U.S. patent application number 10/418065 was filed with the patent office on 2003-11-27 for headset for measuring physiological parameters.
This patent application is currently assigned to Southwest Research Institute. Invention is credited to Bartels, Keith A., Canady, Larry D. JR., Honeyager, Kevin S..
Application Number | 20030220584 10/418065 |
Document ID | / |
Family ID | 29251052 |
Filed Date | 2003-11-27 |
United States Patent
Application |
20030220584 |
Kind Code |
A1 |
Honeyager, Kevin S. ; et
al. |
November 27, 2003 |
Headset for measuring physiological parameters
Abstract
Methods and systems for determining physiological parameters
from body sounds obtained from a person's ear. In various exemplary
embodiment, the system includes an earplug housing; a sensing
element disposed within a portion of the earplug housing; an
acoustic shield coupled to the earplug housing, the acoustic shield
reducing or eliminating extracorporeal sounds; and a
preamplification circuit electrically coupled to the sensing
element. In various exemplary embodiments, the system is operable
to determine motion and/or vibration of the external acoustic
meatus or the tympanic membrane of the ear due to internally
generated body sounds.
Inventors: |
Honeyager, Kevin S.; (San
Antonio, TX) ; Bartels, Keith A.; (San Antonio,
TX) ; Canady, Larry D. JR.; (Bergheim, TX) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
Southwest Research
Institute
San Antonio
TX
|
Family ID: |
29251052 |
Appl. No.: |
10/418065 |
Filed: |
April 18, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60373616 |
Apr 19, 2002 |
|
|
|
Current U.S.
Class: |
600/559 |
Current CPC
Class: |
A61B 5/0285 20130101;
A61B 5/024 20130101; A61B 5/0816 20130101; A61B 7/04 20130101; A61B
5/02125 20130101; A61B 7/023 20130101; A61B 5/02 20130101; A61B
5/7221 20130101; A61B 5/6817 20130101 |
Class at
Publication: |
600/559 |
International
Class: |
A61B 005/00 |
Claims
What is claimed is:
1. A system for determining the motion and/or vibration of the
external acoustic meatus of the ear, the system comprising: an
earplug housing; a sensing element disposed within a portion of the
earplug housing; an acoustic shield coupled to the earplug housing,
the acoustic shield reducing or eliminating extracorporeal sounds;
and a preamplification circuit electrically coupled to the sensing
element.
2. The system according to claim 1 further comprising a data
acquisition and/or processing system electrically coupled to the
preamplification circuit.
3. The system according to claim 2, wherein the system is operable
to determine motion and/or vibration of the external acoustic
meatus of the ear due to internally generated body sounds.
4. The system according to claim 3, wherein the data acquisition
and/or processing system uses the determined motion and/or
vibration to determine one or more of the person's heart rate,
respiration rate, heart sounds, blood pressure or blood pressure
trends, PWV or PWVI, and indicators of heart murmurs.
5. The system according to claim 1 further comprising a power
supply system electrically coupled to the data acquisition and/or
processing system.
6. The system according to claim 1, wherein the acoustic shield is
disposed between the earplug housing and external environment.
7. The system according to claim 1, wherein the earplug housing is
made of compressible foam, a biocompatible rigid or semirigid
polymer, or the like.
8. The system according to claim 1, wherein the sensing element is
a strain gage, a PVDF film, an accelerometer, a piezoceramic
substrate, or the like.
9. The system according to claim 1, wherein the earplug housing,
the sensing element, the preamplification circuit and the acoustic
shield are located within the ear.
10. A headset device for positioning and/or retaining at least one
of the system according to claim 1 in the external acoustic meatus
of at least one ear.
11. The headset device according to claim 10, wherein the
preamplification circuitry is disposed within the headset.
12. The headset device according to claim 10, wherein the data
acquisition and/or signal processing system is either integral to
the headset or external to the headset.
13. The headset according to claim 12, wherein the data acquisition
and/or signal processing system is used to determine one or more of
the person's heart rate, respiration rate, S1 timing, S2 timing,
blood pressure or blood pressure trends, PWV or PWVI, and
indicators of heart murmurs.
14. A system for determining the motion or vibration of the
tympanic membrane of the ear, the system comprising: an earplug
housing; a sensing element disposed within a portion of the earplug
housing; an acoustic shield coupled to the earplug housing, the
acoustic shield reducing or eliminating extracorporeal sounds; a
preamplification circuit electrically coupled to the sensing
element.
15. The system according to claim 14 further comprising a data
acquisition and/or processing system electrically coupled to the
preamplification circuit.
16. The system according to claim 15, wherein the system is
operable to determine motion or vibration of the external acoustic
meatus of the ear due to internally generated body sounds.
17. The system according to claim 16, wherein the data acquisition
and/or processing system uses the determined motion and/or
vibration to determine one or more of the person's heart rate,
respiration rate, S1 timing, S2 timing, blood pressure or blood
pressure trends, PWV or PWVI, and indicators of heart murmurs.
18. The system according to claim 14 further comprising a power
supply system electrically coupled to the data acquisition and/or
processing system.
19. The system according to claim 14, wherein the acoustic shield
is disposed between the earplug housing and external
environment.
20. The system according to claim 14, wherein the earplug housing
is made of compressible foam, a biocompatible rigid or semirigid
polymer, or the like.
21. The system according to claim 14, wherein the sensing element
is a strain gage, a PVDF film, an accelerometer, a piezoceramic
substrate, or the like.
22. The system according to claim 14, wherein the earplug housing,
the sensing element, the preamplification circuit and the acoustic
shield are located within the ear.
23. A headset device for positioning and retaining at least one of
the system according to claim 14 in the tympanic membrane of at
least one ear.
24. The headset device according to claim 23, wherein the
preamplification circuitry is disposed within the headset.
25. The headset device according to claim 23, wherein the data
acquisition and signal processing system is either integral to the
headset device or external to the headset device.
26. The headset device according to claim 25, wherein the data
acquisition and/or signal processing system is used to determine
one or more of the person's heart rate, respiration rate, S1
timing, S2 timing, blood pressure or blood pressure trends, PWV or
PWVI, and indicators of heart murmurs.
27. The headset device of claim 10 having a system according to
claim 1 in each ear, wherein signals associated with motion and/or
vibration of the external acoustic meatus from each ear can be used
to assess signal quality, perform motion artifact rejection, and
the like.
28. The headset device of claim 23 having a system according to
claim 14 in each ear, wherein signals associated with motion and/or
vibration of the external acoustic meatus from each ear can be used
to assess signal quality, perform motion artifact rejection, and
the like.
29. A method for determining cardiovascular parameters of a person,
the method comprising: placing a sensing device within a person's
ear; placing a blood-pressure waveform sensor at a location distal
to the heart; obtaining a first set of waveforms from the sensing
device; obtaining a second set of waveforms from the blood-pressure
waveform sensor; performing a signal processing or conditioning
operation using the first and second sets of waveforms; determining
a time delay between the dicrotic notch component of the
conditioned blood-pressure waveform signal and the S2 component of
the conditioned ear sensor signal; determining a blood pressure
pulse transit time value by adding S2D, representing a time delay
between a person's heart valve closure time and an arrival time of
the S2 signal at the first distal location, to the time delay
between the dicrotic notch signal and the S2 signal; and
determining cardiovascular parameters of a person using the
determined blood pressure pulse transit time and at least one
physical parameter representative of a arterial distance between a
location of aortic valve of the heart and a location of the
blood-pressure waveform sensor.
30. The method according to claim 29, wherein the sensing device is
a motion or vibration sensing device.
31. The method according to claim 29, wherein cardiovascular
parameters include blood pressure-wave velocity, heart rate, a
person's heart isovolumetric contraction period or the like.
32. The method according to claim 29, wherein performing a signal
processing or conditioning operation comprises one or more of
performing an ensemble averaging operation, performing a processing
using a bandpass filter, and performing a processing to determine a
stable detection point on the S2 signal from the ear.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention relates to systems and methods for detecting
and/or measuring a person's physiological parameters by detecting
the person's internally generated body sounds, such as heart
sounds, at a location within a person's ear, and processing the
measured body sounds to obtain physiological parameters of
interest.
[0003] 2. Description of Related Art
[0004] Sound signals recorded from the heart are called
phonocardiogram (PCG) signals. A healthy heart generates two
distinct sounds that are coincident with the closure of the heart
valves. These two sounds are called the first heart sound (S1) and
the second heart sound (S2). In particular, S2 is coincident with
the closure of the aortic valve. The closure of the aortic valve
also creates a distinct feature on the arterial blood pressure
waveform called the dicrotic notch. The pulse transit time (PTT) is
defined as the time required for an arterial blood pressure pulse
to travel from the heart to a distal location to the heart. The PTT
can be measured by determining the delay between the closure of the
aortic valve and the arrival of the dicrotic notch at a distal
measurement point. This measurement is possible since, by placing a
phonocardiogram (PCG) sensor on the chest near the aortic valve, it
can be assumed that the delay between the closure of the valve and
the measurement of the S2 sound on the chest is negligible. The
arterial blood pressure pulse wave velocity (PWV) is computed by
dividing the arterial path length between the heart and the
measurement point by the PTT. Because the PWV is dependent on the
stiffness of the arterial walls, it can be a useful parameter in
determining the health of the cardiovascular system (e.g.
arteriosclerosis).
[0005] Conventional methods and devices measure PWV using a PCG
sensor in a standard location on the chest and a blood pressure
waveform measurement at a location distal to the heart. When
PTT/PWV is to be measured using a PCG sensor at a location distal
to the heart, the true PTT/PWV cannot be calculated unless one
accounts for the propagation delay, hereinafter referred to as S2D,
where S2D is the measured delay between the aortic valve closure
and the arrival of the second heart sound (S2) at the distal
location. The accuracy of the PTT/PWV measurement is directly
proportional to the accuracy with which S2D is known.
[0006] In addition to PWV, heart sound information can be used to
determine heart rate from the timing of successive S1 or S2
components. Respiration rate can be determined from monitoring the
splitting of S2 into its component aortic and pulmonary valve
closure due to breathing. It is well known that inspiration causes
an increase in the time delay between the aortic and pulmonary
valve closure events. Respiration rate can also be determined from
breath sounds obtained from a phonocardiogram sensor.
SUMMARY OF THE INVENTION
[0007] This invention provides systems and methods for detecting a
person's internally generated body sounds at a location within a
person's external acoustic meatus, or ear canal.
[0008] This invention separately provides systems and methods for
determining a person's physiological conditions and/or parameters
based on internally generated body sounds detected within a
person's ear canal.
[0009] This invention separately provides systems and methods for
determining a person's heart sounds, based on internally generated
body sounds detected within a person's ear canal.
[0010] This invention separately provides systems and methods for
measuring and/or detecting one or more of a person's heart rate,
respiration rate, pulse wave velocity (PWV), blood pressure or
blood pressure trend, and other cardiac-related parameters, based
in whole or in part on internally generated body sounds detected
within a person's ear canal.
[0011] In various exemplary embodiments of the systems and methods
according to this invention, heart sounds are obtained by placing a
transducer within an ear of a person to detect internally generated
body sounds, producing a signal representative of the vibration
and/or motion occurring within the ear, and processing said signal
to extract heart sound and other physiological information.
[0012] In various exemplary embodiments of the systems and methods
according to this invention, signals are obtained by determining
the vibrations and/or motion of the tympanic membrane caused by
internally generated body sounds.
[0013] In various exemplary embodiments of the systems and methods
according to this invention, signals are obtained by determining
the vibrations and/or motion of the cartilaginous and bony portion
of the ear's external acoustic meatus caused by internally
generated body sounds.
[0014] In various exemplary embodiments of the systems and methods
according to this invention, the ear sensor device includes an ear
plug housing, a vibration or motion sensor disposed through at
least a portion of the ear plug housing, and one or more electrical
signal connectors that connect the sensor to a data acquisition and
processing system.
[0015] In various exemplary embodiments of the systems and methods
according to this invention, an enhanced distal phonocardiogram
(PCG) recording is performed using a signal conditioning or
processing operation of the ear sensor signals triggered by the
dicrotic notch of a separately obtained blood-pressure
waveform.
[0016] In various exemplary embodiments of the systems and methods
according to this invention, the S2 obtained from a sensor other
than the ear sensor is used as a trigger signal.
[0017] In various exemplary embodiments of the systems and methods
according to this invention, an enhanced distal PCG recording using
a signal conditioning or processing operation is performed using an
ensemble averaging operation of the ear sensor waveform triggered
by the dicrotic notch of the separately obtained blood-pressure
waveform.
[0018] In various exemplary embodiments of the systems and methods
according to this invention, DT, the delay time between a dicrotic
notch signal and an S2 signal, is determined by using a recording
of the blood pressure waveform and a recording of the ear sensor
signal, both acquired from a location distal to the heart.
[0019] In various exemplary embodiments of the systems and methods
according to this invention, a corrected PTT is determined by
adding S2D to DT.
[0020] In various exemplary embodiments of the systems and methods
according to this invention, PWV is determined using the corrected
PTT and artery length.
[0021] In various exemplary embodiments of the systems and methods
according to this invention, an index of PWV (PWVI) is determined
using DT.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Various exemplary embodiments of this invention will be
described in detail, with reference to the following figures,
wherein:
[0023] FIGS. 1A and 1B represent a schematic illustration of one
exemplary embodiment of a system used to detect internally
generated body sounds, such as for example, the first and second
heart sounds (S1 and S2);
[0024] FIG. 2 is a drawing of one exemplary embodiment of the
system used to detect internally generated body sounds, positioned
in its measuring location;
[0025] FIG. 3 is a graph plotting data acquired simultaneously from
the ear sensor device illustrated in FIG. 1 and a reference chest
microphone commonly used for obtaining phonocardiograms;
[0026] FIG. 4 is a drawing of the referenced external and internal
structures of the ear;
[0027] FIG. 5 is a schematic illustration of one exemplary
embodiment of a system used to detect internally generated body
sounds, such as for example, the first and second heart sounds S1
and S2, wherein the vibration and/or motion of the tympanic
membrane is detected;
[0028] FIG. 6 is a schematic illustration of another exemplary
embodiment of a system used to detect internally generated body
sounds, such as for example, the first and second heart sounds S1
and S2, wherein the vibration and/or motion of the external
acoustic meatus is detected;
[0029] FIG. 7 is a flowchart outlining an exemplary embodiment of a
method for obtaining internally generated body sounds from a
person, such as the first and second heart sounds (S1 and S2);
[0030] FIG. 8 is a flowchart outlining one exemplary embodiment of
a method for determining S2D, the delay between the aortic valve
closure and the arrival of a second heart sound (S2) within an ear
of a person;
[0031] FIG. 9 is a flowchart outlining one exemplary embodiment of
a method for determining and/or measuring physiological parameters
of a person, including cardiovascular parameters, such as, for
example, PTT, PWV and PEP, using a determined S2D value; and
[0032] FIG. 10 is a flowchart outlining another exemplary
embodiment of a method for determining and/or measuring
physiological parameters of a person, including cardiovascular
parameters, such as, for example, PWVI, without using a determined
S2D value.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0033] As described herein, this invention provides systems and
methods for acquiring body sound information from a person's ear,
which can then be converted to useful physiological parameters of
interest, such as heart rate, heart valve closure timing, pulse
wave velocity, blood pressure, and the like.
[0034] FIGS. 1A and 1B show one exemplary embodiment of a system
100 according to this invention in which internally generated body
sounds are detected or measured using an ear sensor device 110
inserted into the ear of a person. As shown in FIGS. 1A-1B, the ear
sensor or ear sensing device 110 includes an ear plug housing 124,
a sensor element 114 disposed within a portion of the ear plug
housing 124, an acoustic shield 112 and a preamplification circuit
116 electrically coupled to sensor element 114 via electrical
connections 118. The purpose of the acoustic shield 112 is to
shield the sensor element 114 from ambient noise generated outside
the person's body. The preamplification circuit 116 is used to
convert the motion or vibration signal acquired by the sensor
element 114 into an output, such as a voltage and/or a current, to
be read by a data acquisition and processing system 130.
[0035] FIG. 2 shows one exemplary embodiment of a system 100 when
properly worn in the ear.
[0036] In one exemplary embodiment, the ear plug housing 124 is
made of a foam like material, such as compressible foam.
Alternatively, the ear plug housing 124 is made of a biocompatible
rigid or semi-rigid polymer.
[0037] As shown in FIG. 1A, in one exemplary embodiment, the ear
sensor device 110 is integrated into a headset 120, which can be
positioned on a person's head. The headset 120 may be any style of
headset device known in the art. Generally, the headset device is
electrically coupled to a data acquisition and processing system
130. The data acquisition and processing system may include any
data acquisition and processing system known in the art.
[0038] In an exemplary embodiment, motion of vibrations detected by
the sensing element 114 are converted to electrical signals by the
preamplification circuit 116, and are then transmitted to the data
acquisition and processing system via the power and signal cable
122.
[0039] The data acquisition and processing system 130 may be
located external to the headset 120, or may be located within the
headset 120 for purposes of converting the analog signals to the
digital domain and performing such signal processing as necessary
to obtain the desired physiological parameters.
[0040] It will be appreciated by those skilled in the art that the
system 100 shown in FIG. 1A represents one exemplary embodiment of
the types of devices that may be used with this invention.
[0041] The headset 120 is used for placement of the sensing device
within the ear. The headset may contain a single sensor for one
ear, or sensors for both ears. The design is such that sufficient
tension is provided against the ear to securely retain the sensor
element 114 and acoustic shield 112 within the ear's external
acoustic meatus 200 (shown in FIG. 4). A secondary function of the
headset 120 may be to acoustically isolate external ambient sounds
from the ear sensor device 110. For this purpose the headset 120
may be constructed in such a fashion as to fully enclose the ear's
auricula 206 (shown in FIG. 4) using a padded material surrounding
the auricula 206 to minimize external ambient noise.
[0042] In an alternative exemplary embodiment of the system, the
ear sensor device 110 could be manually placed in the ear, and a
protective headset could be positioned over the sensor(s), with a
cable connecting the sensors to the headset.
[0043] In an exemplary embodiment, the preamplification circuit 116
is located in the ear plug housing 124 with the sensor element 114
and the ear sensor device 110 is then used without headset 120. In
this embodiment the ear sensor device 110 is designed as a
standalone system wherein the signal output from preamplification
circuit 116 is delivered through a cable to an external device with
a power supply and data acquisition and processing capability. The
sensor is held in place by the friction of the ear plug housing 124
and acoustic shield 112 against the external acoustic meatus 200
(shown in FIG. 4).
[0044] In another exemplary embodiment, the preamplification
circuit 116 is located in the headset 120.
[0045] FIG. 5 shows a sensor element 114 that consists of a
vibration or motion sensor able to detect the modulations of the
tympanic membrane 202 (shown in FIG. 4). If the ear canal is
acoustically sealed between the sensing element and the outer ear,
the effect of extracorporeal sounds on tympanic membrane motion
will be reduced or eliminated. The resulting motion of the tympanic
membrane will therefore be due to sounds generated from within the
body.
[0046] An alternative embodiment of ear sensor device 110 is shown
in FIG. 6. This embodiment shows a sensor element 150 used to
detect motion and vibrations of the external acoustic meatus 200 of
the ear (shown in FIG. 4). Internally generated body sounds are
transmitted through various body tissues, including the bony and
cartilaginous structures of the body. These structures include the
bony and cartilaginous parts of the ear's external acoustic meatus
(210 and 212 in FIG. 4). Sensor element 150 is designed to maximize
the signal obtained from the motion and vibration of the external
acoustic meatus 200.
[0047] FIG. 6 shows one possible exemplary embodiment of a sensor
used to measure the vibrations of the external acoustic meatus. A
strain gage or polyvinylidene fluoride (PVDF) sensor element 150 or
the like is attached to a substrate 151, which is shaped to fit
within a substantial portion of the earplug housing 124. The sensor
element, substrate and associated wire connections are encapsulated
in a semi-rigid biocompatible compressible material such as a
polyurethane elastomer. Vibrations emanating from the external
acoustic meatus 200 will cause the substrate 151 and attached
sensor element 150 to flex, thereby producing a signal. The
encapsulated sensor is attached to the headset 120 so that the wire
connections are internal to the headset 120 and can be connected to
a preamplification circuit 116.
[0048] In another exemplary embodiment of the invention, an ear
sensor device 110 is used in each ear to obtain two channels of the
previously described motion or vibration signals. The signals from
each ear can be used together for purposes of assessing signal
quality and performing motion artifact rejection. For instance,
heart sounds that generate vibrations of the external acoustic
meatus 200 will be delivered in the same general timeframe at each
ear. Detection of a distinct feature such as the first or second
heart sound (S1 or S2) could be required by a signal processing
algorithm to occur nearly simultaneously in both ears. If a signal
is detected in one ear but not the other, the signal could then be
rejected as a motion artifact unrelated to heart sounds. The same
principle can be applied to any feature of interest in the signal
that is expected to be common to both channels.
[0049] Likewise, the ear sensor device 110 in one ear may be
positioned improperly so that the signal of interest is
undetectable or of poor quality. The ear sensor device 110 in the
opposite ear can be used to provide the physiological parameters of
interest providing that it has sufficient signal quality.
[0050] FIG. 3 shows a plot of heart sound data, for example S1 and
S2 signal data, acquired simultaneously from an ear sensor device
110 and a reference chest microphone commonly used for obtaining
phonocardiograms. As shown in FIG. 1, the ear sensor device 110 is
clearly able to detect the first and second heart sounds, S1 and
S2. The waveform shapes of the S1 and S2 heart sounds are not
identical because of the difference in construction between the ear
sensor device 110 and the chest sensor, and the additional travel
time required by sound to travel up to the ear. However, it will be
appreciated that the desired information is present and able to be
acquired at the ear using the methods and systems according to this
invention.
[0051] The chest PCG data shown in FIG. 3 were acquired using a
commercially available PCG sensor that uses condenser microphone
technology. Similar results are obtained using other technologies
such as piezoelectric materials and accelerometers. The waveform
data shown were enhanced by a digital bandpass filter that passed
frequencies between 25 and 55 Hz.
[0052] This invention further provides systems and methods that
improve the signal-to-noise ratio (SNR) of the acquired or measured
heart sounds by improving signal processing. In various exemplary
embodiments, improving signal conditioning or processing, and thus
improving signal-to-noise ratio (SNR) of the acquired or measured
heart sounds, is performed by averaging two or more consecutive
heart cycles, also called ensemble averaging.
[0053] To perform the ensemble averaging, the individual heart
cycles must first be identified. This can be done by detecting a
unique feature that occurs during each heart cycle. In one
exemplary embodiment, the R-wave of a separately obtained ECG
signal is used as the delimiter of heart cycles. This is called
R-wave triggering of the ensemble averaging.
[0054] In another exemplary embodiment, the S2 signal from of a
separate chest PCG sensor can be used to delimit the ear sensor
waveform for ensemble averaging. Using the S2 trigger is
advantageous over the R-wave trigger in that a higher
signal-to-noise ratio (SNR) for the averaged ear sensor S2 signal
is obtained. This is because there is a beat-to-beat variability of
the time between the R-wave and the S2 signal. This variability can
cause a "jitter" of the S2 signal when using the R-wave trigger and
hence some signal amplitude can be averaged away.
[0055] The R-wave trigger is advantageous in that it is easily
performed. The R-wave of an ECG is a very easily identifiable
signal.
[0056] The advantage of the S2-triggered ensemble averaging could
also be obtained by using the dicrotic notch of a separately
obtained blood pressure waveform as the trigger. The dicrotic notch
and S2 signal both result from the closure of the aortic valve and
hence have the same timing.
[0057] It will be noted that in various exemplary embodiments of
the systems and methods according to this invention, ensemble
averaging is not required to be performed to detect the S2 signal
at a person's ear. One such example is if the signal-to-noise ratio
(SNR) of the ear's S2 signal is high due to relatively low noise
from sources (other than the heart valves) within the body and from
the external environment. That is, ensemble averaging may not be
required if external ambient noise and/or body vibration is low or
negligible and the signal components of interest can be detected on
a beat-to-beat basis.
[0058] As described above, the PTT is measured with current
technology as the time between the S2 signal measured on the chest
and the dicrotic notch of an arterial blood pressure waveform. In
various exemplary embodiments of the systems and methods according
to this invention, the PTT is measured as the time between the
distally measured S2 signal, i.e., ear measured S2 signal, and the
dicrotic notch plus S2D, where S2D is the measured delay between
the aortic valve closure as measured at the chest and the arrival
of the S2 signal at the ear location.
[0059] In one exemplary embodiment, the S2D value could be
determined as an average value for the entire population. In
another exemplary embodiment, a predetermined S2D value for the
particular individual may be used. In yet another exemplary
embodiment, the S2D value could be experimentally determined based
on a person's demographics, such as height, weight, or age.
[0060] The predetermined S2D value could be obtained for an
individual by using a first PCG sensor, for example a chest PCG
sensor, during a calibration step. The S2D would be measured as the
time delay between the S2 measured by the ear sensor device and the
S2 measured by the chest PCG. An individually calibrated value for
S2D adds an additional initial step to using the device, but would
give a more accurate measurement than if a population-based
standardized value was used. For some applications, however, the
standardized S2D value would give sufficiently accurate
results.
[0061] In various exemplary embodiments of the systems and methods
according to this invention, a person's physiological parameters,
such as, for example PWVI, can be obtained by using the delay time
(DT) between dicrotic notch and S2 signals without using the S2D
signal. That is, an index of PWV, e.g., PWVI, can be determined
without having to determine the S2D signal. The PWVI monitored over
time would still show increases or decreases in PWV.
[0062] FIG. 7 is a flowchart outlining another exemplary embodiment
of a method for determining physiological parameters by using body
sounds obtained from the ear.
[0063] As shown in FIG. 7, the method starts at step S700 and
continues to step S710 where an ear sensor device is placed into a
person's ear canal. Next, at step 720, a first set of body sounds
is obtained using the ear sensor device.
[0064] Then, at step S730, the body sounds acquired by the ear
sensor device are converted into electrical signals using the
preamplification circuit. The operation continues to step S740,
where an S1 and S2 value are determined along with other stable
features in the waveform. Next, at step S750, various physiological
parameters of a person are determined from the ear signal values
determined in step S740 using techniques well known in the art.
These physiological parameters may include one or more of: a
person's heart rate; a person's respiration rate; a person's valve
closure timing; an indication of murmur detection; breath sounds; a
person's PWV; and a person's blood pressure or blood pressure
trend.
[0065] FIG. 8 is a flowchart outlining one exemplary embodiment of
a method for determining S2D. The various steps of the method shown
in FIG. 8 are generally performed only occasionally for each
individual.
[0066] As shown in FIG. 8, the method starts at step S800 and
continues to step S810 where a first PCG sensor is placed on a
person's chest and a second ear sensor device is placed in the
person's ear canal. Next, at step S820, data are acquired
simultaneously from both sensors, for example, a first set of heart
sound signals are obtained or acquired using the first PCG sensor
and a second set of heart sound signals are obtained or acquired
using the ear sensor device.
[0067] Then, at step S830, a signal processing or conditioning
operation is performed using the first and second sets of heart
sound signals acquired. In an exemplary embodiment of the systems
and methods according to this invention, an ensemble averaging
operation is performed using the first and second sets of signals
acquired. In another exemplary embodiment of the systems and
methods according to this invention, signal processing or
conditioning S830 may be performed using a bandpass filter. In yet
another exemplary embodiment of the systems and methods according
to this invention, signal processing is performed for determining a
stable detection point in the ear sensor device signal.
[0068] Next, at step S840, using the results obtained from the
signal processing or conditioning operation, such as for example
from an ensemble averaging operation, the S2D is determined. The
method then continues to step S850, where the method stops.
[0069] FIG. 9 is a flowchart outlining one exemplary embodiment of
a method for determining physiological parameters, including for
example, PWV, PEP and the like, by using distally measured heart
sounds. In one exemplary embodiment, the timing of the closure of
the aortic valve in combination with simultaneously obtained ECG
and blood pressure waveforms can be used to compute the heart's
pre-ejection period (PEP). PEP is also known as the isovolumetric
contraction period and is the time during which ventricular
pressure is increasing while the aortic valve is still closed. When
the pressure within the ventricle surpasses the aortic pressure the
aortic valve opens and the PEP ends. PEP, especially when used in
ratio to the ventricular ejection time, is another important
parameter indicating cardiovascular health.
[0070] As shown in FIG. 9, the method starts at step S900 and
continues to step S910 where the ear sensor device is placed into a
person's ear canal, and a blood-pressure waveform sensor is placed
at a second distal location to the heart. Next, at step 920, a
first set of waveforms is obtained from the ear sensor device. A
second set of waveforms is simultaneously obtained from the
blood-pressure waveform sensor.
[0071] Then, at step S930, a signal conditioning/processing
operation, such as for example, an ensemble averaging operation,
may optionally be performed using the first and second sets of
waveforms obtained in step S920. The operation continues to step
S940, where a time delay (DT) between the dicrotic notch of the
blood pressure signal and the S2 component of the ear signal is
determined.
[0072] At step S950, a blood pressure pulse transit time (PTT)
value is determined by adding a previously determined or known
value of S2D, representing a time delay between a person's aortic
valve closure time and an arrival time of the S2 signal at the ear,
to the time delay DT between a dicrotic notch component and the S2
component of the ear signal.
[0073] Next, at step S960, various cardiovascular parameters of a
person are determined using the determined blood pressure pulse
transit time calculated in step S950 and at least one physical
parameter representative of an arterial distance between the aortic
valve and the measurement location of the blood-pressure waveform
sensor. The method then continues to step S970 where the method
stops.
[0074] In one exemplary embodiment, the method shown in FIG. 9 is
used to determine arterial blood pressure pulse wave velocity (PWV)
by dividing the arterial path length between the heart and the
distal blood pressure measurement point by the PTT. Because the
pulse wave velocity is dependent on the stiffness of the arterial
walls, PWV can be a useful parameter in determining the health of
the cardiovascular system (e.g. arteriosclerosis).
[0075] In one exemplary embodiment of the method according to this
invention, step S930, performing a signal conditioning/processing
operation, for example, an ensemble averaging operation, includes
determining a person's individual heart cycles. In one exemplary
embodiment, determining a person's individual heart cycles includes
determining a delimiter in the person's individual heart cycles. A
delimiter of heart cycles may be obtained from a separately
obtained ECG R-wave. Alternatively, determining a delimiter of
heart cycles may be performed by determining an S2 signal,
representative of a second heart sound associated with closure of
the aortic heart valve, from the first set of heart sound vibration
signals acquired by the ear sensor device.
[0076] In various exemplary embodiments of the systems and methods
according to this invention, performing a signal
conditioning/processing operation, for example, an ensemble
averaging operation, may include using the dicrotic notch of a
separately obtained arterial blood pressure waveform as a
trigger.
[0077] Furthermore, it will be appreciated by those skilled in the
art that the blood pressure waveform sensor may include a blood
pressure cuff, an arterial tonometer, or other sensor sensitive to
the blood pressure waveform.
[0078] FIG. 10 is a flowchart outlining another exemplary
embodiment of a method for determining physiological parameters,
including for example, PWVI and the like, by using distally
measured heart sounds.
[0079] As shown in FIG. 10, the method starts at step S1000 and
continues to step S1010 where an ear sensor device is placed into a
person's ear canal, and a blood-pressure waveform sensor is placed
at a second distal location to the heart. Next, at step S1020, a
first set of waveforms is obtained from the signal acquired by the
ear sensor device. A second set of waveforms is simultaneously
obtained from the blood-pressure waveform sensor.
[0080] Then, at step S1030, a signal conditioning/processing
operation, such as for example, an ensemble averaging operation,
may optionally be performed using the first and second sets of
waveforms obtained in step S1020. The operation continues to step
S1040, where a time delay (DT) between the blood pressure signal's
dicrotic notch component and the S2 component of the ear signal is
determined.
[0081] Next, at step S1050, various parameters, including
cardiovascular parameters, of a person are determined using the
determined delay time DT calculated in step S1040. In one exemplary
embodiment, the method shown in FIG. 10 is used to determine
arterial blood pressure pulse wave velocity index (PWVI). Because
the pulse wave velocity is dependent on the stiffness of the
arterial walls, PWVI can be a useful parameter in determining the
health of the cardiovascular system (e.g. arteriosclerosis). The
method then continues to step S1060 where the method stops.
[0082] In one exemplary embodiment of the method according to this
invention, step S1030, performing a signal conditioning/processing
operation, for example, an ensemble averaging operation, includes
determining a person's individual heart cycles. In one exemplary
embodiment, determining a person's individual heart cycles includes
determining a delimiter in the person's individual heart cycles.
Determining a delimiter of heart cycles may be performed by
determining an R-wave using the first set of electrocardiogram
signals. Alternatively, determining a delimiter of heart cycles may
be performed by determining an S2 signal, representative of a
second heart sound associated with closure of the heart valves,
from the first set of ear sensor signals.
[0083] In various exemplary embodiments of the systems and methods
according to this invention, performing a signal
conditioning/processing operation, for example, an ensemble
averaging operation, may include using the dicrotic notch component
of the pressure waveform as a trigger.
[0084] While this invention has been described in conjunction with
the specific embodiments outlined above, it is evident that many
alternatives, modifications and be apparent to those skilled in the
art. Accordingly, the preferred f the invention as set forth above
are intended to be illustrative, not us changes may be made without
departing from the spirit and scope of the fined in the following
claims.
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