U.S. patent application number 11/316198 was filed with the patent office on 2008-01-03 for defibrillator with implantable medical device detection.
This patent application is currently assigned to Medtronic Emergency Response Systems, Inc.. Invention is credited to David J. Jorgenson.
Application Number | 20080004663 11/316198 |
Document ID | / |
Family ID | 38068772 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080004663 |
Kind Code |
A1 |
Jorgenson; David J. |
January 3, 2008 |
Defibrillator with implantable medical device detection
Abstract
In general, the invention is directed to techniques for using an
external defibrillator to detect a presence of an implantable
medical device (IMD) implanted within a patient, and providing
therapy to the patient through communication between the external
defibrillator and the IMD. An external defibrillator provides
prompts to a user of the external defibrillator to determine the
presence of an IMD implanted within the patient. For example, the
external defibrillator may prompt the user to visually inspect the
patient's chest for signs that an IMD was implanted, such as a scar
or raised portion of skin near the patient's clavicles. As another
example, the external defibrillator may prompt the user to place a
detection device on the patient's chest. The detection device may
be coupled to the external defibrillator, and may employ a magnet
to initiate telemetry by the IMD to detect the presence of the
IMD.
Inventors: |
Jorgenson; David J.;
(Bloomington, MN) |
Correspondence
Address: |
SHUMAKER & SIEFFERT, P.A.
Suite 300
1625 Radio Drive
Woodbury
MN
55125
US
|
Assignee: |
Medtronic Emergency Response
Systems, Inc.
Redmond
WA
|
Family ID: |
38068772 |
Appl. No.: |
11/316198 |
Filed: |
December 22, 2005 |
Current U.S.
Class: |
607/5 ; 128/899;
607/32 |
Current CPC
Class: |
A61N 1/36142 20130101;
G09B 23/28 20130101; G09B 23/288 20130101; A61N 1/37211 20130101;
A61N 1/39044 20170801; A61N 1/3925 20130101; A61N 1/3993 20130101;
A61N 1/3904 20170801; A61N 1/3605 20130101; A61N 1/37247
20130101 |
Class at
Publication: |
607/005 ;
128/899; 607/032 |
International
Class: |
A61N 1/00 20060101
A61N001/00; A61B 19/00 20060101 A61B019/00 |
Claims
1. An external defibrillator comprising: a defibrillation therapy
generator; electrodes coupled to the defibrillation therapy
generator; and a user interface that presents one or more prompts
to a user of the external defibrillator to detect presence of an
implantable medical device (IMD) in a patient.
2. The external defibrillator of claim 1, wherein the user
interface presents a prompt requesting that the user examine an
area of the body of the patient for evidence of presence of an IMD
in the patient.
3. The external defibrillator of claim 1, wherein the user
interface presents: a first prompt requesting that the user examine
a chest of the patient for a scar near clavicles of the patient; a
second prompt requesting that the user examine the chest of the
patient for a raised portion of skin near the clavicles of the
patient; a third prompt requesting that the user place a detection
device on the chest of the patient near the clavicles of the
patient; and a fourth prompt requesting that the user place the
electrodes on the patient's chest based on the location of the
IMD.
4. The external defibrillator of claim 1, wherein the prompts
include at least one of audible prompts or visual prompts, the
external defibrillator including a device to present at least one
of the audible prompts or visual prompts.
5. The external defibrillator of claim 1, wherein the user
interface provides a medium for user input indicating that the user
has detected presence of the IMD.
6. The external defibrillator of claim 1, further comprising a
detection device that detects presence of the IMD, wherein the
detection device is configured to trigger initiation of telemetry
by the IMD and detect the presence of the IMD based on reception of
one or more telemetry signals from the IMD.
7. The external defibrillator of claim 6, further comprising a
processor that receives information from the IMD via the telemetry
signals, wherein the processor controls the therapy generator to
deliver therapy to the patient based on the received
information.
8. The external defibrillator of claim 7, wherein the received
information includes electrogram information, electrocardiogram
information, and IMD event information.
9. A method comprising generating one or more prompts to a user of
an external defibrillator to detect presence of an implantable
medical device (IMD) in a patient.
10. The method of claim 9, further comprising presenting a prompt
requesting that the user examine an area of the body of the patient
for evidence of presence of the IMD in the patient.
11. The method of claim 9, further comprising generating: a first
prompt requesting that the user examine a chest of the patient for
a scar near clavicles of the patient; a second prompt requesting
that the user examine the chest of the patient for a raised portion
of skin near the clavicles of the patient; a third prompt
requesting that the user place a detection device of the external
defibrillator on the chest of the patient near the clavicles of the
patient; and a fourth prompt requesting that the user place
electrodes of the external defibrillator on the patient's chest
based on the location of the IMD.
12. The method of claim 9, wherein generating one or more prompts
includes generating at least one of audible prompts or visual
prompts.
13. The method of claim 9, wherein detecting presence of an IMD in
the patient comprises triggering initiation of telemetry by the IMD
and detecting the presence of the IMD based on reception of one or
more telemetry signals from the IMD.
14. The method of claim 13, further comprising: receiving
information from the IMD via the telemetry signals; and delivering
therapy to the patient based on the received information.
15. The method of claim 14, wherein the received information
includes electrogram information, electrocardiogram information,
and IMD event information.
16. An external-defibrillator comprising: a defibrillation therapy
generator; electrodes coupled to the defibrillation therapy
generator; and a detection device that detects presence of an
implantable medical device (IMD) in a patient.
17. The external defibrillator of claim 16, further comprising an
output medium that indicates presence of the IMD.
18. The external defibrillator of claim 17, wherein the output
medium provides at least one of a visual indication or an audible
indication of presence of the IMD.
19. The external defibrillator of claim 16, wherein the detection
device is configured to trigger initiation of telemetry by the IMD
and detect the presence of the IMD based on reception of one or
more telemetry signals from the IMD.
20. The external defibrillator of claim 16, wherein the detection
device includes a magnet to trigger initiation of telemetry by the
IMD.
21. The external defibrillator of claim 20, further comprising a
processor that receives information from the IMD via the telemetry
signals, wherein the processor controls the therapy generator to
deliver therapy to the patient based on the received
information.
22. The external defibrillator of claim 21, wherein the received
information includes electrogram information, electrocardiogram
information, and IMD event information.
23. The external defibrillator of claim 22, wherein the received
information comprises patient information and IMD information.
24. A method comprising: detecting presence of an implantable
medical device (IMD) in a patient via a detection device associated
with an external defibrillator; and indicating presence of the IMD
to a user of the external defibrillator.
25. The method of claim 24, wherein indicating the presence of the
IMD comprises indicating the presence of the IMD via at least one
of an audible indication or a visual indication.
26. The method of claim 24, further comprising: placing the
detection device near the IMD, wherein the detection device
includes a magnet to trigger initiation of telemetry by the IMD;
and communicating with the IMD via a telemetry device, wherein the
telemetry device is integrated with the detection device.
27. The method of claim 26, further comprising: receiving
information from the IMD via the telemetry device; and delivering
therapy to the patient based on the received information.
28. The external defibrillator of claim 27, wherein the received
information includes electrogram information, electrocardiogram
information, and IMD event information.
Description
TECHNICAL FIELD
[0001] The invention relates to emergency medical devices and, more
particularly, to external defibrillators.
BACKGROUND
[0002] An external defibrillator delivers energy to a heart of a
patient via electrodes placed upon the patient's chest. External
defibrillators are used to deliver energy in the form of a
defibrillation shock to a heart that is undergoing ventricular
fibrillation and has lost its ability to contract. Ventricular
fibrillation is particularly life threatening because activity
within the ventricles of the heart is so uncoordinated that
virtually no pumping of blood takes place. If untreated, a patient
suffering from fibrillation may die within a matter of minutes.
[0003] An electric shock delivered to a fibrillating heart may
depolarize the heart and cause it to reestablish a normal sinus
rhythm. In some cases, the patient may need multiple shocks, and
the external defibrillator may deliver different quantities of
energy with each defibrillation shock. Further, the defibrillator
may provide additional or alternative therapies to the patient,
such as cardioversion or pacing therapy. As examples, the external
defibrillator may be an automated external defibrillator (AED) used
by a first responder or bystander to treat the patient, or a more
fully-featured defibrillator/monitor used by paramedics.
SUMMARY
[0004] In general, the invention is directed to an external
defibrillator equipped to aid a user in detecting the presence of
an implantable medical device (IMD) within a patient. Upon
detection of an IMD, the external defibrillator may communicate
with the IMD to obtain useful information or coordinate delivery of
therapy to the patient. As examples, the external defibrillator may
receive patient or therapy information from the IMD, prompt a user
based on information received from the IMD, deliver therapy based
on information received from the IMD, control delivery of therapy
by the IMD, and store information within the IMD. Alternatively, or
additionally, detection of IMD location may permit the user to
place defibrillation electrodes in a location which will reduce the
chance of damage to the IMD while still providing effective
defibrillation therapy to the patient.
[0005] The external defibrillator may provide prompts to guide a
user of the external defibrillator in detecting the presence of an
IMD implanted within the patient. For example, the external
defibrillator may prompt the user to visually inspect the patient's
chest for signs that an IMD was implanted, such as a scar or raised
portion of skin near the patient's clavicles. As another example,
the external defibrillator may prompt the user to place a detection
device on the patient's chest. The detection device may be coupled
to the external defibrillator, and may employ a detector to locate
an IMD. When an IMD is detected, the external defibrillator or
detection device may emit a notification. For example, the
detection device may have an audible or visual indicator that
assists the user in positioning the detection device.
[0006] The external defibrillator may obtain information from a
detected IMD or coordinate delivery of therapy with the IMD by
wireless telemetry. For example, the detection device may be
integrated with wireless telemetry circuitry to facilitate
communication with the IMD. In some embodiments, the detection
device may include an adhesive interface to permit adhesive
fixation of the detection device at the IMD location, thereby
promoting more reliable telemetry. The external defibrillator may
deliver therapy based on information received from the IMD in the
patient. The external defibrillator may select an energy level for
a defibrillation shock to be delivered to the patient based on an
energy level of a defibrillation shock previously delivered to the
patient by the IMD. As another example, the external defibrillator
may analyze an electrogram (EGM) or electrocardiogram (ECG), or
output received from the IMD indicating pace, shock or sense
events, to determine whether to deliver a defibrillation shock to
the patient.
[0007] In one embodiment, the invention provides an external
defibrillator comprising a defibrillation therapy generator,
electrodes coupled to the defibrillation therapy generator, and a
user interface that presents one or more prompts to a user of the
external defibrillator to detect presence of an implantable medical
device (IMD) in a patient.
[0008] In another embodiment, the invention provides a method
comprising generating one or more prompts to a user of an external
defibrillator to detect presence of an implantable medical device
(IMD) in a patient.
[0009] In an additional embodiment, the invention provides an
external defibrillator comprising a defibrillation therapy
generator, electrodes coupled to the defibrillation therapy
generator, and a detection device that detects presence of an
implantable medical device (IMD) in a patient.
[0010] In another embodiment, the invention provides a method
comprising detecting presence of an implantable medical device
(IMD) in a patient via a detection device associated with an
external defibrillator, and indicating presence of the IMD to a
user of the external defibrillator.
[0011] In various embodiments, the invention may provide one or
more advantages. For example, prompts delivered by an external
defibrillator may permit a user to more readily detect the presence
and location of an IMD. Upon detection of the IMD location, a user
can place defibrillation electrodes at a location which will reduce
the chance of damage to the IMD while still providing effective
defibrillation therapy to the patient. In addition, a detection
device may facilitate rapid detection of the IMD, which promotes
timely delivery of therapy. With the ability to communicate with a
detected IMD, an external defibrillator may provide more effective
treatment to a patient in which the IMD is implanted, permitting
coordinated delivery of therapy. In addition, by communication with
the IMD, the external defibrillator may more effectively obtain and
manage medical information such as patient information or therapy
information.
[0012] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 is a conceptual diagram illustrating an external
defibrillator providing a user prompt for locating an IMD implanted
within a patient.
[0014] FIG. 2 is a conceptual diagram illustrating an external
defibrillator providing a second user prompt for locating an IMD
implanted within a patient.
[0015] FIG. 3 is a conceptual diagram illustrating an external
defibrillator providing a third user prompt for locating an IMD
implanted within a patient.
[0016] FIG. 4 is a conceptual diagram illustrating an external
defibrillator providing a user prompt for placing defibrillation
electrodes on a patient.
[0017] FIG. 5 is a block diagram illustrating example components of
the external defibrillator of FIG. 1.
[0018] FIG. 6 is a flowchart illustrating exemplary operation of an
external defibrillator.
[0019] FIG. 7 is a block diagram illustrating example components of
an IMD detection device for use with the external defibrillator of
FIG. 1.
[0020] FIG. 8 is a block diagram illustrating an example IMD
detection device that includes an adhesive layer and a removable
backing layer.
[0021] FIG. 9 is a conceptual diagram illustrating an example
system that includes an external defibrillator communicating with
an IMD implanted within a patient.
DETAILED DESCRIPTION
[0022] FIG. 1 is a conceptual diagram illustrating an example
system 10 that includes an external defibrillator 12 providing a
user prompt 34 for locating an implantable medical device 14
implanted within a patient 16. External defibrillator 12 may be
brought to patient 16 in response to a medical emergency involving
patient 16, such as a ventricular fibrillation (VF) or sudden
cardiac arrest (SCA) experienced by the patient. External
defibrillator 12 may be, for example, an automated external
defibrillator (AED), or a more fully featured external
defibrillator/monitor, such as those used by paramedics or other
medical professional. However, the generation of user prompts may
be especially useful to a user of an AED. An AED provides basic
life support (BLS) services. A more fully featured external
defibrillator/monitor may provide advanced life support (ALS)
services.
[0023] In the illustrated example, external defibrillator 12 is
coupled to two electrodes 18A and 18B (collectively "electrodes
18") that are applied to the skin of patient 16. Electrodes 18 may
be electrodes pads, which may include an adhesive backing for
attachment to the skin of patient 16, as is known in the art.
Electrodes 18 are coupled to defibrillator 12 by respective leads
or cables 20A and 20B (collectively "cables 20"). Although
illustrated in FIG. 1 as coupled to two electrodes 18, external
defibrillator 12 may be coupled to any number of electrodes 18,
which may be incorporated into common electrode pads, and may share
common cables 20. External defibrillator 12 may additionally
include one or more sensors (not shown in FIG. 1), such as blood
oxygen saturation or noninvasive blood pressure sensors.
[0024] External defibrillator 12 detects electrical activity of the
heart 22 of patient 16 via electrodes 18, and delivers electrical
stimulation to heart 22 via electrodes 18. For example,
defibrillator 12 may deliver one or more defibrillation shocks to
patient 16 via electrodes 18. As shown in FIG. 1, defibrillator 12
may include a display 24, and may provide instructions in the form
of visual prompts and other information to a user via the display.
External defibrillator 12 may, for example, display an
electrocardiogram generated based on the electrical activity
detected by electrodes 18 via display 24. In some embodiments, as
mentioned above, defibrillator 12 may be coupled to additional
sensors for sensing other physiological parameters of patient 16,
such as blood pressure and oxygen saturation, and may display
current or average values for the additional parameters via display
24. External defibrillator 12 may also include a speaker 32 to
provide audible user prompts.
[0025] In the illustrated example, IMD 14 is a multi-chamber
cardiac pacemaker coupled to leads 26A-26C (collectively "leads
26") that extend to selected positions within heart 22, such as the
right atrium, right ventricle, and left ventricle. As an
alternative or in addition to pacing pulses, IMD 14 may deliver
cardioversion and/or defibrillation shocks to heart 22 via leads
26. Hence, IMD 14 may be an implantable cardioverter-defibrillator
(ICD), as is known in the art. Further, IMD 14 may sense electrical
activity of heart 22 via leads 26.
[0026] Leads 26 may include any of a variety of types of electrodes
(not shown) known in the art for use in sensing cardiac electrical
activity and delivering these types of stimulation to heart 22. The
number and positions of leads 26 depicted in FIG. 1 are merely
exemplary. Further, the invention is not limited to systems 10 in
which an IMD is a pacemaker. IMD 14 may be any type of IMD that
senses one or more physiological parameters of patient 16 and/or
delivers one or more therapies to the patient. For example, IMD 14
may be an implantable neurostimulator, muscle stimulator,
gastrointestinal stimulator, an implantable pump, or an implantable
monitor such as an implantable loop recorder.
[0027] In the example of FIG. 1, external defibrillator 12 provides
a user prompt 34 to aid a user in locating an IMD implanted within
patient 16. User prompt 34 may be an audible prompt provided via
speaker 32. Alternatively, user prompt 34 may be a visual prompt
such as a text prompt, pictorial prompt, or other visual prompt. In
some embodiments, defibrillator 12 may provide both audible and
visual prompts. External defibrillator 12 may prompt the user to
visually inspect an area of the patient's body, e.g., the patient's
chest or abdomen for signs that an IMD was implanted in patient 16.
Where the patient is a child, an IMD may be implanted in the
patient's abdomen. User prompt 34 prompts a user to look for a scar
near the patient's clavicle, i.e., collarbone. Such a scar may
indicate the presence of an IMD implanted within patient 16. Visual
and audible prompts may originate from external defibrillator 12 or
from a detection device 28, as will be described, in order to
facilitate optimal positioning of the detection device over the
patient.
[0028] External defibrillator 12 may include a user interface that
provides a medium for user input indicating whether the user has
found a scar near the patient's clavicle. As one example, display
24 may include interactive touchscreen displays in which the user
may push a button shown on display 24 to indicate responses to user
prompts. Other interface media such as buttons, switches, hardkeys
and softkeys may be used. Such interface media may additionally or
alternatively be located on detection device 28. In the case that
the user indicates he or she has found a scar near the patient's
clavicle, external defibrillator 12 may provide follow-up prompts
instructing the user to place detection device 28 on the patient's
chest near the scar, so that detection device 28 may establish
communication with IMD 14, as described in further detail
below.
[0029] In some embodiments, external defibrillator 12 is capable of
communicating with IMD 14 by wireless telemetry. External
defibrillator 12 communicates with IMD 14 via telemetry circuitry
similar to that used by dedicated programming devices to
communicate with the IMD. Dedicated programming devices may
communicate with IMD 14 via its telemetry circuitry to program or
reprogram the operating parameters of the IMD, or to retrieve
information stored or collected by the IMD, as is known in the art.
Like dedicated programming devices, external defibrillator 12 may
include corresponding telemetry circuitry to facilitate
communication with IMD 14 via its telemetry circuitry. The
telemetry circuitry of external defibrillator 12 and IMD 14 may
include suitable transceivers, magnets and antennas for
communication via radio-frequency (RF) telemetry.
[0030] In the example illustrated by FIG. 1, external defibrillator
12 is coupled to detection device 28 by cable 30. Cable 30 may
include conductors to carry both power and data to and from
detection device 28. Alternatively, in some embodiments, detection
device 28 may be battery-powered and communicate with external
defibrillator 12 by wireless telemetry. Detection device 28 is
placed proximate to, e.g., over, IMD 14 by a user of defibrillator
12 to enable the external defibrillator 12 to detect and optionally
communicate with the IMD. In addition to detecting the presence of
IMD 14 in patient 16, the detection device 28 may identify or
indicate a location of IMD 14 within the patient. In some
embodiments, detection device 28 also includes a telemetry device
having an antenna and magnet, enabling defibrillator 12 to
communicate with the IMD. Defibrillator 12 may be removably or
permanently coupled to detection device 28 by cable 30. In some
embodiments, detection device 28 may be integral with a housing of
external defibrillator 12, or incorporated into one of electrodes
18 and coupled to the external defibrillator by a lead 20. In other
embodiments, detection device 28 may not be coupled to
defibrillator 12 via cable 30, but may instead communicate with
defibrillator 12 via wireless communication, such as RF or infrared
communication.
[0031] Detection device 28 may include a magnet to open or close a
switch within IMD 14 and thereby initiate telemetry by the IMD. In
particular, by swiping detection device 28 across the patient's
body near a suspected implant site, the detection device triggers
wireless telemetry by IMD 14. Telemetry circuitry within detection
device 28 then may communicate with IMD 14 and/or measure signal
strength of telemetry signals transmitted by IMD 14 to guide the
user to place the detection device over the implant site of the
IMD. Visual and auditory prompts to guide placement of detection
device 28 to a position in proximity to the implant site may
originate from the detection device 28 or external defibrillator
12.
[0032] For example, detection device 28 may include a visual
indicator such as a series of lights. As detection device 28
approaches the implant site of IMD 14, a greater number of lights
are activated, thereby guiding placement of the detection device
toward the implant site. Alternatively, or additionally, an audible
indicator may be provided by detection device 28 or defibrillator
12. For example, the audible indicator may be a speaker that emits
an audible beep or pitch that increases in volume or frequency as
the detection device 28 approaches the implant site, or speech
output much like the prompts described above. The speaker may be
provided in detection device 28 or defibrillator 12. In each case,
the output of the visual or audible indicator is a function of the
measured signal strength of the telemetry signals emitted by IMD
14.
[0033] In another embodiment, detection device 28 detects the
presence of IMD 14 by inducing IMD 14 to initiate a specific pacing
protocol when the magnet is positioned near IMD 14. The frequency
and duration of the pacing may be measured by external
defibrillator 12 via electrodes 18. Magnet rate profiles are
different for different pacemaker and defibrillator manufacturers.
The change in pacing rate from before and after detection device 28
was applied would be interpreted by external defibrillator 12 as an
IMD. This information may allow external defibrillator 12 to
confirm when pacing was occurring and determine whether the patient
was in ventricular fibrillation and in need of therapy
[0034] In some embodiments, the telemetry circuitry and antennae of
external defibrillator 12 and IMD 14 may be configured to support a
signal strength, other signal characteristics, and communication
protocol that allow RF telemetry communication between the external
defibrillator and the IMD at relatively greater distances. In such
embodiments, one or more antennae of external defibrillator 12 may
be housed within the defibrillator. In this case, external
defibrillator 12 need not be coupled to detection device 28 to
communicate with the IMD, and defibrillator 12 may detect and
communicate with IMD when brought into general proximity with the
IMD.
[0035] FIG. 2 is a conceptual diagram illustrating external
defibrillator 12 in the course of providing another user prompt 40
to aid a user in locating an IMD 14 implanted within a patient 16.
Again, user prompt 40 may be a voice prompt provided via speaker
32, a visual prompt provided by display 24, or a combination of
both. In the example of FIG. 2, prompt 40 advises the user to
visually inspect the patient's chest for other signs that an IMD
has been implanted in patient 16. In particular, user prompt 34
prompts a user to look for a raised portion of the skin near
patient's collarbone. Such a raised portion of the skin may
indicate the presence of an IMD implanted within patient 16.
[0036] Prompt 40 may be provided if the user is unable to identify
a scar per prompt 34 of FIG. 1. Alternatively, prompt 40 may be
provided even if the user identifies a scar in order to aid the
user in more precisely identifying the position of IMD 14, which
may not be located immediately under the scar. In the case that the
user indicates he has found a scar near the patient's clavicle, or
found a raised portion of the skin near the patient's collarbone,
external defibrillator 12 may provide follow-up voice prompts
instructing the user to place detection device 28 on the patient's
chest near the scar, so that detection device 28 may verify the
presence of IMD 14 and/or establish communication with IMD 14 via
telemetry circuitry contained in detection device 28.
[0037] External defibrillator 12 may provide other voice prompts to
guide the user in determining whether an IMD is implanted within
patient 16. For example, external defibrillator 12 may prompt the
user to make a tactile search for an IMD by palpitating the
patient's chest at an area near the patient's clavicles to feel for
an IMD. In other words, the user manipulates the tissue near the
clavicles for tactile detection of the IMD, which should feel like
a hard object embedded within the tissue. As one example, tactile
detection may be done when the patient's size or weight is such
that an IMD is not readily visually detectable.
[0038] FIG. 3 is a conceptual diagram illustrating external
defibrillator 12 in the course of providing another user prompt 44
for locating an implantable medical device 14 implanted within a
patient 16. As one example, where a user has been prompted
according to FIGS. 1 and 2, but has been unable to visually locate
evidence of an IMD in patient 16, external defibrillator 12 may
prompt the user via user prompt 44 to place the detection device 28
near an area of the patient's body, e.g., the patient's chest near
the patient's clavicle, or the patient's abdomen where the patient
is a child.
[0039] Detection device 28 may use a magnetic, metal-detecting
feature to detect an IMD implanted within patient 16 in a manner
similar to a conventional magnetic stud finder. Alternatively,
detection device 28 may use another detection method such as an
acoustically-based detection method. Consequently, when the user
places detection device 28 on the patient's chest near a clavicle,
detection device 28 may detect the presence of an IMD implanted
within patient 16.
[0040] Detection device 28 may contain an output medium that
indicates to the user that the detection device has located an IMD,
such as LED lights, beeping, text alerts, or other indication
means. As another example, display 24 of external defibrillator 12
may display a message indicating that detection device 28 has
located an IMD. External defibrillator 12 may display a pictorial
indication of a location of IMD 14 within patient 16. Further,
detection device 28 may include telemetry circuitry for
communicating with IMD 14. In this embodiment, external
defibrillator 12 may display a message to indicate that external
defibrillator 12 has established communication with IMD 14.
[0041] FIG. 4 is a conceptual diagram illustrating an example
system 10 that includes an external defibrillator 12 providing a
user prompt 48 for placing electrodes 18 of the external
defibrillator 12 on a patient 16. As illustrated in FIG. 4,
detection device 28 has been placed on the chest of patient 16, and
is in communication with IMD 14. It may be undesirable for external
defibrillator electrodes to be placed directly over IMD 14, because
energy from electrodes 18 may electrically damage IMD 14.
Consequently, external defibrillator 12 prompts a user via user
prompt 48 to place the electrodes on the patient's chest, away from
the location of the IMD 14. By placing electrodes 18 at locations
some distance from the implant location of IMD 14, interference
between external defibrillator 12 and IMD 14 may be reduced.
Interference between external defibrillator 12 and IMD 14 may
include electromagnetic interference, which may degrade the signals
generated by sensors of IMD 14 and sensors of external
defibrillator 12.
[0042] FIG. 5 is a block diagram further illustrating exemplary
components of external defibrillator 12. In FIG. 5, external
defibrillator 12 is shown coupled to patient 16 by electrodes 18
and corresponding cables 20, as described above. In a typical
application, therapy interface 60 of external defibrillator 12
includes a receptacle, and cables 20 plug into the receptacle.
[0043] Therapy interface 60 includes a switch (not shown in FIG. 5)
that, when activated, couples an energy storage circuit 62 to
electrodes 18. Energy storage circuit 62 stores energy to be
delivered to patient 16 in the form of a defibrillation shock. The
switch may be of conventional design and may be formed, for
example, of electrically operated relays. Alternatively, the switch
may comprise an arrangement of solid-state devices such as
silicon-controlled rectifiers or insulated gate bipolar
transistors.
[0044] Energy storage circuit 62 includes components, such as one
or more capacitors, that store the energy to be delivered to
patient 16 via electrodes 18. Before a defibrillation shock may be
delivered to patient 16, energy storage circuit 62 must be charged.
A processor 64 directs a charging circuit 66 to charge energy
storage circuit 62 to a high voltage level. Charging circuit 66
comprises, for example, a flyback charger that transfers energy
from a power source 68 to energy storage circuit 62.
[0045] As indicated above, external defibrillator 12 may be a
manual defibrillator or an AED. Where external defibrillator 12 is
a manual defibrillator, a user of defibrillator 12 may select an
energy level for each defibrillation shock delivered to patient 16.
Processor 64 may receive the selection made by the user via a user
interface 70, which may include input devices, such as a keypad and
various buttons or dials, and output devices, such as various
indicator lights, display 24 (FIG. 1), and a speaker. Display 24
may include a cathode ray tube (CRT), light emitting diode (LED)
array, plasma screen, or liquid crystal display (LCD) screen.
[0046] Where external defibrillator 12 is an AED, processor 64
selects an energy level. For example, processor 64 may select an
energy level from a preprogrammed progression of energy levels
stored in a memory 72 based on the number of defibrillation shocks
already delivered to patient 16. In some manual defibrillator
embodiments, processor 64 may select an energy level, e.g., based
on a preprogrammed progression, to recommend to a user via user
interface 70.
[0047] In either case, when the energy stored in energy storage
circuit 62 reaches the desired energy level, processor 64 controls
user interface 70 to provide an indication to the user that
external defibrillator 12 is ready to deliver a defibrillation
shock to patient 16. For example, the indication may be an
indicator light or other visual or audible prompt. The
defibrillation shock may be delivered manually or automatically.
Where the defibrillation shock is delivered manually, the user may
direct processor 64 to deliver the defibrillation shock via user
interface 70 by, for example, pressing a button. In either case,
processor 64 activates the switches of interface 60 to electrically
connect energy storage circuit 62 to electrodes 18, and thereby
deliver the defibrillation shock to patient 16. Therapy interface
60, energy storage circuitry 62 and charging circuit 66 are
examples of therapy delivery circuitry that deliver therapy to
patient 16 under control of processor 64.
[0048] Processor 64 or other circuitry modulates the defibrillation
shock waveform delivered to patient 16. Processor 64 may, for
example, control the switches of interface 60 to regulate the shape
and width of the shock. Processor 64 may control the switches to
modulate the shock to, for example, provide a multiphasic shock,
such as a biphasic truncated exponential shock, as is known in the
art.
[0049] Processor 64 may perform other functions as well, such as
monitoring electrical activity of the heart of patient 16 sensed
via electrodes 18. Therapy interface 60 may include circuitry for
sensing the electrical activity of the heart via electrodes 18.
Processor 64 determines whether heart 22 of patient 16 is
fibrillating based upon the sensed electrical activity in order to
determine whether a defibrillation shock should be delivered to
patient 16. Where a defibrillation shock has already been
delivered, processor 64 evaluates the efficacy of the delivered
defibrillation shock by determining if heart 22 is still
fibrillating in order to determine whether an additional
defibrillation shock is warranted. Processor 64 may automatically
deliver defibrillation shocks based on these determinations, or may
advise the caregiver of these determinations via user interface 70.
Processor 64 may display an electrocardiogram (ECG) that reflects
the sensed electrical activity via user interface 70, e.g., via
display 24 (FIG. 1).
[0050] Processor 64 may store an indication of the time of delivery
of each defibrillation shock delivered to patient 16 as medical
event information within memory 72 for patient 16. Processor 64 may
also store the energy level of each pulse and other characteristics
of each pulse, such as the width, amplitude, or shape, as medical
event information for patient 16. Processor 64 may also store a
digital representation of the ECG, or a heart rate over time
determined based on the electrical activity of the heart of patient
16 detected via electrodes 18 within memory 72 as medical event
information for patient 16. Further, processor 64 may control
delivery of other types of therapy to patient 16 via electrodes 18,
such as cardioversion or pacing therapy, and store information
describing the times that such therapies were delivered and
parameters of such therapies, such as cardioversion pulse energy
levels and pacing rates, as medical event information for patient
16.
[0051] Where external defibrillator 12 is more fully featured,
e.g., a manual paramedic or hospital defibrillator, defibrillator
12 may also include additional sensors 74A-74N (collectively
"sensors 74") coupled to processor 64, such as sensors to measure
blood oxygen saturation, blood pressure, respiration, and the
amount of oxygen or carbon dioxide in the air inhaled or exhaled by
patient 16. Sensors 74 may be included within or coupled to
external defibrillator 12. External defibrillator 12 may include
circuitry that conditions the signals generated by sensors 74 such
that they may be analyzed by processor 64, such as one or more
analog to digital converters to, and suitable filter and amplifier
circuitry.
[0052] Processor 64 may also store the signals generated by these
sensors within memory 72 as medical event information for patient
16. As examples, processor 64 may store any of a capnograph, a
plethysmograph, a blood oxygen saturation over time, a blood
pressure over time, a pulse rate over time determined based on
measured blood pressure, end tidal carbon dioxide measurements,
and/or measurements of the fraction of carbon dioxide in air
inspired or expired within memory 72 as medical event information
for patient 16. Processor 64 may also receive other information
collected by a user during treatment of patient 16, such as a
location of treatment or time of death, and store such information
as medical event information for the patient. Processor 64 may
begin to store medical event information in memory 72 when
defibrillator 12 is powered on to respond to a medical emergency
involving patient 16.
[0053] Processor 64 may, for example, include one or more of a
microprocessor, DSP, ASIC, FPGA, or other equivalent integrated or
discrete logic circuitry. Memory 72 may include program
instructions that cause processor 64 to perform the functions
attributed to processor 64 and defibrillator 12 herein.
Accordingly, this disclosure also contemplates computer-readable
media storing instructions to cause processor 64 to provide the
functionality described herein. Memory 72 may include any of a
variety of solid state, magnetic or optical media, such as RAM,
ROM, CD-ROM, magnetic disk, EEPROM, or flash memory.
[0054] In the example illustrated by FIG. 5, external defibrillator
12 includes a detection/telemetry interface 76. Detection/telemetry
interface 76 may include a port or other physical interface to
receive cable 30, which is coupled to detection device 28, and to
electrically couple circuitry within defibrillator 12 to circuitry
within detection device 28 via cable 30. Cable 30 may include
conductors to carry both power and data to and from detection
device 28. Alternatively, detection device 28 may be
battery-powered and communicate with external defibrillator 12 by
wireless telemetry. Processor 64 communicates with IMD 14 via
detection/telemetry interface 76 and detection device 28.
[0055] In some embodiments, as illustrated in FIG. 5,
detection/telemetry interface 76 may convey data between processor
64 and detection device 28, as well as provide power from
defibrillator 12 to power the circuitry within detection device 28.
As will be described below with reference to FIG. 7, detection
device 28 may incorporate wireless telemetry circuitry and one or
more antennae for communication with IMD 14. Detection device 28
may also incorporate a magnet to trigger initiation of telemetry by
IMD 14. In such embodiments, detection/telemetry interface 76 may
include any of a variety of known digital data interfaces, such as
a universal serial bus (USB) interface. In some embodiments, the
detection device may not be integrated with telemetry circuitry. In
such embodiments, detection device 28 may be configured simply to
trigger initiation of telemetry by IMD 14. Telemetry circuitry may
be incorporated within defibrillator 12, or there may be a separate
telemetry interface and telemetry head, independent of detection
device 28, for providing communication with IMD 14.
[0056] In other embodiments, external defibrillator 12 may include
the telemetry circuitry, and detection device 28 may include only
one or more antennae for communication with IMD 14. In this case,
detection device 28 receives wireless telemetry signals from IMD 14
but transmits the received signals to defibrillator for processing.
Further, in still other embodiments, defibrillator 12 may include
both telemetry circuitry and antennae for communication with IMD
14. Defibrillator 12 need not be coupled to detection device 28 in
order to communicate with IMD 14. In such embodiments, detection
device 28 may provide wireless communication with defibrillator 12,
and may be battery powered, e.g., with a non-rechargeable or
rechargeable battery, instead of receiving power from defibrillator
12.
[0057] FIG. 6 is a flowchart illustrating exemplary operation of
external defibrillator 12. External defibrillator 12 is brought to
patient 16 in response to a medical emergency involving patient 16,
such as a ventricular fibrillation (VF) or sudden cardiac arrest
(SCA) experienced by the patient. A user operates external
defibrillator 12, and follows prompts from external defibrillator
12 to visually inspect patient 16 to determine whether patient 16
has an IMD, and if so, to determine the location of the IMD within
patient 16. In some embodiments, the user is aided not only by
visual or audible prompts, but also detection device 28.
[0058] In the example of FIG. 6, external defibrillator 12 prompts
the user to examine the patient's chest for a scar near the
patient's clavicle (80). As mentioned previously, external
defibrillator 12 may include a user interface that provides a
medium for user input indicating whether the user has found a scar
near the patient's clavicle. If the user indicates he has found
such a scar (yes branch of 82), external defibrillator 12 prompts
the user to place detection device 28 on the patient near the scar
(84), so that detection device 28 may initiate communication by IMD
14, e.g., by triggering telemetry with a magnet carried by
detection device 28.
[0059] If the user indicates he does not find such a scar (no
branch of 82), external defibrillator 12 prompts the user to
examine the patient for a raised portion of skin near the patient's
clavicle (86). If the user indicates he has found such a raised
portion of skin (yes branch of 88), external defibrillator 12
prompts the user to place detection device 28 on the patient near
the raised portion (90), so that detection device 28 may initiate
communication by IMD 14. Again, detection device 28 may integrate
wireless telemetry circuitry for communication with IMD 14, or
simply include a magnet to trigger telemetry by IMD 14.
[0060] If the user indicates he does not find such a raised portion
of skin (no branch of 88), external defibrillator 12 prompts the
user to place detection device 28 on the patient near the patient's
clavicle (92). External defibrillator 12 may provide other prompts
(not shown) prompting the user to move the detection device to
various areas of the patient's chest to use the detection
capabilities of the detection device to search for an IMD. For
example, the user may swipe detection device 28 across the
patient's chest, near the clavicle or elsewhere, to initiate
telemetry by IMD 14. Detection device 28 may include telemetry
circuitry to detect telemetry signals, and thereby detect the
presence of IMD 14. Based on detected signal strength, detection
device 28 may indicate the relative proximity of the detection
device 28 to the implant site of IMD 14. As discussed previously,
detection device 28 may include a visible or audible indicator, or
both, to indicate the strength of the telemetry signal, and hence
the distance from the IMD 14. An indicator, such as an array of
lights in which more lights are lit as signal strength becomes
stronger, can help the user guide detection device 28 toward the
implant site of IMD 14. In turn, upon placement of detection device
28 in close proximity to IMD 14, the increased strength of the
telemetry signal will promote more reliable telemetry with the
IMD.
[0061] In embodiments in which detection device 28 includes
telemetry circuitry for communicating with IMD 14, detection device
28 placed on the patient's chest may attempt to establish
communication with IMD 14 (94). If communication cannot be
established, external defibrillator 12 may continue with its
typical therapy instructions without communicating with an IMD
(98). As one example, detection device 28 may be unable to
establish communication because patient 16 does not have an IMD at
all. As another example, detection device 28 may be unable to
locate an IMD implanted within patient 16. If communication is
established with IMD 14, then external defibrillator 12 may
coordinate therapy with IMD 14 (98), as described in further detail
below.
[0062] FIG. 7 is a block diagram further illustrating an exemplary
detection device 28 of FIG. 1. In the illustrated example,
detection device 28 includes an antenna 100 coupled to telemetry
circuitry 102. Telemetry circuitry 102 includes a wireless
transceiver for RF communication with IMD 14 via antenna 100.
Telemetry circuitry 102 may also include various circuitry for
conditioning signals transmitted or received via antenna 100, such
as analog to digital and digital to analog converters, and
appropriate amplifiers or filters.
[0063] A defibrillator interface 104 of detection device 28
interfaces with detection/telemetry interface 76 (FIG. 5) of
external defibrillator 12. Interface 104 may include a plug or
other physical interface on cable 30 that may be used to removably
or permanently couple detection device 28 to defibrillator 12, and
which electrically couples the circuitry within detection device 28
to circuitry within defibrillator 12 via detection/telemetry
interface 76. As illustrated in FIG. 7, interface 104 may convey
data between telemetry circuitry 102 and external defibrillator 12,
and may receive power from defibrillator 12 for distribution to the
various components of detection device 28. Interface 104 may
include any of a variety of known digital data interfaces, such as
a universal serial bus (USB) connector. In some embodiments, the
USB interface also may carry operating power for components of
detection device 28. In other embodiments, interface 104 may
communicate with defibrillator 12 via a wireless interface, such as
an RF or infrared interface. In these embodiments, defibrillator 12
need not be coupled to detection device 28 in order to communicate
with IMD 14. In such embodiments, detection device 28 may be
battery powered instead of receiving power from defibrillator
12.
[0064] Detection device 28 also includes a magnet 108 to trigger
initiation of telemetry by IMD 14 when detection device 28 is
swiped across the patient's body in proximity to the IMD implant
site. Processor 110 processes signals received from telemetry
circuitry 102, e.g., for transmission to defibrillator 12 via
defibrillator interface 104. In addition, processor 110 may measure
the signal strength of telemetry signals received via telemetry
circuit 102 in order to drive an indicator 112, such as a visual or
audible indicator. As described above, indicator serves to indicate
the relative proximity of detection device 28 to IMD 14 based on
the measured signal strength of telemetry signals received from the
IMD. The signal strength measurement may be performed for digital
signals converted by telemetry circuitry 102. Alternatively, an
analog signals strength measurement may be obtained by an analog
measurement circuit based on analog signals received by telemetry
circuitry. In either case, the signal strength measurement is used
to drive indicator 112.
[0065] FIG. 8 is a block diagram illustrating an example detection
device 28. In the example of FIG. 8, detection device 28 includes a
housing 111, an adhesive layer 112 and a removable backing strip
114. Detection device 28 is coupled to external defibrillator 12 by
cable 30. Adhesive layer 112 may comprise a layer of non-toxic
adhesive for adhering detection device 28 to the skin of patient
16. A user may remove removable backing layer 114 to expose
adhesive layer 112, and then attach detection device 28 to patient
16. In operation, a bottom surface 115 of detection device 28 has a
substantially planar surface designed to engage and slide across
the skin of patient 16.
[0066] In one embodiment, once a location of IMD 14 within patient
16 has been determined, defibrillator 12 may prompt the user to
attach detection device 28 to the patient's skin over IMD 14. In
particular, the user removes backing layer 114 to expose adhesive
layer 112, and thereby permit adhesive fixation of detection device
28 to the skin of patient 16 at the location of the IMD. In this
manner, when detection device 28 includes telemetry circuitry,
detection device 28 remains in proximity to IMD 14 to maintain
communication between the two devices, even when patient 16 is
moved or transported. Adhesive layer 114 thereby promotes reliable
and robust communication between defibrillator 12 and IMD 14. In
one embodiment, detection device 28 may be a disposable unit that
may be decoupled from cable 30 or defibrillator 12 and discarded
after use.
[0067] FIG. 9 is a conceptual diagram illustrating an example
system 10 that includes an external defibrillator 12 communicating
with an IMD 14 implanted within a patient 16, e.g., via detection
device 28 or independently of detection device 28. IMD 14 may store
a variety of information regarding patient 16 and IMD 14 itself
within a memory unit of IMD 14 (not shown), and external
defibrillator 12 may retrieve this information from IMD 14 during a
telemetry session. For example, IMD 14 may store demographic
information for patient 16, such as name, height, weight, sex, age,
residence, date of birth, and the like. Further, IMD 14 may store
treatment alerts for patient 16, such as medications taken by the
patient, allergies of the patient, physician name, physician phone
number, patient's hospital, patient history, patient medical
condition, patient blood type, or a do not resuscitate (DNR) order
for the patient.
[0068] IMD 14 may store information describing the type of IMD 14,
pacemaker or internal defibrillator lead types, ejection fraction,
implant lead data, an implant date, lead configuration, lead
impedance and current programmed parameters, such as a current
pacing mode, pacing amplitude, or defibrillation amplitude. IMD 14
may also store information identifying the implant location of IMD
14. When processor 64 of external defibrillator 12 receives such
information from IMD 14, processor 64 may store the information in
memory 72 as medical event information for patient 16. Such
information may then be included in a report of the treatment of
patient 16, e.g., a "run" report, along with other medical event
information collected by external defibrillator 12 as discussed
above with reference to FIG. 5. Alternatively, such information may
be received directly by a run reporting system from IMD 14.
Paramedics, first responders, or other users of external
defibrillator 12 may be required to prepare such run reports by an
emergency medical service or other regulating authority.
Alternatively, or additionally, such information may be downloaded
from the detection device or the run reporting system to a database
management system of an emergency room or other location. The
information would then be available to a physician.
[0069] Because external defibrillator 12 may retrieve such patient
and device information from IMD 14 and include the information
within the medical event information for patient 16 automatically,
a user of the external defibrillator may not be required to take
time to collect such information from patient 16, family members,
or bystanders, and enter the information into external
defibrillator 12 manually via user interface 70 of the
defibrillator. Consequently, the user's time and attention may
remain focused on treating patient 16. In some embodiments, if
external defibrillator 12 is an AED, it may be configured to
transfer such information to another defibrillator, such as an ALS
defibrillator carried by a paramedic, e.g., by wired or wireless
communication, or by physical transfer of a memory card or other
data storage medium.
[0070] IMD 14 may also store physiological and therapy information.
For example, IMD 14 may store information relating to current
status and history of therapy delivery by the IMD to patient 16.
External defibrillator 12 may retrieve this stored information from
IMD 14, and may also receive real-time values for one or more
physiological parameters and real-time indications of therapies
delivered or scheduled for delivery by the IMD from the IMD. For
example, external defibrillator 12 may receive EGM samples sensed
by IMD 14 via leads 26, and may receive a real-time ECG recorded
and stored by IMD 14. EGM signals are a record of changes of
cardiac electric potentials, as measured with electrodes placed
within the heart, either through catheters or transvenous leads.
Real-time ECG samples may be collected using electrodes built into
the IMD exterior metal housing. External defibrillator 12 may store
any or all of the past or real-time information received from IMD
14 within memory 72.
[0071] In addition, external defibrillator 12 may receive
information indicating events or operations within an implanted
device, such as pacing, shock or sensing events, all of which may
be referred to as IMD event information. An example of such
information is the information presented by the Marker Channel.TM.
functionality provided by various IMDs manufactured by Medtronic,
Inc. of Minneapolis, Minn. Such IMD event information can be used
by the external defibrillator 12 to interpret operation of IMD 14.
For instance, if the patient is in ventricular fibrillation, a life
threatening event, and the patient has a pacemaker that is
delivering pacing pulses, external defibrillator 12 may use the IMD
event information obtained from IMD 14 to determine if the pulses
it records from the electrodes 18 are occurring at the same time as
the paced events indicated by the IMD event information. If so,
then external defibrillator 12 can conclude that the IMD 14 is
generating these events. As another example, external defibrillator
12 may use electrodes 18 to measure the rate of change of a
measured voltage to recognize pacing pulses. In either case, the
external defibrillator 12 can then analyze periods between the
pacing pulses to identify ventricular fibrillation or send a
command to the pacemaker to change the pacing rate to facilitate
better interpretation of the patient's intrinsic rhythm. As a
further example, external defibrillator 12 may detect an impedance
signal generated by IMD 14, e.g., changes in tissue impedance due
to pacing pulses by IMD 14. External defibrillator 12 may use this
information to determine that IMD 14 is present within patient
16.
[0072] Further, external defibrillator 12 may receive EGM or heart
rate data stored by IMD 14, or ECG information obtained via
electrodes 18, including average values or other statistical
summaries of the heart rate of patient 16 over time. External
defibrillator 12 may also receive current heart rate values, or
current average heart rate value, e.g., averaged over a relatively
short period of time such as a minute, from the IMD. External
defibrillator 12 may also receive stored or real-time values for
other physiological parameters that may be detected by IMD 14 as
discussed above, such as blood pressure and blood flow. Using this
information, external defibrillator 12 can make more informed shock
decisions, and control the timing and parameters of shocks
delivered to the patient by the external defibrillator.
[0073] Processor 64 of external defibrillator 12 may provide
prompts to a user via user interface 70, e.g., via speaker 32
and/or display 24, based on the information received from IMD 14.
In some embodiments, providing prompts based on the information
received from IMD 14 comprises modifying programmed prompts that
may have otherwise been provided to a user of defibrillator 12 in
the absence of communication with IMD 14. For example, memory 72 of
external defibrillator 12 may store visual or audible prompts
provided to a user by processor 64 that indicate locations for the
user to place electrodes 18 on patient 16. If an IMD 14 is
detected, however, the prompts may be modified to direct the user
to place electrodes 18 at locations situated at a distance from the
IMD implant site. For example, the prompts may advise the user to
place the defibrillation electrodes 18 at least six inches (15.24
cm) away from the IMD implant site. In this manner, electromagnetic
interference between external defibrillator 12 and IMD 14, as well
as risk of damage to or reprogramming of IMD 14 caused by
defibrillation shock energy levels, may be reduced. Positioning the
electrodes 18 further away from the IMD 14 may be beneficial to
improve the performance of the IMD and external defibrillator 12
when both are present and operating together.
[0074] As another example, processor 64 may prompt a user of
external defibrillator 12 with patient treatment alert information
received from IMD 14. For example, processor 64 may provide prompts
to the user indicating allergies, potential drug interactions,
patient history, patient medical condition, or a DNR order for
patient 16. Because patient treatment alert information may impact
treatment decisions made by a user of external defibrillator 12,
processor 64 may use bold or flashing text, flashing lights,
audible alerts, or the like to draw the attention of the user to
the presence of one or more patient treatment alerts.
[0075] Additionally, processor 64 may prompt a user with a time of
onset of the current medical emergency, or a time elapsed since
onset of the medical emergency, based on the time of onset
information received from IMD 14. The efficacy of therapies that
could be delivered to the patient may vary based on the amount of
time elapsed since onset of the medical emergency, e.g., amount of
time in fibrillation or SCA. Consequently, a user of external
defibrillator 12 may provide different therapies to patient 16
based on the time of onset or amount of time elapsed indicated by
external defibrillator 12 based on information received from IMD
14. For example, a user of external defibrillator 12 may elect to
deliver defibrillation shocks to patient 16 if the patient has been
in SCA or fibrillation for less than five minutes, and elect to
perform CPR on the patient if the patient has been in SCA or
fibrillation for greater than five minutes. In some embodiments,
external defibrillator 12 may prompt the user to provide a
particular therapy or type of monitoring based on the onset or
elapsed time information received from IMD.
[0076] Further, if the received information indicates that IMD 14
is scheduled to deliver a therapy to patient 16, processor 64 may
provide a prompt notifying the user of the upcoming delivery of
therapy. For example, IMD 14 may identify a shockable arrhythmia of
heart 22, and transmit an indication to external defibrillator 12
that IMD 14 will deliver a defibrillation shock to the heart.
Processor 64 may direct the user to avoid contact with patient,
e.g., stop CPR, for a period of time to avoid receiving a portion
of the energy of the defibrillation shock delivered by IMD 14,
which may cause discomfort or injury to the user.
[0077] Processor 64 may also display some or all of the information
received from IMD 14 via display 24. For example, processor 64 may
receive and display the name of patient 16 as stored by IMD 14,
allowing a user of external defibrillator 12 to address the patient
by name without having to ask the patient, family members, or other
bystanders.
[0078] Further, processor 64 may display real-time values of
physiological parameters sensed by IMD 14, such as a real-time ECG
or EGM sensed by IMD 14 via leads 26, via display. Through
communication with IMD 14, external defibrillator 12 may be able to
display values of physiological parameters that may not have
otherwise been able to be sensed by external defibrillator 12.
Processor 64 may provide prompts based on some of these values. For
example, processor 64 may provide audio or visual prompts regarding
the efficacy of CPR provided by a user of external defibrillator
12, e.g., instruction to apply more or less forceful chest
compressions, based on blood pressure or blood flow values measured
by IMD 14.
[0079] EGM waveforms detected by IMD 14 via leads 26 or ECG
waveforms may be of a higher quality than an ECG detected by
external defibrillator 12 via electrodes 18. For example, an EGM or
ECG waveform detected by IMD 14 may be less likely to include
motion artifacts caused by CPR chest compressions than an ECG
detected by the external defibrillator. Consequently, where
available from IMD 14, processor 64 of the external defibrillator
may display a real-time EGM or ECG waveforms received from IMD 14.
In some embodiments, the processor may select either the ECG
detected by the external defibrillator or ECG or EGM received from
the IMD based on criteria related to the quality of the ECGs, such
as noise or impedance. For example, the processor may select the
IMD ECG or EGM when available unless signal to noise ratio of the
external ECG, i.e., the ECG detected by the external defibrillator,
is above a threshold value.
[0080] Processor 64 may also display information indicating
therapies delivered to patient 16 by IMD 14 via display 22.
Processor 64 may also display information indicating a current
status of IMD 14, i.e., what IMD 14 is currently doing. If the
displayed information indicates that the IMD has already delivered
therapy to patient 16 in response to the current medical emergency,
the user may consider such information and thereby avoid delivering
redundant therapies to patient 16. For example, the displayed
information may indicate energy levels of defibrillation shocks
delivered to patient by IMD 14, and the user may select an energy
level for a defibrillation shock to be delivered by external
defibrillator 12 that is adjusted based on the energy levels of the
defibrillation shocks delivered by the IMD. For example, the user
may select an energy level for a defibrillation shock to be
delivered by external defibrillator 12 that is greater than the
energy levels of the defibrillation shocks delivered by the IMD if
the pulse delivered by the IMD failed to defibrillate heart 22.
[0081] External defibrillator 12 may also deliver therapy to
patient 16 based on the information received from IMD 14. For
example, in embodiments in which processor 64 selects an energy
level for a defibrillation shock to be delivered to patient 16 by
external defibrillator 12, processor 64 may select the energy level
based on the information. The information received from IMD 14 may
indicate an energy level of a defibrillation shock delivered to
patient 16 by IMD 14, and processor 64 may select an energy level
for a defibrillation shock to be delivered by external
defibrillator 12 based on the indicated energy level. Processor 64
may select a higher energy level to avoid delivering a redundant
defibrillation shock which may have already proven ineffective at
ending fibrillation of heart 22.
[0082] As another example, in embodiments in which processor 64
analyzes an ECG to determine whether to deliver therapy, e.g., a
defibrillation shock, to patient 16, processor 64 may analyze a
real-time ECG received from IMD 14. As discussed above, the ECG or
EGM received from IMD 14 may be of a higher quality, e.g., less
susceptible to motion artifacts from CPR chest compressions, than
an ECG detected via electrodes 18. Consequently, by using an ECG or
EGM received from IMD 14, processor 64 may be able to more
accurately determine whether therapy should be delivered to patient
16. Additionally, as discussed above, processor 64 may select one
of the IMD and external ECG for analysis based on a criterion
related to the quality of at least one of the ECGs, thereby
supporting coordinated operation of external defibrillator 12 and
IMD 14.
[0083] Further, in some embodiments, IMD 14 may use different
algorithms to determine whether to deliver therapy to patient 16
than are available to processor 64, and processor 64 may deliver
therapy based on a therapy delivery decision received from IMD 14.
For example, IMD 14 may apply arrhythmia detection algorithms to
the rhythm of heart 22 that distinguish between ventricular and
supra-ventricular arrhythmias. IMD 14 may decide that a
defibrillation shock should be delivered in response to detection
of a ventricular arrhythmia, and that a defibrillation shock should
not be delivered in response to detection of a supra-ventricular
arrhythmia. Processor 64 may control delivery of a defibrillation
shock to patient 16 based on a defibrillation shock delivery
decision received from IMD 14. In this manner, external
defibrillator 12 may, for example, avoid delivering a
defibrillation shock to treat a supra-ventricular arrhythmia. In
some embodiments, a user may override a decision by processor 64
not to deliver therapy based on information received from IMD 14,
and direct defibrillator 12 to deliver therapy.
[0084] Additionally, processor 64 may control delivery of therapy
by external defibrillator 12, e.g., control charging circuit 66 and
therapy delivery interface 60, based on onset or elapsed time
information received from IMD 14. For example, processor 64 may
select a therapy, such as defibrillation, cardioversion or pacing,
or the energy levels for such therapy, based on the time. Processor
64 may alternatively suspend delivery of therapy by external
defibrillator 12 based on the time information.
[0085] Processor 64 of external defibrillator 12 may also control
delivery of therapy by IMD 14. For example, processor 64 may
suspend delivery of therapy by IMD 14 during treatment of patient
16 with external defibrillator 12. By suspending delivery of
therapy by IMD 14, external defibrillator 12 may avoid interference
between therapies delivered by IMD 14 and defibrillator 12. As
another example, external defibrillator 12 may deliver therapy upon
receiving information from IMD 14 that IMD 14 has a low battery, or
that IMD 14 has delivered a maximum number of shocks.
[0086] As another example, processor 64 may change a therapy
delivery mode of IMD 14. For example, after defibrillation by
external defibrillator 12, some patients may benefit from pacing in
a different mode than the mode in which IMD 14 had been programmed.
Processor 64 may change the mode of IMD 14 by, for example,
changing IMD 14 from single to dual chamber pacing or from demand
to non-demand pacing, or by changing a pacing rate or the
aggressiveness of rate responsive pacing or by increasing pacing
amplitudes.
[0087] Further, the hearts of some patients are left in a state of
pulseless electrical activity after being defibrillated. Such
patients may benefit from delivery of post extra-systolic
potentiation (PESP) pacing, which may increase the cardiac output
of their heart. If IMD 14 is capable of delivering post
extra-systolic pacing pulses, processor 64 may direct IMD 14 to do
so after heart 22 has been defibrillated. In some embodiments,
processor 64 may direct IMD 14 to delivery other therapies provided
by the IMD that may not be available from the external
defibrillator, such as cardioversion or anti-tachycardia pacing
therapies or by increasing pacing amplitudes, after the shock was
delivered by the AED.
[0088] Additionally, processor 64 may direct IMD 14 to deliver
therapy that is coordinated with therapy delivered by defibrillator
12. For example, processor 64 may direct IMD 14 to deliver a
defibrillation shock synchronized with, or with some other temporal
relationship to, a defibrillation shock delivered by defibrillator
12. Delivery of defibrillation shocks by both IMD 14 and external
defibrillator 12 may be more efficacious than delivery of
defibrillation shocks by either the external defibrillator or the
IMD alone.
[0089] As another example, external defibrillator 12 may include
pacing circuitry for delivery of pacing pulses to heart 22 of
patient 16 via electrodes 18. To the extent IMD 14 is not capable
of delivering post extra-systolic pacing pulses, processor 64 may
control the pacing circuitry to deliver pacing pulses an
extra-systolic interval after delivery of a pacing pulse by IMD 14,
or an intrinsic depolarization of heart 22. Processor 64 of
external defibrillator 12 may interrogate IMD 14 to identify the
therapies sensing capabilities provided by the IMD. Processor 64
may control the IMD to deliver a therapy alone, or in coordination
with the external defibrillator, based on this capability
information retrieved from the IMD.
[0090] As described above, processor 64 collects medical event
information during treatment of patient 16 with external
defibrillator 12, and stores the medical event information within
memory 72 of the external defibrillator. Processor 64 may also
store the medical event information into IMD 14. In this manner,
caregivers who subsequently treat patient 16 and have access to a
programming device that communicates with IMD 14 may be able to
retrieve the medical event information. In the absence of
communication between IMD 14 and external defibrillator 12, such
caregivers may not have had access or timely access to the medical
event information, which may inform treatment decisions made by the
caregivers, and may supplement the medical records maintained for
patient 16 by the caregivers. In some embodiments, rather than a
caregiver retrieving the information with a programming device, IMD
14 may transmit the medical event information to a computing
device, computing network, or other data repository at, for
example, a hospital. The medical event information may supplement
the hospitals records for the patient, and may be available to
caregivers throughout the hospital who may treat the patient.
[0091] Various embodiments of the invention have been described.
However, one skilled in the art will appreciate that various
modifications may be made to the described embodiment without
departing from the scope of the claimed invention. For example,
although wireless communication has been described herein primarily
in the context of RF telemetry, the invention is not so limited. An
external defibrillator and IMD according to the invention may
include any of a variety of RF, optical, acoustic, or other
transducers for wireless communication. Further, although described
in the context of communication with an IMD, an external
defibrillator according to the invention may communicate with other
external medical devices that are associated with the patient, such
as a wearable defibrillator or Holter monitor. In addition,
although described in the context of an external defibrillator, the
IMD may be any implantable device, such as a neurostimulator, a
drug pump, or a diabetes monitoring device. These and other
embodiments are within the scope of the following claims.
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