WO2017085543A1

WO2017085543A1 - Dialysis machine with valve clamp arrangement

Info

Publication number: WO2017085543A1
Application number: PCT/IB2016/001697
Authority: WO
Inventors: Clive Buckberry
Original assignee: Quanta Fluid Solutions Ltd
Priority date: 2015-11-19
Filing date: 2016-11-29
Publication date: 2017-05-26
Also published as: GB201520400D0; GB2544514B; GB2544514A

Abstract

A dialysis machine comprising a cartridge having a body covered by a membrane, the body being rigid relative to the membrane, the membrane being deformable by fluid pressure, the cartridge defining at least one valve, a machine body having a first platen and a second platen, the machine body arranged to receive the cartridge between the first platen and the second platen; a valve clamp arrangement comprising a pneumatic actuator, the valve clamp arrangement provided in the machine body and normally spaced from the cartridge, the valve clamp arrangement being arranged to apply a fluid pressure differential directly to the deformable membrane to open and close the at least one valve; and wherein the valve clamp arrangement further comprises a mechanical actuator arranged to close the at least one valve by mechanical actuation to physically contact the cartridge.

Description

Dialysis Machine with Valve Clamp Arrangement

The present invention relates to a dialysis machine with a valve clamp arrangement. Dialysis is a treatment which replaces the body's renal function of removing excess fluid and waste products, such as potassium and urea, from blood. The treatment is either employed when renal function has deteriorated to an extent that uremic syndrome becomes a threat to the body's physiology (acute renal failure) or, when a longstanding renal condition impairs the performance of the kidneys (chronic renal failure).

There are two major types of dialysis, namely hemodialysis and peritoneal dialysis. In hemodialysis, the patient's blood is removed from the body by an arterial line, is treated by the dialysis machine, and is then returned to the body by a venous line.

A peristaltic pump is commonly used to control the flow of blood. To prevent air being returned to the patient in the event of failure or any other failure mechanism returning blood to the patient which may cause harm, the peristaltic pump may act as a first clamp on the arterial line, when a failure mode is detected. A further external clamp is also commonly employed on the venous line.

When a membrane blood pump is used to control the flow of blood, as disclosed in WO2013/121 163, it is necessary to provide an external clamp on both the venous and arterial lines to prevent air returning to the patient in the event of failure or any other failure mechanism returning blood to the patient which may cause harm.

This is arrangement is bulky and adds complexity to the machine.

The present invention aims to provide a clamp arrangement for a dialysis machine which is compact, and reduces the overall complexity of the dialysis machine.

According to a first aspect of the present invention there is provided a dialysis machine comprising a cartridge having a body covered by a membrane, the body being rigid relative to the membrane, the membrane being deformable by fluid pressure, the cartridge defining at least one valve, a machine body having a first platen and a second platen, the machine body arranged to receive the cartridge between the first platen and the second platen; a valve clamp arrangement comprising a pneumatic actuator, the valve clamp arrangement provided in the machine body and normally spaced from the cartridge, the valve clamp arrangement being arranged to apply a fluid pressure differential directly to the deformable membrane to open and close the at least one valve; and wherein the valve clamp arrangement further comprises a mechanical actuator arranged to close the at least one valve by mechanical actuation to physically contact the cartridge.

Providing the clamp and valve actuator within the same arrangement results in a compact arrangement for a dialysis machine. The mechanical actuator may be biased to a retracted position by the pneumatic actuator. The mechanical actuator may be biased to an extended position by a biasing element. In that way, failure of the pneumatic system results in extension of the clamp. The biasing element may be selected to overcome a limited loss of pneumatic pressure, as well as a total loss.

The biasing element may be a coil spring. The mechanical actuator may be a piston. Such an arrangement provides a compact valve clamp.

The piston may have a head, the head arranged to physically contact the cartridge when the mechanical actuator is arranged to close the at least one valve. By providing a head to contact the cartridge and close the valve, the piston may be smaller thereby facilitating a more compact design.

The mechanical actuator may have a channel to provide fluid communication between the pneumatic actuator and the flexible membrane. The channel may be provided axially in the piston. Such an arrangement provides a compact valve clamp. The head of the piston may be an inverted cone. The piston may be mounted in the platen. The piston may be flush with the platen when in the retracted position. In this way, the mechanical actuator does not interfere with the normal operation of the valve when in a retracted position. The head of the piston may be compliant to provide a better conformal seal to the features of the valve.

The dialysis machine may have a mechanical lifter to return the mechanical actuator to the retracted position from the extended position. According to a second aspect of the present invention there is provided a method of clamping a valve in a dialysis machine; the method comprising the steps of: providing a dialysis machine having a cartridge, the cartridge having a body covered by a membrane, the body being rigid relative to the membrane, the membrane being deformable by fluid pressure, the cartridge defining at least one valve, the dialysis machine further having a machine body, the machine body having a first platen and a second platen, the machine body arranged to receive the cartridge between the first platen and the second platen; the dialysis machine further having a valve clamp arrangement comprising a pneumatic actuator, the valve clamp arrangement provided in the machine body and normally spaced from the cartridge, the valve clamp arrangement being arranged to apply a fluid pressure differential directly to the deformable membrane to open and close the at least one valve; and wherein the valve clamp arrangement further comprises a mechanical actuator arranged to close the at least one valve by mechanical actuation to physically contact the cartridge; detecting the presence of air in a fluid connector transporting blood to, from or within the machine; closing the at least one valve by removing the pneumatic pressure applied to the mechanical actuator to mechanically actuate the mechanical actuator to physically contact the cartridge and clamp the deformable membrane against the rigid body and thereby close the valve. The presence of air may be detected ultrasonically. Alternatively, or additionally, the presence of air may be detected acoustically. An embodiment of the invention will now be described, by way of example only, with reference to the accompanying figures, in which: Figure 1 is a schematic view of a dialysis system using a membrane blood pump;

Figure 2 is a sectioned side view of a dialysis machine using a membrane blood pump; Figure 3 is a plan view of a portion of a dialysis cartridge, showing a valve in greater detail;

Figure 4 is a sectioned side view along line I-I of the valve of Figure 4, with the valve in an open position;

Figure 5 is a sectioned side view along line I-I of the valve of Figure 4, with the valve in a first closed position;

Figure 6 is a sectioned side view of a dialysis machine having two valve clamp arrangements;

Figure 7 is a sectioned side view of a dialysis machine of Figure 3, showing the valve in greater detail, with the valve in an open position; Figure 8 is a sectioned side view of a dialysis machine of Figure 3, showing the valve in greater detail, with the valve in a second closed position; and

Figure 9 is a schematic view of part of the valve clamp, showing the retraction mechanism.

Dialysis System Referring to Figure 1, a dialysis system 10 is shown. The dialysis system 10 includes a patient 20, a dialysis machine 30, a dialysis cartridge 40, sources of dialysate 16 and a dialyser 18. The source of dialysate 16 may include for example a dialysis premix, a bicarbonate mix, or an acid mix.

The dialyser 18 may be of a known kind, such as those consisting of a rigid cylinder body housing hollow polymer fibres.

A first series of connectors 12 fluidly connects the patient 20 to the dialysis machine 30. A second series of connectors 14 fluidly connects the dialysis machine 30 with the dialyser 70. The first series of connectors 12 include the arterial and venous lines referred to above and are responsible for extracting and returning blood to the patient. Ultimate fluid connection to the patient is made by a vascular access device such as a needle 13. The second series of connectors 14 are responsible for passing the blood to be treated, as well as the dialysate mix, to the dialyser 18, and returning the treated blood and used dialysate mix back to the dialysis machine 30. Membrane Blood Pump

Referring to Figure 2, the dialysis machine 30 and dialysis cartridge 40 act together as a membrane pump 50. The dialysis machine 30 includes a first platen 31 and a second platen 38. The first and second platens 31, 38 together define a cavity into which the dialysis cartridge 40 is received.

The first platen 31 has a cartridge engaging surface 32 and an opposite non-cartridge engaging surface 37. The cartridge engaging surface 32 defines a concave recess 33. A fluid port 34 is defined in the concave recess 33, fluidly connecting the cartridge engaging surface 32 and non-cartridge engaging surface 37 of the first platen 31. A pressure pneumatic pump 68 provides a source of positive air pressure and a vacuum pneumatic pump 69 provides a source of negative fluid pressure. The pressure pneumatic pump 68 and vacuum pneumatic pump 69 are provided on the non- cartridge engaging surface 37 of the first platen 31. The fluid port 34 is fluidly connected to the pressure pneumatic pump 68 and the vacuum pneumatic pump 69 via a drive valve 62. The drive valve 62 is controlled by a controller 64.

Together, the concave recess 33, fluid port 34, drive valve 62, pneumatic pumps 68, 69 and controller 64 form a membrane pump driver 58.

The dialysis cartridge 40 has a rigid body 42 having concave recess 44 covered by a flexible membrane 46. The concave recess 44 and the flexible membrane 46 form a membrane pump cavity 52 having an inlet 54 and an outlet 56 leading into and out of the membrane pump cavity 52 respectively.

In use, the cartridge 40 abuts the membrane pump driver 58, as the first platen 31 sealingly engages with the cartridge 40. The recess 33 and the flexible membrane 46 form a drive chamber 60. Drive chamber 60 is arranged, in use, opposite membrane pump cavity 52. Air flow into and out of the drive chamber 60, via the fluid port 34 is regulated by drive valve 62, as controlled by controller 64.

The drive valve 62 is a proportional valve having a variable sized orifice therein. The drive valve 62 is controllable to change the size of the orifice, thereby controlling the flow therethrough.

When the drive valve 62 is operated to allow fluid to flow into the drive chamber 60 from the pressure pneumatic pump 68, the flexible membrane 46 is moved towards the recessed surface 44 of the cartridge 40 and any blood that is in the membrane pump cavity 52 is expelled via the outlet 56.

When the valve 62 is operated to allow air to flow out of the drive chamber 60 to the vacuum pneumatic pump 69, the flexible membrane 46 is drawn away from the recessed surface 44 and towards concave recess 33 in the first platen 31 so that blood is drawn into the pump cavity 52 from the inlet 54.

In order further to control the flow of blood through the membrane pump 50 the inlet 54 to the membrane pump cavity 52 has a blood inlet valve 70 and the outlet 16 from the membrane pump cavity 52 has a blood outlet valve 72 associated therewith, as will be explained in more detail below.

In operation, when the valve 62 is operated to allow fluid to flow into the drive chamber 60 from the pressure pneumatic pump 68, the blood inlet valve 70 is closed and the blood outlet valve 72 is open so the blood within the membrane pump cavity 52 exits the outlet 56 via the blood outlet valve 72. When the valve 62 is operated to allow blood to flow out of the drive chamber 60 to the vacuum pneumatic pump 69, the blood inlet valve 70 is open and the blood outlet valve 72 is closed such that blood is drawn into the membrane pump cavity 52 through the inlet 54 via the open blood inlet valve 70.

Blood Inlet and Outlet Valves The blood inlet valve 70 and blood outlet valve 72 are substantially identical, such that only the blood inlet valve 70 shall be described in detail. The blood inlet valve 70, (see Figures 3, 4 and 5) is defined by the rigid body 42 and flexible membrane 46 of the cartridge 40. The blood inlet valve 70 has an inlet 73 and an outlet 74. The blood inlet valve 70 has an outer circular upstanding wall 75 and an inner circular upstanding wall 76, the inner circular upstanding wall 76 forming the valve seat. Arranged inwardly of the inner circular upstanding annular wall 76 is a valve aperture 77 which acts an outlet for the blood inlet valve 70. The circular inner upstanding annular wall 76 is recessed from the outer circular upstanding annular wall 75. Arranged between the inner and outer circular upstanding annual wall 76, 75 is a sector aperture 78 which acts as an inlet for the blood inlet valve 70. Accordingly, the blood inlet valve 70 has a valve inlet 73 in the form of sector aperture 78 and a valve outlet 74 in the form of valve aperture 77. In the embodiment shown in Figures 4 and 5 the inner circular upstanding wall 76 forming the valve seat is shown to be recessed from the outer circular upstanding wall 75. In alternative embodiments, the upstanding wall 76 can be flush with or indeed above the level of the outer circular upstanding wall 75.

Valve Clamp Actuator Assembly

Referring to Figure 6, the dialysis machine 30 further comprises two valve clamp actuator assemblies 80, 82. The two valve clamp actuator assemblies 80, 82 are provided on the first platen 31. A first valve clamp actuator assembly 80 is associated with the blood inlet valve 70 and a second valve clamp actuator assembly 82 is associated with the blood outlet valve 72. The first and second valve clamp actuator assemblies 80, 82 are substantially identical and as such, only the first valve clamp actuator assembly 80 shall be described in detail.

The first valve clamp actuator assembly 80 is arranged on the non-cartridge engaging surface 37 of the first platen 31. The first valve clamp actuator assembly 80 includes a pneumatic actuator 84 and a mechanical actuator 86.

The pneumatic actuator 84 is similar in composition to the pump driver 58 of Figure 2. The pneumatic actuator 84 comprises the pressure pneumatic pump 68, the vacuum pneumatic pump 69 together with a valve clamp valve 63 and a valve clamp controller 65.

The mechanical actuator 86 comprises a piston 88, a coil spring 90 and a retraction mechanism 92 (see Figures 7 and 8). The cartridge engaging surface 32 of the first platen 31 further defines two conical recesses 35. The conical recesses 35 are smaller in size than the concave recess 33 of the membrane blood pump. The conical recesses 35 correspond to the locations of the blood inlet and outlet valves 70, 72 of the membrane blood pump 50. A fluid port 36 is defined in each of the conical recesses 35, fluidly connecting the cartridge engaging surface 32 and non-cartridge engaging surface 37 of the first platen 31 via bore 39.

The piston 88 of the mechanical actuator 86 extends through the bore 39 provided in the first platen 31. The piston 88 is slidably movable with respect to the bore 39. The piston 88 has a channel 89 extending therethrough. The channel 89 is coaxial with the piston 88.

The piston 88 is biased to an extended position, in which the piston 88 physically contacts the cartridge 40 to press the flexible membrane 46 against the valve seat 76, to close the valve 70, by a coil spring 90. The piston 88 is biased to a retracted position, spaced from the cartridge 40, by the pneumatic actuator 84.

Pneumatic Operation of the Blood Inlet and Outlet Valves

The blood inlet and outlet valves 70, 72 operate in a substantially identical fashion, such that only the operation of the blood inlet valve 70 shall be described in detail. The blood inlet valve 70 is operated by the valve clamp actuator assembly 86 applying, alternately pressure and vacuum to the flexible membrane 46 via the channel 89.

As discussed previously, the rigid body 42 of the dialysis cartridge 40 is covered by a flexible membrane 46. The flexible membrane 46 rests against the outwardly facing surface of the outer circular upstanding annular wall 75 when the blood inlet valve 70 is in the un-actuated, open state.

In use, the cartridge 40 abuts the cartridge engaging surface 32 of the first platen 31. The concave recess 33 and the flexible membrane 46 form a valve chamber 85. The valve chamber 85 opposes the blood inlet valve 70. Fluid flow into and out of the valve chamber 85, via the fluid port 36, is regulated by the valve clamp valve 83, as controlled by controller 65. In order to change the condition of the blood inlet valve 70 from the open position to the closed position, the dialysis machine 30 applies a positive pressure, (arrow P in Figure 5), to the exterior surface of the flexible membrane 46 in order to drive the inner surface of the flexible membrane 46 on to the outwardly facing surface of the inner circular upstanding annular wall 260. This closes the valve aperture 77 thereby preventing flow through the blood inlet valve 70.

Positive pressure "P" is applied by operating the valve clamp valve 63 to allow air to flow into the valve chamber 85 from the pressure pneumatic pump 68.

In order to change the condition of the blood inlet valve 70 from the closed position to the open position, the dialysis machine 30 applies a negative pressure, to the exterior surface of the flexible membrane 46 in order to draw the inner surface of the flexible membrane 46 away from the outwardly facing surface of the inner circular upstanding annular wall 260. This opens the valve aperture 77 thereby allowing flow through the blood inlet valve 70.

The negative pressure is applied by operating the valve clamp valve 63 to allow air to flow from the valve chamber 85 to the vacuum pneumatic pump 69.

With the blood inlet valve 70 in the open state, the blood flows over the inner circular upwardly standing wall 76 and through the valve aperture 77 so as to exit the blood inlet valve 70 via the outlet 74. In Figure 5 the blood inlet valve 70 is shown in its open position in which blood can enter the valve via the inlet 73, pass over the inner circular upstanding wall 76 and out of the outlet 74. Thus, the flow of fluid is up through an outer inlet, over the valve seat 76 and out through an inner inlet.

The blood inlet valve 70 is shown in a first closed position in which the flexible membrane 46 has been actuated by the application of a positive pressure to the outer surface of the flexible membrane 46. This application of pressure P has caused the flexible membrane 46 to deflect causing the flexible membrane 46 contact the inner circular upstanding wall 76 thus creating a barrier between the inlet 73 and outlet 74.

Pneumatic-Mechanic Operation of the Blood Inlet and Outlet Valves

In Figure 7, the piston 88 is shown in a retracted position. The piston 88 is a hollow cylinder terminating in a piston head 94. The piston head 94 is an inverted cone. In the retracted position, the piston head 94 is arranged flush with the conical recess 35 defined in the cartridge engaging surface 32 of the first platen 31. Thus the flexible membrane 46 is actuatable between the open and first closed positions described above without interference with the piston 88.

In Figure 8, the piston 88 is shown in an extended position. The piston 88 is extended such that the piston head 94 clamps the flexible membrane 46 against the valve seat 76. The piston head 94 is sized to cover the valve seat 76. Thus the blood inlet valve 70 is in a second closed position, where flow through the blood inlet valve 70 is prevented.

In use, the piston 88 has channel 89 to convey pressure and vacuum from the pumps 68, 69 to the flexible membrane 110. The channel 89 is fluidly connected to the pneumatic actuator by fluid conduit 66 (see Figure 9). The piston 88 has a cap 93. The cap 93 is received within a piston chamber 87 of the mechanical actuator 86. As the piston 88 is slidably movable with respect to the bore 39, the piston cap 93 is slidably moveable with respect to the walls of the piston chamber 87. The piston cap 93 seals with the walls of the piston chamber 87. The piston cap 93 therefore defines an upper portion of the piston chamber 87 and a lower portion of the piston chamber 87, the upper and lower portions being fluidly discrete from one another and variable in volume as the piston 88 is actuated between the extended and retracted positions. The pneumatic actuator 84 is fluidly connected to the lower portion of the piston chamber 87 by fluid conduit 66. The vacuum pneumatic pump 69 is directly fluidly connected to the upper portion of the piston chamber 87 by fluid conduit 67. The piston 88 is held open pneumatically, flush with the first platen 102, at all times except when a failure mode is reported. The piston 88 is held open pneumatically, by the fluid connection of the vacuum pneumatic pump 69 with the upper portion of the piston chamber 87, which overcomes the biasing force of the spring 90.

A failure mode may be detected by various known means. For example an ultrasonic detector may be used to detect the presence of air within any of the first or second series of connectors 12, 14 which transport blood. Detecting air within such a connector results in the failure mode which is reported to the controller 65. The controller 65 removes the vacuum pneumatic pressure applied to the mechanical actuator 86. The piston 88 is returned against the flexible membrane 46 and dialysis cartridge 40 by the spring 90 to force a closure of the blood inlet valve 70 by clamping the piston head 94 against the valve seat 76 in the second closed position.

Alternatively, a failure mode may be detected because the temperature of the dialysate is out of a pre-determined range, or the composition of the dialysate is out of a predetermined range. Alternatively still, a failure mode may be detected because a restriction, due to clothing, has been detected, or because a different method of operation is required. A different method could be a single needle method, where needle in flow and needle out flow operations are separated such that they occur sequentially in time.

The retraction mechanism 92 is included to return the piston 88 from an extended position to a retracted position in order to return blood manually to the patient or relieve pressure if necessary. The retraction mechanism 92 is a mechanical connection of the piston cap 93 to a lever 99 provided on the outside of the dialysis machine 30.

It is conceivable within the scope of the invention that the inlet and outlet on all the valves are switched, that is to say that the flow of fluid is up through a central inlet, over the valve seat 76 and down an outer outlet. Commonly two blood inlet valves and two blood outlet valves are provided on a dialysis cartridge. The valve clamp arrangement can therefore be applied to more than one of the blood inlet valve and one of the blood outlet valve without departing from the scope of the invention.

Furthermore, the dialysis machine 30, and dialysis cartridge 40 may together define more than one membrane blood pump 50, each membrane blood pump 50 having valve clamp actuator assemblies 80, 82 associated with their inlets and/or outlets.

Claims

1. A dialysis machine comprising:

a cartridge having a body covered by a membrane, the body being rigid relative to the membrane, the membrane being deformable by fluid pressure, the cartridge defining at least one valve,

a machine body having a first platen and a second platen, the machine body arranged to receive the cartridge between the first platen and the second platen;

a valve clamp arrangement comprising a pneumatic actuator, the valve clamp arrangement provided in the machine body and normally spaced from the cartridge, the valve clamp arrangement being arranged to apply a fluid pressure differential directly to the deformable membrane to open and close the at least one valve; and wherein the valve clamp arrangement further comprises a mechanical actuator arranged to close the at least one valve by mechanical actuation to physically contact the cartridge.

2. A dialysis machine according to claim 1 wherein the mechanical actuator is biased to a retracted position by the pneumatic actuator.

3. A dialysis machine according to claim 1 wherein the mechanical actuator is biased to an extended position by a biasing element.

4. A dialysis machine according to claim 3 wherein the biasing element is a coil spring.

5. A dialysis machine according to any of claims 1 to 4 wherein the mechanical actuator is a piston, the piston having a head, the head arranged to physically contact the cartridge when the mechanical actuator is arranged to close the at least one valve.

6. A dialysis machine according to claim 5 wherein the piston head is compliant.

7. A dialysis machine according to claim 5 or claim 6, wherein the mechanical actuator has a channel to provide fluid communication between the pneumatic actuator and the flexible membrane.

8. A dialysis machine according to claim 7 wherein the channel is provided axially in the piston.

9. A dialysis machine according to any of claims 5 to 8 wherein the head of the piston is an inverted cone.

10. A dialysis machine according to claim 1 further comprising a mechanical lifter to return the mechanical actuator to the retracted position from the extended position.

1 1. A dialysis machine according to claim 2 wherein the piston is mounted in the platen.

12. A dialysis machine according to claim 1 1 wherein the piston is flush with the platen when in the retracted position.

13. A method of clamping a valve in a dialysis machine; the method comprising the steps of:

providing a dialysis machine having a cartridge, the cartridge having a body covered by a membrane, the body being rigid relative to the membrane, the membrane being deformable by fluid pressure, the cartridge defining at least one valve, the dialysis machine further having a machine body, the machine body having a first platen and a second platen, the machine body arranged to receive the cartridge between the first platen and the second platen;

the dialysis machine further having a valve clamp arrangement comprising a pneumatic actuator, the valve clamp arrangement provided in the machine body and normally spaced from the cartridge, the valve clamp arrangement being arranged to apply a fluid pressure differential directly to the deformable membrane to open and close the at least one valve; and wherein the valve clamp arrangement further comprises a mechanical actuator arranged to close the at least one valve by mechanical actuation to physically contact the cartridge;

detecting the presence of air in a fluid connector transporting blood to, from or within the machine;

closing the at least one valve by removing the pneumatic pressure applied to the mechanical actuator to mechanically actuate the mechanical actuator to physically contact the cartridge and clamp the deformable membrane against the rigid body and thereby close the valve.

14. A method according to claim 13 wherein the presence of air is detected ultrasonically.

15. A method according to claim 13 or 14 wherein the presence of air is detected acoustically.

16. A dialysis machine substantially as hereinbefore described with reference to Figures 1 to 9.