Abstract:
An integrated disposable set for dialysis or ultrafiltration treatment of blood is disclosed that includes a memory “key” chip. The key contains information relating to the set, including calibration for sensors, model and date of manufacture and a proprietary secret code to prevent unauthorized duplication of a circuit. The key is activated when treatment of a patient begins to prevent reuse of the set and a delay in use of the set that is too long. Patient data and operational information can be stored in the key during treatment. The key can be returned to the manufacturer or entered into hospital database for analysis. The key is preferably an EEPROM chip that can be embedded in an integral circuit sensor or a separate plug in device, such as a code card.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to the extracorporeal treatment of blood, and more particularly to the Renal Replacement Therapy or Artificial Kidney.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Mechanical Fluid Removal Therapies  
           [0003]    Different modalities of Continuous Renal Replacement Therapy (CRRT) have been used to treat patients suffering from excess fluid overload and acute renal failure. In the acute setting, CRRT has been performed previously using standard methods of hemodialysis and continuous arterio-venous hemofiltration (CAVH). More recently, continuous veno-venous hemofiltration (CVVH) has been used to reduce the complications associated with such issues as hemodynamic instability and need for arterial access.  
           [0004]    Renal replacement therapy performs two primary functions: ultrafiltration (removal of water from blood plasma), and solute clearance (removal of different molecular weight substances from blood plasma). The filter, also called hemofilter or “dialyzer”, can be set up to perform either or both of these functions simultaneously, with or without fluid replacement, accounting for the various modes of renal replacement therapy. “Clearance” is the term used to describe the removal of substances, both normal and waste product, from the blood.  
           [0005]    Ultrafiltration is the convective transfer of fluid out of the plasma compartment through pores in the membrane. The pores filter electrolytes and small and middle sized molecules (up to 20,000 to 30,000 daltons) from the blood plasma. The ultrafiltrate output from the filtration pores is similar to plasma, but without the plasma proteins or cellular components. Importantly, since the concentration of small solutes is the same in the ultrafiltrate as in the plasma, no clearance is obtained, but fluid volume is removed.  
           [0006]    Dialysis is the diffusive transfer of small solutes out of a blood plasma compartment by diffusion across the membrane itself. It occurs as a result of a concentration gradient, with diffusion occurring from the compartment with higher concentration (typically the blood compartment) to the compartment with lower concentration (typically the dialysate compartment). Since the concentration of solutes in the plasma decreases, clearance is obtained, but fluid may not be removed. However, ultrafiltration can be combined with dialysis.  
           [0007]    Hemofiltration is the combination of ultrafiltration, and fluid replacement typically in much larger volumes than needed for fluid control. The replacement fluid contains electrolytes, but not other small molecules. Since the net effect of replacing fluid without small solutes and ultrafiltration of fluid with small solutes results in net removal of small solutes, clearance is obtained.  
           [0008]    2. Limitations of Existing Devices for Ultrafiltration  
           [0009]    Dialysis Machines historically used sets of disposables that can be assembled of various parts from different manufacturers. This allowed flexibility in use, but had certain disadvantages. Joints between parts will spring leaks, allowing ingress of air and facilitating clotting. A high degree of skill was required from users to assemble tubes, connectors, filters and accessories and then load them correctly into pumps, bubble detectors, pressure sensors and other interface elements of a dialysis machine. While in the setting of a chronic dialysis center, such practice was acceptable. In the acute setting, such as an Intensive Care Unit (ICU) of a hospital, it became an impediment.  
           [0010]    This, among other factors, led to under utilization of mechanical fluid removal in the ICU of a hospital in the past. In the U.S., only recently was the sophisticated apparatus “Prisma” from Hospal—Gambro released. This device uses an integrated set where tubing, filter and accessories are all bonded together in the right order and no assembly is required. The filter, sensor interfaces and the four dedicated pump segments (for blood, dialysate, replacement solution and effluent) are also mounted on a flat plastic cartridge to simplify the loading of pumps. The manufacturer advertises the Prisma machine as “an integrated system for continuous fluid management and automated renal replacement therapy blood.” 
           [0011]    Recent changes in the dialysis technology introduced microprocessors, computer graphics interfaces and sophisticated control algorithms. The new generation of controls allows more accurate and safe ultrafiltration. The bases for the advances controls are the sensors. Dialysis equipment uses a variety of sensors that interface with the fluid flow. The sensors include standard configuration pressure sensors, blood leak (typically photometric) sensors and air detection (typically ultrasonic) sensors. Lately, some manufacturers have introduced flow sensors, conductivity sensors, and blood hematocrit sensors.  
           [0012]    In all existing dialysis, ultrafiltration and hemofiltration equipment sensors are part of capital equipment. The single use dialysis sets, integrated or not, only include plastic parts with no built in intelligence. Properties of the plastic material as well as mounting conditions contribute to the uncertainty of measurement. For example a 1% accurate pressure sensor can be used to measure blood pressure in the blood return line. Pressure is transmitted from blood through the silicon diaphragm that is a part of the disposable set. Owing to manufacturing methods and properties of the material, the elasticity of the diaphragm has inherent variability of 10%. As a result, practical accuracy of the sensor is dramatically reduced. The sensor to media interface also reduces other performance parameters, such as frequency response, resolution, and stability.  
           [0013]    Another noted limitation of the existing dialysis sets is the lack of traceability associated with the single use set. In some countries, dialyzers (the most expansive component) are reused, but sets of tubing are always disposable. All disposable sets have serial numbers and limited shelf life. It is the responsibility of the user to ensure that the serial number of the set is recorded, and that the set is not reused or kept out of the package and on the machine longer than is safe. Yet another limitation of the existing single use dialysis set technology is that it can be easily replicated by “after market” manufacturers after the original equipment manufacturer has invested in development. This way, dialysis equipment manufacturers have no means of preventing users from using sets that are made by competitors. There is also an associated danger of an incompatible or partially compatible set being used without the knowledge of the manufacturer of the capital equipment.  
           [0014]    Digital technologies allow easy storage of significant amounts of digital information in relatively inexpensive miniature ROM (Read Only Memory) chips. In recent years the medical disposables technologies are making increasing use of them. There have been several devices where the disposable component of a medical device has an integral or added “memory” component. For example, U.S. Pat. No. 5,720,293 discloses a diagnostic catheter with a memory chip where calibration, patient and serial number information can be stored. Camino Neural Care of San Diego, Calif. manufactures a disposable intra-cranial pressure catheter for use in neurosurgery that comes with an individually programmed memory “key” that contains calibration information for the pressure sensor. None of the aforementioned devices addresses specific needs of an advanced dialysis set.  
           [0015]    The present invention is a new and improved integrated disposable set with a memory device for storing useful information used in a dialysis or ultrafiltration set to improve accuracy of sensors, prevent reuse and incorrect use and to protect the set from replication and selling by competitor.  
         SUMMARY OF THE INVENTION  
         [0016]    It is an object of the present invention to address the needs of fluid removal and dialysis in the acute and emergency settings. It is another object of the present invention to eliminate significant limitations of existing fluid removal and dialysis devices.  
           [0017]    The present invention is directed to a memory device that is used with a disposable ultrafiltration set for dialysis or fluid removal in fluid overloaded patients. The memory device or “key” is preferably an EEPROM that is embedded in a blood circuit sensor used with the ultrafiltration set or a separate key code card that is plugged into the control panel of the set.  
           [0018]    The key can contain information about the manufacture and/or use of the disposable ultrafiltration set, including:  
           [0019]    Set Model Number;  
           [0020]    Serial number;  
           [0021]    Encoded Date of manufacture;  
           [0022]    Encoded Expiration date of the set;  
           [0023]    Proprietary secret code to prevent unauthorized duplication of a circuit;  
           [0024]    Calibration coefficients for single use pressure sensors that are the part of the set;  
           [0025]    Calibration coefficients for single use blood optometric leak detector that is the part of the set;  
           [0026]    Calibration coefficients for the single use optical oximery sensor (SvO2) that is the part of the set; and/or  
           [0027]    Encoded checksum of above data.  
           [0028]    Patient data and operational information can be stored in the key during treatment.  
           [0029]    The key can also store information written into the key relating to treatment of a patient:  
           [0030]    Date and time when the circuit was mounted on the machine;  
           [0031]    Machine serial number and model number;  
           [0032]    Machine CPU software revision;  
           [0033]    Machine hardware revision;  
           [0034]    Date and time when the treatment started;  
           [0035]    Duration of treatment;  
           [0036]    Treatment modality (SCUF, CVVH, CVVHD etc.);  
           [0037]    Alarms;  
           [0038]    User actions;  
           [0039]    User settings such as blood flow, fluid removal rate;  
           [0040]    Actual sensor readings such as circuit pressures, blood and other fluid pump flows, oxygen and other gas contents of blood, hematocrit, venous blood pressure when the pump is stopped;  
           [0041]    Total amount of fluid removed per treatment;  
           [0042]    Date and time when the circuit was dismounted; and  
           [0043]    Battery operation.  
           [0044]    Preferably the key is returnable to the manufacturer or usable by a hospitable so that information stored in the key can be entered into databases usable for various objectives. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0045]    A preferred embodiment and best mode of the invention is illustrated in the attached drawings that are described as follows:  
         [0046]    [0046]FIG. 1 is a perspective view of an intravenous blood ultrafiltration system using a disposable blood circuit cartridge with an integrated pressure sensor.  
         [0047]    [0047]FIG. 2 is a schematic diagram showing a fluid path of blood and removed fluids for the blood circuit cartridge used with the blood ultrafiltration system shown in FIG. 1.  
         [0048]    [0048]FIG. 3 is a schematic of an integrated pressure sensor and an EEPROM device.  
         [0049]    [0049]FIG. 4 is a block diagram of the preferred embodiment of the EEPROM device of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0050]    The present invention is a memory device that is used with a single use disposable set for dialysis or ultrafiltration of blood to treat fluid overload in patients in a on-ICU setting. The disposable ultrafiltration set is disclosed in commonly-owned U.S. patent application Ser. No. 09/660,195, filed Sep. 12, 2000, which application is incorporated herein by reference. The ultrafiltration set is mountable on a console equipped with two pumps (for blood and ultrafiltrate). The set contains a disposable circuit with an integral filter and three integrated pressure sensors. Unlike common dialysis disposables that come in separate pouches and need to be assembled, the disposable circuit comes in one organized tray similar to ones used by interventional cardiologists. Inside the tray are all the components that are needed to treat a single patient. The memory key of the present invention is tethered to the disposable circuit and sealed in the tray. A brief description of the disposable set and the console on which it is mounted follows.  
         [0051]    [0051]FIG. 1 shows an intravenous blood ultrafiltration system  100  for treating a patient (not shown) suffering from fluid overload. To initiate ultrafiltration treatment, two standard  18 G IV needles (not shown) are introduced into suitable peripheral veins (not shown) for the withdrawal and return of the blood. The needles are attached to a withdrawal tubing  104  and a return tubing  105 , and secured to skin with attachments, such as adhesive strips (not shown). The withdrawal and return tubing  104  and  105 , forms portions of a continuous blood fluid passage  108  that extends through a disposable blood circuit cartridge  109  (FIG. 2). The disposable blood circuit cartridge  109  is attached to a pumping console  110 .  
         [0052]    Tubing sections similar to the blood tubing  104  leading from and blood tubing  105  leading to the patient extend through cartridge  109  and form additional links in the blood fluid passage  108 . These tubing links are coupled to a blood filter  111  and pressure sensors  112 ,  113 , that are contiguous with the tubing and form sections of the blood fluid passage  108 . In other embodiments it can be envisioned that the blood filter  111  is supplied separately and can be connected to the cartridge by the operator before treatment.  
         [0053]    The filtrate disposable blood circuit cartridge  109  is supplied separate from the console and packaged in a sterile package. The cartridge is intended to be used for one single treatment, and not to be reused. The cartridge is inserted into the pump console  110  by threading the tubing loops  121  in the blood passage  108 , and ultrafiltrate discharge tubing  119  over the rims of roller pumps  122  and  126 , respectively. As pumps  122  rotate, they slidably engage the tubing and force blood and ultrafiltrate fluids to move through the cartridge fluid passages. Microprocessor pump drivers (not shown) control the flow rate of the blood and ultrafiltrate through the cartridge. The pump drivers are part of console  110  and are controlled by a microprocessor controller  128  (FIG. 3) within pump console  110 . Electronic key  130  is supplied with the circuit in the same sterile package and inserted into the slot  125  in console  110  prior to treatment.  
         [0054]    The tubing of the blood circuit cartridge  109  may be mounted in a molded-plastic housing  123  that fits into a recess in the surface of console  110  and snaps into console  110  with latches  124 . A blood withdrawal pressure sensor  112  is mounted to an inside surface of the cartridge housing  123 . A pressure sensor  113  for the blood return tube  105  and an ultrafiltrate pressure sensor  114  are mounted to an inside surface of the second cartridge housing  129 . Blood pressure sensors  112  and  13  and ultrafiltrate pressure sensor  114  include transducers that convert pressures into electrical signals carried by signal wires  131  that are connected to microprocessor controller  128  in console  110 .  
         [0055]    In the preferred embodiment of the invention, sensors  112 ,  113  and  114  are MPX2300D sensors manufactured by Motorola. Filter  111  in the preferred embodiment is a custom-made filter made by Minntech of Minnesota. The filter uses polysulfone hollow fiber available from Minntech or Fersenius of Germany. Pump console  110  in the preferred embodiment is manufactured by Intellicardia.  
         [0056]    [0056]FIG. 2 is a schematic diagram of the blood and filtrate flow through the ultrafiltration system  100 . The system symbolically depicted in the FIG. 2 is designed primarily to perform SCUF (Slow Continuous Ultrafiltration) but can be easily converted for other RRT (Renal Replacement Therapy) modalities. The second hemofilter port  153  is plugged for SCUF. If dialysis is desired, a source of dialysate fluid can be connected to this port. Dialysis fluid will circulate through the filter casing and interface with blood through the hollow fiber membrane. This way clearance can be obtained via the diffusion of solute. For this mode, dialysate may need to circulate in the direction opposite to blood. This can be achieved by reversing the pump  126 .  
         [0057]    Alternatively access port  152  in the circuit tubing  108  can be used to infuse the replacement solution. Ultrafiltration rate can be increased proportionally by speeding up the pump  122 . This way clearance can be obtained by convective transport of solute with ultrafiltrate. Similarly, the post-filter port  151  can be used to infuse the replacement solution if desired. With these simple additions well known in the field of RRT, the described apparatus can be used to perform dialysis and hemofiltration.  
         [0058]    Regardless of the RRT modality desired, the basic principles of the apparatus design remain the same. Blood that is withdrawn from the patient flows into the wiwthdrawal tubing  104  and enters the blood passage  108  of the cartridge  123 . Blood travels inside the hollow fibers through the filter  111  and is returned to the patient via the return tube  105 . Prior to return, blood enters the pressure sensor  113  mounted on cartridge  129 . Ultrafiltrate, effluent or dialysis solution passes through the filter casing surrounding the blood filled hollow fibers. Pump  122  generates the flow. Pump segment tubing loops  121  are attached to cartridges  123  and  129  to assist loading of pumps and prevent tubes from kinking. In the preferred embodiment, ultrafiltrate line pressure sensor  114  is integrated into the same cartridge as the blood return sensor  113 . Pressure sensors  112 ,  113  are integral to the blood passage  108  in the Cartridges  123  and  129 . These sensors are disposed in blood passage  108 , such that a diaphragm of the sensor, which is the device that is in fluid contact with the load and directly responds to the blood pressure, is adjacent the blood passage. The diaphragm does not form stagnant areas in the passage. Similarly, pressure sensor  114  (which also includes a diaphragm in fluid contact with the filtered fluid) for the ultrafiltrate is integrally formed in the filtrate tubing  119  between the filter  111  and the ultrafiltration bag  120 . Pressure sensors  112 ,  113  and  114  are included in the disposable cartridge and are intended for one-time use. These pressure sensors each have a generally straight and hollow fluid passage that is coupled to the blood or filtrate tubing in the cartridge. The passages in the sensors are contiguous with the blood and ultrafiltrate passage of the cartridge.  
         [0059]    The fluid flow passage in each sensor includes a peripheral wall, a pressure sensing diaphragm that is relatively small compared to the passage. As blood or ultrafiltrate flows across the diaphragm, the pressure of the flow displaces the diaphragm. This diaphragm displacement is converted by a mechanical-to-electrical transducer in the sensor to an electrical signal, e.g., a voltage level, that is indicative of the pressure of the flow. The electrical signal is output by the sensor to the pump console  110  through an electrical signal line, e.g., a wire  131 . A microprocessor controller  128  in console  110  receives the pressure signals via the lines  131  and determines the pressure level of the blood or ultrafiltrate in the blood or ultrafiltrate passage in which the associated sensor is positioned.  
         [0060]    Preferably, the memory device of the present is a serial EEPROM. The memory device can be integrated into one of the set components that has an electric connection to the console such as a pressure, blood leak, blood oxygen saturation, blood hematocrit or other sensor. Alternatively, the memory device can be a separate device, such as a key or a card, that is inserted into a slot on the faceplate of the machine. Such a device is available off shelf from Datakey, Inc., a leading provider of token-based systems and technology used by worldwide customers to record, store and transmit electronic information. Datakey products, such as “code keys” and “smart cards”, are inexpensive, tested, and made in robust packages that can be sterilized and packaged together with the disposable ultrafiltration set. These products also include build in encryption and encoding that allow secrecy desired by the set manufacturer and the protection of a patient&#39;s privacy.  
         [0061]    [0061]FIG. 3 illustrates one preferred embodiment of the memory device  130  used in the present invention. Memory device  130  is a code key ROM that is either integrated into the housing  123  of the pressure sensor  112 , integrated into housing  129  of pressure sensors  113  and  114 , or be a separate device which plugs into slot  125  in the faceplate  127  of the ultrafiltering device. Pressure sensors  112 ,  113  and  114  are conventional bridge type strain gauge devices.  
         [0062]    The Code key  130  contains a serial EEPROM (FIG. 4) with the serial number, date of manufacture and other relevant information stored in the device. The preferred embodiment of the code key is a SlimLine Data Carrier from Datakey of Minnesota. The key is an economical, low-cost token with 1K, 4K, and 16K-bit serial memories.  
         [0063]    Each SlimLine token contains a serial I/O, read/write memory in either Microwire™ (LCS) or  12 C™ (SDD) that holds more information than common magnetic strip cards. Data stored in the device can be read, written, and erased via a simple interface to host hardware with which the device is used. The SlimLine tokens can be programmed directly by the host&#39;s microprocessor (e.g., microprocessor controller  128 ) or accessed through a conventional RS232 reader/writer device. The key is nonvolatile and retains data for 10 years. Importantly, the key is sealed and rugged and can withstand sterilization with the rest of the patient circuit.  
         [0064]    Code key  130 &#39;s serial EEPROM has following inputs and outputs:  
         [0065]    CS—chip select  
         [0066]    CLK—clock input  
         [0067]    DI—data input  
         [0068]    DO—data output  
         [0069]    VCC—supply voltage 5 VDC  
         [0070]    VSS—ground  
         [0071]    ORG—organization of the memory array (64×16 or 128×8)  
         [0072]    RDY/BSY—ready or busy signal  
         [0073]    Referring, by way of example, to pressure sensor  112  shown in FIG. 3, both pressure sensor  112  and EEPROM device  130 &#39;s wires  132  and  132 , respectively, are bundled into the same cable  133 . The plug in connector  134  is located on the front panel of the console  110 . Signals from both the sensor  112  and the code key  130  are in electronic communication with the microprocessor controller  128  via standard A/D and digital I/O means.  
         [0074]    [0074]FIG. 4 shows EEPROM device  130  that is used with the preferred embodiment of the invention. The device is preferably an 8 pin DIP chip  135 . Internally it consists of a memory array  137 , address decoder  139 , data register  141 , output buffer  143 , mode select logic  145  and the clock generator  147 .  
         [0075]    In the initial release of the ultrafiltration set, the code key  130  is programmed with the following information at the factory:  
         [0076]    Calibrations: Pressure transducer gains and offsets. 3 offsets+3 gains (Total 6-16 bit words);  
         [0077]    Date of manufacture (1-16 bit word);  
         [0078]    Number generated on Key code  130  that fits with a proprietary algorithm. If the number does not compute, key  130  does not allow the use of the disposable circuit. Set forth below is the algorithm used with the preferred embodiment of the invention:  
         [0079]    CODE=A B CD E F G H (1-16 bit word)  
         [0080]    The code is generated as follows A, B, C, H are random integer numbers between 1 and 9. ((A-B-B)-C-H)=EFG  
         [0081]    If (((A-B-B)-C-H)=EFG) key is accepted, else it is rejected.  
         [0082]    During operation, the ultrafiltration circuit  109  is connected to console  110 . Console  110  will not proceed to priming or treatment of the circuit  109  until a) the memory key  130  is connected to microprocessor controller  128  and b) the memory code is successfully read and analyzed by microprocessor controller  128 . When the key  130  is connected, certain data is read into microprocessor controller  128 &#39;s memory and analyzed. The date and time of  130 &#39;s key connection is written to key  130  when console  110  enters an operating mode that affects the life of disposable circuit  109 . Thereafter, disposable circuit  109  is initialized. The user has 24 hours to use the circuit for treatment. During operation of the ultrafiltration machine, the key initialization time is periodically compared to the current time. If more than 24 hours have elapsed, treatment will continue but cannot be restarted. Any attempt to start the treatment with the key that has been active for more than 24 hours will result in a warning message to the user.  
         [0083]    During treatment, useful information may be collected by microprocessor controller  128  and stored in the key  130 . Key  130  can be later shipped back to the manufacturer so that the information can be used to collect valuable statistics or help troubleshoot failures. Alternatively, key  130  can be retained by the medical institution using it as a part of the patient history and the information later transferred to a central database for storage and analysis.  
         [0084]    During the operation of disposable circuit  109 , the following information is stored in key  130 :  
         [0085]    1) Settings used+duration of use for each setting (10-2-16 bit words);  
         [0086]    2) Last technical  20  alarm codes generated (20-16 bit words);  
         [0087]    3) Number of patient alarms generated. Each time one occurs, the counter for that alarm is incremented. (15-16 bit words);  
         [0088]    4) Number of minutes the key battery was used+duration of use (up to 10 occurrences) (10-16 bit words);  
         [0089]    5) Condition of battery during start up—voltage level. (1-16 bit word);  
         [0090]    6) Number of times machined was turned on/off with the same circuit. (1-16 bit word);  
         [0091]    7) Number of times manual mode was used. (1-16 bit word);  
         [0092]    8) Number of times run mode was used. (1-16 bit word);  
         [0093]    9) Number of times prime mode was used. (1-16 bit word);  
         [0094]    10) Number of times stop mode was used. (1-16 bit word);  
         [0095]    11) Serial number of SAFE console (1-16 bit word);  
         [0096]    12) Hours of operation—can be duplicated in device embedded software in (1-16 bit word);  
         [0097]    13) Revision of embedded software (1-16 bit word);  
         [0098]    14) Circuit board revision (1-16 bit word);  
         [0099]    15) Date that the treatment started—this is used to stop treatment after 24 hours. If the number of hours of use exceeds 24 hours or a day has elapsed, circuit  109  is rejected by microprocessor controller  128 . (1-16 bit word); and  
         [0100]    16) Number of times key  130  was inserted (1-16 bit word)  
         [0101]    Information stored in key  130  can also contain data entered by the operator using the device keyboard. This information can include:  
         [0102]    Patients age, sex and weight;  
         [0103]    Diagnosis;  
         [0104]    Any medication administered before and during treatment;  
         [0105]    Blood pressure and blood gases.  
         [0106]    At the beginning of treatment, a microprocessor controller  128  in console  110  can interrogate key  130  and determine if the shelf life of the disposable set  109  has expired. If so, microprocessor controller  128  will inform the user and will refuse to start treatment.  
         [0107]    The model number of circuit  109  can help console  110  to setup the correct mode of treatment. For example if the set is designed for CVVH and the user attempts to initiate CVVHD treatment, microprocessor controller  128  will prevent it and inform the user. The model number can also help establish correct treatment settings. If filter  111 , for example, is of pediatric size and the user attempts to set the ultrafiltrate rate to an adult value, microprocessor controller  128  will prevent the change based on the encoded filter model.  
         [0108]    Other important checks can be performed based on the information stored in key  130 . For example the software revision in microprocessor controller  128  in console  110  can be compared to the model or revision of circuit  109 . An older revision of software may not support some features of a new circuit  109 . Key  130  can also be used to activate different software segments included but inactive with simpler and less expensive disposables. Alternatively, key  130  can be loaded at the time of manufacturing with the software and hardware revisions that it is compatible with.  
         [0109]    Although the present invention has been described in terms of a particular embodiment, it is not intended that the invention be limited to that embodiment. Modifications of the disclosed embodiment within the spirit of the invention will be apparent to those skilled in the art. The scope of the present invention is defined by the claims that follow.