Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: REMOTE MONITORING OF CARDIAC ELECTRICAL ACTIVITY
FIELD OF THE INVENTION
[0001] This invention relates to remote health monitoring. In
particular, it relates to a device whereby cardiac signals
such as human heart rate, electrocardiogram (ECG) and other
vital signs may be acquired by a patient and transmitted to a
remote location.
BACKGROUND TO THE INVENTION
[0002] In the field of cardiology, devices exist that use
telephones to transmit a patient' s ECG data from the patient' s
location to a monitoring clinic or doctor's office. Examples
include so-called cardiac loop event recorders. These are
connected via cables to ECG gel electrodes, quasi-permanently
attached to the patient. These devices are able to record ECG
data of the patient during ar.rhythmias.
[0003] Other hand-held recorder devices exist that possess
permanent, metallic electrodes arranged in a planar
configuration, all on one side of the device. These must be
temporarily held by the patient against the patient's chest
skin in order to pickup the cardiac signal.
[0004] Still other devices of the prior art require the
patient's two thumbs to be placed on independent, co-planar
electrodes on one face of the device.
[0005] Traditionally, all these types of devices transmit
stored patient ECG data to the monitoring clinic or the
doctor's office using a conventional telephone. This is
accomplished via an audio signal, which the device modulates
with the patient's ECG and which is transmitted through the
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telephone and subsequently de-modulated by a modem or
receiver/adapter at the clinic or doctor's office.
[0006] Cardiac monitors based on the co-planar electrode
arrangements have also been proposed on the back of a cell
phone. One example is US Patent 6,485,416 (Nov 2002). These
require the user to hold the device against the bare skin of
the chest, thus not enabling simultaneous vocal communication
while monitoring.
[0007] U.S. Patent 5,7'72,586 issued to Nokia Mobile Phones
htd. describes the transmission of blood glucose data by cell
phone. Sensor electronics are restricted to the battery case
location and no special consideration is given to ECG.
[0008] US Patent 6,102,856 "Wearable Vital Signs Monitoring
System" (Aug 2000) specifies a wireless transmission device to
be worn on the chest with various sensors affixed to the
patient.
[0009] US Patent 5,544,661 entitled "Real-Time Ambulatory
Patient Monitor" (Aug 1996) describes a portable device
possessing ECG and photo-plethysmograph (blood oxygen) sensors
connected to the patient and providing "wireless wide-area"
communications.
[0010] In all the above cases, bio-signal monitoring is not
accomplished in t'_ne posture of normal speaking or
communications over a phone handset. In most of the above
cases, multiple devices and sensors are required, making the
devices more cumbersome to operate than an ordinary telephone
or cell phone.
[0011] US Patent 6, 549, 756 (April 15, 2003) describes portable
palm-sized personal data communications devices and cellphones
fitted with non-co-planar blood-flow sensors. These are
designed to maximize the number of sensors in contact with the
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hand of the user holding the device. This allows for bio-
signal monitoring while the device is in normal use for data
communications. However the bio-sensors described are
incapable of ECG pickup and, due to human body physiology, use
of multiple contact points on a single hand of a person as
described does not propose acquisition of bio-signals while
the telephone unit is positioned for voice communication.
[0012] No prior art telephonic device has been proposed that
enables ECG or bio-signal collection from the user while the
user is holding the device in the position for ordinary use
for communications.
[0013] It would be desirable for a device to detect and
transmit bio-signals such as ECG while being positioned for
use essentially as an ordinary telephone. Such a system would
offer convenience and would enable real-time or simultaneous
bio-signal transmission and verbal communications with the
health practitioner, thus providing the patient with instant
feedback while saving millions of dollars in hea.lthcare costs .
[0014] A consideration in realizing this goal is that, during
normal communications, hand-held telephonic devices typically
contact the user' s body at one hand and at the head. However,
commercial cardiac pickup devices of the prior art do not use
the head as a pickup location for ECG.
[0015] It has been known in the field of medical research that
a person's head can be used as one locus for the pickup of ECG
signals. In order to generate a difference potential due to
cardiac activity, a second pickup electrode must be placed on
the torso, arm or leg of the person. Such an arrangement may
also provide a differential-type pickup with common mode noise
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rejection. Due to human body physiology, electrodes placed on
the head and left arm produce ECG-like signals on most people.
[0016] Other physiologic signals can also be acquired from the
head. These include plethysmograph (blood oxygen and pulse)
from the ear lobe, and temperature sensing from the inner ear.
[0017] The simultaneous handling of bio-signals, once
acquired, and audio signals through a telephone or cellular
phone can be performed by known technology in a number of
ways. These can be classified into four broad categories:
Analog Half-Duplex, Analog Full Duplex, Digital Half-Duplex,
and Digital Full-Duplex.
[0018] A number of present technologies and emerging digital
data systems and cellular phone systems enable alternating, or
simultaneous, real-time voice and data transmission. An
opportunity exists for these technologies to be combined to
produce a new and effective system for -the remote transmission
of bio-signals with the added feature of providing real-time
voice telephonic communication between the patient and medical
professionals even though they are located at a distance.
[0019] The invention in its general form will first be
described, and then its implementation in terms of specific
embodiments will be detailed with reference to the drawings
following hereafter. These embodiments are intended to
demonstrate the principle of the invention, and the manner of
its implementation. The invention in its broadest and more
specific forms will then be further described and defined in
each of the individual claims, which conclude this
specification.
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SUMMARY OF THE INVENTION
[0020] The invention is directed to a hand-held, vital signs
monitoring device incorporated with, or accompanying a
telephone handset or cell phone.
[0021] The invention is particularly suited to a hand-held
sensor system incorporating one of a variety of head-source
bio-sensors, including sensors for blood oxygen, pulse, body-
temperature, and ECG incorporated with or accompanying a
telephone handset or cell phone.
[0022] The invention provides a means by which these signals,
including the head-to-arm ECG signal, may be conveniently
acquired and telephonically transmitted by the patient via a
single, hand-held device, in the form of a telephone handset
or a cell phone, while the device is in the position for
ordinary communications. "Telephonic communications" as used
herein includes transmission of data over a system that will
accommodate acoustic, e.g. voice, communications.
[0023] The invention therefore enables the simultaneous or
alternate communication of bio-data and voice without the need
for any interruption arising from repositioning of the device.
[0024] According to one aspect, the invention can be realized
as a specially designed telephone handset or a specially
designed cell phone. According to another. aspect, the
invention can be realized as a harness, case, attachment, or
glove designed to be carried by an existing telephone handset
or an existing cell phone.
[0025] In both aspects, the invention addresses a specially
designed telephone handset or cell phone, or a harness or case
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designed to be carried by an existing telephone handset or an
existing cell phone, which device embodies:
a) a first sensor to be carried on the outer surface of the
device in order to establish a first contact with the
user's head and receive bio-signals through such first
contact;
b) a pickup signal conditioning circuit carried by the
device connected to the first sensor to condition
received signals for telephonic communication; and
c) a telephonic communication circuit connected to the
signal conditioning circuit to provide a telephonic
signal corresponding to the bio-signal data for
telephonic communication,
whereby the simultaneous or alternate communication of bio
data and voice may occur without the need for any interruption
arising from repositioning of the device.
[0026] For the purpose of ECG, a second sensor is positioned
on another portion of the surface of the device to establish
a second contact with the user's hand to also effect the
acquisition of bio-signals through such second contact. Both
the first and second sensors may then serve as ECG pickup
electrodes for delivery of bio-signals to a differential
amplifier contained within the signal conditioning circuit.
In addition to the two pickup electrodes, the device of the
invention for ECG may also carry a third electrode to serve as
a reference electrode, preferably ohmic with a low coupling
impedance, positioned to contact either the user' s head or the
hand when the device is in use and connected to the common for
such circuit. The reference electrode serves to establish a
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reference voltage (ground) for the differential amplifier and
improves common mode noise rejection. This reference
electrode may be mounted proximately to either the first or
the second pickup electrode.
[0027] The inventicn is suitable for ECG but is not restricted
to ECG. Other bio-sensors can be incorporated to acquire bio-
signals e.g. monitoring of blood oxygen, pulse, and ear
temperature etc. The invention therefore enables the pickup,
and real-time assessment of the patient°s vital signs.
Instant feedback can be provided to the patient, as can
simultaneous or alternate bio-signal and voice communication
during apparently normal telephonic exchange without the need
for any interruption arising from repositioning of the device.
[002$] According to the invention, the sensed bio-signal is
provided to the conditioning circuit, which conditions it to
provide the signal, or a surrogate of said signal, for
telephonic transmission. Conditioning may include a
differential amplifier, a filter, an analysis circuit based
upon algorithms to partially analyse the bio-signal before
transmission, a compression circuit, a digitising circuit and
other known signal manipulating means. Memory may also be
provided for delayed transmission of signals. Accordingly,
variants of the invention can transmit either the bio-signal,
in analog or digitised form, or surrogates for, the bio-signal,
in real time or on a delayed basis.
[0029] A memory in the conditioning circuit may be used to
store signals for delayed transmission. Conveniently, an
archive memory may be used to store standard bio-data such as
standard ECG trace of the user, acquired when the user is
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healthy. This archived bio-signal may then be sent to distant
medical professions, along with contemporary signals, when the
user/patient is having a crisis.
[0030] When the invention is incorporated into a case,
harness, or glove designed to be carried by an existing
telephone or cell phone, either an acoustic coupling means or
an electrical connection may be employed in order to convey
the bio-signal into the telephonic transmission portion of the
combined device. In the case of use of a cell phone for ECG,
the first and second pickup electrodes, the reference
electrode (preferentially all ohmic), and the electrical
circuitry of the invention may readily be carried within a
case or attachment, coupled to the cell phone by an internal
or external connector which extends from the circuitry of the
invention to the microphone or data port of the cell phone to
permit inclusion of the bio-signal into the cell phone's
telephonic communications. A control switch may allow user
control to toggle the telephonic communication between bio-
signal and voice-only transmissions. Alternately, bio-signal
and voice telephonic transmissions, including simultaneous
transmissions, may be effected by any one of known means for
combining voice and data communication, as further elaborated
below.
[0031] The electrode placement of the invention on the hand-
held telephonic device provides for bio-signal pickup during
the course of normal communications. Thus the head-facing
sensor is on the same side of the device as the customary
earpiece. This enables single-hand operation and simultaneous
or alternate, near-simultaneous bio-signal and voice
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communication through the telephone or cell phone, thus
allowing real-time data transmission and telephonic feedback
between the patient and the health care practitioner.
[0032] A preferred type of pickup electrodes for ECG are
active-type electrodes designed to minimize contact potentials
and motion artifact as described, for example, in PCT patent
applications PCT/CA00/00981 and PCT/CA03/00426, the contents
of such applications being adopted herein by reference.
[0033] The foregoing summarizes the principal features of the
invention and some of its optional aspects. The invention may
be further understood by the description of the preferred
embodiments, in conjunction with the drawings, which now
follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[003] Figure 1 is an illustration of a cell phone of the
invention showing locations for the pickup electrodes, the
ground reference electrode and the analysis circuit.
[0035] Figure 2 is an illustration of a case of the invention
designed to fit onto a pre-existing cell phone.
[0036] Figure 3 is a schematic depiction showing a patient
transmitting bio-signals obtained between the hand and ear as
in normal telephonic communications.
[0037] Figure 4 is a schematic showing the electrical circuit
for an "active" ohmic electrode.
[0038] Figure 5 is a schematic showing the electrical circuit
for two "active" ohmic electrodes feeding a signal to a
differential amplifier.
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[0039] Figure 6 is a functional block diagram of one version
for the electronics of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0040] In Figure 1 a cell phone 1 of the invention is equipped
as a cardiac monitoring device, possessing a forward facing,
first, head-contacting sensor 2 positioned to contact the face
or ear of the user. While sensor 2 is shown in Figure 1 as
being below the earpiece 17 on the cell phone, it may
otherwise surround such earpiece 17 or be positioned elsewhere
on the cell phone 1 to conveniently contact the user's head
during or between telephonic transmissions. To capture ECG
signals, a second, side or rear.-facing, hand-contacting sensor
3 is positioned to contact the left hand or thumb of the user.
And preferably, a reference electrode 4 is positioned on the
cell phone 1 to contact either the face or hand of the user.
The electrodes may be ohmic or capacitive, the reference
electrode being preferably ohmic of the active type.
[0041] It is desirable in the case where ohmic electrodes are
used for the first and second electrodes, particularly in
conjunction with a differential, common-mode noise rejection
circuit, for the body-contacting surface of such electrodes to
have a volume resistivity in the range of l0exp5 to l0exp11
ohm-cms, more preferably l0exp6 to l0exp10 ohm-cms. With such
an electrode it is desirable to feed the signal directly into
a preferably on-board, high impedance amplifier - hence
constituting an active electrode.
[0042) In Figure 2 an already-existing cell phone 1 is
provided with a harness incorporating a first, forward-facing
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sensor 2 positioned to contact the face or ear of the user; a
second, side or rear-facing sensor 3 positioned to contact the
left hand or thumb of the user; a reference electrode 4,
preferably ohmic, positioned to contact either the face or
hand of the user; and an electronic circuit 5 to condition
and/or analyse the bio-signal and to digitise and/or modulate
the bio-signal in preparation for transmission. A coupling
connector 19 delivers the bio-signal to the cell phone input
for telephonic transmission 18. Optionally, an input switch
10 may be provided to allow the user to select bio-signal data
transfer A or voice transmission B, as shown in Figure 6.
[0043] Figure 3 illustrates a device of the invention in use
by a user. When the device 1 is held to an ear as shown in
Figure 3, bio-signals are acquired from the same user posture
as in ordinary telephonic use. Use of the left hand is
preferred for ECG pickup as this produces a stronger signal
for most persons. But this is not a universal rule.
[0044] If for any reason this posture is not convenient on a
particular individual, then the invention can also be made to
operate by placing the face-oriented sensors on other body
parts such as the chest or opposed hand.
[0045] Figure 6 illustrates a functional block diagram of the
invention removed from the interior of a cell phone, or case
for clarity. The outputs from the first sensor 1, the second
sensor 2, and the reference electrode 3, are connected to the
conditioning circuit 5. Circuit 5 may include analyser means
15 to partially analyse the bio-signal. For the purpose of
ECG pickup, the analyser circuit 15 preferably includes a
differential amplifier. The analyser circuit 15 may also
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include means to derive key parameters from the bio-signal,
provide band-pass filters, interference filters and produce
outputs based on the correlation of multiple bio-signals.
[0046] The reference electrode 3 is connected to circuit 5 and
is also connected to a recommended electrical shield 14, which
overlies the circuitry of the invention in order to maximize
the rejection of unwanted electrical interference signals. It
has been found useful in some cases to overly electric shield
14 with an additional magnetic shield 11 constructed of mu-
metal foil or sheet. This further reduces interference
arising from transmission of the telephonic device.
[004?] Bio-signals that have been analysed within the circuit
may be provided to the memory 6, and subsequently to the
modulator '7 within the conditioning circuit 5 which prepares
15 the signal for submission to 'the telephonic device input 9.
The conditioned signal may be i n acoustic or electronic form. ,
electronic being indicated. Before submission to the
telephonic input 9, however, the modulated bio-signal may be
temporarily stored in a buffer memory 6, which is also
connected to a controller 8. Controller 8 controls the timing
of the data submission into the telephonic device and uses
memory 6 to prevent loss of bio-data.
[0048] Buffer memory 6 can optionally be made to store or
archive several seconds of the patient's 'normal' bio
signal. in an archive memory 6A. Such a signal can be recorded
under highly controlled conditions, such as at the doctor's
office, during the patient's optimal health condition. This
'normal' signal can be permanently stored and sent to the
doctor's office along with each real-time bio-signal
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transmission, e.g. interspersed. Such a feature would provide
the health practitioner with the user's 'standard' bio-signal,
thus assisting the practitioner in assessing the patient's
immediate status.
[0049] In the embodiment described previously wherein the
invention is in the form of a harness or case to be used with
an existing cell phone, the micro-controller 8 can be
connected to a user-activated switch 10. In this case, the
switch 10 controls a sense circuit in controller 8 which
toggles the cell phone through input 9 between of normal voice
mode and data transmission mode. The detailed functioning of
controller 8 depends on -the particular model of cell phone
utilized.
[0050] Communications over the telephonic link can be effected
in a number of electronic modes. Half-Duplex allows the
health practitioner to talk to the patient, and to instruct
the patient on when to begin and cease sending the bio-signal
information. When instructed, the patient switches back to
'normal' mode to regain control of the outgoing audio channel
and can immediately converse in a normal fashion with the
monitoring station.
[0051] It is also anticipated that the monitoring station
could control the bio-monitoring functions by sending a
specific tone or other signal through antenna 21 and link 16
to instruct the device to begin or cease sending bio-signals,
thereby removing the need for the patient to activate the
device.
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[0052] Other envisioned voice-over-data capabilities include
Full-Duplex, via time-division multiple-access, code division
multiple access or frequency division multiple access.
[0053] Other systems such as GPRS (General Packet Radio
Service), EDGE (Enhanced Data rates for GSM Evolution), High
Speed Internet, piggy-back DSL (Digital Subscriber Line) or
ADSL (Asynchronous DSL) continue to expand the possibilities
for simultaneous data and voice.
[0054] As high-speed digital systems continue to proliferate,
it is expected that more opportunities for simultaneous
transmission of medical data and voice signals will arise.
This will not be limited to cellular phone or PSTN systems,
but will also encompass cable-television, satellite, micro
cell and pico-cell communication systems. It is also
envisioned that a medical telephones could incorporate two,
separate voice and data systems that operate completely
independently. This will allow the voice portion to connect
to a PSTN system and the data portion to connect to any
available digital connection including, but not limited to,
wired connections, wireless connections, Ethernet, RS232, USB,
802.11 or blue-tooth.
[0055] Figure 4 depicts a pictorial schematic layout for an
electrode used to pickup signals originating inside a body 12
for delivery to the conditioning circuit 5. The electrical
signal inside the body can be called the body-source, as
represented by a voltage Vb. Analyzing this circuit for its
DC characteristics, the body source, along with the voltage
divider required for the pickup of the bio-signal is
illustrated in Figure 4 wherein:
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- Rs and R's are the skin resistance;
- F is the location of the body-to-electrode interface;
- Rc is the contact resistance at the interface F;
- Re is the electrode bulk resistance, anal
- Ra is the resistance across which the output signal Va
is measured.
[0056] The end of the voltage divider, opposite to the
electrode, is connected to the body through resistance Rr at
point K. An operational amplifier, IC1A, serves as the
sensing electronics.
[0057] In the case of passive electrodes connected to an ECG
machine, Ra represents the ECG machine input resistance. In
the case of active, ohmic pickup electrodes possessing an on-
board, internal buffer amplifier acting as an impedance
converter, Ra represents the combined resistance of the
sensing circuit as bridged by the sensing resistor.
(0058] In order to protect the sensing circuitry from overload
voltages, Ra may be paralleled by two parallel, reversely
oriented diodes such as diodes exemplified by Panasonic
MA198CT. Diodes D1, D2 are shown in Figure 5. At the low
signal levels provided by the pick-up electrodes, such diodes
exhibit high forward resistances, having a resistance of on
the order of 10 exp 12-13 ohms. The forward resistance of
these diodes before conduction occurs at low voltages is on
the order of 10 exp 13 ohms. By choosing diodes with a
forward breakdown voltage that is above the level of the
signal of interest, the "reset" function of the input
resistance of the high impedance amplifier can be improved.
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[0059] Figure 5 howl a differential input electronic circuit
that reduces or eliminates common mode noise. In Figure 5 two
pick-ups using operational amplifiers IClA, IC2A similar to
that of Figure 4 are used to drive a differential amplifier
IC3A which further conditions the signal for transmission by
shielded wire 20 to a further portion of the conditioning
circuit 5, and eventually to the telephonic communication
circuit of the phone. By use of this differential signal
detection circuit, common mode noise arising from the
reference electrode, the body, and external noise sources
will be minimized.
[0060, In summary, using the invention a new and useful means
for telemonitoring of patients may be provided.
CONCLUSION
[0061] The foregoing has constituted a description of specific
embodiments showing how the invention may be applied and put
into use. These embodiments are only exemplary. The
invention in its broadest, and more specific aspects, is
further described and defined in the claims, which now follow.
[0062] These claims, and the language used therein, are to be
understood in terms of the variants of the invention which
have been described. They are not to be restricted to such
variants, but are to be read as covering the full scope of the
invention as is implicit within the invention and the
disclosure that has been provided herein.
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