U.S. patent application number 11/606588 was filed with the patent office on 2008-05-29 for methods and apparatuses for detecting medical device acceleration, temperature, and humidity conditions.
Invention is credited to Ian B. Hanson, Jeffrey Ireland, Sheldon B. Moberg, Cary D. Talbot.
Application Number | 20080125700 11/606588 |
Document ID | / |
Family ID | 39464584 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080125700 |
Kind Code |
A1 |
Moberg; Sheldon B. ; et
al. |
May 29, 2008 |
Methods and apparatuses for detecting medical device acceleration,
temperature, and humidity conditions
Abstract
An ambulatory medical device for detecting acceleration,
temperature, and/or humidity conditions in or around the medical
device is provided. The medical device includes one or more
acceleration, thermal, and/or humidity sensors which detect
acceleration, temperature, and/or humidity conditions in or around
the medical device. In response to detected conditions, the medical
device may, among other things, alter the operation of the device,
provide an alarm or warning to the user, or transmit data about the
detected conditions to another device.
Inventors: |
Moberg; Sheldon B.;
(Thousand Oaks, CA) ; Hanson; Ian B.; (Northridge,
CA) ; Talbot; Cary D.; (Santa Clarita, CA) ;
Ireland; Jeffrey; (Thousand Oaks, CA) |
Correspondence
Address: |
MEDTRONIC MINIMED INC.
18000 DEVONSHIRE STREET
NORTHRIDGE
CA
91325-1219
US
|
Family ID: |
39464584 |
Appl. No.: |
11/606588 |
Filed: |
November 29, 2006 |
Current U.S.
Class: |
604/67 |
Current CPC
Class: |
A61M 2005/14264
20130101; A61M 5/172 20130101; A61M 2205/332 20130101; A61M 5/14244
20130101; A61M 2205/52 20130101; A61M 2205/3372 20130101; A61M
5/16831 20130101; A61M 2205/18 20130101 |
Class at
Publication: |
604/67 |
International
Class: |
A61M 5/172 20060101
A61M005/172 |
Claims
1. An external infusion device for infusing fluid into a person
from a reservoir, comprising: a housing adapted to be carried by on
an exterior of the person; a drive mechanism contained in the
housing and operatively coupled to the reservoir to deliver fluid
from the reservoir into the person's body; a processor contained in
the housing; a memory coupled to the processor and adapted to store
a predetermined temperature threshold; and a thermal sensor coupled
to the processor and adapted to provide a temperature output signal
as a function of temperature in the housing; wherein the processor
is adapted to compare the temperature output signal with the
predetermined temperature threshold, and to control the infusion
device based on the temperature comparison.
2. The external infusion device of claim 1, wherein the thermal
sensor is one of a thermoresistor, a thermocouple, a thermal flow
rate sensor, a resistance temperature detector, a platinum
resistor, a diode temperature sensor, a silicon transistor
thermometer, an integrated temperature transducer, a PTAT circuit,
a thermopile, a pyroelectric thermometer, and a quartz
thermometer.
3. The external infusion device of claim 1, further comprising an
indicator operatively coupled to the processor and adapted to
provide at least one of a visual indication, an audible indication,
or a tactile indication to indicate information to the person about
the infusion device.
4. The external infusion device of claim 3, wherein if the
temperature output signal exceeds the predetermined temperature
threshold, the processor is adapted to control the infusion device
by causing the indicator to provide an alarm or a warning to the
person about the temperature output signal.
5. The external infusion device of claim 4, wherein the fluid
infused into the person is medication, and the predetermined
temperature threshold corresponds to a temperature that causes the
medication to degrade, and further wherein the alarm or warning
indicates degradation of the medication to the person.
6. The external infusion device of claim 4, wherein the
predetermined temperature threshold corresponds to a temperature
that causes the indicator to malfunction, and further wherein the
alarm or warning indicates malfunction of the indicator to the
person.
7. The external infusion device of claim 3, wherein if the
temperature output signal is less than the predetermined
temperature threshold, the processor is adapted to control the
infusion device by causing the indicator to provide an alarm or a
warning to the person about the temperature output signal.
8. The external infusion device of claim 7, further comprising a
battery contained in the housing and adapted to provide power for
the infusion device, wherein the battery has a discharge
resistance, and wherein the predetermined temperature threshold
corresponds to a temperature that causes the discharge resistance
of the battery to increase by at least 10 percent, and further
wherein the alarm or warning indicates reduced life of the battery
to the person.
9. The external infusion device of claim 7, further comprising a
battery contained in the housing and adapted to provide power for
the infusion device, wherein the processor is adapted to sample the
battery at a first sampling frequency to determine remaining power
of the battery, and further wherein if the temperature output
signal is less than the predetermined temperature threshold, the
processor is further adapted to control the infusion device by
altering sampling of the battery from the first sampling frequency
to a second sampling frequency.
10. The external infusion device of claim 7, wherein the memory is
further adapted to store a predetermined force threshold
corresponding to a fluid occlusion in the infusion device, and
further wherein if the temperature output signal is less than the
predetermined temperature threshold, the processor is further
adapted to control the infusion device by modifying the
predetermined force threshold to provide a modified force
threshold.
11. The external infusion device of claim 1, further comprising a
transmitter/receiver contained in the housing and coupled to the
processor, wherein the transmitter/receiver is adapted to
communicate with a remote device, and further wherein the processor
is adapted to control the infusion device by causing the
transmitter/receiver to send information about the infusion device
to the remote device based on the temperature comparison.
12. An external infusion device for infusing fluid into a person,
comprising: a housing adapted to be carried by on an exterior of
the person's body; a processor contained in the housing; an
indicator operatively coupled to the processor and adapted to
provide at least one of a visual indication, an audible indication,
or a tactile indication to indicate information about the infusion
device to the person; a memory coupled to the processor and adapted
to store a predetermined humidity threshold; and a humidity sensor
coupled to the processor and adapted to provide a humidity output
signal as a function of humidity in or around the housing; wherein
the processor is adapted to compare the humidity output signal with
the predetermined humidity threshold, and to control the infusion
device based on the humidity comparison.
13. The external infusion device of claim 12, wherein the humidity
sensor is one of a capacitive humidity sensor, a resistive humidity
sensor, and a thermal conductivity humidity sensor.
14. The external infusion device of claim 12, wherein if the
humidity output signal exceeds the predetermined humidity
threshold, the processor is adapted to control the infusion device
by causing the indicator to provide an alarm or a warning to the
person about the humidity output signal.
15. The external infusion device of claim 14, wherein the
predetermined humidity threshold corresponds to entry of water into
the housing, and the indicator is adapted to provide the alarm or
warning to the person about the entry of water into the
housing.
16. The external infusion device of claim 12, wherein if the
humidity output signal is less than the predetermined humidity
threshold, the processor is adapted to control the infusion device
by causing the indicator to provide an alarm or a warning to the
person about the humidity output signal.
17. The external infusion device of claim 16, wherein the
predetermined humidity threshold corresponds to a humidity level
that causes the infusion device to be susceptible to damage due to
static electricity, and the indicator is adapted to provide the
alarm or warning to the person about the static electricity.
18. The external infusion device of claim 12, further comprising a
transmitter/receiver contained in the housing and coupled to the
processor, wherein the transmitter/receiver is adapted to
communicate with a remote device, and further wherein the processor
is adapted to control the infusion device by causing the
transmitter/receiver to send information about the infusion device
to the remote device based on the humidity comparison.
19. An external ambulatory medical device for use on a person's
body, comprising: a housing adapted to be carried by on an exterior
of the person's body; a processor contained in the housing; an
indicator operatively coupled to the processor and adapted to
provide at least one of a visual indication, an audible indication,
or a tactile indication to indicate information about the
ambulatory medical device to the person; a memory coupled to the
processor and adapted to store a predetermined temperature
threshold; and a thermal sensor coupled to the processor and
adapted to provide a temperature output signal as a function of
temperature in the housing; wherein the processor is adapted to
compare the temperature output signal with the predetermined
temperature threshold, and further wherein the processor is adapted
to control the ambulatory medical device and the indicator is
adapted to indicate information about the ambulatory medical device
based on the temperature comparison.
20. The ambulatory medical device of claim 19, wherein the
ambulatory medical device is an external infusion pump.
21. The ambulatory medical device of claim 19, wherein the
ambulatory medical device is a glucose monitoring device.
22. The ambulatory medical device of claim 19, further comprising a
transmitter/receiver contained in the housing and coupled to the
processor, wherein the transmitter/receiver is adapted to
communicate with a remote device, and further wherein the processor
is adapted to control the ambulatory medical device by causing the
transmitter/receiver to send information about the ambulatory
medical device to the remote device based on the temperature
comparison.
23. The ambulatory medical device of claim 19, wherein the thermal
sensor is one of a thermoresistor, a thermocouple, a thermal flow
rate sensor, a resistance temperature detector, a platinum
resistor, a diode temperature sensor, a silicon transistor
thermometer, an integrated temperature transducer, a PTAT circuit,
a thermopile, a pyroelectric thermometer, and a quartz
thermometer.
24. An external ambulatory medical device for use on a person's
body, comprising: a housing adapted to be carried by on an exterior
of the person's body; a processor contained in the housing; an
indicator operatively coupled to the processor and adapted to
provide at least one of a visual indication, an audible indication,
or a tactile indication to indicate information about the
ambulatory medical device to the person; a memory coupled to the
processor and adapted to store a predetermined humidity threshold;
and a humidity sensor coupled to the processor and adapted to
provide a humidity output signal as a function of humidity in or
around the housing; wherein the processor is adapted to compare the
humidity output signal with the predetermined humidity threshold,
and further wherein the processor is adapted to control the
ambulatory medical device and the indicator is adapted to indicate
information about the ambulatory medical device based on the
humidity comparison.
25. The ambulatory medical device of claim 24, wherein the
ambulatory medical device is an external infusion pump.
26. The ambulatory medical device of claim 24, wherein the
ambulatory medical device is a glucose monitoring device.
27. The ambulatory medical device of claim 24, further comprising a
transmitter/receiver contained in the housing and coupled to the
processor, wherein the transmitter/receiver is adapted to
communicate with a remote device, and further wherein the processor
is adapted to control the ambulatory medical device by causing the
transmitter/receiver to send information about the ambulatory
medical device to the remote device based on the humidity
comparison.
28. The ambulatory medical device of claim 24, wherein the humidity
sensor is one of a capacitive humidity sensor, a resistive humidity
sensor, and a thermal conductivity humidity sensor.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to improvements in
ambulatory medical devices, such as drug delivery systems or
patient monitoring systems, and more specifically, to improved
methods and apparatuses for detecting acceleration, temperature and
humidity conditions in or around these ambulatory medical
devices.
BACKGROUND OF THE INVENTION
[0002] Ambulatory medical devices, such as drug delivery systems
and patient monitoring systems, are used in the therapy of various
diseases or medical disorders, such as diabetes mellitus, pulmonary
hypertension, thalassemia, and chronic pain. Many such devices are
adapted to be carried by the user, for example, by means of a belt
clip or harness, in the user's clothing pocket, or attached to the
user's body or clothing.
[0003] A common drug delivery system includes a tubing arrangement
to deliver medication to a user cutaneously or subcutaneously. For
example, ambulatory infusion pumps are used in delivering a
prescribed medication, such as insulin, to a user. In one form,
these devices comprise a relatively compact pump housing adapted to
receive a syringe or reservoir carrying a prescribed medication for
administration to the user through infusion tubing and an
associated catheter or infusion set.
[0004] The external infusion pump may include a small drive motor
connected via a suitable transmission assembly for motor-driven
advancement of a reservoir piston to administer the medication to
the user. Programmable controls can operate the drive motor
continuously or at periodic intervals to obtain a closely
controlled and accurate delivery of the medication over an extended
period of time. Such infusion pumps are used to administer insulin
and other medications, with exemplary pump constructions and
systems being shown and described in U.S. Pat. Nos. 4,562,751;
4,678,408; 4,685,903; 5,080,653; 5,097,122; 6,248,093; 6,362,591;
6,554,798; and 6,555,986, which are incorporated by reference
herein.
[0005] External infusion pumps of the general type described above
have provided significant advantages and benefits with respect to
accurate delivery of medication or other fluids over an extended
period of time. The infusion pump can be designed to be extremely
compact as well as water resistant, and may be carried by the user,
for example, by means of a belt clip or harness, in the user's
clothing pocket, or attached to the user's body or clothing. As a
result, important medication can be delivered to the user with
precision and in an automated manner, without significant
restriction on the user's mobility or lifestyle, including in some
cases the ability to participate in water sports.
[0006] Due to their small size and portability, ambulatory medical
devices can be subjected to a number of external conditions that
may adversely affect their performance. For example, external
infusion pumps can sustain an occlusion in the delivery tubing.
Some pumps have alarm systems designed to detect and indicate pump
malfunction or nondelivery of the medication as a result of
occlusions. There exists, nevertheless, a need for further
improvements in these ambulatory medical devices, particularly with
respect to providing warnings or system operational changes in
response to external conditions that may affect medical device
performance.
BRIEF SUMMARY OF THE INVENTION
[0007] Disclosed are ambulatory medical devices that are adapted
for carrying by a person on an exterior of the person's body, and
include acceleration, thermal, and/or humidity sensors for
detecting conditions in or around the devices. In response to the
detected conditions, the medical devices may, among other things,
alter the operation of the devices, provide alarms or warnings to
the user, or transmit data to another device.
[0008] In one embodiment of the present invention, an ambulatory
medical device such as an external infusion device for infusing
fluid into a person from a reservoir comprises a housing adapted to
be carried on an exterior of the person's body. The infusion device
also includes a drive mechanism contained in the housing and
operatively coupled to the reservoir to deliver the fluid from the
reservoir into the person's body. The infusion device further
includes a processor contained in the housing, and an indicator
operatively coupled to the processor and adapted to indicate
information about the infusion device to the person. An
acceleration sensor also is coupled to the processor and is adapted
to provide an acceleration output signal as a function of
acceleration forces acting on the housing. The processor is adapted
to control the infusion device in accordance with the acceleration
output signal.
[0009] In particular embodiments, the infusion device further
includes a memory contained in the housing and coupled to the
processor. The memory is adapted to store a predetermined
acceleration threshold corresponding to an impact on the housing.
If the acceleration output signal exceeds the predetermined
acceleration threshold, the processor is adapted to control the
infusion device by causing the indicator to provide an alarm or a
warning to the person about the impact. Alternatively, the
processor is adapted to control the infusion device by causing the
drive mechanism to alter delivery of the fluid into the person's
body. In further alternative embodiments, the infusion device also
includes a transmitter/receiver coupled to the processor and
adapted to communicate with a remote device, and the processor is
adapted to control the infusion device by causing the
transmitter/receiver to send information about the impact to the
remote device.
[0010] In some embodiments, the acceleration sensor is an
accelerometer. In other embodiments, the acceleration sensor is an
impact switch disposed within the housing.
[0011] In additional embodiments, the infusion device also includes
a memory contained in the housing and coupled to the processor. The
memory is adapted to store a predetermined acceleration force
corresponding to a physical activity of the person. If the
acceleration output signal exceeds the predetermined acceleration
force, the processor is adapted to control the infusion device by
causing the indicator to notify the person about the physical
activity. Alternatively, the processor is adapted to control the
infusion device by causing the drive mechanism to alter delivery of
the fluid into the person's body from a current delivery rate to a
modified delivery rate. In further alternative embodiments, the
infusion device also includes a transmitter/receiver coupled to the
processor and adapted to communicate with a remote device, and the
processor is adapted to control the infusion device by causing the
transmitter/receiver to send information about the physical
activity to the remote device. In other embodiments, the memory is
further adapted to store data about at least one of frequency,
duration, and intensity of the physical activity of the person.
[0012] In another embodiment of the present invention, an
ambulatory medical device such as an external infusion device for
infusing fluid into a person from a reservoir comprises a housing
adapted to be carried on an exterior of the person's body. The
infusion device also includes a drive mechanism contained in the
housing and operatively coupled to the reservoir to deliver the
fluid from the reservoir into the person's body. The infusion
device further includes a processor contained in the housing, and a
memory coupled to the processor and adapted to store a
predetermined temperature threshold. A thermal sensor is also
coupled to the processor and adapted to provide a temperature
output signal as a function of temperature in the housing. The
processor is adapted to compare the temperature output signal with
the predetermined temperature threshold, and to control the
infusion device based on the temperature comparison.
[0013] In particular embodiments, the infusion device further
includes an indicator operatively coupled to the processor and
adapted to indicate information to the person about the temperature
output signal. In some embodiments, if the temperature output
signal exceeds the predetermined temperature threshold, the
processor is adapted to control the infusion device by causing the
indicator to provide an alarm or a warning to the person about the
temperature output signal. For example, the fluid infused into the
person's body may be medication, and the predetermined temperature
threshold may correspond to a temperature that causes the
medication to degrade, so that the alarm or warning may indicate
degradation of the medication to the person. In other embodiments,
if the temperature output signal is less than the predetermined
temperature threshold, the processor is adapted to control the
infusion device by causing the indicator to provide an alarm or a
warning to the person about the temperature output signal. For
example, the infusion device may further include a battery that is
adapted to provide power for the infusion device and has a
discharge resistance that varies with temperature. The
predetermined temperature threshold may correspond to a temperature
that causes the discharge resistance of the battery to increase by
at least 10 percent, so that the alarm or warning may indicate
reduced life of the battery to the person.
[0014] In additional embodiments, the infusion device includes a
battery adapted to provide power for the infusion device. The
processor is adapted to sample the battery at a first sampling
frequency to determine remaining power of the battery. If the
temperature output signal is less than the predetermined
temperature threshold, the processor is further adapted to control
the infusion device by altering sampling of the battery from the
first sampling frequency to a second sampling frequency.
[0015] In further embodiments, the memory is also adapted to store
a predetermined force threshold corresponding to a fluid occlusion
in the infusion device. If the temperature output signal is less
than the predetermined temperature threshold, the processor is
adapted to control the infusion device by modifying the
predetermined force threshold to provide a modified force
threshold.
[0016] In yet another embodiment of the present invention, an
ambulatory medical device such as an external infusion device
comprises a housing adapted to be carried by a person and a
processor contained in the housing. The infusion device also
includes an indicator operatively coupled to the processor and
adapted to indicate information about the infusion device to the
person. A memory is coupled to the processor and adapted to store a
predetermined humidity threshold. The infusion device further
includes a humidity sensor coupled to the processor and adapted to
provide a humidity output signal as a function of humidity in or
around the housing. The processor is adapted to compare the
humidity output signal with the predetermined humidity threshold,
and to control the infusion device based on the humidity
comparison.
[0017] In particular embodiments, if the humidity output signal
exceeds the predetermined humidity threshold, the processor is
adapted to control the infusion device by causing the indicator to
provide an alarm or a warning to the person about the humidity
output signal. For example, the predetermined humidity threshold
may correspond to entry of water into the housing, and the
indicator is adapted to provide the alarm or warning to the person
about the entry of water into the housing. In other embodiments, if
the humidity output signal is less than the predetermined humidity
threshold, the processor is adapted to control the infusion device
by causing the indicator to provide an alarm or a warning to the
person about the humidity output signal. For example, the
predetermined humidity threshold may correspond to a humidity level
that causes the infusion device to be susceptible to damage due to
static electricity, and the indicator is adapted to provide the
alarm or warning to the person about the static electricity.
[0018] There are additional aspects to the present invention. It
should therefore be understood that the preceding is merely a brief
summary of some embodiments and aspects of the present inventions.
Additional embodiments and aspects of the present inventions are
referenced below. It should further be understood that numerous
changes to the disclosed embodiments can be made without departing
from the spirit or scope of the invention. The preceding summary
therefore is not meant to limit the scope of the invention. Rather,
the scope of the invention is to be determined by appended claims
and their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is aperspective view of an infusion pump according to
an embodiment of the present invention.
[0020] FIG. 2 is a side plan, cut-away view of an infusion pump
drive system in accordance with an embodiment of the present
invention.
[0021] FIG. 3 is a simplified block diagram of an infusion pump and
system in accordance with an embodiment of the present
invention.
[0022] FIG. 4 is a simplified schematic diagram of an impact switch
in accordance with one embodiment of the invention.
[0023] FIG. 5 is a simplified schematic diagram of an impact switch
in accordance with an alternative embodiment of the invention.
[0024] FIG. 6 is a simplified schematic diagram of an impact switch
in accordance with an alternative embodiment of the invention.
[0025] FIG. 7 is a simplified schematic diagram of an impact switch
in accordance with an alternative embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] In the following description, reference is made to the
accompanying drawings which form a part hereof and which illustrate
several embodiments of the present invention. It is understood that
other embodiments may be used, and structural and operational
changes may be made without departing from the scope of the present
invention.
[0027] As shown in the drawings for purposes of illustration, the
invention is embodied in an ambulatory medical device that includes
acceleration, thermal, and/or humidity sensors for detecting
acceleration, temperature, and/or humidity conditions in or around
the medical device. In response to detected conditions, the medical
device may alter operation of the medical device, provide alarm or
text messages to the user, and/or transmit data about the detected
conditions to another device or system. In one embodiment, the
medical device is a drug delivery system, such as an external
infusion pump for delivering insulin into the body of a user.
However, in alternative embodiments, the medical device may be
other drug delivery systems for delivering other fluids into the
body of the user, such as medication other than insulin (e.g., HIV
drugs, drugs to treat pulmonary hypertension, iron chelation drugs,
pain medications, and anti-cancer treatments), chemicals, enzymes,
antigens, hormones, vitamins, or the like. In other alternative
embodiments, the medical device may be a patient monitoring system,
such as a continuous glucose monitoring system for determining
glucose levels in the blood or other bodily fluids of the user. In
further alternative embodiments, the medical device may be other
patient monitoring systems (e.g., pulse rate monitors,
electrocardiogram monitors, and the like, such as the Holter
monitor) for determining the concentrations, levels, or quantities
of other characteristics, analytes, or agents in the user, such as
hormones, cholesterol, oxygen, pH, lactate, heart rate, respiratory
rate, medication concentrations, viral loads (e.g., HIV), or the
like.
[0028] One example of an ambulatory medical device is the external
infusion pump 100 shown in FIG. 1. The pump 100 includes a housing
101 that contains an electronics compartment (not shown), including
a processor (not shown) for running programs and controlling the
pump 100. The pump 100 may be programmed by a care provider, such
as a physician or trained medical personnel, or by the user. To
program the pump 100, an individual utilizes a display 102 and a
keypad of buttons 104, 106, 108, 110, and 112 located on the
housing 101 to access and/or modify control parameters and data for
the pump 100. The display 102 provides information regarding
program parameters, delivery profiles, pump operation, alarms,
warnings, statuses, or the like. In the embodiment shown in FIG. 1,
the pump 100 has five buttons or keys including an Up-Arrow key
104, an ACT (activate) key 106, a Down-Arrow key 108, an ESC
(escape) Key 110, and an Express Bolus key 112. In alternative
embodiments, the pump 100 may utilize more or less keys or have
different key arrangements than those illustrated in the figure.
The pump 100 uses the control parameters to calculate and issue
commands that affect the rate and/or frequency that the pump 100
delivers fluid, preferably medication such as insulin, through a
fitting 202 and flexible tubing 204, and into an infusion set 206
that is adhered to the body of the user.
[0029] FIG. 2 illustrates a drive system for an infusion pump 301
according to an embodiment of the present invention. The pump 301
includes a housing 318 that contains an electronics compartment
310. The electronics compartment 310 houses a power supply (not
shown) for providing power to operate the pump 301, and system
electronics for the pump 301, including a processor (not shown) for
running programs and controlling the pump 301. The housing 318 of
the pump 301 also contains a drive mechanism including a motor 302,
gear box 306, drive screw 303, slide 304, stopper 307, and
reservoir 305, which are generally concentrically aligned. The
motor 302 rotates the drive screw 303 via the gear box 306. The
drive screw 303 has external threads, which engage internal threads
322 on a cylindrical bore 320 running most of the length of the
slide 304. Thus, the rotational torque of the drive screw 303 is
translated into axial force on the slide 304. The slide 304 further
includes one or more tabs 314 that fit within one or more slots 316
in the housing 318 to prevent the slide 304 from rotating with
respect to the housing 318. As the drive screw 303 rotates, the
slide 304 is forced to travel along its axis. The slide 304 is in
removable contact with the stopper 307 within the reservoir 305. As
the slide 304 advances into the reservoir 305, the stopper 307 is
displaced forcing fluid out of the reservoir 305, through a fitting
308 and tubing 309, and into an infusion set (not shown) attached
to the body of the user.
[0030] A sensor 311 is positioned between the motor 302 and the
housing 318 to detect forces translated from fluid pressure within
the reservoir 305 through the stopper 307, slide 304, drive screw
303, and the gear box 306 to the motor 302. The sensor 311 provides
a range of measurements based on the detected forces. However,
because the infusion pump 301 can be carried by users who engage in
a variety of physical activities and travel, the pump 301 can be
subjected to various environmental changes that do not always
result in occlusions, but nevertheless can either adversely affect
performance of the pump 301 or indicate a need to vary operation of
the pump 301 due to changing medication needs of the user.
Therefore, the pump 301 also includes acceleration, thermal, and/or
humidity sensors (not shown) which, as explained in greater detail
below, can detect acceleration, temperature, and/or humidity
conditions in or around the pump 301, and in response to the
detected conditions, the pump 301 may alter its operation, provide
an alarm or text message to the user, or transmit data to another
device.
[0031] FIG. 3 illustrates one hardware and software environment in
which certain embodiments of the present invention may be
implemented. In one embodiment, an ambulatory medical device is a
drug delivery system, such as an external infusion pump, for
regulating the delivery of medication such as insulin into the body
of a user. Examples of the infusion pump may be of the type shown
and described in U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903;
5,080,653; 5,097,122; 5,505,709; 6,248,093; 6,362,591; 6,554,798;
6,555,986; and 6,752,787, which are herein incorporated by
reference.
[0032] As shown in FIG. 3, the infusion pump 410 includes a housing
420 that contains a processor 418 adapted to control the pump 410.
The processor 418 is coupled to a drive mechanism 432, which is
connected to a reservoir 434 containing fluid. The drive mechanism
432 causes the fluid to be delivered from the reservoir 434, and
then into a body of a user through tubing and an infusion set 438.
The processor 418 is also coupled to an internal memory device 422
that stores programs, historical data, user-defined information,
and parameters. In one embodiment, the memory 422 is a flash memory
and SRAM; however, in alternative embodiments, the memory 422 may
comprise other devices, such as ROM, DRAM, RAM, EPROM, dynamic
storage such as other flash memory, or an energy efficient
hard-drive.
[0033] The infusion pump 410 is programmed by a user input device,
such as a keypad 424 mounted on the exterior of the housing 420 and
coupled to the processor 418. An individual, such as a care
provider or a user, presses keys on the keypad 424 to display and
scroll through information, call up menus, select menu items,
select control parameters, change control parameters (change values
or settings), enter information, turn on a backlight, and the like.
Feedback from the infusion pump 410 on status or programming
changes is provided to the individual on an indication device, such
as visually on a display 428, audibly through an audible alarm 430
(e.g., piezo buzzer, annuciator, speaker, or the like), and/or
tactilely through a vibration alarm 416. The individual may
activate or deactivate the audible alarm 430 and/or the vibration
alarm 416 by accessing control parameters on the pump 410. Feedback
from the infusion pump 410 may include signals that notify the
individual of modifications to the control parameters, announce
that the infusion pump 410 is about to initiate a particular
operation, indicate a mode of operation, provide a warning (for
instance to indicate a low fluid level in the reservoir or low
battery power), present an alarm (such as from a timer or a clock),
present an error message to indicate a malfunction of the system
(such as an occlusion that restricts the delivery of the fluid, a
software error, or the like), request input, confirm that
communication has been established, and the like. Alarms and
warnings may start out at a low level and escalate until
acknowledged by the user. In particular embodiments, the alarm
intensity changes over time. If the individual does not respond to
the alarm, the alarm may change tone, change volume, increase the
vibration amplitude or frequency, project a brighter light or a
different color light, flash, flash at a different frequency, and
the like. In alternative embodiments, the intensity may vary up or
down, or alternatively, the intensity may be constant. In other
alternative embodiments, the intensity may change by activating
different alarm types over time.
[0034] In further alternative embodiments, the keypad 424 may be
omitted, and the display 428 may be used as a touch screen input
device. In yet other alternative embodiments, the infusion pump 410
may be programmed by commands received from a remote programmer 415
(e.g., PDA, programmer dedicated to communication with the infusion
pump 410, or the like) through a transmitter/receiver 417 that is
coupled to the processor 418. The remote programmer 415 may be used
to program the infusion pump 410 in addition to the keypad 424,
display 428, audible alarm 430, and/or vibration alarm 416.
Alternatively, the keypad 424, display 428, audible alarm 430,
and/or vibration alarm 416 may be omitted, and all programming may
be handled by the remote programmer 415. In other alternative
embodiments, the infusion pump 410 may be programmed through an
interface, such as a cable or communication station, using a
computer or the like.
[0035] In the illustrated embodiment, a power supply 440, such as a
battery, provides the power to operate the infusion pump 410. In
particular embodiments, the power supply is one or more replaceable
AAA batteries. Energy storage devices such as capacitors, backup
batteries, or the like provide temporary power to maintain the
memory during power supply replacement. In alternative embodiments,
the power supply is one or more button batteries, zinc air
batteries, alkaline batteries, lithium batteries, lithium silver
oxide batteries, AA batteries, or the like. In still further
alternative embodiments, the power supply is rechargeable.
[0036] The infusion pump 410 may also allow the user to transfer or
download information (e.g., infusion pump history data, sensor
data, data from other medical devices, updates to programs, or the
like) between the memory 422 of the infusion pump 410 and an
external device, such as the remote programmer 415, a computer,
another medical device (e.g., blood glucose meter, glucose
monitor), or the like. For example, information may be transferred
to and/or from the infusion pump 410 through an interface, such as
a cable or communication station, to a computer, or alternatively,
over the Internet to a remote server, for storage. Alternatively,
information may be transferred to and/or from the
transmitter/receiver 417 of the infusion pump 410 via a wireless or
wired connection to a transmitter/receiver in an external device,
such as an external communication link, computer, the remote
programmer 415, or the like. The transmitter/receiver 417 of the
infusion pump 410 may communicate with external devices using radio
frequencies; however, alternative embodiments may use optical,
infrared (IR), ultrasonic frequencies, magnetic effects, electrical
cables, or the like.
[0037] In other alternative embodiments, the infusion pump may
include separate durable and disposable housing portions that
selectively engage and disengage from each other. The durable
housing portion may include the electronics (e.g., processor,
memory, and the like) and drive mechanism, and the disposable
housing portion may include the reservoir and/or other components
that may be disposed of after a prescribed period. Such an infusion
pump may be of the type shown and described in U.S. Provisional
Application Ser. No. 60/678,290 filed May 6, 2005 and entitled
"Infusion Device and Method with Disposable Portion," U.S.
application Ser. No. 11/211,095 filed Aug. 23, 2005 and entitled
"Infusion Device and Method with Disposable Portion," and U.S.
application Ser. No. 11/210,467 filed Aug. 23, 2005 and entitled
"Infusion Device and Method with Drive Device in Infusion Device
and Method with Drive Device in Separable Durable Housing," all of
which are herein incorporated by reference. Such an infusion pump
may also be of the type shown and described in U.S. Provisional
Application Ser. No. 60/839,821 filed Aug. 23, 2006 and entitled
"Systems and Methods Allowing for Reservoir Filling and Infusion
Medium Delivery," U.S. Provisional Application Ser. No. 60/839,822
filed Aug. 23, 2006 and entitled "Infusion Medium Delivery Device
and Method with Drive Device for Driving Plunger in Reservoir,"
U.S. Provisional Application Ser. No. 60/839,832 filed Aug. 23,
2006 and entitled "Infusion Medium Delivery Device and Method with
Compressible or Curved Reservoir or Conduit," U.S. Provisional
Application Ser. No. 60/839,840 filed Aug. 23, 2006 and entitled
"Infusion Medium Delivery System, Device and Method with Needle
Inserter and Needle Inserter Device and Method," and U.S.
Provisional Application Ser. No. 60/839,741 filed Aug. 23, 2006 and
entitled "Infusion Pumps and Methods and Delivery Devices and
Methods with Same," all of which are herein incorporated by
reference.
[0038] As previously discussed, ambulatory medical devices,
including drug delivery systems such as an external infusion pump,
may encounter various environmental changes that could adversely
affect performance. For example, a pump can be damaged if dropped
or bumped onto a hard object or surface such as a floor, doorway,
counter or desk. If the pump is dropped or bumped with sufficient
force, it may become damaged to an extent that it cannot adequately
perform its intended functions. The tubing, infusion set, or
reservoir may become damaged such that medication leaks out and is
not delivered to the user. Also, the pump housing may become
cracked, or the electronics or power supply or drive mechanism
contained within the pump may become damaged by the impact. If the
pump lacks the ability to detect and alarm for this condition, the
user may not receive the expected medication and may experience
adverse effects such as hyperglycemia. Additionally, if the pump
becomes damaged due to an impact, it would be useful to indicate
this condition to the user, such as by an alarm (display, audio or
vibratory), thus notifying him or her of the need to check the pump
for damage. Furthermore, if the pump is dropped or bumped with
sufficient force along the axis of the reservoir, unintended
medication delivery may occur. The user may unexpectedly receive
medication, and as a result, experience hypoglycemia. It would be
useful to notify the user of the impact so that the user could take
preventative measures to avoid hypoglycemia.
[0039] Ambulatory medical devices may also come into contact with
external fluids such as water or cleaning agents. For example, some
external infusion pumps are labeled for use in water. If the pump
housing becomes cracked due to an impact, fluid may be able to
enter the pump, and as a result, the pump may no longer function
properly. Again, it would be useful to notify the user of this
potential condition, thus permitting a self-check of the pump or
notification of the manufacturer or a repair facility for
assistance.
[0040] Therefore, the infusion pump 410 further includes an
acceleration sensor 414, a thermal sensor 426, and a humidity
sensor 412. The acceleration, thermal, and humidity sensors 414,
426, and 412 are coupled to and communicate with the processor 418.
For example, based on data from the acceleration, thermal, and/or
humidity sensors 414, 426, and 412, the processor 418 may: (1)
cause the drive mechanism 432 to alter the fluid delivery rate, (2)
activate the display 428, audible alarm 430, and/or vibration alarm
416 to provide alarms or warnings to the user, and/or (3) utilize
the transmitter/receiver 417 to send data to another device, such
as the remote programmer 415 or other remote devices or systems via
remote data communication network(s). Examples of communication
between the pump 410 (or other medical device) and a remote device
or system via a remote data communication network may be of the
type shown and described in U.S. application Ser. No. 11/414,160
filed Apr. 28, 2006 and entitled "Remote Monitoring for Networked
Fluid Infusion Systems," which is herein incorporated by reference.
For example, the pump 410 may transmit information (e.g., warnings,
alarms, notifications) based on data from the acceleration,
thermal, and/or humidity sensors 414, 426, and 412 to a remote
device carried by the user's caregiver or physician via a computer
network, pager network, cellular telecommunication network,
satellite communication network, or the like. Additionally, the
memory 422 is adapted to store values associated with the outputs
of the acceleration sensor 414, the thermal sensor 426, and the
humidity sensor 412, as well as values associated with
predetermined acceleration forces, temperatures, and humidity
levels.
[0041] In alternative embodiments of the present invention, the
ambulatory medical device may be other drug delivery systems for
delivering other fluids into the body of the user, such as
medication other than insulin (e.g., HIV drugs, drugs to treat
pulmonary hypertension, iron chelation drugs, pain medications, and
anti-cancer treatments), chemicals, enzymes, antigens, hormones,
vitamins, or the like. In other alternative embodiments, the
medical device may be a patient monitoring system, such as a
continuous glucose monitoring system, for obtaining an indication
of glucose levels in the blood or other fluids in the body of a
user. Examples of the continuous glucose monitoring system may be
of the type shown and described in U.S. Pat. Nos. 6,248,067;
6,418,332; 6,424,847; 6,809,653; and 6,895,263, which are herein
incorporated by reference. In further alternative embodiments, the
medical device may be other patient monitoring systems (e.g., pulse
rate monitors, electrocardiogram monitors, and the like, such as
the Holter monitor) for determining the concentrations, levels, or
quantities of other characteristics, analytes, or agents in the
user, such as hormones, cholesterol, oxygen, pH, lactate, heart
rate, respiratory rate, medication concentrations, viral loads
(e.g., HIV), or the like. Such medical devices may include
acceleration, thermal, and/or humidity sensors similar to the
sensors 414, 426, and 412.
[0042] In particular embodiments, an acceleration sensor 414 is
included within an ambulatory medical device such as the infusion
pump 410 and is used as an indicator of potential damage to the
pump 410 due to an impact. In one embodiment, the acceleration
sensor 414 is an accelerometer which provides a signal that is
proportional to the acceleration (or deceleration) forces (i.e.,
the rate of change of velocity with respect to time) to which the
pump 410 is subjected. The processor 418 within the pump 410
monitors the signal from the accelerometer for a value larger than
a predetermined or programmed threshold stored in memory 422, and
if the accelerometer signal reaches that threshold, the processor
418 causes an alarm or warning to be provided to the user visually
on the display 428, audibly by the audible alarm 430, and/or
tactilely with the vibration alarm 416. The acceleration threshold
may be determined by testing or other methods to be the
acceleration which may potentially cause damage to any part of the
pump 410.
[0043] Accelerometers typically have one or more axes of
sensitivity. In the simplest form, the accelerometer can have a
single axis of sensitivity. Therefore, the signal generated from
the accelerometer will be the vector sum of accelerations along
that axis. This property can be beneficial since the accelerometer
can be mounted such that its axis of sensitivity is aligned with
the direction of most concern within the ambulatory medical
device.
[0044] If there is concern for damage to the medical device along
multiple directions (axes), then multiple, single-axis
accelerometers can be used. Alternatively, a single acceleration
sensor may have multiple axes of sensitivity and detect
acceleration in a plurality of directions. One example of such an
acceleration sensor is described in U.S. Pat. No. 5,833,713. Again,
this sensor can be mounted in the medical device in an orientation
that monitors acceleration signals in the desired directions.
[0045] If there is concern for damage to the medical device due to
impact in any direction, then a 3-axis accelerometer can be used,
such as one manufactured by Entran Devices, Inc., Fairfield, N.J. A
3-axis orthogonal accelerometer can be mounted as a discrete
component within the medical device, such as within the housing,
attached to a mechanical component, or directly on a printed
circuit board. For example, such an accelerometer could be mounted
within the housing 420 of the pump 410, attached to a component of
the drive mechanism 432, or directly on the circuit board that
includes the processor 418 or other electronic components.
[0046] Furthermore, if it is desirable to have different levels of
sensitivity along multiple axes, then an accelerometer with
discrete axes of sensitivity can be mounted along each of those
axes (i.e. orthogonal or not orthogonal) and monitored and
processed independently. For example, the acceleration sensor 414
within the pump 410 can be an orthogonal 3-axis accelerometer and
monitor the signals from each axis independently. If, in this
example, it is desired to have different levels of sensitivity
along the axis of the reservoir 434, the axis perpendicular to the
display 428, and the corresponding orthogonal axis, then the
accelerometer can be mounted so that each of the three orthogonal
sensor axes is aligned with one of those directions. Thus, each of
these axes can be monitored independently and produce acceleration
signals corresponding to impacts in those directions.
[0047] Varying acceleration threshold levels can be programmed into
the pump 410 for each of these axes or combination of axes to
produce the appropriate alarm or warning messages. For example, a
light impact generating a relatively low acceleration level can
result in a warning to the user to look for potential damage to
his/her pump 410, whereas a hard impact generating a relatively
high acceleration level can result in an alarm and instructions for
the user to call the manufacturer and return the pump 410 for
analysis. The processor 418 may activate the display 428, audible
alarm 430, and/or vibration alarm 416 to provide alarms or warnings
to the user. For example, the pump 410 can alarm and instruct the
user to investigate damage, such as a leaking infusion set 438 or
broken reservoir 434, a cracked pump housing 420 or damage to the
power supply 440 or other electronic components. The pump 410 can
also instruct the user to perform a self-check, or it can
automatically run a self-check to identify damage that may not be
visible to the user. Further, the processor 418 may cause the drive
mechanism 432 to alter the delivery of fluid to the user or
activate the transmitter/receiver 417 to cause data, such as
alarms, to be sent to another device, such as the remote programmer
415.
[0048] Accelerometers are based on several different technologies,
such as piezoelectric, thermal, servo, strain gauge, capacitance,
micro-electro-mechanical systems ("MEMS"), and resonance shift.
Each of these technologies has different advantages. Piezoelectric
("PE") sensors generate a charge when strained. Since PE sensors
generate their own signal, they are referred to as active sensors.
However, PE sensors provide only an AC response, and thus, can only
detect impacts or shock to the medical device. Such PE sensors are
available from several companies including Measurement Specialties,
Inc., Fairfield, N.J.
[0049] Another class of sensors is referred to as passive sensors,
which change some measurable property when strained. For example, a
piezoresistive sensor changes its resistance when strained.
Piezoresistive sensors provide both an AC and DC response, and
thus, can detect both impacts or shock to, as well as slight tilt
or movement of, the medical device. However, in order to measure
the change in resistance, piezoresistive sensors require a constant
power supply. Other examples of passive sensors include capacitive
based sensors which measure a change in capacitance when strained,
and resonance shift sensors which measure a shift in frequency when
loaded or strained.
[0050] The choice of sensor technology depends on the available
power supply, the need to measure a steady-state (DC) input, and
the desired frequency of measurement. In the case of many
ambulatory medical devices such as external infusion pumps, the
power supply is limited to a battery. In one embodiment of such a
medical device, continuous non-DC measurement may be desired.
Therefore, a sensor technology that requires very low power to
operate is often desirable for such medical devices. Since
piezoresistive sensors require a constant power supply to operate,
this sensor technology may not be appropriate. However, since
piezoelectric sensors are active devices that can generate a
signal, less power may be required to operate them, and thus, they
may be a more desirable sensor technology for battery-powered,
ambulatory medical devices such as external infusion pumps.
[0051] In alternative embodiments, the acceleration sensor 414
incorporated into an ambulatory medical device such as the infusion
pump 410 may be an impact or acceleration switch, which provides an
"on" or "off" output signal when its seismic mass is subjected to a
predetermined level of acceleration. FIG. 4 shows a simplistic
representation of an impact switch 601 with an "on" or "off" state.
The switch 601 includes a seismic mass 618 comprised of an
electrically conductive arm 602 and an electrically conductive plug
606. The arm 602 is pivotably coupled to a housing 604 of the
medical device, and the plug 606 is mounted on the free end of the
arm 602. The plug 606 is electrically coupled to the arm 602, and
the arm 602 is electrically coupled to an electrical output 614. In
yet another embodiment, the plug 606 may be omitted, and the
seismic mass 618 may simply include the arm 602 having a free end
and adapted to be held by a latch mechanism.
[0052] The switch 601 also includes a first electrically conductive
latch 608 and a second electrically conductive latch 616, which are
adapted to releasably secure the plug 606 and are electrically
coupled to an electrical input 612. In the illustrated embodiment,
the first and second latches 608 and 616 are latch springs having a
concave-shaped cross section. The plug 606 has a complementary
concave-shaped cross-section that allows the plug 606 to mate with
either of the latch springs 608 or 616. However, in other
embodiments, the latches 608 and 616 and the plug 606 may have
alternative geometries or latching mechanisms.
[0053] In the illustrated embodiment, the switch 601 further
includes two opposed springs 610 that bias the arm 602 such that
the plug 606 is in a spaced-apart relationship between the first
latch 608 and the second latch 616. In one embodiment, the springs
610 may be coil springs; however, in alternative embodiments, the
springs 610 may be other biasing elements, such as leaf springs or
the like.
[0054] Referring back to FIG. 4, when the medical device is
subjected to an acceleration force of a predetermined magnitude and
direction along an axis of sensitivity of the switch 601, the arm
602 will pivot toward one of the latches 608 or 616, and the plug
606 will be releasably secured by that latch 608 or 616. As a
result, a circuit between the electrical input 612 and the
electrical output 614 will be closed, thereby providing an output
signal that indicates the medical device has been subjected to an
acceleration force of the predetermined magnitude and direction
along the axis of sensitivity of the medical device.
[0055] One advantage of an impact switch that can maintain its
"on/off" state relates to the operation of the electronics within a
battery-operated, ambulatory medical device such as an external
infusion pump. It is common for certain sub-systems requiring
higher power (e.g., microprocessor, power supply, motor, or
measurement system) to shut down when not in use, and then
"wake-up" only during scheduled times to perform their operation or
function, in order to extend battery life. Because the switch can
maintain its change of state (i.e., the electrical connection
between the electrical input and electrical output) due to an
impact, the medical device does not have to continuously monitor
for a signal from the impact switch. Thus, the medical device can
shut down certain system electronics when not in use, and wait
until the next time the system electronics "wake-up" to check for a
signal from the switch. As described above, the appropriate alarms
or warnings can be provided to the user upon detecting a signal
from the impact switch. Alternatively, the switch can cause the
drive system to be shut down so that the drive system cannot be
inadvertently activated due to the impact.
[0056] FIG. 5 shows an alternative embodiment of an impact switch
701 that can maintain its "on/off" state. The switch 701 includes a
seismic mass 718 comprised of an electrically conductive arm 702
and an electrically conductive contact member 706. The arm 702 is
pivotably coupled to a housing 704 of the medical device, and the
contact member 706 is mounted on the free end of the arm 702. The
arm 702 and the contact member 706 are electrically coupled to one
another and to a switch electrical output 714. In another
embodiment, the contact member 706 may be omitted, and the seismic
mass 718 may simply include the arm 702 having a free end and
adapted to abut and be held in position by an electromagnet.
[0057] The switch 701 also includes first and second electromagnets
708 and 720, which are adapted to generate magnetic fields that
individually have sufficient strength to releasably hold the
contact member 706, at least a portion of which is constructed of a
ferromagnetic material. The first and second electromagnets 708 and
720 are also electrically coupled to a switch electrical input 712.
Power to the electromagnets 708 and 720 for generating the magnetic
fields is provided via a magnet electrical input 722 and a magnet
electrical output 724. A reset switch 716 electrically connects the
magnet electrical input 722 to the magnet electrical output 724
when the switch 716 is closed, thus shunting the electricity flow
from the electromagnets 708 and 720 and causing the magnetic field
to collapse.
[0058] In the illustrated embodiment, the switch 701 further
includes two opposed springs 710 that bias the arm 702 such that
the contact member 706 is in a spaced-apart relationship between
the first and second electromagnets 708, 720. In one embodiment,
the springs 710 may be coil springs; however, in alternative
embodiments, the springs 710 may be other biasing elements, such as
leaf springs or the like.
[0059] Referring back to FIG. 5, when the switch 701 is subjected
to an acceleration force of a predetermined magnitude and direction
along an axis of sensitivity of the switch 701, the arm 702 will
pivot toward one of the electromagnets 708 or 720, and the contact
member 706 will abut the electromagnet 708 or 720 and be releasably
held in position by its magnetic field. As a result, a circuit
between the switch electrical input 712 and the switch electrical
output 714 is closed, thereby providing an output signal that
indicates the medical device has been subjected to an acceleration
force of the predetermined magnitude and direction along the axis
of sensitivity of the medical device. When it is desired to reset
the impact switch 701, the reset switch 716 is closed, thus
collapsing the magnetic fields and releasing the contact member 706
to return to its initial position between the electromagnets 708
and 720.
[0060] As with the switch 601 of FIG. 4, this switch 701 of FIG. 5
also will latch its condition upon experiencing a predetermined
acceleration force. However, this type of switch 701 may be better
suited for reset following acknowledgement of an alarm since
electromagnets 708 and 720 are used to hold the contact member 706.
The use of a switch, such as the reset switch 716 of FIG. 5, to
reset the impact switch 701 after an alarm may be more convenient
in some applications than the use of a mechanical release mechanism
to release the latch plug 606 from one of the latches 608 or 616 in
the embodiment of FIG. 4.
[0061] FIG. 7 illustrates another embodiment of an impact switch
901 that can be incorporated as an acceleration sensor 414 into an
ambulatory medical device such as an external infusion pump 410.
The impact switch 901 includes a seismic mass 904 comprised of an
electrically conductive arm member 902 and an electrically
conductive impact head 906. The arm 902 has one end rigidly coupled
to a housing 916 of the medical device. Alternatively, the arm 902
may be coupled to electronics (not shown) contained within the
housing of the medical device. In the illustrated embodiment, the
impact head 906 is mounted on the free end of the arm 902 and is
electrically coupled to the arm 902. The arm 902 is constructed of
a material that permits resilient deflection and is electrically
coupled to an electrical output 914. For example, the arm 902 can
be constructed of stainless steel or beryllium copper, or other
materials having the desired resiliency and electrical
conductivity.
[0062] The switch 901 also includes two electrically conductive
contacts 908 and 910, which are fixedly mounted adjacent to the
impact head 906 and are electrically coupled to an electrical input
912. Thus, the impact head 906 is in a spaced-apart relationship
between the contacts 908 and 910 when no acceleration force acts on
the medical device.
[0063] When the medical device is subjected to an acceleration
force of a predetermined magnitude and direction along an axis of
sensitivity of the switch 901, the arm 902 will deflect toward one
of the contacts 908 or 910, and the head 906 will briefly touch
that contact 908 or 910 before returning to its equilibrium
position. When this occurs, the electrical circuit between the
electrical input 912 and the electrical output 914 is momentarily
closed, thus producing a voltage spike or pulse at the electrical
output 914. System electronics monitor the output 914 for such a
voltage pulse, and provide an appropriate alarm or other indication
as described above when such a pulse is detected.
[0064] FIG. 6 shows yet another embodiment of an impact switch 801,
which employs a principle similar to that of the switch 901 of FIG.
7. However, the switch 801 of FIG. 6 can provide an output signal
as a function of predetermined acceleration forces along two, three
or more axes of sensitivity of the switch 801. Additionally, the
switch 801 can have the same or different levels of sensitivity
(i.e., respond to different acceleration forces) along each axis of
sensitivity of the switch 801. The switch 801 includes a seismic
mass comprised of a hook-shaped arm member 804 rigidly coupled to a
housing 802 of the medical device and an electrically conductive
impact head 808 secured to the free end of the arm 804. The arm 804
is electrically conductive and is electrically coupled to an
electrical output 812.
[0065] The arm 804 is constructed of a material that allows for
resilient deflection, and due to its hook shape, is adapted for
deflection along a plurality of imaginary lines of motion in three
dimensions. For example, the arm 804 can be constructed of
stainless steel, beryllium copper, or other materials having the
desired resiliency and electrical conductivity. Alternatively, the
arm can be made of nonconductive material having the desired
resiliency, such as plastic, and a flexible wire having the desired
electrical conductivity can be integrated with the arm. Each of the
imaginary lines of motion defines an imaginary plane. Thus, a
plurality of imaginary planes are defined, some of which have a
relationship other than being parallel to one another, including
planes that are generally orthogonal to one another in three
dimensions. In the illustrated embodiment, the arm 804 has a hook
or bend with a curvature of approximately 90 degrees. In other
embodiments, the curvature may be less or more than 90 degrees,
such as, for example, a curvature of between 45 degrees and 135
degrees.
[0066] Five electrically conductive contact surfaces 806a-806e are
fixedly mounted to form a conductive, generally box-shaped
enclosure 806 having an open end. The enclosure 806 generally
surrounds both the impact head 808 as well as a portion of the free
end of the arm 804. All of the contact surfaces 806a-806e are
electrically coupled to an electrical input 810. The impact head
808 is in a spaced apart relationship with each of the surfaces
806a-806e when no acceleration force acts on the medical
device.
[0067] When an acceleration force of a predetermined magnitude and
direction acts on the medical device, the arm 804 deflects and the
impact head 808 briefly touches one of the contact surfaces
806a-806e before returning to the equilibrium position. When this
occurs, the electrical circuit between the electrical input 810 and
the electrical output 812 is momentarily completed, thus producing
a voltage spike or pulse at the electrical output 812. System
electronics monitor the output 812 for such a voltage pulse, and
provide an appropriate alarm or other indication as described above
when such a pulse is detected.
[0068] Although the embodiment of FIG. 6 involves five generally
planar-shaped contact surfaces that form a generally box-shaped
enclosure, other embodiments may include a greater or lesser number
of contact surfaces having different shapes that may or may not
form an enclosure. For example, one embodiment may include only two
planar-shaped contact surfaces that are oriented generally
orthogonal to one another. On the other hand, other embodiments may
include a plurality of contact surfaces that form any
polyhedron-shaped enclosure having geometries other than the
box-shaped enclosure of FIG. 6 or that form a spherical or
cylindrical-shaped enclosure.
[0069] With respect to the embodiments of both FIGS. 6 and 7,
various impact acceleration set points can be established by
varying the length of the arm 804 or 902, the curvature of the bend
in the arm 804 in FIG. 6, the cross-sectional shape of the arm 804
or 902, the material from which the arm 804 or 902 is constructed,
the density of the material from which the impact head 808 or 906
is constructed, and the distance between the impact head 808 or 906
and the contact surface 806a-e or 908 and 910 at equilibrium (i.e.
when no acceleration force is being applied to the switch 801 or
901). In other alternative embodiments, the impact head 808 or 906
may be omitted, and the arm 804 or 902 may come into contact with
the contact surfaces 806a-e or 908 and 910 to close the electrical
circuit and produce an output signal at the electrical output 812
or 912.
[0070] As described above, an acceleration sensor such as an
accelerometer or impact switch may be used to detect and report
potential damage to an ambulatory medical device due to shock or
impact. Additionally, an accelerometer can be used to detect
physical activities of the user, and then the user's therapy can be
adjusted or operation of the medical device can otherwise be
altered in response to the detected activity of the user, as will
be described below.
[0071] The accelerometers described above can be carried or worn by
individuals to monitor their physical activities, including
exercise. Such physical activity generally results in an
accelerometer frequency output in the range of 10-60 Hz, up to 100
Hz. Typically, each type of physical activity in which the user
engages (e.g., running, walking, sitting, etc.) generates a
different frequency that can be detected and identified. Thus, in
other embodiments of the present invention, an ambulatory medical
device such as the external infusion pump 410 may include an
acceleration sensor 414 such as one or more accelerometers that
provide signals as a function of a plurality of acceleration forces
acting on the pump 410 and corresponding to physical activity of
the user. In one embodiment, the pump 410 may determine that the
user is engaging in physical activity if the output signal of the
acceleration sensor 414 exceeds a predetermined acceleration force
that is known to correspond to such physical activity. In other
embodiments, the pump 410 may determine that the user is engaging
in physical activity based on a trace or pattern of output signals
from the acceleration sensor 414. For example, running may result
in one trace or pattern of varying magnitudes of output signals
from the acceleration sensor 414, while walking may result in
another trace or pattern of varying magnitudes of output signals
from the acceleration sensor 414. The pump monitors the physical
activity of the user and responds accordingly by providing messages
or alarms to the user (i.e., visually on the display 428, audibly
by the speaker 430, and/or tactilely via the vibration alarm 416),
adjusting the delivery of medication to the user, or otherwise
altering the operation of the pump 410.
[0072] For example, some users require less medication, such as
insulin, during periods of intense exercise and/or for certain
periods of time after such exercise. The acceleration sensor 414
incorporated into the pump 410 may be used to detect such exercise
or other physical activity by the user. In response to the detected
exercise or physical activity, the pump 410 can notify the user to
decrease the medication delivery rate. In alternative embodiments,
the pump 410 can automatically decrease the medication delivery
rate. Moreover, the pump 410 can apply a time delay between
detecting the commencement of exercise and decreasing the
medication delivery rate. The time delay may be a predetermined
period of time for the pump 410 (e.g., 5 minutes), or
alternatively, the user may program the length of the delay.
Furthermore, the pump 410 may vary the length of the delay based on
the duration and/or intensity of the exercise. In still other
embodiments, the pump 410 may change the nocturnal delivery rate
(i.e., the delivery rate when the user is sleeping) in response to
detected exercise earlier in the day.
[0073] In particular embodiments, the pump 410 allows the user to
program the amount of decrease in the medication delivery rate
during and/or after the period of exercise. For example, the user
can enter a percentage decrease of the current delivery rate to be
used when exercise is detected. Alternatively, the user can set a
specified delivery rate to be used when exercise is detected. The
delivery rate during and/or after exercise may be any rate that is
lower than the delivery rate used when not exercising, including no
medication delivery during exercise.
[0074] In other embodiments, the pump 410 may correlate the
detected duration and intensity of physical activity to caloric
burn. This correlation may be performed utilizing known algorithms
and data correlating exercise to caloric burn that are
preprogrammed into the pump 410 and/or input into the pump 410 by
the user or caregiver. Based on the estimated caloric burn, the
pump 410 may notify the user of possible hypoglycemia if the
caloric burn is high, or alternatively, suggest more exercise for
the user if the caloric burn is low. The pump 410 may also modify
the medication delivery rate based on the estimated caloric burn.
For example, the pump 410 may decrease the medication delivery rate
if the caloric burn is high.
[0075] In alternative embodiments, the pump 410 may deliver
medications or fluids other than insulin. As a result, in some
embodiments, the user may desire more medication or other fluids
during exercise. Thus, in response to the detected exercise or
physical activity by the user, the delivery rate may be increased
in a manner similar to that described above for decreasing the
delivery rate. For example, the pump may deliver medications or
other fluids such as nutrients, vitamins, minerals, steroids,
anabolic drugs, glucose, salts, sources of energy, painkillers,
drugs to enhance oxygen uptake, fluids for hydration, or the
like.
[0076] In particular embodiments, the acceleration sensor 414
incorporated into the pump 410 may also be used to detect the
cessation of exercise or physical activity by the user. In response
to the detected cessation of exercise or physical activity, the
pump 410 can remind the user to return to the normal, programmed
delivery rate. In alternative embodiments, the pump 410 can
automatically return to the normal, programmed delivery rate.
Additionally, the pump may apply a time delay between detecting the
cessation of exercise and returning to the normal, programmed
delivery rate.
[0077] For some users, the length of the delay between ending
exercise and returning to the normal, programmed delivery rate may
be dependent on the duration of the exercise. For example, if the
user has exercised for 30 minutes or less, the pump 410 may delay
for a period of 5 minutes after the user has stopped exercising,
and then return to the normal, programmed delivery rate. In another
example, if the user has exercised for more than 30 minutes, the
pump 410 may delay for a period of 10 minutes after the user has
stopped exercising, and then return to the normal, programmed
delivery rate. Other time periods of delay or exercise may be used.
In alternative embodiments, the user may program the length of the
delay between detecting the cessation of exercise and returning to
the normal, programmed delivery rate.
[0078] In further alternative embodiments, the pump 410 may change
the delivery rate gradually from the normal programmed delivery
rate to the exercise delivery rate, and from the exercise delivery
rate to the normal programmed delivery rate. These gradual changes
in rates or dosages can occur over a period of time in a generally
linear manner, a generally quadratic manner, a generally
exponential manner, or a generally logarithmic manner.
[0079] In other embodiments, exercise characteristics, such as
frequency, duration, and/or intensity, may be detected by the
acceleration sensor 414 incorporated into the ambulatory medical
device such as the infusion pump 410, and then stored in a history
file or database. In one embodiment, the exercise characteristics
may be downloaded from the transmitter/receiver 417 via a wired or
wireless connection to a computer, PDA, the Internet, or the like,
where an exercise history file or database is maintained.
Alternatively, the exercise history file may be stored and
maintained in the memory 422 of the pump 410. The history file is
analyzed to determine if the user's exercise routine has changed,
and if so, the user is notified to re-evaluate his or her
medication delivery rate.
[0080] For example, some users may require more or less medication,
such as insulin, depending on their exercise routine. For users who
have significantly increased their exercise routine and improved
their physical conditioning, the amount of insulin required per
gram of carbohydrate ingested (i.e., carbohydrate ratio) and/or the
amount of insulin required to lower their blood glucose level a
certain number of units (i.e., insulin sensitivity) may decrease.
On the other hand, for users who have significantly decreased their
exercise routine and lost some physical conditioning, the amount of
insulin required per gram of carbohydrate ingested (i.e.,
carbohydrate ratio) and/or the amount of insulin required to lower
their blood glucose level a certain number of units (i.e., insulin
sensitivity) may increase.
[0081] In some embodiments, the user may be notified when his or
her exercise routine has changed throughout a period of three
months. Alternatively, users can be notified when their exercise
routine has changed for longer or shorter periods of time. For
example, some users with diabetes may require a different amount of
insulin when they are ill compared to when they are healthy. Thus,
if such a user is ill and cannot exercise, then after just 2 or 3
days, the pump can notify the user to re-evaluate his/her
carbohydrate ratio and/or insulin sensitivity.
[0082] In particular embodiments, the exercise history file may be
maintained and analyzed on a device other than the pump 410, such
as a computer, PDA, the Internet, or the like. The user may then be
notified that his/her exercise routine has changed and/or to
re-evaluate his/her medication delivery rate by email, while
operating a computer program, while communicating with a web site,
or the like. Alternatively, the user can receive this notification
from the user's glucose meter or monitoring system, PDA, cell
phone, or the like. In further alternative embodiments, this
notification can be transmitted to the transmitter/receiver 417,
and then provided to the user by the pump 410 visually on the
display 428, audibly by the audible alarm 430, and/or tactilely via
the vibration alarm 416. In other embodiments, the exercise history
file may be maintained and analyzed on the pump 410. The pump 410
then notifies the user that the user's exercise routine has changed
and/or to re-evaluate the user's medication delivery rate visually
on the display 428, audibly by the audible alarm 430, and/or
tactilely via the vibration alarm 416. In alternative embodiments,
the transmitter/receiver 417 may be utilized to communicate this
notification to a device other than the infusion pump 410 so that
the user can receive this notification as described above, such as
by email, while operating a computer program, while communicating
with a web site, or the like. Alternatively, the user can receive
this notification from the user's glucose meter or monitoring
system, PDA, cell phone, or the like.
[0083] In further alternative embodiments, sensing devices other
than an acceleration sensor 414 incorporated into the infusion pump
410 may be used to detect exercise, such as for example, a
respiratory rate measuring device, a blood glucose monitor, a heart
rate measurement device, a blood oxygen sensor, a body temperature
sensor, or the like. These sensing devices can communicate with the
pump 410 via the transmitter/receiver 417, and the pump 410 can
maintain and analyze the exercise history file and/or modify the
medication delivery rate. In other alternative embodiments, these
sensing devices can communicate with a device external to the pump
410 (e.g., computer, PDA, the Internet), which stores and analyzes
the exercise history file. If the pump 410 or device external to
the pump 410 (e.g., computer, PDA, the Internet) determines that
the user's exercise routine has changed, the user can be notified
of such change and/or to re-evaluate his/her medication delivery
rate by the pump 410 or other external device as described
above.
[0084] In addition to acceleration, other environmental conditions
can adversely affect the performance of ambulatory medical devices
such as the infusion pump 410. For example, temperature extremes
can affect both performance of the infusion pump 410 as well as
certain medications, such as insulin. Thus, an ambulatory medical
device such as the infusion pump 410 may also include a temperature
or thermal sensor 426, which allows the pump 410 to notify the user
when the pump 410 is exposed to varying or extreme temperatures
(hot or cold). Temperature sensing can be used, for example, to
estimate the effect of temperature on the performance of the pump
410 itself, the pump's power supply 440 such as a battery, and/or
degradation of insulin or other medication. The thermal sensor 426
may be any of the known thermal sensors, including, for example,
thermoresistors (thermistors), thermocouples, thermal flow rate
sensors, resistance temperature detectors ("RTDs"), platinum
resistors, diode temperature sensors, silicon transistor
thermometers, integrated temperature transducers, PTAT circuits,
thermopiles, pyroelectric thermometers, quartz thermometers, and
the like.
[0085] RTD's operate on the principle that the electrical
resistance of many metals, such as platinum, aluminum and copper,
or the like will increase over a certain range of temperatures. A
fine wire of metal is wound on a core to obtain a high level of
resistance or is patterned as a thin film on a substrate. The
varying resistance is then measured as a function of
temperature.
[0086] A thermistor sensor also operates on the principle of
varying electrical resistances as a function of temperature.
However, these devices are made from various nonmetallic conductors
(e.g., metal oxides and silicon) and can offer the advantage of
higher thermal coefficients of resistance and greater sensitivities
(.DELTA.R/.DELTA.T). Moreover, some types of thermistors provide
increasing electrical resistance as temperature increases, whereas
other types provide decreasing resistance.
[0087] A thermocouple sensor consists of two dissimilar metals that
are bonded together by welding or other means. The bimetallic
junction develops a small voltage that varies with temperature.
Thermocouples are relatively inexpensive and provide moderately
accurate and consistent measurements. However, one disadvantage is
that they produce very small output voltages which are comparable
to the voltages developed at the junctions formed where the
thermocouple wire is connected to other components. This must be
compensated for in the associated circuitry.
[0088] Many temperature sensor integrated circuit devices operate
on the principle that at a constant current bias, the voltage drop
across a silicon P-N diode junction can vary with temperature.
Because the P-N junction is the basic building block of diodes,
transistors, and ICs, temperature sensing can be incorporated at a
relatively low cost.
[0089] There are various uses for a temperature or thermal sensor
426 in an ambulatory medical device such as the infusion pump 410.
In one embodiment, the infusion pump 410 uses the temperature
sensor 426 for warning purposes. In extreme environments,
medication such as insulin can degrade and become less effective.
Also, electronic components of the pump 410 may malfunction (e.g.,
the display 428 may go blank). The thermal sensor 426 is used to
measure or detect temperature conditions to which the pump 410 is
subjected, and in response to the detected temperature, the pump
410 can notify the user of potential problems due to the
temperature before they occur (e.g., insulin degradation,
electronics malfunction). Additionally, if the thermal sensor 426
detects a sufficiently high or low temperature, problems such as
insulin degradation may have already occurred. Thus, the pump 410
can provide the user with an alarm to notify the user of the
insulin degradation.
[0090] In operation, the thermal sensor 426 provides an output
signal as a function of the temperature in the housing 420. The
processor 418 converts the output signal to a value, and compares
that value with a predetermined temperature value stored in the
memory 422 that is associated with a predetermined temperature. If
the temperature measured by the thermal sensor 426 exceeds the
predetermined temperature, the processor 418 may provide an alarm
to the user (i.e., tactilely via the vibration alarm 416, audibly
by the audible alarm 430, and/or visually on the display 428) to
indicate that the pump 410 has been subjected to extremely high
temperatures, and as a result, to check the pump (e.g., whether
insulin degradation has occurred, the display has
malfunctioned).
[0091] Additionally, in cold environments, there may be a higher
occurrence of medication flow stoppage due to the reduced viscosity
of some medications such as insulin. The lower viscosity fluid
requires a higher force to deliver the fluid from the reservoir,
through the tubing, and into the infusion set adhered to the
patient. However, this higher delivery force can be more likely to
trigger a false occlusion alarm as compared with pump operations at
warmer temperatures. Accordingly, in another embodiment of the
present invention, for an ambulatory medical device such as the
infusion pump 301 which utilizes a force sensor 311 to detect
occlusions, the programmed occlusion alarm limits are made
dependent on the measured temperatures to which the pump 301 is
subjected. When the temperature decreases, the pump occlusion alarm
limit is increased accordingly.
[0092] In operation, the memory 422 stores a predetermined
temperature value associated with a predetermined temperature and a
predetermined force threshold value associated with a predetermined
force threshold corresponding to a fluid occlusion. The thermal
sensor 426 provides an output signal as a function of the
temperature in the housing 420. The processor 418 converts the
output signal to a value, and compares that value with the
predetermined temperature value. If the temperature measured by the
thermal sensor 426 is less than the predetermined temperature, the
processor 418 alters the predetermined force threshold value to
provide a modified force threshold value. In other words, the force
threshold corresponding to an occlusion is changed. Subsequently,
if a measured force (as measured, for example, by the force sensor
311) exceeds the modified force threshold value, the processor 418
provides an alarm to the user (i.e., visually on the display 428,
audibly by the audible alarm 430, and/or tactilely via the
vibration alarm 416) to indicate the occlusion.
[0093] In other embodiments, temperature data is used to modify a
delivery pulse of the pump. For example, in some ambulatory medical
devices such as the infusion pump 410, friction within the drive
mechanism 432 and/or reservoir 434 is often dependent on the
temperature at which the pump 410 is operating. As temperature
decreases, friction increases, and as a result, more energy is
required by the drive mechanism 432 to deliver fluid out of the
reservoir 434. Therefore, the thermal sensor 426 can measure the
temperature within the pump housing 420. The processor 418 compares
the measured temperature with a predetermined temperature stored in
the memory 422. If the measured temperature is below the
predetermined temperature, the processor 418 increases the delivery
pulse, for example, by increasing the duration or the amount of
energy in the delivery pulse.
[0094] In yet another embodiment, temperature data is used as an
indicator of reduced battery life. For example, in some ambulatory
medical devices such as the infusion pump 410, alkaline-manganese
dioxide batteries can be used as the power supply 440. Battery
performance is often dependent on the temperature at which the
battery is operating. As temperature decreases, the discharge
resistance of the battery increases, thereby reducing the battery's
life. Therefore, the thermal sensor 426 can measure the temperature
within the pump housing 420. The processor 418 compares the
measured temperature with a predetermined temperature stored in the
memory 422. For example, the predetermined temperature may be a
temperature that causes a battery discharge resistance increase of
10, 15, 25, 50 percent or some other percentage. If the measured
temperature is below the predetermined temperature, the pump 410
provides an alarm to the user, indicating that battery life may be
reduced due to the temperature to which the pump 410 is
subjected.
[0095] Additionally, in other embodiments, an ambulatory medical
device such as the infusion pump 410 uses temperature data to
modify battery measurement algorithms. In one embodiment, when the
temperature decreases, the measurement frequency of the power
supply 440 such as the battery may be increased to ensure that
there is adequate power for effective operation of the pump 410.
For example, in the infusion pump 410, a battery measurement may be
taken every hour. Since the act of taking this measurement requires
power, it can be important to minimize the frequency of battery
measurements. On the other hand, if there are external conditions
that effectively reduce the battery performance, such as lower
temperatures, it may be desirable to modify the pump 410 to take
battery measurements differently, possibly more frequently, so that
appropriate low battery and dead battery conditions can be detected
earlier than otherwise.
[0096] Thus, the processor 418 samples the output voltage of the
battery 440 at a first sampling frequency. The thermal sensor 426
provides an output signal as a function of the temperature in the
housing 420. The processor 418 converts the output signal to a
value and compares that value with a predetermined temperature
value stored in the memory 422 corresponding to a predetermined
temperature. If the temperature measured by the thermal sensor 426
is less than the predetermined temperature, the processor 418
alters the battery voltage sampling from the first sampling
frequency to a second sampling frequency in accordance with this
comparison.
[0097] Humidity is yet another environmental variable that can
affect performance of an ambulatory medical device such as the
infusion pump 410. In one embodiment, the humidity sensor 412 is
incorporated within the infusion pump 410, and provides an output
signal as a function of humidity levels in the housing 420.
Alternatively, the humidity sensor 412 can be disposed to provide
an output signal as a function of humidity levels external to the
housing 420.
[0098] The processor 418 converts the output signal from the
humidity sensor to a value, and compares that value with a
predetermined value stored in the memory 422 that is associated
with a predetermined humidity level. Based on the comparison, the
processor 418 then provides a warning or alarm to the user (i.e.,
visually on the display 428, audibly by the audible alarm 430,
and/or tactilely via the vibration alarm 416). The humidity sensor
412 may be any of the known humidity sensors, including capacitive
humidity sensors, resistive humidity sensors, and thermal
conductivity humidity sensors.
[0099] Capacitive humidity sensors consist of a substrate on which
a thin film of polymer or metal oxide is deposited between two
conductive electrodes. The sensing surface is coated with a porous
metal electrode to protect it from contamination and exposure to
condensation. The change in the dielectric constant of a capacitive
humidity sensor is proportional to the relative humidity of the
surrounding environment.
[0100] Resistive humidity sensors measure the change in electrical
impedance of a hygroscopic medium such as a conductive polymer,
salt, or treated substrate. The impedance change is typically
inversely proportional to the humidity level. Resistive sensors
frequently consist of noble metal electrodes deposited on a
substrate. The substrate can be coated with a salt or conductive
polymer. When it is dissolved or suspended in a liquid binder, it
functions as a vehicle to evenly coat the sensor.
[0101] Thermal conductivity humidity sensors measure the absolute
humidity by quantifying the difference in the thermal conductivity
between dry air and air containing water vapor. They usually
consist of two thermistor elements in a bridge circuit--one is
encapsulated in a gas, such as dry nitrogen, and the other is
exposed to the environment. When current is passed through the
thermistors, resistive heating increases their temperature. The
heat dissipated from the encapsulated thermistor is greater than
the exposed thermistor due to the difference in the thermal
conductivity of the water vapor as compared to dry nitrogen. Since
the heat dissipated yields different operating temperatures, the
difference in resistance of the thermistors is proportional to the
humidity.
[0102] In particular embodiments, humidity measurements from within
an ambulatory medical device such as the infusion pump 410 are used
to detect a breach in the pump's watertight integrity. The humidity
sensor 412 may measure the humidity level within the housing 420 of
the pump 410, and the processor 418 may compare the measured
humidity with a predetermined humidity level stored in the memory
422. For example, the predetermined humidity level may be a very
high humidity level (e.g., greater than 90%, 80%, or some other
percentage) within the housing 420 of the pump 410 that may
indicate possible water intrusion into the pump 410 due to a
damaged housing 420. If the measured humidity exceeds the
predetermined humidity level, the pump 410 notifies the user and
indicates the necessity to perform some self-test or investigation,
or to contact the manufacturer for service. This notification can
be provided tactilely via the vibration alarm 416, audibly by the
audible alarm 430, and/or visually on the display 428.
Alternatively, the processor 418 can activate the
transmitter/receiver 417, which can send the humidity level
information to an external device for analysis or notification to
the user.
[0103] Although some ambulatory medical devices are designed to be
resistant to the effects of static electricity, it nevertheless is
possible that high levels of static discharge can cause such a
device to alarm. A significant environmental parameter affecting
the generation of static electricity is humidity. The effects of
static electricity increase with a decrease in humidity. Therefore,
in another embodiment, the humidity sensor 412 in an ambulatory
medical device such as the infusion pump 410 can measure humidity
external to the pump 410, and the user can then be notified of high
humidity conditions. Alternatively, humidity measured by the
humidity sensor 412 from within the pump 410 can also be used.
[0104] However, there likely will be a time lag between a change in
external humidity and the detection of such a change by the
humidity sensor 412 that measures internal humidity.
[0105] Thus, there is disclosed an ambulatory medical device that
is adapted for carrying by a person, preferably by external
attachment to the person's body. The ambulatory medical device has
acceleration, thermal and/or humidity sensors which, along with
system electronics, control the device by, among other things,
altering the operation of the device, providing an alarm or text
message to the user, and/or transmitting data to another
device.
[0106] While the description above refers to particular embodiments
of the present invention, it will be understood that many
modifications may be made without departing from the spirit
thereof. The claims are intended to cover such modifications as
would fall within the true scope and spirit of the present
invention. The presently disclosed embodiments are therefore to be
considered in all respects as illustrative and not restrictive, the
scope of the invention being indicated by the claims rather than
the foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are therefore
intended to be embraced therein.
* * * * *