CA1193934A - Implantable programmable medication infusion system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A novel infusion system is provided herein for providing medication to a living body of a patient. The infusion system includes an infusion apparatus for implantation in the living body. That infusion apparatus includes a medication reservoir for storing selected medication. Infusion means are provided which includes a pump for infusing the selected medication stored in the medication reservoir into the living body. Operational infor-mation storing means are provided for sensing and storing information per-taining to actual pump operation. Telemetry means is provided for transmit-ting the operational information out of the living body.

Description

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The present invention relates to the field of dispensing medication to a living being. Although mainly intended for use by human patients re-quiring infusions of a drug, e.g. insulin, glucose, heparin, or any of various other che therapeutic agents, the invention extends to use in any living body (e.g. domestic animals) and to the infusion of any liquid (e.g. blood) or colloidal suspension, or gas or granulated solid, which may provide a curative or healing effect. Although a principal use envisioned is for im-plantable devices, it is also envisioned that it could be used external to a living being for the infusion of medication. This invention relates par-ticularly to an implantable infusion apparatus.
Various techniques and devices have been suggested and are cur-rently under study which address the problem of dispensing a drug or other medicative liquid into a living body. Of these techniques and devices, how-ever, sufficient safety features in the environment of the flexibility achieved by programming dosage inputs are rarely contemplated.
One liquid infusion device discussed in U.S. Patent No. 4,077,405 by Haerton et al discloses a controllable dosing arrangement which provides for human operator interaction. A syringe forces liquid through a pressure valve in-to a supply reservoir and a bellows pump forces drug from the reser-voir through a flow limiter into the body. This device fails to address various safety problems, e.g. leakage, excessive pumping, and excessive re-quests for drug. No provision for detecting leaks in the device, for signal-ing malfunctions, for restricting the number of or quantity of drug doses, or for monitoring proper operation of the device is suggested.
Like Haerton et al, U.S. Patent No. 3,692,027 by Ellenwood teaches an implanted, self-powered drug dispenser having a bellows pump which employs one-way valves. The ~L93~3 9L

Ellinwoocl device is not programmable ancl varies dosage by opening and closing portals or selecting a dose of medication from one of a plurality of pumps having different dosage volumes and/or different meclications stored therein. Safety redundancy pertaining to Eilling, leakage problems, patient and doctor interaction with the dispenser, and dosage input programming are not considered.
An invention of Blackshear (U.S. Patent No. 3,731,681) shows another infusion pump without appreciable safety features. Blackshear does not look for pressure integrity before filing the device with drug, nor teach any means for monitoring pump operation.
Richter (U.S. Patent No. 3,894,538) considers, in a medicine supplying device, one safety feature: an exit plug for preventing con-taminants from entering the device and for limiting drug outflow. The flow from the Richter device does not provide a smooth pulsatile flow of drug which is infused over a relatively long period. It further fails to disclose any means for reliably controlling or varying the flow rate or for monitoring the rate of operation.
Several recent publications have also underscored the need for an implantable medication infusion device. Two articles by Rhode et al ("One Year of Heparin Anticoagulation"; Minnesota Medicine; October, 1977 and "Protracted Parenteral Drug Infusion in ~mbulatory Subjects Using an Implantable Infusion Pump"; American Society for Artificial Internal Organs Transaction.s, Volume XXIII, 1977) described an implantable infusion pump. No check for pressure integrity before filling or during operation, no programming means, and no patient or doctor interaction with the device are contemplated.
An article by Spencer ("For Diabetics: an electronic pancreas";
IEEE-Spectrum; June, 1978) discusses current trends in the implantable drug pump field. Programming the rate of drug flow over time depending on food intalce is menti(;ned. Efforts in the development of an ~ - 2 -3~

tmplsntable bellows pump are also dlscussed. Spencer further mentions Che use of an alarm wich sounds lf a pump falls to p.ovide drug ln nccordance with the preprogrammed rate. The Spencer artlcle generally dlscusses drug dlspenser technology but falls to address many speclfic problems. As in the other clted works, safety features such as an antechamber; leak detection;
dlstlnctive subcutaneous stimula~ion to indicate various devlce malfunctions;
safe methods of programmlng the device regardless of work, food-intake, or tlme schedules; and telemeterlng of lnformation per~alning to the actual operatlon of the pump are not considered.
Finally, German Patent Application DE 31-12916-Al, published February 15, 1982, in the name of Medtronlc Inc., teaches an irnplantable medicine dispenser which is externally programmable. Receipt of programming commands can be verified by an acoustic signal. No means are shown or suggested for sensing, storing~ and telemetering information pertaining to actual pump operatlon. As a result, only the instructions given to this apparatus can be verified and changes in the physiological response of the patient, often detrimental, are the only way to monitor pump operation.
According to an aspect of the present invention, an infusion system is provided for providing medication to a llvlng body of a patient, comprising an infusion apparatus for implantation in t:he living body, the apparatus including a medication reservoir for storing selected medication, and infusion means including a pump for infusing the selected medication stored in the medication reservoir lnto the living body, which infusion apparatus comprises operational lnformation storing means for sensing and storing informatlon pertalnlng to actual pump operation, and telemetry means for transmitting the operational information out of the living body.

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By a variant thereof, the operationa] information storing means includes pump operation information storing means for storing a history of -the actual operation of the pump; and the pump is designed to pump a preselected amount of medication into the living body each time it is operated.
By another va~iant thereof, the infusion apparatus includes means for operating the pump in response to requests made by the patient;
and the operational information storing means stores information pertaining to the history of requests made by the patient during a prese-lected time period.
By yet another variant thereof, the operational information stor-ing means includes inhibiting means for inhibiting operation of the pump upon receipt of a request made by the patient which would result in an excess of pump operation beyond a desired maximum infusion rate; and the request storage means stores information pertaining to the number of un-fulfilied requests by the patient.
By still another variant thereof, the infusion means has at least one remotely commandable operational characteristic, and the system further comprises: command receiver means coupled to the infusion means for receiving command signals; and command source meams external to the living body for transmitting the command signals to be received by the command re-ceiver means; the telemetry means comprising telemetry transmitting means for telemetering the operational information out of the living body, and external telemetry receiving means for receiving the telemetered operational infor-mation external to the living body.
By yet another variant thereof, the telemetry transmitting means produces an RF signal.

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By still another variant thereof, the operational information includes information pertaining to key parameters of the operation of the system.
By a further variant tllereof, the telemetry means telemeters in-formation pertaining to the level o medication in the medication reservoir.
By a still further variant thereof, the telemetry transmitting means telemeters information pertaining to increases in pressure within the medication reservoir.
By yet a further variant thereof, the infusion apparatus includes means for operating the pump in response to re~uests made by the patient;
and the telemetry means selectively telemeters information pertain-ing to the validity of the requests and satisfaction of the requests.
In the accompanying drawings, FIG. 1 illustrates a general block diagram of the entire medication infusion system of an aspect of the present invention.

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FIC,S. 2 and 3 show a front cross-sectional anrl top view, respec-tively, of the implantable portion o~ rhe present medication infusion system.
FIG. ~ shows, in detail the mechanical construction of a pulsati-ble pump element of the invention.
FIG. 5 is a block diagram showing the electronics of the invention FIG. 6 shows a method of programming the rate of medication infusion into a patient by use of the maximum running integral dosage limiting technique.
FIGS. 7 and 8 are illustrative of a patient programming unit.
FIG. 7 shows a front view illustrating a sample apparatus for selecting dosage depending on meal size and recognized body condition factors.
FIG. 8 shows a rear portion which provides information relative to the last programming of the patient programmlng unit.
Generally, the present medication infusion system provides an antechamber which is normally filled with saline solution to act as a buffer between the medication intake point and the rnajor medication reservoir in the device. The reservoir may contain a fatal amount of drug or other medication. It is thus isolated from the body by a filter, ; 20 one-way inlet valve, the saline-containing antechamber and a septum providing a self-sealing opening to the antechamber. Further, the reservoir is at a pressure below the ambient body pressure. Thus, even if the inlet valve and septum leak, body fluids would enter the antechamber and slowly ooze into the reservoir through the flow-impeding filter.
Any other leak of medication from the reservoir or leakage of body fluid through the outer sheLI of the implanting device would be sensed by a fluid detector outside the reservoir. Similar safety back-ups are provided at the outlet output of the reservoir whicll is provided with two one-way valves and a filter.

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The outlet, however, als(- is provided WiLh d deformable wall which combines with the outlet iilter to yielcl an exponentially decaying flow of medication. This smooth flow over a long~ predetermined period pro-vides - 5 c~ -X

enhanced safety and flow control. The deforrm~ble wc~ll scrves thc func~ion of an accumulator and the output filter provi(!es the funcLion of a flow resistor or restrictor; thus the deEormable wall provides the "C" and the filter "R" of an "RC" time constant for the decrease of flow atter a pulse of medication has been delivered into an outlet chamber prior to infusion into the body via the RC networlc. Also at the outlet is an element for correlating medication requests with medication dispensing, thus providing an operational indicator and safety feature.
Also, for safety, a filling procedure is taught which insures that medication is not injected into the device until pressure integrity at the input is determined. In the mechanical pump itself, the amount of medication pulsing it can provide is restricted in the preferred embodiment by a pressure limit intrinsic in the pump design.
In programming the present system, convenience and safety are again major concerns. A flexible, maximum running integral program for limiting medication dosage inputs communicated by a patient satisfies not only a patient's need for proper amounts of medication but also satisfies a variable work and eating schedule requirement of the patient and can provide a safe, proper medication schedule even though the patient experiences time zone or work schedule chan~es. In addition to a programma-ble rate of medication input, a hardwired limit is also included. If requests exceed the limits set by the program, the hardwired limits will inhibit the pulsing of excessive medication into the patient.
Final]y, the system provides a history of medication infusion which a physician can read out through telemetry means. This telemetry means is also used to program and check the system.
Referring to FIG. 1, the various portiolls of the implantable .

programmal)le me~licatioll intus:ion sysrern are shown. An implant.able portion

2 in a patient's body can be programmed either by the medication programming system I or by the patient:'s programming unit 400. Commands from the - 6 ~1 _ medication programming system 1 emitted from the communication head 300 are transmitted to electronics in the implantable portion 2 in order to program and effectuate the infusion of medication into the body in a safe, controlled fashion. The medication programming system 1 is also capable of reading information out of the implantable portion 2 concerning the amount of medication dispensed over a specified time period and furthermore the medication programming system 1 is capable of calibrating the per pulse of medication of the implantable portion 2. A medication injection unit 7 is connected to a double hypodermic syringe 4 which is used to provide medication to an implantable medication reservoir 18 (shown in FIGS. 2 and 3 included within the implantable portion 2. Fill commands to the medication injection unit 7 emanate from a medication programming unit 3. A patient's programming unit 400 is controlled by the user ot request doses of medication. The dosage requests are controlled by safety units embodied in fixed hardware elements and programmable elements found in the implantable portion 2. To recharge a rechargeable cell contained within the implantable portion 2, an external charging head 9 connected to a battery charging unit 11 is included.
The need for the charging head 9 and battery charging unit 11 can be obviated by the inclusion in the implantable portion 2 of a power supply (such as a lithium cell) which is of sufficient lifetime to negate the need for recharging. The medication programming unit 3 outputs to a paper printer 13 which provides hard, readable output that can be readily interpreted by a physician.
Referring now to FIGS. 2 and 3, the implantable portion 2 of an implantable programmable medicaition infusion system is shown.
Medication is provided to the implantable portion 2 by means of a double hypodermic syringe 4 which penetrates the skin 5 and a self-sealing 3S9~
f rubber septum 6 whicll covel-s an antechamber 8 in leak--pl~ooL [asllion.
Medication is intro~luced into the antechamber 8 ~hrough syringe 4 under pressure ~he level oE which is contro~lable _ 7 a -.

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externally. ~ rescrvoir chamber 10, in which rhe medicar]oll is stored undcr relatively constant pressure, is ied from the antechamber 8 Vi;l a ceramic filter 12 and an inlet pressure valve 14 which permits flow only from the antechamber 8 into the reservoir chamber 10 when the pressure differential between them exceeds a predetermined threshold.
The inlet ceramic filter 12 performs various functions. Besides filtering contaminants from medication being fed into the reservoir chamber 10, the ceramic filter 12 serves to limit the rate of medication flow from the antechamber 8 into the reservoir chamber 10 or, conversely from the reservoir chamber 10 into antechamber 8 should the inlet pressure valve 14 leak or malfunction. Further, should the self-sealing rubber septum 6 leak, the ceramic filter 12 together with the inlet pressure valve 14 prevents the inflow of body fluids into the reservoir chamber 10. Further, should the inlet pressure valve 14 and the septum 6 both leak or otherwise malfunction, the inlet cerarnic filter 12 would permit only a slow flow of body fluids to enter the reservoir chamber 10, until body ambient pressure is achieved, at which time some medication could diffuse through the ceramic filter 12 but at a rate that would not be hazardous to a typical patient in which the system would be implanted.
The reservoir chamber 10 comprises a liquid-vapor portion 16 which rests atop a reservoir of medication 18, the liquid vapor portion 16 and the reservoir 18 being separated by a flexible diaphragm 20.
The flexible diaphragm 20 could comprise an elastomer. a moveable bellows, or other substitutive flexible diaphragm means which would separate the medication reservoir 18 from the liquid vapor portion 16. The liquid-vapor volume in the vapor portion 16 prefer~lbly comprises a saturated vapor in equilibrium with a small amount of Freon 113 liquid. Over normal bocly temperatures, Freon 113 I~as a linear pressure characteristic rallging from -4 psig (clt 98) to .3ppl-OXi-93~3~

mately - 2.5 psig ar (104 F). Using Freon 113, che meclicari(-n re~sel-v(?ir 18 wiLI be maintainecl at a pressure beIOW that: of the human bocly pressure up to altitudes oE 8500 feeL. For patierlts who may live above that altitude, other tluorocarbons at lower pressure may be employecl. In this way, sllould both the septum 6 and the inlet pressure valve 14 leak, the effect would be to cause body fluids to diffuse slowly, via the inlet ceramic filter 12, into the medication reservoir 18 rather than to have a rapid flow of medication enter into the body where it could cause harm to the patient. Because of the pressure differential between the body and the medication reservoir 18, medication will not flow from the reservoir 18 into the body. As the amount of meclication in the medication reservoir 18 varies, the flexible diaphragm 20 moves up or down, with the Freon 113 being converted either from liquid to vapor or vapor to liquid to provide an essentially constant pressure which will always be below one atmosphere and below normal body pressure.
A reservoir chamber having a volume of approximately 10cc would be suffi-cient for most applications. This amount of concentrated medication, insulin for example, could be fatal if injected over a short time.
The volume of the antechamber 8 is less than 10% the size of the reservoir chamber 10. In the worst case of leakage if medication leaked from the reservoir chamber 10 into the antechamber 8 and even if the antechamber 8 leaked as well, only diluted medication would enter the body gradually passing from an area of low pressure to one of higher pressure. Thene is thus little likelihood of the dose being fatal. As readily seen in FIG 2, decreasing or expanding the size of the reservoir chamber 10 wou]d be a simple modification because of ehe arrangement of elements in the system. Included in the reservoir chamber 1() is a dual pressure switch which can comprise a reservoir fi]l switch 23 for indicating 93~

when the pressure in the reservoir chamber 10 reaches a predeterm;lledlevel e.g. -2 psig and a second s~it:ch 25 ~or indicating when the pressure reaches -I psig. Fill ~ ~ - 9a -~3~

switch 23 is used duril-lg the l~illirlg procc~(lule t(. inclicate (by a telcmetly system to be describecl later) whell che level of meclication in thc reservoir chamber 10 has reachecl a specific value. Sho-llci body Eluids leak into the meciication reservoir 18 ~or any reason, an increase in pressure would result that would activate the seconcl pressure switch 25. For example, when body fluids entering reservoir 18 reach a pressure of -1 psig, this would set off a subcutaneous electrical stimulation alarm system. By having the fill switch 23 set at a lower pressure than the body fluid leak detection pressure switch 25, the filling of the reservoir 18 can be accomplished without setting off an alarm signal.
In order to fill the reservoir chamber 10 with medication, a sequence of steps is followed. The antechamber 8 is normally filled with a saline or other innocuous solution which provides a buffer between the body and the reservoir chamber 10 and which if the septum failed would cause no harm to the patient. At the time of filling, a double hypodermic syringe 4 is directed into the antechamber 8 and saline is introduced into the antechamber 8 through one needle and exits through the other in ordar to flush the antechamber 8 with more saline. Once flushed, the antechamber 8 is checked for pressure integrity with saline introduced under a pressure which is less than that required to open the inlet pressure valve 14. When pressure integrity is determined, the antechamber 8 is flushed with the desireci medication (e.g. insulin).
Medication is then forced into the antechamber 8 at a pressure greater than that required to open inlet pressure valve 14. The insulin fills the medication reservoir 18 of the reservoir chamber 10 until the flexible membrane 20 contacts the dual pressure sw;tch 22, forcing the reservoir fill switch 23, to generate a signal (e.g. at -2 psig) which indicates that the filling has been completed. The amount- ol medication required to fill the medication rescrvoir l8 is norcd and then the alltecllamber 8 is flushed once ag.lill'witll X 1()-

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innocuous saline solution. Thc cnlirc rcservoir clmmbeL 10 is surroullclccl by a wall 24 and is ;solated ~rom the other elemen~s o~ ~:he sys~em by means of the inlet pressure valve 14 and an interface pressure valve 26 which connects the reservoir to a pulsatile pump 28 which is shown in FIG. 4. The remaining elements of the implanted portion 2 are also shown in FIG. 2: an electronics section 30 with a battery subsection 32. As is readily seen in FIG. 2, a hermetically sealed enclosure 34 surrounds the reservoir chamber lO as well as the pulsatile pump 28 (see FIG. 4) and the electronics section 30 with the battery subsection 32. To provide an enhanced safety feature, a fluid detector 35 is provided between the wall 24 and the hermetically sealed enclosure 34. Should either the outer hermetic enclosure 34 leak or should the reservoir chamber 10 leak, the fluid detector 35 is placed at a location where the leaking body fluids or medication would be detected. The fluid detector 35 could be a very high resistance resistor (e.g. 10 megohms) whose resistance drops significantly in the presence of fluids. A malfunc-tion signal to warn the patient if such a leak is detected, is provided.
Similarly, a rnedication leakage detector 37 in the liquid-vapor volume 16 would indicate when medication was leaking into that chamber 16.
This detector rnay also be a resistor whose value will be significantly altered by the presence of the medication. The mec!ication leakage detector 37 when actuated would set off a distinct subcutaneous electrical stimula-tion alarm signal that can be detected by the patient.
FIG. 4 illustrates the pulsatile pump 28 shown in the top view of the implanted portion 2 shown in FIG. 3. Tile interface pressure valve 26 shows where medication enters the pulscltile pump 28 when the differential in pressure between the reservoir chamber lO ancl a medication storing means 200 (inside the pulscltile pump 28) reaclles a lcveL sufficient 3~

to open the inlet pressurc valvc 26. In the pre~erred cmboclimcnt: shcwn in FIG. L, this diL~erential i.n pressure is caused by the expansion of a spring bellows 202 - 11 a -i~ ~

~3~34 in responsc~ ~o arl electrical pulse in~rocl-lcecl ro a pulsing c(-il 204 which surrounds a plate 206 which is attached to the spring be11ows 202. When a pulse passes through the pulsing coil 204, plate 206 is driven to a forward stop 208. This action of expanding the storing means 200 causes the interface pressure valve 26 to open, thereby allowing medication from the reservoir chamber 10 to fill the medication storing means 200. The plate 206 is a permanent magnet (or, possibly, a magnetizable material) which moves in response to a current induced magnetic force. ~hen current in the pulsing coil 204 ceases, the spring force of the bellows 202 returns the plate 206 to a position against a backstop member 210. The amount of travel of plate 206 is thus fixed, rendering the stroke volume of the pulsatile pump 28 constant and independent of the electrical pulse current or pulse width into the pulsing coil 204 as long as certain minimum currents and pulse width is provided. The maximum pressure that can be exerted by the pulsatile pump 28 is dependent on the spring force that can be exerted by the bellows 202 as well as the cross section area of plate 206 which is in contact with the medication in the storing means 200. More simply, P = A where p is the maximum pressure that can be created by the spring Eorce of the bellows within the medication storing means 200, F is the spring force of bellows 202, and A is the portion of surface of plate 206 which is in contact with the medication in the medication storing means 200 which extends into the bellows 202. Should a malfunction occur in the electronics and a continuous se4uence of rapid pulses be introduced to the pulsing coil 204, causing the plate 206 Lo reciprocate, the returll of the plate 206 to its original position against the backstop member 210 would be inhibited once the pressure in the storing means 200 exceeded p The pressure builds up rapidly beccluse o~ the output flow resistance caused by the ceramic filter 218. The posibility Or introducing drugs or other medication at an unsafe high pressure or high raie is thus essentially eliminated. ~ ~
_ 12 -An outlet pressure valve 212 connects the storing means 200 in the pulsatile pump 208 with an outlet chamber 214. In operation, when the plate 206 returns toward its original position against backstop 210 after being reciprocated by the action of the pulsing coil 204 and the bellows 202, an increase in pressure in the storing means 200 results.
When the pressure differential between the pressure in the storing means 200 and the pressure in outlet chamber 21~ exceeds that required to open outlet pressure valve 212, medication flows into outlet chamber 214 from the medication storing means 200. To prevent large spurts or pulses of medication frcm entering the body over a short period of time, an elastic wall 216 and an output ceramic filter 218 are provided at the entrance to the outlet 220 of outlet chamber 214. The output ceramic filter 218 serves to resist the flow of medication from the outlet cha~ber 214 into the living body. The elastic wall 216 a~ts as a type of capacitance to flow, deforming when a pulse of medication is fed into the outlet chamber 214, the elastic wall 216 thus serving as a fluid accumulator.
me combination of the elastic wall 216 and the output ceramic filter 218 comprises a fluid or mechanical RC network that provides medication into the body within an initial rise followed by a decaying fl~w. rrhe time constant which is fairly long, is de-termuned by the elasticity of the elastic wall 216 and the resistance of the output ceramic filter 218. In addition, the output ceramic filter 218 disallows medication from being diffused into the body at a high rate, should bo-th the interface pressure valve 26 and the outlet pressure valve 212 fail to seal.
Should valve 212, leak, there would be a slow diffusion of medication through the ceramic filter 218 until the pressure in the storing means 200 is essentially equal to ambient body pressure. ~lowever, since the volume means 200 is very small and since the medication fluid is essentially X ~ 13 -~9~g~

incompressible, very little medication can diffuse out and that amount only at a slow rate. Should bo-th X -13a-~33~3~

valves 26 and 212 leak, body fluids would then diffuse into the reservoir 18 because i-t is at a pressure below body ambient pressure. A rise in pressure in the medication reservoir 18 relative to tha-t of the ambient body pressure would cause the -1 psig switch to be activated setting off an alarm~ Further, the medication then could not diffuse through the outlet ceramic filter 218 at an unsafe rate because there is no pressure differential across the flow resistance of the ceramic filter 218.
Safety of the output is best understood by considering the various pressure levels in the pulsatile pump 28. With a bellows spring force which gives a maximum pressure, Pmax, of 15 psig and with an outlet pressure valve drop of 5 psi, it is possible for the pulsatile pump 28 to provide a pressure as high as 10 psig in the outlet chamber 214. The pressure in the outlet chamber 214 is significantly greater than the body ambient pressure of approximately 0 psig or the diastolic blood pressure which is approximately 2 psig. me resistance of the output ceramic filter 218 is selected to limit the drug flow to a given safe level, for example less than 50~ the maximum pumping flow at which the pulsatile pump 28 is designed to operate. As with the :inlet ceramic filter 12 (of FIG.
2) the outlet ceramic filter 218 also filters out contaminants moving in either direction, from the outlet chamber 214 into the body or ~rom the body into the outlet chamber 214. Also included in the pulsatile pump 28 is a pressure transducer 222 which is shown located in the outlet chamber 214 but could be located wherever it could detect and respond to a pressure change corresponding to medication being pumped from the pump 28. The pressure transducer 222 produces an electrical output when a pressure pulse of medication enters the outlet chamber 214. The pressure transducer 222, in other words, detects the pressure pulses which are provided each time the spring bellows 202 returns the plate 206 to its ~ - 14 -3~3~

original position against backstop 210. By comparing the pulsing from pulsing coil 204 with the - 14a -~3~3~

pulsing generated by pressure transducer 222, an indication is given as to whether an absence or insufficient number of pulses or rnedication have been provided to the body. An indication of extra pulses of medication cornpared to -the nurnber of electrical pulses may also be provided.
The pulsing signal to pulsing coil 204 as well as the pulse output frorn the pressure transducer 222 are better understood with reference to FIG. S a block diagram of the electronics section 30 shown in FIGS.
2 and 3. As seen in FIG. 5, the electronics section 30 cornmunica-tes with a corrznunication head 300 which is external to the body, ccx~Tunicating through skin 5 by rneans of radio signals which includes an alternating magnetic field. The communications head 300 provides both power inputs and cc~nmands, including programmable inputs, to the electronics section 30. Power is provided by rneans of an alternating field, e.g., a magnetic field, which is ccmmunicated to a pick.up coil 304 which is implanted together with the rest of the electronics section 30 in the body. The pickup coil 304 receives an AC power signal frorn corrmunications head 300 and passes it on to a full wave rectifier 306. One rectified putput frorn the full wave reactifier 306 enters a battery charge control 308 which provis~es a f ixed DC charging signal to a power cell 310 . The power cell 310 can be a nickel-cadmiurn cell which is readily rechargeable off a rectified signal at a typical frequency of 20 kHz. ~ternatively, a lithiurn-type solid state battery can be used instead of the nickel-cadmiurn cell in which case the charging circuitry would be elirninated, the lithium-type battery providing sufficient power ove~ a long terrn, thereby obviating the need for recharging. The power cell 310 provides a biasing voltage to a transistor switch 312, the output of which enters the pulsing coil 20~ previously described in the context of the pulsatile pump 28. In addition to providing power to the power cell 310, rec-tified ~\ - 1 5 3~3~

power is also introduced to a DC to ~C converter 314 the purpose of which is to provide power at the proper levels to the various loads in the system. In J~ . - 15~ --l6--33~3~

addi~ion to the AC power sigrlal, pickup coil 30~ also rece!ves a trclin of seridL digital hits ~rom the commurlica-tion head 300. The digi-tal bits cornprise commands ~or pro~rarnma'ole inputs which are conve~ed, via the pickup coil 304 to a command receiver 316. The signals from the command receiver 316 erlter a cornmand decoder 318 which determines if the digital bits are in a proper sequence and, if so, wha-t action in the system -the commands dictate. It should be no-ted that the f~lll wave rec-ti-fier 306, the bat-tery charge con-troller 308, the command receiver 316, and the command decoder 318 are powered only when an AC signal is picked up by the pickup coil 304. This, of course~
prevents the possibility of detecting stray signals as commands and provides power savings. To be sure, -the power savings achieved could make possible the use of the aforernentioned lithium cell which would not require recharging. From -the command decoder 318, programmable inputs and other comr~ands can be provided to a number of elements. A programrnable base rate is entered into a base i 20 rate rnemory unit 320 which stores a value indicating the number oE pulses of medication which are requested -to be provided to a patient during a normal preselected period of tlme. A second programmable input is provided a patient controlled rate memory unit 322 which stores a value indicating a number o~ pulses of medication that are requested to be introduced into the body over a given period of time during which the patient eats a meal or otherwise alters the chemical balance of the body (as by exercising).
Associated with the base rate memory unit 320 is a hardwired base rate limit control 324 which sets a maximum rate that can override reques-ts of the base rate memory unit 320 which are excessive. Similarly, a hardwired patient controlled rate limit control 326 provides a fixed maximum number of pulses which can be provided at a time after a meal or at 3S other times and under other conditions. As long as the base rate and the patient controlled rate values s-tored in memory units 320 and 322 respectively, do no-t exceed the hardwired ~L~3~)3~

values fixed within limit controls 324 and 326, respectively, an output pulse is provided to the input of -transistor switch 312 to stimulate a pulse putput from pulsing coil 204. Should the rate of either memory unit 320 or 322 exceed the hardwired limi-ts in the limit control elements 324 or 326 respectively, a "rate request exceeds limit" signal is fed from the limit control element 324 or 326 into a progra~nable alarm generator 328 which provides an electrical signal to be stimulation electrode 330 implanted subeutaneously. By the stimulation electrode 330, the patient is informed by means of a subcutaneous stimulation 10that one of the me~ory units 320 or 322 is requesting more than the maximum allowable number of pulses.
It should be noted that the signal to the stimulation eleetrode 330 can serve the dual function of not only providing the patient with a subeutaneous electrieal stimulation but may also be the source of a signal detected by the eornnunieation head 300 ecx~nunieated to the patient or his physieian either or both that a failure has oecurred.
As shown in FIG. 5, the eleetrode 330 will be isolated and should be insulated from the outside of the hennetieally sealed enclosure 34 of the implated portion 2.
20A partieularly signifieant feature of ~e inven~ion resicles in the programnability of the alarm generator 328 based on input eommands from the co~nand deeoder 318. The alarm generator 323 can be switched on or off and the voltage produced by the generator and hence the electrode 330 can be varied in response to signals emana-ting from the co~nunication head 300 and channeled through the command receiver 316 to the comnand decoder 318. In addition, to check the proper operation of the system, the eo~nand decoder 318 can receive test signals which can simulate aetual occurrances to determine whether the circuitry in the eleetronic )( ~

3~

section 30 is operating properly. For exan~le, extra pulses from the command decoder 318 ccm be entered in-to the hardwired limi.t control elements 324 and 326. These extra pulses can be added to -the - 17a -3~3~

pulses provided by the base rate and the patient controlled rate memory units in order to exceed the hardwired base rate and the hardwired patient-controlled rate, respectively. When the rates are exceeded, the alarm generator 328 will provide a signal. In this way, the alarm generator 328 can be used to check the operation of the limit control elements 324 and 326 and also familiarize the paten-t with the corresponding sub-cutaneous emitted by the tickle electrode 330. The programmable alarm generator 328 also receives inputs from the pressure switch 22 and the fluid detector 35 both shown in FIG. 2. If body fluids leak into the reservoir 18, the pressure switch 25 will be activated, indicating this fault condition to the patient by means of the activation of the alarm generator 328 and the elec-trode 330. If -the patient was unconscious, voltage levels on the patient's skin at the site of the inplanted portion 2 could be used by the physician to indicate if a malfunction has occurred and which malfunction it was. Further, as previously described, should fluid leak out of the reservoir chanb~!r 10 and onto the lining of the enclosure 34 or, alternatively, if body fluid should leak in through the enclosure 34, the fluid deteactor 35 would sense such leakage and, as shown in FIG. 5, would provide input to the alarm generator 328.

Still another input to the alarm generator 320 comes from the power cell 310 associated with transistor switch 312. The voltage level of the power cell 310 is communicated to the alarm generator 328, a tickle or subcutaneous stimulation being generated when the voltage is below a predetermined level. Finally, reEerring back to -the pulsatile pump 28 of FIG. 4, the electrical pressure transducer 222 provides a signal which is compared to a programmed "insufficient rate" value emanating from the command decoder 318. If the number of pulses sensed by the pressure transducer 222 over a specified period of time are less than 3~

the num~er of pulses associated with the "insufficient rate" command input, a pulse rate detector 3~2 will provide an output indicating that an insufficient X - 18a -amount of medication is being provided to the 2atient over the specified time. The output of pulse rate detector 332 (FIG. 5) also enters the tickle generator 328 to provide a subcutaneous tickle de-tec-table by -the patien-tO It should be noted that the various mentioned failures in the system result in subcutaneous stimulations each of which may be different in s-timulation magnitude, duration, or periodicity. For example, the stimulation may range between one to four volts and may vary in frequency above and below 20 pulses per second and most importantly, a variety of pulse patterns may be used each unique to a particular malfunction or warning. Additional warnings that might be used are:
(1) medication has leaked into the liquid-vapor volume, (2) only 10~
of the medication remains in the reservoir, (3) only 5 days medication remains.
In addition to pulsing the pump coil 204, the outputs of the ., , limit control elements 324 and 326 also provide input to a pulse recorder 334. Pulse recorder 334 maintains a ~nning history of how many electrical pulses have been provided to the pulsatile pump 28 since the last refill of the reservoir 18 (in FIG. 1). An "interrogate" signal from the command decoder 318 instructs the pulse recorder 334 to provide the history to a telemetry transmitter 336 which communicates the pulse history to a telemetry coil 338. The pulse recorder 334 would record both the number of pulses delivered to the pumping coil 204 and the number of pulses detected by the pressure transducer 222 and/or the difference between these two numbers. The telemetry coil 338, in turn, provides its output through radio frequency signals to a telemetry receiving antenna in the communication head 300. In addition to the pulse history the -telemetry transmitter 336 also receives, during progra ~ing, inputs from the base rate memory unit 320 and patient controlled rate memory ~ ~3~3;3~

unit 322 which are transmitted back to the ccmmunication head 300 indicating that the desired base rate and patient controlled rate, respectively, have been programmed into the corresponding X - l9a -3~3~

memory unit 320 or 322. Similarly, other key par~neters 337 of -the system are also conveyed by means of the telemetry transmitter 336 back to the communication had 300. For example, the exact pressure transducer output waveform would be telemetered. Of course, the pressure waveform signal would be transmitted when the telemetry system is powered. Similarly, the reservoir fill switch 23 placed in -the reservoir chamber 10 to indicate when it has reached a predetermined fill level is also connected via the telemetry transmitter 336 and telemetry coil 338 to the communication head 300 to indicate when the reservoir 18 has been filled with medication.
Finally, a simulated low battery voltage signal can be conveyed from the command decoder 318 to the telemetry transmitter 336 to check that portion of the status circuitry. As with the full wave rectifier 306, battery charge control 308, command receiver 316, and command decoder 318, the telemetry transmitter 336 is powered only during programming, interrogation, testing with simulation sic~nals, and power cell charging.
Reference i5 now made to FIG. 6 which shows a method of programming the patient controlled memory unit 322. The significance of the method lies in the fact that it provides two maximum running integral dose limits in response to requests for medication. Two maximum integral number of pulses for two different time periods are provided. Both are independent of the time of day and therefore would be effective regardless of the patien-t's eating or working schedule, which schedule change might be a result of the patient changing time zones. In the sample graph of FIG. 6, a maximum of eight pulses for a four hour period and twenty-four pulses for any twenty-four hour period are imposed as maximum running integral dose limits. I`hese rate settings can, of course, be altered depending on patient needs and medication to be administered and -time periods other than four hours or 24 hours could be used. In FIG. 6, the nurnber of pulses is shown as a function of time.

In Fig. 6, at midnight, the number of pulses that are allowe~
in the four hour period is eight. Shortly after ~ A~M. five pulses are requested diminishing the n~ber of additional pulses allowed to three pulses. Prior -to noon, within -the four hour time period, a five pulse request is entered. In accordance with the maximum running integral four hour restraint, only -~hree pulses are penmitted but the remaining two pulses in the request are stored in the memory unit 322 (FIG. 5) to be executed at the end of the four hour period beginning immediately after four hours past the delivery time for the after breakfast pulsing. Shortly after noon, when the four hours are over the two pulses are executed. It should be noted that shortly after noon the three pulses provided just before noon were subtracted from the eight pulse allowance. The dispensing of three pulses prior to noon is not eradicated until four hours thereafter, or shortly before 4 P.M. Shortly before

4 P.M. the three pulse allowance is automatically raised to six pulses, accounting for the three pulses executed just before noon. Shortly after 4 P.M., the allowance automatica]ly rises to eight pulses thereby accounting for the two pulses executed shortly after noon. At approximately 6 P.M. the patient has dinner requiring five pulses and the allowance diminishes to three pulses. Shortly be~ore 10 P.M. the patient has a snack which requires two pulses of medication diminishing the allowance to one pulse. At approximately 10 P.M. the five pulses provided at dinner are no longer of import and the allowance is raised by those five pulses to a six pulse level allowance. The importance of FIG~

5 is readily apparent when one considers the various time zones or work schedules a patient may go through from time to time in the course of his life. The program in FIG. 6 provides sufficient safety and flexibility for a wide variety of patients.

3~3;3 ~L

Referring now to FIG. 7, the front vlew of a patient programming unit 400 is sh~wn. In the center of the unit is a dial 402 whi.ch can be rotated to indica-te the size J~ . - 21a -3~3~

of a meal eaten by the patient or the amount of exercise he has under~one, in order to provide inputs indicating the amount of medication needed.
Output from the patient pro~ra~ming urlit 400 is detected by the pickup coil 304 of FIG. 5 as commands. ~hether or not the request is valid is de-terrnined in the electronic section 30 and is conveyed back to the patient progra~ning unit 400 by telemetry. A signal by the patient programming unit 400 to the patient indicates whether his request has been satisfied. The patient progralhming unit 400 will be provided both with audio and visual outputs rendering it paxticularly useful for those patients having either visual or hearing handicaps.
In FIG. 8 is the reax view of the patient programming unit 400.
The rear side of the patient programming unit 400 will pxovide information indicating the number of pulses sent at the last request 403; the time of the last request 404; and possibly (but is not shown) the number of pulses which can be sent within the program restraints. By programrning ROMS (not shown) in the patient programming unit 400 in accordance with the running integral progrc~ms shown in FIG. S an "OK" or "~O MUCH REOUESTED"
video and/or audible output can be provided. The audio output would emanate fro~ the loudspeaker 405. When the request leads to the dispensing of a pulse or pulses of medication into the outlet chamber, a "MEDICATIO~
SENT" signal from the implan-ted portion 2 is relayed to the patient programrning unit 400 to ac-tuate an audio indication by loudspeaker 405 or by visual means.
It should be understood that alternative embodiments are contemplated by the present invention. ~or example, the antechamber 8 can comprise a vitreous carbon insert in the skull, or other suitable, accessible place on the body, coupled with a tube directed to the reservoir chamber 10 which may be located in the torso. The filling procedure and elements X ' - 22 -3~3~

of antechamber 8 (e.g., the septwn 6) would remain the s~ne with the vitreous carbon insert. The inlet pressure valve 14 and filter 12 would ' - 22a -3~3~

still separate the insert and tube from the reservoir chamber 10. Similarly, in addition to the patient programming unit 500, a physician's unit may be provided which indicates: when the medication reservoir 18 (of FIG. 1) has been filled, the pulse hi~tory from the pulse recorder 334, and other signals from -the telemetry transmitter 336 of FIG. 4. Such a physician's unit would be connected to the telemetry portion of the communication head 300.

X ~ - 23 -

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An infusion system for providing medication to a living body of a patient, comprising an infusion apparatus for implantation in said living body, said apparatus including: a medication reservoir for storing selected medication; infusion means including a pump for infusing said selected medication stored in said medication reservoir into said living body; operational information storing means for sensing and storing informa-tion pertaining to actual pump operation; and telemetry means for transmit-ting said operational information out of said living body.

2. A system according to Claim 1, wherein said operational in-formation storing means includes pump operation information storing means for storing a history of the actual operation of said pump; and wherein said pump is designed to pump a preselected amount of medication into said living body each time it is operated.

3. A system according to Claims 1 or 2, wherein said infusion apparatus includes means for operating said pump in response to requests made by the patient; and wherein said operational information storing means stores information pertaining to the history of requests made by the patient during a preselected time period.

4. A system according to Claim 2, wherein said operational infor-mation storing means includes inhibiting means for inhibiting operation of said pump upon receipt of a request made by the patient which would result in an excess of pump operation beyond a desired maximum infusion rate; and wherein said request storage means stores information pertaining to the number of unfulfilled requests by said patient.

5. A system according to Claims 1, 2 or 4, wherein said infusion means has at least one remotely commandable operational characteristic, and wherein said system further comprises: command receiver means coupled to said infusion means for receiving command signals; and command source means external to said living body for transmitting said command signals to be received by said command receiver means; said telemetry means comprising telemetry transmitting means for telemetering said operational information out of said living body, and external telemetry receiving means for receiv-ing said telemetered operational information external to said living body.

6. A system according to Claims 1, 2 or 4, wherein said telemetry transmitting means produces an RF signal.

7. A system according to Claims 1, 2, or 4, wherein said opera-tional information includes information pertaining to key parameters of the operation of said system.

8. A system according to Claims 1, 2, or 4, wherein said tele-metry means telemeters information pertaining to the level of medication in said medication reservoir.

9. A system according to Claims 1, 2, or 4, wherein said tele-metry transmitting means telemeters information pertaining to increases in pressure within said medication reservoir.

10. A system according to Claims 1, 2, or 4, wherein said infusion apparatus includes means for operating said pump in response to requests made by the patient; and wherein said telemetry means selectively telemeters information pertaining to the validity of said requests and satisfaction of said requests.