U.S. patent application number 10/906665 was filed with the patent office on 2005-07-07 for vital signs monitor used for conditioning a patient's response.
This patent application is currently assigned to TRIAGE WIRELESS, INCC.. Invention is credited to Banet, Matthew John, Jaime, Manuel Eduardo.
Application Number | 20050148882 10/906665 |
Document ID | / |
Family ID | 46304040 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050148882 |
Kind Code |
A1 |
Banet, Matthew John ; et
al. |
July 7, 2005 |
VITAL SIGNS MONITOR USED FOR CONDITIONING A PATIENT'S RESPONSE
Abstract
The invention provides a method for monitoring a patient,
comprising the following steps: 1) outfitting the patient with a
ambulatory blood pressure monitor that features an optical system
for measuring blood pressure without using a cuff, and a wireless
system configured to send and receive information sent from an
Internet-based system through a wireless network; 2) sending from
the Internet-based system to the ambulatory blood pressure monitor
a signal that indicates a blood pressure level; 3) comparing a
blood pressure value measured with the ambulatory blood pressure
monitor to the blood pressure level; and 4) generating a signal in
response to the comparing step.
Inventors: |
Banet, Matthew John; (Del
Mar, CA) ; Jaime, Manuel Eduardo; (Solana Beach,
CA) |
Correspondence
Address: |
MATTHEW J. BANET
11622 EL CAMINO REAL
SUITE 100
SAN DIEGO
CA
92130
US
|
Assignee: |
TRIAGE WIRELESS, INCC.
11622 El Camino Real Suite 100
San Diego
CA
|
Family ID: |
46304040 |
Appl. No.: |
10/906665 |
Filed: |
March 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10906665 |
Mar 1, 2005 |
|
|
|
10752198 |
Jan 6, 2004 |
|
|
|
Current U.S.
Class: |
600/485 ;
128/903; 128/905 |
Current CPC
Class: |
A61B 5/02 20130101; A61B
5/6832 20130101; A61B 5/002 20130101; A61B 2505/01 20130101; A61B
5/0205 20130101; A61B 5/02125 20130101; A61B 2562/16 20130101; A61B
5/0022 20130101 |
Class at
Publication: |
600/485 ;
128/903; 128/905 |
International
Class: |
A61B 005/02 |
Claims
What is claimed is:
1. A system for monitoring blood pressure, the system comprising: a
monitoring device comprising a patch sensor component that
generates an optical signal; and a processing component configured
to process the optical signal with calibration information to
obtain blood pressure information, and then compare the blood
pressure information to a pre-programmed value to generate a
signal.
2. The system of claim 1, further comprising an audio
component.
3. The system of claim 2, wherein the audio component is further
configured to receive the signal and in response generate an audio
alert.
4. The system of claim 1, further comprising a display
component.
5. The system of claim 4, wherein the display component is further
configured to receive the signal and in response display an alert
message.
6. The system of claim 1, further comprising a drug-delivery
system.
7. The system of claim 1, further comprising a wireless
transceiver.
8. The system of claim 7, wherein the wireless transceiver is
further configured to send and receive information through a
wireless network.
9. The system of claim 8, further comprising an Internet-based
system configured to send information through the wireless network
to the wireless transceiver, and receive information through the
wireless network from the wireless transceiver.
10. The system of claim 8, wherein the Internet-based system is
further configured to send information describing a blood pressure
level to the processing component.
11. A method for monitoring a patient, comprising the following
steps: outfitting the patient with a ambulatory blood pressure
monitor comprising an optical system that measures blood pressure
without using a cuff, and a wireless system configured to send and
receive information sent from an Internet-based system through a
wireless network; sending from the Internet-based system to the
ambulatory blood pressure monitor a signal that indicates a blood
pressure level; comparing a blood pressure value measured with the
ambulatory blood pressure monitor to the blood pressure level; and
generating a signal in response to the comparing step.
12. The method of claim 11, further comprising a step for
generating an audio alert in response to the signal.
13. The method of claim 12, wherein the audio alert indicates to
the patient that their blood pressure value is above or below the
blood pressure level.
14. The method of claim 12, further comprising a step for
generating a visual alert in response to the signal.
15. The method of claim 14, wherein the visual alert indicates to
the patient that their blood pressure value is above or below the
blood pressure level.
Description
[0001] This application is a continuation-in-part application of
U.S. patent application Ser. No. 10/752,198, filed on Jan. 6,
2004.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] The present invention relates to medical devices for
monitoring vital signs such as heart rate, pulse oximetry, and
blood pressure, and using this information to condition a patient's
response.
DESCRIPTION OF THE RELATED ART
[0004] Pulse oximeters are medical devices featuring an optical
module, typically worn on a patient's finger or ear lobe, and a
processing module that analyzes data generated by the optical
module. The optical module typically includes first and second
light sources (e.g., light-emitting diodes, or LEDs) that transmit
optical radiation at, respectively, red (.lambda..about.630-670 nm)
and infrared (.lambda..about.800-1200 nm) wavelengths. The optical
module also features a photodetector that detects radiation
transmitted or reflected by an underlying artery. Typically the red
and infrared LEDs sequentially emit radiation that is partially
absorbed by blood flowing in the artery. The photodetector is
synchronized with the LEDs to detect transmitted or reflected
radiation. In response, the photodetector generates a separate
radiation-induced signal for each wavelength. The signal, called a
plethysmograph, varies in a time-dependent manner as each heartbeat
varies the volume of arterial blood and hence the amount of
transmitted or reflected radiation. A microprocessor in the pulse
oximeter processes the relative absorption of red and infrared
radiation to determine the oxygen saturation in the patient's
blood. A number between 94%-100% is considered normal, while a
value below 85% typically indicates the patient requires
hospitalization. In addition, the microprocessor analyzes
time-dependent features in the plethysmograph to determine the
patient's heart rate.
[0005] Pulse oximeters work best when the appendage they attach to
(e.g., a finger) is at rest. If the finger is moving, for example,
the light source and photodetector within the optical module
typically move relative to the hand. This generates `noise` in the
plethysmograph, which in turn can lead to motion-related artifacts
in data describing pulse oximetry and heart rate. Ultimately this
reduces the accuracy of the measurement. Various methods have been
disclosed for using pulse oximeters to obtain arterial blood
pressure values for a patient. One such method is disclosed in U.S.
Pat. No. 5,140,990 to Jones et al., for a `Method Of Measuring
Blood Pressure With a Photoplethysmograph`. The '990 patent
discloses using a pulse oximeter with a calibrated auxiliary blood
pressure monitor to generate a constant that is specific to a
patient's blood pressure. Another method for using a pulse oximeter
to measure blood pressure is disclosed in U.S. Pat. No. 6,616,613
to Goodman for a `Physiological Signal Monitoring System`. The '613
patent discloses processing a pulse oximetry signal in combination
with information from a calibrating device to determine a patient's
blood pressure.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention provides a cuffless blood-pressure
monitor that features a behavior modification system. The blood
pressure monitor is typically worn on a patient's head and makes a
transdermal, optical measurement of blood pressure, which it then
sends to a processing component (e.g., a PDA). The processing
component preferably features an embedded, short-range wireless
transceiver and a software platform that displays, analyzes, and
then transmits the information through a wireless network to an
Internet-based system. This system generates an audio or visual
alarm when the patient's blood pressure trends high, and thus the
patient may modify their behavior through conditioned response. In
addition, a medical professional can continuously monitor a
patient's blood pressure during their day-to-day activities.
Monitoring patients in this manner minimizes erroneous measurements
due to `white coat syndrome`, increases the accuracy of a
blood-pressure measurement and additionally allows patients to
modify behavior to lower blood pressure while wearing the
device.
[0007] The invention has many advantages. In particular, one aspect
of the invention provides a system that continuously monitors a
patient's blood pressure using a cuffless blood pressure monitor
and an off-the-shelf mobile communication device. Information
describing the blood pressure can be viewed using an Internet-based
website, using a personal computer, or simply by viewing a display
on the mobile device. Blood-pressure information measured
continuously throughout the day provides a relatively comprehensive
data set compared to that measured during isolated medical
appointments. This approach identifies trends in a patient's blood
pressure, such as a gradual increase or decrease, which allows for
the patient to view and conditionally respond to high blood
pressure through behavior modification such as breathing exercises.
The monitor can also characterize the patient's heart rate and
blood oxygen saturation using the same optical system for the
blood-pressure measurement. This information can be wirelessly
transmitted along with blood-pressure information and used to
further diagnose the patient's cardiac condition. The monitor is
small, easily worn by the patient during periods of exercise or
day-to-day activities, and makes a non-invasive blood-pressure
measurement in a matter of seconds. The resulting information has
many uses for patients, medical professionals, hospitals, insurance
companies, pharmaceutical agencies conducting clinical trials, and
organizations for home-health monitoring.
[0008] In one aspect, the invention provides a system for measuring
blood pressure from a patient that features: 1) an optical module
configured to be worn on (or in) the patient's head that includes
at least one optical source and a photodetector; 2) a calibration
source configured to make a blood pressure measurement; and, 3) a
processing module configured to: i) receive a first signal from the
optical module; ii) receive a second signal from the calibration
source; iii) process the first and second signals to generate a
calibration table; and iv) receive a third signal from the optical
module and compare it to the calibration table to determine the
patient's blood pressure.
[0009] The preferred invention includes a response alert system
designed to alert the patient when escalated vital signs reach
dangerously harmful levels. The alert system alerts the patient
when blood pressure levels reach dangerous levels caused by stress
and anxiety. Each patient's blood pressure level parameters are set
during the time of calibration by a physician.
[0010] In embodiments, the blood pressure monitor features a
head-worn clip that includes the optical module (e.g., a
photodetector and first and second LEDs that emit, respectively,
red radiation and infrared radiation). The optical calibration
source is typically a cuff-based blood pressure module that
includes a cuff and a pump worn around the patient's arm. In other
embodiments, the optical module includes a short-range wireless
transmitter configured to send signals to the processing module,
which in turn may include a matched short-range wireless
receiver.
[0011] The short-range wireless transceiver preferably operates on
a wireless protocol such as Bluetooth.TM., 802.15.4 or 802.11. The
long-range wireless transmitter preferably transmits information
over a terrestrial, satellite, or 802.11-based wireless network.
Suitable networks include those operating at least one of the
following protocols: CDMA, GSM, GPRS, Mobitex, DataTac, iDEN, and
analogs and derivatives thereof.
[0012] In addition, the cuffless blood pressure-measuring device of
the invention combines all the benefits of conventional cuff-based
blood-pressure measuring devices without any of the obvious
drawbacks (e.g., restrictive, uncomfortable cuffs). Its measurement
is basically unobtrusive to the patient, and thus alleviates
conditions, such as a poorly fitting cuff, that can erroneously
affect a blood-pressure measurement. The device is small and makes
a non-invasive blood-pressure measurement in a matter of seconds.
An on-board or remote processor can analyze the time-dependent
measurements to generate statistics on a patient's blood pressure
(e.g., average pressures, standard deviation, beat-to-beat pressure
variations) that are not available with conventional devices that
only measure systolic and diastolic blood pressure.
[0013] These and other advantages of the invention will be apparent
from the following detailed description and from the claims.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0014] FIG. 1 is a semi-schematic diagram of a method for
developing a conditioned response that utilizes the cuffless
ambulatory blood-pressure monitor of the invention;
[0015] FIGS. 2A and 2B are semi-schematic views of the cuffless
ambulatory blood-pressure monitor of FIG. 1 featuring a head-band
with an optical system and a wireless hub connected, respectively,
by a cable and short-range wireless connection;
[0016] FIG. 3 is a semi-schematic view of a calibration process
used with the ambulatory blood-pressure monitor of FIGS. 2A and
2B;
[0017] FIG. 4 is a schematic view of an Internet-based system that
operates with the ambulatory blood-pressure monitor of FIGS. 2A and
2B;
[0018] FIG. 5A is a schematic top view of an adhesive patch sensor
that measures blood pressure according to the invention;
[0019] FIG. 5B is a schematic, cross-sectional view of the patch
sensor of FIG. 1A; and
[0020] FIG. 6 is a graph of time-dependent optical and electrical
waveforms generated by the patch sensor of FIG. 5A.
DETAILED DESCRIPTION OF THE INVENTION
[0021] FIG. 1 shows a semi-schematic diagram illustrating a
conditioned response alert system 8 that features an ambulatory
blood pressure monitor (ABPM) according to the invention. In
preferred embodiments, a physician prescribes to a patient an ABPM
that identifies harmfully high blood pressure levels using the
conditioned response alert system 8. While outfitting the patient,
the physician sets vital signs parameter limits, e.g. blood
pressure limits, into the ABPM that indicate when an audio alarm
will sound (step 1). Patients typically wear the ABPM for an
extended period of time, during which they are typically exposed to
stressful situations that may cause their blood pressure to rise
(step 2). As blood pressure levels elevate into dangerously high
levels, the ABPM emits an audio response and/or a visual alert that
indicates high blood pressure levels (step 3). The patient responds
to the alert (step 4) by, e.g., using breathing and other
relaxation techniques to lower their blood pressure (step 5), or by
activating a `snooze` feature on the monitor to delay the alert
(step 6). Over time the patient develops a conditioned response to
the alert and becomes aware that their blood-pressure levels are
dangerously high. Ultimately this lowers the patient's blood
pressure, thereby reducing the chance that a serious medical
condition, e.g. heart attack or stroke, occurs.
[0022] As shown in FIGS. 2A and 2B, the ABPM 20 typically features
an optical head-mounted component 105 that attaches to a patient's
head 70, and a processing component 19 that preferably attaches to
the patient's belt. In a preferred embodiment, a cable 118 provides
an electrical connection 81 between the head-mounted component 105
and the processing component 19. During operation, the head-mounted
component 105 measures optical and electrical `waveforms`,
described in more detail below, that the processing component 19
processes to determine real-time beat-to-beat diastolic and
systolic blood pressure, heart rate, and pulse oximetry. The
processing component also includes an internal wireless system that
relays this information to an Internet-based system through an
antenna 86.
[0023] Methods for processing the optical and electrical waveform
to determine blood pressure are described in the following
co-pending patent applications, the entire contents of which are
incorporated by reference: 1) CUFFLESS BLOOD-PRESSURE MONITOR AND
ACCOMPANYING WIRELESS, INTERNET-BASED SYSTEM (U.S. Ser. No.
10/709,015; filed Apr. 7, 2004); 2) CUFFLESS SYSTEM FOR MEASURING
BLOOD PRESSURE (U.S. Ser. No. 10/709,014; filed Apr. 7, 2004); 3)
CUFFLESS BLOOD PRESSURE MONITOR AND ACCOMPANYING WEB SERVICES
INTERFACE (U.S. Ser. No. 10/810,237; filed Mar. 26, 2004); 4)
VITAL-SIGN MONITOR FOR ATHLETIC APPLICATIONS (U.S. Ser. No.; filed
Sep. 13, 2004); 5) CUFFLESS BLOOD PRESSURE MONITOR AND ACCOMPANYING
WIRELESS MOBILE DEVICE (U.S. Ser. No. 10/967,511; filed Oct. 18,
2004); 6) BLOOD PRESSURE MONITORING DEVICE FEATURING A
CALIBRATION-BASED ANALYSIS (U.S. Ser. No. 10/967,610; filed Oct.
18, 2004); 7) PERSONAL COMPUTER-BASED VITAL SIGN MONITOR (U.S. Ser.
No. 10/906,342; filed Feb. 15, 2005); and 8) PATCH SENSOR FOR
MEASURING BLOOD PRESSURE WITHOUT A CUFF (U.S. Ser. No. 10/906,315;
filed Feb. 14, 2005).
[0024] FIG. 2B shows an alternate embodiment of the invention
wherein an optical patch sensor 106 sends vital-sign information to
a processing component 18 using a short-range wireless link 24. In
this embodiment the optical patch sensor 106 includes a short-range
wireless transmitter 84, and the processing component 18 features
an embedded, matched short-range wireless transceiver 89. The
optical patch sensor 106 attaches free from wires to the patient's
forehead 70 to increase mobility and flexibility. The short-range
wireless transceiver 89 is preferably a transmitter operating on a
wireless protocol, e.g. Bluetooth.TM., 802.15.4 or 802.11. A
preferred processing component 18 is a personal digital assistant
(PDA) or cellular phone that operates with the above-described ABPM
with little or no modifications. For example, the processing
component 18 can be a PDA that includes a wireless CDMA chipset,
such as the MSM family of mobile processors manufactured by
Qualcomm, each of which includes an internal Bluetooth.TM. radio.
Suitable chipset within this family include the MSM6025, MSM6050,
and the MSM6500, and are described and compared in detail in
http://www.qualcomm.com. In addition to circuit-switched voice
calls, the wireless transmitters used in these chipsets transmit
data in the form of packets at speeds up to 307 kbps in mobile
environments.
[0025] The processing component 18 preferably supports a custom
firmware application that displays and analyzes information for the
ABPM 20. The firmware application is typically written to operate
on a variety of mobile device operating systems including BREW,
Palm OS, Java, Pocket PC, Windows CE, and Symbian. A more detailed
explanation of the custom firmware application is disclosed in
co-pending U.S. patent application Ser. No. 10/967511, filed on
Oct. 18, 2004, for a CUFFLESS BLOOD-PRESSURE MONITOR AND
ACCOMPANYING WIRELESS MOBILE DEVICE, the contents of which have
been previously incorporated by reference.
[0026] FIG. 3 shows a system 120 wherein a physician calibrates the
above-described ABPM 20 for a particular patient 70 and
additionally enters blood pressure limits used in the conditioned
response alert system. In a preferred embodiment, the physician
initiates the calibration process using a personal computer 15 that
sends a signal through a wired connection 34 to a processing
component 19 within the ABPM 20. In response, the processing
component 19 measures and processes optical and electrical
waveforms collected by the optical patch sensor 105 to determine
the patient's calibration parameters. These calibration parameters
are described in more detail in BLOOD PRESSURE MONITORING DEVICE
FEATURING A CALIBRATION-BASED ANALYSIS (U.S. Ser. No. 10/967,610;
filed Oct. 18, 2004) and PATCH SENSOR FOR MEASURING BLOOD PRESSURE
WITHOUT A CUFF (U.S. Ser. No. 10/906,315; filed Feb. 14, 2005), the
contents of which have been previously incorporated herein by
reference. The system 120 correlates the calibration parameters to
blood pressure by subsequently measuring the patient's blood
pressure using a calibration device 100, typically a conventional
blood-pressure cuff, which temporarily attaches to an upper portion
112 of the patient's arm. Immediately after measuring the
calibration parameters, the personal computer 15 sends a second
signal through a second wired connection 95 to a controller 110
embedded within the calibration device 100. The signal directs the
controller 110 to initiate the cuff-based blood pressure
measurement using a motor-controlled pump 102. Once the signal is
received, the calibration device 100 collects blood pressure values
(e.g. systolic and diastolic pressures), and sends these back
through the wired connection 95 to the personal computer 15. The
system 120 repeats this process at a later time (e.g., 15 minutes
later) to collect a second set of calibration parameters. The
physician then removes the calibration device 100. The personal
computer 15 then calculates a calibration table associating the
calibration parameters and blood pressure values that passes
through the wired connection 34 to the processing component 19
within the ABPM, where it is stored in memory. The ABPM uses the
calibration table for all future cuffless measurements of blood
pressure.
[0027] Once the ABPM 20 is calibrated, the physician enters blood
pressure limits into the personal computer 15. The blood pressure
limits pass through the wired connection 34 to the processing
component 19, where they are stored in memory. During an actual
measurement, the processing module 19 compares the patient's blood
pressure measured with the ABPM 20 to the blood pressure limits
stored in memory to determine if the patient's blood pressure is
trending high or low. If this is the case, the controller 19
initiates an audio and/or visual alert as described above.
[0028] FIG. 4 shows a preferred embodiment of an Internet-based
system 53 that operates in concert with the ABPM 20 to send
information from a patient through a wireless network 54 to a web
site 66 hosted on an Internet-based host computer system 57. A
secondary computer system 69 accesses the website 66 through the
Internet 67. The system 53 functions in a bi-directional manner,
i.e. the ABPM 20 can both send and receive data. Most data flows
from the ABPM 20; using the same network, however, the monitor 20
can also receive data (e.g., calibration parameters, pre-determined
blood pressure levels, software upgrades, and text messages
indicating `alerts` or trending blood pressure) through the
wireless network 54. A wireless gateway 55 connects to the wireless
network 54 and receives data from one or more ABPMs. The wireless
gateway 55 additionally connects to a host computer system 57 that
includes a database 63 and a data-processing component 68 for,
respectively, storing and analyzing the data. The host computer
system 57, for example, may include multiple computers, software
pieces, and other signal-processing and switching equipment, such
as routers and digital signal processors. The wireless gateway 55
preferably connects to the wireless network 54 using a TCP/IP-based
connection, or with a dedicated, digital leased line (e.g., a
frame-relay circuit or a digital line running an X.25 or other
protocols). The host computer system 57 also hosts the web site 66
using conventional computer hardware (e.g. computer servers for
both a database and the web site) and software (e.g., web server
and database software).
[0029] During typical operation, the patient continuously wears the
ABPM 20 for a period of time, ranging from a 1-2 days to weeks. For
longer-term monitoring (e.g. several months), the patient may wear
the ABPM 20 for shorter periods of time during the day. To view
information sent from the ABPM 20, the patient or medical
professional accesses a user interface hosted on the web site 66
through the Internet 67 from the secondary computer system 69. The
system 53 may also include a call center, typically staffed with
medical professionals such as doctors, nurses, or nurse
practioners, whom access a care-provider interface hosted on the
same website 66.
[0030] In an alternate embodiment, the host computer system 57
includes a web services interface 70 that sends information using
an XML-based web services link to a secondary, web-based computer
application 71. This application 71, for example, could be a
data-management system operating at a hospital.
[0031] FIGS. 5A and 5B show an adhesive patch sensor 205 according
to the invention that features a pair of LEDs 210, 212 and
photodetector 214 that, when attached to a patient, generate an
optical waveform (231 in FIG. 6). A horseshoe-shaped metal
electrode 217 surrounds these optical components and generates an
electrical waveform (232 in FIG. 6). The electrical and optical
waveforms, once generated, pass through a cable 218 to a processing
module, which analyzes them as described in detail below to measure
a patient's systolic and diastolic blood pressure, heart rate, and
pulse oximetry. The patch sensor 205 features an adhesive component
219 that adheres to the patient's skin and secures the LEDs 210,
212, photodetector 214, and electrode 217 in place to minimize the
effects of motion.
[0032] During operation, the cable 218 snaps into a plastic header
216 disposed on a top portion of the patch sensor 205. Both the
cable 218 and header 216 include matched electrical leads that
supply power and ground to the LEDs 210, 212, photodetector 214,
and electrode 219. The cable 218 and header 216 additionally supply
a high-frequency electrical signal to the electrode that helps
generate the electrical waveform. When the patch sensor 205 is not
measuring optical and electrical waveforms (e.g., when the patient
is sleeping), the cable 218 unsnaps from the header 216, while the
sensor 205 remains adhered to the patient's skin. In this way a
single sensor can be used for several days. After use, the patient
removes and then discards the sensor 205.
[0033] To measure blood pressure, heart rate, and pulse oximetry,
the LEDs 210, 212 generate, respectively, red and infrared
radiation that irradiates an underlying artery. Blood volume
increases and then decreases as the heart pumps blood through the
patient's artery. Blood cells within the blood absorb and transmit
varying amounts of the red and infrared radiation depending the on
the blood volume and how much oxygen binds to the cells'
hemoglobin. The photodetector 214 detects a portion of the
radiation that reflects off an underlying artery, and in response
sends a radiation-induced photocurrent to an analog-to-digital
converter embedded within the processing component. The
analog-to-digital converter digitizes the photocurrent to generate
a time-dependent optical waveform for each wavelength. In addition,
the microprocessor analyzes waveforms generated at both red and
infrared wavelengths, and compares a ratio of the relative
absorption to a calibration table coded in its firmware to
determine pulse oximetry. The microprocessor additionally analyzes
the time-dependent properties of one of the optical waveforms to
determine the patient's heart rate.
[0034] Concurrent with measurement of the optical waveform, the
electrode 219 detects an electrical impulse from the patient's skin
that the processing component processes to generate an electrical
waveform. The electrical impulse is generated each time the
patient's heart beats.
[0035] The patch sensor 205 preferably has a diameter, `D`, ranging
from 0.5 centimeter (`cm`) to 10 cm, more preferably from 1.5 cm to
3.0 cm, and most preferably 2.5 cm. The patch sensor 205 preferably
has a thickness, `T`, ranging from 1.0 millimeter ("mm") to 3 mm,
more preferably from 1.0 mm to 1.5 mm, and most preferably 1.25 mm.
The patch sensor 205 preferably includes a body composed of a
polymeric material such as a neoprene rubber. The body is
preferably colored to match a patient's skin color, and is
preferably opaque to reduce the affects of ambient light. The body
is preferably circular in shape, but can also be non-circular, e.g.
an oval, square, rectangular, triangular or other shape.
[0036] FIG. 6 shows both optical 231 and electrical 232 waveforms
generated by the patch sensor of FIGS. 5A and 5B and used in the
calibration procedure described above. Following a heartbeat, the
electrical impulse travels essentially instantaneously from the
patient's heart to the patch sensor, where the electrode detects it
to generate the electrical waveform 232. At a later time, a
pressure wave induced by the same heartbeat propagates through the
patient's arteries and arrives at the sensor, where the LEDs and
photodetector detect it as described above to generate the optical
waveform 231. The propagation time of the electrical impulse is
independent of blood pressure, whereas the propagation time of the
pressure wave depends strongly on pressure, as well as mechanical
properties of the patient's arteries (e.g., arterial size,
stiffness). The microprocessor runs an algorithm that analyzes the
time difference .DELTA.T between the arrivals of these signals,
i.e. the relative occurrence of the optical 231 and electrical 232
waveforms as measured by the patch sensor.
[0037] In still other embodiments, the above-described system can
receive inputs from other measurement devices, such as weight
scales, glucometers, EKG/ECG monitors, cuff-based blood pressure
monitors, dietary monitors, pedometers and other exercise monitors,
and GPS systems.
[0038] Still other embodiments are within the scope of the
following claims.
* * * * *
References