U.S. patent application number 12/319833 was filed with the patent office on 2009-05-14 for acoustic physiological sensor.
Invention is credited to Douglas R. Daum, Robert J. Sweeney.
Application Number | 20090124916 12/319833 |
Document ID | / |
Family ID | 34216810 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090124916 |
Kind Code |
A1 |
Sweeney; Robert J. ; et
al. |
May 14, 2009 |
Acoustic physiological sensor
Abstract
This document describes, among other things, a body having at
least one acoustically detectable property that changes in response
to a change in a physiological condition, such as ischemia. The
body is positioned with respect to a desired tissue region. At
least one acoustic transducer is used to acoustically detect a
change in physical property. In one example, the body is pH
sensitive and/or ion selective. A shape or dimension of the body
changes in response to pH and/or ionic concentration changes
resulting from a change in an ischemia state. An indication of the
physiological condition is provided to a user.
Inventors: |
Sweeney; Robert J.;
(Woodbury, MN) ; Daum; Douglas R.; (Woodbury,
MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG & WOESSNER/BSC-CRM
PO BOX 2938
MINNEAPOLIS
MN
55402
US
|
Family ID: |
34216810 |
Appl. No.: |
12/319833 |
Filed: |
January 13, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10648837 |
Aug 26, 2003 |
7479112 |
|
|
12319833 |
|
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Current U.S.
Class: |
600/528 |
Current CPC
Class: |
A61N 1/36557 20130101;
A61N 1/3622 20130101; A61B 7/00 20130101; A61N 1/3684 20130101 |
Class at
Publication: |
600/528 |
International
Class: |
A61B 5/02 20060101
A61B005/02 |
Claims
1. An apparatus comprising: a physiological sensor including a
biocompatible body sized and shaped to be implanted within a
subject to contact tissue, at least a portion of the body including
a material having at least one physical property that changes in
response to a physiological condition predictive or indicative of a
tachyarrhythmia when that portion of the body is implanted in
contact with the tissue, wherein the change in the at least one
physical property occurs because of the contact between that
portion and the tissue, wherein the portion of the body is sized
and shaped such that the change in the physical property is
detectable using acoustic energy to provide an indication of the
physiological condition.
2. The apparatus of claim 1, wherein the change in the physical
property of the body includes a change in size of the body.
3. The apparatus of claim 1, wherein the change in the physical
property of the body includes a change in an acoustic property of
the body.
4. The apparatus of claim 1, comprising an implantable transducer
configured to supply the acoustic energy for providing the
indication of the physiological condition.
5. The apparatus of claim 1, wherein the body includes at least a
portion of a catheter.
6. The apparatus of claim 1, wherein the body includes a
sphere.
7. The apparatus of claim 1, wherein the change in the physical
property of the body is responsive to a change in pH.
8. A method comprising: introducing a physiological sensor
including a biocompatible body into contact with a tissue, wherein
the body includes at least one physical property that changes as a
result of the contact with the tissue in response to a
physiological change associated with the tissue, the physiological
change predictive or indicative of a tachyarrhythmia; transmitting
acoustic energy to the body and the tissue; receiving transmitted
acoustic energy for detecting the change in the physical property
of the body; and detecting and providing an indication of the
physiological change by detecting the change in the physical
property of the body.
9. The method of claim 8, wherein introducing the physiological
sensor includes introducing a pH sensitive biocompatible body.
10. The method of claim 8, wherein introducing the physiological
sensor includes introducing an ion sensitive biocompatible
body.
11. The method of claim 8, wherein introducing the physiological
sensor includes introducing a catheter.
12. The method of claim 8, wherein introducing the physiological
sensor includes introducing a sphere.
13. The method of claim 8, comprising introducing a device for
transmitting the acoustic energy.
14. The method of claim 8, comprising introducing a device for
receiving the transmitted acoustic energy.
15. The method of claim 8, wherein transmitting the acoustic energy
includes transmitting the acoustic energy using an implantable
transducer.
16. An apparatus comprising: a physiological sensor including a
biocompatible body, the body sized and shaped to be implanted
within a subject to contact tissue, at least a portion of the body
including a material having at least one physical property that
changes in response to a physiological condition of the tissue when
that portion of the body is implanted in contact with the tissue,
the change in the physiological condition being predictive or
indicative of ischemia, wherein the change in the at least one
physical property occurs because of the contact between that
portion and the tissue, wherein the portion of the body is sized
and shaped such that the change in the physical property is
detectable using acoustic energy to provide an indication of the
physiological condition.
17. The apparatus of claim 16, comprising an implantable transducer
configured to supply the acoustic energy for providing the
indication of the physiological condition.
18. The apparatus of claim 16, wherein the change in the physical
property of the body includes a change in size of the body.
19. The apparatus of claim 16, wherein the change in the physical
property of the body includes a change in an acoustic property of
the body.
20. The apparatus of claim 16, wherein the change in the physical
property of the body is responsive to a change in pH.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 10/648,837, filed Aug. 26, 2003, which is hereby incorporated
by reference in its entirety.
TECHNICAL FIELD
[0002] This document relates generally to medical systems, devices,
and methods, and particularly, but not by way of limitation, to an
acoustic physiological sensor.
BACKGROUND
[0003] Physiological conditions of a subject can provide useful
information about the subject's health status to a physician or
other caregiver. For example, portions of a heart muscle that
receive inadequate blood circulation may become ischemic. There is
a need for improved techniques of invasively or noninvasively
measuring changes in a physiological condition indicative of
ischemia.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] In the drawings, which are not necessarily drawn to scale,
like numerals describe substantially similar components throughout
the several views. Like numerals having different letter suffixes
represent different instances of substantially similar components.
The drawings illustrate generally, by way of example, but not by
way of limitation, various embodiments discussed in the present
document.
[0005] FIG. 1 is a schematic diagram illustrating generally one
example of a system to detect a change in at least one
physiological condition of a tissue, such as a heart.
[0006] FIG. 2 is a flow chart illustrating generally a method of
providing an indication of a physiological condition, such as by
using the system of FIG. 1, or other desired system.
[0007] FIG. 3 is a conceptual schematic diagram illustrating
generally a swelling of a spherical body from non-ischemic to
ischemic conditions.
[0008] FIG. 4 is a conceptual schematic diagram illustrating
generally a swelling of a body that changes its physical property
of morphology, shape, or stiffness from non-ischemic to ischemic
conditions.
[0009] FIG. 5 is a schematic diagram, similar to FIG. 1, but
illustrating a plurality of spherical or other bodies positioned at
desired myocardial locations, such as described above.
[0010] FIG. 6 is a schematic diagram, similar to FIG. 5, but
illustrating an example of a second intravascular lead
catheter.
DETAILED DESCRIPTION
[0011] In the following detailed description, reference is made to
the accompanying drawings which form a part hereof, and in which is
shown by way of illustration specific embodiments in which the
invention may be practiced. These embodiments, which are also
referred to herein as "examples," are described in sufficient
detail to enable those skilled in the art to practice the
invention, and it is to be understood that the embodiments may be
combined, or that other embodiments may be utilized and that
structural, logical and electrical changes may be made without
departing from the scope of the present invention. The following
detailed description is, therefore, not to be taken in a limiting
sense, and the scope of the present invention is defined by the
appended claims and their equivalents.
[0012] In this document, the terms "a" or "an" are used, as is
common in patent documents, to include one or more than one. In
this document, the term "or" is used to refer to a "nonexclusive
or," unless otherwise indicated. Furthermore, all publications,
patents, and patent documents referred to in this document are
incorporated by reference herein in their entirety, as though
individually incorporated by reference. In the event of
inconsistent usages between this documents and those documents so
incorporated by reference, the usage in the incorporated
reference(s) should be considered supplementary to that of this
document; for irreconcilable inconsistencies, the usage in this
document controls.
[0013] FIG. 1 is a schematic diagram illustrating generally, by way
of example, but not by way of limitation, one example of a system
100 to detect a change in at least one physiological condition of a
tissue, such as tissue of a heart 102. In this example, the system
includes an ultrasound or other acoustic transducer 104, which is
disposed within or near the heart 102, or any other region of
interest. In this example, a sphere or other body 106 is also
disposed within or near the heart 102 or other region of interest,
such as near the transducer 104. In this example, but not by way of
limitation, the transducer 104 is located on an intracardiac lead
108, which is coupled to an implantable cardiac rhythm management
(CRM) or other device 110. In one example, the spherical body 106
includes a diameter approximately between 1 micrometer and 50
micrometers, such as about 20 micrometers.
[0014] In this example, the device 110 includes a signal processor
circuit 112. The signal processor circuit 112 is coupled to the
transducer 104 to process an ultrasound or other acoustic signal
received from the transducer 104. In this example, the device 110
also includes a controller circuit 114. The controller circuit 114
is coupled to the transducer 104 to provide at least one control
signal to the transducer 104. In this example, the controller
circuit 114 is also coupled to the signal processor circuit 112,
such as to digitally perform additional processing on the acoustic
signal. In this example, the device 110 includes a telemetry or
other communication circuit 116. The communication circuit 116 is
coupled to the controller circuit 114, such as to receive
information about a change in at least one physiological condition
of the heart 102 or other tissue or region of interest, where the
change in the physiological condition is detected using an acoustic
determination of a change in a physical property of the body 106.
The communication circuit 116 is communicatively couplable to an
external user interface 118, such as for transmitting an indication
of the physical property, the change in the physical property, the
physiological condition, or the change in the physiological
condition for display to a user and/or recording. In one example,
the external user interface 118 includes a nearby external
programmer. In another example, the external user interface 118
includes an a computer network-linked (e.g., internet linked)
and/or telephone network-linked more distant advanced patient
management system capable of storing and/or displaying patient data
and/or performing other functions. In one example, the external
user interface 118 includes a short range communication circuit for
communication with the implantable device 110 and an
internet-linked or other long range communication circuit to
communicate with an patient management computer server.
[0015] FIG. 2 is a flow chart illustrating generally, by way of
example, but not by way of limitation, a method of providing an
indication of a physiological condition, such as by using the
system of FIG. 1 or other desired system. In the example of FIG. 2,
at 200, the transducer 104 and the body 106 are disposed near the
local region of tissue for which the indication of the
physiological condition is desired. In one example, this includes
intravascularly introducing an ultrasound transducer 104 into a
right ventricular chamber of the heart 102, such as by using an
intracardiac lead 108. In one example, this also includes
intravascularly introducing a small spherical or other body 106
into coronary vasculature, such as via the coronary arteries or
veins, to position the body 106 into contact with a local region of
a microcirculatory myocardial tissue bed for which an ischemia
determination is desired.
[0016] At 202, the transducer 104 transmits acoustic energy. In
this example, the transmitted acoustic energy is reflected by the
body 106. The reflected acoustic energy is received at the same (or
different) transducer 104. The received acoustic energy is
processed to obtain a first reading of a physiological condition
using a physical property of the body 106.
[0017] At 204, a physical property of the body 106 changes in
response to a physiological condition. In one illustrative example,
the size of a spherical body 106 changes in response to the
physiological condition of ischemia. Ischemia results from a
decreased blood flow to the heart tissue. This reduced blood flow
produces several physiological effects in the extra-cellular
portion of the ischemic tissue. For instance, the extra-cellular
space would undergo a slight decrease in sodium (Na+) ions, a
substantial increase in potassium (K+) ions, an increase in calcium
(Ca++) ions, and a decreased pH due to accumulation of metabolic
waste (e.g., particularly an increase in percentage carbon dioxide
(pCO.sub.2) and a decreased percentage oxygen (pO.sub.2). In one
example, the spherical or other at least one body 106 responds to
the change in pH, and is constructed using a pH sensitive polymer.
As a result of the decreased pH during ischemia, the body 106
adsorbs water or other bodily fluids and swells, such as
illustrated in FIG. 3. This change in a physical property of the
body 106 is acoustically detectable. It is believed that a 10%
change in diameter of the spherical body 106 will increase the
frequency of reflected acoustic energy by about 10% (e.g., from 20
MHz to 22 MHz).
[0018] At 206, the transducer 104 transmits and receives acoustic
energy to obtain a second reading of a physiological condition
(e.g., ischemia) using this change in a physical property (e.g.,
size and acoustic reflectance) of the body 106. A difference
between the first and second readings permits the detection of any
change in the physiological condition.
[0019] At 208, the system provides an indication of the
physiological condition and/or a change in the physiological
condition using any detected change in the physical property of the
body 106.
[0020] FIG. 3 is a conceptual schematic diagram illustrating
generally, by way of example, but not by way of limitation, a
swelling of a spherical body 106 from non-ischemic to ischemic
conditions, thereby increasing the frequency at which acoustic
energy is reflected from the spherical body 106.
[0021] FIG. 4 is a conceptual schematic diagram illustrating
generally, by way of example, but not by way of limitation, a
swelling of a body 400 (which need not be spherical). In this
example, the swelling changes its physical property of morphology,
shape, or stiffness from non-ischemic to ischemic conditions,
thereby increasing the frequency at which acoustic energy is
reflected from the body 400. In one example, the body 400 is
constructed from a pH sensitive polymer or other pH sensitive
material, as discussed above, to obtain the change in morphology,
shape, or stiffness. In another example, the body 400 is
constructed of an ion-selective membrane enclosure defining its
shape. Ischemia results in an altered local concentration of sodium
(Na+), potassium (K+), and calcium (Ca++). During ischemia, one or
more of these variety of ions are accepted from the local
environment across the membrane enclosure to within the body 400.
The resulting swelling of the body 400 causes an acoustically
detectable change in shape.
[0022] FIG. 5 is a schematic diagram, similar to FIG. 1, but
illustrating generally, by way of example, but not by way of
limitation, a plurality of spherical or other bodies 500 positioned
at desired myocardial locations, such as described above. This
permits detection of a change in physiological condition over a
broader region. Moreover, although the above description has
generally emphasized detecting a change in physiological condition
by using a change in acoustic reflectance due to a change in a
physical property (e.g., size and/or shape) of the body, other
techniques could rely on a change in acoustic transmission,
acoustic attenuation, and/or acoustic transit time, and/or any
other acoustic technique. In one example, the device 110 includes a
second acoustic transducer 502 (e.g., carried within a
hermetically-sealed housing enclosure of the implantable device
110, or disposed on a second intravascular catheter). In this
example, acoustic energy is transmitted from the first transducer
104 and received at the second transducer 502 (or vice versa). The
bodies 500 are positioned acoustically in between the transducers
104 and 502. A change in physiological condition (e.g., ischemia)
alters the acoustic transmission and/or attenuation between the
transducers. This is measured by the signal processor circuit 112
and the controller circuit 114.
[0023] FIG. 6 is a schematic diagram, similar to FIG. 5, but
illustrating generally, by way of example, but not by way of
limitation, a second intravascular lead catheter 600. The second
intravascular lead catheter 600 includes one or more bodies 602
that swell or otherwise alter an acoustically detectable physical
property in response to a change in a physiological condition, such
as described above. In one example, the catheter 600 is introduced
into a coronary sinus and/or great cardiac vein, such as to
position the bodies 602 in contact with a myocardial tissue region
of interest. Acoustic detection is performed either using the
single transducer 104, as described above, or by using two
transducers 104 and 502, as also described above. Alternatively,
the second intravascular lead catheter provides an appropriate
electrical connection to the one or more bodies 602 that swell or
otherwise alter a physical property, thereby changing an electrical
property (e.g., a bridge or other resistance, capacitance, etc.)
incorporated within the one or more bodies 602. In this example,
the ischemia or other physiological condition is detected
electrically instead of acoustically.
[0024] In one example, a change in physiologic condition (e.g.,
ischemia) is determined from the acoustic response of the spherical
or other body or bodies 602 to a change in the physiologic
condition. The acoustic response is compared to a baseline acoustic
response. If the acoustic response deviates from the baseline
acoustic response by an amount that is greater than a predetermined
threshold value, then a detected change in the physiologic
condition (e.g., ischemia) is declared. In one example, the
detected change in the physiologic condition is stored and/or
communicated to the remote user interface 118 for storage and/or
display or other presentation to the user. In one example, the
detected change in the physiologic condition is used in conjunction
with an alarm to alert the physician and/or the clinician (e.g.,
that the patient is undergoing an ischemic episode).
[0025] In another example, the detected change in the physiologic
condition is used to initiate or modify therapy being delivered by
the implantable cardiac rhythm management device 110. For example,
if a detected ischemia episode was preceded by a time period during
which pacing pulses were delivered at a relatively higher average
rate, then, in one example, the pacing rate is reduced. In another
example, such as where multiple pacing electrodes are disposed at
different locations about the heart, the locations or sequence of
delivery of pacing pulses from such locations is altered, such as
to shift blood toward the ischemic area of the heart tissue. In a
further example, the change in the physiologic condition is used as
a factor that is predictive of the occurrence of a future episode
of cardiac arrhythmia, such as fibrillation. One example of using
factor(s) predictive of future arrhythmias (as well as taking
preventative measures) is described in Robert J. Sweeney et al.
U.S. Pat. No. 6,272,377 entitled CARDIAC RHYTHM MANAGEMENT SYSTEM
WITH ARRHYTHMIA PREDICTION AND PREVENTION, which is assigned to
Cardiac Pacemakers, Inc., and which is incorporated by reference
herein in its entirety, including its disclosure of devices and
methods for predicting and preventing future arrhythmias. In one
example, the detected change in the physiologic condition is used
to alter the state of the cardiac rhythm management device 110 in
anticipation of a future physiologic event. For example, the device
110 could monitor the subject with greater time resolution during
an ischemia episode, or could pre-charge defibrillation capacitors
to more readily deliver a defibrillation pulse.
[0026] Although the above examples have emphasized use of an
implantable device 110, such as for obtaining chronic measurements,
alternatively, each of these examples is implemented with an
external device, operating similarly.
[0027] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example,
aspects of the above-described embodiments may be used in
combination with each other. Many other embodiments will be
apparent to those of skill in the art upon reviewing the above
description. The scope of the invention should, therefore, be
determined with reference to the appended claims, along with the
full scope of equivalents to which such claims are entitled. In the
appended claims, the terms "including" and "in which" are used as
the plain-English equivalents of the respective terms "comprising"
and "wherein." Moreover, in the following claims, the terms
"first," "second," and "third," etc. are used merely as labels, and
are not intended to impose numerical requirements on their
objects.
* * * * *