Abstract:
An implantable infusion pump for infusing medicine into a patient has a reservoir for holding the medicine, an injection port for injecting medicine into the reservoir and a controllable shield for selectively blocking access to the injection port.

Description:
BACKGROUND  
         [0001]    This invention relates to implantable infusion pumps, and more particularly to implantable infusion pumps in which access to drug reservoirs within the pump is controlled.  
           [0002]    Implantable infusion pumps are used for the continuous delivery of medicaments, e.g. morphine in a constant dosage over long periods of time. Compared with conventional injections they have the advantage that there is no longer any need to provide an initial high dosage so that despite the decomposition of the medicament up to the next administration time, there is no drop below a certain minimum dose. Instead it is possible to achieve a uniform and significantly reduced supply of the medicament.  
           [0003]    The pumps are implanted underneath the skin and are typically designed to be refilled by injecting medication into a reservoir in the pump, the injection penetrating the skin and a septa covering a port into the reservoir. Frequently, the pumps comprise more than one access port. A first access port supplies a reservoir containing medication for long term, slow delivery. A second access port supplies a reservoir which provides a bolus administration of the medication. Typically, all of the medication injected into the second port will be immediately infused into the patient. Incorrect administration of medicine intended for the first port into the second port will provide an overdose of medicine to the patient.  
           [0004]    U.S. Pat. No. 5,395,324 solves this problem by providing one or more of the ports with a needle stop and filling the port with needles having a side outlet that is blocked unless inserted into the port to the correct depth by abutting the needle stop. Insertion into the wrong port blocks the outlet and prevents injection.  
           [0005]    In addition to the problem of potentially injecting medicine into the wrong port, some patients have highlighted another problem. Especially with medications having an abuse potential, such as morphine, patients have been known to use a syringe to extract the medication from the long term reservoir and then self administer a large dose of the medicine. Such behavior can also lead to an overdose of medicine. The system of the aforementioned &#39;324 patent hinders, but does not completely prevent, such action.  
         SUMMARY OF THE INVENTION  
         [0006]    An implantable infusion pump according to the present invention provides for infusing medication into a patient. The pump comprises a reservoir for containing the medication and an injection access port into the reservoir. An openable and closable shield at the access port blocks access of an injection needle into the port when closed and allows access of the injection needle into the port when open.  
           [0007]    The shield can be for instance adapted to move laterally with respect to the access port, or vertically with respect to the access port. Multiple shields can be employed to block access to the port and in addition the shield or shields can employ linear, rotational or other appropriate movement to block an unblock access to the port.  
           [0008]    To operate the shield, a magnetic rotor can be provided within the pump coupled to the shield. A magnetic driver external of the pump magnetically couples to the rotor whereby to turn the rotor and operate the shield. The rotor preferably has a sequence of north and south magnetic poles and the driver a complementary sequence of magnetic poles. The sequence of poles can be irregular whereby to make unauthorized access to the pump more difficult. The poles on the driver can be electromagnets.  
           [0009]    In one aspect of the invention, a controller can be provided which is in RF communication with a means for opening and closing the shield.  
           [0010]    One desirable feature comprises a delay closing mechanism for automatically closing the shield some time period after it is opened so that an operator does not need to remember to close the shield.  
           [0011]    A method according to the present invention restricts access to a drug reservoir in an implanted infusion pump which is accessible through an access port. The method comprises the steps of: shielding the access port with a shield during a time when access to the reservoir is not to be allowed; and moving the shield to allow access to the port during a time when access to the reservoir is to be allowed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a side sectional elevation view of an infusion pump and access regulator according to the present invention;  
         [0013]    [0013]FIG. 2 is a top plan view of a first embodiment of an access regulator for use in the pump of FIG. 1;  
         [0014]    [0014]FIG. 3 is a top plan view of a second embodiment of an access regulator for use in the pump of FIG. 1;  
         [0015]    [0015]FIG. 4 is a top plan view of a third embodiment of an access regulator for use in the pump of FIG. 1;  
         [0016]    [0016]FIG. 5 is a top plan view of a fourth embodiment of an access regulator for use in the pump of FIG. 1;  
         [0017]    [0017]FIG. 6 is a perspective view of a fifth embodiment of an access regulator for use in the pump of FIG. 1;  
         [0018]    [0018]FIG. 7 is a perspective view of a driving mechanism for an access regulator for use in the pump of FIG. 1;  
         [0019]    [0019]FIG. 8 is a perspective view of the mechanism of FIG. 7 and a controller therefor;  
         [0020]    [0020]FIG. 9 is a side sectional view of a sixth embodiment of an access regulator for use in the pump of FIG. 1;  
         [0021]    [0021]FIG. 10 is a block diagram of a communication system between a controller and a pump according to the invention; and  
         [0022]    [0022]FIG. 11 is a block diagram of an access regulator according to the present invention incorporating an automatic closure upon a time delay. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    [0023]FIG. 1 illustrates an infusion pump  10  having an outer casing  12  of an inert material, such as for example titanium or stainless steel. A bellows  14  attaches to the shell  12  to form a main reservoir  16  for holding a medicine to be infused into a patient. A gas reservoir  18 , formed by the space exterior of the bellows  14  and interior of the casing  12 , holds a pressurizing gas to provide a propellant force to urge the medicine out of the main reservoir  16 . The main reservoir  16  communicates with valves  20  which in turn lead to a plurality of throttle paths  22 , each of which connect to an outlet chamber  24 . A catheter connector  26  connects the outlet chamber to a catheter (not shown) which is implanted along with the pump  10  and out of which the medicine flows into the patient.  
         [0024]    The valves  6  place one or more of the throttle paths  22  into fluid communication with the main reservoir  16 . By varying the flow resistance in the throttle paths  22  the valves  6  can effectively alter the rate at which medicine leaves the pump  10  and enters a patient. A more detailed description of selecting throttle paths, including an RF communication system which induces sufficient current to change the state of the valves is disclosed in U.S. Pat. No. 5,667,504 to Baumann, et al., incorporated herein by reference. In one preferred embodiment, the throttle paths are etched into a chip, such as a silicon wafer chip, as more fully described in U.S. Pat. No. 5,908,414 to Otto, et al., incorporated herein by reference. A more simple pump, may have a single restriction path without an option to change the flow rate.  
         [0025]    A raised injection port  28  covered by a septum  30  allows medicine to be injected into the main reservoir  16  with the pump implanted in a patient. A raised bolus injection port  32  covered by a septum  34  allows a bolus of medicine to be injected directly into the outlet chamber  24  where it can quickly flow into the patient.  
         [0026]    Implementation of the basic pump as just described is within the knowledge of those skilled in the art and may be varied to suit various needs and future innovations without departing from the scope of the present invention.  
         [0027]    An access regulator  100  protects each of the ports  28  and  32  by blocking entry of a needle into the ports  28  and  32 . Although several designs are disclosed herein for physically blocking access to the ports  28  and  32 , it will be understood by those of skill in the art that other ways of blocking the port can be substituted therefor in the scope and spirit of the present invention.  
         [0028]    [0028]FIG. 2 illustrates a blocking member comprising a simple cover  102  which pivots laterally about an axis  104  to cover and uncover the port  28 . FIG. 3 illustrates a cover  106  in two pieces  108  and  110 , each of which rotate laterally about axis  112  and  114  respectively. FIG. 4 illustrates a shutter  116  having two pieces  118  and  120  which slide laterally over the port  28 . FIG. 5 illustrates a shutter  122  which slides laterally over the port  28 . Other covering methods, such as a mechanical iris, could be substituted therefor.  
         [0029]    Preferably, actuation of the access regulator  100  is achieved by rotation of a part within the pump  10 . In FIG. 6, a rotor  124  has teeth  126  thereon which engage teeth  128  on a slidable member  130  in a rack and pinion type engagement to translate rotational movement of the rotor  124  into linear movement of the shutter  122  for moving it into a position to block access to or into an alternative position to allow access to the port  28 . As further illustrated in FIG. 7, one preferred method of rotating the rotor  124  is via a stepping motor arrangement wherein the rotor  124  carries a series of North magnetic poles  132  and South magnetic poles  134  and an external driver  136  similarly carries a series of North magnetic poles  138  and South magnetic poles  140 . Aligning the driver  136  with the rotor  124  and rotating the driver  136  induces rotation in the rotor  124 .  
         [0030]    The driver  136  can comprise a simple part manually rotated over the rotor  124 , but more preferably comprises a portion of a programmable controller  142  (see FIG. 8). The poles  138  and  140  on the driver  136  can be electromagnets. For more precise operation, stator elements (not shown) complementary to the poles  132  and  134  on the rotor  124  can be positioned in the pump  10  adjacent the rotor  124 . Each of the stator elements would be formed of a magnetically soft and permeable material capable of being magnetized by application of a magnetic field, as from the driver  136 . Selectively magnetizing the stator elements induces a rotation in the rotor  124 . Such a system is more fully described in the Hakim U.S. Pat. Nos. 4,615,691 and 4,772,257, incorporated herein by reference.  
         [0031]    The programmable controller  142  can be capable of controlling other aspects of the pump  10  such as the infusion flow rate, or may be dedicated to controlling access to the ports  28  and  32 .  
         [0032]    Each of ports  28  and  32  preferably has associated therewith a rotor  124  and driver  136  which are incompatible with the rotor and driver of the other port so that the driver for the bolus port  32  will operate only the bolus port and the driver for the regular port will operate only the regular port. Accordingly, opening of the incorrect port is avoided. For instance the arrangement of magnetic poles  134  and  136  on one rotor  124  can be incompatible with the arrangement of magnetic poles  138  and  140  on the other driver  136 . Alternatively, the rotors  124  can be given magnetic signatures readable by the controller  142  SO that the controller  142  will know which rotor  124  is being controlled.  
         [0033]    The methods employed to prevent inadvertent access to the wrong port can also prevent unauthorized access to the port  28  by a patient, for instance the rotor  124  can be keyed with a special sequence of north and south poles. Further security could be provided by a magnetic locking mechanism, not illustrated, in which a magnetic key with a particular magnetic signature must be placed adjacent a magnetic lock within the pump to allow movement of the rotor  124  or of one of the access shields disclosed herein.  
         [0034]    [0034]FIG. 9 illustrates a further embodiment wherein a needle stop  144  having a cam follower  146  thereon travels axially within the port  28  rather than laterally. The cam follower  146  cams over a spiral camming surface  148  on a rotor  150  to move the needle stop  144  axially. In an upward position it allows passage of a needle  152  through the septa  30  but blocks further entry of the needle  152  into the port  28 , thereby preventing medication from entering or exiting the port through the needle  152 . In a lowered position the needle  152  is allowed to fully enter the port  28 .  
         [0035]    To fill the reservoir  16  with the pump  10  implanted in a patient, the operator first opens the access regulator  100  over the injection port  28  and then injects the drug through the patient&#39;s skin, through the septum  30  and into the reservoir  16 . Afterwards, the operator closes the access regulator  100 . For instance with the design of FIGS. 6 and 7, the driver  136  is placed adjacent the rotor  124  and rotated to open the shutter  122  prior to injecting the drug.  
         [0036]    Turning to FIG. 10, radio frequency (RF) communication can be established between the pump  10  and an external controller  200 . Such schemes are disclosed in U.S. Pat. Nos. 5,667,504 and 5,820,589 incorporated herein by reference. The controller  200 , preferably a hand held device, incorporates control logic, as for instance in the form of a CPU  202  with some means for input such as a keypad  204  and some means for visual output such as a screen  206  or indicator LEDs (not shown), connected to the CPU  202 . The CPU further controls an RF transmitter circuit  208  and antenna  210  which transmits instructions through the skin to an antenna  212  in the pump  10 . The pump  10  comprises a receiver  214  connected to an antenna  215  and control logic  216  connected to a motor  218  suitable for operating any of the closure mechanisms of the previous embodiments. The motor  218  preferably incorporates or is connected to a power source such as a battery (not shown in FIG. 10).  
         [0037]    The power source for the motor could alternatively comprise a coil  220  energized by RF energy transmitted from the controller  200 . To increase the instantaneous power to drive the motor  218 , the coil  220  could charge a capacitor  222  which is subsequently discharged to operate the motor  218 . A limited function controller could be provided so as to provide one or a limited number of openings of the closure mechanism such as for use when a patient is traveling away from his normal physician.  
         [0038]    Preferably, the RF communication system of FIG. 10 would not be solely devoted to operating a closure mechanism but could also be used to control other aspects of the pump  10  such as flow rate, etc.  
         [0039]    One desirable feature is a mechanism whereby the closure mechanism is opened, as for instance by any of the methods disclosed in the embodiments herein, and then automatically closed by a delay mechanism. Thus, one would not need to remember to close the mechanism later. FIG. 11 illustrates one such embodiment in which a spring  250  biases a closure door  252  into a closed position. Upon receiving instruction from control logic  253  a battery  254  drives a motor  256  to open the door  252  and also charges a capacitor  258  which, after power from the battery  254  to the motor  256  is removed energizes the motor  256  against the bias of the spring  250  until such time as the charge in the capacitor  258  is dissipated and the spring  250  then closes the door  252 . Alternatively, a clock ratchet mechanism (not shown) under power of the spring  250  could time the closure of the door  252 .  
         [0040]    Although the foregoing description of the preferred embodiments of the present invention has shown, described and pointed out the fundamental novel features of the invention, it will be understood that various omissions, substitutions, and changes in the form of the detail of the apparatus and method as illustrated as well as the uses thereof, may be made by those skilled in the art, without departing from the spirit of the present invention. Consequently, the scope of the present invention should not be limited to the foregoing discussions, but should be defined by the appended claims.