CA1231281A - Inhibiting means for programmable infusion system - Google Patents
Inhibiting means for programmable infusion systemInfo
- Publication number
- CA1231281A CA1231281A CA000486976A CA486976A CA1231281A CA 1231281 A CA1231281 A CA 1231281A CA 000486976 A CA000486976 A CA 000486976A CA 486976 A CA486976 A CA 486976A CA 1231281 A CA1231281 A CA 1231281A
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- Prior art keywords
- infusion
- rate
- medication
- pulses
- unit
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
A programmable infusion system is provided herein for providing medication to a living body of a patient. The infusion system includes an infusion apparatus having an infusion device for infusing a selected medication stored in a medication reservoir into the living body. The infusion apparatus has a commandable infusion rate which is variable upon command. The infusion apparatus further includes an inhibiting structure for inhibiting the infusion apparatus from infusing the selected medication if a preselected medication infusion rate is exceeded.
A programmable infusion system is provided herein for providing medication to a living body of a patient. The infusion system includes an infusion apparatus having an infusion device for infusing a selected medication stored in a medication reservoir into the living body. The infusion apparatus has a commandable infusion rate which is variable upon command. The infusion apparatus further includes an inhibiting structure for inhibiting the infusion apparatus from infusing the selected medication if a preselected medication infusion rate is exceeded.
Description
~23~
This invention relates to a programmable infusion system for providing medication to a living body and is a division of copending application Serial No.417,979 filed December 17, 1982, now allowed.
The present invention relates to the field of dispensing medication to a living being. Although mainly intended for use by human patients requiring infusions of a drug, e.g. insulin, glucose, heparin, or any of various other chemotherapeutic agents, the invention extends to use in any living body te.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 implantable devices, it i6 also envisioned that it could be used external to a living being for the infusion of medication.
Various techniques and devices have been suggested and are currently under study which address the problem of dispensing a drug or other medicative liquid into a living body. Of these techniques and devices, however, sufficient , 20 safety features in the environment of the flexibility achieved by programming dosage ineuts are rarely contemplated.
One liquid infusion device discussed in U.S. Patent No. 4,077,405 issued March 7, 1978 to Haerton et al discloses a controllable dosing arrangement which provides for human operator interaction. syringe forces liquid through a ~Z31Z~
pressure valve into a supply reservoir and a bellows pump forces drug from the reservoir through a flow limiter into the body. This device fails to address various safety problems, e.g. leakage, excessive pumping, and excessive requests for drug. No provision for detecting leaks in the device, for signalling malfunctions, for restricting the number of or quantity of drug doses, or for monitoring proper operation of the device is suggested.
~123~
ike Haeeton et al, U.S. Patent No. 3,692,027 issued September 10, 1972 to Ellinwood teaches an implanted, self-powered drug dispenser having a bellows pump which employs one-way valves. The Ellinwood device i6 not progeammable and varies dosage by opening and closing portals or selecting a dose of medication from one of a plucality of pumps having different dosage volumes and/or different medications stored therein. Safety redundancy pertaining to filling, leakage ;:::; ..
problems, patient and doctoc interaction with the dispenser, and dosage input programming are not considered.
An invention of Blackshear et al (U.S. Patent No.
3,731,681 i6sued May 8. 1973) show6 another infusion pump without appreciable safety features. Blackshear et al do not look for pressure integrity before filling the device with drug, nor teach any means for monitoring pump operation.
Richter (U.S. Patent No. 3,894,538 issued July 15, ,, . :
1975) considers, in a medicine supplying device, one safety feature: an exit plug for preventing, contaminants 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 furthec fails to disclose any means for reliably controlling or varying the flow rate oc for monitoring the rate of operation.
Several eecent 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 "Pco~racted Parenteral ~Z3~8~L
Dcug Infusion in Ambulatory Subjects Using an Implantable Infusion Pump"; American Society for Artificial Internal Organs Transaction, Volume XXIII, 1977) described an implantable infusion pump. No check for pcessuce integrity before filling or during operation, no progcamming means, and no patient or doctor interaction with the device are contemplated.
An article by Spencer ("For Diabetics: an electronic -- pancrea6" IEE-Spectrum; June, 1978) discusses current trends in the implantable drug pump field. Programming the rate of drug flow over time depending on food intake is mentioned.
Efforts in the development of an implantable bellows pump are also discussed. Spencer further mentions the use of an alarm which 60unds if a pump fails to pcovide drug in accordance with the preprogrammed rate. The Spencer article generally discussed drug dispenser technology but fails to address many specific problems. As in the othee cited works, safety featuces such as an antechamber: leak detection; distinctive subcutaneous stimulation to indicate various device malfunctions: safe methods of programming the device regardless of wock, food-intake, or time schedules and telemetering of information pertaining to the actual operation of the pump are not considered.
Finally, German Patent Application DE 31-12916-Al, published February 15, 1982, in the name of Medtronic Inc., teaches an implantable medicine dispensec which is externally programmable. Receipt ox progcamming commands can be verified by an acoustic signal. No means are shown or suggested or ~L~3~
sensing, stocing, and telemetecing information pertaining to aetual pump opecation. As a result, only the instruetions given to this aparatus ean be vecified and ehanges in the physiologieal cesponse of the patient, often detrimental, are the only way to monitoc pump opecation.
Aeeocdingly, an objeet of a broad aspeet o. this invention is to pcovide an impcoved infusion system foc providing medieation to a living body of a patient.
, .,..,. ,., - -......
-3a-1~3~
By a broad aseect of this invention, a programmable infusion system is provided for providing medication to a living body including an infusion apparatus having infusion means for infusing a selected medication stored in a medication reservoir into a living body, the inusion means having a commandable infusion rate which is variable upon command, the infusion apparatus comprising: inhibiting means for inhibiting the infusion means from infusing the selected medication if a preselected medication infusion rate is exceeded.
-The preselected medication infusion rate may be remotely selectable, or may comprise a remotely selectable rate and a fixed rate, the remotely selectable rate being limited to the fixed rate.
The inhibiting means may include at least one means ; for defining a fixed infusion rate limit. Furthermore, the inhibiting means may comprise at least one programmable rate --` memory unit, each of the at least one programmable rate memory units for receiving and storing an infusion rate input command corresponding to the remotely selectable rate; at least one limit control unit, each of the at least one limit control units providing a fixed rate limit; and means for comparing each of the infusion rate input commands to a corresponding fixed rate limit, infusion of the medication at a rate exceeding the fixed rate limit being inhibited.
Alternatively, the inhibiting means may include time dependent means for precluding infusion of the medication by the infusion means when the selected commandable infusion rate ~3~
exceeds the preselected medication infusion rate during a window of time of a predetermined length which shifts continuously.
The infusion means preferably includes a pump means which executes in pulses, and the inhibiting means preferably comprises a programmable memory rate unit for storing initially a dose limit number corresponding to a first maximum number of infusion pulses preselected as allowable during a first shifting time window of a predetermined length, pulse quantitie6 being subtracted from the number 6tored in the programmable memory rate unit as infusion pulses are executed by the infusion means, pulse quantities being added to the stored number as time elapses such that the number does not exceed the first maximum number, the subtraction and addition being accomplished in running integral fashion, and the inhibitlng means not permitting pulsing of the pump means at a rate in excess of the rate represented by the dose limit number stored in the programmable memory rate unit. Preferably, such memory rate unit also records the number of pulses which have , 20 been inhibited and causes the pump means of the infusion means to execute the pulses when the pulses can be subtracted as a result of the elapse of time from the dose limit number stored in the programmable memory rate unit. Furthermore, such programmable memory rate unit may also store initially another dose limit number corresponding to a second maximum number of infusion pulses preselected as allowable during a second shifting time window of a predetermined length, ., -4a-~IZ3~
the second shifting time window being longer in length than the first shifting time window, pulse quantities being subtracted from the other dose limit number stored in the programmable memory rate unit as infusion pulses are executed by the infusion means, pulse quantities being added to the other dose limit number as time elapses 6uch that said another dose limit number does not exceed the first maximum number, the subtraction and addition being accomplished in running integral fashion, and the inhibiting means not permitting pulsing of the eump means at a rate in excess of the rate represented by the other dose limit number stored in the programmable memory rate unit. Still further, the programmable memory unit may also record the number of pulses which have been inhibited and causes the pump means of the infusion means to execute the pulses when the pulses can be subtracted from both the dose limit numbers stored in the programmable memory rate unit.
It is preferred that such inhibiting means further include at least one fixed infusion rate limit which limits the total maximum infusion rate of the infusion mean6.
, 20 The programmable infusion system may include means for recording when the inhibiting means inhibits the infusion means or may include means for generating an alarm signal when any commanded infusion rate results in the inhibiting of pulsing of the pump means by the inhibiting means.
The infusion apparatus is preferably adapted to implantation into a living body.
-4b-., :IZ3~
In the accompanying drawings:
FIG. 1 illustrates a general block diagram of the entire medication infusion system embracing the present invention;
FIGS. 2 and 3 show a front cross-sectional and toe view, respectively, of the implantable portion of a medication infusion system embcacing the pcesent invention;
FIG 4 shows, in detail the mechanical construction of :. a pulsatable pup element of a medication infusion system embracing the present invention;
FIG. 5 is a block diagcam showing the electronics of a medication infusion system embracing the present invention;
FIG. 6 shows a method of programming the rate of medication infusion into a patient by the use of the maximum running integral dosage limiting technique; and FIGS. 7 and 8 are illustrative of a patient programming unit in which FIG. 7 shows a front view illustrating a sample apearatus foc select'ing dosage depending on meal size and recognized body condition factors, and FIG. 8 shows a rear portion which provides infocmation celative to the last programming of the patient programming unit.
Generally, the medication infusion system embracing the present invention pcovides an antechamber which is nocmally filled with saline solution to act as a buffec between the medication intake point and the majoc medication ceservoic in the device. The Leservoir may contain a fatal amount of dcug lZ31Z~l or other medication. It is thus isolated from the body by a filter, one-way inlet valve, the saline-containing antechamber and a septum providing a self-sealing opening to the antechambec. Fuether, the reservoir is at a pressure below the ambient body preS6ure. Thus, even if the inlet valve and seetum leak, body fluids would enter the antechamber and slowly ooze into the reservoic through the flow-impeding filter. Any othec leak of medication from the reservoir or leakage of body fluid thcough the outer shell of the implanting device would be sensed by a fluid detector outside the reservoir. Similar safety back-ups are peovided at the outlet output of the reservoir which is provided with two one-way valves and a filter.
The outlet, however, also is provided with a deformable wall which combines with the outlet filter to yield an exponentially decaying flow of medication. This smooth flow over a long, predertermined period provides enhanced safety and flow control. The deformabie wall serves the function of an accumulator and the output filter provides the function of a flow resistor or restrictor; thus the deformable wall provides the `'C" and the filter "R" of an "RC" time constant or the decrease of flow after a pulse of medication has been delivered into an outlet chamber prior to infusion into the body via the O network. Also at the outlet is an element foe cocrelating medication requests with medication dispensing, thus providing an opecational indicator and safety feature.
, ~L23~
Also, for safety, a filling proceduee i6 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 system embraced by the present invention, 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, peoper medication schedule even though the patient experiences time zone or work schedule changes. In addition to a progcammable rate of medication input, a haedwired 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. Finally, the system provides a history of medication infusion which a physician can read out theough telemetry means. This telemetry means is also used to program and check the system.
Referring to FIG. 1, the varous portions of the implantable programmable medication infusion system embracing the present invention are shown. An implantable portion 2 in a patient's body can be programmed either by the medication progcamming system 1 or by the patients programming unit 3~;~83~
400. Commands from the medication prog{amming system 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 caeable ox reading information out of the implantable portion 2 concecning 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 - 10 medication of the implantable portion 2. 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 to request doses of medication. The ... .....
dosage eequests are contcolled by safey 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, and extecnal charging head 9 connected to a battery charging unit 11 is included. The need for the charging head 9 and battery chacging 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.
~L23~Z13~
Referring now to FIGS, 2 and 3, the implantable poction 2 of an implantable programmable medication infusion system embracing the present invention 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 rubber septum 6 which covers an antechamber 8 in leak-proof fashion.
medication is introduced into the antechamber 8 through syringe 4 under pressure the level of which is controllable externally.
A reservoir chambe{ lO, in which the medication is stored under , .
relatively constant pressure, is fed from the antechamber 8 via a ceramic filter 12 and an inlet pressure valve 14 which permits flow only from the antechamber 8 into the reservoir chamber lO 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 antechambeL 8 into the reservoic 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 ceservoir chamber 10. Further, should the inlet pressure valve 14 and the septum 6 both leak or otherwise malfunction, the inlet ceramic filter 12 would permit only a slow flow of body fluids to enter the rese{voir chamber 1~;3121~
10, until Cody ambient pressure is a~hievçd, at. which time some meditation could diffusç through the ceramic filter 12 but at a rate that would not bQ hazardou,s to a typical pat,ient in which the system would bç implanted.
The rçservoir chamfer 10 comprises a 'liquid-vapour portion 16 which rests atop a reservoir of medication 18, the liquid vapor portion 16 and the reservQir 18 being separated by a flexible diaphragm 20. The flexible diaphragm 20 could comprise an elastomer, a Moveable bellows, or othçr substitutive lexible diaphragm means Nhich wol~ld ,separate the meditation reservoir 1~3 from the liquid portion 16. The liquid vapor volume in the vapor portion 16 prefsrably ~ompri~e.s a saturated vapor in equilibrium with a small amount of FREON 113 (registered trade mark of a fluorocarbon refrigerant) liquid.
Over normal body temperatures, FREON 1 13 has a linear pressure characteristic ranging from -4 psig Nat 98) to approximately
This invention relates to a programmable infusion system for providing medication to a living body and is a division of copending application Serial No.417,979 filed December 17, 1982, now allowed.
The present invention relates to the field of dispensing medication to a living being. Although mainly intended for use by human patients requiring infusions of a drug, e.g. insulin, glucose, heparin, or any of various other chemotherapeutic agents, the invention extends to use in any living body te.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 implantable devices, it i6 also envisioned that it could be used external to a living being for the infusion of medication.
Various techniques and devices have been suggested and are currently under study which address the problem of dispensing a drug or other medicative liquid into a living body. Of these techniques and devices, however, sufficient , 20 safety features in the environment of the flexibility achieved by programming dosage ineuts are rarely contemplated.
One liquid infusion device discussed in U.S. Patent No. 4,077,405 issued March 7, 1978 to Haerton et al discloses a controllable dosing arrangement which provides for human operator interaction. syringe forces liquid through a ~Z31Z~
pressure valve into a supply reservoir and a bellows pump forces drug from the reservoir through a flow limiter into the body. This device fails to address various safety problems, e.g. leakage, excessive pumping, and excessive requests for drug. No provision for detecting leaks in the device, for signalling malfunctions, for restricting the number of or quantity of drug doses, or for monitoring proper operation of the device is suggested.
~123~
ike Haeeton et al, U.S. Patent No. 3,692,027 issued September 10, 1972 to Ellinwood teaches an implanted, self-powered drug dispenser having a bellows pump which employs one-way valves. The Ellinwood device i6 not progeammable and varies dosage by opening and closing portals or selecting a dose of medication from one of a plucality of pumps having different dosage volumes and/or different medications stored therein. Safety redundancy pertaining to filling, leakage ;:::; ..
problems, patient and doctoc interaction with the dispenser, and dosage input programming are not considered.
An invention of Blackshear et al (U.S. Patent No.
3,731,681 i6sued May 8. 1973) show6 another infusion pump without appreciable safety features. Blackshear et al do not look for pressure integrity before filling the device with drug, nor teach any means for monitoring pump operation.
Richter (U.S. Patent No. 3,894,538 issued July 15, ,, . :
1975) considers, in a medicine supplying device, one safety feature: an exit plug for preventing, contaminants 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 furthec fails to disclose any means for reliably controlling or varying the flow rate oc for monitoring the rate of operation.
Several eecent 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 "Pco~racted Parenteral ~Z3~8~L
Dcug Infusion in Ambulatory Subjects Using an Implantable Infusion Pump"; American Society for Artificial Internal Organs Transaction, Volume XXIII, 1977) described an implantable infusion pump. No check for pcessuce integrity before filling or during operation, no progcamming means, and no patient or doctor interaction with the device are contemplated.
An article by Spencer ("For Diabetics: an electronic -- pancrea6" IEE-Spectrum; June, 1978) discusses current trends in the implantable drug pump field. Programming the rate of drug flow over time depending on food intake is mentioned.
Efforts in the development of an implantable bellows pump are also discussed. Spencer further mentions the use of an alarm which 60unds if a pump fails to pcovide drug in accordance with the preprogrammed rate. The Spencer article generally discussed drug dispenser technology but fails to address many specific problems. As in the othee cited works, safety featuces such as an antechamber: leak detection; distinctive subcutaneous stimulation to indicate various device malfunctions: safe methods of programming the device regardless of wock, food-intake, or time schedules and telemetering of information pertaining to the actual operation of the pump are not considered.
Finally, German Patent Application DE 31-12916-Al, published February 15, 1982, in the name of Medtronic Inc., teaches an implantable medicine dispensec which is externally programmable. Receipt ox progcamming commands can be verified by an acoustic signal. No means are shown or suggested or ~L~3~
sensing, stocing, and telemetecing information pertaining to aetual pump opecation. As a result, only the instruetions given to this aparatus ean be vecified and ehanges in the physiologieal cesponse of the patient, often detrimental, are the only way to monitoc pump opecation.
Aeeocdingly, an objeet of a broad aspeet o. this invention is to pcovide an impcoved infusion system foc providing medieation to a living body of a patient.
, .,..,. ,., - -......
-3a-1~3~
By a broad aseect of this invention, a programmable infusion system is provided for providing medication to a living body including an infusion apparatus having infusion means for infusing a selected medication stored in a medication reservoir into a living body, the inusion means having a commandable infusion rate which is variable upon command, the infusion apparatus comprising: inhibiting means for inhibiting the infusion means from infusing the selected medication if a preselected medication infusion rate is exceeded.
-The preselected medication infusion rate may be remotely selectable, or may comprise a remotely selectable rate and a fixed rate, the remotely selectable rate being limited to the fixed rate.
The inhibiting means may include at least one means ; for defining a fixed infusion rate limit. Furthermore, the inhibiting means may comprise at least one programmable rate --` memory unit, each of the at least one programmable rate memory units for receiving and storing an infusion rate input command corresponding to the remotely selectable rate; at least one limit control unit, each of the at least one limit control units providing a fixed rate limit; and means for comparing each of the infusion rate input commands to a corresponding fixed rate limit, infusion of the medication at a rate exceeding the fixed rate limit being inhibited.
Alternatively, the inhibiting means may include time dependent means for precluding infusion of the medication by the infusion means when the selected commandable infusion rate ~3~
exceeds the preselected medication infusion rate during a window of time of a predetermined length which shifts continuously.
The infusion means preferably includes a pump means which executes in pulses, and the inhibiting means preferably comprises a programmable memory rate unit for storing initially a dose limit number corresponding to a first maximum number of infusion pulses preselected as allowable during a first shifting time window of a predetermined length, pulse quantitie6 being subtracted from the number 6tored in the programmable memory rate unit as infusion pulses are executed by the infusion means, pulse quantities being added to the stored number as time elapses such that the number does not exceed the first maximum number, the subtraction and addition being accomplished in running integral fashion, and the inhibitlng means not permitting pulsing of the pump means at a rate in excess of the rate represented by the dose limit number stored in the programmable memory rate unit. Preferably, such memory rate unit also records the number of pulses which have , 20 been inhibited and causes the pump means of the infusion means to execute the pulses when the pulses can be subtracted as a result of the elapse of time from the dose limit number stored in the programmable memory rate unit. Furthermore, such programmable memory rate unit may also store initially another dose limit number corresponding to a second maximum number of infusion pulses preselected as allowable during a second shifting time window of a predetermined length, ., -4a-~IZ3~
the second shifting time window being longer in length than the first shifting time window, pulse quantities being subtracted from the other dose limit number stored in the programmable memory rate unit as infusion pulses are executed by the infusion means, pulse quantities being added to the other dose limit number as time elapses 6uch that said another dose limit number does not exceed the first maximum number, the subtraction and addition being accomplished in running integral fashion, and the inhibiting means not permitting pulsing of the eump means at a rate in excess of the rate represented by the other dose limit number stored in the programmable memory rate unit. Still further, the programmable memory unit may also record the number of pulses which have been inhibited and causes the pump means of the infusion means to execute the pulses when the pulses can be subtracted from both the dose limit numbers stored in the programmable memory rate unit.
It is preferred that such inhibiting means further include at least one fixed infusion rate limit which limits the total maximum infusion rate of the infusion mean6.
, 20 The programmable infusion system may include means for recording when the inhibiting means inhibits the infusion means or may include means for generating an alarm signal when any commanded infusion rate results in the inhibiting of pulsing of the pump means by the inhibiting means.
The infusion apparatus is preferably adapted to implantation into a living body.
-4b-., :IZ3~
In the accompanying drawings:
FIG. 1 illustrates a general block diagram of the entire medication infusion system embracing the present invention;
FIGS. 2 and 3 show a front cross-sectional and toe view, respectively, of the implantable portion of a medication infusion system embcacing the pcesent invention;
FIG 4 shows, in detail the mechanical construction of :. a pulsatable pup element of a medication infusion system embracing the present invention;
FIG. 5 is a block diagcam showing the electronics of a medication infusion system embracing the present invention;
FIG. 6 shows a method of programming the rate of medication infusion into a patient by the use of the maximum running integral dosage limiting technique; and FIGS. 7 and 8 are illustrative of a patient programming unit in which FIG. 7 shows a front view illustrating a sample apearatus foc select'ing dosage depending on meal size and recognized body condition factors, and FIG. 8 shows a rear portion which provides infocmation celative to the last programming of the patient programming unit.
Generally, the medication infusion system embracing the present invention pcovides an antechamber which is nocmally filled with saline solution to act as a buffec between the medication intake point and the majoc medication ceservoic in the device. The Leservoir may contain a fatal amount of dcug lZ31Z~l or other medication. It is thus isolated from the body by a filter, one-way inlet valve, the saline-containing antechamber and a septum providing a self-sealing opening to the antechambec. Fuether, the reservoir is at a pressure below the ambient body preS6ure. Thus, even if the inlet valve and seetum leak, body fluids would enter the antechamber and slowly ooze into the reservoic through the flow-impeding filter. Any othec leak of medication from the reservoir or leakage of body fluid thcough the outer shell of the implanting device would be sensed by a fluid detector outside the reservoir. Similar safety back-ups are peovided at the outlet output of the reservoir which is provided with two one-way valves and a filter.
The outlet, however, also is provided with a deformable wall which combines with the outlet filter to yield an exponentially decaying flow of medication. This smooth flow over a long, predertermined period provides enhanced safety and flow control. The deformabie wall serves the function of an accumulator and the output filter provides the function of a flow resistor or restrictor; thus the deformable wall provides the `'C" and the filter "R" of an "RC" time constant or the decrease of flow after a pulse of medication has been delivered into an outlet chamber prior to infusion into the body via the O network. Also at the outlet is an element foe cocrelating medication requests with medication dispensing, thus providing an opecational indicator and safety feature.
, ~L23~
Also, for safety, a filling proceduee i6 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 system embraced by the present invention, 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, peoper medication schedule even though the patient experiences time zone or work schedule changes. In addition to a progcammable rate of medication input, a haedwired 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. Finally, the system provides a history of medication infusion which a physician can read out theough telemetry means. This telemetry means is also used to program and check the system.
Referring to FIG. 1, the varous portions of the implantable programmable medication infusion system embracing the present invention are shown. An implantable portion 2 in a patient's body can be programmed either by the medication progcamming system 1 or by the patients programming unit 3~;~83~
400. Commands from the medication prog{amming system 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 caeable ox reading information out of the implantable portion 2 concecning 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 - 10 medication of the implantable portion 2. 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 to request doses of medication. The ... .....
dosage eequests are contcolled by safey 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, and extecnal charging head 9 connected to a battery charging unit 11 is included. The need for the charging head 9 and battery chacging 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.
~L23~Z13~
Referring now to FIGS, 2 and 3, the implantable poction 2 of an implantable programmable medication infusion system embracing the present invention 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 rubber septum 6 which covers an antechamber 8 in leak-proof fashion.
medication is introduced into the antechamber 8 through syringe 4 under pressure the level of which is controllable externally.
A reservoir chambe{ lO, in which the medication is stored under , .
relatively constant pressure, is fed from the antechamber 8 via a ceramic filter 12 and an inlet pressure valve 14 which permits flow only from the antechamber 8 into the reservoir chamber lO 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 antechambeL 8 into the reservoic 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 ceservoir chamber 10. Further, should the inlet pressure valve 14 and the septum 6 both leak or otherwise malfunction, the inlet ceramic filter 12 would permit only a slow flow of body fluids to enter the rese{voir chamber 1~;3121~
10, until Cody ambient pressure is a~hievçd, at. which time some meditation could diffusç through the ceramic filter 12 but at a rate that would not bQ hazardou,s to a typical pat,ient in which the system would bç implanted.
The rçservoir chamfer 10 comprises a 'liquid-vapour portion 16 which rests atop a reservoir of medication 18, the liquid vapor portion 16 and the reservQir 18 being separated by a flexible diaphragm 20. The flexible diaphragm 20 could comprise an elastomer, a Moveable bellows, or othçr substitutive lexible diaphragm means Nhich wol~ld ,separate the meditation reservoir 1~3 from the liquid portion 16. The liquid vapor volume in the vapor portion 16 prefsrably ~ompri~e.s a saturated vapor in equilibrium with a small amount of FREON 113 (registered trade mark of a fluorocarbon refrigerant) liquid.
Over normal body temperatures, FREON 1 13 has a linear pressure characteristic ranging from -4 psig Nat 98) to approximately
-2.5 psig at 104F. Using FREON 113, the medication reservoir 18 will be maintained at a pressure below that of the human body pressure up to altitudes of 8500 feet. For patients who may live ahove that altitude, ot,her fluorocarbon.s at lower pressure may ke employed. In this way, should both the septum 6 and the inlet pressure valve 14 leak, the effect would be to cause body fluids to diffuse slowly, via the inlçt cçramic filter 12, into the medication reservoir l rathçr than to have a rapid flow of medication enter the body where it could cause harm to the patient. Because of the pres,sure differential ~LZ3~Z~l between the body and the medication re.servoir l medication will not. flow from the re.servoir l into the body. A.s the amount of medication in the medicat,ion reservoir l varle.s, t,he flexible diaphragm 20 move up or down, with the FREON 113 being converted zither from livid to vapor, or from vapor to liquid to provide an essentially constant pressure which will always be below one atmosphere and bQIow normal body pressure.
A reservoir chamber having a volume of approximately 10 cc would ye sufficient for most application.s. This amount of concçntrated medication, insulin for example, could be fatal if injected over a short time. The volume of the antechamber is le,ss than 1Q% the size of the reservoir chamber 10. In the wor.st ca.se of leakage if medication leaked from the reservoir chamber 10 into the antechamber and even if the antechamher leaked as well, only diluted medication would ent,er the body gradually passing from an area of low pressure to one of higher pre.ssure. There 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 would be a simple modification of the arrangement of elements in the system. Included in the reservoir chamber 10 is a dual pressure .switch which can comprise a reservoir fill switch 23 for indicating when the pre.ssure in the reservoir chamber 10 reaches a predetermined level, e.g. -2 psig, and a second switch 25 for indicating when the pressure reaches -1 p.sig. Fill switch 2~ is used during ~Z3~
the fllling pr~edure to indicate (hy telemetry system to be decried later) when the level of medication in the reservoir chamfer 1 n has reached a ~L23~
specific value. Should body fluids leak into the medication resecvoir 18 for any reason, an increase in pressure would result that would activate the second pees6ure switch 25. For examele, when body f luids entering reservoir 18 reach eressure of -1 psig, this would set off a subcutaneous electrical stimulation alarm system. By having the fill switch 23 set at a lower pres6ure than the body fluid leak detection pres6ure switch 25, the filling of the reservoir 18 can be accomplished without setting off an alarm signal.
10In order to fill the reservoir chamber 10 with medication, a sequence ox steps is hollowed. The antechamber 8 i5 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 is directed into the antechamber 8 and saline is introduced into the antechamber 8 through one needle and exits through the other in order 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 desired medication (e.g.
insulin). Medication is then forced into the antechamber 8 at a pressure greater than what required to open inlet pressure valve l The insulin fills the medication reservoir 18 of the reservoir chamber 10 until the flexible membrane 20 ~23~'~8~
contacts the dual prey re witch 22, forcing t,he re~ervoi.r fill witch 23 to generate a signal, (e.g. at -2 prig), which indicates that the fill.ing has been completed. The amo-lnt of medication required to fill the medication reservoir l is noted and then t,he anteGhamber B I 1u~hed once agQin ilk innocuous saline solution. The entire reservoir chamber 10 is surrounded my a wall 24 and is isolated Erom the ot,her foment of the ~y~tem by mean of the inlet pressure valve 14 and an interface pre~ure valve 2~ which connects the reservoir t,o a pulsatile pump 2~ which it shown in FIG. 4. The remaining element of the implant,ed portion 2 are alto shown in FIG. 2:
an electronic section 30 with a battery ~ub~ection 32. As is already seen in Fig. 2, a hermeti.cally sealed enclosure 34 surrounds the re~erVQir Ghamber 10 a well as the pulsQtile pump 2~ (see FIG. 4) and the electronic section 30 with the battery subjection 32. To provide an enhanced safety feature, a fluid detector 35 it provided between the wall 24 and the hermetically sealed enclosure 34. Should either the outer hermetic enclosure 34, or the reservoir chamber 10 leak, the fluid detector 35 it placed at a 1OcQtion where the leaking hody fluids or medication would be detected. The fluid detector 35 cQuld be a very high re~i~tQnce resistor, (e.g. 10 megohms), whose reliance drops significantly in the preæence of fluid. A malfunction signal to warn the patient if such leak is detected, it provided. similarly, a medication leakQge ~;233~
- 1~a -det~tor 37 in the liquid-va~or voll~lm~ 16 wollld indi~atQ ~h~n m~di~atiQn way leaking into that ~h~m~or ~3~
16. Thi6 detector may also be a ce6istor whose value will be significantly altered by the presence of the medication. The medication leakage detectoc 37 when actuated would set off a distinct subcutaneous electeical stimulation alarm signal that can be detected hy the patient.
FIG. illustrates the pulsatile pump 28 shown in the top view of the implanted eoction 2 shown in FIG. 3. The interface pressure valve 26 shows where medication entecs the pulsatile pump 28 when the diffecential in peessuee between the reservoir chamber 10 and a medication storing means 200 (inside the pulsatile pump 28) reaches a level sufficient to open the inlet pressuee valve 26. In the preferred embodiment shown in FIG. 4, this diffeeential in pressure is caused by the expansion of a spring bellows 202 in response to an electrical pulse intcoduced to a pulsing coil 204 which surrounds a plate 206 which is attached to the spring bellows ~02. When a pulse passes through the pulsing coil 204, plate 206 is dciven 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 stocing means 200. The plate 206 is a permanent magnet (oe, possibly, a magnetizable material) which moves in eesponse to a current induced magnetic focce. When 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 -lq-:~L;Z3~Z~
and independent of the electrical pulse current or pulse width into the pulsing coil Z04 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, PmaX=F/A
:: where PmaX is the maximum pre5sure that can be created by the speing foece of the bellows within the medication storing means 200, F is the spring focce of bellows 202, and A is the portion o 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 sequence of rapid pulses be introduced to the pulsing coil 204, causing the plate 206 to reciprocate, the ... return 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 PmaX. The pressure builds up rapidly because of the output flow resistance caused by the ceramic filter 218. The possibility of introducing drugs or other medication at an unsafe high pressure or high rate is thus essentially eliminated.
An outlet pressure valve 21Z 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 ;iL23~2~
increasç in pressure in the storing means 200 re~:ults. When the pressure differential betwçen the pressllre in the storing means 20~ and thç pressure outlet chamber 214 exceeds that required to open outlet pres~;ure valve 212, medication flowæ
into outlet chamber 214 from the medication storing means 200.
To prevent large spurt,s or pul~;es of medication from entering the hody over a short period of time, an ela~:tic wall 216 and an output ceramic filter 21~ are provided at the entrance to the outlet 220 of outlet chamber 214. The output ceramic filter 218 serve.s to resi,st the flow of medication from the outlet chamber 214 into the living body. The elastic wall 216 acts as a type of capacitance to flow, deforming when a pulse of medication it; fed into the outlet chamber 214, the elastic wal] 216 thus serving as a fluid accumulator. The combination of thQ ela,stic wall 216 and the output ceramic filter 21 comprises; a fluid or mechanical RC network that providers medication into the body within an initial rise followçd by a decaying flow. The time constant which i.s fairly long, is determined hy the elasticity of the elastic wall 216 and the resirstance of th~3 output ceramic filtçr 218. In addition, thç
output ceramic filter 21~ disallows medication from being diffu~;ed into the body at a high rate, should both the interface pressure valve 26 and the outlet pressure valve 212 fail to seal.
lZ3~Z~
- 16 a hollld valve 212 leak, there would ye a slow diffll,sior of medicatiQn through the ceramic filter 218 until the pre~sur~
in the stor.ing mean 2 no i.5 essentially equal to ~3~Z~
ambient body pressure. However, since the volume mean 200 i6 very 6mall and since the medication fluid is essentially incompressible, vec~v little medication can difuse out and that amount only at a slow rate. Should both valve 26 and 212 leak, body fluids would then diffuse into the eeservoir 18 because it is at a pressure below body ambient pressure. A
rise in pressure in the medication reservoir 18 relative to that of the ambient body pressure would cause the -1 psig switch to be activated setting off an alarm. Further, the medication then could not difuse 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 speing force which gives a maximum pressure, Pmax, f --I 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. The resistance of the outeut ceramic filter 21B 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 ~3~;281 in either direction, from thy outlet chamber 214 into the body or fcom the body into the outlet chamber 214. Also included in the pulsatile pump 28 i8 a pee6sure transducer 2Z2 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 pres6ure transducer 222 eroduces an electrical output when a pressure pulse of medication enters the outlet chamber 214.
he peessure transducer 222, in other words, detects the pressure pulses which are peovided each time the spring bellows 202 returns the plate 206 to its ociginal posi-tion against backstop 210. By comparing the pulsing from pulsing coil 204 with the pulsing generated by pressure transducer 222, an indication is given as to whether an absence or insufficient number of pulses or medication have been provided to the body. An indication of extra pulses of medication compared to I: the number of electrical pulses may also be provided.
The pulsing signal to pulsing coil 204 as well as the eulse output from the pressure transducer 222 are better understood with reference to FIG. 5 a block diagram of the electronics section 30 shown in FIGS. 2 and 3. As seen in FIG. 5, the electronics section 30 communicates with a communication head 300 which is external to the body, communicating through skin S by means of radio signals which includes an alternating magnetic field. The communications head 300 provides both power inputs and commands, including programmable inputs, to the electronics section 30. Power is 23~
provided by means of an alternat,ing field, e.g., a magnetic Eield, which I comml.lnicated I:o a pickup coil 304 s7hich it;
implant,ed together wit,h the ret of the electronic ection 30 in the body. The pickup coil 304 regive an AC power ~3ignal from communication; hçad 300 and pees it on to a ull wave rectifier 306. One rectified output from the full wave rectifier 306 enter; a batter charge cont,rol ~08 which provides;
a fixed DC charging signal to a power cell 310. The power cell 310 can be a nickel-cadmium cell which is readily rechargeahle off a rectified ~;ignal at a typiGal frequency of 20 kHz.
Alternat,ively, a lithium-type .~olid state l~attery can be u:~;ed in~3tead of the nickel-cadmium cell, in which case the charging circuitry would be eliminated, the lithium-type battery providing :~ufficient power over a long te3rm, therehy obviating the need for recharging. The power cell 310 provide.s a bia~;ing voltage to a tran~ tor switch 312, the output of which enter:
the pulsing coil 204 previously described in the context of the pul~;atile pump 28. In addition to providing power to the powçr cell 310, rectified power it al.~o introduced to a DC to AC
converter 314 the purpose of which it; to provide power at the proper level to the various load in the :~ys~;tem. In addition to the A. power signal, pickup coil 304 alto receive a train of ~:erial digital lit from the communication head 3Qn. The digital bit comprise command for programmak-le input: which are conveyed, via the pickuE~ coil 304 to a command receiver 316. The ~:ignal~ from the command receiver 316 enter ~L~3~LZ~3~
a command decoder l whlch dçtçrmines if the digital bit arQ
in a proper sç~uen~e and, if Jo, what action in the systçm thç
command.s dictate. It should bç noted that the full wave rectifier 30~, the buttery chargç controller 308, the command receiver 316, and the command decoder 31t3 are powçred only when an A signal is pickçd up hy the pickup coil 304. This, of course, prevents the possibility of detecting stray signals a commands and provides power savings. To be sure, the pnwer .saving.s achieved could make possible the use of thç
aforementioned lithium cell which would not require recharging.
From the command decoder 31~, programmable inputs and othçr commands can bç prQvided to a number of elements. A
programmable base rate iæ entçred into a basç rate memory unit 320 which storçs a value indicating thç number of pulses of medication which are requested to be provided to a patient during a normal preselectçd pçriod of time. A second programmable input is provided, namçly a patient-controlled ratç mçmory unit 322 which stores a value indicating a number of pulses of medication that are requested to be introduced into the body over a given period of time during which the patient çatrs a meal or otherwise alters the chemical balance of the body (as by e.~ercising). Associated with the base rate memory unit 320 is a hardwired base ratç limit control 324 which jets a maximum rate that can override requests of the base rate memory unit 320 which are exce~ive. similarly, a hardwired patient controlled rate limit control 326 provides a ~L~3~'~8~
fixed maximum number of pul.ses which Jan by provided at, a time after a meal or at other times and unrler other conditions. As lQng AS the base rat,e and the patient,-controlled rate values stored in memory unit 320 and 322 respectively, do not exceed the hardwirQd values fixQd within limi-t controls 324 and 326, re~spectivQly, an out,put pulse is provided to the input of transistor switch 312 to stimulAte Q pulsQ output from pul.sing coil 204. Should the rate of either memory unit 320 or 322 exceed the hardwired limits in the limit cont,rol elQmQnts 324 or 32~ respectivQly, a "rate request exeeds limit" signal is fed from the limit, control elemQnt 324 or 32h into a programmable alarm generator 32~ which providçs an electricil signal to the stimulation electrode 330 implanted rsubcutaneQIlsly. my means of the stimulation electrQde 330, the patiQnt is inormed, by meanrs of subcutaneous .stimulation, that one of the memory unit-s 32Q or 322 is re~uersting more -than the maximum all ow able number of pulse.s.
It should be noted that thç signal to the stimulation electrode 330 can serve the dual function not only of providing the patient with a subcutaneous eleGtrical rstimulation, but also may be the .source of a signal detected by the communication head 300 communicated either to the patient or to his physician or hoth, that, a failure has occurred. As shown in FIG. 5, the electrode 330 will ke isolated and should be insulated from the outside o-E the hermetically-sealQd enclosure 34 of the implanted portion 2.
~23~
A particularly significant featllre of the inl1~ion system emkracing aspectæ of the present invention re,sides in the programmabilit.y of t.he alarm generator 32~ based on inpl1t command from the Gommand decoder 31~. The alarm generator 328 can bQ swit.ched on or off and the voltage produced by thç
generator, and henGe to the elçGtrode 330, can be varied in response to signal emanating from the communication hçad 300 and channeled through the command reGsiver 31Ç to the Gommand decoder 31~. In addition, to Gheck the proper operation of the system, the command decoder 31~ can receive test .signals whish can simulate actual occurrences to detçrmine whether the Gir~uitry in the eleGtroniG section 30 is operating properly.
For example, extra pul.~es from the command decoder 31~3 Gan bç
enterçd into the hardwired limit control elements 324 and 32Ç.
These extra pulses can ye added to the pulse pro~idçd by the bate rate and the patient-controlled rate memory units in order to ex~eçd the hardwirçd base rate and the hardwired patient-controlled rate, respectivçly. When the rates are e~ceQded, the alarm generator 323 will providç a signal. In this way, the alarm generator 32~3 can be used to check the operation of thç limit Gontrol elements 324 and 32Ç and also to familiarize the patient with the corresponding subcutaneolls signals emittçd by the tickle elect.rode 330. The programmable alarm gçnerator 328 also receiYes inputs from the pressure switch 22 and the fluid detector 35, both shown in FIX. 2. If body fluids leak ~Z3~
- ~2~ -into the reservoir l the prQ~sl~re with 2.5 wi]l be activated, indicating this fault condition to the patient by means of the activati,on of -the a].arm generator 32~ and t,he electrode 3~0. If thy patient was llncon~ciol.ls, voltage levels of the p~tlent'~ skin at the site of the implanted portion 2 1231'~
could be used by the phsyician to indicate if a malfunction has occurred and which malfunction it was. Further, as previously described, should fluid leak out of the reservoir chamber 10 and onto the lining of the enclosure 34 or, alternatively, if body fluid should leak in through the enclosure 34, the fluid detector 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 genecator 320 comes from the power cell 310 associated with transistor switch 312. The voltage level of the vower 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, referring 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 decode 318. If the number of pulses sensed by the pressure transducer 222 over a specified period of time are less than the number of eulses associated with the "insufficient rate" command input, a pulse rate detector 332 will provide an output indicating that an insufficient amount of medication is being provided to the patient over the specified time. The output of pulse rate detector 332 (FIG.
5) also enters the tickle generator 328 to provide a subcutaneous tickle detectable by the patient. It should be noted that the various mentioned failures in the system result in subcutaneous stimulations each of which may be different in stimulation magnitude, duration, or periodicity. For example, ~23~2~
the stimulation may range between one to four vo]ts and may very in frequency abovç and below 20 pulses per second and mo.~t importantly, a. variety oE pulse patterns may be used each uni.que to a particular malfunct.iQn or warning. Additional warnings that m.ight be used are: (1) meditation has leaked into the liquid-vapQr volume; (2) only 1Q% of the medication remain.c in the reservoir; and (.3) onl.y 5 days medisation remains.
In addition to pulsing the pump toil 204, the outputs of the ].imit çontrol elements 324 and 326 al.so provide input to a pulse recorder 334. Pulse recorder 334 maintains a running history of how many ele~tri~al pulsss have been prov.ided to the pulsatile pump 28 singe the last refill of thç reservoir 18 (in FIX. 1). An "interrogate" signal from the command decoder 318 instructs the pulse reorder 334 to provide the history to a telemetry transmitter 336 which communicates the pulse history to a telemçtry coil 33~3. The pulse recorder 334 would record both t.he number of pulsçs delivered to the pumping coil 204 and the number of puts detected by the pressure transducer 222 and/or the difference between these two numbers. The telemetry coil 33~3, in turn, providçs its output thrQugh radio frequency signals to a telemetry-receiving antenna in the communication head 300. In addition to the pulse history, the telçmetry transmitter 336 also rç~eives, during programming, inputs from the base rate memory unit 320 and patient-~ontrolled rate memory unit 322 which are transmitted hack to the communication head 30Q indicating that the desired base rate and patient contro].led rate, respectively, have been programmed ~L~3~
in the corresponding memory unit 32 or 322. Similarly, other key parameterc 337 of the system are alGo conveyed by means of the telemetry tcansmitter 336 back to the communication head 300. For example, the exact pcessure transducer output wavefoLm would be telemetered. Of course, the pressure wavefoem 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 feom 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 signals, and power cell charging.
Reference is now made to FIG. 6 which shows a method of programming the patient controlled memory untit 322. The significance o 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 thecefore would be effective regardless of the patients eating or working schedule, which 3L~23~
schedule change might be a cesult of the patient changing time zones. In the sample gcaph 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. These rate settings can, of course, be altered depending on eatient needs and medication to be administered and time periods other than four hours or 24 hours could be used. In FIG. 6, the number of pulses i6 shown as function of time.
In Fig. 6, at midnight, the number of pulses that are allowed in the four hour period is eight. Shortly-after 8 A.M. five pulses are requested diminishing the number of additional pulses allowed to three pulses. Prior to noon, within the four hour time peeiod, a five pulse request is entered. In accordance with the maximum running integral four hour restraint, only three pulses are permitted but the remaining two pulses in the request are stored in the memory unit 322 (FIG. S) 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, OL shortly before 4 P.M. Shortly before 4 P.M. the three pulse allowance is automatically raised to six pulses, accounting for the three ~3~
pulses executed just befoce noon. Shortly after 4 P.M., thy allowance automatically rises to eight pulses theceby 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 before 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 York schedules a patient may go theough 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.
Referring now to FIG. 7, the front view of a patient . .
programming unit 400 is shown. In the center of the unit is a dial 402 which can be rotated to indicate,the size of a meal eaten by the patient or the amount of exercise he had undergone, in order to provide inputs indicating the amount of medicàtion needed. Output from the patient programming unit 400 is detected by the pickup coil 304 of FIG. 5 as commands.
Whether or not the request is valid is determined in the electronic section 30 and is conveyed back to the patient programming unit 400 by telemetry. signal by the patient programming unit 400 to the patient indicates whether his request has been satisfied. The patient programming unit 400 ~23~
will be provided both with audio and visual outputs rendering it particularly useful for those patients having either visual or hearing handicaps.
In FIG. 8 is the rear view of the patient programming unit 400. The rear side of the patient programming unit 400 will provide inormation 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 pcogramming ROMS (not shown) in the patient programming unit 400 in accordance with the running integral programs shown in FIG. 5 an "OK" or "TOO
MUCH REQUESTED" video and/or audible output can be provided.
The audio output would emanate from the loudspeaker 405. When the request leads to the dispensing of a pulse or pulses of medication into the outlet chambert, a "MEDICATION SENT" signal from the implanted portion 2 is relayed to the patient programming unit 400 to actuate an audio indication by loudspeaker 405 or by visual means.
It should be understood that alternative embodiments ' 20 are contemplated for the infusion system embcacing the eresent invention. For example, the antechamber 8 can comprise a vitreous carbon insert in the skull, or other suitable, accessible elace on the body, coueled with a tube directed to the reservoir chamber lO which may be located in the torso.
The filling procedure and elements o antechamber 8 (e.g., the septum 6) would remain the same with the vitreous carbon insert. The inlet pressure valve 14 and filter 12 would 6till ~231~
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 lB (of FIG. 1) has been filled, the pulse history 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.
A reservoir chamber having a volume of approximately 10 cc would ye sufficient for most application.s. This amount of concçntrated medication, insulin for example, could be fatal if injected over a short time. The volume of the antechamber is le,ss than 1Q% the size of the reservoir chamber 10. In the wor.st ca.se of leakage if medication leaked from the reservoir chamber 10 into the antechamber and even if the antechamher leaked as well, only diluted medication would ent,er the body gradually passing from an area of low pressure to one of higher pre.ssure. There 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 would be a simple modification of the arrangement of elements in the system. Included in the reservoir chamber 10 is a dual pressure .switch which can comprise a reservoir fill switch 23 for indicating when the pre.ssure in the reservoir chamber 10 reaches a predetermined level, e.g. -2 psig, and a second switch 25 for indicating when the pressure reaches -1 p.sig. Fill switch 2~ is used during ~Z3~
the fllling pr~edure to indicate (hy telemetry system to be decried later) when the level of medication in the reservoir chamfer 1 n has reached a ~L23~
specific value. Should body fluids leak into the medication resecvoir 18 for any reason, an increase in pressure would result that would activate the second pees6ure switch 25. For examele, when body f luids entering reservoir 18 reach eressure of -1 psig, this would set off a subcutaneous electrical stimulation alarm system. By having the fill switch 23 set at a lower pres6ure than the body fluid leak detection pres6ure switch 25, the filling of the reservoir 18 can be accomplished without setting off an alarm signal.
10In order to fill the reservoir chamber 10 with medication, a sequence ox steps is hollowed. The antechamber 8 i5 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 is directed into the antechamber 8 and saline is introduced into the antechamber 8 through one needle and exits through the other in order 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 desired medication (e.g.
insulin). Medication is then forced into the antechamber 8 at a pressure greater than what required to open inlet pressure valve l The insulin fills the medication reservoir 18 of the reservoir chamber 10 until the flexible membrane 20 ~23~'~8~
contacts the dual prey re witch 22, forcing t,he re~ervoi.r fill witch 23 to generate a signal, (e.g. at -2 prig), which indicates that the fill.ing has been completed. The amo-lnt of medication required to fill the medication reservoir l is noted and then t,he anteGhamber B I 1u~hed once agQin ilk innocuous saline solution. The entire reservoir chamber 10 is surrounded my a wall 24 and is isolated Erom the ot,her foment of the ~y~tem by mean of the inlet pressure valve 14 and an interface pre~ure valve 2~ which connects the reservoir t,o a pulsatile pump 2~ which it shown in FIG. 4. The remaining element of the implant,ed portion 2 are alto shown in FIG. 2:
an electronic section 30 with a battery ~ub~ection 32. As is already seen in Fig. 2, a hermeti.cally sealed enclosure 34 surrounds the re~erVQir Ghamber 10 a well as the pulsQtile pump 2~ (see FIG. 4) and the electronic section 30 with the battery subjection 32. To provide an enhanced safety feature, a fluid detector 35 it provided between the wall 24 and the hermetically sealed enclosure 34. Should either the outer hermetic enclosure 34, or the reservoir chamber 10 leak, the fluid detector 35 it placed at a 1OcQtion where the leaking hody fluids or medication would be detected. The fluid detector 35 cQuld be a very high re~i~tQnce resistor, (e.g. 10 megohms), whose reliance drops significantly in the preæence of fluid. A malfunction signal to warn the patient if such leak is detected, it provided. similarly, a medication leakQge ~;233~
- 1~a -det~tor 37 in the liquid-va~or voll~lm~ 16 wollld indi~atQ ~h~n m~di~atiQn way leaking into that ~h~m~or ~3~
16. Thi6 detector may also be a ce6istor whose value will be significantly altered by the presence of the medication. The medication leakage detectoc 37 when actuated would set off a distinct subcutaneous electeical stimulation alarm signal that can be detected hy the patient.
FIG. illustrates the pulsatile pump 28 shown in the top view of the implanted eoction 2 shown in FIG. 3. The interface pressure valve 26 shows where medication entecs the pulsatile pump 28 when the diffecential in peessuee between the reservoir chamber 10 and a medication storing means 200 (inside the pulsatile pump 28) reaches a level sufficient to open the inlet pressuee valve 26. In the preferred embodiment shown in FIG. 4, this diffeeential in pressure is caused by the expansion of a spring bellows 202 in response to an electrical pulse intcoduced to a pulsing coil 204 which surrounds a plate 206 which is attached to the spring bellows ~02. When a pulse passes through the pulsing coil 204, plate 206 is dciven 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 stocing means 200. The plate 206 is a permanent magnet (oe, possibly, a magnetizable material) which moves in eesponse to a current induced magnetic focce. When 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 -lq-:~L;Z3~Z~
and independent of the electrical pulse current or pulse width into the pulsing coil Z04 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, PmaX=F/A
:: where PmaX is the maximum pre5sure that can be created by the speing foece of the bellows within the medication storing means 200, F is the spring focce of bellows 202, and A is the portion o 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 sequence of rapid pulses be introduced to the pulsing coil 204, causing the plate 206 to reciprocate, the ... return 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 PmaX. The pressure builds up rapidly because of the output flow resistance caused by the ceramic filter 218. The possibility of introducing drugs or other medication at an unsafe high pressure or high rate is thus essentially eliminated.
An outlet pressure valve 21Z 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 ;iL23~2~
increasç in pressure in the storing means 200 re~:ults. When the pressure differential betwçen the pressllre in the storing means 20~ and thç pressure outlet chamber 214 exceeds that required to open outlet pres~;ure valve 212, medication flowæ
into outlet chamber 214 from the medication storing means 200.
To prevent large spurt,s or pul~;es of medication from entering the hody over a short period of time, an ela~:tic wall 216 and an output ceramic filter 21~ are provided at the entrance to the outlet 220 of outlet chamber 214. The output ceramic filter 218 serve.s to resi,st the flow of medication from the outlet chamber 214 into the living body. The elastic wall 216 acts as a type of capacitance to flow, deforming when a pulse of medication it; fed into the outlet chamber 214, the elastic wal] 216 thus serving as a fluid accumulator. The combination of thQ ela,stic wall 216 and the output ceramic filter 21 comprises; a fluid or mechanical RC network that providers medication into the body within an initial rise followçd by a decaying flow. The time constant which i.s fairly long, is determined hy the elasticity of the elastic wall 216 and the resirstance of th~3 output ceramic filtçr 218. In addition, thç
output ceramic filter 21~ disallows medication from being diffu~;ed into the body at a high rate, should both the interface pressure valve 26 and the outlet pressure valve 212 fail to seal.
lZ3~Z~
- 16 a hollld valve 212 leak, there would ye a slow diffll,sior of medicatiQn through the ceramic filter 218 until the pre~sur~
in the stor.ing mean 2 no i.5 essentially equal to ~3~Z~
ambient body pressure. However, since the volume mean 200 i6 very 6mall and since the medication fluid is essentially incompressible, vec~v little medication can difuse out and that amount only at a slow rate. Should both valve 26 and 212 leak, body fluids would then diffuse into the eeservoir 18 because it is at a pressure below body ambient pressure. A
rise in pressure in the medication reservoir 18 relative to that of the ambient body pressure would cause the -1 psig switch to be activated setting off an alarm. Further, the medication then could not difuse 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 speing force which gives a maximum pressure, Pmax, f --I 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. The resistance of the outeut ceramic filter 21B 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 ~3~;281 in either direction, from thy outlet chamber 214 into the body or fcom the body into the outlet chamber 214. Also included in the pulsatile pump 28 i8 a pee6sure transducer 2Z2 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 pres6ure transducer 222 eroduces an electrical output when a pressure pulse of medication enters the outlet chamber 214.
he peessure transducer 222, in other words, detects the pressure pulses which are peovided each time the spring bellows 202 returns the plate 206 to its ociginal posi-tion against backstop 210. By comparing the pulsing from pulsing coil 204 with the pulsing generated by pressure transducer 222, an indication is given as to whether an absence or insufficient number of pulses or medication have been provided to the body. An indication of extra pulses of medication compared to I: the number of electrical pulses may also be provided.
The pulsing signal to pulsing coil 204 as well as the eulse output from the pressure transducer 222 are better understood with reference to FIG. 5 a block diagram of the electronics section 30 shown in FIGS. 2 and 3. As seen in FIG. 5, the electronics section 30 communicates with a communication head 300 which is external to the body, communicating through skin S by means of radio signals which includes an alternating magnetic field. The communications head 300 provides both power inputs and commands, including programmable inputs, to the electronics section 30. Power is 23~
provided by means of an alternat,ing field, e.g., a magnetic Eield, which I comml.lnicated I:o a pickup coil 304 s7hich it;
implant,ed together wit,h the ret of the electronic ection 30 in the body. The pickup coil 304 regive an AC power ~3ignal from communication; hçad 300 and pees it on to a ull wave rectifier 306. One rectified output from the full wave rectifier 306 enter; a batter charge cont,rol ~08 which provides;
a fixed DC charging signal to a power cell 310. The power cell 310 can be a nickel-cadmium cell which is readily rechargeahle off a rectified ~;ignal at a typiGal frequency of 20 kHz.
Alternat,ively, a lithium-type .~olid state l~attery can be u:~;ed in~3tead of the nickel-cadmium cell, in which case the charging circuitry would be eliminated, the lithium-type battery providing :~ufficient power over a long te3rm, therehy obviating the need for recharging. The power cell 310 provide.s a bia~;ing voltage to a tran~ tor switch 312, the output of which enter:
the pulsing coil 204 previously described in the context of the pul~;atile pump 28. In addition to providing power to the powçr cell 310, rectified power it al.~o introduced to a DC to AC
converter 314 the purpose of which it; to provide power at the proper level to the various load in the :~ys~;tem. In addition to the A. power signal, pickup coil 304 alto receive a train of ~:erial digital lit from the communication head 3Qn. The digital bit comprise command for programmak-le input: which are conveyed, via the pickuE~ coil 304 to a command receiver 316. The ~:ignal~ from the command receiver 316 enter ~L~3~LZ~3~
a command decoder l whlch dçtçrmines if the digital bit arQ
in a proper sç~uen~e and, if Jo, what action in the systçm thç
command.s dictate. It should bç noted that the full wave rectifier 30~, the buttery chargç controller 308, the command receiver 316, and the command decoder 31t3 are powçred only when an A signal is pickçd up hy the pickup coil 304. This, of course, prevents the possibility of detecting stray signals a commands and provides power savings. To be sure, the pnwer .saving.s achieved could make possible the use of thç
aforementioned lithium cell which would not require recharging.
From the command decoder 31~, programmable inputs and othçr commands can bç prQvided to a number of elements. A
programmable base rate iæ entçred into a basç rate memory unit 320 which storçs a value indicating thç number of pulses of medication which are requested to be provided to a patient during a normal preselectçd pçriod of time. A second programmable input is provided, namçly a patient-controlled ratç mçmory unit 322 which stores a value indicating a number of pulses of medication that are requested to be introduced into the body over a given period of time during which the patient çatrs a meal or otherwise alters the chemical balance of the body (as by e.~ercising). Associated with the base rate memory unit 320 is a hardwired base ratç limit control 324 which jets a maximum rate that can override requests of the base rate memory unit 320 which are exce~ive. similarly, a hardwired patient controlled rate limit control 326 provides a ~L~3~'~8~
fixed maximum number of pul.ses which Jan by provided at, a time after a meal or at other times and unrler other conditions. As lQng AS the base rat,e and the patient,-controlled rate values stored in memory unit 320 and 322 respectively, do not exceed the hardwirQd values fixQd within limi-t controls 324 and 326, re~spectivQly, an out,put pulse is provided to the input of transistor switch 312 to stimulAte Q pulsQ output from pul.sing coil 204. Should the rate of either memory unit 320 or 322 exceed the hardwired limits in the limit cont,rol elQmQnts 324 or 32~ respectivQly, a "rate request exeeds limit" signal is fed from the limit, control elemQnt 324 or 32h into a programmable alarm generator 32~ which providçs an electricil signal to the stimulation electrode 330 implanted rsubcutaneQIlsly. my means of the stimulation electrQde 330, the patiQnt is inormed, by meanrs of subcutaneous .stimulation, that one of the memory unit-s 32Q or 322 is re~uersting more -than the maximum all ow able number of pulse.s.
It should be noted that thç signal to the stimulation electrode 330 can serve the dual function not only of providing the patient with a subcutaneous eleGtrical rstimulation, but also may be the .source of a signal detected by the communication head 300 communicated either to the patient or to his physician or hoth, that, a failure has occurred. As shown in FIG. 5, the electrode 330 will ke isolated and should be insulated from the outside o-E the hermetically-sealQd enclosure 34 of the implanted portion 2.
~23~
A particularly significant featllre of the inl1~ion system emkracing aspectæ of the present invention re,sides in the programmabilit.y of t.he alarm generator 32~ based on inpl1t command from the Gommand decoder 31~. The alarm generator 328 can bQ swit.ched on or off and the voltage produced by thç
generator, and henGe to the elçGtrode 330, can be varied in response to signal emanating from the communication hçad 300 and channeled through the command reGsiver 31Ç to the Gommand decoder 31~. In addition, to Gheck the proper operation of the system, the command decoder 31~ can receive test .signals whish can simulate actual occurrences to detçrmine whether the Gir~uitry in the eleGtroniG section 30 is operating properly.
For example, extra pul.~es from the command decoder 31~3 Gan bç
enterçd into the hardwired limit control elements 324 and 32Ç.
These extra pulses can ye added to the pulse pro~idçd by the bate rate and the patient-controlled rate memory units in order to ex~eçd the hardwirçd base rate and the hardwired patient-controlled rate, respectivçly. When the rates are e~ceQded, the alarm generator 323 will providç a signal. In this way, the alarm generator 32~3 can be used to check the operation of thç limit Gontrol elements 324 and 32Ç and also to familiarize the patient with the corresponding subcutaneolls signals emittçd by the tickle elect.rode 330. The programmable alarm gçnerator 328 also receiYes inputs from the pressure switch 22 and the fluid detector 35, both shown in FIX. 2. If body fluids leak ~Z3~
- ~2~ -into the reservoir l the prQ~sl~re with 2.5 wi]l be activated, indicating this fault condition to the patient by means of the activati,on of -the a].arm generator 32~ and t,he electrode 3~0. If thy patient was llncon~ciol.ls, voltage levels of the p~tlent'~ skin at the site of the implanted portion 2 1231'~
could be used by the phsyician to indicate if a malfunction has occurred and which malfunction it was. Further, as previously described, should fluid leak out of the reservoir chamber 10 and onto the lining of the enclosure 34 or, alternatively, if body fluid should leak in through the enclosure 34, the fluid detector 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 genecator 320 comes from the power cell 310 associated with transistor switch 312. The voltage level of the vower 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, referring 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 decode 318. If the number of pulses sensed by the pressure transducer 222 over a specified period of time are less than the number of eulses associated with the "insufficient rate" command input, a pulse rate detector 332 will provide an output indicating that an insufficient amount of medication is being provided to the patient over the specified time. The output of pulse rate detector 332 (FIG.
5) also enters the tickle generator 328 to provide a subcutaneous tickle detectable by the patient. It should be noted that the various mentioned failures in the system result in subcutaneous stimulations each of which may be different in stimulation magnitude, duration, or periodicity. For example, ~23~2~
the stimulation may range between one to four vo]ts and may very in frequency abovç and below 20 pulses per second and mo.~t importantly, a. variety oE pulse patterns may be used each uni.que to a particular malfunct.iQn or warning. Additional warnings that m.ight be used are: (1) meditation has leaked into the liquid-vapQr volume; (2) only 1Q% of the medication remain.c in the reservoir; and (.3) onl.y 5 days medisation remains.
In addition to pulsing the pump toil 204, the outputs of the ].imit çontrol elements 324 and 326 al.so provide input to a pulse recorder 334. Pulse recorder 334 maintains a running history of how many ele~tri~al pulsss have been prov.ided to the pulsatile pump 28 singe the last refill of thç reservoir 18 (in FIX. 1). An "interrogate" signal from the command decoder 318 instructs the pulse reorder 334 to provide the history to a telemetry transmitter 336 which communicates the pulse history to a telemçtry coil 33~3. The pulse recorder 334 would record both t.he number of pulsçs delivered to the pumping coil 204 and the number of puts detected by the pressure transducer 222 and/or the difference between these two numbers. The telemetry coil 33~3, in turn, providçs its output thrQugh radio frequency signals to a telemetry-receiving antenna in the communication head 300. In addition to the pulse history, the telçmetry transmitter 336 also rç~eives, during programming, inputs from the base rate memory unit 320 and patient-~ontrolled rate memory unit 322 which are transmitted hack to the communication head 30Q indicating that the desired base rate and patient contro].led rate, respectively, have been programmed ~L~3~
in the corresponding memory unit 32 or 322. Similarly, other key parameterc 337 of the system are alGo conveyed by means of the telemetry tcansmitter 336 back to the communication head 300. For example, the exact pcessure transducer output wavefoLm would be telemetered. Of course, the pressure wavefoem 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 feom 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 signals, and power cell charging.
Reference is now made to FIG. 6 which shows a method of programming the patient controlled memory untit 322. The significance o 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 thecefore would be effective regardless of the patients eating or working schedule, which 3L~23~
schedule change might be a cesult of the patient changing time zones. In the sample gcaph 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. These rate settings can, of course, be altered depending on eatient needs and medication to be administered and time periods other than four hours or 24 hours could be used. In FIG. 6, the number of pulses i6 shown as function of time.
In Fig. 6, at midnight, the number of pulses that are allowed in the four hour period is eight. Shortly-after 8 A.M. five pulses are requested diminishing the number of additional pulses allowed to three pulses. Prior to noon, within the four hour time peeiod, a five pulse request is entered. In accordance with the maximum running integral four hour restraint, only three pulses are permitted but the remaining two pulses in the request are stored in the memory unit 322 (FIG. S) 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, OL shortly before 4 P.M. Shortly before 4 P.M. the three pulse allowance is automatically raised to six pulses, accounting for the three ~3~
pulses executed just befoce noon. Shortly after 4 P.M., thy allowance automatically rises to eight pulses theceby 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 before 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 York schedules a patient may go theough 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.
Referring now to FIG. 7, the front view of a patient . .
programming unit 400 is shown. In the center of the unit is a dial 402 which can be rotated to indicate,the size of a meal eaten by the patient or the amount of exercise he had undergone, in order to provide inputs indicating the amount of medicàtion needed. Output from the patient programming unit 400 is detected by the pickup coil 304 of FIG. 5 as commands.
Whether or not the request is valid is determined in the electronic section 30 and is conveyed back to the patient programming unit 400 by telemetry. signal by the patient programming unit 400 to the patient indicates whether his request has been satisfied. The patient programming unit 400 ~23~
will be provided both with audio and visual outputs rendering it particularly useful for those patients having either visual or hearing handicaps.
In FIG. 8 is the rear view of the patient programming unit 400. The rear side of the patient programming unit 400 will provide inormation 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 pcogramming ROMS (not shown) in the patient programming unit 400 in accordance with the running integral programs shown in FIG. 5 an "OK" or "TOO
MUCH REQUESTED" video and/or audible output can be provided.
The audio output would emanate from the loudspeaker 405. When the request leads to the dispensing of a pulse or pulses of medication into the outlet chambert, a "MEDICATION SENT" signal from the implanted portion 2 is relayed to the patient programming unit 400 to actuate an audio indication by loudspeaker 405 or by visual means.
It should be understood that alternative embodiments ' 20 are contemplated for the infusion system embcacing the eresent invention. For example, the antechamber 8 can comprise a vitreous carbon insert in the skull, or other suitable, accessible elace on the body, coueled with a tube directed to the reservoir chamber lO which may be located in the torso.
The filling procedure and elements o antechamber 8 (e.g., the septum 6) would remain the same with the vitreous carbon insert. The inlet pressure valve 14 and filter 12 would 6till ~231~
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 lB (of FIG. 1) has been filled, the pulse history 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.
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS
1. A programmable infusion system for providing medication to a living body including an infusion apparatus having infusion means for infusing a selected medication stored in a medication reservoir into a living body, said infusion means having a commandable infusion rate which is variable upon command, said infusion apparatus comprising: inhibiting means for inhibiting said infusion means from infusing said selected medication if a preselected medication infusion rate is exceeded.
2. A system according to Claim 1, wherein said inhibiting means includes at least one means for defining a fixed infusion rate limit.
3. A system according to Claims 1 or 2, wherein said preselected medication infusion rate is remotely selectable.
4. A system according to Claims 1 or 2, wherein said preselected medication infusion rate comprises a remotely selectable rate and a fixed rate, said remotely selectable rate being limited to said fixed rate.
5. A system according to Claims 1 or 2, wherein said inhibiting, means comprises at least one programmable rate memory unit, each of said at least one programmable rate memory units for receiving and storing an infusion rate input command corresponding to said remotely selectable rate; at least one limit control unit, each of said at least one limit control units providing a fixed rate limit; and means for comparing each of said infusion rate input commands to a corresponding said fixed rate limit, infusion of said medication at a rate exceeding said fixed rate limit being inhibited.
6. A system according to Claims 1 or 2 wherein said inhibiting means includes time dependent means for precluding infusion of said medication by said infusion means when the selected said commandable infusion rate exceeds said preselected medication infusion rate during a window of time of a predetermined length which shifts continuously.
7. A system according to Claim 1, wherein said infusion means includes a pump means which executes in pulses, and said inhibiting means comprises a programmable memory rate unit for storing initially a dose limit number corresponding to a first maximum number of infusion pulses preselected as allowable during a first shifting time window of a predetermined length, pulse quantities being subtractedfrom said number stored in said programmable memory rate unit as infusion pulses are executed by said infusion means, pulse quantities being added to said stored number as time elapses such that said number does not exceed said first maximum number, said subtraction and addition being accomplished in running integral fashion, and said inhbiting means not permitting pulsing of said pump means at a rate in excess of the rate represented by said dose limit number stored in said programmable memory rate unit.
8. A system according to Claim 7, wherein said memory rate unit also records the number of pulses which have been inhibited and causes said pump means of said infusion means to execute said pulses when said pulses can be subtracted as a result of the elapse of time from said dose limit number stored in said programmable memory rate unit.
9. A system according to Claim 8, wherein said programmable memory rate unit also stores initially another dose limit number corresponding to a second maximum number of infusion pulses preselected as allowable during a second shifting time window of a predetermined length, said second shifting time window being longer in length than said first shifting time window, pulse quantities being subtracted from said another dose limit number stored in said programmable memory rate unit as infusion pulses are executed by said infusion means, pulse quantities being added to said another dose limit number as time elapses such that said another dose limit number does not exceed said first maximum number, said subtraction and addition being accomplished in running integral fashion, and said inhibiting means not permitting pulsing of said pump means at a rate in excess of the rate represented by said another dose limit number stored in said programmable memory rate unit.
10. A system according to Claim 9, wherein said programmable memory unit also records the number of pulses which have been inhibited and causes said pump means of said infusion means to execute said pulses when said pulses can be subtracted from both said dose limit numbers stored in said programmable memory rate unit.
11. A system according to Claim 10, wherein said inhbiting means further comprises at least one fixed infusion rate limit which limits the total maximum infusion rate of said infusion means.
12. A system according to Claims 1 or 2, further comprising means for recording when said inhibiting means inhibits said infusion means.
13. A system according to Claims 1 or 2, further comprising means for generating an alarm signal when any commanded infusion rate results in the inhibiting of pulsing of said pump means by said inhibiting means.
14. A system according to Claims 1 or 2, wherein said infusion apparatus is adapted for implantation in said living body.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000486976A CA1231281A (en) | 1982-12-17 | 1985-07-17 | Inhibiting means for programmable infusion system |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000417979A CA1193934A (en) | 1982-12-17 | 1982-12-17 | Implantable programmable medication infusion system |
| CA000486976A CA1231281A (en) | 1982-12-17 | 1985-07-17 | Inhibiting means for programmable infusion system |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000417979A Division CA1193934A (en) | 1982-12-17 | 1982-12-17 | Implantable programmable medication infusion system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1231281A true CA1231281A (en) | 1988-01-12 |
Family
ID=4124170
Family Applications (4)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000417979A Expired CA1193934A (en) | 1982-12-17 | 1982-12-17 | Implantable programmable medication infusion system |
| CA000486976A Expired CA1231281A (en) | 1982-12-17 | 1985-07-17 | Inhibiting means for programmable infusion system |
| CA000486993A Expired CA1231282A (en) | 1982-12-17 | 1985-07-17 | Pumping means for programmable infusion system |
| CA000486992A Expired CA1206832A (en) | 1982-12-17 | 1985-07-17 | Alarm means for programmable infusion system |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000417979A Expired CA1193934A (en) | 1982-12-17 | 1982-12-17 | Implantable programmable medication infusion system |
Family Applications After (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000486993A Expired CA1231282A (en) | 1982-12-17 | 1985-07-17 | Pumping means for programmable infusion system |
| CA000486992A Expired CA1206832A (en) | 1982-12-17 | 1985-07-17 | Alarm means for programmable infusion system |
Country Status (1)
| Country | Link |
|---|---|
| CA (4) | CA1193934A (en) |
-
1982
- 1982-12-17 CA CA000417979A patent/CA1193934A/en not_active Expired
-
1985
- 1985-07-17 CA CA000486976A patent/CA1231281A/en not_active Expired
- 1985-07-17 CA CA000486993A patent/CA1231282A/en not_active Expired
- 1985-07-17 CA CA000486992A patent/CA1206832A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| CA1231282A (en) | 1988-01-12 |
| CA1206832A (en) | 1986-07-02 |
| CA1193934A (en) | 1985-09-24 |
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