Abstract:
A drug infusion assembly comprises a drug delivery device arranged to adhere to a patient&#39;s skin and includes a reservoir that holds the drug, a cannula that delivers the drug to the patient, and a pump that causes the drug to flow to the cannula. The assembly further includes a monitor device for providing information about the operation of a drug delivery device. The monitor device includes a housing arranged to be attached to and detached from the drug delivery device, a sensor that senses the operation of the drug delivery device and generates an activation signal, a clock mechanism that generates a time signal, a memory that receives and stores the activation signal and the time signal and creates an information packet coordinating the time signal and the activation signal, an interrogator that interrogates the memory such that the memory generates a memory signal in response thereto, and a responder that receives the memory signal and generates a response.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a device for sensing medicament dosing in a drug infusion set. In some embodiments it also includes the ability to retain and recall dosing history and to provide tactile feedback to a user reflecting recent dosing activity. In some embodiments it also includes the ability to retain and dosing history and to provide a download of that history to an electronic device such as a computer or a similar device specifically for that purpose. 
         [0002]    The invention relates to a sensing device that is applicable to infusion devices for liquid medicaments in general, but for purposes of example, the use of the device in connection with disposable infusion devices for the administration of insulin in diabetes is described below. 
         [0003]    Glucose is the central source of energy in the human body, and is generated by the digestion of the food, particularly carbohydrates and released into the bloodstream for distribution throughout the body. Insulin is a hormone that allows the glucose in the bloodstream to be absorbed by the cells of the body. A healthy person makes enough insulin for the body&#39;s cells to absorb essentially all the glucose generated by the food that the body digests. Insulin is produced in the pancreas and released into the bloodstream and is present at a low basal level at all times, but is sometimes released in larger bolus amounts in response to or anticipation of a person&#39;s intake of carbohydrates, for example at a meal. 
         [0004]    Diabetes is a disorder of the manufacture and utilization of insulin. It is a huge and growing health problem among virtually all segments of the population. It is an incurable and progressive disease that typically manifests itself in one of two different ways, type 1 diabetes (T1) and type 2 diabetes (T2). In T1 diabetes the patient loses the ability to make insulin at all, generally as a result of destruction of cells of the pancreas. This often happens early in life and was previously sometimes called early onset diabetes. With this type of diabetes, insulin replacement therapy is necessary, and without the administration of insulin the patient dies. 
         [0005]    In T2 diabetes, the patient develops an inability to use insulin efficiently. Often diet and exercise will delay progression, but the disease typically progresses to the stage where it is necessary to administer drugs to increase the body&#39;s production of insulin or the efficiency of use of the insulin present. At some point thereafter, the disease usually progresses to the point that insulin injections are required. 
         [0006]    In both T1 and T2 where insulin injections are required, careful monitoring of the amount and timing of injections is important. Certain insulin analogs have been developed that allow a single or perhaps two daily injections to provide the rough equivalent of the daily basal insulin of a patient without diabetes. However, mimicking the body&#39;s bolus insulin amounts is far more delicate. Bolus administrations of insulin are typically given about half an hour before a meal The amount of insulin that is appropriate varies from one administration to the next depending on the amount and type of the food to be eaten, the amount of exercise that the patient has recently engaged in, the how tired the patient is, and any number of other factors. 
         [0007]    Recent treatment protocols are trending toward a move to earlier treatment of T2 diabetes with insulin, and in more precise and constant monitoring of the blood glucose level of the patient. This protocol is sometimes referred to as Intense Insulin Therapy, or IIT and involves the administration of insulin three or more times per day, or constant administration by a pump. As a result, in addition to the growing problem of diabetes in the population, it is likely that in the future a larger portion of people with diabetes will be treated by the administration of insulin, and IIT will become far more common. 
         [0008]    Administration of insulin has traditionally been accomplished using a syringe. Recently, needle carrying pen-like devices have also been employed for this purpose. Both forms of insulin administration require the patients to stick themselves each time they inject insulin, often many times a day. Additionally, the act of injecting themselves or having a helper inject them is socially awkward for the person with diabetes. Thus, these traditional forms of insulin administration have been a rather pervasive intrusion in the lives and routines of the patient&#39;s who have had to adopt and employ them. If the social awkwardness results in a patient skipping administrations, that may be detrimental to control of the disease 
         [0009]    More recently, insulin pumps attached by tubing to an infusion set mounted on the patient&#39;s skin have been developed as an alternative form of insulin administration. Such pumps may be controlled by a programmable remote electronic system employing short range radio communication between a control device and electronics that control the pump. While such devices may involve fewer needle sticks, they are expensive to manufacture, complex to operate and cumbersome and awkward to wear. Further, the cost of such devices can be many times the daily expense of using a traditional injection means such as a syringe or an insulin pen. 
         [0010]    Devices of the type mentioned above also require a significant amount of training to control and use. Great care in programming the devices is required because the pumps generally carry sufficient insulin to last a few days and improper programming or operation of the pumps can result in delivery of an excessive amount of insulin which can be very dangerous and even fatal. 
         [0011]    Many patients are also reluctant to wear a pump device because they too are generally socially awkward. The devices are generally quite noticeable and can be as large as a pager. Adding to their awkwardness is their attachment to the outside of the patients clothes and the need for a catheter like tubing set running from the device to an infusion set located on the patient&#39;s body. Besides being obvious and perhaps embarrassing, wearing such a device can also be a serious impediment to many activities such as swimming, bathing, athletic activities, and activities such as sun bathing where portions of the patient&#39;s body are necessarily uncovered. 
         [0012]    In view of the above, a more cost effective and simple device has been proposed whereby an injection system is discreetly attached directly to the skin of the patient. The device may be attached to the patient under the patient&#39;s clothing to deliver insulin into the patient by the manual pumping of small doses of insulin out the distal end of a temporarily indwelling cannula that is made a part of the pump device. The cannula may be made a part of the drug delivery device before, during or after the attachment of the drug delivery device to the skin of the patient. The device may be made quite small and, when worn under the clothes, entirely unnoticeable in most social situations. It may still carry sufficient insulin to last a patient several days. It can be colored to blend naturally with the patient&#39;s skin color so as not to be noticeable when the patient&#39;s skin is exposed. As a result, insulin for several days may be carried by the patient discreetly, and conveniently applied in small dosages after only a single needle stick. For a more complete description of devices of this type, reference may be had to co-pending application Ser. No. 11/906,130, filed on Sep. 28, 2007 for DISPOSABLE INFUSION DEVICE WITH DUAL VALVE SYSTEM, which application is owned by the assignee of this application and hereby incorporated herein by reference in its entirety. 
         [0013]    As noted above, current medical protocol is trending toward IIT where frequent and precise insulin administration is used. Also as noted above, each bolus insulin dosage is unique and will vary from one to the next. It is therefore very important to keep track of the timing and amount of each dosage. Patients are often advised to keep journals whereby they record each insulin administration and their blood glucose in frequent intervals to help carefully monitor their treatment. 
         [0014]    Where the administration of the dose of insulin involves loading a syringe or dialing an amount on an insulin pen, and injecting oneself with the dose, the patient is unlikely to forget that they had administered the dose or the amount of the dose. Likewise if a complex electronic unit is controlling an insulin pump, one of its electronic functions can be to recall each dose and display the results on the individual remote unit. However, the very simple and discreet nature of the disposable unit described above makes it more likely that the patient may not remember the details of the last insulin administration. The fact that the device is worn on the patient&#39;s body in an unobtrusive manner also makes a visual display less useful. It is very likely that the patient will be wearing the device where they cannot easily see it. Finally, in furtherance of the goal of making the treatment less of an unpleasant intrusion into the daily life of the patient, it would be helpful to have a means of keeping a record of insulin treatment without the need to carry and maintain a journal. 
         [0015]    Thus there is a need for a sensing device for use with an attached drug delivery device that can sense dosing by that device, and respond to a query from a user with information regarding recent dosing activity. There is a need for such a device that can provide that response in a tactile form that may be sensed by the user without the need to see the sensing device. There is a need for such a device to be discreet to be consistent with the ability of such a drug delivery device to be discreet and unobtrusive. Finally it would be useful if such a device could store the history of the insulin administration over a significant period of time and provide that information later to a physician or patient. 
         [0016]    As mentioned previously, the administration of insulin is used here for exemplary purposes. However the administration of any liquid medicament, particularly where relatively frequent or constant administration is indicated, would be greatly aided by this invention. For example, where administration of pain medication for a chronic situation is required, an unobtrusive infusion device would be helpful, and a method of sensing and later providing information concerning recent dosing or long term dosing history would be very helpful. In some chemotherapeutic regimes, a similar system would be very useful. The invention is not limited by the exemplary method described herein except as explicitly stated in the claims. 
       SUMMARY OF THE INVENTION 
       [0017]    In one embodiment, the invention provides a monitoring device for providing information about the operation of a drug delivery device. The monitoring device comprises a housing arranged to attach to the drug delivery device, a sensor that senses the operation of the drug delivery device and provides operational data indicative of the operation of the drug delivery device, a memory that stores the operational data, and an indication generator that generates a perceptible indication of the operational data. 
         [0018]    The indication generator may be arranged to provide a tactile response to provide the perceptible indication. The tactile response may be a vibratory response. The indication generator may be a motor. The motor may be an electric motor. 
         [0019]    The sensor may comprise an optical sensor and/or a magnetic sensor. The drug delivery device may include a pump that delivers the drug to a patient. For example, the pump may be a mechanical stroke pump and the sensor may sense the strokes of the pump. The monitoring device may further comprise a timer that times a dosing session of the device. 
         [0020]    The drug delivery device may include at least one valve. The operation of the drug delivery device initiates with operation of the at least one valve and the magnetic sensor senses the operation of the at least one valve. The optical sensor senses strokes of the pump. 
         [0021]    The memory may store each pump stroke occurring during a dosing session. The indication generator may generate a perceptible indication of the number of pump strokes occurring during a last dosing session. The memory may store operational data for a number of dosing sessions in a history file. The monitoring device may further include an interface arranged to provide the history file to an external reader. The interface may comprise a USB interface. 
         [0022]    In another embodiment, a monitor device provides information about the operation of a drug delivery device. The monitor device comprises a sensor that senses the operation of the drug delivery device and generates an activation signal, a clock mechanism that generates a time signal, a memory that receives and stores the activation signal and the time signal and creates an information packet coordinating the time signal and the activation signal; an interrogator that interrogates the memory such that the memory generates a memory signal in response thereto, and a responder that receives the memory signal and generates a tactile response. 
         [0023]    In another embodiment, a monitor device provides information about the operation of a drug delivery device. The drug delivery device includes a mechanical stroke pump that delivers the drug to a patient and at least one valve, the operation of which initiates operation of the drug delivery device. The monitor device comprises a housing arranged to attach to the drug delivery device, a timer that times a dosing session, a magnetic sensor that senses the operation of the at least one valve, an optical sensor that senses operation of the pump to provide operational data, a memory that stores the operational data provided by the optical sensor during a last dosing session, an interrogator that interrogates the memory such that the memory generates a memory signal in response thereto representing operation of the drug delivery device during a last dosing session, and a responder that receives the memory signal and generates a tactile response. 
         [0024]    In a further embodiment, a drug infusion assembly comprises a drug delivery and a monitor device. The drug delivery device is arranged to adhere to a patient&#39;s skin and includes a reservoir that holds the drug, a cannula that delivers the drug to the patient, and a pump that causes the drug to flow to the cannula. The monitor device provides information about the operation of the drug delivery device. The monitor device comprises a housing arranged to be attached to and detached from the drug delivery device, a sensor that senses the operation of the drug delivery device and provides operational data indicative of the operation of the drug delivery device, a memory that stores the operational data, and an indication generator that generates a perceptible indication of the operational data. 
         [0025]    In a still further embodiment, a drug infusion assembly comprises a drug delivery device arranged to adhere to a patient&#39;s skin and includes a reservoir that holds the drug, a cannula that delivers the drug to the patient, and a pump that causes the drug to flow to the cannula. The assembly further includes a monitor device for providing information about the operation of a drug delivery device. The monitor device includes a housing arranged to be attached to and detached from the drug delivery device, a sensor that senses the operation of the drug delivery device and generates an activation signal, a clock mechanism that generates a time signal, a memory that receives and stores the activation signal and the time signal and creates an information packet coordinating the time signal and the activation signal, an interrogator that interrogates the memory such that the memory generates a memory signal in response thereto, and a responder that receives the memory signal and generates a response. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further features and advantages thereof, may best be understood by making reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify identical elements, and wherein: 
           [0027]      FIG. 1  is a perspective view of an infusion device which may be employed in an assembly embodying the present invention; 
           [0028]      FIG. 2  is another perspective view of the infusion device of  FIG. 1  shown with a deployed cannula; 
           [0029]      FIG. 3  is an exploded perspective view of the device of  FIG. 1 ; 
           [0030]      FIG. 4  is a sectional view, in perspective, to an enlarged scale, taken along lines  4 - 4  of  FIG. 1 , showing the actuation linkages of the device of  FIG. 1  prior to medicament dosage delivery; 
           [0031]      FIG. 5  is another sectional view, in perspective, to an enlarged scale, taken along lines  5 - 5  of  FIG. 2 , showing the actuation linkage operation of the device of  FIG. 1  during medicament dosage delivery; 
           [0032]      FIG. 6  is another sectional view similar to that of  FIG. 5 , in perspective, to an enlarged scale, showing the actuation linkage operation of the device of  FIG. 1  immediately after dosage delivery; 
           [0033]      FIG. 7  is a schematic representation of the valves and pump of the device of  FIG. 1  between medicament dosage deliveries and during the filling of the pump with the medicament; 
           [0034]      FIG. 8  is another schematic representation of the valves and pump of the device of  FIG. 1  during medicament dosage delivery; 
           [0035]      FIG. 9  is a sectional view, in perspective, to an enlarged scale, showing the configuration of the valves of the device of  FIG. 1  during pump filling and prior to medicament dosage delivery; 
           [0036]      FIG. 10  is another sectional view, in perspective, to an enlarged scale, showing the configuration of the valves of the device of  FIG. 1  during dosage delivery; 
           [0037]      FIG. 11  is a perspective view of an infusion assembly embodying the present invention showing the infusion device of  FIG. 1  and a dosage monitor releasably attached thereto in accordance with aspects of the present invention; 
           [0038]      FIG. 12  is a perspective view of the dosage monitor of  FIG. 11 ; 
           [0039]      FIG. 13  is a bottom plan view of the dosage monitor of  FIG. 11 ; 
           [0040]      FIG. 14  is a perspective view taken along lines  14 - 14  of  FIG. 11 ; 
           [0041]      FIG. 15  shows a portion of the perspective view of  FIG. 14  illustrating a magnet carried by a valve actuation button of the infusion device and a magnetic sensor of the dosage monitor in accordance with aspects of the present invention; 
           [0042]      FIG. 16  is a perspective view taken along lines  16 - 16  of  FIG. 11 ; 
           [0043]      FIG. 17  shows a portion of the perspective view of  FIG. 11  illustrating a reflective surface of a pump actuation button of the infusion device and a light source and an optical sensor of the dosage monitor in accordance with additional aspects of the present invention; 
           [0044]      FIGS. 18-21  are bottom views, with portions cut away, illustrating the sequential operation of the actuator buttons of the infusion device for corresponding magnetic and optical sensing according to aspects of the invention; 
           [0045]      FIG. 22  is a schematic block diagram of an infusion device dosage monitor embodying the present invention; and 
           [0046]      FIG. 23  is flow diagram illustrating the operation of the dosage monitor for incrementing a dosage counter and performing dosage amount read-back. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]    Referring now to  FIGS. 1 and 2 , they are perspective views of an infusion device  110  which may be used in an assembly embodying various aspects of the present invention. More particularly, the device  110  may receive a monitoring device thereon embodying the present invention and described subsequently to form an infusion assembly capable of providing a drug, such as insulin, to a patient and to report to the patient information pertaining to the drug delivery. 
         [0048]      FIG. 1  shows the device prior to receiving and thus without a cannula while  FIG. 2  illustrates the device after having received a cannula  130  that has a distal end  131 . As may be seen in both  FIGS. 1 and 2 , the device  110  generally includes an enclosure  112 , a base  114 , a first actuator control button  116 , and a second actuator control button  118 . 
         [0049]    The enclosure  112 , as will be seen subsequently, is formed by virtue of multiple device layers being brought together. Each layer defines various components of the device such as, for example, a reservoir, fluid conduits, pump chambers, and valve chambers, for example. This form of device construction results in a compact design and enables manufacturing economy to an extent that the device is disposable after use. 
         [0050]    The base  114  preferably includes a pad  115  attached to the base  114 . The pad  115  has an adhesive coating  117  on the side thereof opposite the base  114  to permit the device to be adhered to a patient&#39;s skin. 
         [0051]    The device  110 , as will be seen herein after is first adhered to the patient&#39;s skin followed by the deployment of the cannula  130  thereafter. However, it is contemplated herein that various aspects of the present invention may be realized within a device that may alternatively be mated with a previously deployed cannula assembly. 
         [0052]    The actuator buttons  116  and  118  are placed on opposites sides of the device  110  and directly across from each other. This renders more convenient the concurrent depression of the buttons when the patient wishes to receive a dose of the liquid medicament contained within the device  110 . This arrangement also imposes substantially equal and opposite forces on the device during dosage delivery to prevent the device from being displaced and possibly stripped from the patient. As will be further seen hereinafter, the concurrent depression of the buttons is used to particular advantage. More specifically, the actuator button  116  may serve as a valve control which, when in a first position as shown, establishes a first fluid path between the device reservoir and the device pump to support pump filling, and then, when in a second or depressed position, establishes a second fluid path between the device pump and the device outlet or distal end of the cannula to permit dosage delivery to the patient. As will be further seen, a linkage between the control actuator buttons  116  and  118  permits actuation of the device pump with the actuator control button  118  only when the second fluid path has been established by the first actuator control button  116 . Hence, the first actuator control button  116  may be considered a safety control. 
         [0053]    The actuator buttons  116  and  118  are preferably arranged to require a complete through of their travel to achieve activation of the device pump and thus dosage delivery. This, together with the sudden release of resistance to actuator advancement creates a snap action that provides an advantage in positively knowing that dosage delivery has occurred and that no less than a full dose has been delivered. For more description regarding this feature, reference may be had to co-pending application Ser. No. 11/906,102, titled DISPOSABLE INFUSION DEVICE WITH SNAP ACTION ACTUATION, which application is owned by the assignee of this application and is incorporated herein by reference in its entirety. 
         [0054]    As may be noted in  FIG. 1 , the device  110  includes a cavity  120  that is arranged to receive a cannula assembly  122  ( FIG. 2 ) from which the cannula  130  extends. When the cannula is deployed, the outlet  124  of the device  110  is placed in fluid communication with the cannula  130  by a cannula carrier  128  of the cannula assembly  122  that carries the cannula. When thus deployed, the cannula  130  extends from the base  114  of the device  110  to beneath the skin of the user. 
         [0055]    As may further be noted in  FIGS. 1 and 2 , the enclosure  112  of the device  110  includes a pair of pockets  140  and  142  on opposite sides of the second actuator button  118 . A similar pair of pockets, not seen in the figure, are also provided on opposite sides of the first actuator button  116 . These pockets are used to receive corresponding projections of a cannula placement assembly for releasably joining the cannula placement assembly to the device  110  to support cannula deployment as will he described subsequently. Such a cannula placement assembly is fully described in co-pending application Ser. No. 12/147,295, filed on Jun. 26, 2008 for DISPOSABLE INFUSION DEVICE WITH AUTOMATICALLY RELEASABLE CANNULA DRIVER, which application is owned by the assignee of the present invention and hereby incorporated herein by reference. As described therein, upon cannula deployment, the cannula placement assembly is automatically released from the device by the driver projections being forced from the pockets. 
         [0056]    Referring now to  FIG. 3 , it is an exploded perspective view of the device  110  of  FIG. 1 . It shows the various component parts of the device. The main component parts include the aforementioned device layers including the base layer  160 , a reservoir membrane  162 , an intermediate layer  164  and a top body layer  166 . As may also be seen in  FIG. 3 , the base layer  160  is a substantially rigid unitary structure that defines a first reservoir portion  168 , a pump chamber  170 , and a valve chamber  190  that receives a shuttle bar  200  of a shuttle valve  210 . A reservoir membrane layer  162  is received over the reservoir portion  168  to form an expandable/deflatable reservoir of the device  110 . The base layer  160  may be formed of plastic, for example. The base and the top body layer may be joined together, trapping the intermediate layer there between by any means such as with screws, ultrasonic welding or laser welding. 
         [0057]    The valve chamber  190  is arranged to receive a valve shuttle bar  200  carried by and extending from the first actuator button  116 . A series of O-rings, to be described subsequently, are seated on the shuttle bar  200  to form first, second, and third valves. The actuator button  116  also carries a first linkage portion  240  of the linkage that permits actuation of the device pump with the actuator control button  118  only when the second fluid path has been established by the first actuator control button  116 . The first linkage portion  240  is received within a suitably configured bore  270  formed in the base layer  160  and will be described subsequently. 
         [0058]    The pump actuator button  118  is arranged to be linked to a pump piston  300  and a second linkage portion  340  to interact with the first linkage portion  240 . The pump piston  300  is arranged to be received within the pump chamber  170  and the second linkage portion  340  is arranged to be received within the bore  270  for interacting with the first linkage portion  240 . O-rings are seated on the piston  300  to provide a seal against leakage and to prevent external contaminants from entering the piston chamber. 
         [0059]    The intermediate layer  164  may be a generally resilient member and received on the base layer  160  to cover channels scribed in the base layer as a type of gasket to form fluid channels  380  that serve to conduct the medicament from the reservoir to the device outlet and to the distal end  131  ( FIG. 2 ) of the cannula  130 . Springs  410  are arranged to spring load the actuator buttons  116  and  118  away from each other. 
         [0060]    The reservoir membrane  162  is formed of flexible membrane material and is received over the reservoir portion  168  to form the reservoir of the device  110 . A rigid plate  420  is arranged to be adhered to the reservoir membrane  162  of the reservoir. Because the membrane  162  is flexible, it will move as the reservoir is filled and emptied. The rigid plate  420  will then move with it. The plate  420  includes an eyelet  422  dimensioned to receive an elongated web  424  that forms a part of a medicament level indicator. The web  424  carries an indicator line or feature  426  that may be read through a window  428  of the device top most panel  440 . 
         [0061]    Another component of the device  110  is a translucent window  450  that is received on the underside of the base  160 . As will be seen hereinafter, the window forms a part of a prime indicator. It is formed of a transparent material such as glass or transparent plastic and has a roughened surface rendering it translucent. However, when it is covered with or at least wetted by liquid medicament, it is rendered essentially transparent creating a visually obvious condition and, for example, permitting indicia to be seen beneath it indicating that the conduit to the device outlet is primed and ready to deliver fixed doses of medicament when desired. 
         [0062]      FIGS. 4-6  show details of the operation of the linkage that permits actuation of the device pump with the actuator control button  118  only when the second fluid path from the reservoir to the outlet has been established by the first actuator control button  116 . The linkage has been given the general reference character  150 . 
         [0063]    As may be seen  FIG. 4 , the first actuator button  116  has an extension  152  that terminates in a block  154 . The block  154  has a first ramp surface  156  and a second ramp surface  158 . When the device  110  is actuated, the button  116  is concurrently depressed with pump button  118 . It and its extension  152  and block  154  are free to move to the right. As seen in  FIGS. 4 and 5 , the pump actuator button  118  has parallel extensions  250  and  252  which are joined and separated be a rod member  254 . The extensions  250  and  252  are pivotally mounted to pivot about a pivot point  256 . Another extension  260  of the pump actuator button  118  spring biases the extensions  250  and  252  as shown in  FIG. 4 . As seen in  FIG. 4 , the extensions  250  and  252  abut an abutment  262  which they must clear to enable the actuator  118  to be moved to the left. As shown in  FIG. 5 , as the button  116  is depressed, its extension  152  moves to the right causing the first ramp surface  156  to engage the rod member  254 . Continued movement of the button causes the rod member  254  to ride up the first ramp surface  156  which in turn causes the extensions  250  and  252  to begin to move slightly to the left and bend upward against the loading of extension  260 . Eventually, the rod member  254  rides up the length of the first ramp  156  and down the second ramp  158  causing the extensions  250  and  252  to clear the abutment  262  and continue their travel to the left until the extensions are received on the opposite side of the abutment as shown in  FIG. 6  The pump button  116  has now been fully depressed to deliver a dose of measured medicament. When the ends of extensions  250  and  252  totally clear the abutment  262 , they will snap behind the abutment  262  as shown in  FIG. 6  and become temporarily locked. Meanwhile, the rod member  254  has traversed all the way down the second ramp surface  158 . The buttons  116  and  118  are now fully depressed. 
         [0064]    Hence, from the above, it may be seen that the pump button  118  could not at first move freely while the first actuator button  116  which operates the valves could. As a result, the pump actuation lags behind the valve actuation. This enables the device outlet to be sealed from the reservoir and the pump connected to the outlet before the pump is permitted to pump any medicament to the outlet. Hence, the device establishes a medicament delivery flow path to the cannula before the pump is able to begin pumping the medicament to the patient. Thus, it is assured that there is never an open unobstructed pathway between the reservoir and the fluid outlet. Also, by assuring that the pump only draws fluid from the reservoir when the pathway to the outlet is sealed off, it is also assured that a precise amount of fluid is moved with each pump cycle. This operation is completely timed by the linkage just described and occurs quickly, appearing to the patient that both actuator buttons are moving at the same rate. 
         [0065]    When the extensions  250  and  252  of the pump button clear the abutment  262 , they become locked in a snap action. This provides positive feedback to the patient that a dosage of medicament was delivered as desired. It also causes a full dose to be delivered. By virtue of the snap action of the pump actuator, only full doses may be administered. 
         [0066]    When the medicament has been delivered, the spring loading of the actuator buttons returns the buttons to their first or initial position. During this time, the same timing provided by the block  154  is used for recharging the pump. More specifically, ramp  158  unlatches the ends of extensions  250  and  252  by lifting rod member  254 . While the extensions  250  and  252  are being lifted by the ramp  158 , the valve control button  116  is returning to the left to cause the outlet to be disconnected from the pump before the reservoir is reconnected to the pump for charging, thus sealing the outlet from both the pump and the reservoir before the reservoir is connected to the pump for recharging. This assures that the pump does not pull medicament from the patient but only from the reservoir. As the pump returns, a full dose of the medicament is drawn up into the piston chamber  170  to ready the device for the next dosage delivery. 
         [0067]    Referring now to  FIGS. 7 and 8 , they are schematic representations of the valves and pump of the device of  FIG. 1  between medicament dosage filling ( FIG. 7 ) and medicament dosage delivery ( FIG. 8 ) As may be seen in  FIGS. 7 and 8 , the device  110  further includes a reservoir  222 , a pump  224 , and the cannula  130 . The reservoir  222  may be formed as shown in  FIG. 3  by the combination of the device base  160  and the flexible membrane  162 . The device further includes the shuttle valve  210  including shuttle bar  200 . The shuttle bar  200  is shown within the valve chamber  190 . The shuttle bar  200  and O-rings  214  and  216  form a first valve  212 , shuttle bar  200  and O-rings  220  and  222  form a second valve  234  and shuttle bar  200 , O-ring  226  and a bypass channel  186  form a third valve  224 . Although O-rings are used herein to form seals, other types of valve construction may employ forms of seals other than O-rings without departing from the invention. 
         [0068]    The pump piston  300  is within the piston camber  170  to form a piston pump  172 . The actuator control button  218  is directly coupled to and is an extension of the pump piston  226 . It may also be noted that the actuator buttons  116  and  118  are spring loaded by springs  117  and  119 , respectively. The springs are provided for returning the actuator buttons to a first or start position after a dosage is administered. 
         [0069]    A fluid conduit  182  extends between the reservoir  180  and the valve  212 . An annular conduit  192  extends between the O-rings  216  and  226 , and an annular conduit  194  extends between the O-rings  226  and  220 . A fluid conduit  184  provides a fluid connection between the reservoir  180  and the annular conduits  192  and  194  depending upon the position of the shuttle valve  210 . Also illustrated in  FIG. 7  is the linkage  150  that assures that the shuttle valve  210  is actuated before the piston pump  172  is actuated to provide a dose of medicament. 
         [0070]    In  FIG. 7 , the valves are shown in a first configuration immediately after having returned to their first position following a dosage delivery. After the return of the valves, the linkage  150  permits the pump actuator  118  and piston  300  to return for refilling the pump chamber  300  in ready for the next medicament dosage delivery. During their return, the medicament flows as indicated by arrows  202  from the reservoir  180 , through the conduit  182 , through the annular channel  192 , through conduit  184 , and into the pump chamber  170 . 
         [0071]    As may be noted, when in the first position, the valves  218  and  224  isolate the outlet  124  from both the reservoir  180  and the piston pump  118 . Having two such valves isolate the outlet  124  when the valves are in the first configuration provides an added degree of safety from medicament being inadvertently delivered to the patient between dosage deliveries. For example, this provides additional safety that the liquid medicament is not accidentally administered to the patient notwithstanding the inadvertent application of pressure to the reservoir. In applications such as this, it is not uncommon for the reservoir to be formed of flexible material. While this has its advantages, it does present the risk that the reservoir may be accidentally squeezed as it is worn. Because the valves  118  and  124  isolate the outlet  124  when the valves are in their first configuration, this redundant protection assures that pressure, accidentally applied to the reservoir, will not cause the fluid medicament to flow to the cannula. 
         [0072]    In addition to the linkage  150  preventing return of the piston  300  until after the valves return to their first and start positions, the O-rings on the shuttle bar  200  are also spaced apart to insure that the valves  218  and  224  isolate the outlet  124  from the pump  172  and reservoir  180  before the pump is again connected to the reservoir. The O-ring spacing thus effectively forms a second linkage to assure that the cannula  130  is connected to the pump  172  only when a dosage is to be delivered and that it is never connected to the reservoir  180 . 
         [0073]    In operation, the pump chamber  170  is first filled as the actuator button  118  returns to the first position after having just delivered a medicament dosage. In this state, the shuttle valve  210  is set so that the first valve  212  will be open and the second and third valves  218  and  224  will be closed. This establishes a first fluid path indicated by arrows  202  from the reservoir  180  to the pump chamber  170  to fill the piston pump  172 . When the patient wishes to receive another dose of medicament, the actuator buttons are concurrently pressed. The aforementioned linkages, including linkage  150 , cause the first valve  212  to close and the second and third valves  218  and  224  to thereafter open. Meanwhile, actuation of the pump  172  is precluded until the first valve  212  is closed and the second and third valves  118  and  224  are opened. At this point a second fluid path indicated by arrows  204  is established from the pump chamber  170  to the cannula  130 . The medicament is then administered to the patient through the distal end  131  of cannula  130 . 
         [0074]    Once the medication dosage is administered, the piston  330 , and thus the actuator button  118 , is returned under the spring pressure of spring  119  to its initial position. During the travel of the piston back to its first position, a given volume of the liquid medicament for the next dosage delivery is drawn from the reservoir into the pump chamber  170  as described above to ready the device for its next dosage delivery. 
         [0075]    Referring now to  FIG. 9 , it is a sectional view in perspective showing the valve configuration of the device  110  of  FIG. 1  during medicament filling of the pump chamber  170  immediately after a dosage delivery. Here, it may be clearly seen that the first actuator button  116  is directly coupled to the shuttle bar  200  of the valves  212 ,  218 , and  224 . Above the valves are the conduits from the reservoir, from the pump, and to the cannula. More particularly, the conduit  182  is in fluid communication with the reservoir, the conduit  184  is in fluid communication with the pump, and the conduit  124  is in fluid communication with the cannula. The valves are shown with the first valve  212  opened, communicating reservoir conduit  182  with the pump conduit  184  through channel  192 , the second valve  218  closed and blocking the conduit  124  to the cannula, and the third valve  224  closed and blocking both the reservoir conduit  182  and the pump conduit  184  from the cannula conduit  124 . This permits medicament to flow from the reservoir through conduit  182 , through channel  192 , and to the pump chamber  170  through conduit  184  as the actuator button  116  returns to its first position. Hence, the pump chamber is filled and ready for the next dosage delivery. 
         [0076]    Referring now to  FIG. 10 , it is a sectional view in perspective similar to that of  FIG. 9  but showing the valve configuration of the device  110  of  FIG. 1  during medicament delivery. Here, the valves are shown with the first valve  212  closed and blocking the reservoir conduit  182 , the second valve  218  opened permitting the outlet conduit  124  to communicate with the annular conduit  194 , and the third valve  224  opened permitting medicament to flow from the annular conduit  192 , through bypass  186 , and to annular conduit  194 . Thus, medicament is permitted to flow from the pump conduit  184 , through annular conduit  192 , through the bypass  186 , through annular conduit  194 , and into the outlet conduit  124  to administer the fixed volume dosage. As previously mentioned, the O-rings defining the first valve  212 , the third valve  224 , and the second valve  218  are spaced apart so that conduit  182  is blocked before conduits  184  and  124  are connected together through the valves  224  and  218 . 
         [0077]      FIG. 11  is a perspective view of an infusion assembly  500  embodying the present invention showing the infusion device  110  of  FIG. 1  and a dosage monitor  502  releasably attached thereto in accordance with aspects of the present invention. The dosage monitor  502  includes an enclosure  504 . With additional reference to  FIG. 12 , the enclosure  502  has legs  506 ,  508 , and  510 . The legs  506 ,  508 , and  510  are resilient and include feet  512 ,  514 , and  516 , respectively, that grip the device  110  when snap fitted thereon. The dosage monitor  502  further has a user switch button  518  that, as will be seen subsequently, when pressed, causes the monitor  502  to provide the user with information concerning drug delivery to the user by the device  110 . As will also be seen, the information is delivered to the user in the form of a perceptible response. In accordance with this embodiment, the perceptible response is tactile, and more specifically, in the form of a vibration provided by an electric motor. The information delivered may be an indication of the amount of drug delivered to the used during a last dosing session. 
         [0078]      FIG. 13  is a bottom view of the monitor device  502 . Here it may be seen that the monitor housing  504  has a bottom surface  520 . Within the bottom  520  there is a window  523 . As will be seen subsequently, the monitor  502  includes an optical sensor that senses operation of the piston pump. To that end, as will be seen subsequently, the monitor includes a light source, such as an infrared light source, that shines a beam of infrared light through the window  523  onto an extension of the piston pump actuator button  118 . The extension is provided with a reflective coating that passes through the light beam during each stroke of the piston pump. During each such stroke, the infrared light is reflected back from the reflective coating to an infrared light sensor in the monitor  502  and counted. The number of such strokes during a dosing session is stored in memory for later response to a user inquiry. 
         [0079]    In addition to storing the number of drug deliveries during a last dosing session, the monitor may also store a history of dosage deliveries. The dosing history is preferably stored in a non-volatile memory. The history data associated with the operation of the drug delivery device  110  may be transferred to an external device using a plurality of contacts  524  that form an external interface  526 . The external interface  526  may be a USB interface. To that end, the interface  526  of the monitor  502  may be plugged into a USB adapter, such as a USB dongle, that converts the signals on contacts  524  to USB format to connect the monitor to an external device such as, for example, a personal computer. Alternatively, the USB formatting may be accomplished within the monitor  502  so that the signals at contacts  524  are already USB formatted. Once the monitor  502  is interfaced with the computer, the monitor may be powered through the USB port. This eliminates the need for an internal power source for this purpose. The entire contents of the monitor memory may then be downloaded to the computer to render the entire dosing history available. As may further be appreciated by those skilled in the art, the interface  526  may alternatively be coupled to a serial interface for connection to a computer. 
         [0080]    In addition to the optical sensor mentioned above, the sensor of the monitor  502  includes a magnetic sensor  530  which may be seen in the sectional view of  FIG. 14  and the partial view of  FIG. 15 . The magnetic sensor  530  includes a reed switch  532  carried on a circuit board  534  of the monitor  502 . The reed switch  532  is arranged to be above an extension of the first actuator button  116  ( FIG. 11 ). As previously described, the first actuator button  116  configures a valve system for drug delivery prior to actuation of the piston pump with the second actuator button  118 . The first actuator button  116  carries a magnet  536 . When a drug dose is to be delivered, actuation of the first actuator button  116  causes the magnet  536  to translate beneath the reed switch  532 . The reed switch  532  then closes to transition the monitor from a sleep mode to an active mode for sensing the stroke of the piston pump and counting the dosage delivery. 
         [0081]    The sectional view of  FIG. 16  and the partial view of  FIG. 17  illustrate the optical sensor  540 . In these views it may be seen that the optical sensor  540  includes a light source and sensor unit  542  carried on the circuit board  534  of the monitor  502 . As previously mentioned, the light provided and sensed by the light source and sensor unit  542  is in the infrared portion of the spectrum. The infrared light is conducted by a light pipe  522  within a shaft  544  of the drug delivery device  110  and is directed from the window  523  into the valve chamber  190 . As previously mentioned, an extension of the pump actuator button  118  carries a reflective coating that passes through the beam of light with each stroke of the piston pump. The reflected light is then returned through the light pipe  522  to the light source and sensor unit  542  to enable the counting of the piston pump stroke and thus the delivered incremental dose. 
         [0082]    Referring now to  FIGS. 18-21 , they are bottom views, with portions cut away, illustrating the sequential operation of the actuator buttons of the infusion device for corresponding magnetic and optical sensing according to aspects of the invention. In  FIG. 18 , neither actuator button  116  nor actuator button  118  has been depressed. In  FIG. 18  it may be seen that the first actuator button  116  carries magnet  536 . As may be seen in  FIG. 19 , and as previously described, when a dose of drug is to be delivered to the user, the device  110  forces the first actuator button  116  to be depressed before the second actuator button  118  to complete required valve operation. As the actuator button  116  is depressed, the magnet  536  that it carries translates with the actuator button  116 . The magnet  536  moves from its initial position shown in  FIG. 18  to the position shown in  FIG. 19  where it is below and in detectable proximity to the reed switch  532  ( FIGS. 14 and 15 ). The reed switch  532  detects the magnet when the magnet field of the magnet  536  causes the reed switch  532  to close. This causes the monitor to wake from a sleep mode to prepare it for sensing the stroke of the piston pump. 
         [0083]    When the valve operation is completed, the second actuator button  118  is permitted to be depressed. As previously described, the forgoing actuator depressions are completed so quickly that to the user, it appears that the actuator depression of the buttons  116  and  118  is performed essentially simultaneous.  FIG. 20  shows the device  110  as the actuator button  118  is being depressed. As seen in  FIG. 20 , the reflective coating  546  carried on the extension  119  of the actuator button  118  is viewable through the light pipe  522 . In  FIG. 21 , all of the light pipe  522  is adjacent the reflective coating  546  to permit the light from the light source and sensor unit  542  ( FIG. 17 ) to be conducted down the light pipe  522 , reflected from the reflective coating  546 , and returned to the light source and senor unit  542  to cause the delivered incremental dose to be sensed and counted. Now, the actuator buttons  116  and  118  may be returned to their start positions as shown in  FIG. 18 . 
         [0084]      FIG. 22  is a schematic block diagram of an infusion device dosage monitor embodying the present invention. In addition to the user switch  518 , the magnetic sensor  532 , and the optical sensor  540 , the monitor  502  includes a microcontroller or processor  560 , a vibration motor  562 , a light emitting diode (LED)  564 , a real time clock (RTC)  566 , and a power source, such as battery  568 . Also illustrated in  FIG. 22  is an external display  570 , a USB dongle  572 , an external personnel computer (PC)  574 , and a flash memory  576 . The RTC  566  may, instead of being external to the processor  560 , may be embedded within the processor  560 . 
         [0085]    The functions of the magnetic sensor  532 , the optical sensor  540 , and the user switch  518  have already been described. The processor  560  may provide all of the functionality for data acquisition, memory storage, and communication. The RTC  566  is coupled to the processor  560  to enable the processor  560  to keep time. Normally the processor  560  is maintained in a sleep mode to conserve battery power. However, the processor is responsive to interrupts to cause it to wake up and perform its functions. One such interrupt is an overflow interrupt generated by the RTC  566 . This overflow interrupt occurs every 10 seconds. It causes the processor  560  to turn on and increment a seconds register by ten seconds. It then initiates an overflow check to determine if this register is at 60 seconds. If it is, a minute register is incremented and the seconds register is set to zero. In a similar process, the processor  560  checks for minute overflow for incrementing an hours register. After the hours, minutes, and seconds registers have been appropriately updated, the processor returns to sleep. The RTC overflow interrupt is preferably a high priority interrupt to supersede any other triggering event. Since only 5-10 processor clock cycles are required for this time keeping function, the processor has ample time to return to sleep and wait for other triggering events without a perceived lapse in function. 
         [0086]    The vibration motor  563  provides a tactile response when the user requests information concerning drug delivery. The motor  562  may be provided with an offset (eccentric) weight on its output shaft to provide a perceived vibration. The information concerning the drug delivery may, in accordance with this embodiment, be the number of dosage deliveries provided during a last dosing interval timed by a timer  580  of the processor  560 . To that end, the motor  563  may provide pulses of vibrations, each pulse corresponding to one dosage delivery. 
         [0087]    The external display  570  is coupled to the processor  560  via a wireless connection  576  which may be, for example, a wifi connection. The external display  570  may be used to display a history file maintained in a processor memory  578  of the processor  560 . The display may thus be a computer or other device having a wifi receiver and a display. The history file may contain the number of dosage deliveries delivered by the infusion device during each of the dosing sessions occurring over predefined period of time. 
         [0088]    The PC  574  may be coupled to the processor  560  through the USB dongle  572 . The dangle may in turn be coupled to the processor by using the USB contacts  524  ( FIG. 13 ) arrayed on the back surface  520  of the monitor  502 . The PC may also be used for displaying the history file. 
         [0089]    The flash memory  576  may also be used to store the history file. It may be readily removable from the dosage monitor  502  and interfaced with a computer or PDA (not shown) or other similar device for displaying the history file. 
         [0090]      FIG. 23  is a flow diagram illustrating the operation of the dosage monitor for incrementing the dosage counter and performing dosage amount read-back. More specifically, the flow diagram of  FIG. 23  shows how the processor handles interrupts other than time keeping interrupts. 
         [0091]    The process  600  may be initiated with either the user depressing the user switch  518  ( FIG. 1 ) as represented by activity block  602  or the user depressing the first actuator  116  as represented by activity block  604 . Either event wakes the processor  560  from a power conserving sleep mode. 
         [0092]    If the user switch has been depressed, the process advances to activity block  606  to perform the read-back. To that end, the processor will access the memory  578  to obtain the number of drug doses that have occurred in the current dosing session. The processor will then cause the motor  562  to provide a number of vibration bursts that corresponds to the number of drug doses that have been counted during the current dosing session. 
         [0093]    If the interrupt is caused by the depression of the first actuator button  116 , the process advances to decision block  608  to determine if the subsequent depression of the second actuator button  118  ( FIG. 1 ) calling for another dosage delivery occurred during the current dosing session. If it has, the process advances to activity block  610  to increment the dose count. The process then returns and the processor falls back to sleep. 
         [0094]    If in decision block  608  it is determined that a new dosing session has begun since the last dosage delivery request, the process advances to activity block  612  wherein the number of dosage deliveries occurring during the last completed dosing session is stored in memory for the history file. The process then advances to activity block  614  wherein the current day and time are stored in memory to time stamp the dosage delivery just administered. 
         [0095]    The process now advances to activity block  616  wherein the timer  580  is reset for beginning the timing of a new dosing session. Once the timer  580  is reset, the process advances to activity block  610  for incrementing the dose counter. The process then returns. 
         [0096]    The sensing of a dosage delivery as may be seen from the foregoing is a two event process. This is in response to the requirement for conserving battery power. The first event is the closing of the reed switch  532 . The reed switch draws no power from the battery  568 . Once the reed switch  532  is closed, the dosage delivery is validated by the optical sensor  540 . The infrared optical switch has high reliability and is immune from environmental noise. Since it is an active sensing device, it is only turned on when a dosage delivery is to be validated. Hence reliable dosage delivery sensing is provided while also minimizing the power requirements for such sensing. 
         [0097]    While particular embodiments of the present invention have been shown and described, modifications may be made, and it is therefore intended in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention as defined by those claims.