U.S. patent application number 12/444011 was filed with the patent office on 2010-03-04 for drug heating cycle limiter for injection device.
Invention is credited to Cesario Dos Santos.
Application Number | 20100057003 12/444011 |
Document ID | / |
Family ID | 39721777 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100057003 |
Kind Code |
A1 |
Dos Santos; Cesario |
March 4, 2010 |
Drug Heating Cycle Limiter For Injection Device
Abstract
An injection assembly includes a dispensing chamber housing, a
temperature control device, a thermal sensor, a switch, and a
controller. The dispensing chamber housing has an inner surface and
an outer surface. The inner surface partially defines a dispensing
chamber for receiving a quantity of a substance. The temperature
control device at least partially surrounds the dispensing chamber
housing and alters a temperature of a substance in the dispensing
chamber. The thermal sensor is located near the temperature control
device and reads a temperature near the temperature control device.
The switch is coupled to the temperature control device. The
controller controls the temperature control device and the switch
such that a first voltage is applied to the temperature control
device until the temperature control device reaches a desired
temperature, and a second voltage is applied to the temperature
control device thereafter to maintain the temperature control
device at the desired temperature.
Inventors: |
Dos Santos; Cesario; (Aliso
Viejo, CA) |
Correspondence
Address: |
ALCON
IP LEGAL, TB4-8, 6201 SOUTH FREEWAY
FORT WORTH
TX
76134
US
|
Family ID: |
39721777 |
Appl. No.: |
12/444011 |
Filed: |
October 9, 2007 |
PCT Filed: |
October 9, 2007 |
PCT NO: |
PCT/US07/80755 |
371 Date: |
April 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60921498 |
Oct 16, 2006 |
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60921499 |
Oct 16, 2006 |
|
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60921497 |
Oct 16, 2006 |
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Current U.S.
Class: |
604/114 ; 222/1;
222/54 |
Current CPC
Class: |
A61M 2005/14268
20130101; A61M 5/20 20130101; A61M 2205/50 20130101; A61M 2205/6027
20130101; A61M 5/1413 20130101; A61M 5/445 20130101; A61M 5/14244
20130101; A61M 2205/3653 20130101; A61M 2205/3368 20130101; A61M
5/14526 20130101; A61M 5/31511 20130101; A61M 2210/0612 20130101;
A61M 5/3129 20130101; A61M 5/14546 20130101; A61M 5/14566 20130101;
A61M 2205/8206 20130101; A61F 9/0017 20130101 |
Class at
Publication: |
604/114 ; 222/54;
222/1 |
International
Class: |
A61M 5/44 20060101
A61M005/44; B67D 7/82 20100101 B67D007/82; A61F 7/12 20060101
A61F007/12 |
Claims
1. A dispensing assembly comprising: a dispensing chamber housing
having an inner surface and an outer surface, the inner surface
partially defining a dispensing chamber for receiving a quantity of
a substance; a temperature control device at least partially
surrounding the dispensing chamber housing, the temperature control
device for altering a temperature of a substance in the dispensing
chamber; a thermal sensor located near the temperature control
device, the thermal sensor for reading a temperature near the
temperature control device; and a controller for controlling the
temperature control device such that the substance in the
dispensing chamber is not exposed to elevated temperature nor
overexposed to heat.
2. The assembly of claim 1 wherein the controller counts a number
of times the temperature control device is activated.
3. The assembly of claim 2 wherein the controller disables a tip
segment if the number of times the temperature control device is
activated exceeds a set number.
4. The assembly of claim 1 wherein the controller times a period
when the temperature control device is activated.
5. The assembly of claim 4 wherein the controller shuts off the
temperature control device when the period when the temperature
control device is activated exceeds a set period.
6. The assembly of claim 1 further comprising: a switch coupled to
the temperature control device.
7. The assembly of claim 6 wherein the controller controls the
switch such that a first voltage is applied to the temperature
control device until the temperature control device reaches a
desired temperature, and a second voltage is applied to the
temperature control device thereafter to maintain the temperature
control device at the desired temperature.
8. The assembly of claim 1 wherein the temperature control device
is a heater comprising a resistive element.
9. An injection assembly comprising: a dispensing chamber housing
having an inner surface and an outer surface, the inner surface
partially defining a dispensing chamber for receiving a quantity of
a substance; a temperature control device at least partially
surrounding the dispensing chamber housing, the temperature control
device for altering a temperature of a substance in the dispensing
chamber; a thermal sensor located near the temperature control
device, the thermal sensor for reading a temperature near the
temperature control device; a switch coupled to the temperature
control device; and a controller for controlling the temperature
control device; wherein the controller controls the switch such
that a first voltage is applied to the temperature control device
until the temperature control device reaches a desired temperature,
and a second voltage is applied to the temperature control device
thereafter to maintain the temperature control device at the
desired temperature.
10. The assembly of claim 9 wherein the controller counts a number
of times the temperature control device is activated.
11. The assembly of claim 10 wherein the controller disables a tip
segment if the number of times the temperature control device is
activated exceeds a set number.
12. The assembly of claim 9 wherein the controller times a period
when the temperature control device is activated.
13. The assembly of claim 12 wherein the controller shuts off the
temperature control device when the period when the temperature
control device is activated exceeds a set period.
14. The assembly of claim 9 wherein the temperature control device
is a heater comprising a resistive element.
15. A method of operating a dispensing assembly comprising:
checking a count of a number of times a temperature control device
has been activated; if the count does not exceed a preset number,
incrementing a counter; applying a first voltage across a
temperature control device to bring the temperature control device
to a desired temperature; after the temperature control device
reaches the desired temperature, applying a second voltage across
the temperature control device to maintain the temperature control
device at the desired temperature; starting a timer to count the
amount of time that the temperature control device is activated;
and if the amount of time that the temperature control device is
activated exceeds a preset amount of time, turning off the
temperature control device.
16. The method of claim 15 further comprising: if the count exceeds
a preset number, then disabling a tip segment so that an injection
cannot be performed.
17. The method of claim 15 wherein applying a first voltage across
a temperature control device to bring the temperature control
device to a desired temperature further comprises controlling a
switch to apply the first voltage.
18. The method of claim 17 wherein applying a second voltage across
a temperature control device to bring the temperature control
device to a desired temperature further comprises controlling a
switch to apply the second voltage.
19. The method of claim 18 wherein starting a timer to count the
amount of time that the temperature control device is activated
further comprises starting the timer when the switch is controlled
to apply the second voltage.
20. The method of claim 15 wherein starting a timer to count the
amount of time that the temperature control device is activated
further comprises starting the timer after the temperature control
device has reached the desired temperature.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/581,629 filed Oct. 16, 2006, U.S. patent
application Ser. No. 11/581,630 filed Oct. 16, 2006, U.S. patent
application Ser. No. 11/581,591 filed Oct. 16, 2006, and is related
to U.S. patent application Ser. No. 11/435,906 filed May 17,
2006.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a single-use medical device
and more particularly to a two-piece ophthalmic injection device
with a disposable tip end containing a temperature control device
and temperature sensor assembly.
[0003] Several diseases and conditions of the posterior segment of
the eye threaten vision. Age related macular degeneration (ARMD),
choroidal neovascularization (CNV), retinopathies (e.g., diabetic
retinopathy, vitreoretinopathy), retinitis (e.g., cytomegalovirus
(CMV) retinitis), uveitis, macular edema, glaucoma, and
neuropathies are several examples.
[0004] These, and other diseases, can be treated by injecting a
drug into the eye. Such injections are typically done manually
using a conventional syringe and needle. FIG. 1 is a perspective
view of a prior art syringe used to inject drugs into the eye. In
FIG. 1, the syringe includes a needle 105, a luer hub 110, a
chamber 115, a plunger 120, a plunger shaft 125, and a thumb rest
130. As is commonly known, the drug to be injected is located in
chamber 115. Pushing on the thumb rest 130 causes the plunger 120
to expel the drug through needle 105.
[0005] In using such a syringe, the surgeon is required to pierce
the eye tissue with the needle, hold the syringe steady, and
actuate the syringe plunger (with or without the help of a nurse)
to inject the fluid into the eye. The volume injected is typically
not controlled in an accurate manner because reading the vernier is
subject to parallax error. Fluid flow rates are uncontrolled and
tissue damage may occur due to an "unsteady" injection. Reflux of
the drug may also occur when the needle is removed from the
eye.
[0006] An effort has been made to control the delivery of small
amounts of liquids. A commercially available fluid dispenser is the
ULTRA.TM. positive displacement dispenser available from EFD Inc.
of Providence, R.I. The ULTRA dispenser is typically used in the
dispensing of small volumes of industrial adhesives. It utilizes a
conventional syringe and a custom dispensing tip. The syringe
plunger is actuated using an electrical stepper motor and an
actuating fluid. Parker Hannifin Corporation of Cleveland, Ohio
distributes a small volume liquid dispenser for drug discovery
applications made by Aurora Instruments LLC of San Diego, Calif.
The Parker/Aurora dispenser utilizes a piezo-electric dispensing
mechanism. Ypsomed, Inc. of Switzerland produces a line of
injection pens and automated injectors primarily for the
self-injection of insulin or hormones by a patient. This product
line includes simple disposable pens and electronically-controlled
motorized injectors.
[0007] U.S. Pat. No. 6,290,690 discloses an ophthalmic system for
injecting a viscous fluid (e.g. silicone oil) into the eye while
simultaneously aspirating a second viscous fluid (e.g.
perflourocarbon liquid) from the eye in a fluid/fluid exchange
during surgery to repair a retinal detachment or tear. The system
includes a conventional syringe with a plunger. One end of the
syringe is fluidly coupled to a source of pneumatic pressure that
provides a constant pneumatic pressure to actuate the plunger. The
other end of the syringe is fluidly coupled to an infusion cannula
via tubing to deliver the viscous fluid to be injected.
[0008] It would be desirable to have a portable hand piece for
injecting a drug into the eye. Such a hand piece can include a
limited reuse assembly attachable to and removable from a
disposable tip segment. The disposable tip segment contains the
drug, a needle for administering the drug, and a temperature
control device, such as a heater, for altering the temperature of
the drug. Typically, the drug is suspended in a compound that is
heated. In order to maintain the integrity of the drug, it is
desirable to limit the number of times it is heated. Therefore, it
would be desirable to implement a drug delivery hand piece with
such a heating limitation.
SUMMARY OF THE INVENTION
[0009] In one embodiment consistent with the principles of the
present invention, the present invention is a dispensing assembly
including a dispensing chamber housing, a temperature control
device, a thermal sensor, and a controller. The dispensing chamber
housing has an inner surface and an outer surface. The inner
surface partially defines a dispensing chamber for receiving a
quantity of a substance. The temperature control device at least
partially surrounds the dispensing chamber housing and alters a
temperature of a substance in the dispensing chamber. The thermal
sensor is located near the temperature control device and reads a
temperature near the temperature control device. The controller
controls the temperature control device such that the substance in
the dispensing chamber is not exposed to temperature stress.
[0010] In another embodiment consistent with the principles of the
present invention, the present invention is an injection assembly
including a dispensing chamber housing, a temperature control
device, a thermal sensor, a switch, and a controller. The
dispensing chamber housing has an inner surface and an outer
surface. The inner surface partially defines a dispensing chamber
for receiving a quantity of a substance. The temperature control
device at least partially surrounds the dispensing chamber housing
and alters a temperature of a substance in the dispensing chamber.
The thermal sensor is located near the temperature control device
and reads a temperature near the temperature control device. The
switch is coupled to the temperature control device. The controller
controls the temperature control device. The controller controls
the switch such that a first voltage is applied to the temperature
control device until the temperature control device reaches a
desired temperature, and a second voltage is applied to the
temperature control device thereafter to maintain the temperature
control device at the desired temperature.
[0011] In another embodiment consistent with the principles of the
present invention, the present invention is a method of operating a
dispensing assembly including checking a count of a number of times
a temperature control device has been activated; if the count does
not exceed a preset number, incrementing a counter; applying a
first voltage across a temperature control device to bring the
temperature control device to a desired temperature; after the
temperature control device reaches the desired temperature,
applying a second voltage across the temperature control device to
maintain the temperature control device at the desired temperature;
then starting a timer to count the amount of time that the
temperature control device is activated; and if the amount of time
that the temperature control device is activated exceeds a preset
amount of time, the temperature control device is turned off.
[0012] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are intended to provide further
explanation of the invention as claimed. The following description,
as well as the practice of the invention, set forth and suggest
additional advantages and purposes of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The accompanying figures, which are incorporated in and
constitute a part of this specification, illustrate several
embodiments of the invention and together with the description,
serve to explain the principles of the invention.
[0014] FIG. 1 is a perspective view of a prior art syringe.
[0015] FIG. 2 is a view of an ophthalmic medical device including a
disposable tip segment and a limited reuse assembly according to
the principles of the present invention.
[0016] FIG. 3 is an embodiment of a limited reuse assembly
according to the principles of the present invention.
[0017] FIG. 4 is a cross section view of a disposable tip segment
and a limited reuse assembly according to the principles of the
present invention.
[0018] FIG. 5 is a cross section view of a disposable tip segment
according to the principles of the present invention.
[0019] FIG. 6 is a block diagram of an implementation of a drug
heating cycle limiter according to the principles of the present
invention.
[0020] FIG. 7 is a block diagram of an implementation of a drug
heating cycle limiter according to the principles of the present
invention.
[0021] FIG. 8 is a graph of one operation of a drug heating cycle
limiter according to the principles of the present invention
[0022] FIG. 9 is a flow chart of a method of operating a drug
heating cycle limiter according to the principles of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Reference is now made in detail to the exemplary embodiments
of the invention, examples of which are illustrated in the
accompanying figures. Wherever possible, the same reference numbers
are used throughout the figures to refer to the same or like
parts.
[0024] FIG. 2 depicts one view of an ophthalmic medical device
including a disposable tip segment and a limited reuse assembly
according to an embodiment of the present invention. In FIG. 2, the
medical device includes a tip segment 205 and a limited reuse
assembly 250. The tip segment 205 includes a needle 210, a housing
215, and an optional light 275. The limited reuse assembly 250
includes a housing 255, a switch 270, a lock mechanism 265, and a
threaded portion 260.
[0025] Tip segment 205 is capable of being connected to and removed
from limited reuse assembly 250. In this embodiment, tip segment
205 has a threaded portion on an interior surface of housing 215
that screws onto the threaded portion 260 of limited reuse assembly
250. In addition, lock mechanism 265 secures tip segment 215 to
limited reuse assembly 250. Lock mechanism 265 may be in the form
of a button, a sliding switch, or a cantilevered mechanism. Other
mechanisms for connecting tip segment 205 to limited reuse assembly
250, such as those involving structural features that mate with
each other, are commonly known in the art and are within the scope
of the present invention.
[0026] Needle 210 is adapted to deliver a substance, such as a
drug, into an eye. Needle 210 may be of any commonly known
configuration. Preferably, needle 210 is designed such that its
thermal characteristics are conducive to the particular drug
delivery application. For example, when a heated drug is to be
delivered, needle 210 may be relatively short (several millimeters)
in length to facilitate proper delivery of the drug based on
thermal characteristics.
[0027] Switch 270 is adapted to provide an input to the system. For
example, switch 270 may be used to activate the system or to turn
on a heater. Other switches, buttons, or user-directed control
inputs are commonly known and may be employed with limited reuse
assembly 250 and/or tip segment 205.
[0028] Optional light 275 is illuminated when tip segment 205 is
ready to be used. Optional light 275 may protrude from housing 215,
or it may be contained within housing 215, in which case, optional
light 275 may be seen through a clear portion of housing 215. In
other embodiments, optional light 275 may be replaced by an
indicator, such as a liquid crystal display, segmented display, or
other device that indicates a status or condition of disposable tip
segment 205. For example, optional light 275 may also pulse on and
off to indicate other states, such as, but not limited to a system
error, fully charged battery, insufficiently charged battery or
faulty connection between the tip segment 205 and limited use
assembly 250. While shown on tip segment 205, optional light 275 or
other indicator may be located on limited reuse assembly 250.
[0029] FIG. 3 is another embodiment of a limited reuse assembly
according to the principles of the present invention. Limited reuse
assembly 250 includes a button 310, a display 320, and a housing
330. Disposable tip segment 205 attaches to end 340 of limited
reuse assembly 250. Button 310 is actuated to provide an input to
the system. As with switch 270, button 310 may activate a heater or
other temperature control device or initiate actuation of a
plunger. Display 320 is a liquid crystal display, segmented
display, or other device that indicates a status or condition of
disposable tip segment 205 or limited reuse assembly 250.
[0030] FIG. 4 is a cross section view of a disposable tip segment
and a limited reuse assembly according to an embodiment of the
present invention. FIG. 4 shows how tip segment 205 interfaces with
limited reuse assembly 250. In the embodiment of FIG. 4, tip
segment 205 includes plunger interface 420, plunger 415, dispensing
chamber housing 425, tip segment housing 215, temperature control
device 450, thermal sensor 460, needle 210, dispensing chamber 405,
interface 530, and tip interface connector 520. Limited reuse
assembly 250 includes mechanical linkage 545, actuator shaft 510,
actuator 515, power source 505, controller 305, limited reuse
assembly housing 255, interface 535, and limited reuse assembly
interface connector 525.
[0031] In tip segment 205, plunger interface 420 is located on one
end of plunger 415. The other end of plunger 415 forms one end of
dispensing chamber 405. Plunger 415 is adapted to slide within
dispensing chamber 405. An outer surface of plunger 415 is fluidly
sealed to the inner surface of dispensing chamber housing 425.
Dispensing chamber housing 425 surrounds the dispensing chamber
405. Typically, dispensing chamber housing 425 has a cylindrical
shape. As such, dispensing chamber 405 also has a cylindrical
shape.
[0032] Needle 210 is fluidly coupled to dispensing chamber 405. In
such a case, a substance contained in dispensing chamber 405 can
pass through needle 210 and into an eye. Temperature control device
450 at least partially surrounds dispensing chamber housing 425. In
this case, temperature control device 450 is adapted to heat and/or
cool dispensing chamber housing 425 and any substance contained in
dispensing chamber 405. Interface 530 connects temperature control
device 450 and thermal sensor 460 with tip interface connector
520.
[0033] The components of tip segment 205, including dispensing
chamber housing 425, temperature control device 450, and plunger
415 are at least partially enclosed by tip segment housing 215. In
one embodiment consistent with the principles of the present
invention, plunger 415 is sealed to the interior surface of
dispensing chamber housing 425. This seal prevents contamination of
any substance contained in dispensing chamber 405. For medical
purposes, such a seal is desirable. This seal can be located at any
point on plunger 415 or dispensing chamber housing 425.
[0034] In limited reuse assembly 250, power source 505 provides
power to actuator 515. An interface (not shown) between power
source 505 and actuator 515 serves as a conduit for providing power
to actuator 515. Actuator 515 is connected to actuator shaft 510.
When actuator 515 is a stepper motor, actuator shaft 510 is
integral with actuator 515. Mechanical linkage interface 545 is
connected to actuator shaft 510. In this configuration, as actuator
515 moves actuator shaft 510 upward toward needle 210 mechanical
linkage interface 545 also moves upward toward needle 210.
[0035] Controller 305 is connected via interface 535 to limited
reuse assembly interface connecter 525. Limited reuse assembly
interface connecter 525 is located on a top surface of limited
reuse assembly housing 255 adjacent to mechanical linkage interface
545. In this manner, both limited reuse assembly interface
connector 525 and mechanical linkage interface 545 are adapted to
be connected with tip interface connector 520 and plunger interface
420 respectively.
[0036] Controller 305 and actuator 515 are connected by an
interface (not shown). This interface (not shown) allows controller
305 to control the operation of actuator 515. In addition, an
interface (not shown) between power source 505 and controller 305
allows controller 305 to control operation of power source 505. In
such a case, controller 305 may control the charging and the
discharging of power source 505 when power source 505 is a
rechargeable battery.
[0037] Controller 305 is typically an integrated circuit with
power, input, and output pins capable of performing logic
functions. In various embodiments, controller 305 is a targeted
device controller. In such a case, controller 305 performs specific
control functions targeted to a specific device or component, such
as a temperature control device or a power supply. For example, a
temperature control device controller has the basic functionality
to control a temperature control device. In other embodiments,
controller 305 is a microprocessor. In such a case, controller 305
is programmable so that it can function to control more than one
component of the device. In other cases, controller 305 is not a
programmable microprocessor, but instead is a special purpose
controller configured to control different components that perform
different functions. While depicted as one component, controller
305 may be made of many different components or integrated
circuits.
[0038] Tip segment 205 is adapted to mate with or attach to limited
reuse assembly 250 as previously described. In the embodiment of
FIG. 5, plunger interface 420 located on a bottom surface of
plunger 415 is adapted to mate with mechanical linkage interface
545 located near a top surface of limited reuse assembly housing
255. In addition, tip interface connector 520 is adapted to connect
with limited reuse assembly interface connector 525. When tip
segment 205 is connected to limited reuse assembly 250 in this
manner, actuator 515 and actuator shaft 510 are adapted to drive
plunger 415 upward toward needle 210. In addition, an interface is
formed between controller 305 and temperature control device 450. A
signal can pass from controller 305 to temperature control device
450 through interface 535, limited reuse assembly interface
connector 525, tip interface connector 520, and interface 530.
[0039] In operation, when tip segment 205 is connected to limited
reuse assembly 250, controller 305 controls the operation of
actuator 515. Actuator 515 is actuated and actuator shaft 510 is
moved upward toward needle 210. In turn, mechanical linkage
interface 545, which is mated with plunger interface 420, moves
plunger 415 upward toward needle 210. A substance located in
dispensing chamber 405 is then expelled through needle 210.
[0040] In addition, controller 305 controls the operation of
temperature control device 450. Temperature control device 450 is
adapted to heat and/or cool dispensing chamber housing 425. Since
dispensing chamber housing 425 is at least partially thermally
conductive, heating or cooling dispensing chamber housing 425 heats
or cools a substance located in dispensing chamber 405. Temperature
information can be transferred from thermal sensor 460 to
controller 305 via any of a number of different interface
configurations. This temperature information can be used to control
the operation of temperature control device 450. When temperature
control device 450 is a heater, controller 305 controls the amount
of current that is sent to temperature control device 450. The more
current sent to temperature control device 450, the hotter it gets.
In such a manner, controller 305 can use a feed back loop utilizing
information from thermal sensor 460 to control the operation of
temperature control device 450. Any suitable type of control
algorithm, such as a proportional integral derivative (PID)
algorithm, can be used to control the operation of temperature
control device 450.
[0041] FIG. 5 is a cross section view of a disposable tip segment
for an ophthalmic medical device according to an embodiment of the
present invention. In FIG. 5, disposable tip segment 205 includes
housing 215, needle 210, plunger 415, plunger interface 420,
dispensing chamber 405, dispensing chamber housing 425, temperature
control device 450, thermal sensor 460, interface 530, and tip
interface connector 520. Disposable tip segment 205 operates as a
disposable injection device.
[0042] In the embodiment of FIG. 5, plunger 415 is located in
dispensing chamber housing 425. Dispensing chamber 405 is enclosed
by dispensing chamber housing 425 and plunger 415. Plunger 415
forms a fluid seal with the interior surface of dispensing chamber
housing 425. Needle 210 is fluidly coupled to dispensing chamber
405. In this manner, a substance located in dispensing chamber 405
can be contacted by plunger 415 and pushed out of needle 210.
Temperature control device 450 is located adjacent to dispensing
chamber housing 425 and at least partially surrounds dispensing
chamber 405. Housing 215 forms an outer skin on disposable tip
segment 205.
[0043] In various embodiments of the present invention, temperature
control device 450 is a heating and/or a cooling device.
Temperature control device 450 is in thermal contact with
dispensing chamber housing 425. As such, temperature control device
450 is capable of changing the temperature of the substance in
dispensing chamber 405. Interface 530 and tip interface connector
520 couple temperature control device 450 to a limited reuse
assembly. In such a case, temperature control device 450 can be
powered and controlled by the limited reuse assembly. In one
embodiment of the present invention, temperature control device 450
receives voltage via interface 530 from a limited reuse assembly.
Providing a positive voltage across the temperature control device
450 causes it to produce heat. Providing a negative voltage across
the temperature control device 450 causes it to cool.
[0044] A substance to be delivered into an eye, typically a drug,
is located in dispensing chamber 405. In this manner, the substance
is contacted by the inner surface of dispensing chamber housing 425
and one face of plunger 415. Typically, dispensing chamber 405 is
cylindrical in shape. Temperature control device 450 is in thermal
contact with dispensing chamber housing 425. In this manner,
temperature control device 450 is adapted to control the
temperature of the contents of dispensing chamber 425. Thermal
sensor 460 provides temperature information to assist in
controlling the operation of temperature control device 450.
[0045] In one embodiment of the present invention, the substance
located in dispensing chamber 405 is a drug that is preloaded into
the dispensing chamber. In such a case, disposable tip segment 205
is appropriate as a single use consumable product. Such a
disposable product can be assembled at a factory with a dosage of a
drug installed.
[0046] When a drug is preloaded into dispensing chamber 405, a set
quantity of the drug can be preloaded. For example, 100 microliters
of a drug can be loaded into dispensing chamber 405, and any
quantity up to 100 microliters can be dispensed. In such a case,
the plunger 415 can be moved a precise distance to deliver a
precise dosage of drug from the dispensing chamber 405, through the
needle 210, and into an eye. This provides for flexibility of
dosing and for ease of assembly.
[0047] FIG. 6 is a block diagram of an implementation of a drug
heating cycle limiter according to the principles of the present
invention. In FIG. 6, controller 305 interfaces with temperature
control device 450 and thermal sensor 460. Controller 305 receives
temperature information from thermal sensor 460 and uses that
information to control temperature control device 450.
[0048] FIG. 7 is a block diagram of an implementation of a drug
heating cycle limiter according to the principles of the present
invention. In FIG. 7, controller 305 includes counter 720 and timer
730. Controller 305 interfaces with thermal sensor 460 and switch
710. Switch 710 interfaces with temperature control device 450. In
the embodiment of FIG. 7, controller 305 controls the operation of
switch 710 to supply a first voltage (V1) or a second voltage (V2)
to temperature control device 450.
[0049] Switch 710 is any suitable type of mechanical or electronic
switch. Since the voltage supplied to temperature control device
450 is typically a low DC voltage, any number of different
electronically implemented switches may be used. In one embodiment,
a comparator is used as switch 710. Controller 305 provides an
input to control switch 710.
[0050] Controller 305 also includes a counter 720 and a timer 730.
While shown as separate blocks within controller 305, counter 720
and timer 730 may be implemented with software or hardware
contained in controller 305. Many electronic controllers, such as
microcontrollers, contain such timing and counting functions.
Counter 720 provides a counting function, and timer 730 provides a
timing function.
[0051] In operation, controller 305 operates switch 710 to provide
a first voltage (V1) to temperature control device 450. This first
voltage (V1) is typically higher then the second voltage (V2). The
first voltage (V1) brings the temperature control device to a set
point temperature quickly. When temperature control device 450 is a
heater, such as a resistive heater, applying a relatively high
first voltage (V1) brings the temperature of the heater up quickly.
Thermal sensor 460 measures the temperature of the heater (or a
temperature near the heater) and provides this information to
controller 305. When this temperature reaches the set point,
controller 305 operates switch 710 to provide the second voltage
(V2) to temperature control device 450. Again, when temperature
control device 450 is a heater, this second, relatively lower
voltage (V2), maintains temperature control device 450 at the set
point. In sum, the first voltage (V1) is chosen to bring the
temperature control device 450 to a desired temperature quickly,
and the second voltage (V2) is chosen to maintain the temperature
control device 450 at the desired temperature.
[0052] Counter 720 counts the number of times the temperature
control device 450 is operated to alter the temperature of a
substance contained in the dispensing chamber. Since the substance
in the dispensing chamber is typically a drug, it is desirable not
to stress the drug with excess heat or elevated temperatures. For
example, when a drug is suspended in a phase transition compound,
the phase transition compound is heated to bring it to a more
liquid state suitable for injection into the eye. Too much heat may
have a negative effect on the drug or may degrade it. Therefore, it
can be important to monitor the amount of heat that is applied to
the drug. Counter 720 achieves this by counting the number of
heating cycles the drug undergoes. For example, if a doctor turns
on the temperature control device to heat the phase transition
compound, and then leaves the device on without performing an
injection, the device turns itself off after a preset period of
time (the time the device is left on is calculated by timer 730).
The doctor may then turn the device on a second time, in which case
the counter increments by one. After a preset number of counts are
reached, the device is disabled indicating that the drug has been
exposed to a level of heating that is not desirable. In such a
case, the tip segment may be disabled to prevent it from being
used.
[0053] Timer 730 tracks the amount of time that temperature control
device 450 is on (and altering the temperature of the drug/phase
transition compound). Timer 730 begins timing when the temperature
control device 450 is turned on or when it reaches a steady state
temperature. In this manner, timer 730 keeps track of how long the
drug is exposed to heat (when temperature control device 450 is a
heater). In conjunction with counter 720, timer 730 can be used to
determine how much heat is applied to the drug.
[0054] FIG. 8 is a graph of one operation of a drug heating cycle
limiter according to the principles of the present invention. In
FIG. 8, time is depicted on the x-axis and temperature on the
y-axis. At time, t, the voltage applied across temperature control
device 450 is switched from V1 to V2. The temperature of
temperature control device 450 (when it is a heater) is depicted.
The temperature, T, is the set point or steady state temperature.
In this manner, voltage V1 is applied to bring temperature control
device to its set point in a relatively quick manner, and voltage
V2 is applied to maintain temperature control device at the set
point.
[0055] FIG. 9 is a flow chart of a method of operating a drug
heating cycle limiter according to the principles of the present
invention. In 1110, it is determined whether the limit number has
been reached. The limit number is the preset number of times that
the temperature control device is allowed to cycle in the tip
segment. Each cycle corresponds to a heating of the drug in the
dispensing chamber. For example, this limit number may be five. In
such a case, the temperature control device in a tip segment is
allowed to cycle five times before being disabled. If in 1110, the
limit number has been reached, then the system is disabled in 1130.
In one embodiment, a fuse located in the tip segment is blown to
prevent its reuse. If the limit number has not been reached, then
in 1120, the counter is incremented. Incrementing the counter
indicates that the temperature control device is to be cycled.
[0056] In 1140, a first voltage V1 is applied to the temperature
control device. In 1150, it is determined whether the temperature
control device has reached the steady state temperature (or set
point). If it has not reached its steady state temperature, then
the first voltage V1 continues to be applied across the temperature
control device. If it has reached its steady state temperature,
then in 1160, the second voltage V2 is applied to the temperature
control device. As previously mentioned, this second voltage V2
keeps the temperature control device at the steady state
temperature. In 1170, the timer is started. This timer counts the
amount of time that the temperature control device is at the steady
state temperature (and heating the drug--when the temperature
control device is a heater).
[0057] In 1180, it is determined whether the time limit has been
reached. The time limit is the amount of time that the temperature
control device is allowed to be left on without an injection being
performed. In one embodiment, the time limit is five minutes. In
such a case, the temperature control device is allowed to be on for
five minutes. If the doctor does not perform the injection
procedure within five minutes, then the time limit has been
reached. In such a case, the system is turned off (1190).
[0058] From the above, it may be appreciated that the present
invention provides an improved system for delivering precise
volumes of a substance into an eye. The present invention provides
a single use, disposable delivery device tip segment that is
capable of delivering a dosage of a drug. The tip segment
interfaces with a limited reuse assembly. The disposable tip
segment has a temperature control device and a thermal sensor. The
system monitors the amount of time that the temperature control
device is turned on and the number of cycles that the temperature
control device undergoes. Preset limits on these variables are used
to prevent further use of the device when the limits are exceeded.
In this manner, the drug contained in the tip segment is not
subjected to excessive temperature stresses.
[0059] While the present invention is described in the context of a
single-use ophthalmic drug delivery device, the present invention
encompasses any medical device or injection device. Other
embodiments of the invention will be apparent to those skilled in
the art from consideration of the specification and practice of the
invention disclosed herein. It is intended that the specification
and examples be considered as exemplary only, with a true scope and
spirit of the invention being indicated by the following
claims.
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