U.S. patent application number 11/901376 was filed with the patent office on 2008-01-10 for wireless electrocardiograph system and method.
Invention is credited to Nicholas C. Hopman, Franco Lodato, Daniel L. Williams.
Application Number | 20080009694 11/901376 |
Document ID | / |
Family ID | 22817794 |
Filed Date | 2008-01-10 |
United States Patent
Application |
20080009694 |
Kind Code |
A1 |
Hopman; Nicholas C. ; et
al. |
January 10, 2008 |
Wireless electrocardiograph system and method
Abstract
A method and system for wireless ECG monitoring is provided. An
electrode connector, transmitter and receiver operate with existing
electrodes and ECG monitors. The electrode connector includes
connectors for attaching to disposable or reusable single
electrodes. The transmitter transmits the signals from the
electrodes to the receiver. The receiver passes the electrode
signals to the ECG monitor for processing. ECG monitors used with
an electrical conductor, for example wire connections to
electrodes, are connected with the receiver, avoiding the purchase
of a new monitor. Any legacy ECG monitor, including different ECG
monitors, connects with the receiver using the ECG monitor's
lead-wires. The ECG monitor operates as if directly connected to
the electrodes without the problems discussed above associated with
wires running from the ECG monitor to the patient.
Inventors: |
Hopman; Nicholas C.; (Lake
Zurich, IL) ; Williams; Daniel L.; (Norwell, MA)
; Lodato; Franco; (Weston, FL) |
Correspondence
Address: |
LOTT & FRIEDLAND, P.A.
ONE EAST BROWARD BLVD.
SUITE 1609
FORT LAUDERDALE
FL
33301
US
|
Family ID: |
22817794 |
Appl. No.: |
11/901376 |
Filed: |
September 17, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10439574 |
May 16, 2003 |
7272428 |
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|
11901376 |
Sep 17, 2007 |
|
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|
09908509 |
Jul 17, 2001 |
6611705 |
|
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10439574 |
May 16, 2003 |
|
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60219082 |
Jul 18, 2000 |
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Current U.S.
Class: |
600/374 |
Current CPC
Class: |
A61B 5/282 20210101;
A61B 5/0006 20130101; A61B 5/6831 20130101; A61B 5/25 20210101 |
Class at
Publication: |
600/374 |
International
Class: |
A61N 1/05 20060101
A61N001/05 |
Claims
1. An electrode connector for ECG monitoring of a patient, the
connector comprising: material operable to interconnect a plurality
of electrodes; and a plurality of electrode releasable connectors
provided on the material wherein the material comprises a plurality
of expandable arms, each of the plurality of expandable arms
corresponding to respective ones of the plurality of electrode
releasable connectors, wherein the electrode connector is comprised
of a memoryless material.
2. The electrode connector of claim 1 wherein the electrode
connector is comprised of polypropylene or polyethylene fabric, a
cloth, a fabric or another flexible material.
3. The electrode connector of claim 1 wherein the electrode
connector is comprised of Mylar.
4. The electrode connector of claim 1 wherein at least one of the
expandable arms comprises a serpentine pattern.
5. The electrode connector of claim 3, wherein the serpentine
pattern has breakable connections.
6. The electrode connector of claim 1 further comprising a second
precordial connector the precordial connector.
7. The electrode connector of claim 1 wherein the electrode
connector is defibrillation resistant.
8. The electrode connector of claim 1 wherein each of the plurality
of arms include an electrical conductor.
9. The electrode connector of claim 8 wherein each of the
electrical conductors electrically connects with the respective
electrode connector.
10. An electrode connector for ECG monitoring of a patient, the
electrode connector the connector comprising: material operable to
interconnect a plurality of electrodes; and a plurality of
electrode releasable connectors provided on the material wherein
the material comprises a plurality of expandable arms, each of the
plurality of expandable arms corresponding to respective ones of
the plurality of electrode releasable connectors, wherein the
expandable arms are expandable to approximate right leg, left leg,
right arm left arm electrode positions.
11. The electrode connector of claim 10 wherein the electrode
connector is comprised of polypropylene or polyethylene fabric, a
cloth, a fabric or another flexible material.
12. The electrode connector of claim 10 wherein the electrode
connector is comprised of Mylar.
13. The electrode connector of claim 10 wherein at least one of the
expandable arms comprises a serpentine pattern.
14. The electrode connector of claim 8, wherein the serpentine
pattern has breakable connections.
15. The electrode connector of claim 8 further comprising a second
precordial connector
16. The electrode connector of claim 10 wherein the electrode
connector is defibrillation resistant.
17. The electrode connector of claim 10 wherein each of the
plurality of arms include an electrical conductor.
18. The electrode connector of claim 17 wherein each of the
electrical conductors electrically connects with the respective
electrode connector.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of and claims the
benefit of the filing date pursuant to 35 U.S.C. .sctn.119(e) of
Provisional Application Ser. No. 60/219,082, filed Jul. 18, 2001,
for a WIRELESS EKG, the disclosure of which is hereby incorporated
by reference.
BACKGROUND
[0002] This invention relates to medical monitoring systems and
methods. In particular, a biomedical system and method for
monitoring a patient is provided.
[0003] Biomedical monitoring systems include bedside,
transportable, ambulatory and discrete vital sign monitors. In
vital signs monitors, electrocardiograph (ECG), temperature, blood
pressure or other characteristics of a patient are monitored.
[0004] ECG systems are used for monitoring activity of a patient's
heart. For example, three electrodes are positioned on the patient.
The signal from one electrode is used as a reference signal for a
difference between the signals of two other electrodes (e.g. ECG
vector). By using this reference signal, and a differential
amplifier configuration, common mode interference can be
essentially eliminated or reduced. As another example, nine
electrodes are positioned on the patient for a "12-lead" analysis
of electrical activity of the heart.
[0005] Wires are connected from the electrodes to an ECG monitor.
The ECG monitor processes the signals and outputs ECG data, such as
a plurality of traces representing activity of the heart by
measuring electrical signals at different positions on the patient.
However, the wires inhibit movement by and around the patient. The
wires will stress the electrodes, resulting in malfunction or
disconnection from the patient. A caregiver's time is then required
to reconnect or replace the electrodes. Patients are often moved
during a day, requiring disconnecting one ECG monitor and
reconnecting another ECG monitor. Often the electrodes also need to
be removed and replaced. If not replaced in exactly the same
position, the patient's ECG will be different from ECG monitor to
ECG monitor, creating an artifact in the ECG.
[0006] Wireless ECG systems connect the electrodes to a transmitter
to avoid wires from the patient to a monitor. In the example
described in WO 94/01039, a microchip is positioned proximate the
electrodes on the patient. The microchip analyzes the signals from
the electrodes and transmits the results (see page 42). The results
are received and provided to a printer or monitor (see page 26).
However, a complete system including a monitor, printer or recorder
operable to receive the signals as processed by the microchip on
the patient is required.
[0007] Holter monitors record a patient's vital signs over a time
period. The patient carries the complete monitor and recorder. The
information can be downloaded or otherwise obtained for subsequent
analysis. However, many of these systems limit the bandwidth of
signals to suppress artifacts associated with patient movement, so
information can be lost. Special monitors or other devices may be
required for obtaining the stored data for analysis, preventing
maximum use of other equipment.
[0008] Wireless ECG systems often use patches or strips for
positioning electrodes. The strip is fabricated with a plurality of
electrodes electrically connected to the transmitter. If one
electrode fails, the entire strip is replaced.
BRIEF SUMMARY
[0009] The present invention is defined by the following claims,
and nothing in this section should be taken as a limitation on
those claims. By way of introduction, the preferred embodiment
described below includes a method and system for wireless ECG
monitoring.
[0010] An electrode connector, transmitter and receiver operate
with existing electrodes and ECG monitors. The electrode connector
includes connectors for attaching to disposable or reusable single
electrodes. The transmitter transmits the signals from the
electrodes to the receiver. The receiver passes the electrode
signals to the ECG monitor for processing. ECG monitors used with
an electrical conductor, for example wire connections to
electrodes, are connected with the receiver, avoiding the purchase
of a new monitor. Any legacy ECG monitor, including different ECG
monitors, connects with the receiver using the ECG monitor's
lead-wires. The ECG monitor operates as if directly connected to
the electrodes without the problems discussed above associated with
wires running from the ECG monitor to the patient.
[0011] In a first aspect of the invention, an electrode connector
for ECG monitoring of a patient is provided. Material is operable
to interconnect a plurality of electrodes. The material includes a
plurality of electrode releasable connectors.
[0012] In a second aspect, a method for connecting electrodes for
ECG monitoring is provided. A plurality of electrodes are placed. A
plurality of expandable arms, one expandable arm provided for each
of the plurality of electrodes, are expanded. The plurality of
expandable arms are connected to the plurality of electrodes.
[0013] In a third aspect, a system for monitoring electrical
signals generated by a patient is provided. A transmitter is
operable to transmit electrode signals. A receiver is responsive to
the transmitter to generate the electrode signals. The receiver has
an output connector operable to connect with electrode wires of an
ECG monitor.
[0014] In a fourth aspect, a method for monitoring electrical
signals generated by a patient is provided. Signals are received
from electrodes. Information representing the signals received from
electrodes is transmitted. The information is received. The signals
received from the electrodes are reconstructed. Existing wires from
an ECG monitor are connected. The reconstructed signals are
received at the ECG monitor.
[0015] In a fifth aspect, a wireless ECG monitoring system for
reconstructing signals at a plurality of electrodes is provided. An
electrode connector is operable to connect with the plurality of
electrodes. A single transmitter is operable to connect with the
electrode connector. The single transmitter is operable to transmit
signals from the plurality of electrodes. A receiver is operable to
reconstruct the signals from the plurality of electrodes.
[0016] In a sixth aspect, a method for wireless ECG monitoring with
reconstructed signals from a plurality of electrodes is provided.
The plurality of electrodes are connected with an electrode
connector. Signals from the plurality of electrodes are transmitted
with a single transmitter. The signals transmitted by the
transmitter are received. The signals from the plurality of
electrodes are reconstructed.
[0017] Further aspects and advantages of the invention are
discussed below in conjunction with the preferred embodiments.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0018] FIG. 1 is a block diagram of one embodiment of an ECG
monitoring system.
[0019] FIGS. 2A-D are front views of various embodiments of
electrode connectors and transmitters of the ECG monitoring system
of FIG. 1.
[0020] FIG. 3 is a perspective view of one embodiment of an
expandable arm of the electrode connectors of FIGS. 2A-D.
[0021] FIG. 4 is a front view of one embodiment of a belt used with
the electrode connector of FIG. 2D.
[0022] FIG. 5 is a flow chart of one embodiment for operation of
the ECG monitoring system of FIG. 1.
[0023] FIG. 6 is a perspective view of another embodiment of an ECG
monitoring system.
[0024] FIG. 7 is a block diagram of one embodiment of a
transmitter.
[0025] FIG. 8 is a block diagram of one embodiment of a
receiver.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] A wireless ECG system uses existing electrodes and ECG
monitors. The wireless ECG system wirelessly bridges between
conventional electrodes on a patient and a conventional ECG
monitor. The wireless ECG system is an accessory that augments the
capability of conventional, or legacy, ECG monitors or systems. The
wireless ECG system functions as a wireless extension cord that
physically un-tethers a patient from a conventional lead-wire cable
connected to a conventional ECG monitor.
[0027] The wireless ECG system includes three components: an
electrode connector (e.g. sensor array), a transmitter (e.g.
ECG-radio) and a receiver (e.g. base station). These components
interpose between conventional electrodes worn by a patient and a
conventional lead-wire cable of a conventional ECG monitor without
requiring any additional changes to the conventional electrodes,
the conventional lead-wire cables, or the conventional ECG
monitoring systems. An electrode connector with releasable
connections, such as snap terminals, and expandable arms
electrically connects with existing electrodes, such as snap
terminal type electrodes. A transmitter provides signals received
from the electrodes to the receiver. The receiver connects to the
ECG monitor via conventional lead-wires or electrode wires of the
ECG monitor. Signals representing the electrode signals measured or
sampled on a patient are provided to the ECG monitor. The existing
ECG monitor processes the signal to output ECG data, such as ECG
vector data. Consequently, physical coupling between the patient
and the electrocardiograph or vital signs monitor is eliminated.
This enables the patient to freely ambulate while being monitored
by the ECG.
[0028] FIGS. 1 and 6 show a wireless ECG monitoring system 20. The
ECG monitoring system 20 includes an electrode connector 22, a
transmitter 24, a receiver 26 and an ECG monitor 28. Additional or
fewer components can be used, such as providing the system 20
without the ECG monitor. Alternative components can be used, such
as a strip or patch with electrodes rather than an electrode
connector 22 or a printer rather than an ECG monitor 28.
[0029] FIGS. 2A-D show electrode connectors 22 of various
embodiments used with an array of electrodes 30. The electrodes 30
comprise conductive material. For example, a foam disk with a
conductive fabric or a fabric with a conductive metal layer is
used. The electrodes 30 include a snap terminal (male, female or
both) or tab for connection to a wire. Other connectors may be
provided on the electrodes 30. The electrodes 30 are positioned for
ECG monitoring, such as positioned for hexaxial-lead monitoring as
illustrated in FIGS. 2A-C. For hexaxial-lead monitoring, the
electrodes 30 are positioned in left and right arm positions and
right and/or left leg positions. With these electrode positions, up
to seven leads can be monitored (e.g. Lead I, II, III, aVL, aVR,
aVF and chest positions). Other positions of electrodes can be
used, such as associated with precordial (e.g. V1-V6) or
combinations of hexaxial and precordial (e.g. "12-lead"
monitoring). The electrodes 30 are attached to the patient with
conductive hydrogel or other adhesives. The electrodes 30 and/or
the electrode connector 22 are disposable or reusable.
[0030] The electrode connector 22 includes a plurality of
expandable arms 32 and a transmitter 24. The expandable arms 32
comprise polypropylene or polyethylene fabric with an electrically
conductive element such as a wire 36 and an electrode joiner 38 as
shown in FIG. 3. In one embodiment, the expandable arm 32 is formed
from Kapton or Mylar, manufactured by DuPont, a cloth, a fabric or
another flexible material. Multiple layers of dielectric, and or
electrically or magnetically conductive material can be used to
shield the wire 36. Alternatively, no shielding is provided. Fabric
or other material can be attached to one or both sides of the
expandable arm 32, such as to provide comfort for a patient.
[0031] The expandable arm 32 of one embodiment comprises memoryless
material, such as the materials discussed above. The expandable arm
32 is die cut in a serpentine pattern as shown in FIG. 3. The
expandable arm 32 expands by releasing or breaking connections
between portions of the serpentine pattern. When expanded, a
portion or all of the expandable arm 32 is extended. Where only a
portion of the expandable arm 32 is extended, another portion
remains folded or unbroken. Pressure on the electrode 30 from
elastic or stretchable material is avoided, providing for more
stable connection of the electrode 30 to the patient. The
expandable arm 32 also allows for extension as needed without extra
extension and resulting loose material to be tangled or provide
discomfort. In alternative embodiments, a stretchable or elastic
expandable arm 32 is used. In yet other alternative embodiments, a
non-expandable arm is used.
[0032] The electrical conductor or wire 36 in the expandable arm 32
preferably comprises a conductor printed on the Mlyar, Kapton or
other flexible dielectric material. The printed conductor is
flexible, providing electrical connection between the electrode 30
and the transmitter 24 whether expanded or unexpanded. In
alternative embodiments, the wire 36 comprises a thread of copper
or another conductive material. In yet other embodiments, the wire
comprises a coaxial cable. One or more wires 36 are provided for
each electrode 30. For some expandable arms 32, one wire 36
electrically connects from one electrode 30 to the transmitter 24
or another expandable arm 32. For other expandable arms 32, a
plurality of wires 36 connect from a respective plurality of
electrodes 30 on the same and/or another expandable arm 32.
[0033] The electrode joiner 38 comprises a clip (e.g. alligator
clip), snap terminal, or connector (male, female or both), adhesive
tab or other device for electrically and physically joining the
electrode 30 to the expandable arm 32. As shown in FIG. 2D, a
plurality of electrode joiners 38 can be used on one expandable arm
32. In other embodiments, one electrode joiner 38 is provided at an
end or other portion of the expandable arm 32. If one electrode 30
malfunctions, only the electrode 30 is removed and replaced. The
electrode connector 22 is kept.
[0034] The other end of the expandable arm 32 connects with other
expandable arms 32 or the transmitter 24. The plurality of
expandable arms 32 are connected in any of various configurations,
such as a spiral configuration shown in FIGS. 2A and 2B. The
expandable arms 32 releasably or fixedly connect from a hub 40. In
the embodiment of FIG. 2A, one expandable arm 32 includes wires for
all or a sub-set of the electrodes 30 to electrically communicate
with the transmitter 24. The transmitter 24 is spaced away from the
hub 40, such as being positioned on an arm band (shown), or on
another location on the patient. For example, FIG. 6 shows the
transmitter 24 held to the patient with an arm band 74 comprising
neoprene or other fabric. In the embodiment of FIG. 2B, the
transmitter 24 is positioned on the hub 40.
[0035] The hub 40 comprises the same material as the expandable
arms 40, such as from using a continuous sheet to form the hub 40
and expandable arms 32. In other embodiments, the hub 40 comprises
the same or different material with releasable connectors for
electrically and physically connecting with the expandable arms 32.
For example, the hub 40 comprises plastic or other material with
plurality of conductive snap terminals for connecting with the
expandable arms.
[0036] Another configuration is a "7" or "L" configuration, such as
the embodiment shown in FIG. 2C. One of the electrode positions
generally corresponds to the hub 40, and expandable arms 32 expand
from the hub 40. Other alternative configuration embodiments
include "C" or "U" shapes with multiple hubs.
[0037] Yet another configuration is shown in FIG. 2D. A belt 42
connects with a plurality of expandable arms 32. The belt 42
comprises neoprene, non-woven polypropylene or polyethylene fabric
or other materials. One or more pockets or connectors for the
transmitter 24, other electrical components, batteries, displays,
or other devices are provided on the belt 42. In one embodiment
shown in FIG. 4, the belt 42 is formed to fasten or stretch around
a waist of the patient, but arm, neck, chest or leg belts can be
used. One or more of the expandable arms 32 releasably connects
with the belt 40. In one embodiment, the belt 40 includes separate
connectors 44 for each electrode position. In other embodiments,
one or more of the connectors 44 on the belt 40 include separate
electrical contacts for electrically connecting with multiple wires
36 and associated electrodes 30 on one expandable arm 32. The
connectors 44 are provided on the outer surface of the belt 42, but
can be provided in pockets. The transmitter 24 is positioned on the
belt 42 or elsewhere on the patient.
[0038] As shown in FIG. 2D, one or more of the expandable arms 32
may include one or more connectors 44 for connecting with other
expandable arms 32, forming a hub 40. For example, an electrically
conductive snap terminal or terminals connect the expandable arms.
Other connectors, such as male and female housings with clips and
wires associated with connecting multiple separate wires between
the expandable arms, can be used.
[0039] The configuration is associated with the desired ECG
monitoring. FIGS. 2A-C illustrate hexaxial positions for the
electrodes 30, such as associated with continuous monitoring.
Electrodes 30 are positioned at hexaxial positions associated with
left arm, right arm, left leg and/or right leg. Many ECG systems
use three electrode positions, but some use four or more. FIGS. 2A
and 2C show three electrode positions. FIG. 2B shows four electrode
positions. More or fewer electrode positions, such as three to five
positions, may be provided with additional electrode joiners 38
and/or expandable arms 32.
[0040] FIG. 2D shows both hexaxial and precordial positions for the
electrodes 30, such as associated with "12 lead" ECG monitoring.
Two or more expandable arms 32 connect with electrodes 30 in
hexaxial positions. One or more expandable arms 32, such as
expandable arm 46, connect with electrodes 30 in precordial
positions. In this embodiment, the precordial expandable arm 46
connects with another of the expandable arms 32 used for hexaxial
positions. The resulting hub 40 is associated with one of the
precordial electrode positions. In alternative embodiments, the hub
40 is spaced away from any electrode 30. In yet other alternative
embodiments, the precordial expandable arm or arms 46 separately
connect with the belt 42. For example, separate hexaxial and
precordial electrode connectors 76 and 78 are provided as
illustrated in FIG. 6. The precordial electrode connector 78
connects with the hexaxial electrode connector 76 or the
transmitter 24.
[0041] The hubs 40 and expandable arms 32 may include connectors 44
for adding additional expandable arms 32 or electrodes 30. For
example, two or more expandable arms 32 are positioned for
hexaxial-lead monitoring as shown in FIG. 2D without the precordial
expandable arm 46. When precordial-lead monitoring is desired,
electrodes 30 are positioned along six precordial positions, and
the expandable arm 46 is expanded and connected with the precordial
electrodes 30. The expandable arm 46 is also connected to the belt
42 or other expandable arm 32. Alternatively, different electrode
connectors 22 are used for different ECG systems or numbers of
electrodes. Since the expandable arms 32 are flexible and
expandable, the same electrode connector 22 is used for various
electrode positions as represented by the bold arrows in FIGS.
2A-D.
[0042] The transmitter 24 receives the signals from the electrodes
30. The transmitter 24 comprises a wireless transmitter or
transceiver, such as a radio, ultrasound, infrared or other
transmitter. For example, a transceiver operable according to
Bluetooth specifications (i.e. a Bluetooth transceiver) is used. In
one embodiment, the transmitter 24 comprises an application
specific integrated circuit, a processor or other circuit.
[0043] FIG. 7 shows one embodiment of the transmitter 24. The
transmitter 24 includes a plurality of electrode signal channels
80, a multiplexer 82, an analog-to-digital converter (ADC) 84, a
controller 86, a radio 88 and a battery 90. Additional, fewer or
different components can be used. The battery 90 comprises a
replaceable or rechargeable lithium battery connected to provide
power to the various components of the transmitter 24.
[0044] In one embodiment, nine electrode signal channels 80
corresponding to the typical nine electrodes used for hexaxial-lead
and precordial-lead monitoring are provided. Fewer or additional
electrode signal channels 80 can be provided. The electrode signal
channels 80 each comprise a connector 92, a filter 94, an amplifier
96, a Nyquist filter 98 and a track and hold circuit 100. The
connector 92 comprises snaps, plugs or other electrical connectors
for connecting with the wires 36. The filter 94 comprises a low
pass filter, such as for removing electromagnetic interference
signals. The amplifier 96 amplifies the signals from the electrodes
30. The Nyquist filter 98 comprises a low pass filter for removing
high frequency content of the amplified signals to avoid sampling
error. The track and hold circuit 100 enables the system to sample
all 9 channels of signals at a same or relative times so that there
is no differential error created when these signals are combined
later in a legacy ECG monitor.
[0045] The multiplexer 82 sequentially selects signals from the
electrode signal channels 80 using time division multiplexing, but
other combination functions can be used. The ADC 84 converts the
combined analog signals to digital signals for transmission. The
controller 86 controls operation of the various components and may
further process the digital signals, such as diagnosing operation,
controlling any user interface (e.g. input and/or output devices),
and detecting connection to electrodes. Preferably the controller
comprises a digital signal processor (DSP) that decimates the
digitized signals so as to lessen the bandwith required to transmit
the signals. The radio 88 modulates the digital signals with a
carrier signal for transmission. In one embodiment, the radio 88
includes a demodulator for receiving information. The controller 86
processes the received information.
[0046] In one embodiment, the transmitter 24 is operable to
minimize introducing undesired noise or signals. For example,
components are matched such that later application to a
differential amplifier in a legacy ECG monitor for determining a
heart vector is accurate. In one embodiment, the ECG vectors are
not formed by the ECG system 20, but rather by the legacy ECG
monitor. Because the ECG system 20 is essentially "in-series" with
the legacy ECG monitor, any error may produce undesirable results.
One potential source of error is differential error. This
differential error can be observed on the legacy ECG monitor when
the ECG monitor forms the ECG lead signals by combining the
individual electrode signals in the ECG monitor input stage. This
input stage comprises a difference, or differential, amplifier to
eliminate common mode interference from the signals produced at the
electrodes 30. If there is any difference in how each of the
electrode signals are processed, when the legacy ECG's differential
amplifier forms the ECG lead signals or ECG vectors an artifact
will be present. For example, in the transmitter 24 if there is a
difference in the gain of the amplifiers, a difference in the phase
shift associated with the anti-aliasing (Nyquist) filters, a
difference in how the respective track and hold circuits treat the
electrode signals, this differential error creates an artifact on
the legacy ECG monitor. One important technique to minimize this
potential source of differential error, is to choose a Nyquist
filter 98 cutoff frequency that is very high. This is because each
individual filter will have differing group delay performance, and
to mitigate that difference the frequency that this group delay
will affect is much higher than the frequency of the ECG signals,
which are about 0.05 Hz to 150 Hz. By choosing a high cutoff
frequency for the Nyquist filters 98, any mismatch in the Nyquist
filter 98 components will not affect accuracy of the individual
electrode ECG signals. For example picking a filter cutoff
frequency of 1,200 Hz mitigates this source of error. With this
approach, the individual electrode ECG signals are oversampled at
about 3,000 Hz in order to not introduce aliasing. Of course higher
filter cutoff frequencies and correspondingly higher sampling rates
may further reduce error. Lower cutoff frequencies and/or sampling
rate may be used.
[0047] Because the electrode signals are now sampled at such a high
rate, these signals may be decimated to minimize the required
transmission bandwidth. For example the digital samples are
decimated by a factor of 8 in the controller 86. Greater or lesser
rates of decimation can be used, such as decimation as a function
of the bandwidth available for transmission, the number of
electrode signals to be represented, and the Nyquist sampling rate.
In alternative embodiments, the digital data is compressed, the
electrode signals are not oversampled, or no decimation is
provided.
[0048] The selected signals are transmitted as radio or other
signals modulated with a carrier signal. Various formats for
transmission can be used, such as Bluetooth, TCP/IP, or other
formats. The controller 86 controls the acquisition and
transmission of the electrode signals. The transmitted signals
comprise data representing the signals received from the electrodes
30. In alternative embodiments, the controller 86 may also
processes the signals prior to transmission, so the transmitted
signals comprise ECG vector data. In one embodiment, the
transmitter 24 also receives control information from the receiver
26, such as instructions to resend signals.
[0049] The transmitter 24 is positioned near the patient. In the
embodiment shown in FIGS. 2A and 2C, the transmitter 24 is
positioned on the hub 40 or an expandable arm 32. In the embodiment
shown in FIG. 2B, the transmitter 24 is positioned on an arm band,
but leg, chest or other bands can be used. In the embodiment of
FIG. 2D, the transmitter 24 is positioned on the belt. Either a
pocket or a surface mount is provided for the transmitter 24. In
alternative embodiments, the transmitter 24 is positioned in a
pocket of clothing or elsewhere on the patient.
[0050] In one embodiment, the transmitter 24 is removable. For
example, clips, screws, bolts, latches or other devices releasably
hold the transmitter 24 in contact with the electrode connector 22.
Electrical contact is provided by connectors operable to withstand
electrical energy produced by a defibrillator. These connectors may
also provide the physical connection. The transmitter 24 is removed
for recharging the battery or a plug is provided on the electrode
connector 22 or the transmitter 24 for recharging the battery
without removal. The battery or the transmitter 24, like the
electrode connector 22, can be used for multiple days or multiple
times and is separately disposable to avoid costly replacement of
the entire system 20.
[0051] Referring to FIGS. 1 and 6, the receiver 26 receives the
transmitted signals. The receiver 26 comprises a radio, infrared,
ultrasound or other receiver. An application specific integrated
circuit, digital signal processor or other circuit for receiving
signals from the transmitter 24, decoding the received signals, and
generating representative electrode signals is used. In one
embodiment, the receiver comprises a transceiver for two-way
communication with the transmitter 24. For example, a transceiver
operable pursuant to the Bluetooth specification is provided.
[0052] FIG. 8 shows one embodiment of the receiver 26. The receiver
26 includes a radio 110, a controller 112, a digital-to-analog
converter (DAC) 114, a demultiplexer 116, a plurality of electrode
signal channels 118 and a battery or power supply 120. Additional,
fewer or different components can be used. Preferably, the power
supply 120 comprises a replaceable or rechargeable battery or other
power source connected to provide power to the various components
of the receiver 26.
[0053] The radio 110 demodulates the received signals for
identifying digital data representing the combined electrode
signals. In one embodiment, the radio 110 also includes a modulator
for transmitting control information. The controller 112 controls
operation of the various components and may further process the
signals from the radio 110, such as interpolating data, converting
the signals to digital information, generating control signals for
the transmitter 24, operating any user interface, operating any
user output or input devices, and diagnosing operation of the
system 20. Preferably, the controller 112 in the receiver 26
interpolates the electrode signals to return the effective sample
rate to about 3 kHz or another frequency. This enables the
reconstruction filters to have a cutoff frequency many times the
bandwidth of the electrode signals, thus minimizing any differences
in group delay at the frequencies of interest, i.e. less than 150
Hz. The DAC 114 converts the digital signals to analog signals. The
demultiplexer 116 separates the individual regenerated electrode
signals onto the separate electrode signal channels 118.
[0054] In one embodiment, nine electrode signal channels 118
corresponding to the typical nine electrodes used for hexaxial-lead
and precordial-lead monitoring. Fewer or additional electrode
signal channels 118 can be provided. The electrode signal channels
118 each comprise a sample and hold circuit 120, a filter 122, an
attenuator 124 and a connector 126. The sample and hold circuit 120
is controlled by the controller 112 so that the converted electrode
signals appear simultaneously on each electrode signal channel 188.
Differential error may be mitigated. Other embodiments may include
individual DAC's that provide the signals substantially
simultaneously. The filter 122 comprises a low pass reconstruction
filter for removing high frequency signals associated with the DAC
conversion process. The attenuator 124 comprises an amplifier for
decreasing the amplitude to a level associated with signals at the
electrodes 30, that were earlier amplified in the amplifiers 96 of
the transmitter 24. This results in a unity system gain so as not
to introduce error between the electrodes and the legacy ECG
monitor. Other gains may be used. The connector 126 comprises
posts, snaps, plugs, tabs or other electrical connectors for
connecting with the lead wire set 70.
[0055] The controller 112 sets the demodulation frequency in
response to input from the user input device or memory, or the
demodulation frequency is fixed. In one embodiment, the user input
comprises buttons associated with manual frequency control, with
preprogrammed channels, with numbers or characters, with possible
transmitters 24 or other input devices for selecting a demodulation
frequency. The receiver 26 electrically connects to the ECG monitor
28.
[0056] FIG. 6 shows one embodiment of the wireless ECG system 20
where the wires 70 from a standard ECG monitor 28 attach to the
electrically conductive posts 72 or other connectors on the
receiver 26. The wires 70 comprise a lead-wire set, cable or
electrode connectors from or for the ECG monitor 28. The posts 72
are labeled as electrodes 30, and the wires 70 are connected with
corresponding outputs on the receiver 26. The receiver 26 outputs
signals as if from the corresponding electrodes 30 for processing
by the ECG monitor 28. In alternative embodiments, the receiver 26
includes wires for connecting with the ECG monitor 28.
[0057] In one embodiment, the receiver 26 physically connects to
the ECG monitor 28. For example, latches, clips or straps on the
receiver 26 connect the receiver 26 to the ECG monitor 28. In
alternative embodiments, the receiver 26 connects to an equipment
pole or wall or is free standing. The receiver 26 may be releasably
attached. When a patient is moved, the receiver 26 may be detached
and moved adjacent a different ECG monitor. Alternatively,
different receivers 26 operate with the same transmitter 24, so
another receiver 26 is programmed to receive signals from the
transmitter 24 on the patient.
[0058] The ECG monitor 28 comprises one or more of a bedside
monitor, a transport monitor or a discrete (i.e. diagnostic)
monitor. Bedside and transport monitors are used for continuous
monitoring, such as associated with hexaxial-lead monitoring. A
discrete monitor typically is used periodically for analysis, such
as associated with "12-lead" monitoring or obtaining multiple
vectors associated with precordial and/or hexaxial leads. The ECG
monitor 28 processes the electrode signals as if the signals where
received directly from the electrodes 30. Neither of the
transmitter 24 or receiver 26 includes differential amplifiers for
determining a heart vector associated with two electrodes.
[0059] Some ECG monitors 28 test for failure or malfunction of
electrodes 30. For example, a signal is output on the lead wire to
the electrode 30 or a direct current level associated with the
signal from the electrode 30 is monitored. To continue to provide
this functionality, the wireless ECG system 20 tests for electrode
failure or malfunction and indicates the results to the ECG monitor
28. For example, the transmitter 24 performs the same or similar
tests as the ECG monitor 28. In other embodiments, the transmitter
24 or receiver 26 determines whether the ECG signal is within an
expected range. For example, the controller 112 (FIG. 8) compares
the digital electrode signals, such as after interpolation, to
maximum and minimum thresholds. If either threshold is exceed by a
particular number of samples or for a particular time, a lead-off
or faulty electrode 30 is indicated. When one or more samples are
subsequently within hysteresis limits of the thresholds, then an
error is no longer indicated. When a lead-off condition is
indicated, the receiver 26 opens an analog switch or, alternatively
does not generate a signal for the output corresponding to the
malfunctioning or failed electrode 30. As a result, the ECG monitor
28 indicates a failure of the electrode 30. If the transmitter 24
and receiver 26 are out of radio communication range, a lead-off
condition is presented to the ECG monitor 28.
[0060] The ECG monitoring system 20 is used for continuous
hexaxial-lead or occasional precordial-lead or both hexaxial-lead
and precordial-lead monitoring. FIG. 5 shows the acts representing
use of the system 20.
[0061] In act 50, the electrodes 30 are positioned on the patient.
For example, electrodes 30 are positioned in hexaxial positions,
precordial positions or combinations thereof.
[0062] In act 52, the electrode connector 22 and transmitter are
positioned. The expandable arms 32 are expanded, such as expanding
a portion or all of the expandable arms 32. Another portion of the
expandable arms 32 may remain folded or unexpanded. The expandable
arms 32 are expanded to reach one or more electrodes.
[0063] In act 54, the electrode connector 22 is connected with the
electrodes 30. For example, the expandable arms 32 are releasably
connected with one or more electrodes 30, such as snapping or
clipping to the electrodes 30. Expandable arms 32 may also be
connected with other expandable arms 32, hubs 40, the transmitter
24, and/or the belt 42. In an alternative embodiment, the
electrodes 30 are connected with the electrode connector 22 prior
to positioning the electrodes 30 and expanding the expandable arms
32.
[0064] In act 56, the transmitter 24 is operated or turned-on. In
one embodiment, a switch on the transmitter 24 activates the
transmitter. In alternative embodiments, connection to one or more
of the wires 36, expandable arms 32, electrode connecter 22 and/or
electrodes 30 activates the transmitter 24. In response, the
transmitter 24 radiates a signal representing the electrode
signals.
[0065] In act 58, the receiver 26 is programmed. A code
corresponding to the transmitter 24 is entered, or a channel (i.e.
frequency) is selected. In an alternative embodiment, the receiver
26 searches a plurality of frequencies for an appropriate signal,
such as a signal in an expected format or with a particular code.
If more than one signal is identified, an output may be provided
for user selection of the appropriate signal. A visual or audible
output indicating reception of a signal may be provided.
[0066] In act 60, wires or electrode connectors from the ECG
monitor 28 are connected to the receiver 26. In alternative
embodiments, act 60 occurs before any of acts 50, 52, 54, 56 or
58.
[0067] In act 62, the ECG device, such as a monitor, printer or
memory, is activated. Analog or digital signals corresponding to
signals at the electrodes 30 are received by the ECG device from
the receiver 26. The ECG device processes the signals to generate
ECG data, such as one or more heart vectors.
[0068] In one embodiment, a light emitting diode, a light pipe or
multiple light emitting diodes, or other output device is provided
on the transmitter 24 and/or one or more of the expandable arms 32.
The output device indicates electrical operation of the transmitter
or conductance of signals by the wire 36. Different output devices
may represent improper operation. In one embodiment, extending the
expandable arm 32 activates operation of the output device or
devices.
[0069] The wireless ECG system 20 provides for fewer artifacts due
to wire movement, allows the patient to wear clothing without
interfering with wires, and provides less psychological
intimidation of the patient due to wire connections to a machine.
The electrodes 30 are less likely to disconnect because of lower
mass or force due to wires connected to the ECG monitor 28. The
wireless ECG system 20 is usable with many different ECG monitors
28 and electrodes 30. Faster setup when a patient is transferred
and connected to a different ECG monitor 28 is provided since the
same electrodes 30 already positioned on the patient can be used.
Since the electrodes 30 are not repositioned due to a transfer, the
ECG monitor output is more comparable to the output of previous ECG
monitors. If an electrode 30 fails because of patient movement or
perspiration, the electrode can be replaced without replacing the
electrode connector 22 or other electrodes 30.
[0070] While the invention has been described above by reference to
various embodiments, it will be understood that many changes and
modifications can be made without departing from the scope of the
invention. For example, the transmitter and receiver may each
comprise transceivers for two-way communication and control.
Various aspects can be used with or without other aspects, such as
using the electrode connector 22 with a transmitter that processes
the electrode signals into ECG vector data rather than transmitted
signals representing the electrode signals. Another example is
transmitting the electrode signals but using a different electrode
connector, strip, patch or mere wires. Other biomedical systems,
such as temperature or blood pressure, can be additionally or
alternatively monitored using the systems and methods discussed
above.
[0071] It is therefore intended that the foregoing detailed
description be understood as an illustration of the presently
preferred embodiments of the invention, and not as a definition of
the invention. It is only the following claims, including all
equivalents that are intended to define the scope of this
invention.
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