U.S. patent application number 12/894151 was filed with the patent office on 2011-04-21 for system and method for visualizing sleep-related information.
Invention is credited to John Leyon Branscum, JR., John George Sotos.
Application Number | 20110090226 12/894151 |
Document ID | / |
Family ID | 36074984 |
Filed Date | 2011-04-21 |
United States Patent
Application |
20110090226 |
Kind Code |
A1 |
Sotos; John George ; et
al. |
April 21, 2011 |
System and Method for Visualizing Sleep-Related Information
Abstract
A method for improved visualization of information related to
the physiology of a sleeping patient is disclosed. Physiological
information from the patient is obtained by a device, converted to
digital format, and transformed into physiological data of two or
more types. Physiological data of two or more types are combined
into a compact graphical display representing data from all
physiological data types.
Inventors: |
Sotos; John George; (Palo
Alto, CA) ; Branscum, JR.; John Leyon; (Belmont,
CA) |
Family ID: |
36074984 |
Appl. No.: |
12/894151 |
Filed: |
September 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11095154 |
Mar 31, 2005 |
7841987 |
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12894151 |
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Current U.S.
Class: |
345/440 |
Current CPC
Class: |
A61B 5/7445 20130101;
A61B 7/003 20130101; A61B 5/4809 20130101; A61B 5/24 20210101; A61B
5/4812 20130101; A61B 5/743 20130101; A61B 5/08 20130101 |
Class at
Publication: |
345/440 |
International
Class: |
G06T 11/20 20060101
G06T011/20 |
Claims
1. A method for displaying sleep related physiological information,
the method comprising: outputting an image of a spatial region
having a first axis representing time and a second axis
intersecting the first axis, the second axis representing at least
an intensity measurement; and outputting within the spatial region
provided by the first axis and the second axis an envelope trace of
sound associated with sleep, the envelope trace of sound including
a plurality of graphical components within the envelope trace; each
of the plurality of graphical components being associated with a
determined time provided on the first axis representing time;
whereupon at least one of the plurality of graphical components
represents a degree of snoring during the determined time
associated with the graphical component.
2. The method of claim 1 wherein the graphical components are areas
of substantially uniform color or texture pattern having borders
substantially perpendicular to the first axis.
3. The method of claim 1 wherein the graphical components have an
upper border substantially conforming to the envelope trace.
4. The method of claim 3 wherein the graphical components have a
lower border substantially conforming to a baseline of the envelope
trace.
5. The method of claim 1 wherein the graphical components have a
lower border substantially conforming to a baseline of the envelope
trace.
6. The method of claim 1 wherein each of a plurality of graphical
components has an associated visible color, a characteristic of the
visible color being indicative of a degree of snoring.
7. The method of claim 6 wherein at least three visually
distinguishable colors are present in the spatial region, each of
the visually distinguishable colors being associated with at least
a graphical component in the spatial region.
8. The method of claim 1 wherein a plurality of the graphical
components have an associated determined time of duration less than
or equal to one-half second.
9. A method for displaying physiological information associated
with a sleep period of a mammal, the method comprising: outputting
an image of a spatial region having a first axis representing a
time interval associated with the sleep period, and a second axis
intersecting the first axis, the second axis representing at least
an intensity measurement; outputting within the spatial region
provided by the first axis and the second axis an envelope trace of
respiratory sound associated with the mammal during the time
interval; and outputting within the spatial region provided by the
first axis and the second axis a first plurality of graphical
components, each of the first plurality of graphical components
being associated with a determined time period provided on the
first axis representing time, whereupon: at least one of the first
plurality of graphical components represents a degree of snoring
during the determined time associated with the graphical component,
the representation of snoring deriving from a color or texture
pattern of the graphical component; and each of the first plurality
of graphical components has a top border that substantially
conforms to the envelope trace and side borders that are
substantially perpendicular to the first axis or substantially
conform to the envelope trace.
10. The method of claim 9 wherein a greater degree of color
saturation or a greater degree of color darkness of a graphical
component is indicative of a greater degree of snoring by the
mammal during the determined time associated with the graphical
component.
11. The method of claim 9 wherein the duration of the determined
time period of a graphical component is less than or equal to the
duration of an inhalation by the mammal.
12. The method of claim 9 wherein the duration of the determined
time period of a graphical component is less than or equal to one
second.
13. The method of claim 9 further comprising outputting within the
spatial region provided by the first axis and the second axis a
second plurality of graphical components, each of the second
plurality of graphical components being associated with a
determined time period provided on the first axis representing
time, whereupon: at least one of the second plurality of graphical
components represents a limb movement by the mammal during the
determined time associated with the graphical component; and each
of the second plurality of graphical components has a substantially
rectangular shape, with side borders substantially perpendicular to
the first axis, top border substantially at the maximum extent of
the second axis, and bottom border substantially at the minimum
extent of the second axis.
14. The method of claim 13 further comprising outputting within the
spatial region provided by the first axis and second axis a third
plurality of graphical components, each of the third plurality of
graphical components being associated with a determined time period
on the first axis representing time, whereupon: at least one of the
third plurality of graphical components represents a body position
of the mammal during the determined time associated with the
graphical component; and each of the third plurality of graphical
components has substantially linear sub-components parallel to the
first axis and positioned substantially between the maximum extent
of the second axis and the minimum extent of the second axis.
15. The method of claim 14 further comprising outputting within the
spatial region provided by the first axis and second axis a fourth
plurality of graphical components, each of the fourth plurality of
graphical components being associated with a determined time period
on the first axis representing time, whereupon: at least one of the
fourth plurality of graphical components represents respiratory
airflow of the mammal during the determined time associated with
the graphical component; and each of the fourth plurality of
graphical components has a top border that is substantially
parallel to the first axis at substantially the maximum extent of
the second axis, has side borders that are substantially
perpendicular to the first axis, and has a bottom border that
substantially conforms to the envelope trace or is substantially at
the minimum extent of the second axis.
16. A method for displaying sleep related physiological information
about a mammal, the method comprising: outputting an image of a
spatial region having a first axis representing time and a second
axis intersecting the first axis, the second axis representing at
least an intensity measurement; outputting within the spatial
region provided by the first axis and the second axis an envelope
trace of sound associated with sleep; and outputting within the
spatial region provided by the first axis and the second axis a
first plurality of graphical components, each of the first
plurality of graphical components being associated with a
determined time period provided on the first axis representing
time, whereupon: the extent, in a direction parallel to the second
axis, of the first plurality of graphical components substantially
overlaps the extent in said direction of the envelope trace; each
of the first plurality of graphical components is indicative of a
first physiological parameter of the mammal during the determined
time associated with each of the first plurality of graphical
components; and the first physiological parameter is selected from
at least one selected from snoring, blood oxygen saturation, and
body position.
17. The method of claim 16, wherein the first physiological
parameter is snoring.
18. The method of claim 16 wherein the first physiological
parameter is blood oxygen saturation.
19. The method of claim 16, further comprising outputting within
the spatial region provided by the first axis and the second axis a
second plurality of graphical components, each of the second
plurality of graphical components being associated with a
determined time period provided on the first axis representing
time, whereupon: the extent, in a direction parallel to the second
axis, of the second plurality of graphical components substantially
overlaps the extent in said direction of the envelope trace; each
of the second plurality of graphical components is indicative of a
second physiological parameter of the mammal during the determined
time associated with each of the second plurality of graphical
components; and the second physiological parameter is selected from
at least one selected from snoring, blood oxygen saturation, body
position, limb movement, respiratory effort, respiratory air
flow.
20. The method of claim 19 wherein the first physiological
parameter is snoring and the second physiological parameter is
blood oxygen saturation.
21. The method of claim 16 wherein the overlap is greater than 75
percent.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/095,154 filed Mar. 30, 2005 (as petitioned).
[0002] This application claims priority to U.S. Provisional Patent
No. 60/557,735 filed Mar. 30, 2004, hereby incorporated by
reference for all purposes.
[0003] This application claims priority to U.S. Provisional Patent
No. 60/610,888 filed Sep. 18, 2004, hereby incorporated by
reference for all purposes.
BACKGROUND OF THE INVENTION
[0004] The present invention generally relates to ways of
characterizing health related disorders. More particularly, the
invention provides a system and method for visualizing information
related to the sleep of an organism such as a mammal or human
being. But it would be recognized that the invention has a much
broader range of applicability such as applicability in situations
where body position is a consideration.
[0005] Several disorders of sleep are known, including but not
limited to snoring, insomnia, restless legs syndrome, upper airway
resistance syndrome (UARS), and sleep apnea and its subtypes:
obstructive sleep apnea (OSA) and central sleep apnea (CSA). To
characterize disorders afflicting patients during sleep, diagnostic
tests known as "sleep studies" may be performed. During a typical
sleep study, physiological data are collected from the patient by
various physiological sensors during a night's sleep. A type of
sleep study called polysomnography (PSG) normally collects
physiological data from a plurality of data channels over several
hours. Belcher (Sleeping: On the Job! 2002, page 138) describes 16
to 18 different data channels for a typical PSG study. The
resulting data set may be large. Lipman (Snoring from A to Zzzz.
1998, page 115) reports that a paper record of a PSG study may
require one-half mile of paper. Computers and digital data storage
have, in many cases, reduced the need for paper in sleep studies,
but the quantity of information resulting from a sleep study may
still tax the patience of a busy health care professional who wants
to rapidly assess the clinical implications of the data.
[0006] Efficiently presenting a large data set to a busy health
professional can be challenging. Much of the data collected during
a sleep study are quantitative. Presenting quantitative data
graphically has often proven advantageous. Tufte (The Display of
Quantitative Information. 1983, page 9) notes: "Modern data
graphics can do much more than simply substitute for small
statistical tables. At their best, graphics are instruments for
reasoning about quantitative information. Often the most effective
way to describe, explore, and summarize a set of numbers--even a
very large set--is to look at pictures of those numbers.
Furthermore, of all methods for analyzing and communicating
statistical information, well-designed data graphics are usually
the simplest and at the same time the most powerful."
[0007] Well-designed data graphics are, of course, generally
advantageous, and Tufte has spent considerable effort teaching the
principles of good data graphical design. He believes (Tufte.
Supra. Page 13) graphical displays should, among other desiderata:
[0008] show the data; [0009] avoid distorting what the data have to
say; [0010] present many numbers in a small place; [0011] make
large data sets coherent; [0012] encourage the eye to compare
different pieces of data; [0013] reveal the data at several levels
of detail, from a broad overview to the fine.
[0014] Data from sleep studies have been displayed in a plurality
of graphical formats, often satisfying Tufte's desiderata only
partially.
[0015] FIG. 1A shows a segment of raw PSG data rendered graphically
(from Undevia et al. Internet document, 2004). At least 17 channels
of physiological data are presented, graphed in separate panes on a
common horizontal (time) axis, with each pane having its own
vertical axis. The top 8 panes represent electroencephalographic
channels, with successive panes representing the left oculogram
(the "LOC" pane of the graph, as labeled at the left margin), the
right oculogram (ROC), chin electromyography (EMG chin), left and
right leg electromyography (LAT/RAT), nasal airflow (Airflow),
thoracic respiratory movement (Chest), abdominal respiratory
movement (Abdomen), electrocardiogram (ECG), and arterial oxygen
saturation (SAO2). Tufte advocates graphical designs that
"encourage the eye to compare different pieces of data," but the
relatively large vertical distance between some channel plots in
this figure generally makes inter-channel comparisons less
inviting. Approximately 5 minutes of data are presented in FIG. 1A.
Because a PSG study may collect data for 8 hours or longer, on the
order of 100 such pages may be required to fully present a single
study.
[0016] FIG. 1B shows approximately 6 hours 43 minutes of four data
channels from a PSG study, plotted in four separate panes (from
Undevia et al. Supra). From top to bottom the panes plot sleep
stage, oxygen saturation, apnea-hypopnea event types, and delivered
facemask pressure against time. Some of these data inherently vary
slowly, allowing longer periods of time to be plotted in a given
space without losing resolution. Plotting certain types of data,
e.g. electrocardiogram signals, at the time scale of FIG. 1B would
typically be far less informative because such data signals
inherently vary faster. Although FIG. 1B needs only one page to
plot results from the entire time of a sleep study, it appears to
have a lower information density than FIG. 1A. Thus, FIG. 1B may
have a potential for application of Tufte's desideratum to "present
many numbers in a small place." Another shortcoming of FIG. 1B is,
as in FIG. 1A, the relatively large vertical distance between
channel panes, making inter-channel comparisons generally less
inviting.
[0017] In addition to polysomnography, other types of sleep studies
may be performed. For example, several types of "reduced sensor"
diagnostic devices collect fewer channels of physiological data
than typical polysomnography. A certain tension often exists in
designing a reduced sensor device between maximizing diagnostic
yield and minimizing technical failures. In many cases diagnostic
yield increases with the number of sensors used to collect
physiological data from a patient being tested with the device.
However, in many cases the likelihood of a technical failure during
a study also increases with the number of sensors used. Thus, the
choice of which sensors to design into a reduced sensor device is
often critical. As Douglas (Sleep Med Rev. 2003; 7:53-59) remarks:
"The choice of sensors to be used is open to considerable
debate."
[0018] The American Academy of Sleep Medicine provides some
guidance about sensor selection. A committee writing on their
behalf states "Body position must be documented during recordings
to assess the presence of OSA" (Thorpy et al. Sleep. 1994;
17:372-377). There is evidence that the severity of OSA in some
people varies according to their body position during sleep. In
such persons, OSA is typically more severe when the person is lying
on their back, as opposed to lying on a side or face down.
[0019] If positional data are collected during a sleep study, it is
often desirable to visualize these data. FIG. 2 shows a plot 200 of
a patient's body position during a night of sleep, as recorded by a
reduced sensor device. Time, in minutes, is on the horizontal axis
210, and body position is on the vertical axis 220. Four body
positions are recognized by this reduced sensor device,
corresponding to being face up, face down, facing left, or facing
right, as shown in labeling of vertical axis 220. The plot shows,
for example, that initially the patient was facing right for a
little more than an hour, then was on his or her back for about the
next two hours ("facing up"). This simple plot of position-vs-time
may be incorporated into a PSG-style plot by, for example,
replacing one of the 17 panes plotted in FIG. 1A or one of the 4
panes plotted in FIG. 1B with the pane plotted in FIG. 2 (and
adjusting the time axis as necessary, of course). Such a
substitution, however, retains most of the shortcomings present in
FIG. 1A and FIG. 1B.
[0020] Some reduced sensor devices collect sound as a physiological
parameter for use in assessing breathing disorders of sleep, as
taught in U.S. patent Ser. No. 11/094,911. One factor in the
visualization of digitized sound data is the high typical sampling
rate, e.g. 2000 samples per second. Thus, in an 8-hour period, over
57 million sound samples may be collected. Although this may be
considered a large data set in many visualization applications,
there are several examples where signals similar to raw sound are
plotted on a common time axis with other physiological signals.
[0021] In some cases the envelope of an audio signal may be plotted
to give an indication of the loudness of the sound. (Note: we treat
sound level, sound intensity, and sound loudness as the same
concept herein.) However, the sampling rate of an envelope of an
audio signal is often significantly lower than the sampling rate of
the signal on which it was based. Thus, the envelope may be plotted
similarly to some of the channels in FIG. 1A and FIG. 1B, but with
some of the same shortcomings discussed for those figures.
[0022] Potsic (Laryngoscope. 1987; 97:1430-1437) (Otolaryngol Head
Neck Surg. 1986; 94:476-480) teaches a method for representing
several minutes of sound data collected by a reduced sensor device.
His approach directly represents a quantity related to sound
intensity and, indirectly, respiratory regularity. Furthermore, the
example plots he provides do not include data from a channel other
than sound, which is likely to be a shortcoming of his approach
should comparison of sound and other channels be desired.
[0023] Other approaches to visualization of sound provide a binary
representation of whether sound level (or intensity) have exceeded
a certain threshold (Stoohs and Guilleminault. Eur Respir J. 1990;
3:823-829) (Penzel et al. Sleep. 1990; 13:175-182) (U.S. Patient
Nos. 4,982,738; 5,275,159; and 6,120,441). While potentially
compact, this degree of data reduction may be associated with an
undesirable loss of information in some applications.
[0024] From the above, it is desirable to have improved techniques
for characterizing health related disorders.
BRIEF SUMMARY OF THE INVENTION
[0025] A method for improved visualization of information related
to the physiology of a sleeping patient is disclosed. Physiological
information from the patient is obtained by a device, converted to
digital format, and transformed into physiological data of two or
more types. Physiological data of two or more types are combined
into a compact graphical display representing data from all
physiological data types.
[0026] In one embodiment sound information comprises a first data
type. An envelope of the sound information is displayed against a
time axis. Physiological data of a second type is displayed against
the same time axis such that variations in the values of the data
elements are represented as visually distinguishable variations in
the region above the envelope line, e.g. variations in hue,
saturation, color, texture, and the like. Physiological data of a
third type may be displayed against the same time axis such that
variations in the values of the data elements are represented as
visually distinguishable variations in the region below the
envelope line. Physiological data of a fourth type may be displayed
against the same time axis such that variations in the values of
the data elements are represented as visually distinguishable
variations straddling the envelope line. Additional physiological
data may be plotted against the time axis.
[0027] Various additional objects, features, and advantages of the
present invention can be more fully appreciated with reference to
the detailed description and accompanying drawings that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawing(s) will be provided by the Office
upon request and payment of the necessary fee.
[0029] FIGS. 1A and 1B illustrate a visualization of
polysomnographic information.
[0030] FIG. 2 illustrates a visualization of body position
information.
[0031] FIG. 3 shows a flowchart of the operation of one embodiment
of a system for communicating physiological information.
[0032] FIG. 4A shows an embodiment of a plot of five physiological
parameters.
[0033] FIG. 4A2 shows substantially the same information as FIG.
4A, but with a greater range in the scale of the vertical axis.
[0034] FIG. 4A3 shows an enlarged view of the lower left corner of
FIG. 4A.
[0035] FIG. 4B shows a flowchart of the operation to produce FIG.
4A.
[0036] FIG. 5 shows an embodiment of a plot of position and three
additional parameters.
[0037] FIG. 6A shows an embodiment of a positional histogram.
[0038] FIG. 6B shows an embodiment of a positional histogram teamed
with a table.
DESCRIPTION OF THE SPECIFIC EMBODIMENT
[0039] FIG. 3 shows a flow diagram of steps in communicating
physiological information about a human or otherwise mammalian
patient. In one method, in data collection step 310 a device may
acquire physiological data from a patient who is sleeping (or
attempting to sleep). The device may be a polysomnographic device
or a reduced sensor device, e.g. as taught in U.S. patent
application Ser. No. 11/094,911. In step 320 the data collected in
step 310 may be converted to digital format, e.g. with an
analog-to-digital converter.
[0040] In one method, optional step 330 may result in one or more
processing transformations being applied to the digitized data
provided from step 320. For example, audio data may be filtered,
unusable portions of data may be identified and tagged, artifacts
in the data may be removed, diagnoses may be made, and algorithmic
transformations may be applied to the data. An example of an
algorithmic transformation is computation of an envelope of an
audio signal. Merely by way of example, processing step 330 may
occur in a digital computer.
[0041] Information about the data collected in step 310 or about
the data created in step 330 may be represented in one or more
forms. In one method, words may be generated in step 340, e.g. "The
mean heart rate during the study was 79 beats per minute." In
another method, sounds may be created in step 350, e.g. playing
back tracheal sounds recorded from the patient between 2:06 a.m.
and 2:07 a.m. In yet another method, one or more static images may
be generated in step 360. Used in this sense, "static" means
"unchanging." In one method, an animation or moving picture may be
created in step 370, generated, for example, from a plurality of
static images.
[0042] In one embodiment, one or more of steps 340, 350, 360, and
370 may be combined. For example, sound from step 350 may be
combined with an animation from step 370. As an additional example,
words from step 340 may be used to caption an image resulting from
step 360. As another example, a static image (from step 360)
representing one minute of an envelope signal may be combined with
an animation of a vertical bar taking one minute to sweep across
the static image (from step 370), and these may be combined with
the sound of the patient's breathing (from step 350) synchronized
to the position of the bar with respect to the static envelope
image. In this example, words (from step 340) may appear and
disappear, e.g. the word "apnea" may appear when the bar begins to
sweep across a period of time associated with an apnea.
[0043] In one method, the information from one or more of steps
340, 350, 360, and 370 is received by a decision-maker, who uses
all or some of the information to make a decision about the
diagnosis and/or management of the patient.
[0044] We have discovered that certain types of static images, as
may result from step 360, may facilitate decision making in step
380.
[0045] FIG. 4A illustrates an embodiment in which values of five
different physiological parameters are represented graphically in
one graphical pane 400. FIGS. 4A2 and 4A3 provide alternate views
into FIG. 4A. (FIG. 4A3 is an enlargement of the lower left corner
of FIG. 4A, while FIG. 4A3 replots substantially the same data as
FIG. 4A but with an enlarged scale on the vertical axis). In FIG.
4A the parameters derived from data collected (as in step 310)
during one minute of a sleep study of a patient. In one embodiment
the data may have been collected from a plurality of sensors
including, but not limited to, a tracheal microphone, an
accelerometer coupled to the patient's wrist, and a body-position
sensor. In graphical pane 400, the five parameters are plotted
against a common time axis 402, as follows: [0046] 1. A jagged dark
blue line 404, sometimes known as an "envelope trace," may
represent the envelope of sound recorded during the one minute of
time indicated by horizontal axis 402 for this study. In FIG. 4A
sound level increases from bottom to top on the vertical axis 403.
Breaths, in one embodiment, are normally identifiable in envelope
trace 404 as a mountain-like rise and fall. (Some breaths appear as
double mountains because inhalation and exhalation appear as
separate peaks.) In FIG. 4A and in FIG. 4A2, for example, there are
6 complete breaths represented to the right of the peak indicated
by the item 404 pointer. The loudness of the first five breaths in
FIG. 4A have been capped at 200 units, and at 2400 units in FIG.
4A2. [0047] 2. The temporal extent of a solidly light-blue-colored
"movement" rectangle 406 extending the full height of pane 400 may
represent a period of time during which the patient moved his or
her wrist; [0048] 3. The temporal extent of a solidly
yellow-colored "apnea" area 408 above envelope trace 404 may
represent a period of time during which little or no sound
intensity above a baseline was present in the sound envelope. In
one embodiment the lower border of an apnea area 408 is generally a
portion of the envelope trace 404. [0049] 4. The temporal extent of
a solidly red-colored "snoring" area 410 below envelope trace 404
may represent a period of time during which the patient snored. In
one embodiment the upper border of a snoring area 410 is generally
a portion of the envelope trace 404. FIGS. 4A2 and 4A3 also
illustrate this embodiment. FIGS. 4A, 4A2, and 4A3 show four clear
snoring breaths from 87.1 minutes to 87.3 minutes. [0050] 5. One or
more horizontal lines 412a, 412b, 412c near the top of pane 400 may
represent the position of the patient's body (with respect to
earth's gravity) at various times during the minute represented by
horizontal axis 402.
[0051] (Note: We frequently use the numbers for areas 406, 408, and
410 to refer to the generic class of each of these area types.)
[0052] In one embodiment, apnea area 408 may be considered to
represent a period in which little air flowed in the patient's
trachea. Because airflow in a trachea generally produces sound
detectable by a suitable tracheal microphone, the absence (or
near-absence) of a signal from such a microphone is often an
indication of the absence (or near-absence) of tracheal airflow.
FIG. 4A displays several short periods of apnea, e.g. between
end-exhalation and start-inhalation from minutes 87.7 to 88. We
call such periods "micro-apneas" because of their short duration
(e.g. one second or less) as compared to the common requirement of
10 seconds of apnea in the diagnosis of obstructive sleep
apnea.
[0053] For convenience we refer to this visualization of Position,
Snoring, Apnea, Loudness (envelope), and Movement as the PSALM
graph. However, because other embodiments may plot different
parameters, use of the PSALM acronym should not be interpreted as
limiting.
[0054] In one embodiment, the colors of movement area 406, apnea
area 408, and snoring area 410 may all be different, such that they
may be readily distinguished. In another embodiment, areas 406,
408, and 410 may have the same color, but have different texture
patterns, e.g. cross-hatching, dots, and the like, to distinguish
them.
[0055] In one embodiment the representation of a wrist movement by
a movement rectangle 406 may remove from view representations of a
low sound level (apnea area 408) or snoring (area 410) occurring
during the same time period as the wrist movement. The phrases
"movement trumps snoring" and "movement trumps apnea" may be used
to describe these interactions. These interactions are often
acceptable, because if a patient is moving it is generally true he
or she is awake during the period of movement, and thus there is
relatively less concern about whether the patient is then snoring
or making little sound. Generally, the envelope trace 404 will be
visible as a line appearing to lie above (in the z-axis) the
solidly colored movement rectangle 406.
[0056] In one embodiment, sound epochs may be rated according to
their degree of resemblance to a snoring definition, a measure we
call "snoringness." In an embodiment snoringness may be graphically
represented by varying the saturation or other characteristic of
the color of snoring area 410. For example, a deep red color may
indicate a sound that is typical for a snore, while a light red
color may indicate that a sound is atypical, but not entirely
unlike, a snore. In such an embodiment lack of snoringness may be
represented without a color. In another embodiment, varying snoring
loudness may be represented by varying the color of snoring area
410, but this is not often preferred, as the vertical extent of
envelope trace 404 also represents sound loudness.
[0057] In another embodiment the horizontal lines 412 representing
body position may do so according to a code. For example, the
presence of three lines (412a, 412b, 412c) at a specific time may
indicate the patient, while lying in bed, was facing upwards at
that time. The presence of one line (412a) may indicate the patient
is facing down, and the presence of two lines may indicate the
patient is on his or her side (412a and 412c for facing left, and
412b and 412c for facing right). Applying this code to FIG. 4A
discloses that the patient was on his or her back for approximately
the first 0.44 minutes, before assuming a left-facing position.
[0058] In another embodiment body position may be represented by
icons arrayed in a horizontal line near the top of pane 400, such
that an icon plotted at a time t (per horizontal axis 402) would
represent the patient's body position in bed at that time t. In one
embodiment the icons are arrowheads facing up, down, left, and
right with respect to pane 400, representing, respectively, the
patient facing up, down, left, and right.
[0059] The technique of representing body position in a vertically
small extent, as shown, for example, in FIG. 4A, may potentially be
applied to any graph in which the representation of body position
is desired. In one embodiment a body position datum may assume
relatively few values, e.g. up, down, left, right, facilitating the
use of coding approaches, as above. Sleep/wake stage is another
physiological variable that in some embodiments can assume
relatively few values, e.g. wakefulness, rapid eye movement (REM)
sleep, and stages one, two, three, and four sleep. As a result of
this similarity between body position and sleep/wake stage, in one
embodiment sleep/wake stage may be amenable to one or more of the
visualization techniques applied to body position.
[0060] In another embodiment one or more additional parameters may
be plotted on pane 400 as one or more traces extending from left to
right, preferably distinguishable from each other by color,
thickness, dashing, and the like. Oxygen saturation, for example,
could be plotted as a series of line segments, with numerical
labeling on the right vertical axis 414 to assist in discerning the
numeric values indicated by the oximetry trace. In such an
embodiment it may be preferable to omit horizontal lines 412a
through 412c, as the plot may become too crowded in appearance. In
another embodiment, a representation of body position may be
displayed in a small vertical extent just above the top border of
pane 400. In general, however, different plotting elements and
physiological parameters may be included or not included in various
embodiments according to the type of decisions a graph is meant to
support.
[0061] A representation of data such as that illustrated in FIG. 4A
may be advantageous in an embodiment because it may reduce five (or
potentially more) channels of data into one graphical pane, thereby
conserving vertical extent, keeping related data together and, in
the words of Tufte (supra.), encouraging "the eye to compare
different pieces of data." We have discovered, for example, that
plotting 8 lines of 2 minutes each on standard copier paper with an
inkjet printer will, in many cases, retain sufficient resolution
for most uses. We have also discovered that printing two pages on
one side of one sheet of standard copier paper also retains
adequate resolution in many cases. Thus, one embodiment may print
32 minutes of data on each side of a piece of paper, meaning that
only about 8 pieces of paper would be required to fully visualize
the PSALM data obtained in an 8-hour sleep study.
[0062] In some embodiments it is preferable to use a pale color for
apnea area 408 because the breathing of some persons includes a
high percentage of micro-apneas, leading to an almost solidly
colored plot that can wash out certain other plotted elements. In
another embodiment the color saturation or other characteristic of
apnea area 408 may depend on the proportion of nearby time that is
apneic, with the saturation increasing as the amount of local apnea
increases.
[0063] A representation of data such as that illustrated in FIG. 4A
may be advantageous in an embodiment because of certain patterns
that might be produced by the representation. For example,
rhythmically regular snoring may be very apparent when looking at a
PSALM plot displaying several minutes of envelope traces 404 and
corresponding snoring areas 410. This phenomenon may be
advantageous given that Smolley and Bruce (The Snoring Cure. 1999,
page 167) remark: "Snoring that is regular--without interruptions
[of various types]--is not likely to represent a serious problem."
Similarly, in some cases irregular snoring is easy to discern by
inspecting a PSALM plot.
[0064] In one embodiment choosing an emotionally-laden color for
snoring area 410 may be advantageous because some people attach an
emotion to snoring problems and because dense snoring (i.e. snoring
with almost every breath) may result in a PSALM plot rather
suffused with the snoring area 410 color. Thus, red, with its usual
active overtones, may be an appropriate color for an embodiment if
complaints of snoring are provoking discord between two people.
[0065] In one method, the graph of FIG. 4A may be generated
according to FIG. 4B. Data 452 defining the envelope may be used to
plot the envelope trace 404 (step 450). After such a plot, the axes
of the plot may have a defined extent that can be read (step 460).
Using the data 472 defining apnea periods (whether micro- or
macro-), the apnea area 408 may be plotted (step 470). Some
graphical software routines may facilitate this step by using
envelope data 452 and the top boundary of the vertical plot axis to
define a polygon that can be plotted and filled with a color as a
single function call. Similarly, the data 482 defining periods of
snoring may be used to plot snore areas 410 (step 480). The data
492 defining limb movement may then be used to plot move areas 406
(step 490) and the position data (494) may be used to plot the
horizontal position lines 412 (step 495). In some cases, envelope
trace 404 will need to be replotted (not shown) after one or more
of the other drawing steps have occurred.
[0066] FIG. 5 shows one embodiment of a graphical plot in a single
pane 500 relating body position to three other variables: snoring,
wrist movement, and time. Time may run across a horizontal axis
502. A vertical axis 504 may specify four (or some other number of)
body positions 510. The extent of the vertical axis may be divided
with horizontal lines into four strata, one for each body position.
Certain rectangular portions of some strata may be shaded (e.g.
512a) with a color, signifying that the patient had assumed the
corresponding body position at the time encompassed by the
horizontal extent of the rectangular color shading. Shaded areas
(e.g. 512a) may contain one or more sub-strata 514a and 516a
possibly including event indicators. A first sub-stratum 514 may
display a vertical mark during times associated with an arm
movement of the patient. A second sub-stratum 516 may display a
vertical mark during times associated with a snore. In some
embodiments a third sub-stratum (not shown) may display a vertical
mark during times associated with an oxygen desaturation, based on
data from an oximeter. In another embodiment other parameter(s) may
be displayed in various sub-strata, e.g. apnea and hypopnea events,
respiratory effort related arousals, and the like. In one
embodiment each sub-stratum has its own vertical axis, which may
allow continuous variables to be represented.
[0067] In one embodiment event markers for different subs-strata
are distinguishable, e.g. by color or by texture. In another
embodiment, a color assigned to a class of event marker has
mnemonic value, e.g. red is assigned to a blood-related event such
as oxygen desaturation.
[0068] In one embodiment, graphical contents of pane 500 may be
rendered in the Postscript language (Adobe Corporation, San Jose,
Calif.). A potential advantage of rendering in Postscript is that a
plurality of magnifications can be applied to pane 500, using, for
example, the magnification capabilities provided by Adobe Acrobat
Reader software. A result is that a sub-stratum 516b, which appears
at low magnification to have event markers in a relatively long and
unbroken extent in time may, at high resolution, resolve into
separate and distinguishable snoring events.
[0069] Another potential advantage of the graphical display
technique illustrated in FIG. 5 is that it may have the potential
to convey intuitively a correlation between body position and
events in sub-strata (e.g. 514 and 516). For example, inspection of
sub-stratum 516 across the entire study in FIG. 5 seems to disclose
that snoring is present in all body positions to an approximately
equal degree, as the density of snoring marks appears approximately
the same in all strata 510. Inspection of sub-stratum 514, however,
seems to suggest that arm movement was more common in this study
when the patient was facing up (i.e. on his or her back), as the
density of arm movement event marks appears greater in the time
periods of the "Up" stratum.
[0070] An additional potential advantage of the graphical display
technique illustrated in FIG. 5 is that it may convey the body
positions the patient assumed during the sleep study. Gaps in
shading of the strata 522 may indicate the system was unable to
assign a body position for the corresponding period of time, and as
a result event markers 514b are sometimes plotted outside of a
shaded stratum.
[0071] FIG. 6A shows one embodiment of a "positional histogram"
690. A positional histogram may plot a quantity for each of the
canonical body positions in an embodiment and may further provide
various ways to compare the quantities between positions. FIG. 6A
shows a positional histogram 690 with 4 canonical positions (facing
right, facing left, facing down, and facing up). The general
appearance of the plot may be that of a circle with foreshortened
spokes. When there are 4 canonical positions, each body position
may be allocated one quarter of the circle. Thus, each of the
canonical positions in FIG. 6A is allocated a quadrant. It may be
advantageous to allocate the quadrants (or other sectors) so as to
provide a mnemonic correlation between the figure and the actual
orientation of the positions. Thus, in FIG. 6A, for example, the
quadrant allocated to the "facing up" position is at the top of the
figure.
[0072] We will temporarily focus our discussion of FIG. 6A on the
"facing right" quadrant. Each position's sector may include, but is
not limited to, a caption 610, a quantity label 620, a histogram
bar 640, and a comparison circle 630. Caption 610 may generally be
a word or two that explains which position is displayed. Quantity
label 620 may generally be a number corresponding to the value of
the graph's parameter for the given position. Histogram bar 640 may
be akin to the bars on a standard histogram, but with a different
orientation, i.e. oriented in the same direction as the quadrant of
the corresponding body position. Comparison circle 630 may be
defined by two points: the center of FIG. 6A and the tip of a
histogram bar 640. All histogram bars meet in the center of FIG.
6A. Comparison circle 630 reinforces the distance from the center
of FIG. 6A to the top of histogram bar 640 for a given section.
Comparison circle 630 may be used to make quick graphical "greater
than" and "less than" comparisons between positions, as the circle
extends into all quadrants, allowing a rapid comparison with the
histogram bars in other quadrants.
[0073] In one embodiment a positional histogram plot 690 may be
paired with a table 680 reporting positional data, as in FIG. 6B.
Table 680 and positional histogram 690, for example, both may
report the number of snoring breaths, and the proportion of snoring
breaths, occurring in each of the canonical body positions. This
may be advantageous in the case of persons who are weak readers and
are more visually oriented.
[0074] It is seen that certain visualization techniques may improve
the quality of information display, according to some of the
criteria enunciated by Tufte. Although the application of such
techniques herein has been related to sleep physiology, the
techniques are not limited to sleep physiology.
[0075] It should be noted that the above sequence of steps is
merely illustrative. The steps can be performed using computer
software or hardware or a combination of hardware and software. Any
of the above steps can also be separated or be combined, depending
upon the embodiment. In some cases, the steps can also be changed
in order without limiting the scope of the invention claimed
herein. One of ordinary skill in the art would recognize many other
variations, modifications, and alternatives. It is also understood
that the examples and embodiments described herein are for
illustrative purposes only and that various modifications or
changes in light thereof will be suggested to persons skilled in
the art and are to be included within the spirit and purview of
this application and scope of the appended claims.
* * * * *