Abstract:
A medical fluid pneumatic manifold system includes a plurality of pump and valve chambers for controlling a flow of medical fluid, a header including a plurality of pneumatic passageways, each passageway in pneumatic communication with one of the pump or valve chambers, a plurality of electrically actuated pneumatic valves, and a plate defining a plurality of pneumatic apertures, wherein the header and the plurality of electrically actuated pneumatic valves are separately attached to the plate, such that each pneumatic aperture in the plate is placed in pneumatic communication with one of the plurality of pneumatic passageways of the header and one of the electrically actuated pneumatic valves.

Description:
PRIORITY 
     This application claims priority to and the benefit as a continuation of U.S. patent application Ser. No. 13/919,297, filed Jun. 17, 2013, entitled, “Pressure Manifold System for Dialysis, which is a continuation of U.S. patent application Ser. No. 13/047,203, filed Mar. 14, 2011, now U.S. Pat. No. 8,465,446, entitled, “Noise-Reducing Dialysis Systems And Methods Of Reducing Noise In Dialysis Systems”, which is a divisional application of U.S. patent application Ser. No. 11/929,330, filed Oct. 30, 2007, now U.S. Pat. No. 7,905,853, entitled, “Dialysis System Having Integrated Pneumatic Manifold”, the entire contents of each of which are incorporated herein by reference and relied upon. 
    
    
     BACKGROUND 
     The present disclosure relates generally to a medical fluid delivery system and in particular to a dialysis system. U.S. Pat. No. 5,350,357, the entire contents of which are incorporated herein by reference, shows a peritoneal dialysis machine  10  having housing  12 . Housing  12  holds a bag heater module  14  located under a bag heating plate  16 . Housing  12  further encloses a pneumatic actuator module  20 . Pneumatic actuator module  20  incorporates a cassette holder  22  that holds a disposable dialysis cassette (not illustrated) and a liquid shutoff assembly  24 . Machine housing  12  further encloses a source  30  of pneumatic pressure and an associated pneumatic pressure distribution module  40 , which links the pressure source  30  with the actuator module  20 . Pressure distribution module  40  stores positive pressure in reservoir  32  and negative pressure in reservoir  34 . Machine housing  12  also encloses an AC power supply module  36  and a back-up DC battery power supply module  38  to power machine  10 . 
     Tubing  42  connects pneumatic valves located on pressure distribution module  40  to the machine components that operate using pneumatic pressure. Slots  44  in the side of the pressure distribution module  40  accommodate the passage of the tubing  42 . In particular, tubing  42  runs from pressure distribution module  40  to actuator module  20 , where the tubing connects to components such as a cassette sealing bladder (not illustrated), an occluder bladder for liquid shutoff assembly  24  and to pump and valve actuators that control the application of positive and negative pressure to different areas of the disposable cassette. 
     Each of the tubes  42  has to be disconnected individually to remove either pressure distribution module  40  to actuator module  20  from machine  10 . Tubes  42  are not easy to disconnect. Tubing  42  often stretches and becomes unusable when pulled off the barbed fittings connected to pressure distribution module  40 . The barbed fittings themselves can be damaged if an attempt is made to cut tubes  42  off the fittings. 
       FIG. 2  shows pressure distribution module  40  exploded. Pressure distribution module  40  includes a printed circuit board  46  which is carried on stand-off pins  48  atop the pressure distribution module. Pressure transducers  50  mounted on printed circuit board  46  of module  40  sense through associated sensing tubes  52  pneumatic pressure conditions present at various points along the air conduction channels (not illustrated) within pressure distribution module  40 . Pressure transducers  50  and/or the solder joint that connect the pressure transducers to the printed circuit board  46  can be damaged if an attempt is made to disconnect the tubes between the manifold and the pressure transducers. 
     Attempts to detach the tubing from actuator module  20  also encounter problems.  FIG. 3  shows a cassette interface  26 , which is located inside actuator module  20 . T-fittings  28  connect the tubing  42  to the ports of the valve actuators and pump actuators. Thus to remove actuator module  20  from pressure distribution module  40 , cassette interface  26  has to be accessed first and then T-fittings  28  have to be removed from cassette interface  26 . 
     A need therefore exists for a dialysis machine that is more readily repaired and maintained. 
     SUMMARY 
     The present disclosure relates to an integrated pneumatic manifold with direct mounted or encapsulated parts that eliminate the need for certain tubes or hoses. The manifold can be used in medical fluid delivery treatments, such as any type of dialysis treatment or machine, e.g., one operating on pneumatic pressure. The manifold can incorporate other pneumatic components besides valves, such as one or more storage reservoir, a pressure pump and a manual diverter valve for calibration standard connection. 
     The manifold in one embodiment includes a printed circuit board (“PCB”) with pneumatic valve drives. The manifold also has easily removable port headers with multiple tubing connections for tubes leading to other subsystems. Valves attached to the PCB communicate with the ports of the header via pneumatic traces or grooves formed in the plate to which the PCB and headers are mounted. The PCB containing the valve drivers also includes a spike and hold circuit in one embodiment that minimizes the holding current required when the valves remain energized for more than a certain period of time, e.g., about 0.1 seconds. 
     The air pump is mounted in one embodiment to a lower manifold plate, which serves as a heat sink for the air pump motor. The lower plate can therefore be made of a light, thermally conductive material, such as aluminum. The lower plate attaches to the upper plate holding the PCB, valves and headers via a gasket between the plates. The gasket seals the pneumatic pathways or grooves formed on the underside of the upper plate. 
     The port headers allow the manifold assembly to be detached easily from the dialysis machine, e.g., from a door assembly and electronics in the machine to which the ports and PCB are connected respectively. Any of the manifold subassembly, door subassembly or control board subassembly can be removed and replaced without having to (i) replace any of the interconnecting tubing or (ii) remove any other machine subassembly. The potential to damage any of the interconnecting components is accordingly minimized. For example, tubing does not have to be detached from barbed ports fittings, which otherwise can potentially damage the fitting in addition to destroying the tubing. 
     A filter that prevents particles from entering the manifold is also integrated into the manifold. In a one embodiment, the filter is a flat filter element that is sandwiched between the upper and lower plates of the manifold. As mentioned, pneumatic reservoirs (shown above as stand-alone positive and negative pressure source tanks  32  and  34 ) are also integrated into the manifold in one embodiment. Many of the header ports to the valves connect directly into the reservoirs. Pressure transducers can also connect directly into the reservoirs and are thereby unaffected by the transient dynamic conditions that occur in the pneumatic tubing when the system is operating. The manual diverter valve connected to the assembly allows an external pressure standard to be connected to the manifold during calibration to calibrate the pressure transducers. 
     The manifold assembly works in a pneumatic system to operate a medical fluid system such as a dialysis system. The manifold, for example, can deliver positive or negative air to dialysis fluid pump and valve actuators. The actuators actuate pump and valve chambers located on a disposable fluid cassette. The cassette needs to be sealed to a cassette interface (e.g., shown above as interface  26 ). In one embodiment therefore the manifold assembly also provides pressure to a bladder that presses the cassette against the cassette interface for operation. Tubes connected to the cassette receive dialysis fluid, carry fresh dialysis fluid to the patient, and carry spent dialysis fluid from the patient to drain. When the machine is not in use or in the event that the machine loses power, the tubes are crimped closed via a spring-loaded occluder that crimps the tubing unless otherwise acted upon. In one embodiment, the manifold assembly pressurizes a second bladder, which operates to retract the occluder to uncrimp or open the tubing. 
     In the pneumatic system of the present disclosure, the air pump pressurizes four separate tanks, namely, the positive and negative reservoirs located on the manifold assembly, the cassette sealing bladder and the occluder bladder. The pneumatic configurations shown below include apparatuses that allow the air pump to pressurize each of the tanks and bladders individually so that one does not “steal” pressure or air from another during operation of the machine. For example, the air pump located on the manifold assembly in one embodiment includes dual pump heads, which can be dedicated to pumping positive and negative pressure, respectively, to the positive and negative reservoirs. Indeed, the pump can pump to the positive and negative reservoirs simultaneously. This has been found to have the added benefit of halving the pump output to each reservoir, reducing noise. 
     The pneumatic system isolates the reservoirs from the bladders and the bladders from each other using valves. To conserve the number of valves, the system in one embodiment uses a three-way valve to supply pressurized air to either a positive pressure tank for operating the fluid pumps or to a line that supplies a cassette sealing bladder and a tubing pumping occluder bladder. Also, to conserve the number of solenoid valves needed, the system in one embodiment places a check valve in a split in a line that supplies pressure to the cassette sealing bladder and occluder bladders, such that the occluder bladder cannot steal positive pressure from the cassette sealing bladder. A drop in the cassette sealing bladder pressure can compromise the seal of the dialysis pumping cassette relative to the dialysis instrument. 
     It is accordingly an advantage of the present disclosure to provide a pneumatic manifold assembly having improved reliability, ease of assembly and serviceability while being backwards compatible with existing systems. 
     It is another advantage of the present disclosure to provide a pneumatic manifold assembly that integrates the air pump, heat sinks the air pump and places the air pump inside a sealed enclosure to minimize the noise without overheating the pump and valves. 
     It is a further advantage of the present disclosure to mitigate dialysis instrument noise. 
     It is still another advantage of the present disclosure to provide a valve manifold assembly configured to isolate two separate sealing bladders pressurized via the manifold assembly. 
     It is yet a further advantage of the present disclosure to provide a robust pneumatic system in which pneumatic storage tanks and bladders are pneumatically isolated form one another. 
     Additional features and advantages are described herein, and will be apparent from, the following Detailed Description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS. 1 to 3  are various perspective views of a prior art peritoneal dialysis machine and in particular to a pneumatic system of the machine. 
         FIG. 4  is a perspective view of one embodiment of a pressure manifold assembly of the present disclosure. 
         FIG. 5  is another perspective view of the pressure manifold assembly of  FIG. 4 . 
         FIG. 6  illustrates one embodiment of a pressure manifold plate having pneumatic passageways, the plate operable with the pressure manifold assembly of the present disclosure. 
         FIG. 7  is a perspective view of the underside of top plate  102  from the pressure manifold assembly of  FIG. 4 . 
         FIG. 8  is an exploded perspective view of a lower portion of the pressure manifold assembly of  FIG. 4 . 
         FIGS. 9A to 9D  are perspective views of an alternative pressure manifold assembly of the present disclosure. 
         FIGS. 10 and 11  are schematic views of various pneumatic configurations for the pressure manifold assembly and other pneumatic components of the present disclosure. 
         FIGS. 12 and 13  illustrate one embodiment of a noise reduction circuit operable with the pneumatic pump of the pressure manifold assemblies of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Pneumatic Hardware Configurations 
     Referring now to the drawings and in particular to  FIGS. 4 to 8 , pressure manifold assembly  100  illustrates one embodiment of the present disclosure. Assembly  100  includes a top plate  102 , a bottom valve plate  104  and a gasket  106  sandwiched between top plate  102  and bottom valve plate  104 . Top plate  102  can be made of aluminum or other lightweight material that can be threaded or fitted with threaded inserts. 
     Manifold assembly  100  includes a first header  108 , which is attached to manifold top plate  102  in a sealed manner using o-ring seals  110  and screws  112 . O-Ring seals  110  provide a leak tight connection between all of the internal passageways  134  (see  FIG. 7 ) connecting first header  108  to manifold top plate  102 . A plurality of hose barbs  114  on first header  108  connect the pneumatic passages of first header  108  to the pilot operated valves and pumps contained in actuator assembly (shown above in  FIG. 1 ) using flexible urethane tubing (not shown) for example. The actuator assembly (shown above in  FIG. 1 ) can be separated readily from manifold assembly  100  by removing screws  112 . 
     Manifold assembly  100  includes a second header  116 , which is also is attached to manifold top plate  102  in a sealed manner using o-ring seals  110  and screws  112 . O-Ring seals  110  provide a leak tight connection between all of the internal passageways connecting second header  116  to manifold top plate  102 . A plurality of hose barbs on second header  116  connect the pneumatic passages of second header  116  to pressure transducers contained in a separate printed circuit board assembly, which is similar to item  40  shown in  FIG. 2  of the prior art using flexible urethane tubing (not shown). The pressure transducer printed circuit board  40  can be separated readily from manifold assembly  100  by removing screws  112  and is attached to header  116  via flexible, e.g., urethane, tubing only. 
     Referring now to  FIG. 7 , the underside of plate  102  (from that shown in  FIGS. 4 and 6 ) is illustrated. Internal passageways  134 , discussed above, pneumatically connect hose barbs  114  on first header  108  to ports of the right bank of valves  120  shown in  FIG. 6 . Likewise, internal passageways  138  pneumatically connect hose barbs  114  on second header  116  to the left bank of valves  120  in  FIG. 6 . Some of the other passageways in  FIG. 7  are used to connect air pump heads  156  to filter  136 , air tanks  140  and manual valve  130  as shown in schematics  200  and  210 . There are also passageways in  FIG. 7  that connect the right and left pump chambers (L_DISP and R_DISP), the right and left volumetric reference volumes (VSL and VSR), and their respective pressure sensors to the solenoid valves with which they communicate when pumping fluid and when measuring the volume of fluid that has been pumped. 
     Conversely, manifold assembly  100  can be removed from the machine by disconnecting headers  108  and  116  and removing an electrical connection to printed circuit board (“PCB”)  118  from the PCB. PCB  118  controls valves  120 . 
     PCB assembly  118  is placed in a recessed channel  122  in top plate  102  via shorter screws  124  before valves  120  are attached to top plate  102  via small screws  126 . Electrical contact pins (not seen) extend down from valves  120  and plug into mating connectors (not seen) soldered to PCB assembly  118 . Any of valves  120  can be removed easily and replaced by removing the two small screws  126 . 
     Printed circuit board  118  contains a spike and hold circuit that energizes each of valves  120  with a twelve volt voltage spike and then reduces the applied voltage to a hold level to save energy and reduce the heat that valve  120  produces when it is held open. For example, the spike and hold circuit can reduce the supply voltage from twelve volts to 8.48 volts, which reduces the energy that needs to be dissipated (heat generated) up to fifty percent of that generated at twelve volts. 
     In an alternative embodiment, the spike and hold circuit is stored in software, e.g., via a memory and processor soldered to PCB  118 . Here, smart power proportioning varies the spike duration depending upon how long it has been since the particular valve  120  has been actuated. For example, the processing and memory can set a spike duration for a valve  120  that has not been actuated recently to two-hundred milliseconds, and alternatively set a spike duration for a valve  120  that is continuously operated to only fifty milliseconds, further saving energy and reducing heat generation. The ability to vary the voltage profile that is applied to actuate solenoid valve  120  not only minimizes the heat that the valve generates (reducing the operating temperature of the valve), the variation also minimizes the amount of audible noise that valve  120  generates when energized. Reduced audible noise is especially advantageous when the dialysis machine is used at the patient&#39;s bedside, such as with a home peritoneal dialysis or home hemodialysis machine. 
     A diverter valve  130  is attached directly to top plate  102  via screws  112 . Diverter valve  130  includes two ports on its underside, which seal to manifold  100  using o-rings  110  as shown in  FIG. 6 . Rotation of the slotted screw opposite an external port  132  of valve  130  connects the underside ports of valve  130  fluidly to port  132 . External Port  132  in turn connects fluidly to an external pressure standard (not illustrated) for calibration of the pressure transducers. Rotating slotted screw to its original position blocks port  132 , while enabling the two ports on the underside of diverter valve  130  to communicate fluidly. 
     A particulate filter  136  is sandwiched between top valve plate  102  and bottom valve plate  104 . Gasket  106  seals top valve plate  102  to bottom valve plate  104  and to particulate filter  136 . 
       FIGS. 5 and 8  show molded, cast or machined pneumatic reservoirs  140  mounted to bottom plate  104  using screws  112 . Pneumatic reservoirs  140  hold pressurized air for valves  120  to supply the pressurized air to different subsystems within the dialysis instrument. For example, valves  120  supply pressurized air to the fluid cassette valve chambers and pump chamber. Valves  120  also control air to seal the cassette for operation and to pressurize a bladder that retracts an occluder that otherwise is closed to clamp off all fluid lines for safety purposes. Pneumatic reservoirs  140  are shown below schematically in  FIGS. 10 to 11 . 
     The integrated pneumatic reservoirs  140  have multiple inlets and outlets in one embodiment, which are bores or holes  128  in plate  104  of manifold assembly  100  in one embodiment. As seen in  FIGS. 6 through 8 , the bores  128  run directly from one of the integrated reservoirs  140  to a valve  120 , a pressure sensor, etc. One advantage of the direct connection is that the pressure sensor reads the actual pressure in the reservoir  140 , not the pressure in a line connected to the reservoir, which can differ from the actual reservoir pressure when air is flowing into or from the reservoir  140 . 
     Another advantage of communicating pneumatic reservoirs  140  of manifold assembly  100  with valves  120  via individual bores  128  is that if liquid is sucked into the manifold  100 , e.g., in a situation in which sheeting on the disposable cassette has a hole located adjacent to one of the cassette&#39;s valves, liquid damage is mitigated. With assembly  100 , fluid pulled into the assembly flows into one solenoid valve  120  only, after which the fluid discharged directly through a bore  128  associated with that valve  120  into Neg P Tank reservoir  140  without contaminating other valves  120  or other components. Thus, only a small portion of the pneumatic system might need replacing. 
     Gasket  142  seals pneumatic reservoirs  140  to bottom plate  104 . Vent filters  144  minimize the sound produced when air enters (e.g., from POS T TANK or NEG P TANK as seen in  FIGS. 10 and 11 ) and/or exits manifold assembly  100  and prevents particulate matter from entering manifold assembly  100  along with air. 
     Manifold assembly  100  includes a pneumatic pump  146  marked as PUMP in  FIGS. 10 and 11 . Pneumatic pump  146  pressurizes pneumatic reservoirs  140  and the sealing bladders shown in  FIGS. 10 and 11 . The heads  156  of pump  146  are attached to bottom plate  104  using longer screws  148  on one end and clamp  150  and screws  112  on the other end. Electrometric seals (o-ring, quad-ring, quad-seal, etc.)  110  seal the pneumatic connection of the inlets and outlets of pump  146  to bottom plate  104 . A thermally conductive pad  152  (e.g., Bergquist Gap Pad, Bergquist Sil Pad, Dow Corning TP 1500 or 2100, Fujipoly Sarcon, Laird T-Pli, T-Flex and T-Putty, or 3M 5507S) thermally links the motor  154  from pump  146  to bottom plate  104 , so that bottom plate  104  becomes a heat sink for motor  154  and pump  146 , absorbing the thermal energy that motor  154  creates. Bottom plate  104  is accordingly made of aluminum or other thermally conducting material in one embodiment. The thermal connection via thermally conductive pad  152  has been found to lower the operating temperature of pump motor  154  from around 100° C. to around 60° C., which should increase the life expectancy of pump  146 . 
     The mounting and thermal coupling of pump  146  to bottom plate  104  also increases the effective mass of pump  146 , so that pump  146  produces sound having a lower (and less bothersome) frequency and magnitude. Further, in one embodiment, manifold Assembly  100  is mounted within a sealed (potentially air tight), acoustically insulated enclosure, further reducing magnitude of sound emanating from the enclosure. The lower operating temperature of pump  104  promotes use of the enclosure without over heating the manifold assembly. 
     Referring now to  FIGS. 9A to 9D , manifold assembly  180  illustrates one alternative manifold of the present disclosure. Here, pump  146  is located on the upper surface of the assembly with headers  108  and  116  and PCB  118 . Mounting pump  146  as shown in  FIG. 9A  is advantageous because the pump is more accessible for servicing and because the manifold assembly is not as tall. Air reservoirs  140  located on the underside of manifold assembly  180  can be longer and do not need to have as much depth to achieve the same volume. The pump inlet and outlet ports of pump  146  can attach directly to the manifold using o-ring connections. Or, short lengths of flexible tubing can be bent in a u-shape and connect barbed ports located on the pump heads  156  of pump  146  to barbed fittings located on the underside of the plate upon which the pump heads  156  and pump  146  are mounted. 
     Locating pump  146  on the upper surface of the assembly allows only alternative upper plate  202  to be made of metal, e.g., aluminum. Alternative lower plate  204  and intermediate plate  208  can be made of plastic. Upper plate  202  is threaded to accept screws inserted through headers  108  and  116  and plates  204  and  208  to bolt those headers and plates to upper plate  202 . Alternative gaskets  206   a  and  206   b  are located between intermediate plate  208  and upper and lower plates  202  and  204 , respectively, to seal integral flow paths located on the insides of plates  202  and  204  (like paths  134  and  138  of  FIG. 7 ) and around valve ports. Middle plate  208  separates gaskets  206   a  and  206   b  and provides a surface against which gaskets  206   a  and  206   b  can compress. 
       FIG. 9B  shows pump  146  removed to illustrate that the pump mounts to elastomeric sealing inserts  214  placed in intermediate plate  208 .  FIGS. 9A and 9B  illustrate that clamp  150  and conductive pad  152  connect to metallic upper plate  202  in the illustrated embodiment, so that the above-described heat sinking can occur. Upper plate  202  includes a recessed area  216  with a saddle that is designed for the heat sink mounting of pump  146  to upper plate  202 . 
     Recessed area  216  forms or includes a saddle that pump motor  154  fits into. The saddle conducts the heat from pump motor  154  into upper plate  202 , which is the only metallic plate as discussed in one embodiment. Top plate  202  includes all of the tapped holes for pump  146  and the other components of system  180 . The outlet ports of heads  156  seal to middle plate  208 , however, there is very little heat conducted from pump heads  156  to middle plate  208 . Instead, air that is being pumped takes heat away from the pump heads  156  and so acts as a coolant. 
       FIGS. 9C and 9D  show different views of lower plate  204 , which again is plastic in one embodiment. Lower plate includes molded pressure reservoirs  140  and flow paths  218 . Features  222   a  and  222   b  on the underside of lower plate  204  accommodate filter  136  and elastomeric sealing inserts  214 . Reservoirs  140 , middle plate  208  and tubing headers  108  and  116  can all be molded plastic in one embodiment, reducing weight and cost. 
     Pneumatic System Configurations 
     Referring now to  FIG. 10 , schematic  200  illustrates one pneumatic schematic for manifold assembly  100  shown in  FIGS. 4 to 8  and manifold assembly  180  of  FIG. 9 .  FIG. 10  shows twelve valves on the left bank of valves, which correspond to the twelve valves  120  shown mounted on the left side of PCB  118  in  FIGS. 4, 7 and 9 . Likewise, the fourteen valves shown on the right bank of valves of schematic  200  correspond to the fourteen valves  120  shown on the right side of PCB  118  in  FIGS. 4, 7 and 9 . Schematic  200  of  FIG. 10  includes a valve labeled B 5 /NV that is used to lower the vacuum level in negative pressure tank (NEG P Tank)  140  when fluid is to be drained from the patient instead of a supply bag. Previously, the equivalent of air pump  146  of  FIG. 10  would be turned off and the equivalent of valve D 0  (12) of  FIG. 10  would be energized, so that air could bleed through air pump  146 , lowering the vacuum level in Neg P Tank  140 . The need for the vacuum pump to bleed through the pump severely limited the choice of air pumps that could be used because the vast majority of available air pumps do not allow a vacuum to be bled through the pump. 
     In schematic  200  of  FIG. 10 , pneumatic pump  146  includes two heads  156  (see also  FIGS. 5 and 8 ) having inlets and outlets connected in parallel. Dual heads  156  individually pressurize reservoirs  140  simultaneously in the embodiment shown in schematic  210  of  FIG. 11 . One head is dedicated to pressurizing positive pressure reservoir (Pos P (Lo Pos) tank)  140 . Positive pressure reservoir  140  in one embodiment is controlled at about 1.5 psig when pumping to the patient or at about 5.0 psig when pumping to a solution bag or drain line. The other head  156  is dedicated to evacuating negative pressure reservoir (Neg P tank)  140 . Negative pressure reservoir  140  in one embodiment is controlled at about −1.5 psig when pumping from the patient or at about −5.0 psig when pumping from a solution bag. Because pump  146  does not have to switch back and forth between reservoirs  140 , the reservoirs  140  are filled on a more constant and smooth basis, reducing noise and reducing the energy required to operate pump  146 . Halving the flow to dual pump heads  156  reduces the pressure losses due to flow restrictions to nearly one-quarter of their original value. Running each reservoir at half flow rate reduces noise because the inrush of air to positive reservoir  140  or from negative reservoir  140  is less severe. 
     Both schematics  200  and  210  further include an inline filter  136  that prevents particulate generated at air pump  146  from entering manifold assembly  100  or  180 . Schematics  200  and  210  also include a manually operated selector valve  130  (see  FIGS. 4 and 6 ) for diverting a pathway in the manifold to an outside calibration port. 
     Pneumatic schematic  210  of  FIG. 11  shows an alternative pneumatic configuration for manifold assemblies  100  and  180  of the present disclosure. Schematic  210  of  FIG. 11  differs from schematic  200  of  FIG. 10  in one respect because schematic  210  includes a three-way valve A 6  that replaces a two-way Hi-Lo valve A 6  of  FIG. 11 . Three-way valve A 6  of system  10  allows air pump  146  to maintain the pressure in the Pos P (Lo Pos) tank  140  directly, while isolating an occluder tank  56  and Pos T (High Pos) tank (bladder  54  of  FIG. 1 ). 
     The occluder tank  56  and Pos T tank  54  are in one embodiment bladders that can expand and contract with pressure changes. Bladder as used herein includes, without limitation, balloon type bladders and bellows type bladders. The force created by the Pos T bladder  54  seals a disposable cassette against a cassette holder  22  on machine  10  that operates one or more pump chamber and valve chamber located within the cassette. In one embodiment, pump  146  pressurizes both bladders  54  or  56  to about 7.1 psig. Previously, the bladder pressures have fluctuated between about 5 psig and 7.1 psig. The bladder pressures for schematic  210  of the present disclosure however have been narrowed to fluctuate between about 6.8 psig and about 7.1 psig. For schematic  200 , the cassette sealing bladder pressure would normally fluctuate between 6.8 psig and 7.1 psig but can fall as low as five psig if the occluder is closed and re-opened. The system of schematic  210  eliminates the possibility of falling to five psig. 
     The force created by the occluder bladder  56  retracts an occluder bar by compressing plural coil springs, allowing fluid to flow to and from the cassette during normal operation. If occluder bladder  56  is not retracted, the occluder will extend, pinching the tubing lines that lead from the cassette to the patient, heater bag, supply bags and drain line so that fluid movement is prevented. Three-way valve A 6  closes off cassette bladder  54  and occluder bladder  56  whenever the air pump has to pressurize Pos P Tank  140 , so that no air is stolen from the bladder. For example, in one implementation, when machine  10  is pumping fluid to the patient, the Pos P (Low Pos) tank  140  pressure is maintained at 1.5 psig. 
     A replenishment of a heater bag (stored on tray  16  shown in  FIG. 1 ) follows each patient fill, which requires five psig. To change pressure in Pos P tank  140  from 1.5 to five psig, PCB  118  energizes three-way valve A 6 , closing off the cassette sealing bladder and occluder bladder  56  supply lines so that the pressure in the bladders cannot fall. The pressure in the Pos T bladder  54  and occluder bladder  56  can momentarily fall to as low as about five psig at this time, which is close to the pressure needed to retract the occluder, i.e., the occluder could actuate inadvertently generating a creaking noise if the two-way valve of schematic  200  is used instead of the three-way isolating valve of schematic  210 . In schematic  210 , the pressure in the Pos T bladder  54  and occluder bladder  56  will not change upon a replenishment of the heater bag because pneumatic system  210  uses three-way valve A 6 . 
     In another example, if the pressure in Pos T bladder  54  falls to as low as about five psig, the seal between the disposable cassette and machine interface can be broken momentarily. It is possible that the seal will not be recreated when the pressure in Pos T bladder  54  is increased to its normal operating pressure of about 7.1 psi. Machine  10  without three-way valve A 6  (e.g., schematic  200  of  FIG. 10 ) can be configured to detect this leak by performing a pressure decay test on Pos T bladder  54  and post an alarm when such leak is detected. The alarm is cleared by cycling the power off and back on. If the pressure is below about 4.5 psig when the power comes back on, the therapy is terminated because the cassette seal is determined to have been broken. The machine operating according to schematic  210  however avoids this alarm by isolating Pos T bladder  54  from the pneumatic lines filling the occluder bladder  56  and/or the Pos P Tank  140 , ensuring that Pos T bladder  54  is at the higher pressure. 
     Schematic  210  allows pump  146  to maintain the pressure in Pos P reservoir  140  directly, so that pump  146  only has to pump against either 1.5 or 5 psig. In schematic  200 , Pos P reservoir  140  is maintained indirectly through Pos T bladder  54 , which requires pump  146  to pump against 7.1 psig of Pos T bladder  54 . Pump  146  generates less noise and less heat when it pumps against the lower pressure. Also, when the 7.1 psig Pos T bladder  54  and the occluder bladder  56  are connected to Pos P reservoir  140  by valve A 6  in system  200 , the 7.1 psig source produces a rush of air to the 1.5 psig destination. This rush of air generates a noticeable audible noise. 
     In another example, if the pressure of occluder bladder  56  falls to about 5 psig from 7.1 psig, the load on the compression springs decreases allowing the springs to extend the occluder partway but not enough to completely pinch-off the flow of fluid through the tubing leading to or from the cassette. The partial movement of the occluder results in an audible creaking noise that can wake up a sleeping patient. The isolation of three-way valve A 6  prevents such partial occlusion from occurring. 
     Schematic  210  of  FIG. 11  also arranges the dual heads  156  of pneumatic pump  146  so that one head is dedicated to positive pressure generation, while the other head is dedicated to negative pressure generation. The result is a lower rate of air flow through the system when the Pos T bladder  54 , Pos P reservoir  140 , Neg P reservoir  140  or occluder bladder  56  are being maintained, which generates less noise. 
     As seen additionally in  FIG. 12 , whenever the positive pressure of positive pump head  156  or the negative pressure of pump head  156  is not being used, the resulting air flows are diverted through a circuit  220  containing free-flow orifices  158 ,  160  and  162 , operate as shown below. Free-flow orifices  160  and  162  create a resistance to airflow that maintains the sound produced by the air flow at a pitch that is very close to the sound that the pump produces when it is pressurizing the components of schematic  210 . Although the “free flow” orifices  160  and  162  do not reduce the air flow or the sound, the orifices make the sound less offensive to the patient because the sound is maintained at the low pump frequency. 
       FIGS. 12 and 13  show noise reduction circuit  220  in two valve states.  FIG. 12  is the de-energized, recirculation, noise reducing state.  FIG. 13  is the energized, pressure-applying state. In  FIG. 12 , valves C 5  and D 0  (also seen in  FIG. 11 ) are in the de-energized state. Each pump head  156  pumps in a recirculation loop with the outlet flow being directed back to the pump head inlet. Positive pressure orifice  162  and negative pressure orifice  160  maintain a partial load on positive pump head  156  and negative pump head  156 , respectively. 
     When valves C 5  and D 0  switch state as shown in  FIG. 13 , the change in the load on the pump heads  156  is small, so that the pitch and amplitude difference between when pump  146  is running in (i) free flow ( FIG. 12 ) and (ii) both pressure and vacuum ( FIG. 13 ) is minimized. Further, the change in the load on the negative pump head  156  is small, so that the pitch and amplitude difference between when pump  146  is running in (i) free flow ( FIG. 12 ) and (iii) vacuum only (not shown but valve D 0  is as in  FIG. 13 , while valve C 5  is as in  FIG. 12 ) is minimized. Still further, the change in the load on the negative pump head  156  is small, so that the pitch and amplitude difference between when pump  146  is running in (i) free flow ( FIG. 12 ) and (iv) pressure only (not shown but valve D 0  is as in  FIG. 12 , while valve C 5  is as in  FIG. 13 ) is minimized. It should also be appreciated that pitch and amplitude difference is minimized when switching from: state (ii) to state (i), (iii) or (iv); state (iii) to state (i), (ii) or (iv); and state (iv) to state (i), (ii) or (iii). 
     Schematic  210  of  FIG. 11  also includes plural filters  144  ( FIG. 8 ) integrated into manifold assembly  100  in places that an inrush of flow can occur that could generate noise of a higher frequency and magnitude than a baseline noise. For example, one of the filters  144  reduces the magnitude of the noise that Pos P tank  54  generates when pressure is changed from 1.5 psig to 5 psig. Another filter  144  reduces the magnitude of the noise that is generated when the occluder bladder is pressurized. Still another pair of filters  144  reduces the magnitude of the noise that the connection of the pumping chambers  140  to the volumetric reference chambers located at cassette interface  26  ( FIG. 3 ) creates during the fluid measurement process. Multi-layered manifold assembly  100  accommodates placement of the above filter elements  144  economically wherever they are needed. 
     Schematic  210  of  FIG. 11  shows yet another improvement for integrated manifold assembly  100  or  180 . A one-way flow check valve  212  is included in the conduit supplying pressure to the valve, which supplies PosT bladder  54 , which in turn maintains the pressure that seals the cassette and its fluid pathways. Cassette-sealing bladder  54  with check valve  212  cannot lose pressure when or after occluder bladder  56  is pressurized. Check valve  212  thus prevents a loss of the seal between the cassette and gasket located in the cassette interface  26  due to a momentary loss of pressure of occluder bladder  56 . A solenoid valve can be used instead of the one-way check valve. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.