Dialysis Pumping System

Abstract

This invention relates to a dialysis pump and pumping system primarily designed for the pumping of blood for purification in an "artificial kidney machine" using the recently announced system of the use of a single needle temporarily inserted into a vein or artery of a patient through which blood is withdrawn from the vein for purification and returned to the patient through the same needle. Such a dialysis system requires a device, commonly called an "occluder," by means of which blood from the filter is prevented from entering the needle during the suction stroke of the pump of the machine and is open to flow during the pumping stroke which, in the preferred form, exerts a greater pressure than that supplied by the body during the suction stroke of the pump.

Description

BACKGROUND OF THE INVENTION

One of the surgical miracles of the last generation has been the invention and development of the "artificial kidney machine", referred to in medical circles as a "dialysis machine", by Dr. Willem Kolff, now associated with the University of Utah. The dialysis machine was first invented about 25 years ago and much time and effort has been spent in trying to improve its operation, to make it more efficient and to make it truly portable and less expensive. One of the defects of prior machines has been the fact that they were very large, very expensive and required treatment under clinical or surgical conditions. Thus, most patients were financially unable to get treatment because such machines could be supplied only by large hospitals or well endowed clinics, and treatment had to be secured every second or third day by spending about 6 hours in the clinic. The research team directed by Dr. Kolff at the University of Utah has very recently announced a truly inexpensive dialysis machine which would be within the price range of most American families and, which is more important, could be utilized in the home. In the past, for dialysis treatment, a patient had to undergo a surgical procedure by means of which an artificial "plug-in" connection, or canula, was placed in an artery and in a vein of a patient, blood being withdrawn from the artery for treatment in the machine and then returned to the vein. Since there are relatively few spots in the body where an artery is close to the skin, the number of places where such a canula could be placed in an artery was very limited. The life of such a canula is quite short, as the natural bodily processes make it unusable, and a new costly and painful surgical procedure was required. With the new invention of a single surgical needle technique the canula problems are eliminated. In this new procedure, a single needle is inserted into a vein (many of which are close to the skin and, therfore, readily accessible for withdrawing blood samples, taking blood for transfusion or storage in a blood bank, etc.), and after being purified, the blood is injected back into the patient through the same needle. Such a system requires that a very small amount of blood be withdrawn through any suction stroke in order to avoid collapsing the vein, usually within the range of 1.5 to 2.5 cc. per stroke at a rate of between 60 to 120 cycles per minute, depending upon the age and size of the patient. During the suction stroke of the dialysis machine, the blood is taken from the body of the patient through the single needle and one leg of a Y connection; and then, during the pumping stroke, passed through the filter and back into the patient's body through the other leg of the Y connection into the same needle. Such a system requires the use of at least one valve device, or occluder, and which is operative to shut off the flow of purified blood to the patient during the suction stroke of the pump. Furthermore, this "occluder," as it is commonly called, must operate in timed sequence to the operation of a pump. Obviously, the occluder must be open for the passage of blood during the time that the pump is pushing blood through the filter and back into the body of the patient, but should completely close the purified blood delivery line during that portion of a cycle in which the pump is withdrawing blood from the body of a patient.

One of the features of the present invention is that the volume of blood pumped in each stroke is variable through a wide range and adjustments can be made easily and accurately while the pump is in operation. Another advantage is that the force applied to the blood in the conduit is also variable over a considerable range, and again adjustments can be made while the pump is in operation. More important is the fact that the pump and occluder of the present invention are isolated from the tubes carrying blood from the dialysis filter and returning it to the body, so that neither the pump nor the occluder need to be sterilized between uses. It will be understood that in such a procedure as dialysis, the needle, the blood tubes, and the filter, will have to be sterilized or replaced between each use, and this is commonly done, but it is unnecessary to sterilize either the pump or the occluder of the present invention, as the sterilized tubes are placed within the pump and occluder but do not communicate with them.

OBJECTS

It is a primary object of the present invention to provide a small, light weight pumping system for a dialysis machine.

It is a further object of the present invention to provide an artificial kidney pump with an infinitely variable volumetric adjustment.

It is another object of the present invention to provide a pumping system for a dialysis machine utilizing a single needle for the withdrawal of blood from, and its return to, the patient.

It is still a further object of the present invention to provide a quiet and positive occluder which controls the flow of the patient's blood from, and the delivery of the purified blood back to the patient, through a single hypodermic needle.

It is still a further object of the present invention to provide a surgical pump and an occluder which, in themselves, do not have to be sterilized, since only the tubes through which the blood passes and the filter needs to be sterile since the tube, or tubes, may be readily inserted through the two mentioned devices.

These and other objects of the present invention will be apparent from the specification which follows, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a diagrammatic view of the pumping system of the present invention.

FIG. 2 is a circuit diagram which controls the sequential operation of the pump and occluder of the present invention.

FIG. 3 is a cross-sectional view of the power section of the pump of the present invention.

FIG. 4 is a cross-sectional view of the pumping section of the pump of the present invention.

FIG. 5 is a cross-sectional view in enlarged detail of the one-way valve in the blood tube used in the pump shown in FIG. 4.

FIG. 6 is a view of one side of the occluder of the present invention.

FIG. 7 is a view of the other side of the occluder shown in FIG. 6; and

FIG. 8 is a plan view of the occluder of the present invention.

SPECIFICATION

The pumping system of the present invention comprises four major sections: (A) a power unit 30; (B) a pump section 50, which may be constructed integrally with the power unit 30, or which may be separated therefrom as shown in FIGS. 2 and 3; (C) an occluder 110; and (D) a power control unit 140. For ease in understanding, these four sections will be discussed separately, but for purposes of construction, the power unit 30, the pump section 50 and the power control unit 140 can be built as an integral unit, and presumably would be; however, the occluder 110 normally is preferably placed as close to the patient as possible, and therefore can be somewhat removed from the other three.

A. Power Unit

Construction of the pump section 30 is shown in detail in FIG. 3. Basically, it comprises a solenoid 31 contained within a casing 32 which may be made of plastic, or any other suitable material. The plunger 33 of the solenoid is spring-biased to an extended position by means of a relatively strong spring 40 and bears against a collapsible bellows 34. The interior of the bellows 34 communicates with a pressure chamber 35 which, by means of a tube 36, is in fluid communication with the pumping section 50. This connecting tube 36 may be valved as at 37 as shown. The chamber 35 also communicates with a filling tube 38 which must be closed as by means of valve 39. Power is supplied to the solenoid 31 in timed pulses through power line 41 leading from the power supply assembly 140 shown in FIG. 2. When electrical power is supplied to the solenoid 31, the plunger 33 is retracted, pulling the bellows 34 (to the left in FIG. 3) to its extended position, thereby sucking the fluid from the chamber 35, tube 36 and the intermediate chamber 75 in the pumping section 50. Then, when the circuit to the solenoid 31 is de-energized, the force of spring 40 forces the plunger 33 and the bellows 34 to the right, thereby expelling fluid from the bellows 34 into chamber 35 and thence by tube 36 into the interior chamber 75 of the pumping unit 50.

B. Pump Unit

The pump unit 50 is almost identical with that shown in my copending application, Ser. No. 191,207, now U.S. Pat. No. 3,724,973 but differs therefrom sufficiently that a complete description is deemed to be in order. Normally, it would be about half the size of a pump designed for heart surgery, as was the case in that application. It comprises a casing 51 that has a relatively tight fit with the bore 52 of a casing support block 53 which, in turn, is rigidly secured to a mounting plate 54 by any suitable means, such as machine bolts 55. The casing 51 can be locked in position by a set screw 56 threaded into the block 53 and registering with an annular groove 57 formed in the outer wall of the casing 51. The annular groove 57 in the casing permits rotation of the pump casing 180 if desired, but not longitudinal movement in its support.

The casing 51 is also provided with an annular groove 60 which registers with a supply port 61 to which the liquid supply tube 36 is affixed, when the pump is in the proper position. A plurality of radial orifices 62 lead from the annular groove 60 into the interior portion of the cylindrical casing 51. Preferably, a pair of O-rings 63 and 64 are contained within annular grooves 65 and 66 formed in the outer wall of the casing 51, one on each side of the supply port 61. This construction provides a water-tight seal between the casing 51 and its retaining block 53 on either side of the supply port so that no liquid will be lost during operation.

I prefer to seal the interior of the casing 51 by a flexible tubular membrane 70. Preferably, this membrane will be a silastic tube which will be passed lengthwise through the casing 51 as shown in FIG. 4. The two ends of the cylindrical membrane 70 are preferably sealed as by means of folding over a conical collar 71, placing a truncated conical thimble 72 thereover, and rigidly sealing the assembly by means of a cap 73 which is threaded onto suitable threads formed on the ends of the casing 51. A gasket member 74 compressed between the conical collar 71 at the end of the casing seals the tubular membrane 70 against leakage. Preferably, as shown in FIG. 4, the interior of the casing 51 is enlarged except at its very ends, thereby providing an elongated cylindrical chamber 75 throughout most of the length of the casing and lying between the wall of the casing 51 and the tubular membrane 70. Thus, throughout most of its length within the casing 51, the silastic tube 70 will not lie against the wall of the casing but will be embraced by the liquid which communicates with the pumping section 30. This liquid will completely encompass the tube 70 throughout most of its length within the casing at all times. This construction permits the rapid and equalized transmission of pressure to the entire length of the pump chamber on the pump stroke; and also the rapid and equalized vacuum thereto on the suction stroke. It also provides an additional safeguard against the intermingling of liquid from the pump itself to the blood being pumped. The blood to be pumped passes through a short section of silastic tubing 80 of a length slightly greater than the length of the casing 51. Preferably, this tube 80 is provided at each end with a pair of conical nipples 81 and 82 over which the blood supply tube 22 and the pump delivery tube 28 can be forced. It is obvious, of course, that the blood supply tube 22, the pump section 80 and delivery tube 28 can be fabricated as a single tube and then the nipples 81 and 82 would be unnecessary. The tube 80 is provided with a pair of one-way valves 83 which can be of any suitable construction, but preferably is of the style shown in detail in FIG. 5. Preferably, the tube 80, its nipples 81 and 82 and the pair of one-way valves 83 will be pre-sterilized and contained within a sterilized casing 84 which can be suitably sealed at the time of sterilization. When the device is to be used, the casing 84 serves to pull the assembly through the pump chamber 51 contained within the membrane 70 in the casing 51. The ends of the casing 84 can then be snipped so that the suction tube 22 can be forced over the nipple 81 and the discharge tube 28 forced over the nipple 82, and the pump is ready for operation.

I have found that the one-way valve of the type shown in FIG. 5 is better for use in a dialysis machine. Each valve comprises a stiff cylindrical collar 90 having an annular indentation 92 (semi-circular in shape in cross-section) formed adjacent the upper edge thereof. The collar is inserted (and may be cemented) within the tube 80 at the locations to lie within the tube 80 immediately adjacent the conical collars 71. Obviously, both valves are pointed in the same direction so that the valve at the inlet end will permit the entry of blood into the pumping chamber but not backwardly therefrom, while the valve in the outlet end permits the blood to be expelled from the chamber but not to return thereto. As mentioned, the collar 90 is formed with an annular groove 92, adapted to receive an O-ring 91 which is inserted over the blood tube 80 and lies within the semi-circular groove 92 formed in the stiff collar 90. This locks each one-way valve in the proper position. The semi-circular groove 92 also forms an excellent valve seat for the valve member 93 which preferably is formed of a soft silastic material. The silastic material is molded around a frame comprising a plate 94 of greater diameter than the valve seat 92 and a valve stem member 95 rigidly secured thereto. Both parts of the frame preferably are formed of metal to add weight to the valve member 93 so that gravity will readily seat it on its cooperating valve seat 92 as soon as pressure to lift the valve member 93 off the seat ceases. The metal frame also prevents an exceedingly strong backward force from forcing the valve member 93 through the seat 92, which readily can be done to a silastic valve member which does not have such metal reenforcemnt. Preferably, the silastic material forming the valve member 83 is of the soft type so that it will seat tightly against the indentation in the collar, regardless of any deformation in the collar 90. The valve member 93 is also locked against excessive upward movement by any suitable means, such as a locking member 96, which preferably can be a C-clamp whose interior diameter is smaller than the valve stem so that it can be forced over the soft silastic material which forms the valve stem. Thus, the valve member 93 is held in position between the limits imposed by collar 90.

C. Occluder

The occluder 110 is shown particularly in FIGS. 6, 7 and 8. It comprises a mounting plate 111 provided with a suitable aperture 112 so that the occluder can be hung close to the patient, or in any other suitable position. A solenoid 113 is secured to the mounting plate by any suitable means, not shown, and is supplied with electric power by a power lead 114. The solenoid armature 115 is pinned to a link 116 which, in turn, is pinned to a gear 117 that is rotatably mounted on a pin 118 secured in the mounting plate 111. A tension spring 119 pulls the gear 117 (clockwise in FIG. 6) to pull the link 116 in armature 115 to the extended position shown in this figure. The gear 117 meshes with a smaller gear 120 that is pinned on, or otherwise rigidly secured to, a shaft 121 journalled in the mounting plate 111. The gear 120 is preferably smaller than the gear 117 in order to rock this gear through a larger arc than would be secured from the direct movement of the armature 115 itself. On the other end of the shaft 121, as shown in FIGS. 7 and 8, is an occluder collar 125 which is rigidly pinned on, or otherwise secured to, the shaft 121. The outer end of the collar 125 is provided with a slot 126 adapted to receive and retain the blood delivery tube 23. It is preferred that the collar 125 be so mounted on its shaft that the slot 126 lies in a vertical position when the occluder is to permit flow of blood from the dialysis filter 26 to the patient, as is shown in FIGS. 7 and 8. This permits the flow of blood with a minimum of friction or other restrictive forces. Also, the memory of the tube itself tends to straighten it when the occluder is at rest.

When the solenoid 113 is operated and the collar 125 rocked thereby (counter-clockwise in FIG. 7), the tube 23 is rocked against a post 127 which is mounted on the backside of the plate 111 immediately adjacent the collar 125. This rocking of the tube 23 against the post 127 pinches the tube against post 127, as shown in dotted lines 23a in FIG. 7, and thereby closes the tube to the passage of blood therethrough. As soon as the pulse which operates the solenoid ends, however, the spring 119 and the elastic memory of the tube itself immediately returns the tube and occluder to the vertical position shown in these figures.

The occluder can also be operated as a "fail safe" device to shut off vital flow of blood in emergencies, as when the patient is asleep, by using the power stroke of the solenoid to open occluding action and have the spring force of spring 119 strong enough to occlude the tube 23. Thus, the occluder mechanism may replace the spring set blood clamp now used.

D. Power Supply

The power supply 140 can be mounted on any suitable member, such as a plate 141 shown in dotted lines in FIG. 2 and supplied from any suitable electrical supply, such as leads L-1 and L-2. The power supply for such devices are well-known and the present invention utilizes components that can readily be secured on the market. Hence, it is not deemed necessary to explain them in detail. It should be sufficient to note that the power supply 140 contains a converter, or transformer, 142 to convert normal A.C. current to a direct current of reduced voltage of, say, 12 volts. It also contains a pulsation, or timing circuit 143 and a power amplifier 144. The pulsation timing circuit is adapted to supply a power pulse to the lead 41 which operates the pump actuator 30 and lead 114 which actuates the occluder 110, and then break the circuits thereto. In the embodiment shown, the two pulses are simultaneous. However, it is important to note that in another form of the present invention, the timing circuit operates to supply power to the pump actuator 30 and the occluder 110 alternately, so that while power is being supplied to the solenoid 31 of the pump actuator 30, none is being supplied to the solenoid 113 of the occluder 110, and vice versa. Thus, the two solenoids 113 and 31 operate alternately, which causes a minimum requirement of power as only one of the solenoids can be operative at one time.

The heperin (anti-coagulant) pump 24 can be operated independently of the pump actuator 30 connecting its power supply line 145 to a suitable source of power. Since only 1.5 milliliters of heparin are needed per hour, this pump 24 will normally be operated independently.

It should be noted that the speed (number of cycles per minute), the length of the pulse, and the relative length of the pulses with respect to the periods of rest can be adjusted by the usual conventional means, such as adjusting member 146. Normally, the pump (and the occluder) will be operated at speeds ranging from 60 to 120 cycles per minute. The test embodiment of the present invention has been operated at speeds of from 50 to 150 cycles per minute by adjusting the timer 143.

OPERATION

(Using the single needle technique developed at the University of Utah Biomedical Laboratory)

The operation of the present device will be readily understood by reference to FIG. 1. The usual surgical hypodermic needle 30 can be inserted into any suitable vein of the patient. A Y member 21 is affixed to the needle 20 and a suction tube 22 and a delivery tube 23 are connected to the Y member 21. The suction tube 22 leads to the inlet nipple 81 of the pump 50, while an outlet tube 28 is connected to the outlet nipple 82 of the pump. The duct 28 leads to a plurality of ducts, such as 28a and 28b of the conventional dialysis filter. After being filtered, blood is collected in branch delivery tubes 23a and 23b and then passes into a bubble trap 27 and thence into the delivery tube 23. Since the filter 26 and the bubble trap 27 are of known construction, it is believed unnecessary to refer further to them. It can also be noted that it is conventional practice to inject a very minute amount (usually in the order of 1.5 milliliters per hour) of heparin into the suction tube 23 as by means of a heparin pump 24 which leads to a suitable T connection 25 in the suction tube 22. This pump can be operated by an independent power supply through lead 145. The delivery tube 23 is passed through the slot 126 of the occluder collar 125. When the power supply assembly is connected to a suitable source of power, such as conventional house current of 110 volts, it provides pulses to the pump actuator 30 and the occluder 110. When power is supplied to the solenoid 31 of the pump actuator 30, the plunger 33 of the solenoid is pulled (to the left in FIG. 3), thereby sucking liquid from chamber 35, tube 36 and the inner chamber 75 lying between the wall of the casing 51 and the inner membrane 70, which action applies suction to the tube 22 and hence draws blood through the needle 20 and Y 21. On the alternate operation, when power is shut off from the solenoid 31, the spring 40 of the pump actuator forces the diaphragm armature and its associated bellows 34 (to the right in FIG. 3), and hence forces liquid back through chamber 35, tube 36 and into chamber 75 of the pump. This, in turn, forces blood from the inner tube 80 up through the outlet one-way valve 83 and thence into discharge tube 28 leading to the dialysis filter 26. Simultaneously with the sequential operation of the solenoid 31 of the pump actuator 30, the solenoid 113 of the occluder 110 is supplied with sequential pulses of power in step with those supplied to solenoid 31 of the pump actuator. When supplied with power, the occluder solenoid 113 rocks the collar 125 to pinch the tube 23 against post 127, and thereby terminate the flow of blood from the filter 26 into the patient. With the termination of power to solenoid 113, spring 119 rocks gears 117 and 120 to the position shown in FIG. 6, thereby rocking collar 125 to straighten delivery tube 23 and permit blood to flow to needle 20. Thus, the pump actuator 30 and the occluder 110 are operated in a timed sequence to simultaneously operate the pump 50 in its suction stroke and close occluder 110 to the flow of blood, and then operate the pump in its pumping stroke and open the occluder to the flow of blood.

The timing of the pump cycles can be varied according to modification of the pulsation timing circuit by well-known means, and that the amount of blood supplied at any stroke can be accurately controlled by adjustment of the valve 37 in the pump actuator duct 36. These changes can be made while the pump is in operation or preset as desired.

It is believed that these and other advantages of the pump system of the present invention will be obvious to those skilled in the art. Accordingly, it is intended that all modifications which lie within the scope of the underlying inventive concepts are to be included within the scope of the claims and the invention is not to be limited to the particular forms herein shown and described.

Claims

I claim:

1. A dialysis pumping system for use in connection with a single needle dialysis technique in a machine in which blood is taken from a patient and returned to the patient after treatment through a single needle, said pumping system comprising:

a. a power section including

1. a chamber adapted to receive a liquid,

2.

2. a flexible bellows for communicating with said chamber,

3. a solenoid for operating said bellows, and

4. an outlet from said chamber;

b. a pumping section comprising

1. a cylinder, the intermediate portion of which has a larger diameter than its ends,

2. a cylindrical flexible diaphragm within said cylinder, adapted to receive a flexible tube carrying blood, said tube being provided with one-way check valves, and

3. means for sealing the ends of said cylindrical diaphragm to the ends of said cylinder and thereby providing a space between the cylinder and the cylindrical diaphragm, and

4. passageways into the space lying between said cylinder and said flexible diaphragm, said passageways communicating with the outlet from the power section chamber;

c. an occluder comprising

1. a solenoid,

2. a rotary member rocked by said solenoid,

3. a slot in said rotary member adapted to receive a flexible tube leading from a dialysis device,

4. a fixed post adjacent one end of said slot in said rotary member; and

d. a power section for sequentially supplying discrete pulses to said power

section solenoid and to said occluder solenoid. 2. The pumping system of claim 1 wherein the solenoid in the power section and the solenoid in the occluder are operated simultaneously.

3. The pumping system of claim 1 wherein the solenoid in the power section and the solenoid in the occluder are operated alternately.

4. The pumping system of claim 1 wherein the one-way valve in the flexible tube carrying blood comprises:

a. a short stiff cylinder adapted to fit inside of said tube, said cylinder having an annular indentation adapted to receive a flexible ring,

b. a flexible ring embracing said blood tube and seated tightly in the indentation in said cylinder,

c. a conical valve member formed of soft material enclosing a metal plate of a diameter greater than the inside diameter of the indentation in said cylinder and a metal stem depending from said plate, and

d. means affixed to said stem adapted to prevent said stem from passing through said indentation in said cylinder.