CA2018296A1

CA2018296A1 - Apparatus and method to test for valve leakage in a pump assembly

Info

Publication number: CA2018296A1
Application number: CA002018296A
Authority: CA
Inventors: Michael W. Lawless; Walter L. Jimison; Giovanni Pastrone; Anthony C. Yung
Original assignee: Abbott Laboratories
Current assignee: Abbott Laboratories
Priority date: 1989-06-07
Filing date: 1990-06-05
Publication date: 1990-12-07
Also published as: JPH0330776A; AU623782B2; EP0406562A2; US5000664A; EP0406562A3; AU5602690A

Abstract

APPARATUS AND METHOD TO TEST FOR
VALVE LEAKAGE IN A PUMP ASSEMBLY
Abstract of the Disclosure Apparatus and method for determining leakage, particularly of valves, in a pumping cassette. A cassette (70) includes a primary valve (34) and a secondary valve (36), which may be selectively activated to control the source of fluid input to the cassette. The cassette also includes an inlet valve (48) and an outlet valve (56) disposed on each side of a pumping chamber (52). Downstream of the outlet valve is disposed a pressure sensor (60) which produces a signal indicative of the pressure of fluid within the cassette at that point. The cassette also includes an air-in-line sensor (40), disposed between a manifold line (38) that connects the primary and secondary valve in fluid communication with an air trap reservoir (44). Leakage in the inlet or outlet valves is detected by closing both valves, pressurizing fluid in the pumping chamber for a predetermined period of time, and then opening the outlet valve. If a pressure pulse having an amplitudeless than a predetermined level is detected downstream of the outlet valve when it is opened, either the inlet or outlet valve has leaked. The primary and secondary valves are checked for leakage either by pressurizing fluid in the pumping chamber and checking for retrograde flow of air trapped in the air trap reservoir through the air-in-line sensor, or by pressurizing fluid trapped in the cassette, holding the pressure for a period of time before closing the inlet valve, and then opening the outlet valve to detect a pressure pulse propagating downstream of the outlet valve, using the pressure sensor. If a pressure pulse of less than the predetermined magnitude is detected, one of the primary or secondary outlet valves is leaking. Both tests also detect leakage of other portions of the pumping cassette.

Description

9~

APPARATUS AND METHOD TO TEST FOR
VALVE LEAKAGE IN A PUMP AS~;E~IBLY
Technical Field This invention generally relates to a pump assembly including a plurality of 5 valves and particularly, relates to apparatus and method for detecting leakage in any of the valves or the pump assembly.
- Background of the Invention Disposable pump cassettes are frequently employed to infuse medicinal fluids into a patient. A pumping cassette may include a plastic housing having a10 front and a rear portion, betweeh which an integral elastic membrane is encapsulated. One part of the housing has a number of ports through which actuators of a pump drive mechanism extend, interacting with the elastic membrane to control fluid flow through the cassette. A pump plunger on the driveunit presses against the membrane to reciprocatively pressurize liquid trapped in a 15 pumping chamber formed between the membrane and the back of the housing.
Similarly, actuator rods extend from the drive unit through ports in the housing, pressing against the membrane to interrupt fluid flow through valve passages formed in the back of the housing. A microprocessor in the pump drive controls the pump plunger and actuator rods to effect a desired rate of delivery of 20 medicinal fluids to the patient, and in some units, is capable of selecting between a plurality of different sources by opening an appropriate selector valve in thecassette.
Selection of the source fluid and pumping rate or volume are normally determined by an operator programming the pump drive in response to a display 25 prompt. Significant leakage through the valves in the pump cassette can create a potentially harmful variation from the programmed value in the quantity of medication actually delivered to a patient, or in the case of a leaking selectorvalve, may allow a m,edicinal fluid to enter the pump cassette when infusion of the fluid into the patient is not desired. Leskage of the valves or in other parts of the pump cassette, e.g., due to a poor seal between the elastic membrane and housing, is difficult or impossible to detect by visual inspection and rnay occur after the cassette was originally inspected for leaks during its manufacture. In view of the potential harm to the patient should significant leakage go undetected, there isclear justification for evaluating the leakage integrity of all valves and of the cassette assembly when it is first used to administer drugs, and perhaps at periodic intervals thereafter.
Apparstus and a method for detecting valve leakage in a pump cassette are disclosed in U.S. Patent No. 4,657,490. A reciprocating plunger pressuri~es and 10 pumps fluid from a pumping chamber in the cassette described in this patent. To check for leakage, a stepping motor advances the plunger to elevate the pressureof liquid trapped in the pumping chamber between an inlet valve and an outlet valve. Attached to the plunger is a load cell that produces a signal indicative of the force required to pressurize the liquid trapped in the pumping chamber. If the 15 signal produced by the load cell fails to indicate that an increase in force is required to elevate the pressure of the liquid, a system problem is indicated.
Either the liquid supply is depleted, gravity feed of liquid is insufficient to fill the pumping chamber, or the inlet or outlet valve or both are leaking, allowing liquid to escape from the pumping chamber as the plunger is advanced.
Use of a load cell to detect multiple causes of system failure reduces the complexity of the device; however, this approach cannot determine which of the three possible problems has been detected. Moreover, in the disclosed method shown in the prior art, there is no provision for testing other valves in the cassette for leakage. The present invention provides a more effective apparatus to detect25 and identify valve leakage~
Summary of the Invention In accordance with the present invention, a pump assembly having the capacity to self test for leakage includes a pumping chamber in which liquid is pressurized during a pump cycle An inlet valve is operative to periodically 30 interrupt fluid flow into and out of the pumping chamber, with respect to a source of the fluid that is disposed upstream of the inlet valve. Fluid flow into and out from the pumping chamber through a delivery passage is controlled by an outlet valve, which periodically interrupts the fluid flow when the pump assembly is operating to pump ~luid.
Downstream of the outlet valve is disposed a pressure sensor that senses the pressure of fluid in the delivery passage and produces a signal indicative of that pressure. Control means are included for controlling the pumping cycle and include self test means that are connected to receive the signal produced by thepressure sensor. The self test means are operative to filJ the pumping chamber with the fluid, close the inlet and outlet valves, and to effect at least a partial pumping cycle to pressurize fluid in the pumping chamber. After a predetermined 5 time interval, the self test means open the outlet valve to de~ermine whether the pump assembly has leaked during the predetermined time interval, as a function of the signal produced by the pressure sensor after the outlet valve is opened.
When the outlet valve is open, a pressure pulse should propagate down the delivery passage from the pumping chamber. If the maximum amplitude of the 10 pressure pulse is less than a predetermined value, the self test means are operative to detect that unacceptable leakage from a volume of fluid nominally trapped between the inlet and outlet valves has occurred during the predetermined time interval. Preferably, the self test means repetitively test for leakage anddetermine that the pump assembly is leaking only if a predetermined number of 15 such tests indicate leakage.
The pump assembly may include selector valve means, disposed upstream of the inlet valve and connected in fluid communication therewith by an inlet passage. The selector valve means select at least one inlet port from among a plurality of inlet ports on the pump assembly for fluid communication with the 20 inlet valve and pumping chamber.
Detection of leakage from a volume of fluid nominally trapped between selector valve means and the outlet valve is accomplished by the self test means, by filling the inlet passage and pumping chamber with fluid, closing the selector valve means and the outlet valve, and effecting at least a partial pumping cycle to 25 pressuri~e fluid in the inlet passage and in the pumping chamber. After a second predetermined time interval, the self test means close the inlet valve, then open the outlet valve, and determine if the pump assembly has leaked during the second predetermined time interval, as a function of the signal produced by the pressure sensor after the outlet valve is opened. If the maximum amplitude of the pressure 30 pulse propagating down the delivery passage is less than a predetermined value, the self test means are operative to detect a leak in the pump assembly.
To effect an alternate preferred leakage tes~, the pump assembly includes an air trap reservoir disposed on the inlet passage, and an air-in-line sensor disposed in the inlet passage between the air trap reservoir and the selector valve means.
35 The air-in-line sensor produces a signal indicative of the presence of air in the inlet passage where the air-in-line sensor is disposed and is connected to provide that signal to the self test means. If air is trapped in the air trap reservoir, the ~Q~

self test means are operative to determine whether the pump assembly is leaking by filling the inlet passage and pumping chamber with liquid, closing the selector valve means and the outlet valve, and effecting at least a partial pumping cycle to pressurize liquid in the pumping chamber and in the inlet passage. The self testmeans then detect leaksge from a volume of fluid nominally trapped between selector valve means and the inlet valve as a function of the signal produced bythe air-in-line sensor. This signal indicates a leak upstream of the air-in-linesensor if, after the pumping cycle is initiated, the signal from the air-in-linesensor changes to indicate the presence of air rather than liquid, since the leakage causes air in the air trap reservoir to enter the air-in-line sensor.
A method including steps generally consistent with the functions implemented by the elements of the apparatus described above represents a further aspect of this invention.
Brief Description of the Drawings FIGURE 1 schematically illustrates the flow path of a liquid through a pump assembly employing valve leak detection in accordance with the present invention;
FIC;URE 2 is an isometric view of a disposable pumping cassette and a portion of a pump driver used to drive the pumping cassette and to actuate valves in the cassette;
FIGURE 3 is a plan view of the cassette, with one side broken away to show its interior;
FIGURE 4 is a cross-sectional view of the cassette, taken along a section line 4-4 of FIGURE 3;
FIGURE 5 is a ~ross-sectional view of the cassette, taken along a section line j-5 of FIGURE 3;
FIGURE 6 is an elevational view of the pump driYe, showing the front of the device, with its door removed to better disclose its layout;
FIGURE 7 is a cross-sectional view o~ a portion of the pump drive front panel, taken along section line 7-7 of FIGURE 6, and showing the cassette in phantom view, where it is attached to the pump drive during operation of the pump assembly;
FIGURES 8A and 8B graphically represent ~he time sequence of operation of the pUllIp assembly during tests for leaks in the valves of the cassette;
FIGURES 9A, 9B, and 9C respectively illustrate the logic used for testing the input-output valves for leaks, primary and secondary valves ~or leaks using an air-in-line sensor, and tests of the primary and secondary valves for leakage using the pressure sensor; and -s -FIGURE 10 is an electrical schematica~ block disgr~m of a pump drive and leak test control employed in the pump assembly.
Description of the Preferred Embodiments A flow diagram for a pump apparatus used to administer liquids intravenously to a patient is shown schematically in FIGURE 1, identi~ied generally at reference numeral 20. Pump apparatus 20 is connected to selectivelypump a first fluid 22, which is supplied from a reservoir bag 24, or a second fluid 26, supplied from a reservoir bag 28. Both reservoir bags 24 and 28 are typically elevsted above pump apparatus 20, so that the first and second fluids freely flow downwardly toward the pump assembly; however, gravity flow is not required to prime the pump apparatus. Accordingly7 a supply line 30 connects reservoir bag 24 to a primary valve 34, and similarly, a supply line 32 connectsreservoir bag 28 to a secondary valve 36. Primary valve 34 and secondary valve 36 are both disposed within pump assembly 20 and are selectively controlled, as will be explained below, to permit either the first liquid or the second liquid to enter a manifold line 38, which connects both the primary and secondary valves to an air-in-line sensor 40.
A primary function of air-in-line sensor 40 is to detect the presence of air in either first fluid 22 or second fluid 26, to prevent air bubbles being deliveredintravenously to a patient, since such bubbles, if sufficient in volume, could result in a fatal air embolism. With respect to the present invention, air-in-line sensor 40 has a secondary function, since it is also used to determine if the primary or secondary valve is leaking or to detect leakage from the volume of fluid disposed between the air-in-line sensor and the primary and secondary valves, as explained in detail below.
Downstream of air-in-line sensor 40 is disposed an air trap reservoir 44, which normally serves to capture any air bubbles. Air trap reservoir 44 is connected to air-in-line sensor 40 by an inlet passage 42. Similarly, an inlet passage 46 connects the outlet of the air trap reservoir to an inlet valve 48. Inlet valve 48 selectively enables fluid flow into a pumping chamber 52 through a passage 50.
A passage 54 connects the outlet of pumping chamber ~2 to an outlet valve 56, which selectively controls fluid flow from pumping chamber 52, as described in greater detail below. Outlet valve 56 is connected through a delivery passage 58 to a pressure sensor 60. Pressure sensor 60 produces a signal indicative of the pressure of fluid within delivery passage 58, and is used in the present invention to detect leakage from the pump apparatus and to determine if inlet -6- ~ 9~

valve 48 or outlet v~lve 56 is leaking. The pressure sensor can nlso be used to determine whether primary valve 34 or secondary valve 36 is leaking. Pressure sensor 60 is connected through a delivery passage 62 to an air-in-line sensor 64.
Delivery passage 58 connects outlet valve 'i6 to air-in-line sensor 6~, which 5 performs only the function of deteeting sir bubbles in fluid delivered through a connected delivery tube 66, again to prevent air bubbles sufficient in volume topotentially cause an air embolism.
From FIGURE 1, it will be apparent that a leak in either primary valve 34 or seeondary valve 36 could permit either the first or second fluid, respectively, to 10 flow into manifold line 38 when the presence of fluid from the nonselected source is not desired. Such leakage could potentially cause a dangerous amount of a medieinal fluid to be injected into a patient if leakage of the primary or secondary seleetor valve should go undeteeted, as explained above. In addition, any leakage through inlet valve 48 or outlet valve 56 or from pump apparatus 20 eould either15 reduee the effeetive pumping rate of a medieinal fluid into a patient, or permit fluid flow through eonnected delivery tube 66 when pump apparatus 20 is supposedto be inoperative. Again, either eondition eould have potentially harmful effects if undeteeted.
FIGURES 2-5 illustrate a eassette 70, whieh eomprises the pump apparatus 20 deseribed above. A housing face of eassette 70 ineludes a flange 73 that extends around its perimeter and Pround eaeh of a plurality of eavities formed within a housing back 7~ of the eassette. Housing baek 74 also ineludes a flange around its perimeter, whieh sealingly eonnects to flange 73. Both a housing faee 72 and housing baek 74 are preferably molded from a rigid plastie sueh as polyearbonate25 or other suitable material. An elastomerie membrane 76 is positioned between housing faee 72 and housing baek 74 and is aecessible through eaeh of a plurality of ports formed in the housing faee. For example, elastomerie membrane 76 is exposed at a plunger port 78 that is defined within the housing faee. Behind theexposed portion e]astomerie membrane 76 and formed in housing baek 74 is 30 pumping ehamber 52. A plunger B0 is reeiproeatively driven in and out of plunger port 78, aetuating elastomeric membrane 76 so as to force fluid from pumping ehamber 52 through open outlet valve 56, when inlet valve 48 is closed.
Housing face 72 also includes a primary valve port 82 and a secondary valve port 84 through which extend actuator rods 86 and 88, respectively. A rounded 35 end on each of these actuator rods contacts elastomeric membrane 76, seleetively controlling fluid flo~v through primary valve 34 and secondary valve 36. Similarly, an inlet valve port 90 provides an opening for an actuator rod 92 to depress 2~ 2~`3~

elastomeric membrane 76 to control fluid flow through inlet valve 48, and an outlet valve port 94 serves a similar function wi~h respect to an actustor rod 96, to control fluid flow through outlet valve 56. A somewhat different function is provided by a pressure sensor port 98, which allows a pressure sensor rod 10D to5 contact elastomeric membrane 76. Pressure sensor rod 100 transmits fluid pressure from a cavity defining pressure sensor 60, formed in housing back 7~, to a strain gauge (not shown), which produces a signal indicative of fluid pressure.
Air-in-line sensors 40 and 64 e~tend outwardly from the outer surface of housing face 72. As shown in the cross section of FIGVRE 4, a finger 105 extends10 from housing back 74 into air-in-line sensor 40, and in conjunction with elastomeric membrane 76 defines inlet passage 42. On each side of air-in-line sensor 40, elastomeric membrane 76 bulges outwardly forming lobes 106.
Similarly, as shown in FIGURE 5, a finger 140 extends outwardly from housing back 74 into air-in-line sensor 64 to define delivery passage 62. Elastomeric 15 membrane 76 also includes lobes 106 at each side of air-in-line sensor 64. A pair of ultrasonic transducers 102 and 104 (shown in FIGURE 2) engage air-in-line sensors 40 and 64 so that a piezoelectric transmitter and piezoelectric receiver(neither shown) disposed at opposite sides of each transducer can come into contact with lobes 106. Elastomeric membrane 76 fits into a concave pocket 107 20 formed within housing îace 72 as shown in FIGURE 4, to provide an exposed passageway for engagement with ultrasonic transducer 102. An ultrasonic signal transmitted through the lobes determines the presence of an air bubble within the fluid passageway defined thereby.
Housing face 7~ is also provided with a flow control 108 comprising a 25 shaft 109 which is threaded into a projection 110. The end of shaft 109 engages elastomeric membrane 76, as shown in ~IGURE 5, to control fluid flow into delivery tube 66. Shaft 109 is threaded so that the flow control can be manuallyadjusted to set a desired flow rate for fluid into delivery tube 66 under gravity flow if a pump driver is not available. In addition, flow control 108 is normally set 30 to block fluid flow through delivery tube 66 when cassette 70 is not locked in place within a drive mechanism, to prevent undesired delivery of medicinal fluids to a patient. A mechanism for opening flow control 108 is disclosed in further detail herein below.
Housing back 74 includes a secondary inlet 112, which either has an in~ernal 35 luer taper 113, provided with locking flanges 114 for connection with an appropriate luer fitting (not shown), or includes a resilient reseal plug (not shown) that is punctured with a needle. A secondary inlet passage 11~ conveys fluid to an L82~

opening 118 formed within housing back 74. Elastomeric membrane 76 seals against housing back 74 immediately adjacent to opening 118 under the urging of actuator rod 88 to selectively stop fluid flow through openin~ 118.
Referring now to FIGURE 4, a primary inlet 119 defines an inlet passage 120 through which fluid flows to an opening 122 formed within housing back 74.
Immediately above openin~ 122 is disposed primary valve 34. The closure of primary valve 34 stops fluid flow through opening 122 from supply line 32. Fluidfrom secondary inlet 112 or primary inlet 119 flows through inlet passage 42 into air-in-line sensor 40, passes through the air-in-line sensor to a top reservoir inlet 124, and drips into air trap reservoir 44 as indicated by droplets 126. Air accumulates within a top section 128 of air trap reservoir 4~ as shown at 129.
Liquid accumulates in a bottom volume 132 of the reservoir, and flows through a bottom outlet 130 into inlet passage 46. If inlet valve 48 is open, fluid flows into the pumping chamber through a pumping chamber inlet 134. At the top of pumping chamber 52 is a pumping chamber outlet 136, disposed adjacent outlet valve 56. ~utlet valve 56 is closed when elastomeric membrane 76 is sealed against housing back 74 under the urging of actuator rod 96. However, during a normal pumping cycle, valve 5S opens and fluid is displaced from pumping chamber 52 as elastomeric membrane 76 is forced toward housing back 74 by plunger 80. Displacement of the fluid from a recess 135 that forms the back of the pumping chamber, increases the pressure of the fluid in a pressure sensor recess 138, which comprises pressure sensor 60. The displaced fluid is forced around finger 140, through a delivery passage 144 and out an outlet 142, which is connected to delivery tube 66. (See FIGURE 5.) Turning now to FIGURES 6 and 7, parts of a pump driver are shown which relate to the present invention. A pump driver 150 includes a face plate 152.
Cassette 70 is shown in phantom view in ~IGURE 7, illustrating how housing face 72 fits against face plate 152 of the pump driver, to enable engagement of flow control 108, to provide pumping action, and to effect actuation of the primary and secondary valves and inlet and outlet valves. Face plate 152 includes ultrasonic transducers 102 and 104, which are mounted at appropriate positions to fit over air-in-line sensors 40 and 64 of cassette 70 as previously disclosed with respect to FIGURE 2. A driver door pivot arm 154 is mounted to a pivot shaft 156on one side of face plate 152. Not shown in the drawing figures is a door to which driver door pivot arm 154 is attached, and which holds cassette 70 in place on face plate 152. The driver door connects to driver door pivot arm 154 causing the armto rotate pivot shaft 156 as cassette 70 is locked in place by closure of the driver door.

Face plate 152 includes a plurality of openings, including an opening 158 through which sctuator rod 92 extends, and an inverted key shape opening 160 throu~h which plunger 80 and actuator rod 96 extend. Openings 162, 16~, and 165 are provided for actuator rods 86, 88, and pressure sensor rod 100, respectively.
Behind face plate 152, pressure sensor rod 100 is connected to a pressure transducer 180. Each of the actuator rods ~6, 88, 92, and 96 are connected to levers actuated by motor driven cams (none of which are shown).
Also provided on face plate 152 is a flow control depressor 166, which comprises a portion of a flow shut-off assembly 167, shown in FIGURE 7. Shut-offassembly 167 includes two arms 168 (only one shown) and a cam 170, which is connected at one end of pivot shaft 156. Flow control depressor 166 is mounted within a bracket 172, which connects arms 168 on each side of the flow control depressor. Pins 174 (only one shown) extend outwardly from both sides of cam 170, each contacting the edge of one of the arms 168, so that rotation of cam 170 transmits force through the pins to move the arms. A spring 176 is connected between bracket 172 and flow control depressor 166, urging arms 168 away from flow control 108 when pins 174 permit such movement as a result of rotation of cam 170 in the opposite direction. Each time that cassette 70 is engaged with face plate 152, driver door pivot arm 154 rotates pivot shaft 156, causing cam 170 to rotate so that arms 168 engage flow control 108, forcing the flow control to its full open position. Conversely, as the driver door pivot armrotates to release cassette 70 from engagement with pump driver 150, cam 170 rotates pins 174 away from arms 168, and spring 176 causes arms 168 to pivot away from engagement with the flow control. As cam 170 continues to rotate, flow control depressor 166 is forced to pivot about a pivot shaft 178, engaging flow control 108 and forcing it to its fully closed position, just before cassette 70 is finally released from pump driver 150. As a consequence, fluid flow through cassette 70 under the force of gravity is blocked by flow control 108. After cassette 70 is removed from pump driver 150, flow control 108 can be manually adjusted to allow medicinal fluid to be administered to a patient at a controlled rate, if desired.
Since flow control 108 is forced to a full open position by shut-off assembly 167 when cassette 70 is mounted on pump driver 150, it is important that uncontrolled fluid flow through cassette 70 be prevented by some other mechanism. Accordingly, actuator rods 92 and 96 are mechanically interlocked so that at least one of the inlet and outlet valves is closed at all times that cassette 70 is mounted on pump driver 150. Since either inlet valve 48, or outlet 2~ 2~

valve 56, or both are closed Plt all times that cassette 70 is thus mounted, ~luid cAnnot flow through the cassette, except as a result of controlled pumping action involving the selective opening and closing of the inlet and outlet valves.
Pump driver 150 is controlled to effect a desired pumping rate of selected 5 medicinal fluids by a control 200, which is shown in a block diagram in FIGURE 10. Control 200 is also programmed to conduct leakage tests of the inlet and outlet valves and the primary and secondary valves in accordance with the present invention. An 8-bit microprocessor 202 in the control responds to programmed instructions stored in a read-only memory (ROM) and maintains 10 values temporaril~,- in a random access memory (RAM) as indicated by a memoryblock 20~, associated with microprocessor 202. A plurality of signal lines interconnect each of the other blocks shown in FIGURE 10 to microprocessor block 202 and memory block 204, in 8 manner well known by those of ordinary skill in the art. A key aspect of the present invention comprises output signals from 15 pressure sensor 60, and from the ultrasonic air-in-line sensor, collectively identified 8S a sensor block at reference numeral 208. In addition, a plurality of - optical mechanism position sensors 206, are connected to microprocessor 202 for monitoring the operation of pump driver 150. Since the optical mechanism position sensors are not particularly relevant to the subject matter of the present ~O invention, details concerning their function and structure are omitted herein.
Also connected to microprocessor 2û2 are three stepping motors 210, which effectoperation of plunger 80 and actuator rods ~6, 88, 92 and 96 for the primary and secondary valves and the inlet and outlet valves, respectively.
Microprocessor 202 thus controls the plunger and each of the valves in 25 cassette 70 according to preprogrammed instructions, and consistent with input data provided the microprocessor from a keyboard 216. The operator enters data such as the pumping rate desired in response to prompts created on a display 218, which includes both a liquid crystal display (LCD) and light emitting diodes (LEDs). Power supplies 212 provide appropriate voltages at necessary current 30 levels to each of the active components in control 200 and include a battery charger to maintain a backup battery (not separately shown) in the event that power is interrupted from an AC line source. A data way 220 is provided on control 200 to enable bi-directional data exchange with an external device, for example, a printer. Where appropriate, microprocessor 202 can initiate a nurse 35 call as shown by a block 222, to summon help in the event that action by medical personnel is required. In addition, control 200 includes an alarm 214, which maycomprise both visual and audible signals, energized when emergency conditions are detected, such as a leak in one of the primary, secondary, inlet, or outlet valves.

-11- 2~ 9~

Stored in ROM within memory block 204 are the leAk detection al~orithms implemented by microprocessor 202. The logic implemented in these algorithms is shown in a flow chart in FIGURES 9A-9C. Timing for the valve leakage tests (and other operations of pump apparatus 20), are shown in FIGURES 8A and 8B.
5 Reference to the timing charts assists in understanding the valve integrity test logic shown in the flow charts. The first leakage test performed in cassette 70 after start-up uses the logic illustrated in FIGURE 9A to determine whether inlet valve 48 or outlet valve 56 (or the portion of cassette 70 defining the fluid volume between these two valves) is leaking. The left sides of both FIGURE 8A or BEi 10 corresponds to the timing for determining leakage of fluid nominally trapped between the inlet and outlet valves, while the right sides of the figures show two different methods for determining leakage of fluid nominally trapped between theprimary and secondary valves and the outlet valve. In the timing chart, FIGURE 8A, a line 350 ~top line in the timing chart) illustrates the relative 15 position of plunger 80, the lowest vertical points along line 350 indicating the position of the plunger when it is fully withdrawn, and the highest vertical points along the line representing the fully extended stroke position of plunger 80, which displaces fluid from pumping chamber 52.
A line 352 indicates the condition of inlet valve 48 and ouUet valve 56, the 20 center vertical position along line 352 indicating that both valves are closed, the highest vertical position indicating that outlet valve 56 is closed and inlet valve 48 is open, and the lowest vertical position indicating that the outlet valve is open while the inlet valve is closed. The condition of primary and secondary valves are similarly shown by a line 354, wherein the center vertical elevation of the line25 indicates that both valves are closed, the highest vertical ~oints on the line indicate the primary valve is open, and the lowest indicating that the secondaryvalve is open.
The signal produced by pressure sensor 60 is shown on a line 356, wherein a positive spike indicates a pressure pulse detected at the point where pressure 30 sensor 60 is disposed, downstream of pumping chamber 52 and outlet valve 56, due to a pressurized fluid wave propagating downstream of the outlet valve. A
line 358 generally indicates the cycle that is being implemented. For example, on the left side of line 358, a motor synchronization cycle is implemented to ensure that the valves and plunger motor are properly synchronized. A check of the inlet 35 and outlet valve leak integrity follows the motor synchronization cycle, beginning with an operator depressing a start button (not shown) on keyboard 216. This check also detects leakage of cassette 70 due to failure of the seal between elastomeric membrane 76 and housing back 74, e.g., around pumping chamber 52.

As shown in FICURE 9A, the algorithm begins with the start initiated in a block 250 and proceeds to a block 252 wherein casse~te 70 is primed with f]uid (either the primary or secondary) that is to be delivered to the patient. To prime cassette 70 with primary fluid, pumping chamber 52 may be filled by gravity feed5 prior to installation in the drive unit, or by pumping air from the cassette before the IV line is connected to the patient. As shown by line 350 (FIGURE 8A) after the priming operation, plunger 80 is initially fully withdra~n from pumping chamber 52. In a block 254, both the inlet and outlet valves are closed so that fluid is trapped within pumping chamber 52 between the two valves. In a 10 bloclc 256, p]unger 80 is advanced by five steps of the stepping motor that drives it, which corresponds to a holding pressure in pumping chamber 52 of approximately 10 psi. This pressure is held for a period o~ time ranging betweentwo and ten seconds, as a function of the programmed delivery rate for the fluid, as shown in Table 1 below. For a pumping rate less than 130 ml per hour, a 15 maximum of ten seconds holding time is provided; however, for rates between 130 and 1,000 mls per hour, the holding time corresponds to a leakage equal to approximately 5% of the pumping rate.

I /O VALVE
RATE HOLD T IME
m l/hr T1 (SECONDS

Up to 120.0 10.0 Up to 130.0 9.0 Up to 150.0 8.0 25 Up to 100.0 7.0 Up to 210.0 6.0 Up to 2~0.0 5.0 Up to 360.0 4.0 Up to 540.0 3.0 Up to 99~.0 2.0 At the end of the time interval indicated as T1, in blocks 258 and 260, outlet valve 56 is opened, while inlet valve 48 remains closed. When outlet valve 56 isopened, a dynamic pressure pulse propagates through delivery passage 58, downstream of outlet valve 56, and is sensed by pressure sensors 60. The amplitude of the pressure pulse should exceed a predetermined minimum, unless `
35 either (or both) the inlet or outlet valve or the cassette has leaked during the holding period, T1. In a block 262, microprocessor 202 determines if the pressure - 1 3~ L8~

pulse is equal or greater than a predetermined value, Pm jn, and if so, the software logic proceeds to a block 264, to continue at the top of FICURE 9B, wherein the primary and secondary valve are checked for leakage.
Assuming that the pressure pulse is less than Pm jn in block 262, a block 266 5 determines if there has been a previous test of the inlet and outlet valve leak integrity, ~nd if not, the logic proceeds back to repeat the inlet/outlet (I/O) valve leak test, starting with block 254. Alternatively, if the pressure pulse is less than or equal to Pmin in a second test, the logic proceeds to a block 268, wherein analarm is effected, comprising either an audibie or visual signal to alert the 10 operator that excessive leakage has been detected. While determination of l/Ovalve or cassette 70 leakage only depends on the results of two such tests in the preferred embodiment, it may be made to depend on the results of more than two consecutive tests. Line 350 shows that at the conclusion of the l/O valve leak test, assuming that the valves and cassette are not leaking, fluid is delivered 15 through the open outlet valve by completion of the plunger stroke.
In the portion of the flow chart shown in FIGURE 9B, a first preferred method for testing the primary and secondary valves for leakage uses the signal output from air-in-line sensor 40. This test also detects leakage from the fluidpassages of cassette lO that are between air-in-line sensor 40 and the primary and 20 secondary valves. Following the completion of the delivery stroke at the end of the inlet/outlet valve leak test cycle, the outlet valve closes and the inlet valve opens so that as plunger 80 pulls back to its fully retracted position, fluid again fills pumping chamber 52, as indicated in a block 280 in the flow chart. In a block 282, the logic determines if a value designated "Air Trp" is less than a value 25 "Air Trg". These values are determined from a previous test of the primary and secondary valves, if one was made. If such a test had not previously been made, or if the results were posit,ve, the logic proceeds to a block 284, wherein a counter having the count Air Trp, indicative of the amount of air trapped in theair trap reservoir is cleared, i.e., set equal to zero. Then, in a block 28~, 30 plunger 80 performs a pushback as the stepping motor that drives it advances through twenty steps. Fluid is forced from pumping chamber 52 in retrograde direction, through the open inlet valve, displacing fluid within the air trap reservoir 44. Any air within air trap reservoir 44 is thus forced back through air-in-line sensor 40 during the pushback operation. Thereafter, microprocessor 202 35 waits for approximately 100 milliseconds for settling to occur and retracts plunger 80 by twenty steps of its stepping motor, placing it back to its fully retracted position. With each step that plunger 80 is retracted, microprocessor 202 checks to see if the signal output from air-in-line sensor 40corresponds to the presence of air or liquid, and accumulates the number of suchsteps durin~ which the air-in-line sensor detects air. The total step count for air within air trap reservoir 44 can range between zero and twenty, depending upon 5 the number of steps of the stepping motor during which air was detected withinair-in-line sensor 40. This operation of the algorithm is referenced in a block 288. (If no liquid is present in the air trap reservoir, a plurality of pumping cycles are initiated to draw liquid into cassette 70 and the pushback operation is repeated.) Subsequently, in a block 290, if the air count is greater than or eq~lal to a predetermined value, preferably four in the preferred embodiment. sufficient airis detected to perform a primary/secondary valve leak test using the air-in-linesensor. This affirmative response to the question posed in block 290 causes the logic to proceed to a block 292 to perform the leak test using the air-in-line 15 sensor. An air count equal to four corresponds to approximately 16 microliters of air within the air trap reservoir in the preferred embodiment. However, before initiating the leak test using air-in-line sensor 40, liquid must be detected within the air-in-line sensor. To perform the leak test using the air-in-line sensor, both primary and secondary valves are closed; inlet valve 48 remains open and outlet 20 valve 5O closed. Microprocessor 202 causes plunger 80 to advance, pressurizing fluid within pumping chamber 52 and other internal passages of cassette 70, backthrough air-in-line sensor 40. If during a period of time, T2, which is determined in accord with the programmed pumping rate as shown in Table 2 below, the signaloutput from air-in-line sensor has not changed from indicating that liquid is 25 present to indicating that air has entered inlet passage 42, then neither theprimary nor secondary valve has leaked and fluid has not leaked from cassette 70upstream of air-in-line sensor 40. An inquiry in a block 294 to determine whether the primary and secondary valves (and cassette 70) have passed the test may be answered in the affirmative. With an affirmative answer, the logic proceeds to a30 block 296 to begin the normal pumping cycle. Alternatively, if air is detected within air-in-line sensor 40 during the T2 holding period, the logic returns to block 280, following a full stroke by plunger 80, to provide for another intake stroke .

PRIM~RY/SEC. VALVE
RATE HOLD Tl IU E
~I/hr T2 (sEcoND
Up to 100.0 15.0 Up to 1 1 0.0 1 3.0 Upto 120.0 12.0 Up to 140.0 11.0 Up to 150.0 10.0 Up to 170.0 9.0 Up to 200.0 8.0 Up to 230.0 7.0 1O Up to 280.0 6.0 Up to 350.0 5.0 Up to 460.0 4.0 Up to 700.0 3.0 Up to 999.0 2.0 As shown in Table 2, the hold time ranges from a ma~cimum fifteen seconds 15 for a pumping rate up to 100 mililiters per hour to two seconds ~or a pumping rate of about 1000 mill}liters per hour. For all pumping rates in excess of 100 milliliters per hour, the hold time corresponds to a maximum allowed leakageequivalent to approximately 10% of the pumping rate (for the preferred embodiment of cassette 70). With respect both to Table 1 and Table 2, different ~ holding times may be provided within the algorithm, to a~commodate msximum allowed leakages equal to a different percentage of the pumping rate.
Referring back to the flow chart in FIGURE 9B, if the answer to the inquiry in block 294 is negative, a block 312 determines whether the test has failed a predetermined number, F, times and if so issues an alarm in a block 314. If not, 25 the test is repeated, starting with block 280. In block 290, if insu~ficient air is present to perform the test for leakage in primary and secondary valves 34 and 36, respectively, the logic reverts to a block 300, to initiate the test using pressure sensor 60. Tests of the primary and secondary valves using pressure sensor are shown in FIGURE 9C, described below. Following the test of the primary and 30 secondary val-.~es using the pressure sensor, a block 302 determines if the test was passed, and, if so, the logic continues to block 296, where it exits to begin a normal pumping cycle. Alternatively, in a block 304, the test of the primary andsecondary valves using the pressure sensor is repeated, by advancing plunger 80 through fifteen more steps of its stepping motor. In a block 306 the leak test is 35 repeated as shown in FIGURE 9C, using pressure sensor 60. In a block 308, if the test was passed, the logic proceeds again to block 296; otherwise, the logic proceeds to a block 310 to issue an alarm.

9~i FIGURE 9C and the timing diagrams in FIGURE 8B illustrate the logic used to test primary valve 34 and secondary valve 36 and the portion of cassette 70 between these two valves and outlet valve 56 for leakage integrity as a functionof the signal output from the pressure sensor 60. This test is similar to that used to test the leakage integrity of inlet valve 48 and outlet valve 56. Logic in FIGURE 9C starts with a block 320, entered as provided in blocks 300 snd 306 of FI~VRE 9B. From block 320, the logic proceeds to a block 322 in which the primary and secondary valves are closed. Next, inlet valve 48 and outlet valve 56 are toggled between their opened and closed conditions through an intermediate position in which they are both closed (preferably at least six times) to equalize internal pressure within cassette 70. At the conclusion of the toggling operation in a block 324, the inlet and outlet valves satisfy the condition in a block 326, i.e., outlet valve 56 is closed and inlet va~ve 48 is open. Plunger 80 is then advanced twenty steps of its stepper motor in a block 328, pressurizing fluid within pumping chamber 52 and in the internal passages of cassette 70, all the way back to bothprimary valve 34 and secondary valve 36. In a block 330, microprocessor 202 waits for a period of time equal to two to fifteen seconds, again depending uponthe delivery rate programmed by the user (see Table 2). Finally, in blocks 332 and 334, inlet valve 48 is closed and outlet valve 56 is opened. If a pressure pulse with an amplitude greater than or egual to a predetermined value, Pmin is detected propagating through the iluid downstream of outlet valve 56 by pressuresensor 60, a block 336 determines that neither the primary rlor seconda~y valvesnor cassette 70 are leaking. (~learly, if fluid is leaking through either of these valves, or from the volume of fluid nominally trapped between the primary and secondary valves and the outlet valve, the pressure of îluid trapped in pumping chamber 52 is reduced, so that when the outlet valve is open, the amplitude of the pressure pulse that propagates to pressure sensor 60 is significantly reduced.
Assuming that neither the primary and secondary valves nor cassette 70 have leaked during the preceding test, in a block 338, the logic initiates the normalpumping cycle. Upon failure to pass the leak test in block 336, the logic proceeds to a block 340, which determines if this is the second time the test has failed, and, if so, issues an alarm in a block 3~1. Otherwise, logic proceeds to a block 342 in which the outlet valve is closed and the inlet valve opened. In a block 344, theplunger advances fifteen more steps before proceeding to block 330, where the pressure is again held for the predetermined time period, T2. Blocks 340, 342, and 344 in FIGURE 9C thus correspond to blocks 308, 310, and 304 in FIGURE 9B.

~8~2~

lt will be apparent that the primary snd secondary valves and cassette 70 could be tested for leakage using only pressure sensor 60, without using the air-in-line sensor method. However, the air-in-line sensor method is more sensitive in determining leakage through the primary and secondary valves thsn is the method 5 using pressure sensor 60 if air is present in the cassette. However, if little or no air is present in the cassette, the test using the pressure sensor is preferred.Furthermore, leakage tests of the primary and secondary valves using the air-in-line sensor are independent of tests for leakage integrity of the inlet and outlet valves. However, leakage of the inlet or outlet valves or of cassette 70 will 10 affect the results of leakage tests on the primary secondary valves using pressure sensor 60. For this reason, it is best to determine that the volume of fluid trapped between the inlet and outlet valves is not leaking before testing the leakage integrity of the primary and secondary Yalves and the remainder of cassette 70, particularly if the pressure sensor method is used.
While the present invention has been disclosed with respect to preferred embodiments, those of ordinary skill in the art will understand that further modifications thereto may be made within the scope of the claims that follow below. Accordingly, it is not in~ended that the invention in any way be limited by the disclosure, but instead that it be determined entirely by reference to the 20 claims.

Claims

1. A pump assembly having the capacity to self test for leakage, comprising:
a) a pumping chamber in which a fluid is pressurized during a pumping cycle;
b) an inlet valve that periodically interrupts fluid flow into and out of the pumping chamber, with respect to a source of the fluid disposed upstream of the inlet valve;
c) an outlet valve that periodically interrupts fluid flow into and out of the pumping chamber, with respect to a delivery passage through which pressurized fluid flows when the pump assembly is operating to pump the fluid;
d) a pressure sensor, disposed downstream of the outlet valve and operative to sense the pressure of the fluid and to produce a signal indicative of that pressure; and e) control means for controlling the pumping cycle, including self test means connected to receive the signal produced by the pressure sensor for:
i) filling the pumping chamber with the fluid;
ii) closing the inlet and the outlet valves;
iii) effecting at least a partial pumping cycle to pressurize fluid in the pumping chamber;
iv) after a predetermined time interval, opening the outlet valve; and v) determining whether the pump assembly has leaked during the predetermined time interval, as a function of the signal produced by the pressure sensor after the outlet valve is opened.

2. The pump assembly of Claim 1, wherein said signal produced by the pressure sensor is indicative of a pressure pulse caused by propagation of a pressurized fluid wave down the delivery passage from the pressure chamber when the outlet valve is opened.

3. The pump assembly of Claim 2, wherein unacceptable leakage from a volume of fluid nominally trapped between the inlet and outlet valves during thepredetermined time interval is detected by the self test means if the maximum magnitude of the pressure pulse is less than a predetermined value.

4. The pump assembly of Claim 1, wherein the control means are further operative to effect an alarm if the self test means determine that the pump assembly has leaked during the predetermined time interval.

5. The pump assembly of Claim 4, wherein the self test means are operative to repetitively test for fluid leakage, and to determine that the pumpassembly is leaking only if a predetermined number of such tests indicate leakage.

6. The pump assembly of Claim 1, further comprising selector valve means, disposed upstream of the inlet valve and connected in fluid communicationtherewith by an inlet passage, for selecting at least one inlet port from among a plurality of inlet ports on the pump assembly for connection to the source supplying the fluid to the inlet valve and pumping chamber.

7. The pump assembly of Claim 6, wherein the self test means are further operative to detect leakage by:
a) filling the inlet passage and pumping chamber with fluid;
b) closing the selector valve means and the outlet valve;
c) effecting at least a partial pumping cycle to pressurize fluid in the inlet passage and in the pumping chamber;
d) after a second predetermined time interval, closing the inlet valve and then opening the outlet valve; and e) determining whether the pump assembly has leaked during the second predetermined time interval, as a function of the signal produced by the pressure sensor after the outlet valve is opened.

8. The pump assembly of Claim 7, wherein said signal produced by the pressure sensor is indicative of a pressure pulse caused by propagation of a pressurized fluid wave down the delivery passage from the pressure chamber when the outlet valve is opened.

9. The pump assembly of Claim 8, wherein unacceptable leakage from a volume of fluid nominally trapped between the selector valve means and the inletvalve during the second predetermined time interval is detected by the self testmeans if the maximum magnitude of the pressure pulse is less than a predetermined value.

10. The pump assembly of Claim 6, further comprising an air trap reservoir disposed on the inlet passage, and an air-in-line sensor disposed in the inlet passage between the air trap reservoir and the selector valve means, said air-in-line sensor being operative to produce a signal indicative of the presence of air in the inlet passage where said air-in-line sensor is disposed and being connected to provide that signal to the self-test means.

11. The pump assembly of Claim 10, wherein the self test means are further operative to alternatively determine whether unacceptable leakage from avolume of fluid nominally trapped between the selector valve means and the outlet valve has occurred, if air is trapped in the air trap reservoir, by:
a) filling the inlet passage and pumping chamber with a liquid;
b) closing the selector valve means and the outlet valve;
c) effecting at least a partial pumping cycle to pressurize the liquid in the pumping chamber and in the inlet passage; and d) determining whether the selector valve means are leaking as a function of the signal produced by the air-in-line sensor.

12. The pump assembly of Claim 11, wherein a change in the signal produced by the air-in-line sensor indicating the presence of air flowing from the air trap reservoir into the inlet passage where the air-in-line sensor is located, after said at least partial pumping cycle is initiated is determinative of a leak in the pump assembly.

13. The pump assembly of Claim 11, wherein the self test means are further operative to effect a plurality of pumping cycles before closing the selector valve means and the outlet valve, in order to clear any air initially present in the inlet passage where the air-in-line sensor is disposed.

14. The pump assembly of Claim 11, wherein the self test means are operative to determine whether the pump assembly is leaking as a function of thesignal produced by the air-in-line sensor only if the air trap reservoir initially contains a substantial quantity of air, part of which is forced into the air-in-line sensor if fluid leaks from the pump assembly upstream of the air-in-line sensor when the liquid in the inlet passage is pressurized.

15. In a pump assembly having a plurality of valves, including an inlet valve and an outlet valve, a pumping chamber disposed between the inlet valve and outlet valve, and a control that selectively opens and closes the inlet and outlet valves and activates a driver to pressurize a fluid within the pumping chamber in a pump cycle, apparatus to test for leakage of the pump assembly, comprising:
pressure sensing means for producing a signal indicative of the pressure of fluid in a fluid passage downstream of the outlet valve; and leak detection means, connected to receive the signal produced by the pressure sensing means, for detecting leakage from the pump assembly as a function of the signal produced by the pressure sensing means immediately after the outlet valve is opened, said outlet valve being opened after fluid within the pumping chamber has been pressurized for an interval of time.

16. The apparatus of Claim 15, wherein leakage is detected by the leak detection means if the signal produced by the pressure sensing means indicates that a peak pressure of a pulse propagating through the fluid passage when the outlet valve is opened is less than a predetermined value.

17. The apparatus of Claim 15, wherein the plurality of valves further include selector valve means for selecting from among a plurality of inlets to the pump assembly a source of fluid for input to the pumping chamber as determined by the control means, said selector valve means being connected in fluid communication with the inlet valve by an inlet passage.

18. The apparatus of Claim 17, further comprising an air trap reservoir and air-in-line sensor means, both disposed in the inlet passage, for detecting the presence of air/liquid upstream of the air trap reservoir and producing a signalindicating whether air or liquid is present in the inlet passage at the air-in-line sensor means, wherein the leak detection means are alternatively operative to detect leakage through the selector valve means as a function of the signal produced by the air-in-line sensor means when both the selector valve means and the outlet valve are closed if substantial air is initially present in the air trap reservoir, and if not, to detect leakage through the selector valve means as a function of the signal produced by the pressure sensor means when the outlet valve is opened, releasing pressurized liquid from the pumping chamber, said liquid having been initially trapped between the selector valve means and the outlet valve when initially pressurized.

19. The apparatus of Claim 18, wherein the leak detection means determines that the selector valve means are leaking as a function of the signalproduced by the air-in-line sensor means if, during pressurization of liquid in the pumping chamber, said air-in-line sensor means begin to indicate the presence ofair rather than liquid.

20. In a pump assembly having a plurality of valves, including an outlet valve and a primary valve, a pumping chamber disposed between the primary valve and outlet valve, and a control that selectively opens and closes the primary valve and outlet valve and activates a driver to pressurize a liquid within the pumping chamber in a pump cycle, apparatus to test for leakage of the pump assembly, comprising:
a) an air trap reservoir disposed on an inlet passage connecting the primary valve in fluid communication with the pumping chamber;
b) air-in-line sensor means for detecting the presence of air/liquid in the inlet passage at a point that is upstream of the air trap reservoir and downstream of the primary and secondary selector valves and producing a signal indicative of whether air or liquid is present at said point; and c) leak detection means, connected to receive the signal produced by the air-in-line sensor means, for detecting leakage when a substantial quantity of air is initially present in the air trap reservoir, by:
i) filling the pumping chamber and inlet passage with liquid so that the signal produced by the air-in-line sensor means indicates thepresence of liquid at said point;
ii) closing the outlet valve and the primary valve;
iii) effecting at least a partial pumping cycle to pressurize liquid in the pumping chamber and in the inlet passage; and iv) determining whether the pump assembly valve is leaking as a function of the signal produced by the air-in-line sensor changing to indicate the presence of air at said point in the inlet passage.

21 . The apparatus of Claim 20, further comprising pressure sensing means for sensing the pressure of liquid in a fluid passage downstream of the outlet valve, producing a signal indicative of that pressure, and an inlet valve disposed upstream of the pumping chamber, wherein if a substantial quantity of air is notpresent in the air trap reservoir, said leak detection means are operative to detect a leak by:
i) filling the pumping chamber and inlet passage with liquid;
ii) closing the outlet valve and the primary valve;
iii) effecting at least a partial pumping cycle to pressurize liquid in the pumping chamber and in the inlet passage;
iv) closing the inlet valve;
v) opening the outlet valve; and vi) determining the pump assembly is leaking as a function of the signal produced by the pressure sensing means after the outlet valve is opened.