Patent Publication Number: US-10765805-B2

Title: Infusion pump including pain controlled analgesic (“PCA”) apparatus

Description:
PRIORITY CLAIM 
     This application is divisional of and claims the benefit of and priority to U.S. patent application Ser. No. 14/832,617, filed Aug. 21, 2015, now U.S. Pat. No. 10,159,789, which is a continuation application of, and claims the benefit of and priority to U.S. patent application Ser. No. 13/734,445, filed on Jan. 4, 2013, now U.S. Pat. No. 9,132,232, which is a continuation application of, and claims the benefit of and priority to U.S. patent application Ser. No. 13/043,044, filed on Mar. 8, 2011, now U.S. Pat. No. 8,361,010, which is a continuation application of, and claims the benefit of and priority to U.S. patent application Ser. No. 12/061,496, filed on Apr. 2, 2008, now U.S. Pat. No. 7,914,483, the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to medication delivery and more particularly to delivery of a pain controlled analgesic (“PCA”). 
     Infusion pumps are used to administer liquid drugs to patients. The liquid drug is supplied from a source of the drug and delivered to the patient via a catheter or other injection device. The infusion pump controls the manner in which the liquid drug is infused to the patient. The pump can have various modes of infusion. An infusion pump can operate in different modes of infusion, such as: (i) a continuous mode in which the pump delivers a single volume at a single rate; (ii) an auto-ramp mode in which the pump delivers the liquid drug at a rate that gradually increases to a threshold rate, remains at the threshold rate for a period of time, and then gradually decreases; (iii) an intermittent mode in which the pump delivers discrete liquid volumes spaced over relatively long periods of time, such as a liquid volume every three hours; (iv) a custom mode in which the pump can be programmed to deliver a unique infusion rate at discrete time periods; and (v) a pain controlled analgesic (“PCA”) mode during which the pump periodically infuses boluses of an analgesic in response to requests by the patient. 
     The PCA delivery has a number of benefits including: (i) a time savings between when the patient feels pain and/or the need to receive analgesia and when the drug is administered; (ii) a reduction of workload of the nursing staff (an amount of the prescribed analgesic, enough for multiple doses, is pre-loaded into the infusion device and delivered via PCA mode); (iii) reduction of the chance for medication error (PCA programmed per physician&#39;s order for amount); (iv) patients receive medicine when they need it, instead of having to wait for the nursing staff; (v) patients who use PCA devices have reported better analgesia and lower pain scores than those patients who have to request analgesia from the nursing staff; and (vi) PCA provides a measurement of how much pain an individual patient is experiencing from one day to the next. 
     PCA modes of drug delivery involve the intravenous, epidural, or subcutaneous administration of a liquid opioid. The infusion pumps currently in use for PCA in some instances give the clinician two parameters to set when prescribing a given drug for a patient: (i) a dose or bolus amount of drug administered whenever the patient presses a button and (ii) a lockout interval which determines how soon after a bolus is administered that a second bolus can be delivered if the patient presses the button again. If a patient presses the button before the lockout interval has elapsed, the PCA pump ignores the request. The dose and lockout are programmed into the pump for an individual patient and drug combination. The dose is prescribed based on the clinician&#39;s assessment of the patient&#39;s drug or opioid requirement (depending on weight and habituation. The lockout interval is generally set depending on the time to onset of clinical effect of a given drug. The lockout interval is used to prevent a patient drug overdose resulting from giving himself or herself another bolus before the previous bolus has had a chance to take effect. 
     Sometimes a third parameter is programmed into a pump providing PCA. This is the flow rate of a continuous infusion of medication providing a background of opioid on top of which PCA is added. The continuous infusion is adjusted to provide the minimum amount of drug needed by a patient over time. The PCA component then allows the patient to administer extra (rescue or break-through-pain) doses as needed. This technique of using a continuous infusion along with PCA minimizes the requirement for a patient to push the button repeatedly as a bolus wears off. This is particularly useful at night when the patient&#39;s sleep would otherwise be interrupted regularly. 
     The PCA button is connected to the infusion pump via a cord. The infusion pump supplies an analog voltage to the button. The infusion pump&#39;s electronics recognizes a patient&#39;s closure of the PCA button by detecting a change in voltage level, which is normally not seen but seen when the button is pressed. 
     The analog cables can be prone to a number of errors. A frayed wire or wires within the cord may not allow current to flow or enough current to flow to trigger the electronics when the patient pushes the PCA button, rendering the pump unable to deliver a bolus of analgesic, or possibly delivering a bolus when it is not needed or has not been requested. Or, the wires can become short circuited, damaging electrical components in the pump or opening a fuse, which may need to be replaced, and may also lead to improper analgesic dosage delivery. 
     A need accordingly exists for an improved PCA input apparatus and method. 
     SUMMARY 
     The present disclosure provides a pain controlled analgesic (“PCA”) apparatus, which is more reliable than current systems. 
     In one embodiment, an infusion pump is provided that is connected to a PCA input device having one or more button. The device is connected to the pump&#39;s primary housing via a cord. The PCA input device includes a remote microchip or integrated circuit. The chip or circuit communicates with a local chip or circuit located at the infusion pump. Communication between the remote (button) microchip and local (pump) microchip is performed digitally and/or through frequency matching. Communication protocols such as Inter-Integrated Circuit (“I 2 C”), Serial Peripheral Interface Bus (“SPI”) (two or three wire), Transistor-Transistor Logic Universal Asynchronous Receiver/Transmitter (“TTL UART”), or Standard RS232 Universal Asynchronous Receiver/Transmitter (“RS232 UART”) may be used between the remote and local microchips. The type of protocol chosen depends upon the number of wires in the cord. The cord can have, for example, a single fiber optic cable, two wires or three wires, which are configured to carry low analog voltage, e.g., 3 to 24 VDC, signals. 
     The remote microchip senses when the one or more PCA button is pressed and sends a corresponding signal to the local microchip. The local microchip in turn is connected electrically to the pump&#39;s processing and memory, which causes a pump motor to deliver a bolus of analgesic if conditions are appropriate to do so, e.g., if the current button press has not occurred too soon after previous button press. 
     The digital protocol (digital message protocol or frequency waveform) is configured to sense for example when a communication line has been broken, e.g., through the lack of response from a handshaking request from the local microchip to the remote microchip. For example, the local microchip can be programmed to send a handshake request to the remote microchip after a predetermined time interval. If the request is sent and no response is sent back, the local microchip can tell the pump processing and memory that there is a problem with the PCA button. The local microchip can either be programmed to send a second handshake request or be told to do so by the pump electronics. If a second handshake request is again not answered (second attempt not absolutely necessary or more than one second request could be made) the infusion pump is configured to take appropriate action. 
     In one embodiment, appropriate action includes providing an alarm or alert at the pump, e.g., in the form of an audible alarm and a message on the pump&#39;s video screen saying, e.g., “PCA disabled.” Alternatively or additionally, the pump can be configured to provide a dose of analgesic to the patient either at a preset interval and dose or at a last recorded interval and dose. For example, if the alarm is not cleared, e.g., no nurse has responded or the patient is at home and asleep, and a period of time transpires after which the pump should have been told to deliver a dose of analgesic, the pump can provide a dose, e.g., prescribed dose of the analgesic and continue to do so at the set intervals until the alarm is cleared. 
     The above handshaking routine is performed regularly enough in one embodiment such that a broken or frayed cord is detected before the patient is likely to press the PCA button. Either the remote or local microchip or the pump electronics can be programmed to look for other PCA input failures, such as failures with the PCA button or switches within the input device housing the button. To this end, any one or more of the microchips and the pump electronics can have programmable processing and memory to detect additional failure modes. 
     For example, the button of the PCA input device is a momentary button in one embodiment, which the patient need only press for a moment to initiate delivery of an analgesic bolus. When the patient releases the button, a spring pushes the button such that a break in electrical contact is made. It may happen that the spring does not function properly and the button stays depressed after the patient releases the button. In such a case, the PCA system of the present disclosure can detect the stuck button in a myriad of ways. 
     In one way, the remote integrated circuit detects a constant rather than a momentary input from the PCA button. The remote integrated circuit has programmed processing and memory to determine a stuck button condition, the remote integrated circuit sends a “stuck button” message to the local integrated circuit, which relays the message to the pump&#39;s processing and memory, which alarms and takes other corrective action. 
     In another way, the remote integrated circuit detects a constant rather than a momentary input from the PCA button and relays the constant signal to the local integrated circuit. The local integrated circuit has programmed processing and memory to determine a stuck button condition, the local integrated circuit sends a “stuck button” message to the pump&#39;s processing and memory, which alarms and takes other corrective action. 
     In a further way, the remote integrated circuit detects a constant rather than a momentary input from the PCA button and relays the constant signal to the local integrated circuit, which in turn relays the signal to the pump&#39;s processing and memory. The pump&#39;s processing and memory has programmed processing and memory to determine a stuck button condition and alarms and takes other corrective action. 
     In another example, the button of the PCA input device is a maintained button, which the patient need only press for a moment to initiate delivery of an analgesic bolus. When the patient releases the button in this instance, however, the button remains depressed until another action causes the button to release, e.g., a timer times out or the bolus is competed. Here, the mechanism holding the button in a depressed state, e.g., against a spring, may have trouble maintaining electrical contact, causing the button to intermittently make contact or “chatter.” In this case too, the PCA system of the present disclosure can detect the chattering PCA contact in a myriad of ways by placing the programmed processing an memory at the remote integrated circuit, the local integrated circuit or the pump&#39;s processing and memory as described above for the stuck PCA button. 
     In a further example, the wires within the PCA cord can become shorted causing a false request for a bolus dose. Here, a continuous signal can be treated the same as a stuck button by placing the programmed processing and memory at either the local integrated circuit or the pump&#39;s processing an memory. Alternatively, when the local integrated circuit receives a signal from the remote integrated circuit requesting an analgesic bolus, the local integrated circuit can send a handshake signal back to the remote integrated circuit for the remote integrated circuit to confirm. The remote integrated circuit will either not send the confirm signal or the shorted lines will impede the signal. 
     It is accordingly an advantage of the present disclosure to provide an improved infusion pump. 
     It is another advantage of the present disclosure to provide an infusion pump having an improved pain controlled analgesic (“PCA”) input device. 
     It is a further advantage of the present disclosure to provide a PCA input device having diagnostic capability for both the input device and the cord connecting the input device to the pump housing. 
     It is yet another advantage of the present disclosure to provide a PCA input device having open circuit detection capability. 
     It is yet a further advantage of the present disclosure to provide a PCA input device having short circuit detection capability. 
     It is still another advantage of the present disclosure to provide a PCA input device having button stuck detection capability. 
     It is still a further advantage of the present disclosure to provide a PCA input device having button chatter detection capability. 
     Further still, it is an advantage of the present disclosure to provide an infusion pump having a PCA input system that can detect when the PCA input device is not functioning properly and override the PCA input device and provide an analgesic dose automatically. 
     Additional features and advantages are described herein, and will be apparent from, the following Detailed Description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view illustrating one embodiment of an infusion pump of the present disclosure. 
         FIG. 2  is another perspective view illustrating one embodiment of an infusion pump of the present disclosure. 
         FIG. 3  is a schematic view showing one embodiment of a control architecture for the pain controlled analgesia (“PCA”) apparatus of the present disclosure. 
         FIG. 4  is a schematic view illustrating one embodiment for configuring the integrated circuits disclosed herein with the PCA apparatus of the present disclosure. 
         FIG. 5  is a schematic view illustrating another embodiment for configuring the integrated circuits disclosed herein with the PCA apparatus of the present disclosure. 
         FIG. 6  is a chart showing different embodiments for communication between the integrated circuits and pump control of the present disclosure. 
         FIG. 7  is a logic flow diagram illustrating one frayed cord or open circuit method of operation for the PCA apparatus of the present disclosure. 
         FIG. 8  is a logic flow diagram illustrating one crossed-wire or short circuit method of operation for the PCA apparatus of the present disclosure. 
         FIG. 9  is a logic flow diagram illustrating one stuck button method of operation for the PCA apparatus of the present disclosure. 
         FIG. 10  is a logic flow diagram illustrating one chattering contact method of operation for the PCA apparatus of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings and in particular to  FIGS. 1 and 2 , an embodiment of an infusion pump  10  having the microchip based pain controlled analgesic (“PCA”) apparatus of the present disclosure is illustrated. Infusion pump  10  includes a housing  12 . In the illustrated embodiment, housing  12  of infusion pump  10  has a generally contoured shape. Housing  12  can have other shapes if desired. 
     The housing  12  includes a first member  14  and a second member  16  that are connected together to form a central cavity  18 . Central cavity  18  houses various components of the pump  10  including the user interface  20 . The first member  14  of the housing has an opening  22  that accommodates a display screen of the user interface  20 . A rear portion of the housing  12  has a receptacle or recess  24  that is adapted to receive a power supply  26 . At a bottom, front portion of the housing  12 , a container compartment or syringe compartment  28  is defined that accommodates a syringe assembly  30 , a portion of a drive mechanism  40  and other components. The first member  14  of the housing  12  has a hinged access door  32  that encloses syringe assembly  30  in compartment  28 . Access door  32  can be transparent for medical personnel to view the contents within syringe assembly  30 . 
     A lock  34  is provided with door  32  to prevent unauthorized access to syringe assembly  30 . An upper portion of the housing  12  is provided with a handle  36 . Housing  12  can be made from a variety of materials including various types of plastics and metals. Housing  12  has a pole clamp  38  attached to the second member  16  of the housing  12 . Pole clamp  38  can have various designs and is adapted to mount pump  10  on a pole assembly used in a hospital setting. In one embodiment, pole clamp  38  can mount pump  10  in various positions. For example, the pump  10  can be mounted in a generally horizontal position shown in FIGS. 3A and 3B of U.S. Pat. No. 7,018,361 (“the &#39;361 patent”) entitled “Infusion Pump”, the entire contents of which are incorporated herein by reference. 
       FIG. 2  shows syringe compartment  28  in greater detail. Syringe compartment  28  is dimensioned to receive and support the syringe assembly  30  and receive a portion of drive mechanism  40 . Syringe assembly  30  includes a syringe barrel  42  and a syringe plunger  44 . Syringe barrel  42  contains medication and slidably receives the syringe plunger  44 . Drive mechanism  40  drives syringe plunger  44  to force medication from the syringe barrel  42  through a tube (not shown) and to a patient. The tube has one end connected to an end of the syringe barrel  42  and another end configured to be connected to a patient. 
     The syringe compartment  28  has a rear wall  46  that is generally concave to receive the syringe barrel  42  of the syringe assembly  30 . The syringe barrel  42  of the syringe assembly  30  and rear wall  46  are generally in confronting relation. The housing  12  further has a curved lip  48  that in one embodiment is integral with the rear wall  46 . Lip  48  aids in loading a syringe  26  in the compartment  28  to be described in greater detail below. As shown in  FIG. 2 , a syringe clamp  50  is movably mounted in the compartment  28 . The clamp  50  has a concave inner surface that faces the rear wall  46  and that fits over the syringe barrel  42 . Clamp  50  is slidable along a rod assembly (see number 54 at FIG. 18 of the &#39;361 patent) to move the clamp  50  towards and away from the rear wall  46 . The clamp  50  can slide along the rod assembly  52  to accommodate different sized syringe barrels. A base portion of the clamp  50  has a pair of rollers  54 ,  56  that help reduce friction when the clamp  50  slides along the housing  12 . Due to tolerances, the clamp  50  may also pivot slightly. Clamp  50  is resiliently biased towards rear wall  46 . 
     Housing  12  and syringe compartment  28  are sized such that an entire syringe assembly, with plunger fully extended from the syringe barrel, is contained within the housing and can be enclosed by the access door  32 . No part of a syringe barrel or syringe plunger protrudes from the housing  12 . A portion of the drive mechanism  40  extends into the syringe compartment  28  to engage the plunger  44 . Access door  32  has an opening that accommodates the tube (not shown) that is attached to the syringe barrel  42  to deliver medication to the patient. 
     As shown in  FIG. 1 , pump  10  has a user interface  20 . Portions of the user interface  20  are described in greater detail in commonly owned U.S. patent application Ser. No. 10/172,808 (2004-0225252) entitled “System And Method For Operating An Infusion Pump”, the entire contents of which are incorporated herein by reference. User interface  20  includes a display screen  58 , a first control panel  60 , a second control panel  62  and associated electrical components and computer software contained within the housing  12  to operate the pump  10 . Display screen  58  displays all of the general operating parameters of the pump  10  and fits within the opening  22  in the housing  12 . 
     The display screen  58  in one embodiment operates with a touch screen overlay for a user to enter data to be into the pump  10 . As discussed, the pump  10  can be mounted in either a generally horizontal position or a generally vertical position. The software associated with the user interface  20  and pump  10  has the ability to display information on the screen  58  in either a landscape orientation or a portrait orientation. When the pump is mounted in the horizontal configuration information is displayed on the display screen  50  in a landscape configuration. When pump  10  is mounted in the vertical configuration, information is displayed on the display screen  50  in a portrait configuration. Thus, depending on how the pump  10  is mounted, the information can be read by users without the need to tilt one&#39;s head. This feature is described in greater detail in commonly-owned U.S. Pat. No. 6,997,905 entitled “Dual-Orientation Display For Medical Devices”, the entire contents of which are incorporated herein expressly by reference. First control panel  60  has a start button  64 , a stop button  66  and an alarm/alert button  68 . Second control panel  62  has a settings panel  70 , a history button  72  and a data port  74 . Pump  10  also includes a radio frequency identification (“RFID”) reader  76 , which reads a radio frequency (“RFID”) tag  78  placed on syringe barrel  42 . Data port  74  in one embodiment is an infrared data port, which communicates with a personal data assistant (“PDA”)  80  operated by a nurse or clinician. 
     The pump  10  provides patient-controlled analgesia (“PCA”). As shown in  FIG. 2 , pump  10  includes a PCA input device  100 , which allows the patient to manually actuate the pump actuator to deliver a bolus of analgesic to the patient when desired and when proper. PCA input device  100  is connected via a cord  102 , which is plugged into or otherwise connected to housing  12  of pump  10 . PCA input device  100  in one embodiment includes a peripheral structure that protects against inadvertent actuation. The PCA input device  100  and/or cord  102  can also be lighted so as so glow in the dark to aid patients in locating the button. PCA input device  100  includes a button  104 , which can be a momentary or maintained button as discussed in detail below. 
     Referring now to  FIG. 3 , one embodiment for an electrical layout for pump  10  as it relates to PCA input device  100  is illustrated. Pump  10  includes a plurality of processors, which can be a master processor (e.g., a central processing unit) running a plurality of delegate processors. Pump  10  can also include a safety processor to provide redundancy and ensure proper operation of the other processors. Central processing and memory  106  in one embodiment oversees the pump actuator processing and memory  108 , which in turn controls the movement of drive mechanism  40  that drives syringe plunger  44  to force medication from the syringe barrel  42  through the syringe plunger. 
     It should be appreciated that while a syringe pump is illustrated, pump  10  can be a peristaltic pump, a micro-pump, a piezoelectric pump, each capable of delivering a medical fluid to a patient. Accordingly, while the source of the drug or medicament is shown as being syringe barrel  42 , the source is alternatively a bag or other medical fluid container. Still further alternatively, pump actuator processing and memory  108  in an alternative embodiment are integrated with central processing and memory  106 . 
     Pump actuator processing and memory  108  likewise communicates with a local PCA controller  110 . Communication between actuator processing and memory  108  and local PCA controller  110  can be via a protocol, such as Inter-Integrated Circuit (“I 2 C”), Serial Peripheral Interface Bus (“SPI”) (two or three wire), Transistor-Transistor Logic Universal Asynchronous Receiver/Transmitter (“TTL UART”) and Recommended Standard 232 Universal Asynchronous Receiver/Transmitter (“RS232 UART”). In a similar manner, local PCA controller  110  can communicate with remote controller  112  via a protocol, such as Inter-Integrated Circuit (“I 2 C”), Serial Peripheral Interface Bus (“SPI”) (two or three wire), Transistor-Transistor Logic Universal Asynchronous Receiver/Transmitter (“TTL UART”), Recommended Standard 232 Universal Asynchronous Receiver/Transmitter (“RS232 UART”) and fiber optic cable. As seen in  FIG. 3 , local PCA controller  110  is separated from remote PCA controller  112  via cord  102 . The signals between controllers  110  and  112  can be low voltage analog, e.g., zero to five VDC or 4 to 20 milliamp, signals. 
     Remote controller  112  operates with PCA input device  100  to receive an input from the patient when the patient presses button  104  to receive a bolus of analgesic. When button  104  of PCA input device  100  is pressed, remote integrated circuit or microchip  112  sends a digital message to local integrated circuit or microchip  110 . As shown below, local integrated circuit or microchip  110  can also send a digital message to remote integrated circuit or microchip  112  either by way of response or to initiate a handshake or other desired back-and-forth with remote integrated circuit or microchip  112 . Remote integrated circuit or microchip  112  can also respond to a digital message sent from local integrated circuit or microchip  110 . 
     Referring now to  FIGS. 4 and 5 , two different configurations for the remote and local controllers  110  and  112 , relative to PCA cable  102 , PCA input device  100  and housing  12  of pump  10  are illustrated.  FIG. 4  illustrates one embodiment in which local integrated PCA circuit  110  is housed within housing  12  of pump  10  and remote integrated PCA circuit  112  is located within a housing  114  of PCA input device  100 . Remote controller  112  can include at least one integrated circuit chip or microchip  116 , such as an off the shelf, low power utilization, electronic microchip. Remote controller  112  is shown connected to button  104  via wires  120   a . Alternately, button  104  includes a contact that mates with a contact located directly on remote controller  112 , making separate wires unnecessary. Remote controller  112  is also connected electrically to wires  120   b  of cord  102 . Wires  120   a  and  120   b  connect to microchip  116 . Microchip in one embodiment includes onboard processing and memory. However, processing and memory external to microchip  116  could be used alternatively. Traces  122   a  formed on a printed circuit board (“PCB”)  124   a  connect microchip  116  to wires  120   a  and  120   b  and associated downstream components. 
     Cord  102  is connected to housing  12  of pump  10  via an electrical fitting  126 . Local controller  110  can include at least one off of the shelf integrated circuit chip or microchip  118 , which also has onboard processing and memory (processing and memory are alternatively external). Local controller  110  is connected electrically to wires  120   b  of cord  102 . Wires  120   c  connect local controller  110  to actuator processing and memory  108  ( FIG. 3 ). Wires  120   b  and  120   c  connect to microchip  118  via traces  122   b  formed on a PCB  124   b , to which microchip  118  is also soldered. Local controller  110  is located alternatively on a same PCB as actuator processing and memory  108  ( FIG. 3 ) and communicates with actuator processing and memory  108  via circuit board traces. Cord  102  in the illustrated embodiment is a three-wire cord but alternatively has a different number of wires  120   b  if needed. 
     In the alternative embodiment of  FIG. 5 , cord  102  incorporates local controller  110  and remote controller  112  into connectors  126   a  and  126   b  of the cord, which in turn connect cord  102  respectively to PCA device  100  and pump  10 . Remote controller  112  of connector  126   a  of  FIG. 5  can include at least one integrated circuit chip or microchip  116 . Remote controller  112  is shown connected to button  104  via wires  120   a . Remote controller  112  is also connected electrically to wires  120   b  of cord  102 . Wires  120   a  and  120   b  connect to microchip  116  via traces  122   a  formed on a printed circuit board (“PCB”)  124   a  to which microchip  116  is soldered. 
     Local controller  110  of connector  126   b  of  FIG. 5  can include at least one integrated circuit chip or microchip  118 . Local controller  110  is connected electrically to wires  120   b  of cord  102 . Wires  120   c  connect local controller  110  to actuator processing and memory  108  ( FIG. 3 ). Wires  120   b  and  120   c  connect to microchip  118  via traces  122   b  formed on a PCB  124   b  to which microchip  118  is soldered. 
       FIG. 6  illustrates, without limitation, three processing scenarios for local controller  110  and remote controller  112 . Three functions separating the three processing scenarios include (i) signal processing, (ii) data manipulation, and (iii) pump actuation and alert generation. In the first scenario, local controller  110  and remote controller  112  are both configured to pass signals to each other. Local controller  110  is configured to send and receive signals from actuator processing and memory  108  ( FIG. 3 ). 
     In the first scenario, local controller  110  and remote controller  112  do not perform any data manipulation such as add, subtract and/or manipulate the data as set forth below in the algorithms of  FIGS. 7 to 10 . Here, actuator processing and memory  108  performs the above-mentioned data manipulation and controls the pump to deliver an analgesic bolus or causes an alert to be sounded, whichever is needed. Here, remote controller  112  senses an input, e.g., press of button  104 , sends a corresponding signal to local controller  110 , which relays the signal to actuator processing and memory  108 , which in turn controls the pump to deliver an analgesic bolus or causes an alert to be sounded, whichever is needed. 
     In the second scenario, local controller  110  and remote controller  112  are both configured to pass signals to each other. Local controller  110  is configured to send and receive signals from actuator processing and memory  108  ( FIG. 3 ). In the second scenario, remote controller  112  is configured to perform data manipulation such as add, subtract and/or manipulate the data as set forth below in the algorithms of  FIGS. 7 to 10 . Here, remote controller  112  senses an input, e.g., press of button  104 , remote controller  112  manipulates data to determine when an alarm needs to be generated or the pump is to be actuated. Remote controller  112  sends a corresponding signal to local controller  110 , which relays the signal to actuator processing and memory  108 , which in turn controls the pump to deliver an analgesic bolus or causes an alert to be sounded, whichever is needed. 
     In the third scenario, local controller  110  and remote controller  112  are both configured to pass signals to each other. Local controller  110  is configured to send and receive signals from actuator processing and memory  108  ( FIG. 3 ). In the second scenario, local controller  110  is configured to perform data manipulation such as add, subtract and/or manipulate the data as set forth below in the algorithms of  FIGS. 7 to 10 . Here, remote controller  112  senses an input, e.g., press of button  104 , and sends a corresponding signal to local controller  110 . Local controller  110  manipulates data to determine when an alarm needs to be generated or the pump is to be actuated. Local controller  110  sends a corresponding signal to actuator processing and memory  108 , which in turn controls the pump to deliver an analgesic bolus or causes an alert to be sounded, whichever is needed. 
     Referring now to  FIG. 7 , an algorithm  130  stored at any of local controller  110 , remote controller  112  and actuator processing and memory  108  illustrates one embodiment in which the PCA system of the present disclosure is configured to determine when cord  102  has become frayed. Upon starting at oval  132 , algorithm  130  sets a counter N=0. Local controller  110  is configured to send periodically, e.g., every half-minute, minute or multiple of a minute, a handshake request to remote controller  112 , as seen at block  136 . If remote controller  112  sends a response to the handshake request to local integrated circuit, meaning proper communication exists between the two controllers (cord is not frayed), as determined at diamond  138 , algorithm  130  waits for the next time to send a handshake request, as seen at block  140 , sets N again to zero, and sends another request at block  136 . The loop between blocks  134  and  136 , diamond  138  and block  140  continues until a handshake response is not sent, as determined at diamond  138 . 
     It should be appreciated that if cord  102  becomes frayed right after the handshake response is sent and the patient at that second presses button  104  for a bolus of analgesic, algorithm  130  will do nothing until the timer times out at block  140 . Although the scenario above is unlikely, it is still desirable to make the time to next request at block  140  relatively small. This way, when cord  102  becomes frayed, only a few seconds or a minute has to pass before such fray is detected. It should also be appreciated that the handshake request can be sent instead from remote controller  112  to local controller  110 , which sends the handshake response back to remote controller  112 . Algorithm  130  will operate equally as well. 
     When a handshake response is not sent, as determined at diamond  138 , algorithm  130  advances a counter to N=N+1, as seen at block  142 . The counter serves as a double, triple or multiple check that the cord is actually frayed. Determining if N=trigger amount at diamond  144  provides a redundant check. Setting N=3 at diamond  144  for example looks to see if handshake is missing over three cycles and so on. If N is not yet equal to the set trigger amount as determined at diamond  144 , algorithm  130  is configured to send another handshake request at block  136 . If a handshake response is now sent as determined at diamond  138  the count is cleared back to zero at block  134 . If a handshake response is again not sent as determined at diamond  138 , N is increased again at block  142 . 
     When N reaches the trigger amount at diamond  144 , algorithm  130  assumes that cord  102  has become frayed, severed or otherwise inoperable. At block  146 , an “open circuit” alert is sent to actuator processing and memory  108 . It should be appreciated that the counting feature could be left out of algorithm  130 , so that an open circuit is determined after a first time there is no response to a handshake request. Actuator processing and memory  108  provides an audio, visual or audiovisual alert at pump  10 , a remote location or both asking the patient or clinician to check cord  102 , as seen at block  148 . 
     Another optional feature is shown at diamond  150 . Pump  10  in one embodiment records the time between the last two analgesic bolus deliveries. Thus pump  10  knows when the next analgesic bolus is likely to be requested. Pump  10  in one embodiment provides an automatic bolus after the last recorded period of time passes, after the last recorded period of time plus an additional time amount passes, or after a predetermined period of time passes. In algorithm  130 , if the alert or alarm is cleared before the next bolus time occurs, as determined at diamond  150 , it is assumed that the frayed cord  102  has been swapped out or that the patient otherwise has an avenue to receiving an analgesic bolus, and algorithm  130  ends as seen at oval  154 . In algorithm  130 , if the alert or alarm is not cleared before the next bolus time occurs, as determined at diamond  150 , a bolus of analgesic is provided automatically to the patient as seen at block  152 , after which algorithm  130  ends as seen at oval  154 . 
     Referring now to  FIG. 8 , an algorithm  160  stored at any of local controller  110 , remote controller  112  and actuator processing and memory  108  illustrates one embodiment in which the PCA system of the present disclosure is configured to determine when cord  102  has a short circuit, e.g., insulation on wires  120   b  is missing so that two wires become conducting. Algorithm  160  starts at oval  162  when it is assumed that the patient has pressed bolus button  104  to request a bolus of analgesic. A corresponding signal is sent from remote controller  112  to local controller  110 , as seen at block  164 . At block  166  local controller  110  sends a confirm request signal to remote controller  112 . 
     If a confirm signal is not sent back from remote controller  112  to local controller  110 , as determined at diamond  168 , the local integrated circuit sends a “short circuit” signal or output to actuator processing an memory  108 , as seen at block  170 , which provides an audio, visual or audiovisual alert at pump  10 , a remote location or both alerting the patient or clinician that a short circuit condition has likely occurred and to check cord  102 , as seen at block  172 . A failed confirm can stem from the confirm request signal not reaching the remote controller  112  or from the remote controller  112  receiving the request but not being able to respond to the local controller  110 . 
     If a confirm signal is sent back from remote controller  112  to local controller  110 , as determined at diamond  168 , the local integrated circuit sends a “provide bolus” signal or output to actuator processing an memory  108 , as seen at block  174 , which causes the pump actuator to provide a bolus of analgesic to the patient as seen at block  176 . Thus, if after a bolus request, the two controllers  110  and  112  are able to communicate, the request is seen as a legitimate request from the patient instead of a short circuit between wires of cords. If after the bolus request, however, the two controllers  110  and  112  are not able to communicate, the request is seen as stemming from some sort of short circuit between the wires of cord  102  that have inadvertently caused a bolus request signal to be sent. Algorithm  160  then ends as seen at oval  178 . 
     Referring now to  FIG. 9 , an algorithm  180  stored at any of local controller  110 , remote controller  112  and actuator processing and memory  108  illustrates one embodiment in which the PCA system of the present disclosure is configured to determine when button  104  of PCA input device  100  has become stuck. In one embodiment, button  104  is a momentary pushbutton which only has to make an electrical contact for a short period of time for remote controller  112  to sense an input from the patient and send a bolus request signal. Here, button  104  includes a spring that unmakes electrical contact when the patient removes his or her thumb or finger from button  104 . Momentary button  104  can become stuck such that the electrical contact is not un-maid when the patient releases from button  104 . 
     Algorithm  180  starts at oval  182  when the patient presses button  104  and a request for analgesic bolus is sensed at block  184 . Upon sensing the request signal, algorithm  180  starts a timer “t” at block  186 . If timed “t” is greater than an expected time t expected  as determined at diamond  188 , a “stuck button” alert is provided, which can be an audio, visual or audiovisual alert at pump  10 , a remote location or both, which alerts the patient or clinician that a stuck button condition has likely occurred, as seen at block  190 . 
     If however timed “t” is not greater than an expected time t expected  as determined at diamond  188 , algorithm  180  determines if the bolus request signal has stopped as determined at diamond  192 . If the timer signal has not stopped, timing continues at block  186  and the loop of block  186 , diamond  188  and diamond  192  continues until timed “t” is greater than an expected time t expected  (diamond  188 ) or the request signal stops (diamond  192 ). 
     If the request signal stops as determined at diamond  192  before timed “t” reaches t expected , the bolus of analgesic is delivered to the patient as seen at block  194 . Here, the momentary signal stops before a stuck or sticking bolus button  104  is detected. Upon sounding the alert or providing the analgesic bolus, algorithm  180  ends as seen at oval  196 . 
     Referring now to  FIG. 10 , an algorithm  200  stored at any of local controller  110 , remote controller  112  and actuator processing and memory  108  illustrates one embodiment in which the PCA system of the present disclosure is configured to determine when button  104  of PCA input device  100  has a chattering contact. In one embodiment, button  104  is a maintained pushbutton, which when pressed stays depressed until another event occurs, e.g., another button is pressed or a timer times out. Maintained button  104  when depressed can have a contact that chatters back and forth instead of making steady contact. 
     Algorithm  200  starts at oval  202  when the patient presses button  104  and a request for analgesic bolus is sensed at block  204 . If the signal sensed is fragmented or not continuous, as determined at diamond  206 , a “chattering contact” alert is provided, which can be an audio, visual or audiovisual alert at pump  10 , a remote location or both, which alerts the patient or clinician that the button  104  is not functioning properly, as seen at block  208 . If however the request signal is continuous or non-fragmented, as determined at diamond  206 , the bolus of analgesic is delivered to the patient as seen at block  210 . Upon sounding the alert or providing the analgesic bolus, algorithm  200  ends as seen at oval  212 . 
     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.