Description
Respiration measurement sensor
The present invention relates to a sensor for measuring
respiration of a user.
It is known in the prior art to measure respiration, and
other body parameters characterized by mechanical movement,
with devices mechanically coupled to the body. In most cases
the respiration monitoring is based on an impedance
measurement of the patient's thorax. However, other measuring
methods are also known, e.g., measuring the temperature
variations of the respiration air or pressure variations
between body and support or mechanical ventilation or the
like.
Such a system is known from U.S. Pat. No. 5,840,907, which
discloses a respiratory analysis system for monitoring a
respiratory variable of a patient. The system includes an
array of sensors attached to the body of the patient for
measuring respiratory movement at different locations of the
patient's body to generate a set of independent respiratory
movement signals. Further, these signals are processed to
derive a respective breathing pattern. Disadvantageously, the
deployment of the system causes discomfort to the patient as
the sensor harness herein induces constraints in physical
movement.
Another example is shown in U.S. Pat. No. 6,416,471, which
discloses a system and method for monitoring vital signs and
capturing data from a patient remotely. This includes a
cordless sensor band with sensors and transmission circuitry
for the detection and transmission of vital signs data.
However, the sensor band is designed to work for only limited
period of time, for example 24-30 hours, after which it need
to be discarded and replaced by a new sensor band, which in
turn incurs cost.
The object of the invention is to provide a means which can
be utilized in a flexible and cost-effective way for
measuring the respiratory function of an individual.
The above object is achieved by a sensor according to claim 1
and a system according to claim 16.
The invention is set forth and characterized in the main
claim, while the dependent claims describe preferred
embodiments of the invention.
The coupling of the capacitor to the skin of the user enables
accurate sensing of the forces and the movement caused by the
user's respiration. The sensor uses only simple circuitry to
measure the respiration of the user corresponding to the
change in the capacitance of the capacitor. The sensor
herein is compact in design and is inexpensive as for system
implementation standard components like known variable
capacitors is used. The sensor provides flexibility to the
user as it does not require any additional harness for its
functioning, which may cause discomfort to the person.
According to an embodiment herein, the first capacitor plate
and the second capacitor plate are coupled to the skin via a
base member fixed onto the skin. This facilitates
transmission of the fluctuations caused during respiration
from the skin to the capacitor plates.
According to a preferred embodiment, the base member is an
adhesive plaster. This provides for easy attachment or
removal of the sensor from the body of the user.
According to a preferred embodiment, the change in the
relative arrangement of first capacitor plate and the second
capacitor plate is a change in the distance between the first
capacitor plate and the second capacitor plate. This varies
the capacitance of the capacitor proportional to the
respiration motion.
According to another preferred embodiment, the first
capacitor plate and the second capacitor plate are connected
to a spacing means which holds the capacitor plates at a
tension, wherein the capacitor plates are coupled to the skin
such that the movement of the skin exerts a force against the
tension to change the distance between the first capacitor
plate and the second capacitor plate. This helps to provide
the sufficient flexibility to vary the distance between the
capacitor plates.
According to another preferred embodiment, further comprises
a connecting means attached to the first capacitor plate and
the second capacitor plate, wherein the connecting means is
coupled to the skin in opposite sides of the first capacitor
plate and the second capacitor plate such that the movement
of the skin exerts forces working from opposite directions on
the capacitor plates. This helps to equally distribute the
force among both the capacitor plates such that the capacitor
plates get closer.
According to another preferred embodiment, the sensor further
comprises a transmission means attached to the first
capacitor plate, wherein the transmission means is coupled to
the skin through the base member such that the transmission
means transmits a force provided by the movement of the skin
to the first capacitor plate to reduce the distance between
the capacitor plates.
According to another preferred embodiment, the sensor
comprises a flexible member, wherein the ends of the flexible
member is attached to the first capacitor plate and the
second capacitor plate, wherein the first supporting means
and the second supporting means is coupled to the flexible
member such that a movement of the skin exerts a tension on
the coupling to change the distance between the first
capacitor plate and the second capacitor plate.
According to yet another preferred embodiment, the first
capacitor plate and second capacitor plate is arranged
relatively parallel to the skin, wherein the first capacitor
plate is coupled to the skin such that the respiratory
movement of the skin pushes the first capacitor plate towards
the second capacitor plate. This results in a reduction of
distance between the capacitor plates, thereby changing the
capacitance.
According to yet another preferred embodiment, the change in
the relative arrangement of first capacitor plate and the
second capacitor plate is a movement of at least one
capacitor plate in a direction parallel to a surface of the
capacitor. This causes a change in the capacitance of the
capacitor.
According to another preferred embodiment, the first
capacitor plate and the second capacitor plate is flat. This
is the most commonly used as it acquires very less surface
area.
According to another preferred embodiment, the first
capacitor plate and second capacitor plate is spiral.
According to yet another preferred embodiment, the sensor
includes a separation means placed between the first
capacitor plate and the second capacitor plate. This prevents
the first capacitor plate and the second capacitor plate from
contacting each other.
According to yet another preferred embodiment, the sensor
further comprises an antenna to receive an electromagnetic
sender signal, wherein the antenna is electronically linked
to the capacitor such that an electromagnetic resonance
frequency of the antenna depends on the capacitance of the
capacitor. The resonant frequency is indicative of the
pressure applied on the base member due to the respiration.
This in turn helps to detect the mode of respiration.
According to yet another preferred embodiment, the antenna is
adapted to receive an electromagnetic sender signal, wherein
the antenna is electronically linked to the capacitor such
that an electromagnetic resonance frequency of the antenna
depends on the capacitance of the capacitor. This helps to
receive the signal at any sender frequency with no signal
losses.
According to yet another preferred embodiment, the sensor
comprises an energy storage adapted to store energy dependent
on the electromagnetic sender signal received by the antenna,
wherein the signal strength depends on the amount of energy
saved in the energy storage. This eliminates the need for any
external power supply means thereby reducing the cost
involved in timely replacement or maintenance.
Another aspect of the invention includes a respiratory
monitoring system comprising a sensor and a transceiver
adapted to transmit the electromagnetic sender signal to the
sensor and to receive the electromagnetic response signal
from the sensor. This simplifies the detection process as the
hardware and/or software in the monitoring system is simple
with no complex components.
According to yet another preferred embodiment, the
transceiver is adapted to vary the frequency of the
electromagnetic sender signal. This helps to determine the
exact frequency at which the strength of the signal attains a
higher value.
According to yet another preferred embodiment, the
transceiver comprises a signal measuring means adapted to
measure strength of the electromagnetic response signal and a
computing means adapted to determine relative maxima in the
strength of the electromagnetic response signal. This helps
to detect not only a normal breathing but also an irregular
breathing having a frequency different from that of the
normal breathing.
According to yet another preferred embodiment, the computing
means is adapted to determine the respiratory cycle based on
the intervals between the extrema. This helps to continuously
measure the respiration of the user with high accuracy.
According to yet another preferred embodiment, the computing
means is adapted to determine the resonance frequencies of
the capacitor based on the frequency of the electromagnetic
sender signal for which the strength of the electromagnetic
response signal reaches the relative maxima.
According to yet another preferred embodiment, the computing
means is adapted to determine the respiratory cycle based on
the development of the resonance frequency over time. This
helps to find the breath pattern of the patient.
The present invention is further described hereinafter with
reference to illustrated embodiments shown in the
accompanying drawings, in which:
FIG 1 illustrates a schematic view of a sensor for
measuring the respiration of a user according to an
embodiment of the invention;
FIG 2 illustrates a schematic circuit diagram of a
capacitor for use with the device of FIG. 1;
FIG 3 illustrates an alternative arrangement of the
capacitor of the sensor of FIG. 1;
FIG 4 illustrates an alternative arrangement of the
capacitor of the sensor of FIG. 1;
FIG 5 shows an exemplary illustration of an arrangement
of the capacitor of the sensor of FIG. 1;
FIG 6A-6B is an exemplary illustration of an alternative
arrangement of the capacitor of the sensor of
FIG.l;
FIG 7 is an exemplary illustration of an alternative
arrangement of the capacitor of FIG.l;
FIG 8 illustrates functioning of the capacitor of the
sensor of FIG.l;
FIG 9 illustrates a block diagram of a respiratory
monitoring system according to an embodiment of the
invention;
FIG lOA-lOE illustrates an explanatory diagram showing
variations in capacitance and frequency induced
during respiration;
FIG. 11 is a graph illustrating the computed power of the
electromagnetic response signal versus frequency of
the electromagnetic sender signal in accordance
with an embodiment of the invention; and
FIG. 12 is a graph explaining the periodicity of the
extrema of the electromagnetic response signal.
Various embodiments are described with reference to the
drawings, wherein like reference numerals are used to refer
to single elements throughout. In the following description,
for purpose of explanation, numerous specific details are set
forth in order to provide a thorough understanding of one or
more embodiments. It may be evident that such embodiments may
be practiced without these specific details.
The present invention thus provides a system that senses the
body movements of a person to determine parameters of
respiratory-related functions. The aforementioned parameters
can be used to diagnose a range of respiratory disorders.
Referring to FIG.l of the drawings, illustrates a schematic
view of a sensor 10 for measuring the respiration of a user
in accordance with an embodiment of the invention. The sensor
10 includes a capacitor 12 comprising of a first capacitor
plate 14 and. a second capacitor plate 16. The first capacitor
plate 14 and the second capacitor plate 16 are mechanically
coupled to the skin 17 of the user via a base member 18 fixed
onto the skin 17.
The base member 18 herein can be a flexible bandage such as a
plaster which can be attached to the body of the user. The
base member 18 includes an adhesive on one side which helps
to easily attach to the body or to remove the base member 18
from the body of the user at a location where the respiration
can be observed.
Here, the expansion and contraction of the skin 17 during the
respiration causes the base member 18 to expand and contract
simultaneously, thereby mechanically transferring the
respiration motion to the base member 18. The capacitor
plates 14, 16 is coupled to the base member 18 such that a
movement of the skin 17 during the respiration changes a
relative arrangement of the first capacitor plate 14 with
respect to the second capacitor plate 16 to vary the
capacitance of the capacitor 12. Here, the change in the
relative arrangement of first capacitor plate 14 and the
second capacitor plate 16 is a change in a distance between
the first capacitor plate 14 and the second capacitor plate
16.
The first capacitor plate 14 and second capacitor plate 16 is
connected to the spacing means 20 which hold the plates 14,
16 at a tension. The spacing means 20 is coupled to the base
member 18 such that the coupling works against the tension
during the respiration to change the distance between the
first capacitor plate 14 and second capacitor plates 16.
The first capacitor plate 14 and second capacitor plate 16
are in turn connected to a connecting means 22. the
connecting means 22 is coupled to the skin 17 in opposite
sides of the first capacitor plate 14 and the second
capacitor plate 16 such that the movement of the skin 17
exerts forceps working from opposite directions on the
capacitor plates 14, 16. This cause the capacitor plates 14,
16 to come closer thereby changing the capacitance of the
capacitor 12.
The sensor 10 further includes an antenna 30 to transmit and
receive electromagnetic signals. The antenna 30 is
electronically linked to the capacitor 12 such that an
electromagnetic resonance frequency of the antenna 30 depends
on the capacitance of the capacitor 12.
The sensor 10 further comprises an energy storage 32 adapted
to store energy from the electromagnetic sender signal 34 for
the operation of the sensor 10. The antenna 30 is adapted to
transmit the output signal dependent on the capacitance of
the capacitor 12. The antenna 30 transmits the output signal
in the form of an electromagnetic response signal 36 with
signal strength dependent on the capacitance of the capacitor
12. The signal 36 strength depends on the amount of energy
saved in the energy storage 32.
FIG 2 illustrates a schematic circuit diagram of a capacitor
12 for use with the sensor 10 of FIG. 1. The capacitor 12
includes a first capacitor plate 14 and a second capacitor
plate 16. The two ends of the first capacitor plate 14 and
the second capacitor plate 16 is connected to a spacing means
20. The spacing means 20 is arranged so as to hold the first
capacitor plate 14 and the second capacitor plate 16 apart at
a tension.
The capacitor 12 arrangement further comprises a connecting
means 22. The connecting means 22 holds the ends of the first
capacitor plate 14 and the second capacitor plate 16
together. The connecting means 22 can be for instance wires,
co-axial cables, springs or the like. The connecting means 22
is further coupled to the base member 18 through the spacing
means 20.
The connecting means 22 is coupled to the skin 17 in opposite
sides of the first capacitor plate 14 and the second
capacitor plate 16 such that the movement of the skin 17
exerts forces working from opposite directions on the first
capacitor plate 14 and second capacitor plate 16 to change
the distance between the capacitor plates 14,16. As the
capacitor plates 14, 16 are held by the spacing means 20
which is flexible, it makes it easy to transfer the force
generated based on the pull from the connecting means 22
during respiration to the capacitor plates 14, 16. This in
turn varies the capacitance and hence the tuning frequency of
the capacitor 12.
The capacitor 12 is further provided with a separation means
28 between the first capacitor plate 14 and the second
capacitor plate 16. The separation means 28 prevents the
capacitor plates from touching each other when they are
pulled closei:.
The capacitor 12 herein is shaped, sized and contoured to
substantially match the planar surface of the base member 18.
In the preferred embodiment, the capacitor plates 14, 16
includes a strip of copper, silver or gold or other
conductive materials that may be used to form the capacitor
plates 14,16. Alternatively, the capacitor plates 14, 16 may
be etched from a copper-clad substrate or screened and fired
using thick-film techniques, using procedures well known for
the fabrication of printed circuits.
FIG 3 illustrates an alternative arrangement of the capacitor
12 of the sensor 10 of FIG.l. As shown in FIG. 3, the first
capacitor plate 14 and the second capacitor plate 16 are
connected to a connecting means 22. The capacitor plates 14,
16 are spaced apart at a certain tension by the spacing means
20.
The connecting means 22 herein is further coupled to the base
member 18 of the sensor 10 attached to the skin 17 of the
user. The respiration motion of the user causes expansion of
the skin 17.. This move of the skin 17 causes a sideward
pulling of the connecting means 24 in a direction parallel to
the capacitor 12. This sideward pulling exerts a force which
works against the tension at which the capacitor plates 14,
16 are held.. The sideward pulling of the connecting means 22
forces the first capacitor plate 14 and the second capacitor
plate 16 to come closer, thereby reducing the distance
between the plates 14, 16. The reduction of distance in turn
changes the capacitance of the capacitor 12.
FIG 4 illustrates another arrangement of the capacitor 12 of
the sensor 10 of FIG.l. The first capacitor plate 14 and the
second capacitor plate 16 are arranged horizontally parallel
to each other. The connecting means 22 attached to each of
the capacitor plate 14, 16 holds the capacitor plates 14, 16
at a tension certain distance apart. As shown in FIG. 4, a
transmission means 26 is attached to each of the first
capacitor plate 14 and the second capacitor plate 16.
The transmission means 26 is coupled to a base member 18. The
first capacitor plate 14 and the second capacitor plate 16
are coupled to the base member 18 through the transmission
means 26 and the connecting means 22. Here the connecting
means 22 and the transmission means 26 can be a flexible body
such as a string or a spring attached to the base member 18.
The expansion of the skin 17 during respiration exerts a
stretching force on the transmission means 26 coupled to the
flexible member 24. The transmission means 26 attached to
the first capacitor plate 14 pushes the first capacitor plate
14 towards the second capacitor plate 16. The force exerted
in opposing directions causes the first capacitor plate 14
and the second capacitor plate 16 to come closer, thereby
reducing the distance between the capacitor plates. This in
turn changes the capacitance and the tuning frequency of the
capacitor 12.
Alternatively, the transmission means 26 attached to the
second capacitor plate 16 pulls forward the second capacitor
plate 16 towards the first capacitor plate 14. This also
reduces the distance between the capacitor plates 14, 16.
FIG 5 shows an exemplary illustration of the capacitor 12 of
the sensor 10 of FIG.l. The first capacitor plate 14 and the
second capacitor plate 16 is held apart at a tension using
the spacing means 20. The first capacitor plate 14 and the
second capacitor plate 16 are further coupled to a flexible
member 24 which functions as a connecting means.
The flexible member 24 can be a flexible elastic band. The
expansion of the skin 17 during respiration exerts a
stretching force on the elastic band coupled to the skin.
This in turn causes pushes the first capacitor plate 14
towards the second capacitor plate 16. Here the capacitance
of the capacitor changed by the movement of at least one of
the capacitor plate towards the other thereby reducing the
distance between the plates 14, 16.
FIG 6A-6B is an exemplary illustration of an alternative
arrangement of the capacitor 12 of the sensor 10 of FIG.l.
The figure 6A shows the outer surface of the skin 17 on which
the sensor 10 is placed. Here the first capacitor plate 14
and second capacitor plate 16 is arranged relatively parallel
to each other on the skin 17 and are mechanically coupled to
the base member 18 using a connecting means 22.
The expansion of the skin 17 during a respiration motion
exerts a stretch on the base member 18 which induce a tension
on the coupling. The stretching pushes the second capacitor
plate 15 towards the first capacitor plate 14 as shown in
FIG. 5B. This causes to reduce the distance between the first
capacitor plate 14 and the second capacitor plate 16.
FIG 7 is an exemplary illustration of an alternative
arrangement of the capacitor 12 of FIG.l. Here the first
capacitor plate 12 and the second capacitor plate 16 are
arranged in a spiral form as shown in FIG. 7. The first
capacitor plate 14, the second capacitor plate 16 and the gap
between the plates and the base member 18 forms a capacitor
having a characteristic capacitance.
One end of each of the first capacitor plate 14 and the
second capacitor plate 16 is attached to a connecting means
22 such as a string. The end of the first capacitor plate 14
and the second capacitor plate 16 is thus coupled to the base
member 18 through the connecting means 22.
The gap between the two spiral capacitor plates 14, 16 are
provided wirh a separation means 22. The separation means 22
prevents the physical contact of the first capacitor plate 14
and the second capacitor plate 16 during the sensor 10
operation. The separation means 22 can be for example sponge
or any similar non-conductive material.
The respiration motion causes a stretching of the base member
18 which in turn pulls the first capacitor plate 14 and the
second capacitor plate 16 closer. This reduces the gap
between the plates thereby changing the capacitance of the
capacitor 12.
FIG 8 illustrates functioning of the capacitor 12 of the
sensor 10 of FIG.l. The first capacitor plate 14 and the
second capacitor plate 16 are arranged flat on the base
member 18. The first capacitor plate 14 and the second
capacitor plate 16 are mechanically coupled to the skin 17 of
the user such that a force generated due to the movement of
the skin 17 during respiration is transferred to the
capacitor 12.
The movement of the skin 17 during the respiration thus
changes a relative arrangement of the first capacitor plate
14 with respect to the second capacitor plate 16 to vary the
capacitance of the capacitor 12. The change in the relative
arrangement of first capacitor plate 14 and the second
capacitor plate 16 is a movement of at least one capacitor
plate in a direction parallel to a surface of the capacitor
as shown in the FIG.8.
Here the sideward shift of at least one capacitor plate in a
direction parallel to the other capacitor plate results in a
change in the capacitance of the capacitor.
FIG 9 illustrates a block diagram of a respiratory monitoring
system 38 according to an embodiment of the invention. The
respiratory monitoring system 38 of FIG. 9 comprises a sensor
10 and a transceiver 40 adapted to transmit an
electromagnetic sender signal 34 to the sensor 10 and to
receive the electromagnetic response signal 36 from the
sensor 10.
The transceiver 40 is adapted to transmit the electromagnetic
sender signal 34 at a particular frequency in a direction of
the user's body. The antenna 30 of the sensor 10 receives the
electromagnetic sender signal 34 at the transmitted
frequency. The sensor 10 analyzes the power at which the
electromagnetic sender signal 34 is received. When the
frequency of ~he electromagnetic sender signal 34 received at
the sensor marches with the tuning frequency of the capacitor
12, resonance occurs and the power of the electromagnetic
sender signal 34 is the highest. The energy storage 32 of the
sensor 10 then stores power for the operation of the sensor
10.
The power stored in the energy storage 32 is used to transmit
the electromagnetic response signal 36 to the transceiver 40.
The strength of the electromagnetic response signal 36 is
thus proportional to the amount of energy stored in the
energy storage 32.
The transceiver 40 includes a signal measuring means 42
adapted to measure strength of the electromagnetic response
signal 36. The transceiver 40 further includes a computing
means 4 4 adapted to determine adapted to determine relative
maxima in the strength of the electromagnetic response
signal. The computing means 44 is adapted to determine the
resonance frequencies of the capacitor 12 based on the
frequency of the electromagnetic sender signal 34 for which
the strength of the electromagnetic response signal 36
reaches the relative maxima.
The computing means 4 4 further determine the respiratory-
cycle based on the intervals between the maxima. The
respiratory cycle is determined based on the development of
the resonance frequency over time. The computing means 4 4
analyzes the cycles of the electromagnetic response signal 36
to determine? where the signal 36 is increasing and decreasing
in frequency and to measure a time interval between extrema
of two adjacent cycles of the electromagnetic response signal
36 to determine duration of one respiration motion.
FIG lOA - lOE illustrates an explanatory diagram showing
variations in capacitance and frequency. The various patterns
of the movement of the skin 17 due to the respiration motion
and the corresponding change in the relative arrangement of
the capacitor plates 14, 16 is shown in FIG lOA - lOE.
Different respiratory states of the user produce different
patterns of the capacitor plate displacements.
The waveforms in lOA-lOE shows frequency of the
electromagnetic response signal 36 from the sensor 10
corresponding to the capacitance of the capacitor 12. The
waveforms indicate frequency distribution for various
respiration patterns such as normal inhalation, normal
exhalation, obstructed inhalation, early inhale/exhale, late
inhale/exhale associated with respiration of a user.
The transceiver 40 analyzes the respiratory motion from these
waveforms to determine the resonant frequency.
FIG. 11 is a graph illustrating the computed strength of the
electromagnetic response signal 36 versus frequency of the
electromagnetic sender signal 34 in accordance with an
embodiment of the invention.
The signal measuring means 42 of the transceiver 40 measures
the output power of the electromagnetic response signal 36
corresponding to the capacitance of the sensor capacitor 12
representing the respiration of the user. The computing means
44 associated with the transceiver 40 further scans the power
of the electromagnetic response signal 36 at various
frequencies of the electromagnetic sender signal 34 at which
it is transmitted to the sensor 10. The computing means 44
further estimates the frequency of the electromagnetic sender
signal 34 where the maximum power of the electromagnetic
response signal 36 is scattered.
This frequency is noted as the peak frequency. The peak
frequency is for example, a frequency having maximum power in
case where the sensor signal is converted into the power
spectrum. Here, the peak frequency is obtained at a resonance
when the scanned frequency matches with the transmitted
frequency of the electromagnetic sender signal 34.
FIG. 11 is a graph explaining the periodicity of the relative
maxima of the electromagnetic response signal 36. The
processor 46 computes the respiration on the basis of the
electromagnetic response signal 36 outputted from the sensor
10.
The movement of the skin during respiration causes a change
in the resonant frequency. This in turn changes the frequency
of the maximum power transferred. The plot of peak frequency
of the electromagnetic response signal 36 versus time
interval between the extrema of two adjacent cycles gives the
respiration cycle of the user.
The processor 46 analyze the cycles of the electromagnetic
response signal 36 to determine where the signal is
increasing and decreasing in frequency. The breathing cycle
includes multiple extrema including maximum values and
minimum values. The measurement of the time interval between
extrema of two adjacent cycles of the electromagnetic
response signal 36 provides the duration of one respiration
motion. This helps to analyze how much time lag is respective
succession of inhaling or exhaling.
The system 38 described herein is highly accurate owing to
the mode of sensing, does not require extra power storage and
hence makes it more user friendly, environment friendly and
requires less maintenance. The motion artifacts do not hamper
the system performance since the sensor only measures the
stretching and contraction. The usage of wireless
transmission obviates the need for line of sight. The sensor
is very compact in a bandage form with thin form factor less
than 1mm thickness and poses less discomfort to the user.
Multiple such sensors can be placed onto the patient to
obtain accurate measurements of the respiration rate.
The sensor can be used for continuous respiration monitoring
as it is attached to the persons body. This makes it easy to
alert the doctor using standing communication protocols such
as mobile phone when the respiration rate shows anomalies.
The circuitry of the transceiver is small and is adapted to
obtain information from a multitude of sensors in the
vicinity. The cost of the system is less, especially
appealing to mass markets.
The embodiment described herein finds extensive application
in healthcaire areas. For instance, it can be used to monitor
breathing rate of babies and infants especially in the case
of pneumonia. The breath rates of each baby can be wirelessly
monitored and can be displayed on a computer or an alarm can
be generated. This facilitates monitoring of the patients
remotely from elsewhere both when they are asleep or in
motion. Further, respiration rate of sports players and
athletes can be continuously determined to study and improve
their performance.
Patent claims
1. A sensor (10) for measuring a respiration of a user,
wherein the sensor (10) comprises:
- a capacitor (12) comprising of a first capacitor plate (14)
and a second capacitor plate (16), the first capacitor plate
(14) and the second capacitor plate (16) being coupled to a
skin (17) of the user such that a movement of the skin (17)
during the respiration changes a relative arrangement of the
first capacitor plate (14) with respect to the second
capacitor plate (16) to vary the capacitance of the capacitor
(12); and
- a means to generate an output signal (36) dependent on the
capacitance.
2. The sensor (10) according to claim 1, wherein the first
capacitor plate (14) and the second capacitor plate (16) are
coupled to the skin (17) via a base member (18) fixed onto
the skin (17).
3. The sensor (10) according to claim 1 or 2, wherein the
change in the relative arrangement of the first capacitor
plate (14) and the second capacitor plate (16) is a change in
a distance between the first capacitor plate (14) and the
second capacitor plate (16).
4. The sensor (10) according to claim 3, wherein the first
capacitor plate (14) and the second capacitor plate (16) are
connected to a spacing means (20) which holds the capacitor
plates (14, 16) at a tension, wherein the capacitor plates
(14, 16) are coupled to the skin (17) such that the movement
of the skin (17) exerts a force against the tension to change
the distance between the first capacitor plate (14) and the
second capacitor plate (16).
5. The sensor (10) according to claim 4, further comprises a
connecting means (22) attached to the first capacitor plate
(14) and the second capacitor plate (16), wherein the
connecting means (22) is coupled to the skin (17) in opposite
sides of the first capacitor plate (14) and the second
capacitor plate (16) such that the movement of the skin (17)
exerts a force working from opposite directions on the
capacitor plates (14, 16).
6. The sensor (10) according to any of the claims 3 to 5,
further comprises a transmission means (26) attached to the
first capacitor plate (14), wherein the transmission means
(26) is coupled to the skin (17) through the base member (18)
such that the transmission means (26) transmits a force
provided by the movement of the skin (17) to the first
capacitor plate (14) to reduce the distance between the
capacitor plates (14, 16).
7. The sensor (10) according to any of the claims 3 to 6,
further comprises a flexible member (24), wherein the first
capacitor plate (14) and the second capacitor plate (16) is
coupled to the flexible member (24) such that the respiratory
movement of the skin (17) pushes the first capacitor plate
(14) towards the second capacitor plate (16).
8. The sensor (10) according to any of the claims 1 to 7,
wherein the first capacitor plate (14) and second capacitor
plate (16) is arranged relatively parallel to the skin (17),
wherein the first capacitor plate (14) is coupled to the skin
(17) such that the respiratory movement of the skin (17)
pushes the first capacitor plate (14) towards the second
capacitor plate (16).
9. The sensor (10) according to any of the claims 1 to 8,
wherein the change in the relative arrangement of first
capacitor plate (14) and the second capacitor plate (16) is a
movement of at least one capacitor plate (14,16) in a
direction parallel to a surface of the capacitor (12) .
10. The sensor (10) according to any of the claims 1 to 9,
wherein the first capacitor plate (14) and the second
capacitor plate (16) are flat.
11. The sensor (10) according to any of the claims 1 to 10,
wherein the first capacitor plate (14) and second capacitor
plate (16) are spiral.
12. The sensor (10) according to any of the claims 1 to 11,
further comprises a separation means (28) placed between the
first capacitor plate (14) and the second capacitor plate
(16) to prevent contact of the first capacitor plate (14) and
second capacitor plate (16).
13. The sensor (10) according to any of the claims 1 to 12,
further comprises an antenna (30) to receive an
electromagnetic sender signal (34), wherein the antenna (30)
is electronically linked to the capacitor (12) such that an
electromagnetic resonance frequency of the antenna (30)
depends on the capacitance of the capacitor (12).
14. The sensor (10) according to claim 13, wherein the
antenna (30) is adapted to transmit the output signal in the
form of an electromagnetic response signal (36) with a signal
strength dependent on the capacitance of the capacitor (12).
15. The sensor (10) according to claim 14, further comprises
an energy storage (32) adapted to store energy dependent on
the electromagnetic sender signal (34) received by the
antenna (30), wherein the signal strength depends on the
amount of energy saved in the energy storage (32).
16. A respiratory monitoring system (38) comprising:
- a sensor (10) according to any of the claims 14 to 16; and
- a transceiver (40) adapted to transmit the electromagnetic
sender signal (34) to the sensor (10) and to receive the
electromagnetic response signal (36) from the sensor (10).
17. The system (10) according to claim 16, wherein the
transceiver (40) is adapted to vary the frequency of the
electromagnetic sender signal (34).
18. The system (10) according to claim 16 or 17, wherein the
transceiver (40) comprises:
- a signal measuring means (42) adapted to measure a strength
of the electromagnetic response signal (36); and
- a computing means (44) adapted to determine relative
extrema in the strength of the electromagnetic response
signal (36).
19. The system (10) according to claim 18, wherein the
computing means (44) is adapted to determine the respiratory
cycle based on the intervals between the extrema.
20. The system (10) according to claim 19, wherein the
computing means (44) is adapted to determine the resonance
frequencies of the capacitor (12) based on the frequency of
the electromagnetic sender signal (34) for which the strength
of the electromagnetic response signal (36) reaches the
relative maxima.
21. The system (10) according to claim 20, wherein the
computing mesans (44) is adapted to determine the respiratory
cycle based on the development of the resonance frequency
over time.

A sensor for measuring a respiration of a user, wherein the
sensor comprises a capacitor comprising of a first capacitor
plate and a second capacitor plate, the capacitor plates
being coupled to a skin of the user such that a movement of
the skin during the respiration changes a relative
arrangement of the first capacitor plate with respect to the
second capacitor plate to vary the capacitance of the
capacitor and a means to generate an output signal dependent
on the capacitance is disclosed. The change in the relative
arrangement of first capacitor plate and the second capacitor
plate is a change in a distance between the first capacitor
plate and the second capacitor plate.