casing cup can be entirely cut off from the gas source 32 or can, under proper control, be opened to such source.

In the general operation of this structure the actuator 26 under control of a signal through the line 27 varies the working gas pressure in the master casing cup 21 in a programmed or predetermined fashion as to timing and duration or pattern of pressure fluctuation alternately increasing and decreasing the interior pressure in the master casing cup. There is correspondingly produced, by deflection of the diaphragm, a comparable pressure fluctuation in the slave casing cup. This pressure fluctuation is transmitted through the closed system to afford a corresponding volume variation of the balloon 12.

Should it be observed at any time that the volume of the balloon system is reduced due to a hole, diffusion, or other gas leakage, (and some leakage is virtually inevitable) then the valve 33 can be momentarily opened to replenish the gas supply to the balloon or slave system and restore the gas content to the proper amount.

While a large variation in pressure within the actuator 26 is not particularly critical, nevertheless the pressure within the master casing cup can readily be monitored and if it goes below a set or desired value or outside a selected range the actuator 26 can readily be operated to make up the deficiency or release the excess and so restore the desired operating pressure values.

Particularly in accordance with the invention, I afford means for varying the volume of the slave casing cup so that the balloon can be made to cycle in different diameter ranges. it can thus be made to follow enlargement of the aorta due to increasing blood pressure. It is also thus feasible to insert a standard size inert balloon into aortas of different sizes and then operate the balloon through a desired size range, always with the aim of obtaining maximum pumping without complete obstruction of the aorta, i.e., always keeping the balloon from touching much of the aorta wall.

To that end, as particularly shown in FIG. 3, the diaphragm 18 is mounted across the mouth of the slave casing cup 16 by means of a ring 36 urged toward a special flange 37 on the slave casing cup by a plurality of fasteners 38. The interposed diaphragm is properly clamped. The ring 36 is formed with external threads 39 with which mate internal threads 41 on the interior of a flange 41 included in the master casing cup 21. Preferably, the configuration of the interior wall 43 of the master casing cup is made to follow quite closely the desired configuration of the diaphragm 18 when flexed in one direction.

When the parts are in the position shown in FIG. 3 and the casing cups are quite close together, the diaphragm 18 can flex between the two extreme positions shown by the broken lines in that figure, being then almost entirely supported on one or the other of the adjacent cup walls. The excursion of the diahragm is a minimum amount in this case so that a minimum volume change occurs. When the cups are rotated relative to each other on the threads, they are spaced farther apart in an axial direction. The diaphragm 18 then can have a greater excursion before resting upon the cup walls at its extreme positions. A greater volume is swept through. By appropriately rotating the cups relative to each other so that greater diaphragm flexure and distortion can occur, a variation in volume of the always closed balloon gas system is effectuated. This can be accomplished at anytime, even during the operation of the structure so that changes in aorta size or aortas of different original diameter can immediately be compensated for.

Since at the present time, with presently acceptable materials and gases some minor leakage seems to be unavoidable, I sometimes prefer to use a construction as illustrated in FIG. 4. This is generally identical with all of the structure previously described except that in addition to the single diaphragm 18 I preferably utilize a second diaphragm 46 overlying the diaphragm 18 and clamped into position therewith. There is an exception in that between the peripheries of the diaphragms 18 and 46 there is interposed a washer 47 having at least one radial passage 48 therethrough leading to an outlet pipe 49. Leakage through the diaphragm 18, therefore, can discharge through the pipe 49 directly to the atmosphere.

Preferably, any gas discharge is monitored. One way of accomplishing this is to provide a pressure gauge 51 on the pipe 49 in an upstream portion and to restrict the pipe so that the pressure gauge 51 affords an indication of the amount of gas escaping.

In lieu of or in addition to the gauge 51 there can be provided an enlarged chamber 52 connected to the pipe 49 and carrying a disc 53 having a restricted orifice 54 therein. The chamber 52 is connected to a duct 56 leading to an evacuating device. Lines 57 and 58 connected on opposite sides of the orifice 54 lead to a sensor 59 actuated when the pressure drop across the orifice 54 becomes excessive. When actuated the sensor 59 sends out a signal to a line 61 (FIG. 4) received through the line 61 (FIG. 1) to operate an actuator 62. This correspondingly terminates the balloon pumping and evacuates line 24.

As a further refinement, the mechanism lends itself to the use of a pressure sensor 63 detecting aortic blood pressure and effective upon an actuator 64 to move the cups 16 and 21 with respect to each other so that the volume swept through by the diaphragm is automatically varied pursuant to blood pressure.

Claims

What is claimed is:

1. An intra-aortic balloon system comprising a slave casing cup having a peripheral flange; a slave gas connector opening into said slave casing cup; a master, casing cup having a peripheral flange; means movably engaging said master casing cup flange; a master gas connector opening into said master casing cup; means including at least one diaphragm between said cups engaging said peripheral flanges and overlying said casing cups for movement through a central position and between deflected positions on opposite sides of said central position; means including the walls of said casing cups for limiting said movement of said diaphragm; an aortic balloon; a catheter at one end joined to and communicating with said aortic balloon and at the other end joined to and communicating with said slave gas connector, said aortic balloon, said catheter, said slave casing cup and said diaphragm together defining a substantially closed volume; means for supplying a physiologically acceptable gas to said substantially closed volume; a supply of working gas under pressure; means for supplying said working gas under pressure to said master casing cup to move said diaphragm; and means for imposing a programmed pressure change cycle on said working gas supplied to said master cup.

2. A system as in claim 1 in which said limiting means includes conical walls of said casing cups.

3. A system as in claim 1 in which said means movably engaging said master casing cup flange comprises means for moving said master casing cup and said slave casing cup toward and away from each other.

4. A system as in claim 1 in which said slave casing cup has a mouth, said diaphragm overlies said mouth and on one side engages said peripheral flange of said slave casing cup, said means movably engaging said master casing cup flange comprises a ring engaging the other side of said diaphragm, and means for urging said peripheral flange of said slave casing cup and said ring toward each other.

5. A system as in claim 4 in which said ring is provided with first threads, and said master casing cup has second threads engaging said first threads.