U.S. patent application number 16/851462 was filed with the patent office on 2020-07-30 for apparatus and method for the detection of the body position while sleeping.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Rene Martinus Maria DERKX, Jia DU, Gary Nelson GARCIA MOLINA, Adrienne HEINRICH, Henriette Christine VAN VUGT.
Application Number | 20200237261 16/851462 |
Document ID | 20200237261 / US20200237261 |
Family ID | 1000004765689 |
Filed Date | 2020-07-30 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200237261 |
Kind Code |
A1 |
HEINRICH; Adrienne ; et
al. |
July 30, 2020 |
APPARATUS AND METHOD FOR THE DETECTION OF THE BODY POSITION WHILE
SLEEPING
Abstract
The invention relates to a method and an apparatus for the
detection of the body position, especially while sleeping. More
particularly, the invention relates to how the main body positions
during sleep can be derived from the distribution of the reflection
of a projected IR light from a subject's body under a blanket.
Additionally, the breathing signals can be analyzed to determine
the body posture.
Inventors: |
HEINRICH; Adrienne; (DEN
BOSCH, NL) ; VAN VUGT; Henriette Christine;
(ULTRECHT, NL) ; DERKX; Rene Martinus Maria;
(EINDHOVEN, NL) ; GARCIA MOLINA; Gary Nelson;
(MADISON, WI) ; DU; Jia; (WAALRE, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
Eindhoven |
|
NL |
|
|
Family ID: |
1000004765689 |
Appl. No.: |
16/851462 |
Filed: |
April 17, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16203904 |
Nov 29, 2018 |
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16851462 |
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14117385 |
Nov 13, 2013 |
10159429 |
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PCT/IB2012/052671 |
May 29, 2012 |
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16203904 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/4818 20130101;
A61B 5/1113 20130101; A61B 7/04 20130101; A61B 5/1116 20130101;
A61B 5/113 20130101; A61B 2503/04 20130101; A61B 5/4806 20130101;
G08B 21/0476 20130101; A61B 5/1128 20130101; A61B 5/0075 20130101;
A61B 5/1118 20130101; A61B 7/003 20130101; A61B 5/0077 20130101;
A61B 5/70 20130101 |
International
Class: |
A61B 5/11 20060101
A61B005/11; A61B 5/00 20060101 A61B005/00; A61B 5/113 20060101
A61B005/113; A61B 7/00 20060101 A61B007/00; A61B 7/04 20060101
A61B007/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2011 |
EP |
11305656.8 |
Claims
1. A method for detection of a posture of a body, the method
comprising: providing a bedding; wherein the bedding lies upon a
body; identifying a plurality of segments of the body; projecting a
pattern of electromagnetic radiation at least on a part of the
bedding; detecting a reflection pattern of the projected pattern
caused by reflections from the bedding; comparing the reflection
pattern with a plurality of predefined reflection patterns
representing a corresponding plurality of body postures; and
determining the posture of the body based on the comparison of the
reflection pattern with the plurality of predefined reflection
patterns; and recording the posture of the body over time for
subsequent diagnoses; wherein the reflection pattern includes a
plurality of reflection magnitudes; wherein each of the plurality
of reflection magnitudes correspond to reflections from
corresponding segments of the body; and wherein each of the
predefined reflection patterns include a plurality of predefined
reference magnitudes corresponding to each segment of the body at
each corresponding body posture.
2. The method of claim 1, wherein the segments of the body include
at least two of: upper body part, middle body part, and bottom body
part.
3. The method of claim 1, wherein a light source for the projection
of the pattern of electromagnetic radiation comprises a laser
device; wherein the laser device is a solid state device; and
wherein the laser device emits light in the infrared spectrum.
4. The method of claim 1, wherein the projecting of the pattern of
electromagnetic radiation comprises projecting the pattern of
electromagnetic radiation intermittently.
5. The method of claim 1, wherein the detecting of the reflection
of the pattern of electromagnetic radiation is via a low-resolution
sensor array.
6. The method of claim 1, wherein, in addition to the reflections
from the bedding, one or more additional information items are
considered for the determining of the body posture.
7. The method of claim 6, wherein the one or more additional
information items include breathing amplitude information.
8. The method of claim 7, wherein the breathing amplitude
information is based on images of the body from a video signal.
9. The method of claim 6, wherein the one or more additional
information items include acoustical information that is retrieved
via at least two microphones positioned on both sides of the
bedding.
10. The method of claim 9, wherein the determining of the posture
of the body is based on heuristics; wherein the heuristics include
an orientation of one or more light sources that project the
pattern of electromagnetic radiation; and wherein the heuristics
include an orientation of one or more sensors that detect the
reflection of the projected pattern.
11. The method of claim 6, wherein the one or more information
items include movement information.
12. An apparatus comprising: a projector that projects a pattern of
electromagnetic waves on a bedding; wherein the bedding lies upon a
body; a detector that detects a reflection pattern of the pattern
of electromagnetic waves; a data processor that: compares the
reflection pattern to a plurality of predefined reflection
patterns; determines the posture of the body based on the
comparison of the reflection pattern with the plurality of
predefined reflection patterns; and records the posture of the body
over time for subsequent diagnoses; wherein the reflection pattern
includes a plurality of reflection magnitudes; wherein each of the
plurality of reflection magnitudes correspond to reflections from
corresponding segments of the body; and wherein each of the
predefined reflection patterns include a plurality of predefined
reference magnitudes corresponding to each segment of the body at
each corresponding body posture.
13. The apparatus of claim 12, further comprising at least one
microphone connected to the data processor.
14. The apparatus of claim 12, wherein the projector comprises a
laser device; wherein the laser device is a solid state device; and
wherein the laser device emits light in the infrared spectrum.
15. The method of claim 2, wherein the upper body part comprises an
upper left body part and an upper right body part; wherein the
middle body part comprises a middle left body part and a middle
right body part; and wherein the lower body part comprises a lower
left body part and a lower right body part.
16. The method of claim 1, wherein the projecting of the pattern of
electromagnetic radiation includes modulating the electromagnetic
radiation.
17. The method of claim 6, wherein the one or more additional
information items include acoustical information.
18. The method of claim 1, wherein each reflection magnitude and
each reference reflection magnitude is a binary value.
19. The method of claim 1, comprising diagnosing a physical health
condition based on the determined posture of the body.
20. The method of claim 1, comprising controlling an environmental
situation of the body based on the determined posture of the body.
Description
CROSS-REFERENCE TO PRIOR APPLICATIONS
[0001] This application is a Continuation of Ser. No. 16/203,904
filed Nov. 29, 2018 which is a continuation of Ser. No. 14/117,385,
filed on Nov. 13, 2013, which is the U.S. National Phase
application under 35 U.S.C. .sctn. 371 of International Application
No. PCT/IB2012/052671, filed on May 29, 2012, which claims the
benefit of European Patent Application No. 11305656.8, filed on May
30, 2011. These applications are hereby incorporated by reference
herein.
FIELD OF THE INVENTION
[0002] The invention relates to methods and apparatus for the
detection of the body position, especially while sleeping. More
particularly, the invention relates to how the main body positions
during sleep can be derived from the distribution of the reflected
IR light from the person's body under the blanket. Additionally,
the breathing signal can be analyzed to determine the body
posture.
BACKGROUND OF THE INVENTION
[0003] Detection of the body position while sleeping enables
improved unobtrusive monitoring. When an image sensor is used as an
off-body motion sensor, motion detection or estimation is typically
applied to measure the activity level and replace actigraphs. When
e.g. two persons share the bed (65% of the adult US population
sleep together with a partner or children) the movements can be
easier discerned when the body position is known. Motion detection
alone is not sufficient for the shared-bed scenario since the areas
of motion cannot indicate sufficiently well which motion areas
belong to which subject when the two subjects lie close to each
other. Motion estimation, where motion vectors are computed per
image block, help, but only in cases when the two subjects do not
move similarly in the border area. The body position can indicate
which movements are likely to belong to one subject and which
movements belong to the other subject.
[0004] Moreover, several other benefits regarding the body position
information exist, particularly regarding sleep and health. These
benefits are [0005] Enable more robust positional apnea detection:
Obstructive sleep apnea (OSA) is the most common category of
sleep-disordered breathing. In some patients with OSA, the severity
of their apnea and sleep disturbance as measured by the Respiratory
Disturbance Index (RDI) is twice as high or more when sleeping on
their backs (the supine position) compared to sleeping on their
sides (the lateral position). This is referred to as Positional
Sleep Apnea ("PSA"). By contrast, patients with less or no change
in their RDI related to sleeping position are said to have
Nonpositional Sleep Apnea ("NSA"). A device designed based on the
instant application may help treating patients diagnosed with PSA
and increase their and their doctor's insight into the severity and
possible progression of their disease. Many people suffering from
OSA benefit from sleeping at a 30-degree elevation of the upper
body or higher, as if in a recliner. This helps prevent the
gravitational collapse of the airway. Lateral positions (sleeping
on one's side), as opposed to supine positions (sleeping on the
back) are also recommended as a treatment for sleep apnea. Indeed,
the gravitational component is smaller in the lateral position than
in the supine positions. [0006] Coaching solutions: Body position
may be included as a parameter and a user is coached/influenced to
bias body positions leading to better sleep quality. The
relationship between body position and sleep quality is recognized
in the field of sleep research; [0007] Poor sleepers spend longer
on their backs with their head straight than good sleepers do;
[0008] People who sleep face downwards, on their stomach or on
their side, weigh heavily on their jaws with static load, this
incorrect position over years can cause symptoms such as migraine,
trigeminal neuralgia, pain, hum, tension, and/or dizziness; [0009]
Sleep on one's side can ease the symptoms of apnea.
[0010] Complex solutions involving human models and pose
recognition exist for detecting the body position of the sleeping
person with a camera. They are, however, computationally more
complex and only work with a thin blanket where the outline of the
person is well visible. Further, such methods do not work for all
major body positions (e.g. the distinction between on the stomach
and on the back cannot be made).
[0011] US20070118054 discloses a method and a system for monitoring
vital signs for the prediction and treatment of physiological
ailments. In this patent application only the changes in the
posture of the body are considered and are estimated from
physiological signals. Methods and systems for monitoring vital
signs for the prediction and treatment of physiological ailments
are provided. The methods and systems disclosed may be applied to
the monitoring of a broad range of physiological ailments or
"episodes," including, but not limited to, asthma, hypoglycemia,
coughing, edema, sleep apnea, labor, and REM sleep stages. The
methods employ sensors, for example, non-contact sensors, adapted
to detect vital signs, such as heart rate or respiration rate, to
produce signals that can be analyzed for trends, deviations, or for
comparison to prior conditions or criteria. The sensors may be
positioned whereby the subject need not be viewed by a health care
provider. Some methods and systems employ the use of "scores" based
upon a combination of sensed vital signs or based upon a comparison
of the vital signs to standard criteria.
[0012] WO2009/083017 discloses a movement detector for detecting
the movement of a breathing activity. To enhance a movement
detector for detecting the movement of a body breathing or
heartbeat activity comprising a Doppler sensor with a microwave
oscillator and at least one mixer in such a manner, that the
detector is on the one hand efficient and safe with respect to a
baby breathing or heartbeat detection and on the other hand a low
cost solution, the sensor is performed as a sensor unit with a
volume less than 100 cm and a sending energy lower than 10 mW.
[0013] U.S. Pat. No. 5,914,660 discloses a position monitor and
alarm apparatus for reducing the possibility of sudden infant death
syndrome. A device for reducing the possibility of sudden infant
death syndrome (SIDS) as disclosed comprises a position-indicating
device effectively coupled to a signal-producing circuit and
attached to the clothing of the infant. The position indicating
device provides signals, varying in response to prone and other
positions assumed by the infant during sleep, allowing an
associated alarm device to be activated in response to the infant's
assuming a SIDS-dangerous prone or side-position. In one
embodiment, the position of the infant can be determined by an
optical sensor interacting with a reflective or other marker
adhered to the infant. Gravity or pressure switches may also be
used to provide position-responsive signals. A signal generated
upon assumption of the SIDS-dangerous prone or side-positions is
transmitted to a remote receiver located proximate the infant's
care-giver whereupon an alarm is generated to indicate the need to
reposition the infant. A constant low-level or intermitted
maintenance signal can be produced to assure the continued and
proper operation of the apparatus. An additional awakening alarm
can be produced near the sleeping infant to further reduce the
likelihood of a SIDS event.
[0014] US2010/0262026 discloses a method for the detection of the
sleep position. The method as disclosed in US2010/0262026 uses ECG
sensors at fixed positions, not fixed to the patient. The ECG
signals recorded from the sensors are used to detect body position,
using the variation of ECG potential over the surface of the body.
The results may be processed by measuring artifacts related to the
angle between the sensors and the heart, in particular the polarity
of the QRS complex. The sensors may be fixed on the upper surface
of a bed and used to monitor the sleep position.
SUMMARY OF THE INVENTION
[0015] It is therefore the object of the invention to provide a
method as well as a device enabling a contactless detection of a
body's posture, especially while sleeping.
[0016] With respect to the method, this object is achieved by a
method for the detection of the posture of a body, especially while
sleeping, the method comprising the steps of: [0017] providing a
bedding; [0018] projection of a pattern of electromagnetic
radiation at least on a part of said bedding; [0019] detection of
the reflection of the projected pattern caused by a body laying on
said bedding; [0020] comparing the reflection pattern with
reflection pattern representing typical body postures.
[0021] The term bedding as used in this context should be
understood as any kind of device enabling a subject to rest his or
her body, e.g., a bed, a mattress, a deck-chair, or any other kind
of lie down area, while the term subject refers to human or
animal.
[0022] The phrase electromagnetic radiation refers to light at the
visible wavelength, e.g. about 380 nm to about 780 nm, as well as
electromagnetic radiation at a wavelength outside the range visible
to the unaided human eye, e.g., IR-radiation at a wavelength within
a range of about 780 nm to about 1 mm.
[0023] By comparison of a reflection pattern with reflection
patterns representing typical body postures, the position of a body
while sleeping can be determined in a contactless way without
disturbing the subject monitored in during his or her sleep. The
projection of the pattern facilitates the comparison of the
detected reflection pattern with patterns representing typical body
postures. The distribution of the reflected light is used to
determine the body position. When the person lies flat in bed (e.g.
in the prone, royal, Cyclops, Waterwings positions, see FIG. 1),
the reflected intensity is more evenly distributed from the top to
the lower part of the body whereas on the side, the reflected
intensity is clearly higher around the middle and top (see FIG. 2
for examples) for the given light projector.
[0024] According to a preferred embodiment of the invention, for
comparing the reflected pattern with the pattern representing
typical body postures the person's body is virtually segmented into
6 major parts: Upper body left and right, middle part left and
right, bottom part left and right, of which the sum of the present
intensity is computed. Heuristics can be derived based on the
location of the light projector. Basically, the reflected light has
a higher intensity the smaller the distance between the light
projector and the object since the light is reflected back
quicker.
[0025] When the person lies flat, either on the belly or on the
back, the distribution of the light is hardly altered by a person
in bed compared to only the blanket pulled over the bed. However,
when the person turns to one side, the upper and middle part of the
body change the reflectance in the corresponding area (to larger or
lower depending on from where the light is shining and which parts
become occluded, due to e.g., legs pulled up, one side of the body
blocking other side of the bed). This can be used to derive
heuristics to determine the body position of a sleeping person.
[0026] According to a preferred embodiment of the invention, as the
light source for the projection of the pattern a laser is used. The
use of a laser as a light source enables a sharp projection of a
pattern. Preferably, the laser operates at a wavelength which is
outside the range that is visible to, or harmful for, the human
eye, e.g., in the IR-wavelength range. Preferably, an IR-laser is
used that operates at a wavelength of 808 nm to 1064 nm. The energy
of the laser used as light source is preferably low enough to
ensure avoidance of eye damage caused by laser radiation.
Especially preferred, an IR-LED-laser is used as a light
source.
[0027] In a further preferred embodiment of the invention, the
projection of the pattern on said bedding is performed in an
intermittent and/or modulated way. The projection may be performed
e.g. once a minute, once every 10 second, or once a second, etc.
Performing the projection of the pattern in an intermittent way can
reduce discomfort caused by a permanent projection of the pattern.
In another embodiment, the projection is modulated in its
intensity. By doing so, discomfort caused by the projection can be
reduced, too.
[0028] In another embodiment the projection is modulated in its
frequency. This may reduce interferences caused by other light
sources, e.g., night lights etc. Frequency modulation may be
performed by using at least two different projectors, like e.g. two
IR-LED-lasers emitting at different frequencies, e.g. 808 nm and
1064 nm. The at least two different projectors may project in an
alternating way.
[0029] The detection of the reflection can be performed by video
analysis of the pattern projected on the bedding. In a preferred
embodiment of the invention, a CCD-sensor is used for the detection
the reflection of the pattern. In an even more preferred embodiment
of the invention, a low resolution sensor array is used for the
detection of the reflection of the pattern. A low resolution sensor
in this concern refers to sensors having a resolution of e.g., 125
cpi to 1375 cpi, preferably about 500 cpi, as are used in optical
mouse sensors. Due to the reduced information needed for the
detection of the body posture, the higher resolution image from a
camera is not needed. By using low resolution sensors, the amount
of data to be processed can be reduced, while also the privacy of
the sleeping person can be preserved since the low resolution image
disables identification of the person lying on the bedding.
[0030] According to another embodiment of the invention, additional
information is used to determine the body posture more accurately.
In an embodiment of the invention, acoustical information and/or
information on the breathing amplitude is used to increase the
accuracy of the body posture determination. When a flat body
position is detected on the basis of the reflected pattern, to
distinguish on the back from on the belly, the respiration analysis
output can be included. The breathing characteristics extracted
from a video signal are different when the person lies on the belly
compared to when the person lies on the back. When the person lies
on the back, the chest is free to move into open space without any
large barrier blocking its movement. However, when the person is on
the belly, the chest movement goes into the mattress and the
amplitude perceived by the video is reduced. Empirically, 25%
higher breathing amplitude is measured when a subject is on his
back than on his stomach. The decline in the breathing amplitude
towards the end of the `back` sequence is assumed due to the more
relaxed state of the subject with more shallow breathing (reduced
air flow and chest expansion). When the side position is detected
on the basis of the reflected pattern, the body orientation can be
robustly determined by including audio signals from the two
microphones on the right and left side of the head of the sleeping
subject. The microphone with the larger breathing amplitude
indicates the orientation of the head.
[0031] According to an embodiment of the invention, acoustical
information is retrieved via at least two microphones positioned on
both sides of the bedding. To detect the left/right position by
means of the microphones, the following approach is used. After
performance of a noise-reduction of each of the two microphones
(one on the left side, one on the right side) by commonly known
techniques, the breathing-events can be detected. This detection is
done as shown in the following Algorithm 1, where input samples
x[k] are processed with k as the sample-index.
TABLE-US-00001 Algorithm 1 Event detection Initialize k.sub.nonzero
= 0 for k = 1, do if |x[k]| > then .DELTA.k = k - k.sub.nonzero
if .DELTA.k > .DELTA.k.sub.low and .DELTA.k <
.DELTA.k.sub.high then event detection at sample index k end if
k.sub.nonzero = k end if end for indicates data missing or
illegible when filed
[0032] The threshold .DELTA.klow and .DELTA.khigh are adjusted as
the minimum and maximum amount of samples that can occur between
two breathing events. For example, one can adjust these two
parameters as Fs and 6 Fs, with Fs being the sample-rate of the
signal x[k]. The sample frequency may vary in a range of between 10
kHz and 100 kHz, preferably between 22 kHz and 96 kHz. Most
preferred Fs=22050 Hz.
[0033] According to another embodiment of the invention, the
orientation of the light source for the pattern projection as well
as of the sensor/camera for the determination of the reflection is
considered when detecting the body posture. Heuristics are derived
for the main orientations of the camera/sensor and the light source
with regard to the bedding (e.g., on top, from the bottom side of
the bed, from the left side of bed, or from the right side of bed).
Automatically, the corresponding heuristics are applied when the
user inputs the estimated location of the camera/sensor and the
light source with regard to the bed in a one-time installation of a
system capable to perform the inventive method.
[0034] According to another embodiment of the invention, movement
information which is available due to simultaneous actigraphy
processing are used to render a more robust detection due to
indications of position changes and relocation of grid segments on
the subject's body.
[0035] In another aspect, the invention relates to an apparatus for
the detection of postures of a body on a bedding, the apparatus
comprising: [0036] A projector for the projection of a pattern of
electromagnetic waves on said bedding; [0037] A detector for the
detection of the reflection of the pattern projected by said
projector; [0038] A data processing means connected to the
detector, said data processing means being capable to compare
actual reflection detected by the detector with stored reflection
patterns representing typical body postures.
[0039] According to a preferred embodiment of the invention with
respect to the apparatus, the apparatus comprises at least one
microphone connected to a data processing means. Even more
preferred, the apparatus comprises at least two microphones,
located on each side of the bedding.
[0040] In a preferred embodiment, the projector comprises a light
emitting diode (LED) as an electromagnetic wave source, preferably
a LED-laser emitting in the IR-range of the electromagnetic
spectrum. In another preferred embodiment of the invention, the
electromagnetic wave source is capable to emit in an intermitted
and/or intensity modulated way.
[0041] According to another embodiment of the invention, the data
processing means is connected to actuators capable to stimulate a
subject to change his or her body posture. The actuators may be
integrated in e.g. a pillow, a blanket, a t-shirt etc. In another
embodiment, the actuator may be capable to amend the bedding, e.g.
by lifting portions of the bedding.
[0042] In another embodiment, the data processing means is
connected to an environment controlling means, e.g., an air
condition controller, a heating installation controller, a
room-light controller or the like.
[0043] In particular, the invention also relates to a system that
measures Obtrusive Sleep Apnea (OSA) events, e.g., by measuring
breathing by means of a camera or a microphone, a system that
measures sleep quality or sleep depth, an output unit for
outputting information regarding the determined sleep positions
over the night, e.g., how long has the subject slept on the back or
on the side.
[0044] In another aspect, the invention further relates to the use
of a method and/or device as described above for the detection of
physical health conditions related to the body posture during
sleep, or for controlling the environmental situation in or around
a bedding in dependence of the body posture. For example, the
method and/or apparatus can be used for baby-pose detection to
reduce SIDS, i.e., detection whether the baby is on the back or
belly or side. Further, it can be used as a bed sores alarm system,
i.e. detection of how long a person has been in the same position,
and sounding an alarm when it is time to change the body position
to reduce or prevent bed sores, or as a coaching system that uses
the body position itself or the amount of body position shifting
for sleep quality evaluation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] These and other aspects of the invention will be apparent
from and elucidated with reference to the embodiments described
hereinafter.
[0046] In the drawings:
[0047] FIG. 1 shows the most common body postures for sleep
(Dunkell, Samuel, "Sleep Positions," 1977);
[0048] FIG. 2 shows the pattern reflection caused by different body
postures at different resolution;
[0049] FIG. 3 shows a schematic illustration of the body posture
detection according to an embodiment of the invention;
[0050] FIG. 4 shows the intensity distribution comparison of the
reflection between different body postures with a light projector
mounted on a wall at the lower end of the bedding;
[0051] FIG. 5 shows the intensity distribution comparison of the
reflection between different body postures with a light projector
mounted on the ceiling above the head of a subject on the
bedding;
[0052] FIG. 6 shows the intensity distribution comparison of the
reflection between different body postures with a light projector
mounted on the left lower side of the bedding;
[0053] FIG. 7 shows the breathing amplitude comparison when lying
on the back versus lying on the belly;
[0054] FIG. 8 shows cumulative audio events over a full-night
recording of a subject;
[0055] FIG. 9 shows a left/right posture estimation over a full
night;
[0056] FIG. 10 shows integrated actuators usable in combination
with the inventive method;
[0057] FIG. 11 shows a bed lifting device usable in combination
with the inventive method.
DETAILED DESCRIPTION OF EMBODIMENTS
[0058] While the invention has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive; the invention is not limited to the disclosed
embodiments. Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the
disclosure, and the appended claims. In the claims, the word
"comprising" does not exclude other elements or steps, and the
indefinite article "a" or "an" does not exclude a plurality. The
mere fact that certain measures are recited in mutually different
dependent claims does not indicate that a combination of these
measures cannot be used to advantage. Any reference signs in the
claims should not be construed as limiting the scope.
[0059] FIG. 1 shows the most common body postures for sleep. Shown
are the Prone, the Semi-Fetal, the Full Fetal, the Flamingo, the
Sandwich, the Royal, the Cyclops, and the Water-Wings body posture.
The Prone posture is lying face down with the arms extended over
the head and the legs stretched out with the feet somewhat apart.
The Semi-Fetal position is lying on the side with the knees drawn
partway up. The Full Fetal position is lying in a folded position
that obscures the face. The legs are flexed at the knees and the
knees are drawn up. The Flamingo position is lying on the side with
one leg straight out while the other leg is bent at the knee and
flexed at a sharp angle. The Sandwich position is lying on the side
with the legs placed precisely on top on one another, the thigh,
knee and angle of the leg parallel to that of the other. The Royal
posture is lying flat on the back. The Cyclops posture is lying
flat on the back with one hand covering the eyes. In the
Water-Wings posture the head rests in the palms of the hands with
the elbows extended on either side.
[0060] FIG. 2 shows a pattern reflection caused by different body
postures at different resolution. In row 1 and 2 body postures are
shown where the higher intensities of reflection in the middle
segments are visible. These are the postures when the subject lies
on the side. In row 3 images of a high and low resolution are
compared. The low resolution image is sufficient for discriminating
side from flat lying postures. Another possibility is to analyze
the reflected light segments indicating the orientation of the legs
as shown in FIG. 2. From the leg orientation, the head orientation
can be directly obtained.
[0061] FIG. 3 shows an illustration of the body posture detection
according to an embodiment of the invention. In a video signal
captured from a camera the distribution of the reflected light is
detected. For discriminating similar reflection pattern of flat and
side postures, the audio signal coming from two microphones on
either side of the bedding are taken in consideration. Further, for
discriminating a back from a belly posture the breathing amplitude
is taken into consideration. By analyzing the distribution of the
light reflectance, the flat or side body position can be
identified. When a side body position is detected, the orientation
of the face can be either determined by an additional audio signal
and/or by the reflected intensity distribution in the lower leg
area. Adding another modality renders the system more robust. When
only information on the flat or side position is needed, the images
can be captured with a low resolution optical sensor, e.g. an
optical mouse sensor, e.g. with a resolution of 19.times.19. Due to
the reduced information needed by the algorithm, the higher
resolution image from a camera is not needed. This is especially
relevant to preserve the privacy of the sleeping person (see third
row in FIG. 2). When the flat body position is detected, the
breathing amplitude provides an indication on whether the subject
is on the belly or on the back since the chest movement is more
prominent when the sleeping subject is on his/her back. Heuristics
can be derived for the main orientations of the camera/sensor and
the light source(s) with regard to the bed (e.g., on the top, from
the bottom side of the bed, from the left side of the bed, and/or
from the right side of the bed). Automatically, the corresponding
heuristics can be applied when the user inputs the estimated
location of the camera/sensor and light source(s) with regard to
the bed in a one-time installation.
[0062] FIGS. 4 to 6 show the intensity distribution comparison of
the reflection between different body postures for light projector
positions. In the Figs. the reflection is segmented into six areas,
top left/right, middle left/right, and bottom left/right, however,
the reflection can be segmented into as low as two segments. For
some postures, a smaller number of segments is sufficient to
determine body posture. It can also be envisioned to segment the
reflection into a larger number than six segments. Additionally,
the grids do not need to be rectangular in order to determine a
subject's body posture while sleeping. In FIGS. 4 to 6 each posture
gives a specific distribution of reflection between these six
segments. The distribution varies with the position of the light
projector and/or the sensor/camera detecting the reflection. The
following heuristics are derived for three light source locations
in the bedroom (the light source is always positioned higher than
the bed). As a dividing line, the "threshold" is chosen as the mean
of the whole intensity curve within one segment. This could also
have been done differently; it serves only as an approximate
indication so that high-low intensities can be distinguished. The
x-axis coding reflects flat royal (on back, FR), flat prone (on
belly, FP), side right (SR), side left (SL). In total, 71 body
positions with 4 different test subjects were measured. A
classification accuracy of 96% correct detections and 4% false
detections is achieved.
[0063] Bottom (foot part, see FIG. 4): [0064] At least 1 middle
segment high: Side [0065] Both middle segments low: Flat [0066] 1
middle segment low, 1 middle segment close to thresh: If 1 bottom
segment high: Side, else Flat
[0067] Top (on ceiling above upper body, see FIG. 5: [0068] At
least 1 middle segment low: Side [0069] Both middle segments high:
Flat [0070] 1 middle segment close to thresh: If at least 1 top
segment high: Side, else Flat Bottom left, see FIG. 6: [0071] At
least 1 top segment high: Side [0072] Both top segments low: Flat
[0073] 1 top segment low, 1 top segment close to thresh: If 1
middle segment high: Side, else Flat
[0074] FIG. 7 shows the breathing amplitude comparison when lying
on the back versus lying on the belly. When a flat body position is
detected on the basis of the reflected pattern, to distinguish "on
the back" from "on the belly," the respiration analysis output can
be included. The breathing characteristics extracted from a video
signal are different when the person lies on the belly compared to
when the person lies on the back. When the person lies on the back
the chest is free to move into open space without any large barrier
blocking its movement. However, when the person is on the belly,
the chest movement goes into the mattress and the amplitude
perceived by the video is reduced. Empirically, a 25% higher
breathing amplitude is measured when a subject is on his back. The
decline in the breathing amplitude towards the end of the `back`
sequence is assumed due to the more relaxed state of the subject
with more shallow breathing (reduced air flow and chest
expansion).
[0075] FIG. 8 shows cumulative audio events over a full-night
recording of a subject. In this plot, one can see that for each
microphone there are around 5000 event detections. Clearly, it can
be seen that between 400 and 500 minutes, the posture is mainly
toward the left microphone. In order to more clearly detect if the
breathing person lies toward the left or the right microphone, one
will look at the number of detected events in an epoch of 1 minute.
First, a quality measure can be computed as follows:
# events ( mic left ) - # event ( mic_right ) 25 ##EQU00001##
[0076] The division by 25 is chosen as one may assume that roughly
25 breaths are maximally possible during 1 minute. This measure is
depicted for a full-night recording in FIG. 9. A low-pass filtering
of this measure was performed to smooth the data. Finally, the
low-pass filtered signal is compared with the mean level in order
to detect the posture. As one can see, the posture between 400 and
500 minutes is mainly pointed toward the left microphone, 1
represents a left side posture, -1 represents a right side
posture.
Example 1: Alleviation of Obtrusive Sleep Apnea (OSA)
[0077] In this embodiment, it is proposed a positional sleep apnea
apparatus for monitoring the sleep position of a person, in an
unobtrusive manner, comprising: [0078] hardware: a camera that
makes use of reflected light, and a microphone; [0079]
software/algorithms: for detecting the sleep position (lateral or
supine), based on the images of the camera and the microphone
output. Said algorithms can also include the amount of time the
person is on the back or side, and the changes over the night,
etc.
[0080] If OSA events are detected, the output unit can also relate
these events (and the number of occurrences of the event) to the
sleep positions during the night. For example:
[0081] Number of OSA events in supine position: 20
[0082] Number of OSA events in lateral position: 1.
[0083] This can be depicted visually in a graph or using text or
other modality. If sleep quality or sleep depth is determined, the
output unit can also relate the sleep quality or depth to the OSA
events and to the body position during sleep. For example, in the
lateral position, the subject's sleep quality was 30% higher than
in supine position due to less OSA events. This can also be
depicted visually in a graph or using text or other modality.
[0084] The device can also comprise one or both of the following:
an actuator to help subjects who sleep on their backs to move to
sleep on their side. This can be done using tactile stimulation by,
e.g., a bed that automatically lifts up or down, vibrations in the
bed, a t-shirt, mattress, or pillow. The system can also behave
smarter by detecting the location of a subject in bed in order to
trigger certain actuators for optimum and effective turning
stimulation as shown in FIG. 10 and FIG. 11. For example, the
subject can be stimulated to change the body posture to one in
which less OSA events occur, like e.g. the lateral body
posture.
* * * * *