U.S. patent application number 15/088220 was filed with the patent office on 2017-02-02 for method and system for monitoring oxygenation levels of a compartment for detecting conditions of a compartment syndrome.
The applicant listed for this patent is J&M SHULER, INC.. Invention is credited to MICHAEL SIMMS SHULER.
Application Number | 20170027499 15/088220 |
Document ID | / |
Family ID | 39716701 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170027499 |
Kind Code |
A1 |
SHULER; MICHAEL SIMMS |
February 2, 2017 |
METHOD AND SYSTEM FOR MONITORING OXYGENATION LEVELS OF A
COMPARTMENT FOR DETECTING CONDITIONS OF A COMPARTMENT SYNDROME
Abstract
A method and system for continually monitoring oxygenation
levels in real-time in compartments of an animal limb, such as in a
human leg or a human thigh or a forearm, can be used to assist in
the diagnosis of a compartment syndrome. The method and system can
include one or more near infrared compartment sensors in which each
sensor can be provided with a compartment alignment mechanism and a
central scan depth marker so that each sensor may be precisely
positioned over a compartment of a living organism. The method and
system can include a device for displaying oxygenation levels
corresponding to respective compartment sensors that are measuring
oxygenation levels of a compartment of interest. The method and
system can also monitor the relationship between blood pressure and
oxygenation levels and activate alarms based on predetermined
conditions relating to the oxygenation levels or blood pressure or
both.
Inventors: |
SHULER; MICHAEL SIMMS;
(Athens, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
J&M SHULER, INC. |
ATHENS |
GA |
US |
|
|
Family ID: |
39716701 |
Appl. No.: |
15/088220 |
Filed: |
April 1, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14106739 |
Dec 14, 2013 |
9320473 |
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15088220 |
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13279298 |
Oct 23, 2011 |
8694068 |
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14106739 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/14507 20130101;
A61B 5/6828 20130101; A61B 5/684 20130101; A61B 2562/04 20130101;
A61B 5/7405 20130101; A61B 5/7282 20130101; A61B 5/021 20130101;
A61B 5/746 20130101; A61B 5/443 20130101; A61B 5/742 20130101; A61B
5/14551 20130101; A61B 5/0215 20130101; A61B 5/0205 20130101; A61B
5/4519 20130101; A61B 5/03 20130101; A61B 5/14557 20130101; A61B
5/1455 20130101; A61B 5/14552 20130101; A61B 5/14542 20130101; A61B
5/7246 20130101; A61B 5/7271 20130101; A61B 5/7275 20130101; A61B
5/6824 20130101; A61B 5/022 20130101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61B 5/145 20060101 A61B005/145; A61B 5/0205 20060101
A61B005/0205; A61B 5/1455 20060101 A61B005/1455 |
Claims
1-4. (canceled)
5. A computer-implemented method for automatically monitoring
oxygenation levels of injured tissue of a human body for
automatically detecting conditions of a compartment syndrome,
comprising: automatically monitoring oxygenation levels of injured
tissue in a continuous manner with a first non-invasive sensor;
automatically monitoring oxygenation levels of healthy tissue in a
continuous manner with a second non-invasive sensor, the second
non-invasive sensor detecting systemic perfusion of the human body
from the healthy tissue; and automatically activating an alarm with
a computing device when oxygenation levels of the first
non-invasive sensor for the injured tissue start decreasing in
value compared to the oxygenation levels of the second non-invasive
sensor for the healthy tissue, the second non-invasive sensor
providing a basis for comparison for relative oxygenation levels of
the injured tissue.
6. The method of claim 5, further comprising: automatically
monitoring blood pressure of the human body in a continuous manner
with a non-invasive blood pressure device, the blood pressure
comprising diastolic and systolic blood pressure values.
7. The method of claim 6, further comprising: automatically
activating an alarm with the computing device when both the blood
pressure of the human body comprising the diastolic and systolic
blood pressure values decreases and oxygenation levels of the first
non-invasive sensor for the injured tissue decreases.
8. The method of claim 5, further comprising displaying oxygenation
levels of the compartment on a display device.
9. The method of claim 5, further comprising providing an alignment
mechanism on the first non-invasive sensor.
10. The method of claim 6, further comprising calculating with the
computing device a running average for the blood pressure and
oxygenation levels.
11. The method of claim 5, wherein activating an alarm with the
computing device further comprises activating an alarm that
produces one or more alerts on a display device.
12. The method of claim 6, further comprising calculating with the
computing device a mean arterial pressure (MAP) and displaying the
mean arterial pressure (MAP) on a display device.
13. A system for automatically monitoring oxygenation levels of
injured tissue of a human body for automatically detecting
conditions of a compartment syndrome, the system comprising: a
plurality of non-invasive sensors for automatically detecting
oxygenation levels of the human body in a continuous manner; and a
computing device coupled to the non-invasive sensors, wherein the
computing device is configured for: monitoring oxygenation levels
of injured tissue from a first non-invasive sensor of the plurality
of non-invasive sensors; monitoring oxygenation levels of healthy
tissue from a second non-invasive sensor of the plurality of
non-invasive sensors; and automatically activating an alarm when
oxygenation levels of the first non-invasive sensor start
decreasing in value compared to the oxygenation levels of the
second non-invasive sensor, the second non-invasive sensor
providing a basis for comparison for relative oxygenation levels of
injured tissue.
14. The system of claim 13, further comprising: a non-invasive
blood pressure device for automatically sensing blood pressure of
the human body in a continuous manner, the blood pressure
comprising diastolic and systolic blood pressure values.
15. The system of claim 14, wherein the computing device monitors
blood pressure of the human body with the non-invasive blood
pressure device.
16. The system of claim 15, further comprising automatically
activating an alarm with the computing device when both the blood
pressure comprising the diastolic and systolic blood pressure
values of the human body decreases and oxygenation levels of the
first non-invasive sensor start decrease in value.
17. The system of claim 13, wherein the computing device is further
configured for increasing a frequency at which the oxygenation
levels are monitored when the oxygenation level fall within a
predetermined range of values.
18. The system of claim 13, further comprising a display device
configured for displaying the oxygenation levels of the human
body.
19. The system of claim 13, wherein one or more of the first
non-invasive sensor and the second non-invasive sensor each
comprises an array of non-invasive sensing elements.
20. The system of claim 19, wherein the computing device is further
configured for controlling a timing for activating respective
non-invasive sensors of the array in order to provide scans of
different portions of the human body.
21. The system of claim 13, wherein the computing device is further
configured for calculating a running average for the oxygenation
levels.
22. The system of claim 13, wherein the alarm comprises at least
one of an audible alarm and visual alarm.
23. The system of claim 14, wherein the computing device is further
configured for calculating a mean arterial pressure (MAP) that is
displayed on the display device.
24. The system of claim 14, wherein the computing device is further
configured for activating an alarm when the blood pressure and
oxygenation levels approach predefined levels.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to provisional
patent application entitled, "Near Infrared Compartment Syndrome
(NICS) Monitor," filed on Feb. 27, 2007 and assigned U.S.
Application Ser. No. 60/903,632. The entire contents of the
provisional patent application mentioned above is hereby
incorporated by reference.
FIELD OF INVENTION
[0002] The invention relates to a coordinated, continual and
real-time method and system for monitoring oxygenation levels of a
compartment in order to detect conditions that are likely caused by
a compartment syndrome. More particularly, the invention relates to
an orchestrated method and system that monitors oxygenation levels
and that is provided with sensors having markers so that the
sensors can be precisely positioned over a compartment of interest
in order to assist with a compartment syndrome diagnosis.
BACKGROUND OF THE INVENTION
[0003] Compartment syndrome is a medical condition where the
pressure inside a compartment, which is a muscle group surrounded
by fascia or a thin, inelastic film, increases until the blood
circulation inside the volume defined by the fascia or thin film is
cut off. The most common site, in humans, occurs in the lower leg,
and more specifically, in regions adjacent to the tibia and fibula.
There are four compartments in the lower, human leg: the anterior
(front), lateral (side next to the fibula) and the deep and
superficial posterior (back).
[0004] These four compartments surround the tibia and fibula.
Anyone of these four compartments can yield a compartment syndrome
when bleeding or swelling occurs within the compartment.
Compartment syndrome usually occurs after some trauma or injury to
the tissues, such as muscles or bones or vessel (or all three),
contained within the compartment. Bleeding or swelling within a
compartment can cause an increase in pressure within that
compartment. The fascia does not expand, so as pressure rises, the
tissue and vessels begin to be compressed within the
compartment.
[0005] This compression of tissue, such as muscle, due to
intra-compartmental pressure can restrict and often times stop
blood flow from entering the compartment that is destined for any
tissues contained within the compartment. This condition is termed
ischemia. Without blood flow to tissues, such as muscle, the
tissues will eventually die. This condition is termed necrosis.
[0006] A simple working definition for a compartment syndrome is an
increased pressure within a closed space which reduces the
capillary blood perfusion below a level necessary for tissue
viability. As noted above, this situation may be produced by two
conditions. The first condition can include an increase in volume
within a closed space, and the second condition is a decrease in
size of the space.
[0007] An increase in volume occurs in a clinical setting of
hemorrhage, post ischemic swelling, re-perfusion, and
arterial-venous fistula. A decrease in size results from a cast
that is too tight, constrictive dressings, pneumatic anti-shock
garments, and closure of fascial defects. As the pressure increases
in tissue, it exceeds the low intramuscular arteriolar pressure
causing decreased blood in the capillary anastomosis and subsequent
shunting of blood flow from the compartment.
[0008] The clinical conditions that may be associated with
compartment syndrome include the management of fractures, soft
tissue injuries, arterial injuries, drug overdoses, limb
compression situations, burns, post-ischemic swelling, constrictive
dressings, aggressive fluid resuscitation and tight casts.
[0009] Referring now to the Figures, FIG. 1 illustrates an X-ray
view of a human leg 100 with fractured bones of the tibia 105 and
fibula 110 that lead to one or more compartment syndromes in the
muscles 115 surrounding the bones of the human leg 100. The tibia
105 and fibula 110 usually bleed in regions proximate to the
physical break regions 120. This bleeding can form a large pool of
stagnant blood referred to as a hematoma. The hematoma can start
pressing upon muscles 115 that may be proximate to the break 120.
This pressure caused by the hematoma can severely restrict or stop
blood flow into the muscles 115 of a compartment, which is the
diagnosis of a compartment syndrome.
Traditional Methods for Diagnosing Compartment Syndromes
[0010] Referring now to FIG. 2, this Figure is a side view of a
human leg 100 in which compartment pressures are being measured
with a large bore needle 200, having a gauge size such as 14 or 16
(which is the largest needle in the hospital available to
clinicians), according to a conventional method known in the prior
art. While compartment pressures can be measured with this
conventional method, the method is highly invasive procedure which
can cause tremendous pain to the patient. Needles with large gauge
sizes of 14 or 16 are analogous to sticking a patient with an
object as large as a nail or a pen.
[0011] In addition to causing tremendous pain to the patient, there
are several more problems associated with the conventional needle
measuring method. First, it is very challenging for a medical
practitioner to actually measure or read pressure of a compartment
since the needle must be positioned at least within the interior of
a compartment. To enter the interior of a compartment, the needle
200 must penetrate through several layers of skin and muscle. And
it is very difficult for the medical practitioner to know if the
needle has penetrated adequately through the intermediate layers to
enter into the compartment. This challenge significantly increases
if the patient being measured is obese and has significant amounts
of subcutaneous fat in which to penetrate with the needle.
[0012] Often, the medical practitioner may not have a needle
accurately positioned inside a compartment which can yield a
reading of the tissue adjacent to the compartment, such as muscle
or skin. Such a reading of muscle or skin instead of the
compartment of interest can provide the medical practitioner with
elevated or depressed pressure readings that do not reflect the
actual pressure contained within the compartment of interest.
Pressure readings inside a compartment have been shown to vary
(increase) based on the depth of the reading as well as the
proximity to the fracture site.
[0013] Because of the challenge medical practitioners face with
precisely positioning a needle within a compartment of interest and
because of the numerous law suits associated with the diagnosis of
compartment syndrome, many medical schools do not provide any
formal training for medical practitioners to learn how to properly
place a needle within a compartment of interest for reading a
compartment's pressure. Therefore, many medical practitioners are
not equipped with the skills or experience to accurately measure
compartment pressures with the needle measuring method.
[0014] Currently, intra-compartmental pressures are the only
objective diagnostic tool. Due to the legal climate regarding this
condition, clinicians are forced to treat an elevated value for
compartment pressures or expose themselves to legal ramifications
with any complications. As described later, the treatment of
compartment syndrome can cause significant morbidity and increase
the risk for infection. Therefore inaccurate and elevated pressure
readings are a very difficult and potential dangerous pitfall.
[0015] Another problem associated with the training and experience
required for the needle measuring method is that, as noted above,
compartment syndromes usually occur when tissues within the
compartment are experiencing unusual levels of swelling and
pressure. With this swelling and pressure, the tissues do not have
their normal size. Therefore, any training of a medical
practitioner must be made with a patient suffering under these
conditions. A normal patient without any swelling would not provide
a medical practitioner with the skills to accurately assess a size
of a compartment when using the needle measuring method for
determining compartment pressure. Put another way, due to the
trauma associated with the injury, normal anatomy is not always
present when attempting to measure compartment pressures.
[0016] In addition to the problem of entering a compartment that
may have an abnormal size or anatomy, the needle measuring method
has the problem of providing only a snap-shot of data at an instant
of time. When the conventional needle measuring method is used, it
provides the medical practitioner with pressure data for a single
instant of time. In other words, the needle pressure method only
provides the medical practitioner with one data point for a
particular time. Once pressure is read by the medical practitioner,
he or she usually removes the needle from the patient. The data
obtained from a single measurement in time gives no information
concerning the pressure trend, and the direction the
intra-compartmental pressure is moving.
[0017] This collection of single data points over long periods of
time is usually not very helpful because pressures within a
compartment as well as the patient's blood pressure can change
abruptly, on the order of minutes. Also, because of the pain
associated with the needle measuring method noted above, the
medical practitioner will seldom or rarely take pressure readings
within a few minutes of each other using a needle.
[0018] A further problem of the needle measuring method is that for
certain regions of the body, such as the lower leg, there are four
compartments to measure. This means that a patient's leg must be
stuck with the large bore needle at least four times in order for a
medical practitioner to rule out that a compartment syndrome exists
for the lower leg. In the lower leg of the human body, one
compartment is located under a neighboring compartment such that a
needle measurement may be needed in at least two locations that are
very close together, but in which the medical practitioner must
penetrate tissues at a shallow depth at a first location to reach
the first compartment; and for reaching the second compartment that
is underneath the first compartment, a large depth must be
penetrated by the needle, often with the needle piercing the first
compartment and then the second compartment.
[0019] Another problem, besides pain that is associated with the
needle pressure measuring method, is that there is a lack of
consensus among medical practitioners over the compartment pressure
ranges which are believed to indicate that a compartment syndrome
may exist for a particular patient. Normal compartment pressure in
the human body usually approaches 4 mmHg in the recumbent position.
Meanwhile, scientists have found that an absolute pressure
measurement of 30 mmHg in a compartment may indicate presence of
compartment syndrome. However, there are other scientists who
believe that patients with intracompartmental pressures of 45 mmHg
or greater should be identified as having true compartment
syndromes. But other studies have shown patients with
intra-compartmental pressures above these limits with no clinical
signs of compartment syndrome. Additional studies have shown that a
pressure gradient based on perfusion pressure (diastolic blood
pressure minus intra-compartmental pressure) is the more important
variable. Studies have shown in a laboratory setting that once the
perfusion pressure drops to 10 mm Hg tissue necrosis starts to
occur.
[0020] Other subjective methods for diagnosing compartment
syndromes instead of the needle measuring method exist, however,
they may have less accuracy than the needle measuring method
because they rely on clinical symptoms of a patient. Some clinical
symptoms of a patient used to help diagnose compartment syndromes
include pulselessness (absence of a pulse), lack of muscle power,
pain, parastesias, and if the flesh is cold to touch. Pain out of
proportion and with passive stretch are considered the earliest and
most sensitive, but both have very low specificity. One of the
major drawbacks of these symptoms is that for many of them the
patient must be conscious and must be able to respond to the
medical practitioner. This is true for the muscle power and pain
assessment. For any inebriated patients or patients who are
unconscious, the pain assessment and muscle power assessment cannot
be used accurately by the medical practitioner. In the setting of
high energy trauma which is associated with compartment syndrome,
many patients are not capable of cooperating with a good physical
exam due to any number of causes including head trauma, medical
treatment (including intubation), drug or alcohol ingestion,
neurovascular compromise or critical and life threatening injuries
to other body systems.
[0021] For the pain assessment, if a lower leg compartment syndrome
exists in a patient, then the range of motion for a patient's foot
or toes will be extremely limited and very painful when the
patient's foot or toes are actively or passively moved. The pain
from a compartment syndrome can be very immense because the muscles
are deprived of oxygen because of the compartment syndrome.
[0022] Another drawback using pain to assess the likelihood of a
compartment syndrome is that every human has a different threshold
for pain. This means that even if someone should be experiencing a
high level of pain, he or she may have a high threshold for pain
and therefore, not provide the medical practitioner with a normal
reaction for the current level of pain. Another problem with using
pain to assess the likelihood of the existence of a compartment
syndrome is that if the patient is experiencing trauma to other
parts of their body, he or she may not feel the pain of a
compartment syndrome as significantly, especially if the trauma to
the other parts of the patient's body is more severe. This
condition is termed a distracting injury. On the other hand, trauma
causes the initial injury that precipitates a compartment syndrome.
That initial trauma by definition will cause a baseline amount of
pain that is often very difficult to separate from a potential
compartment syndrome pain. These initial injuries by themselves
cause significant pain, so a patient that does not tolerate pain
well may present similar to a compartment syndrome without having
any increased pressures simply because they react vehemently to
painful conditions.
Conventional Non-Invasive Techniques for Measuring Oxygenation
Levels of a Compartment
[0023] Non-invasive measuring of compartment syndromes using near
infrared sensors, such as spectrophotometric sensors, to measure
oxygenation levels within a compartment has been suggested by the
conventional art. However, these conventional techniques have
encountered the problem of a medical practitioner locating
compartments of interest and accurately and precisely positioning a
sensor over a compartment of interest. Often the orientation of the
scan and the depth of the scan produced by a near infrared sensor
as well as the orientation of a compartment can be challenging for
a medical practitioner to determine because conventional sensors
are not marked with any instructions or visual aids. Another
problem faced by the medical practitioner with conventional
non-invasive techniques is determining how to assess the
oxygenation level of compartments that lie underneath a particular
neighboring compartment, such as with the deep posterior
compartment of the human leg.
[0024] In trauma settings, near infrared sensors often do not work
when they are placed over regions of the body that have hematomas
or pools of blood. In such conditions, a medical practitioner
usually guesses at what regions of the human body do not contain
any hematomas that could block compartment measurements. Also,
conventional near infrared sensors typically are not sterilized and
cannot be used in surgical or operating environments.
[0025] Near infrared sensors (NIRS) in their current form are
limited to a single sensor with a single sensor depth. They also
can be affected by skin pigmentation that is not accounted for in
the current technology. Placement of the sensor can be difficult
since an expanding hematoma can block a previously acceptable
placement. Additionally, the only system as of this writing is a
single monitor system. There is no product available at this time
which will allow for multiple areas to be monitored in close
proximity to one another without the potential for interference
from other sensor light sources.
Treatment for Compartment Syndrome
[0026] Referring now to FIG. 3, this figure is a side view of a
human leg 100 in which a surgical procedure, known as a fasciotomy,
was performed in order to release the pressures in one or more
compartments surrounding the bones of the leg according to a
technique known in the art in order to alleviate a compartment
syndrome that was diagnosed. This surgical procedure includes an
incision 300 that is made along the length of the leg 100 and is
generally as long as the compartments contained within the leg 100.
While a single incision 300 is illustrated in FIG. 3, a second
incision is made on the opposing side of the leg so that a patient
will have two incisions on each side of his leg 100. These
incisions typically extend from near the knee to near the ankle on
each side of the leg.
[0027] This procedure is very invasive and it often leaves the
patient with severe scars and venous congestion once healed. Also
the procedure increases a patient's chances of receiving an
air-borne infection because the incisions made on either side of
the leg are usually left open for several days in order to allow
for the swelling and excess bleeding to subside. Fasciotomies
transform a closed fracture (one in which the skin is intact and
minimal risk of infection) to an open fracture. Open fractures have
a much higher risk of bone infections which requires multiple
surgical debridements and ultimately amputation in some cases in
order to appropriately treat. Additionally, some wound cannot be
closed and require skin transfers, or skin grafts, from other parts
of the body, usually from the anterior thigh.
[0028] Therefore, it is quite apparent that accurately diagnosing
compartment syndrome is critical because any misdiagnosis can lead
to significant morbidity. A missed compartment syndrome can result
in an insensate and contracted leg and foot. A fasciotomy which is
highly invasive procedure and which exposes a patient to many
additional health risks should not be performed in the absence of a
compartment syndrome.
[0029] Additionally, time is an important factor in the evaluation
of these patients. Ischemic muscle begins to undergo irreversible
changes after about six hours of decreased perfusion. Once
irreversible changes or necrosis occur, a fasciotomy should not be
performed. Fasciotomies in the setting of dead muscle only increase
the risk for severe infections and other complications. Late
fasciotomies have been shown to have approximately a 50-75% risk of
complication. Therefore, fasciotomies need to be performed early
but judiciously in patients that are often unresponsive or
uncooperative in order to prevent severe morbidity.
[0030] Accordingly, there is a need in the art for a non-invasive,
real time method and system that monitors oxygenation levels of a
compartment and that is provided with sensors which can be
precisely positioned over a compartment of interest in order to
assist in assessing conditions associated with a compartment
syndrome. A further need exists in the art for a non-invasive
method that monitors oxygenation levels of a compartment over long
periods of time at frequent time intervals and that can monitor
different compartments that may be in close proximity with one
another. Another need exists in the art for oxygenation sensors
that can be fabricated to fit the size of compartments of interest.
There is also a need in the art for a non-invasive method and
system that monitors oxygenation levels and that can identify ideal
locations along a human body in which to conduct scans for deep
compartments. There is another need in the art for sterile,
non-invasive oxygenation sensors that can be used under surgical
and operating conditions. There is a need for multiple locations
and multiple compartments to be monitored in a continual and
orchestrated manner by a single system. In other words, multiple
monitors coordinated to limit noise and continually monitor
multiple compartments are needed in the art.
SUMMARY OF THE INVENTION
[0031] A method and system for monitoring oxygenation levels in
compartments of an animal limb, such as in a human leg or a human
thigh or a forearm, can be used to assist in the diagnosis of a
compartment syndrome. The method and system can include one or more
near infrared compartment sensors in which each sensor can be
provided with a compartment alignment mechanism and a central scan
depth marker so that each sensor may be precisely positioned over a
compartment of a living organism, such as a compartment of a human
leg or human thigh or forearm. The method and system can include a
device for displaying oxygenation levels corresponding to
respective compartment sensors that are measuring oxygenation
levels of a compartment of interest.
[0032] The alignment mechanism of a compartment sensor can include
a linear marking on a surface of the compartment sensor that is
opposite to the side which produces a light scan used to detect
oxygenation levels. The linear marking can be used by a medical
practitioner to align a compartment sensor with the longitudinal
axis of a compartment.
[0033] The central scan depth marker can include a linear marking
positioned on a surface of a compartment sensor that intersects the
alignment mechanism, a crosshatch, at a location along the
alignment mechanism that denotes the deepest region of a light scan
produced by the compartment sensor. The depth of measurement can be
displayed in numeric form over the crosshatch guide to aid the
clinician since depth varies based on light source & receptor
separation. The central scan depth marker can insure that a medical
practitioner properly aligns the compartment sensor at a location
that will measure a compartment of interest.
[0034] According to one exemplary embodiment of the invention, in
addition to each compartment sensor having a compartment alignment
mechanism and a central scan depth marker, the compartment sensors
can be grouped in pairs and share a common supporting substrate.
The common supporting substrate can include a separation device,
such as, but not limited to, a perforated region. The separation
device, such as a perforated region, can be torn or broken by the
user in order to adjust for a size of a compartment of interest. In
other words, with the separation device, a pair of two compartment
sensors can be physically divided so that the sensors do not share
a common substrate after the separation device is utilized.
[0035] According to another exemplary embodiment of the invention,
a compartment sensor can include one light emitting device and two
different sets of light detectors such that the compartment sensor
can provide a first, shallow oxygenation scan at a first depth and
a second, deep oxygenation scan at a second depth. The second depth
can be greater than the first depth, so that a general computing
device coupled to the two compartment sensors can be programmed or
hardwired to calculate the second, deep oxygenation level at the
second depth by subtracting data generated by the first, shallow
oxygenation level at the first depth.
[0036] According to another alternate exemplary embodiment of the
invention, several individual compartment scanners can be grouped
together along a longitudinal axis of a common supporting material
to define a linear compartment array. The linear compartment array
can also include a linear marking on its surface that is opposite
to the side which produces the light scan as well as multiple
crosshatches for depth denotation. The linear marking can be used
to align the linear compartment array with a longitudinal axis of a
compartment.
[0037] According to another exemplary embodiment of the invention,
a compartment sensor or compartment sensor array can be positioned
at a predetermined position along a human leg in order to measure a
deep posterior compartment of the human leg. Position is
posteromedial to the posterior aspect of the tibia.
[0038] According to one exemplary embodiment of the invention, a
linear compartment sensor array can include individual sensors that
scan at different depths such that the linear compartment sensor
array as a whole has a varied scan depth along its longitudinal
axis to more closely match the topography, shape, or depth of a
compartment of interest that has a corresponding varied depth.
According to another exemplary embodiment of the invention, each
individual compartment sensor can produce its oxygenation scan at a
predetermined interval such that each individual compartment sensor
is only activated one at a time or in a predetermined sequence so
that any two or more sensors are not working at a same instant of
time in order to reduce any potential for light interference among
the different oxygenation scans produced by respective sensors of
the array.
[0039] According to a further exemplary embodiment of the
invention, each compartment sensor can use optical filters in
combination with different wavelengths of light so that two or more
compartment sensors can scan at the same without interfering with
one another. According to another exemplary embodiment of the
invention, a linear compartment array can include optical
transmitters that are shared among pairs of optical receivers. For
example, a single optical transmitter can be used with two optical
receivers that are disposed at angles of one-hundred eighty degrees
relative to each other and the optical transmitter along the axis
of the compartment.
[0040] According to yet another exemplary embodiment, a compartment
sensor or compartment sensor array can be made from materials that
can be sterilized and used in operating environments that are free
from germs or bacteria. A compartment sensor or compartment sensor
array can also be provided with a coating that is sterilazable or
sterilized. When a compartment sensor or compartment sensor array
is sterilized, it can be provided underneath bandages or dressings
adjacent to a wound or injury of a compartment or proximate to
compartment of interest. Each sensor can be provided with a common
and sufficient length of cord, such as on the order of
approximately ten feet, to allow the cord to extend off the sterile
operative field.
[0041] According to another exemplary embodiment of the invention,
the compartment monitoring method and system can include a device
that displays oxygenations levels of a compartment over time in
which oxygenation levels are measured at a particular time
frequency, such as, but not limited to, on the order of seconds or
minutes. According to another exemplary embodiment of the
invention, the compartment monitoring system and method can display
all measured data from all sensors on the same screen. The display
can also show a differential between injured and uninjured leg
values of the concordant compartments.
[0042] For example, the screen can display calculations of the
difference between the values of the anterior compartment of both
the injured leg and the contralateral uninjured leg (control leg)
to help evaluate the perfusion of the injured leg. According to an
alternate exemplary embodiment of the invention, the compartment
monitoring system and method can display anatomical features and
locations for positioning the sensors of the system along
compartments of interest selected by a user. This program at
initial set up can help insure proper placement of the sensor by
the clinician by using diagrams for accurate placement for each of
the labeled sensors or sensor arrays.
[0043] According to another exemplary embodiment of the invention,
the compartment monitoring system can detect changes in a size of a
hematoma when at least one linear compartment array is used to
measure oxygenations levels at different positions of a
compartment. Alternatively, the compartment monitoring system can
provide information on various levels of blood flow along the
longitudinal axis of a compartment when at least one linear
compartment array is used to measure oxygenations levels at
different positions of a compartment.
[0044] Alternatively, according to another exemplary embodiment of
the invention, a compartment sensor can be provided with a skin
pigment sensor that has a known reflectance and that can be used to
calibrate the compartment sensor based on relative reflectance of
skin pigment which can affect data generated from oxygenation
scans. For example, a skin narrow-band simple reflectance device, a
tristimulus colorimetric device, or scanning reflectance
spectrophotometer can be incorporated into the oxygenation sensor
system to obtain a standardized value for skin pigmentation which
evaluate melanin and hemoglobin in the skin.
[0045] Once the skin melanin is determined it can be correlated to
its calculated absorption or reflectance (effect) on the NIRS value
using a predetermined calibration system. This effect, optical
density value, can be incorporated in tissue hemoglobin
concentration calculations in the deep tissue. Accounting for skin
pigmentation will usually allow for information or values to be
compared across different subjects with different skin pigmentation
as well as using the number as an absolute value instead of
monitoring simple changes in value over time.
[0046] According to an exemplary embodiment of the invention, a
compartment sensor can be provided with layers of a known thickness
and a known absorption in order to reduce the depth of an
oxygenation scan by the sensor so that a thin layer of tissue, such
as skin can be measured by the sensor. In other words, due to
limitations of how close the light source and receptor can be
positioned, in order to evaluate very superficial layers such as
skin, the sensor can be separated from the skin of the subject by
fixed amount with a known material. For example, by using a
material with a known optical density, the length of a scan can be
shortened by projecting the light pathway mostly through the known
material.
[0047] The light pathway would escape the known material only at
the maximum depth to evaluate a limited depth of tissue such as
skin. This technique would allow for direct measurement of the skin
pigmentation effects on the system. This skin sensor can be either
incorporated into the compartment monitoring system directly or
used to construct the predetermined calibration for skin
reflectance values that can be used by the compartment monitoring
system.
[0048] According to another exemplary embodiment of the invention,
the compartment monitoring system can receive data from a blood
pressure monitoring system in order to correlate oxygenation levels
with blood pressure. The compartment monitoring system that
includes a blood pressure monitoring system can activate an alarm,
such as an audible or visual alarm (or both), when the diastolic
pressure of a patient drops since it has been discovered that
perfusion can be significantly lowered or stopped at low diastolic
pressures and when compartment pressures are greater than the
diastolic pressure.
[0049] According to another exemplary embodiment, the compartment
monitoring system can increase a frequency of data collection for
oxygenation levels and/or blood pressure readings when low blood
pressure is detected by the system. According to an alternative
exemplary embodiment, the compartment monitoring system can display
blood pressure and oxygenation levels simultaneously and in a
graphical manner over time, such as an X-Y plot in a Cartesian
plane or as two separate graphs over time. Correlation between
hemoglobin concentration and diastolic pressure can be used to
estimate intra-compartmental pressures without having to use
invasive needle measurements.
[0050] According to another further exemplary embodiment, the
inventive system can incorporate oxygenation levels from both lower
extremities and compare values between the legs or other body
parts. Initial data from patients with extremity injuries by the
inventor have shown that muscular skeletal injuries cause hyperemia
(increased blood flow and oxygen) in the injured extremity. If a
compartment syndrome develops, the oxygenation drops from an
elevated state to an equal and then lower level with comparison to
the uninjured limb. Therefore when comparing injured and uninjured
extremities, the injured limb may show increased oxygenation
levels. If levels begin to drop in the injured limb compared to the
uninjured limb, an alarm or alert can be triggered to alert the
clinician. A display for the blood pressure being measured can also
be provided by the system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 illustrates an X-ray view of a human leg with
fractured bones of the tibia and fibula that lead to one or more
compartment syndromes in muscles surrounding the bones of the human
leg.
[0052] FIG. 2 is a side view of a human leg in which compartment
pressures are being measured with a large bore needle according to
a conventional method known in the prior art.
[0053] FIG. 3 is a side view of a human leg in which a surgical
procedure, known as a fasciotomy, was performed in order to release
the pressures in one or more compartments surrounding the bones of
the leg according to a technique known in the art.
[0054] FIG. 4 illustrates oxygen levels of compartments of a human
leg being measured by compartment sensors that include compartment
alignment mechanisms and central scan depth markers according to
one exemplary embodiment of the invention.
[0055] FIG. 5A illustrates a bottom view of two pairs of
compartment sensors with each sensor having a compartment alignment
mechanism and a central scan marker in addition to a separating
device according to one exemplary embodiment of the invention.
[0056] FIG. 5B illustrates a bottom view of the four compartment
sensors of FIG. 5A (?) but with the individual sensors divided from
one another through using the separating device, such as the
perforations, according to one exemplary embodiment of the
invention.
[0057] FIG. 6A illustrates a bottom view of a three sensor
embodiment in which one sensor of the three compartment sensors can
scan at two or more depths according to one exemplary embodiment of
the invention.
[0058] FIG. 6B, this figure illustrates the compartment sensor of
FIG. 6A that can scan at two or more depths in order to measure
deeper compartments of an animal body according to one exemplary
embodiment of the invention.
[0059] FIG. 7 illustrates a near light detector and a far light
detector that are positioned within substrate material at
predetermined distances from the optical transmitter of a
compartment sensor according to one exemplary embodiment of the
invention.
[0060] FIG. 8A illustrates a linear array of compartment sensors
assembled as a single mechanical unit that can provide scans at
various depths according to one exemplary embodiment of the
invention.
[0061] FIG. 8B illustrates a linear compartment sensor array that
can include optical transmitters that are shared among pairs of
optical receivers according to one exemplary embodiment of the
invention.
[0062] FIG. 8C is a functional block diagram of compartment sensor
that illustrates multiple optical receivers that may positioned on
opposite sides of a single optical transmitter and that may be
simultaneously activated to produce their scans at the same time
according to one exemplary embodiment of the invention.
[0063] FIG. 9A illustrates a cross-sectional view of a left-sided
human leg that has the four major compartments which can be
measured by the compartment sensors according to one exemplary
embodiment of the invention.
[0064] FIG. 9B illustrates a cross-sectional view of a right-sided
human leg and possible interference between light rays of
simultaneous oxygenation scans made by the compartment sensors into
respective compartments of interest according to one exemplary
embodiment of the invention.
[0065] FIG. 9C illustrates a position of a compartment sensor in
relation to the knee for the deep posterior compartment of a right
sided human leg according to one exemplary embodiment of the
invention.
[0066] FIG. 10 illustrates an exemplary display of numeric
oxygenation values as well as graphical plots for at least two
compartments of an animal according to one exemplary embodiment of
the invention.
[0067] FIG. 11 illustrates single compartment sensors with
alignment mechanisms and central scan depth markers that can be
used to properly orient each sensor with a longitudinal axis of a
compartment of an animal body according to one exemplary embodiment
of the invention.
[0068] FIG. 12 illustrates compartment sensor arrays with alignment
mechanisms that can be used to properly orient each array with a
longitudinal axis of a compartment of an animal body according to
one exemplary embodiment of the invention.
[0069] FIG. 13A illustrates various locations for single
compartment sensors that can be positioned on a front side of
animal body, such as a human, to measure oxygenation levels of
various compartments according to one exemplary embodiment of the
invention.
[0070] FIG. 13B illustrates various locations for single
compartment sensors that can be positioned on a rear side of animal
body, such as a human, to measure oxygenation levels of various
compartments according to one exemplary embodiment of the
invention.
[0071] FIG. 14A illustrates various locations for compartment
sensor arrays that can be positioned over compartments on a front
side of an animal body, such as a human, to measure oxygenation
levels of the various compartments according to one exemplary
embodiment of the invention.
[0072] FIG. 14B illustrates various locations for compartment
sensor arrays that can be positioned over compartments on a rear
side of an animal body, such as a human, to measure oxygenations
levels of the various compartments according to one exemplary
embodiment of the invention.
[0073] FIG. 14C illustrates an exemplary display and controls for
the display device that lists data for eight single compartment
sensors according to one exemplary embodiment of the invention.
[0074] FIG. 14D illustrates an exemplary display of providing users
with guidance for properly orienting a single compartment sensor
over a compartment of an animal, such as a human leg, according to
one exemplary embodiment of the invention.
[0075] FIG. 15A illustrates a front view of lower limbs, such as
two lower legs of a human body, that are being monitored by four
compartment sensor arrays according to an exemplary embodiment of
the invention.
[0076] FIG. 15B illustrates a display of the display device that
can be used to monitor hematomas and/or blood flow according to one
exemplary embodiment of the invention.
[0077] FIG. 16 illustrates a display of the display device for an
instant of time after the display of FIG. 15B and which can be used
to monitor hematomas and/or blood flow according to one exemplary
embodiment of the invention.
[0078] FIG. 17 illustrates a sensor design for measuring the
optical density of skin according to one exemplary embodiment of
the invention.
[0079] FIG. 18A illustrates a sensor that can penetrate two layers
of skin to obtain optical density values according to one exemplary
embodiment of the invention.
[0080] FIG. 18B illustrates a sensor that can penetrate one layer
of skin according to one exemplary embodiment of the invention.
[0081] FIG. 18C illustrates a modified compartment monitoring
system that can correlate skin pigmentation values with skin
optical density values in order to provide offset values for
oxygenation levels across different subjects who have different
skin pigmentation according to one exemplary embodiment of the
invention.
[0082] FIG. 19 is a functional block diagram of the major
components of a compartment monitoring system that can monitor a
relationship between blood pressure and oxygenation values
according to one exemplary embodiment of the invention.
[0083] FIG. 20 is an exemplary display that can be provided on the
display device and which provides current blood pressure values and
oxygenation levels of a compartment of interest according to one
exemplary embodiment of the invention.
[0084] FIG. 21 is a functional block diagram that illustrates
sterilized material options for a compartment sensor according to
one exemplary embodiment of the invention.
[0085] FIG. 22 illustrates an exemplary clinical environment of a
compartment sensor where the sensor can be positioned within or
between a dressing and the skin of a patient according to one
exemplary embodiment of the invention.
[0086] FIG. 23 is a graph of perfusion pressure plotted against
oxygenation levels of a study conducted to determine the
sensitivity and responsiveness of the inventive compartment
monitoring system according to one exemplary embodiment of the
invention.
[0087] FIG. 24 is a graph of perfusion pressure plotted against a
change in the oxygenation levels from a baseline for each subject
of the study conducted to determine the sensitivity and
responsiveness of the inventive compartment monitoring system
according to one exemplary embodiment of the invention.
[0088] FIG. 25 is a logic flow diagram illustrating an exemplary
method for monitoring oxygenation levels of a compartment for
detecting conditions of a compartment syndrome.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0089] A method and system for monitoring oxygenation levels in
compartments of an animal limb, such as in a human leg or a human
thigh or a forearm, can be used to assist in the diagnosis of a
compartment syndrome. The method and system can include one or more
near infrared compartment sensors in which each sensor can be
provided with a compartment alignment mechanism and a central scan
depth marker so that each sensor may be precisely positioned over a
compartment of a human leg or human thigh or forearm. The method
and system can include a device for displaying oxygenation levels
corresponding to respective compartment sensors that are measuring
oxygenation levels of a compartment of interest.
[0090] Referring now to the drawings, in which like reference
numerals designate like elements, FIG. 4 illustrates oxygen levels
402A, 402B of compartments of a human leg 100 being measured by a
near-infrared spectroscopy (NIRS) sensors 405A, 405B that include a
compartment alignment mechanisms 410A, 410B and central scan depth
markers 415A, 415B according to one exemplary embodiment of the
invention.
[0091] The alignment mechanism 410 of a compartment sensor 405 can
include a linear marking on a surface of the compartment sensor 405
that is opposite to the side which produces a light scan used to
detect oxygenation levels. The linear marking can be used by a
medical practitioner to align a compartment sensor 405 with the
longitudinal axis 450 of a compartment of interest. The invention
is not limited to a solid line on the sensor 405. Other alignment
mechanisms 410 within the scope of the invention include, but are
not limited to, tick marks, dashed lines, notches cut in the
substrate of the compartment sensor 405 to provide a geometric
reference for the medical practitioner, and other like visual
orienting alignment mechanisms 405.
[0092] The central scan depth marker 415 can include a linear
marking positioned on a surface of a compartment sensor 405 that
intersects the alignment mechanism 410 at a location along the
alignment mechanism 410 that denotes the deepest region of a light
scan produced by the compartment sensor 405. The depth of
measurement can be displayed in numeric form over the central scan
depth marker 415 as a guide to aid medical practitioner since scan
depth can vary based on the compartment sensor's light source and
receptor separation. The central scan depth marker 415 can insure
that a medical practitioner properly aligns the compartment sensor
405 at a location that will measure a compartment of interest.
Similar to the alignment mechanism 410 noted above, the invention
is not limited to a solid line on the compartment sensor 405. Other
central scan depth markers 415 within the scope of the invention
include, but are not limited to, tick marks, dashed lines, notches
cut in the substrate of the compartment sensor to provide a
geometric reference for the medical practitioner, and other like
visual orienting central depth markers 415.
[0093] Once the proper position for a compartment sensor 405 is
determined by the medical practitioner with the compartment
alignment mechanism 410 and the central scan depth marker 415, the
medical practitioner can apply the compartment sensor 405 on the
patient by using an adhesive that is already part of the
compartment sensor 405.
[0094] FIG. 4 illustrates three compartment sensors 405A, 405B, and
405C of a system 400 for monitoring three different compartments of
the lower human leg 100. A fourth compartment sensor 405D not
illustrated can be positioned on a side of the leg not illustrated
and which monitors the fourth compartment of the lower human leg
100. The compartment sensors 405 illustrated in FIG. 4 and
discussed throughout this document can be of the type described in
U.S. Pat. No. 6,615,065 issued in the name of Barrett et al. (the
"065 patent"), the entire contents of which are hereby incorporated
by reference. The compartment sensors 405 can include those made
and distributed by Somanetics, Troy, Mich. However, other
conventional near infrared compartment sensors 405 can be used
without departing from the scope and spirit of the invention.
[0095] The compartment sensors 405 can generally provide
spectrophotometric in vivo monitoring of blood metabolites such as
hemoglobin oxygen concentration in any type of compartment and on a
continuing and substantially instantaneous basis.
[0096] The compartment sensors 405 are coupled to a processor and
display unit 420 which displays the two oxygen levels 402A, 402B
comprising the values of seventy-three. The processor and display
unit 420 can display all four oxygen levels of four compartments of
the human leg 100 when at least four compartment sensors 405 are
deployed. The invention is not limited to four compartment sensor
embodiments. The invention can include any number of compartment
sensors for the accurate detection of conditions that may be
associated with compartment syndrome. For example, another
exemplary embodiment illustrated in FIG. 14C allows for eight
sensor readings so that concomitant monitoring of the contralateral
uninjured leg can be performed.
[0097] The processor of the display unit 420 can be a conventional
central processing unit (CPU) known to one of ordinary skill in the
art. It may have other components too, similar to those found in a
general purpose computer, such as, but not limited to, memory like
RAM, ROM, EEPROM, Programming Logic Units (PLUs), firmware, and the
like. Alternatively, the processor and display unit 420 can be a
general purpose computer without departing from the invention.
[0098] The processor and display unit 420 can operate in a
networked computer environment using logical connections to one or
more other remote computers. The computers described herein may be
personal computers, such as hand-held computers, a server, a client
such as web browser, a router, a network PC, a peer device, or a
common network node. The logical connections depicted in the
Figures can include additional local area networks (LANs) and a
wide area networks (WANs) not shown.
[0099] The processor and display unit 420 illustrated in FIG. 4 and
the remaining Figures may be coupled to a LAN through a network
interface or adaptor. When used in a WAN network environment, the
computers may typically include a modem or other means for
establishing direct communication lines over the WAN.
[0100] In a networked environment, program modules may be stored in
remote memory storage devices. It will be appreciated that the
network connections shown are exemplary and other means of
establishing a communications link between computers other than
depicted may be used.
[0101] Moreover, those skilled in the art will appreciate that the
present invention may be implemented in other computer system
configurations, including other hand-held devices besides hand-held
computers, multiprocessor systems, microprocessor based or
programmable consumer electronics, networked personal computers,
minicomputers, mainframe computers, and the like.
[0102] The invention may be practiced in a distributed computing
environment where tasks may be performed by remote processing
devices that are linked through a communications network. In a
distributed computing environment, program modules may be located
in both local and remote storage devices.
[0103] The processor and display unit 420 can comprise any general
purpose computer capable of running software applications and that
is portable for mobile applications or emergency applications.
[0104] The communications between the processor and display unit
420 and the sensors 405 can be wire or wireless, depending upon the
application. Typical wireless links include a radio frequency type
in which the processor and display unit 420 can communicate with
other devices using radio frequency (RF) electromagnetic waves.
Other wireless links that are not beyond the scope of the invention
can include, but are not limited to, magnetic, optical, acoustic,
and other similar wireless types of links.
[0105] In the exemplary embodiment illustrated in FIG. 4, the
compartment sensors 405 are coupled to the processor and display
unit 420 with cables 430A, 430B which can include electrical
conductors for providing operating power to the light sources of
the compartment sensors 405 and for carrying output signals from
the detectors of the sensors 405 to the display unit 420. The
cables 430 may be coupled to a quad-channel coupler, a preamplifier
425A, 425B, and an integrated, multiple conductor cable 435.
Alternatively, all wires could be packaged or merged into a single
unit or cord or plug (not illustrated) for insertion into the
monitor for ease of management for the clinician and to prevent
misplacement of wire plugs into wrong sockets.
[0106] In addition to tracking compartment oxygen levels, the
processor and display unit 420 may receive data from a blood
pressure monitor 445. The blood pressure monitor 445 may be coupled
to a probe 440 that takes pressure readings from the patient at one
or more locations, such as, but not limited to, an arm with a cuff,
a needle in the volar wrist, the brachium (arm) via a
sphygmomanometer, or arterial line. The probe 440 can be any one of
a number of devices that can take blood pressure readings, such as,
but not limited to, automated inflating pressure cuffs
(sphygmomanometer), arterial lines, and the like. Similarly, other
types of blood pressure monitors 445 are not beyond the scope of
the invention. Further details of the relationship between blood
pressure and oxygen levels in the human body will be discussed and
described more fully below in connection with FIGS. 19-20.
[0107] The display and processing unit 420 can display values at
any one time for all compartment sensors 405 being used. While the
display and processing unit 420 only displays two oxygen levels for
the embodiment illustrated in FIG. 4, the display and processing
unit 420 could easily display all four values from the four
compartment sensors 405 that are being used to monitor the four
compartments of the lower leg 100.
[0108] Referring now to FIG. 5A, this figure illustrates a bottom
view of two pairs of compartment sensors 405 with each sensor 405
having a compartment alignment mechanism 410 and a central scan
marker 415 in addition to a separating device 505 according to one
exemplary embodiment of the invention. The substrate 530 of each
compartment sensor 405 can comprise a foam or plastic material that
may have a soft and comfortable outer layer. The separating device
505 is illustrated with a dashed line in FIG. 5A.
[0109] According to one exemplary embodiment the separating device
505 can comprise a perforation in the substrate 530. A perforation
is a series of cuts or removed portions positioned along a line
which can be perforated or separated. This means, for the exemplary
embodiment illustrated in FIG. 5A, the first compartment sensor
405A can be physically separated from the second compartment sensor
405B. The separating device 505 is not limited to perforations and
it can include other types of devices. For example, the separating
device 505 can comprise a zipper, a plastic seal line, hook and
loop fasteners and other like devices that would permit the rapid
and accurate expansion of compartment sensors 405 when used in a
trauma setting.
[0110] As noted above, the compartment sensors 405 can include
alignment mechanisms 410 and a central scan depth marker 415 in
order to accurately position the compartment sensors 405 over
compartments of interest. The alignment mechanisms 410 and central
depth markers 415 are illustrated with dashed or dotted lines
because they are "hidden" relative to the bottom view of the
compartment sensors 405 which are illustrated in FIG. 5A.
[0111] Each compartment sensor 405 may comprise an optical
transmitter 510 and an optical receiver 515. The optical
transmitter 510 may comprise an electrically actuated light source
for emitting a selected examination spectra. Specifically, the
optical transmitter 510 may comprise two or more narrow-bandwidth
LEDs whose center output wavelengths correspond to the selected
examination spectra. Each optical receiver 515 may comprise two or
more light detectors, such as photodiodes. In the embodiment
illustrated in FIG. 5A, the optical receiver 515 has a total of
four photodiodes in which pairs of photodiodes work together to
provide a "near" detector and a "far" detector. Each photo diode
must have two receptors to receive light at two separate
wavelengths to allow for calculations of oxy-hemoglobin and
deoxy-hemoglobin concentrations. Using two pairs of receptors
allows for a deep and shallow set to enable isolation of only the
deep tissue oxygenation (see FIG. 7).
[0112] Referring briefly now to FIG. 7, the "near" light detector
702B and the "far" light detector 702A are positioned within the
substrate material 530 at predetermined distances from the optical
transmitter 510. The "near" detector 702B formed by the two
photodiodes that are closest to the optical transmitter 510 have a
light mean path length 710B which is primarily confined to
"shallow" layers 705 of a compartment of interest. Meanwhile, the
"far" detector 702A formed by the pair of photodiodes that are
farthest from the optical transmitter 510 have a light mean path
710A that is longer than that of the "near" detector and is
primarily confined to "deep" layers of a compartment of interest in
a leg 100.
[0113] By appropriately differentiating the information from the
"near" or "shallow" detector 702B (which may produce a first data
set) from the "far" or "deep" detector 702A (which may produce a
second data set), a resultant value for the tissue optical density
may be obtained that characterizes the conditions within a
compartment of interest without the effects that are attributable
to the overlying tissue 705 which is adjacent to the compartment of
interest.
[0114] This enables the compartment monitoring system 400
(illustrated in FIG. 4) to obtain metabolic information on a
selective basis for particular regions within the patient and by
spectral analysis of the metabolic information and by using
appropriate extinction coefficients, a numerical value or relative
quantified value such as 402 of FIG. 4 may be obtained which can
characterize metabolites or other metabolite data, such as the
hemoglobin oxygen saturation, within the particular region of
interest. This region of interest is defined by the curved light
mean path 710A extending from the optical transmitter 510 to the
"far" or "deep" detector 702A and between this path 710A and the
outer periphery of the patient but excluding the region or zone
defined by the curved light mean path 710B extending from the
optical transmitter 510 to the "near" or "shallow" detector 26.
Further details of the compartment sensors 405 are described in
U.S. Pat. No. 6,615,065, issued in the name of Barrett et al.,
which is hereby incorporated by reference.
[0115] Referring back now to FIG. 5A, each compartment sensor 405
has its own cable 430 that provides power to the optical
transmitter 405A and that receives data from the optical receiver
515. Each compartment sensor 405 may also include a label 555 which
may comprise a name and an anatomical location to position the
compartment sensor 405 on a patient. This label may be placed on
the bottom of the sensor 405 that contacts the patient as well as
on the side that is opposite to the side which contacts the
patient. For example, the first sensor 405A can have a first label
555A that comprises the phrase, "Lateral" to describe the name of
the compartment that this compartment sensor 405A that is designed
to assess. The numerical depth can also be displayed on the label,
but is not limited to a single depth.
[0116] The first pair of compartment sensors 405A, 405B may be
coupled to the second pair of compartment sensors 405C, 405D with
an expansion device 535. The expansion device 535 may comprise an
elastic material that stretches. The expansion device 535 allows
the pair of compartment sensors 405 to be positioned on appropriate
parts of a patient to monitor any compartments of interest. The
four compartment sensor exemplary embodiment illustrated in FIG. 5A
is designed for the four compartments of a human lower leg 100.
[0117] The expansion device 535 is not limited to elastic material.
The expansion device can include other mechanisms which allow for
an adjustable separation between the pairs of compartment sensors
405 so that the compartment sensors 405 may be precisely and
appropriately positioned over specific compartments of interest.
The expansion device 535 may include, but is not limited to,
springs, tape, hook and loop fasteners, gauze, and other like
materials.
[0118] Referring now to FIG. 5B, this figure illustrates a bottom
view of the four compartment sensors 405 of FIG. 5A but with the
individual sensors 405 divided from one another through using the
separating device 505, such as the perforations, according to one
exemplary embodiment of the invention. Specifically, the first
compartment sensor 405A of the first pair of sensors 405A, 405B is
physically located away from the second compartment sensor 405B.
Similarly, the third compartment sensor 405C of the second pair of
sensors 405B, 405C is physically located away from the fourth
compartment sensor 405C. The separating device 505, the expansion
device 535 in combination with the alignment mechanism 410 and
central scan depth marker 415 can allow the compartment sensors 405
to be accurately and precisely positioned over compartments of
interest, such as the four compartments of a human leg 100. In
order to accurately monitor the appropriate compartment, a right
and left configuration can be provided since compartment alignment
would be reversed based on which leg is examined by the medical
practitioner. Each configuration would be labeled as right or left.
The configuration illustrated in FIGS. 5A and 5B are designed for
human left leg 100 where the expansion device would be positioned
over the tibia.
[0119] Referring now to FIG. 6A, this figure illustrates a bottom
view of a three sensor embodiment in which one sensor 605 of the
three compartment sensors 405A, 405B, 605 can scan at two or more
depths according to one exemplary embodiment of the invention.
Specifically, a compartment sensor 605 may include an optical
transmitter 510C that works with at least two different optical
receivers 515C1 and 515C2. As noted above, each optical receiver
515 may comprise two or more light detectors, such as photodiodes.
In the embodiment illustrated in FIG. 6A, each optical receiver
515C1 and 515C2 has a total of four photodiodes in which pairs of
photodiodes work together to provide "near" detector and "far"
detectors for a respective receiver 515C1, 515C2. This combination
allows the compartment sensor 605 to scan at least two different
depths. And because of the capability to scan at two different
depths, the compartment sensor 605 is provided with two different
central scan depth markers 415C1, 415C2.
[0120] Referring now to FIG. 6B, this figure illustrates the
compartment sensor 605 of FIG. 6A that can scan at two or more
depths in order to measure deeper compartments of an animal body
according to one exemplary embodiment of the invention. The two
optical receivers 515 of FIG. 6B work in principal in an identical
manner relative to the optical receiver described in connection
with FIG. 7 discussed above. This means that the combination of the
optical transmitter 510C and optical receiver 515C1 can provide an
oxygenation level for a first scan depth 620B of a patient.
Meanwhile, the combination of the optical transmitter 510C and the
optical receiver 515C2 can provide an oxygenation level for a
second scan depth 620A of a patient.
[0121] Therefore, this stacked compartment sensor 605 can be used
to measure the oxygenation level of a first compartment that may be
positioned underneath a second compartment, such as for the deep
posterior compartment of a lower leg 100 of a human body which is
positioned beneath the superficial posterior compartment of the leg
100. This stacked compartment sensor 605 can allow the display and
processing unit 420 to subtract the oxygenation level found at the
first scan depth 620B of the first compartment, such as the
superficial posterior compartment, from the oxygenation level at
the second scan depth 620A of the second compartment, such as the
deep posterior compartment.
[0122] The invention is not limited to the two stacked optical
receiver embodiment 605 illustrated FIGS. 6A and 6B, and can
include any number of optical receivers 515 positioned in the
substrate material 530 so that various scan depths can be made to
determine oxygenation levels within multiple compartments that may
be stacked on or positioned adjacent to one another in a sequential
or layered, shallow to deep arrangement.
[0123] Referring now to FIG. 8A, this Figure illustrates a linear
array 805 of compartment sensors 405 assembled as a single
mechanical unit that can provide scans at various depths 620A,
620B, 620C, and 620D. The compartment sensors 405 can be
simultaneously activated to produce their scans of various depths
620 at the same time when optical filters are used as will be
described more fully below in connection with FIG. 8C.
Alternatively, the sensors 405 of the linear array 805 can produce
their scans of various depths 620 by controlling a phase or timing
of the activation of the sensors 405 so that no two sensors 405 are
activated at the same time in order to reduce any potential of
optical interference between the sensors 405. This phasing of the
sensors can be controlled by the display and control unit 420 of
FIG. 4.
[0124] The first compartment sensor 405A can provide a first scan
depth 620A that is shorter or more shallow than a second scan depth
620B produced by the second compartment sensor 405B. The scan
depths 620 can increase in this manner along its longitudinal axis
which corresponds with its alignment mechanism 410 so that the
linear array 805 matches the one or more depths of a single
compartment of interest. As noted above in connection with FIG. 6B,
the scan depth 620 of a compartment sensor 405 is function of the
separation distance between the optical transmitter 510 and optical
receiver 515. For example, a scan depth 620 of a compartment sensor
405 can be decreased as the optical receiver 515 is moved closer
along the body of the sensor 405 towards the optical transmitter
510C.
[0125] One of ordinary skill in the art recognizes that many of the
compartments of the human body have various different geometries
and resulting depths relative to the outside skin of a patient. For
example, the compartments of the lower human leg 100 tend to have a
greater depth or volume adjacent to the knee and generally taper or
decrease in depth towards the ankle or foot. Therefore, linear
arrays 805 of compartment sensors 405 can be designed to have
depths that match a particular geometry of a compartment of
interest. To achieve these different scan depths 620, each
compartment sensor 405 can have an optical transmitter 510 and an
optical receiver 515 that is spaced or separated from each other by
an appropriate distance to achieve the desired scan depth 620. If a
compartment of interest has a substantially "flat" or "linear"
depth relative to the skin surface of a patient, the linear array
805 can be designed such that each compartment sensor 405 produces
scans with uniform depths (not illustrated) to match a compartment
with such a linear or flat geometry.
[0126] Like the single sensor embodiments described above in FIGS.
4-6A which are designed to measure individual compartments, the
compartment sensor array 805 may comprise an alignment mechanism
410 that can be positioned so that it corresponds with the
longitudinal axis 450 of a particular compartment. The compartment
sensor array 805 of FIG. 8A is not provided with any central depth
markers 415 like those of the single sensor embodiments since the
depth markers 415 may not be needed by the medical practitioner
since he or she will be assessing the entire length of a particular
compartment with the entire compartment sensor array 805 which is
unlike that of the single sensor embodiments. Alternatively,
multiple crosshatches and numerical depths (not illustrated) can be
positioned over each light source/receptor set to locate where each
measurement is obtained for identifying sites of a hematoma, which
will be described in more detail in connection with FIGS. 15-16
below. Additionally, these positions could be used to locate
appropriate amputation level for diabetics or peripheral vascular
disease, which is also described in more detail in connection with
FIGS. 15-16 below.
[0127] Referring now to FIG. 8B, this figure illustrates a linear
compartment sensor array 805 that can include optical transmitters
510 that are shared among pairs of light receptors 515. For
example, a single optical transmitter 510A1 can produce light rays
820A, 820B that can be used by two optical receivers 515A1, 515A2
that are disposed at angles of one-hundred eighty degrees relative
to each other and the optical transmitter 510A1 along the
longitudinal axis and alignment mechanism 410A of the compartment
sensor array 805A. As described previously, the light source and
receptor separation can be varied to best match the topography of
the compartment in the leg or other body part. Larger separation
would allow for deeper sampling in the proximal leg versus more
shallow depth closer to the ankle.
[0128] As discussed above in connection with the single sensor
array 805 of FIG. 8A, the sensors 405 of each compartment sensor
array 805 illustrated in FIG. 8B can be simultaneously activated to
produce their scans at the same time when optical filters (not
illustrated in FIG. 8B) are used as will be described more fully
below in connection with FIG. 8C. Alternatively, the sensors 405 of
each linear compartment sensor array 805 can produce their scans by
controlling a phase or timing of the activation of the sensors 405
so that no two sensors 405 are activated at the same time in order
to reduce any potential for optical interference between the
sensors 405. This phasing of the sensors can be controlled by the
display and control unit 420 of FIG. 4.
[0129] Like the single sensor embodiment illustrated in FIG. 5A,
the compartment sensor array 805 of FIG. 8B can comprise an
alignment mechanism 410 for aligning the structure with the
longitudinal axis 450 of a compartment as well as a separation
device 505A that can be used to divide the physical structure of
the paired array 805A, 805B into two separate linear compartment
sensor arrays 805A, 805B. The compartment sensor arrays 805 of FIG.
8B may also include labels 555 and an expansion device 535, like
those of FIG. 5A. The labels can be positioned on the front and
back sides of each compartment sensor array 805. While the optical
transmitters 510 and receivers 515 of FIG. 8B are illustrated in
functional block form, it is noted that these elements as well as
other numbered elements, which correspond to the numbered elements
of FIGS. 4-7, work similar to the embodiments described and
illustrated in FIGS. 4-7.
[0130] Referring now to FIG. 8C, this figure is a functional block
diagram of compartment sensor 405 that illustrates multiple optical
receivers 515 that may positioned on opposite sides of a single
optical transmitter 510 and that may be simultaneously activated to
produce their scans at the same time. This exemplary embodiment can
produce scans at the same time by using light with different
wavelengths. Using light with different wavelengths can help reduce
and substantially eliminate any optical interference that can occur
between multiple light rays that may be received by the multiple
optical receivers 515. While the optical receivers 515 of FIG. 8C
are illustrated in functional block form, it is noted that these
receivers 515 as well as other numbered elements, which correspond
to the elements of FIGS. 4-7, work similar to the embodiments
described and illustrated in FIGS. 4-7.
[0131] The two optical receivers 515A1, 515A2 of FIG. 8C may be
simultaneously activated when two optical filters 810A, 810B having
different wavelengths are used. The first optical filter 810A may
have a first wavelength of lambda-one (.lamda.1) which is different
than a second wavelength of lambda-two (.lamda.2) that is the
wavelength of the second optical filter 810B1. The optical
transmitter 510 can be designed to produce light having wavelengths
of the first and second wavelengths which correspond with the first
and second optical filters 810A, 810B.
[0132] Light 820A with a first wavelength can be produced by the
optical transmitter 510 propagating its light through a first
optical filter 810A1 that is designed to only let the first
wavelength pass through it. Similarly, Light 820B with a second
wavelength can be produced by the optical transmitter 510
propagating its light through a second optical filter 810B1 that is
designed to only let the second wavelength pass through it. A third
optical filter 810A2 corresponding with the first optical filter
810A1 can be designed to only pass the first wavelength such that
the optical receiver 515A1 only detects light of the first
wavelength. Similarly, a fourth optical filter 810B2 corresponding
with the second optical filter 810B1 can be designed to only pass
the second wavelength such that the optical receiver 515A2 only
detects light of the second wavelength.
[0133] In this way, simultaneous different compartment scans can be
produced at the same time with light having the first wavelength of
lambda-one (.lamda.1) and light having the second wavelength of
lambda-two (.lamda.2), in which the two optical receivers 515A1 and
515A2 share the same optical transmitter 510. This principal of
optical receivers 515 sharing the same optical transmitter 510 is
also illustrated in FIG. 8B which provides the compartment sensor
arrays 805 discussed above. Specifically, any optical transmitter
510/optical receiver 515 group that is positioned along a single
alignment mechanism 410 and longitudinal axis 450 can be designed
to have a unique wavelength relative to its neighbors along the
same line. So this means that each optical transmitter 510/optical
receiver 515 group of a particular compartment sensor array 805,
such as first array 805A, can be designed to have unique
wavelengths relative to each other for illuminating the same
compartment. Meanwhile, a neighboring compartment sensor array 805,
such as second array 805B, may have the same wavelength arrangement
as the first array 805A.
[0134] One of ordinary skill in the art recognizes that each light
optical transmitter and optical receiver design uses two separate
wave lengths to solve for oxy-hemoglobin and deoxy-hemoglobin
concentrations, as illustrated in FIG. 7. Therefore, the two
optical wavelength design described for FIG. 8C above may translate
into four or more wavelengths for each optical transmitter 510 and
pair of optical receivers 515. The two wavelength design for FIG.
8C was described above for simplicity and to illustrate how groups
of optical transmitters and optical receivers can operate at
different wavelengths relative to the groupings.
[0135] The invention is not limited to only two optical receivers
515 that share the same optical transmitter 510. The invention
could include embodiments where a single optical transmitter 510 is
shared by a plurality of optical receivers 515 greater than two
relative to the exemplary embodiment illustrated in FIG. 8C.
[0136] Referring now to FIG. 9A, this figure illustrates a
cross-sectional view of a left-sided human leg 100 that has the
four major compartments 905 which can be measured by the
compartment sensors 405 according to one exemplary embodiment of
the invention. A first compartment 905B (also noted with a Roman
Numeral One) of the lower human leg 100 comprises the anterior
compartment that is adjacent to the Tibia 910 and Fibula 915. A
first compartment sensor 405B is positioned adjacent to the
anterior compartment 905B and provides a first oxygenation scan
having a depth of 620B.
[0137] A second compartment 905A (also noted with a Roman Numeral
Two) of the lower human leg 100 comprises the lateral compartment
that is adjacent to the Fibula 915. A second compartment sensor
405A is positioned adjacent to the lateral compartment 905A and
provides a second oxygenation scan having a depth of 620A.
[0138] A third compartment 905D (also noted with a Roman Numeral
Three) of the lower human leg 100 comprises the superficial
posterior compartment that is behind the Tibia 910 and Fibula 915.
A third compartment sensor 405D is positioned adjacent to the
posterior compartment 905D and provides a third oxygenation scan
having a depth of 620D.
[0139] A fourth compartment 905C (also noted with a Roman Numeral
Four) of the lower human leg 100 comprises the deep posterior
compartment that is within a central region of the human leg 100. A
fourth compartment sensor 405C is positioned adjacent to the deep
posterior compartment 905C and provides a fourth oxygenation scan
having a depth of 620C.
[0140] Referring now to FIG. 9B, this figure illustrates a
cross-sectional view of a right-sided human leg 100 and possible
interference between light rays 820 of simultaneous oxygenation
scans made by the compartment sensors 405 into respective
compartments of interest according to one exemplary embodiment of
the invention. This figure illustrates how light rays 820 produced
by respective compartment sensors 405 can interfere with one
another. To resolve this potential problem, the activation and
hence, production of light rays 820, by the compartment sensors 405
can be phased so that light rays 820 produced by one compartment
sensor 405A are not received and processed by a neighboring
compartment sensor 405B, 405C. When light is emitted from the
compartment sensors 405 through tissue, the light does not travel
in a straight line. It is reflected and spreads throughout the
whole tissue. Therefore, light interference or noise would be a
significant concern for multiple light sources placed in close
proximity to each other. Alternatively, and as noted above, each
compartment sensor 405 can produce optical wavelengths that are
independent of one another in order to reduce any chances of
optical interference.
[0141] Referring now to FIG. 9C, this figure illustrates a position
930 of a compartment sensor 405C in relation to the knee 927 for
the deep posterior compartment 905C of a right sided human leg 100
according to one exemplary embodiment of the invention. As
illustrated in FIGS. 9A and 9B discussed above, the deep posterior
compartment sensor 405C can be positioned such that the sensor 405C
can directly sense the oxygenation levels of this compartment 905C
without penetrating or going through another compartment. With
respect to FIG. 9C, the deep posterior compartment 905C can be
accessed by placing the sensor along the posteromedial aspect of
the medial tibia. In other words, palpation of the shin bone will
allow the location of the tibia. The sensor 405 should be placed
just behind the bone on the inside of the leg along the
longitudinal axis 450C of the compartment 905C (not illustrated in
this Figure). The compartment sensor 405C can be aligned with the
longitudinal axis 450C of the deep posterior compartment 905C
through using the alignment mechanism 410C. The compartment sensor
405C can positioned at any point along the longitudinal axis 450C.
The location of this deep posterior compartment sensor 405C on the
lower leg 100 may be one inventive aspect of the technology since
it allows a direct scan of the deep posterior compartment 905C.
[0142] Referring now to FIG. 10, this figure illustrates an
exemplary display 1000 of numeric oxygenation values 402 as well as
graphical plots 1005 for at least two compartments of an animal
according to one exemplary embodiment of the invention. The
graphical plots 1005 can display the current instantaneous
oxygenation level for each compartment as a point as well as
historical data displayed as other points along a line that plots
the history for a particular compartment sensor 405. In other
words, the X-axis of the plots 1005 can denote time in any
increments while the Y-axis of the plots can denote oxygenation
levels monitored by a particular sensor 405.
[0143] While only two plots are illustrated, multiple plots can be
displayed for each respective sensor 405. In compartment sensor
array 805 deployments, the graphical plot 1005 can represent an
"average" of oxygenation levels measured by the multiple sensors of
a particular linear compartment sensor array 805. The display
device 420 can include controls 1015 that allow for the selection
of one or more compartment sensors 405 or one or more compartment
sensor arrays 805 for displaying on the display device 420. The
display of historical oxygenation levels of a compartment 905 over
time through the plots 1005 is a significant improvement over
conventional methods of direct pressure readings of compartments
905 which usually would only allow periodic measurements of
compartments 905 on the order of every fifteen or thirty minutes
compared to minutes or seconds now measured with the compartment
sensors 405 described in this document.
[0144] Referring now to FIG. 11, this figure illustrates single
compartment sensors 405 with alignment mechanisms 410 and central
scan depth markers 415 that can be used to properly orient each
sensor 405 with a longitudinal axis 450 of a compartment 905 of an
animal body according to one exemplary embodiment of the invention.
While the longitudinal axis 450 of a compartment (shown with broken
lines) cannot actually be seen on the external surface of a lower
human leg 100 by a medical practitioner, a medical practitioner can
envision this invisible axis 450 based on the anatomy of the leg,
such as looking at the knee 927 and comparing its orientation with
the ankle and foot of the leg 100. As described above, the
compartment extends from the knee to ankle and the sensor can be
placed over a portion or all of the compartment being measured.
With these single compartment sensor 405 embodiments, each sensor
405 can be positioned along the length of the longitudinal axis 450
to obtain an oxygenation level for a particular compartment 905 of
interest.
[0145] Referring now to FIG. 12, this figure illustrates
compartment sensor arrays 805 with alignment mechanisms 410 that
can be used to properly orient each array 805 with a longitudinal
axis 450 of a compartment 905 of an animal body according to one
exemplary embodiment of the invention. Since compartment sensor
arrays 805 will typically occupy close to the entire length of any
given longitudinal axis 450 of a compartment 905 of interest, the
individual sensors 405 of the compartment sensor array 805 are
usually not provided with central scan depth markers 415. In the
sensor array embodiments, the arrays 805 are usually provided only
with the alignment mechanism 410. However, the central scan depth
markers 415 could be provided if desired for a particular
application or medical practitioner (or both).
[0146] Referring now to FIG. 13A, this Figure illustrates various
locations for single compartment sensors 405 that can be positioned
on a front side of animal body, such as a human, to measure
oxygenation levels of various compartments 905 according to one
exemplary embodiment of the invention. FIG. 13A illustrates that
the invention is not limited to compartment sensors 405 that only
measure lower legs 100 of the human body. The compartment sensors
405 can measure various different compartments 905 such as, but not
limited to, compartments 905 of the arm, thighs, and abdomen.
[0147] Referring now to FIG. 13B, this Figure illustrates various
locations for single compartment sensors 405 that can be positioned
on a rear side of animal body, such as a human, to measure
oxygenation levels of various compartments 905 according to one
exemplary embodiment of the invention. Similar to FIG. 13A above,
the compartment sensors 405 shown in this Figure can measure
various different compartments 905 such as, but not limited to,
compartments 905 of the arm, thighs, and abdomen. Also, while
grouped compartment sensors 405 that are coupled together with
expansion devices 535 are not illustrated here (such as those
described in connection with FIG. 5A above), one of ordinary skill
recognizes that such grouped compartment sensors can be substituted
anywhere were the single compartment sensors 405 are shown.
[0148] Referring now to FIG. 14A, this Figure illustrates various
locations for compartment sensor arrays 805 that can be positioned
over compartments 905 on a front side of an animal body, such as a
human, to measure oxygenation levels of the various compartments
905 according to one exemplary embodiment of the invention. Like
the single compartment sensor embodiments of FIGS. 13A-13B
described above, the compartment sensor arrays 805 can measure
various different compartments 905 such as, but not limited to,
compartments 905 of the arm, thighs, and abdomen.
[0149] Referring now to FIG. 14B, this Figure illustrates various
locations for compartment sensor arrays 805 that can be positioned
over compartments 905 on a rear side of an animal body, such as a
human, to measure oxygenations levels of the various compartments
905 according to one exemplary embodiment of the invention. Also,
while grouped compartment sensor arrays 805 that are coupled
together with expansion devices 535 are not illustrated here (such
as those described in connection with FIG. 8B above), one of
ordinary skill recognizes that such grouped compartment sensor
arrays 805 can be substituted anywhere were the individual
compartment array sensors 805 are shown.
[0150] Referring now to FIG. 14C, this Figure illustrates an
exemplary display 1300 and controls for the display device 420 that
lists data for eight single compartment sensors 405 according to
one exemplary embodiment of the invention. The eight single
compartment sensors 405 may be monitoring compartments of two limbs
of an animal, such as two lower legs of a human patient. One limb
is usually uninjured while the other limb is typically injured,
though the system is not limited to unilateral injuries.
[0151] The display 1300 may provide up to eight different plots or
graphs 1335A, 1330A, 1325A, 1320B, 1335B, 1330B, 1325B, 1320B of
data that are taken from the eight different sensors 405 or sensor
arrays 805. The first pair of right and left leg sensors may
monitor the anterior compartment 905B of FIG. 9A which is displayed
with the letter "A" for the first row 1335 of data. The second pair
of right and left leg sensors may monitor the lateral compartment
905A of FIG. 9A which is displayed with the letter "L" for the
second row 1330 of data. The third pair of right and left leg
sensors may monitor the deep posterior compartment 905C which is
displayed with the letters "DP" for the third row 1325 of data. The
first pair of right and left leg sensors may monitor the
superficial posterior compartment 905D which is displayed with the
letters "SP" for the fourth row 1320 of data.
[0152] The display 1300 may also provide a measure of a difference
1340 in oxygenation levels between the injured limb or region and
the uninjured limb or region. This difference may be displayed by
listing the two oxygenation levels of each respective limb
separated by a slash "I" line. Underneath the two oxygenation
levels for a respective pair of sensors for the injured and
uninjured limbs, a value which is the difference between the
oxygenation levels displayed above it may be listed. For example,
for the first oxygenation difference value of 1340A, the
oxygenation level for the right leg sensor is the value of
forty-four while the value for the left leg sensor is the value of
sixty-five. In this exemplary embodiment, the right leg is injured
while the left leg is uninjured. The difference value displayed
under the two oxygenation levels for the first data set 1340A is
twenty-one.
[0153] Initial data from patients with extremity injuries measured
by the inventor have shown that muscular skeletal injuries cause
hyperemia (increased blood flow and oxygen) in the injured
extremity. If a compartment syndrome develops, the oxygenation
drops from an elevated state to an equal and then lower level with
comparison to the uninjured limb. Therefore when comparing injured
and uninjured extremities, the injured limb should show increased
oxygenation levels. If levels begin to drop in the injured limb
compared to the uninjured limb, an alarm or alert can be triggered
to warn the medical practitioner. This alarm can be visual or
audible (or both).
[0154] With the display 1300, a medical practitioner can modify how
data is displayed by pressing the "mode" button 1305 on the display
1300 (which may comprise a "touch-screen" type of display). The
mode button 1305 permits the medical practitioner to change the
display of the screen. This function would allow for selection
between multiple different settings to allow for data downloading,
changing the time frame for which data is displayed, etc. With the
time mark "button" 1310, the medical practitioner can mark or
"flag" certain data points being measured for later review. With
the select "button" 1315, the medical practitioner can select
between the multiple options that can be accessed through the mode
button.
[0155] While the above description of FIG. 14C mentioned that eight
single compartment sensors 405 produced the data of the display
1300 of FIG. 14C, the single compartment sensors 405 can be easily
substituted by compartment sensor arrays 805. In such a scenario in
which compartment sensor arrays 805 are used to produce the data of
display 1300, the displayed values can be an "average" of the
values taken from a given array 805. This "average" can be
calculated by the processor of the display device 420.
[0156] Referring now to FIG. 14D, this Figure illustrates an
exemplary display 1302 of providing users with guidance for
properly orienting a single compartment sensor 405 over a
compartment of an animal, such as a human leg, according to one
exemplary embodiment of the invention. The display 1302 can be
generated by display device 420 so that a medical practitioner is
provided with instructions and graphical information on how to
mount and operate the compartment sensors 405 of the system. The
display may provide an illustration of the body part having the
compartment of interest. In the exemplary embodiment of FIG. 14D,
the compartment of interest is located within the lower human leg
100.
[0157] An illustration of the lower human leg 100 is provided in
display 1302. On the body part having the compartment of interest,
the display device 420 can identify the longitudinal axis 450 by
marking or flagging this axis 450 with a text box label 1309. The
display 1302 can also identify an illustration of the compartment
sensor 405A by marking or flagging this illustration with another
text box label 1311. The display 1302 can also identify a general
region for a compartment of interest by encapsulating the region
with a geometric outline such as an ellipse and marking this
ellipse with another text box label 1307.
[0158] The display 1302 can also include a miniaturized view 1301
of a cross-section of the compartment of interest, similar to the
views illustrated in FIGS. 9A and 9B for this exemplary embodiment
that is assessing a lower leg compartment 905. The display 1302 may
also allow the user to expand the cross-sectional view 1301 of the
compartment of interest by allowing the user to double-click or
touch the actual display of the cross-section. Multiple sections
including an axial, coronal and/or sagittal view may be included in
the on-screen instructions for placement. Upon such action by the
user, the display device 420 may enlarge the cross-sectional view
1301 to a size comparable or equivalent to that illustrated in FIG.
9A. Once the medical practitioner has positioned the sensor 405 on
the patient over the desired compartment of interest, the display
1302 can be refreshed to include the next compartment of
interest.
[0159] Referring now to FIG. 15A, this Figure illustrates a front
view 1500 of lower limbs, such as two lower legs of a human body,
that are being monitored by four compartment sensor arrays 805
according to an exemplary embodiment of the invention. The four
sensor arrays 805 can be positioned along compartments of interest
by orienting the alignment mechanism 410 along the longitudinal
axis of a respective compartment. Multiple central scan depth
markers 415 and numerical depths (not illustrated in FIG. 15A) can
be positioned over each light source/receptor set of a sensor array
805 to locate where each measurement is obtained for identifying
sites of a hematoma, which will be described in more detail in
connection with FIGS. 15B-16 below.
[0160] Referring now to FIG. 15B, this Figure illustrates a display
1505 of the display device 420 that can be used to monitor
hematomas and/or blood flow according to one exemplary embodiment
of the invention. The display 1505 can include an average
oxygenation level 1515 of thirty-six at an instant of time that is
determined from the two compartment sensor arrays 805A1, 805B1 of a
patient's right leg 100A which is injured in this exemplary case.
Meanwhile, the display 1505 can also include an average oxygenation
level 1510 of fifty-three at the same instant of time that is
determined from the two compartment sensor arrays 805A2, 805B2 of a
patient's left leg 100B which is uninjured in this exemplary
case.
[0161] The display 1505 can also provide oxygenation values that it
is receiving from each of the individual sensors 405 in a first
sensor array 805 not illustrated. For the injured right leg 100A
illustrated in the display, the oxygenation levels vary between
thirty-two and forty-four. However, in the exemplary embodiment
illustrated in FIG. 15B, there are three individual sensors 405
(not illustrated in this Figure) of the sensor array 805A1 that are
not producing any oxygenation values which have been provided with
the letter "H" to denote a possible hematoma. For the uninjured leg
100B, the individual compartment sensors 405 (not illustrated) of
the two sensor arrays 805A2, 805B2 have provided oxygenation levels
that range between 50 and 54 which are believed to be in the normal
range for normal blood flow. Also, While individual sensors 405
that are not illustrated here (such as those described in
connection with FIG. 4A above), one of ordinary skill recognizes
that such individual compartment sensors 405 can be substituted
anywhere were the compartment array sensors 805 are shown.
[0162] Referring now to FIG. 16, this Figure illustrates a display
1600 of the display device 420 for an instant of time after the
display of FIG. 15B and which can be used to monitor hematomas
and/or blood flow according to one exemplary embodiment of the
invention. The display 1600 illustrates that the hematoma or
absence of healthy blood flow condition being tracked by sensor
arrays 805A1, 805B1 (of FIG. 15A) is expanding. The display 1600
can include a warning message 1605 such as "WARNING--HEMATOMA
EXPANDING!" to alert the medical practitioner of the changing
conditions of the compartments 905 of interest in the injured or
traumatized area. In FIG. 16, the average oxygenation level 1510 of
the injured leg 100A decreased in value from thirty-six to
twenty-four. Further, the number of individual sensors 405 (not
illustrated but values shown) detecting a hematoma or lack of
healthy blood flow condition increased from two sensors detecting
the condition in FIG. 15B to seven sensors detecting the condition
in FIG. 16 as indicated by the "H" values on display 1505.
Meanwhile, the average oxygenation level 1515 of the uninjured left
leg 100B changed slightly from fifty-three to fifty-two.
[0163] With the display 1600 that provides the compartment sensors
405 with "H" values in combination with the central scan depth
markers 415 provided on the sensor arrays 805, the medical
practitioner can easily locate the physical sites on the leg 100
that contain the hematoma or lack of healthy blood flow. These
positions can also be used by the medical practitioner to locate
appropriate amputation level for diabetics or peripheral vascular
disease, since peripheral vascular disease is typically worse
distally (closer to the toes) and gradually improves closer to the
knee. The compartment sensor 405 or more specifically the array
system 805 can be used to aid a clinician or surgeon in determining
the level of amputation for peripheral vascular disease and or
diabetes mellitus. By obtaining multiple readings at different
levels from the knee to the ankle, the surgeon can determine the
appropriate level for amputation. The level of amputation is
important since if the tissue is not well perfused, the surgical
wound will not heal and require revision surgery and more of the
patient's leg must be removed.
[0164] Referring now to FIG. 17, this Figure illustrates a sensor
design for measuring the optical density of skin according to one
exemplary embodiment of the invention. The depth of tissue
measurement using NIRS is based on separation of the optical
transmitter 510 and the optical receiver (see FIGS. 18A-B). In
order to obtain readings of only the skin (very shallow depths),
the separation between the optical transmitter 510 and optical
receiver 515 would have to be very small and which may not be
feasible. In this exemplary embodiment, the sensor 405 can comprise
a material 1705 of known optical density that can be positioned
between the substrate 530 and the skin 1710. In this way, the light
mean paths 710A, 710B will only penetrate upper layers of the leg
100, such as the skin layers 1710. The thickness of the known
material 1705 can be varied to adjust for different desired scan
depths made by the light mean paths 710A, 710B. Since the optical
density of the material 1705 is known, then any near infrared light
absorption will be attributable to the layers of tissue of
interest. And in this case, the optical density of the skin 1710
can be determined. According to a further exemplary embodiment, one
of the photoreceptors 702A, 702B can be removed from the optical
receiver 515 in order to decrease the depth of the scan. For
example, if the second photoreceptor 702A was removed, the depth of
the scan would only extend as deep as the light mean path 710B for
the photoreceptor 702B.
[0165] The inventor has recognized that skin pigmentation can
affect the oxygenation values of a patient that uses near-infrared
compartment sensors 405. This effect on oxygenation levels is also
acknowledged in the art. See an article published by Wassenar et
al. in 2005 on near-infrared system (NIRS) values. As with solar
light, skin pigmentation caused by the biochemical melanin is a
major factor in light absorption. In the inventor's research, skin
pigmentation has been demonstrated to be a significant factor in
measuring oxygenation levels among patients. The inventor has
discovered that there was approximately a ten point difference when
comparing low pigmentation subjects (Caucasians, Hispanics &
Asians) with higher pigmented subjects (African American). The
pigmented subjects had average scores of approximately ten points
lower when compared to non-pigmented subjects. See Table 1 below
that lists data on the difference between measured oxygenation
levels of uninjured patients due to skin pigmentation.
TABLE-US-00001 TABLE #1 Difference in measured oxygenation levels
between White and Dark Pigmentation Skinned Subjects Avg White Dark
Diff p value Anterior 60 51 9 <0.0001 Lateral 61 52 9 <0.0001
Deep Post 66 53 13 <0.0001 Sup Post 66 52 14 <0.0001 N = 10
(White) and 17 (Dark) (This study compared 10 white subjects to 17
darker pigmented subjects) Statistics used a non paired, two tail
student t-test for p-values P values show very statistically
significant differences between white (Caucasian, Asian &
Hispanic) vs. Dark (African American) subjects
[0166] The p-value can be described as the chance that these
findings were due to chance alone. In all four compartments, the
chance of finding the difference (9-14) in average value between
the two groups (dark and white) was less than 0.01% or less than 1
out of 10,000. In other words the likelihood of these findings
occurring by chance alone is very unlikely. By convention,
statistically significant findings are considered to be less than
5% or a p-value of <0.05 in comparison. See APPENDIX A for the
raw data that supports this data.
[0167] Conventional studies (Wassenar et al., 2005 and Kim et al.,
2000) have showed that when subjects increase their activity, dark
pigmented people tend to have higher rates of loss of signal.
[0168] There have been no attempts as of this writing to account
for skin pigmentation, or optical density, in oxygenation levels
detected with sensors like the compartment sensor 405 discussed
above. Therefore, the design illustrated in FIGS. 17-18 have been
developed by the inventor to account for pigmentation optical
density. With the embodiments of FIGS. 17-18, skin pigmentation
influences can be calibrated and accounted for when measuring
oxygenation levels with sensors 405 that use near infrared light
absorption principles. In this way, true or more accurate
oxygenation levels of subcutaneous tissue such as muscle, cerebral
matter or organ tissue may be obtained. This calibration or
pigmentation accounting would also allow for comparison of values
between different patients, since each individual will likely have
different skin pigmentation values.
[0169] Referring now to FIG. 18A, this Figure illustrates a sensor
405 that can penetrate two layers of skin 1805A, 1805B to obtain
optical density values according to one exemplary embodiment of the
invention. The distance D1 between the optical transmitter 510 and
optical receiver 515 can be predetermined based on the scan depth
620A that is desired.
[0170] Referring now to FIG. 18B, this Figure illustrates a sensor
405 that can penetrate one layer of skin 1805A according to one
exemplary embodiment of the invention. This figure demonstrates how
the depth of measurement for oxygenation levels using the sensors
405 that operate according to near infrared light absorption
principles is usually directly proportional to the optical
transmitter and optical receiver separation distance D. In FIG.
18B, the separation distance D2 is smaller than that of the
separation distance D1 of FIG. 18A. Accordingly, the central scan
depth 620B of FIG. 18B is also shorter than the central scan depth
620A of FIG. 18A.
[0171] According to one exemplary embodiment of the invention, the
separation D1 and D2 between the optical transmitter 510 and
optical receiver 515 can range between approximately five
millimeters to two centimeters. This separation distance D can be
optimized to obtain an accurate reading of only the skin in the
particular area of interest. One of ordinary skill in the art
recognizes that skin is not a constant depth or thickness
throughout a human body. Therefore, the depth 620 of the scan of a
sensor 405 for which it is designed (ie. the leg for compartment
syndromes) may preferably be designed to vary to obtain an accurate
optical density value for skin in that specific body location.
[0172] Referring now to FIG. 18C, this figure illustrates a
modified compartment monitoring system 1800 that can correlate skin
pigmentation values with skin optical density values in order to
provide offset values for oxygenation levels (derived from near
infrared light absorption principles) across different subjects who
have different skin pigmentation according to one exemplary
embodiment of the invention. The system 1800 can comprise a central
processing unit of the display device 420 or any general purpose
computer. The CPU of the display device 420 can be coupled to a
compartment sensor 405' that has been modified to include a skin
pigment sensor 1820.
[0173] The skin pigment sensor 1820 may be provided with a known
reflectance and that can be used to calibrate the compartment
sensor 405' based on relative reflectance of skin pigment which can
affect data generated from oxygenation scans. For example, the skin
sensor 1820 can comprise a narrow-band simple reflectance device, a
tristimulus colorimetric device, or scanning reflectance
spectrophotometer. Conventional skin sensors available as of this
writing include mexameter-18 (CK-electronic, Koln, Germany),
chromameters, and DermaSpectrometers. Other devices appropriate and
well suited for the skin sensor 1820 are found in U.S. Pat. No.
6,070,092 issued in the name of Kazama et al; U.S. Pat. No.
6,308,088 issued in the name of MacFarlane et al; and U.S. Pat. No.
7,221,970 issued in the name of Parker, the entire contents of
these patents are hereby incorporated by reference.
[0174] The skin sensor 1820 can determine a standardized value for
skin pigmentation of a patient by evaluating the melanin and
hemoglobin in the patient's skin. Once the skin melanin or pigment
value is determined it can be correlated to its calculated
absorption or reflectance (effect) on the oxygenation levels using
a predetermined calibration system, such as the skin pigment table
1825 illustrated in FIG. 18C. From the skin pigment table 1825, the
CPU 420 can identify or calculate an oxygenation offset value that
can be incorporated in tissue hemoglobin concentration calculations
for deep tissue oxygenation scans. Accounting for skin pigmentation
will usually allow for information or values to be compared across
different subjects with different skin pigmentation as well as
using the number as an absolute value instead of monitoring simple
changes in value over time.
[0175] Referring now to FIG. 19, this figure is a functional block
diagram of the major components of a compartment monitoring system
1900 that can monitor a relationship between blood pressure and
oxygenation values according to one exemplary embodiment of the
invention. The compartment monitoring system 1900 can include a CPU
420A of a display device 420B that is coupled to compartment
sensors 405, a blood pressure probe 440, and a blood pressure
monitor 445. The CPU 420A may also be coupled to a voice
synthesizer 1905 and a speaker 1907 for providing status
information and alarms to a medical practitioner.
[0176] The CPU 420A can receive data from the blood pressure
monitor 445 in order to correlate oxygenation levels with blood
pressure. The CPU 420A can activate an alarm, such as an audible or
visual alarm (or both) with the voice synthesizer 1905 and speaker
or displaying a warning message on the display device 420B when the
diastolic pressure of a patient drops. It has been discovered by
the inventor that perfusion can be significantly lowered or stopped
at low diastolic pressures and when compartment pressures are
greater than the diastolic pressure. According to one exemplary
embodiment, in addition to activating an alarm, the CPU 420A of the
compartment monitoring system 1900 can increase a frequency of data
collection for oxygenation levels and/or blood pressure readings
when a low blood pressure condition is detected by the system
1900.
[0177] Referring now to FIG. 20, this figure is an exemplary
display 2005 that can be provided on the display device 420 and
which provides current blood pressure values 2020 and oxygenation
levels 2025 of a compartment of interest according to one exemplary
embodiment of the invention. Display 2005 can be accessed by
activation of the mode switch 1305 of FIG. 14.
[0178] In addition to displaying current blood pressure values 2020
and oxygenation levels 2025, the display 2005 can further include
graphs that plot a blood pressure curve 2035 and an oxygenation
level curve 2040. The blood pressure curve 2035 can represent blood
pressure data taken over time that is plotted against the time axis
2030 (X-axis) and the blood pressure axis 2010 (first Y-axis
values). The oxygenation level curve 2040 can represent oxygenation
levels taken over time that is plotted against the time axis 2030
(X-axis) and the oxygenation level axis 2015 (second Y-axis
values).
[0179] In this way, the relationship between blood pressure and
potential compartment pressure based on the oxygenation levels can
be directly tracked and monitored by a medical practitioner. As
noted above, it has been discovered by the inventor that perfusion
can be significantly lowered or stopped at low diastolic pressures
and when compartment pressures are greater than the diastolic
pressure. So when the blood pressure of a patient starts to drop
and if the oxygenation levels of a compartment being tracked also
start to drop, the CPU 420A can sound an audible alarm and display
a warning message 2035 to the medical practitioner to alert him or
her of this changing condition. This correlation between hemoglobin
concentration (oxygenation levels) and diastolic pressure can be
used to estimate intra-compartmental pressures without having to
use invasive, conventional needle measurements.
[0180] Additionally, a running average of oxygenation values over a
certain time period can be calculated and displayed. The time
period could be altered between multiple time periods from seconds
to minutes to even hours. The purpose of the running average would
be to limit the amount of variability of the oxygenation values
displayed on the screen. The current instantaneous value that is
displayed in existing models is very labile. By using a running
average, the trends can be monitored and the instantaneous changes
can be smoothed out. This ability to decrease volatility would be
important to prevent continual alert triggering if an alarm value
was set by the medical practitioner.
[0181] In addition, with blood pressure input as described above,
the diastolic, systolic and/or mean arterial pressure (MAP) can be
displayed (not illustrated) against time on the same graph. Using
the two data series of oxygenation and diastolic blood pressure, an
estimate of perfusion pressure (diastolic pressure minus
intra-compartmental pressure) can also be estimated by the CPU
420A.
[0182] Referring now to FIG. 21, this figure is a functional block
diagram that illustrates material options for a compartment sensor
405 according to one exemplary embodiment of the invention.
Functional block 2105 indicates that the structure of the
compartment sensor can be made with sterile materials. For example,
the substrate 530 (not illustrated) of the sensor 405 may be made
of anyone or combination of the following materials: various
polymers such as the polyurethanes, polyethylenes, polyesters, and
polyethers or the like may be used. Alternatively, each compartment
sensor can be made with a sterile coating 2110 that encapsulates
the compartment sensor 405. The sterile coating can be applied
during manufacturing of the sensor 405 or it can be applied after
manufacturing and provided as a container or sealable volume.
Additionally, once the unit is constructed and finished, the device
can be sterilized using one or more off multiple processes
including but not limited to chemical, heat, gas or irradiation
sterilization.
[0183] Referring now to FIG. 22, this figure illustrates an
exemplary clinical environment of a compartment sensor 405 where
the sensor 405 can be positioned within or between a dressing 2205
and the skin 1805 of a patient according to one exemplary
embodiment of the invention. Since the inventive compartment sensor
405 can be made with or enclosed by sterile materials as noted in
FIG. 21 above, the compartment sensor 405 or an sensor array 805
can be positioned between a dressing 2205 and a skin layer 1805 of
a patient intra-operatively. In this way, a medical practitioner
can monitor a compartment 905 of interest without the need to
remove the dressing 2205 or adjust the position of the compartment
sensor 405.
Case Studies Using Compartment Sensors 405 and Conventional
Pressure Measuring Methods
Case I
[0184] In 2007, a 44 year old Caucasian male fell 20 feet
sustaining an isolated closed proximal tibia fracture with
extension into the knee. Initial treatment included external
fixation for stabilization on the day of injury. During surgery the
compartments were firm but compressible. At post operative check
revealed that the compartments were more firm. There was mild pain
with passive stretch, though the patient was diffusely painful
throughout both lower extremities. Intra-compartmental pressures
were measured for all four compartments using a conventional needle
method with a Striker device (Stryker Surgical, Kalamazoo, Mich.).
The anterior and lateral pressures measured 50 mm Hg and the
superficial and deep posterior compartments were 48 mm Hg. The
diastolic pressure was 90 mm Hg resulting in a 40 mm Hg perfusion
pressure.
[0185] Tissue oxygenation (StO.sub.2) or oxygenation levels were
evaluated using two compartment sensors 405. The oxygenation levels
were approximately 80% in all four compartments. The compartment
sensors 405 were placed on the lateral and deep posterior
compartments for continual monitoring, which maintained oxygenation
values near 80%. Higher percentage oxygenation levels indicate more
perfusion and higher oxy-hemoglobin concentrations.
[0186] All clinical decisions were based of the clinical symptoms
and pressure measurements and not on the oxygenation levels. Two
hours passed and compartment pressures were repeated. The anterior
and lateral compartments remained at 50 mm Hg. The superficial and
deep posterior compartments rose to 50 mm Hg as well. The patient's
diastolic pressure remained at 90 mm Hg maintaining 40 mm Hg of
perfusion pressure. The oxygenation values remained near 80% for
both the lateral and deep posterior compartments. Clinical symptoms
were monitored closely throughout the night.
[0187] Approximately 24 hours after the initial injury, the patient
became more symptomatic and began requiring more pain medication.
Intra-compartmental measurements were repeated. The anterior and
lateral compartments remained at 51 mm Hg. The superficial and deep
posterior compartments measured 61 mm Hg and 63 mm Hg respectively.
However, the diastolic pressure dropped to 74 mm Hg decreasing the
perfusion pressure to 11 mm Hg. Based on the pressure measurements
and clinical symptoms, the patient underwent fasciotomy and was
found to have no gross evidence of muscle necrosis or neuromuscular
sequelae at late follow up.
[0188] Throughout the monitoring period, the lateral compartment
maintained an oxygenation level of approximately 80%. The
oxygenation levels in the deep posterior compartment began in the
eighties and started to drop approximately three hours after the
second compartment pressure measurement. At time of fasciotomy, the
oxygenation level for the deep posterior compartment was 58%. The
gradual decline in muscle oxygenation mirrored the decrease in
perfusion pressure over an extended period of time.
[0189] This first case suggests that the compartment sensors 405
can be used to continually monitor an injured extremity. Initially,
the patient had elevated intra-compartmental pressures, but the
perfusion pressure was greater than 30 mm Hg. The ensuing increase
in clinical symptoms and decrease in perfusion pressure correlated
with the gradual decrease in oxygenation levels. Impaired perfusion
was reflected in a decline in the oxygenation levels. These results
are consistent with a previous study by Garr et al. who showed a
strong correlation between oxygenation levels and perfusion
pressures in a pig model. This case also demonstrates the ability
of compartment sensors 405 to differentiate between compartments in
the leg since the oxygenation levels in the lateral compartment
remained elevated while the deep posterior values declined.
Case II
[0190] Also in 2007, a 32 year old Hispanic male sustained an
isolated, closed Schatzker VI tibial plateau fracture after falling
from a scaffold. On initial evaluation, the patient had tight
compartments, but there were no clinical symptoms of compartment
syndrome. Active and passive range of motion resulted in no
significant pain. Based on the concerns for the tense leg,
intra-compartmental pressure measurements were obtained using a
Stryker device.
[0191] All compartments were greater than 110 mm Hg. The patient's
blood pressure was 170/112 mm Hg. The decision to perform a four
compartment fasciotomy was made. The compartment sensors 405 were
placed on the deep posterior compartment as well as the lateral
compartment for continual monitoring. The lateral compartment was
unable to give a consistent reading due to hematoma interference.
The initial reading for the deep posterior was an oxygenation level
of 65%. The deep posterior tissue oxygenation level steadily
declined from 65% to 55% over the hour of preoperative
preparation.
[0192] Upon intubation, a sharp drop in the oxygenation levels from
55% to 43% was observed. The anesthesia record showed a concomitant
drop in blood pressure at the time of induction from 171/120 mm Hg
to 90/51 mm Hg. The patient underwent an uneventful fasciotomy and
external fixation. Tissue examination showed no gross signs of
muscle necrosis and at nine months follow-up there were no signs of
sequelea. The oxygenation level monitoring of the compartment was
acutely responsive and showed real time changes to a decline in
perfusion pressure in an injured extremity.
[0193] The responsiveness of the compartment sensors 405 to
intra-compartmental perfusion pressure is demonstrated by this
second case study. This patient was initially asymptomatic even
though his compartments were over 110 mm Hg in all compartments.
The oxygenation levels from the compartment sensors 405 were able
to detect gradual perfusion declines over the hour prior to
fasciotomy. Prior to induction of anesthesia, the patient was able
to maintain some tissue oxygenation by maintaining a high diastolic
blood pressure. Once the patient was anesthetized during
intubation, the diastolic pressure was significantly reduced. The
oxygenation levels of the compartments dropped within thirty
seconds of induction because the slight perfusion gradient was
completely abolished by the induced hypotension.
Case III
[0194] In 2007, a 62 year old Asian male suffered a closed midshaft
tibia fracture in a motor vehicle crash. The patient was
unresponsive and hypotensive at the scene of the accident and
intubated prior to arrival. Upon presentation, the patient was
hypotensive with a blood pressure of 90/55 mm Hg. The injured leg
was clinically tight on examination.
[0195] Oxygenation levels were measured for all four compartments.
The oxygenation levels were approximately at 50% for the anterior
and lateral compartments while the two posterior compartments were
approximately at 80%. The compartment sensors 405 were placed on
the anterior and superficial posterior compartments for continued
monitoring. Intra-compartmental pressures were measured at 50 mm Hg
and 52 mm Hg in the anterior and lateral compartments respectively
using the conventional Striker device (needle pressure measuring
method). The superficial and deep compartment pressures were 19 mm
Hg and 20 mm Hg respectively. After the patient was stabilized by
the trauma team, he underwent fasciotomy. There were no gross signs
of muscle necrosis and no complications at 7 months follow-up.
Muscle oxygenation was able to differentiate between compartments
with hypoperfusion and adequate perfusion in a hypotensive and
intubated patient.
[0196] This third case is evidence that the compartment sensors 405
are useful in assessing established or existing compartment
syndromes. The compartment sensors 405 can provide useful
information in patients that are unable to give feedback during a
clinical examination such as this patient who was intubated and
hypotensive upon examination. These findings correlate with the
findings by Arbabi et al. who demonstrated oxygenation levels to be
responsive in hypotensive and hypoxic pigs in a laboratory setting.
The compartment sensors 405 can distinguish between different
compartments and their respective perfusions. Clinically, in this
case, the whole leg was tense, but intra-compartmental pressures
were only elevated in the anterior and lateral compartments. The
oxygenation levels measured by the compartment sensors 405 were
proportional to the perfusion pressure with low values in the
anterior and lateral compartments, but elevated values in the two
posterior compartments.
Conclusion for Three Case Studies:
[0197] These three cases suggest that compartment sensors 405 are
responsive and proportional to perfusion pressures within the
injured extremity. These findings support previous studies
documenting the importance of perfusion pressure and not an
absolute value in the diagnosis of compartment syndrome. The
compartment sensors can distinguish between compartments and is
useful in the unresponsive, intubated and hypotensive patient.
Lastly, the compartment sensors 404 have the potential to offer a
continual, noninvasive and real time monitoring system that is
sensitive in the early compartment syndrome setting. In all three
cases, a difference in oxygenation levels was demonstrated prior to
any irreversible tissue injury.
Case IV
[0198] A 60 year old Middle Eastern male was shot in the right
thigh. Initially the thigh was swollen but the patient was
comfortable. After approximately 12 hours after the initial injury
the patient began to complain of increasing pain and required more
pain medication. The thigh was more tense upon clinical exam. The
patient was taken to the OR for fracture fixation and potential
fasciotomy of the thigh.
[0199] NIRS sensors were placed on the anterior, posterior and
medial (adductors) compartments of the thigh. Values for the
injured side were similar or decrease when compared to the
uninjured side. As previously described, injured tissue should show
increased values due to hyperemia. The injured side anterior,
posterior and medial values were 54, 53 and 63 respectively. The
uninjured values for the anterior, posterior and medial were 51, 55
and 63 respectively.
[0200] The compartment pressures were measured in all three
compartments. The intra-compartmental pressures for the anterior,
posterior and adductors were 44, 59 and 30 respectively. Once the
patient was induced for anesthesia and the patient's blood pressure
dropped from 159/90 to 90/61, the patients NIRS values dropped
within in 30 seconds of the his blood pressure drop. Once the blood
pressure was dropped and the perfusion pressure was eliminated, the
new values for the anterior, posterior and medial compartments were
29, 40 and 35.
Study: Sphygmomanometer Model & Invention's Sensitivity &
Responsiveness
[0201] A study was conducted to determine the sensitivity and
responsiveness of the inventive compartment monitoring system 400.
Specifically, the purpose of the study was to evaluate the
invention over the anterior compartment with a cuff around the
thigh at different pressures (simulating a compartment Syndrome) to
show responsiveness to increasing pressures in the leg.
[0202] The inventor's hypothesis was that the inventive compartment
monitoring system 400 will show normal oxygenation at levels below
pressures equivalent to compartment syndrome. Once pressures become
equal to the diastolic blood pressure, it was believed the
inventive system 400 would show significant deoxygenation because
the capillary perfusion pressure will be passed. Continued
monitoring will be obtained until a plateau or nadir is
obtained.
Materials & Methods:
[0203] Thigh Cuff Pressures: 0 mmHg: Baseline; Increase cuff by 10
mmHg and hold for 10 minutes; At the end of each ten minute period
blood pressure and NIRS values were obtained; Repeat incremental
increases until obtain decreased oxygenation level readings; and
Observe post release response & time to return to baseline
Outcomes:
[0204] It was confirmed that the compartment monitoring system 400
is sensitive to changing pressures. A correlation with decreased
perfusion was discovered once the pressure approaches diastolic
pressure. The inventive system 400 does not reflect complete
vascular compromise until tourniquet pressure supersedes systolic
blood pressure because of venous congestion. These findings are
consistent with previously described studies.
Statistical Analysis:
[0205] A significant difference is observed once tourniquet
pressure equals the diastolic pressure (Perfusion pressure of
zero). The venous congestion phenomenon which has been described
with the tourniquet model for compartment syndromes maintains some
flow until cuff pressure is raised to above systolic pressure (no
flow). Venous congestion is the phenomenon when the higher systolic
blood pressure is able to overcome the tourniquet pressure applied
to the leg during that burst of pressure created by the heart's
contraction when the tourniquet compression is above diastolic
pressure but below systolic pressure.
[0206] Referring now to FIG. 23, this figure is a graph 2300 of
perfusion pressure plotted against oxygenation levels (O.sub.2) of
the study conducted to determine the sensitivity and responsiveness
of the inventive compartment monitoring system 400. The section
between points A and B show the combined points of all subjects
studied during the study when the tourniquet pressure was below the
diastolic pressure. As shown in the graph, the grouping is mostly
flat and does not show any decrease as the tourniquet pressure is
increased. After point B between point B and C, the tourniquet
pressure is above the diastolic pressure and the perfusion pressure
becomes zero or negative. During this section of the graph, there
is a significant drop in muscle oxygenation. The data points in
FIG. 23 use the actual compartment monitoring values, which as
described above, can vary based on skin pigmentation. Therefore,
there is a wider range of values in oxygenation numbers and a wider
spread of data points. See APPENDIX B for the raw data that
supports this graph 2300.
[0207] Referring now to FIG. 24, this figure is a graph 2400 of
perfusion pressure plotted against a change in the oxygenation
levels (O.sub.2) from a baseline for each subject of the study
conducted to determine the sensitivity and responsiveness of the
inventive compartment monitoring system 400.
[0208] In the FIG. 24, the change from baseline was used instead of
the absolute number presented by the compartment sensor. The
effects of pigment were removed when change from baseline values
was used. Baseline was defined as the value before the tourniquet
was placed. The spread between data points is much less. As shown
again between points A and B, there is a very small and gradual
decrease in tissue oxygenation until point B (moving from high
perfusion pressures to lower perfusion pressures or from right to
left). Once the perfusion pressure, becomes zero or negative, the
change from baseline was much larger and more rapid. Both graphs
show how the tissue oxygenation is highly sensitive to perfusion
pressure and the critical point is when the perfusion pressure
changes from positive to negative. As described above, the
diagnosis of compartment syndrome is based on the perfusion
pressure (diastolic pressure minus compartment pressure).
Therefore, the compartment monitoring system 400 has the capability
to show real-time changes in perfusion prior to any irreversible
tissue damage. See APPENDIX B for the raw data that supports this
graph 2300.
[0209] This study supports the theory that oxygenation levels
measure with the compartment sensors 405 decrease as perfusion
pressure also decreases (Perfusion pressure=diastolic-cuff
pressure). The study also indicates that there are no significant
changes in measured oxygenation levels until there is increase
above the diastolic pressure. The findings of this study as
illustrated in FIGS. 23 and 24 correlate with previous studies
using other determinants of flow (Xenon clearance; Clayton, 1977;
Dahn, 1967; Heppenstall, 1986; Matava, 1994).
Study of Established Acute Compartment Syndromes:
[0210] Based on the clinical evaluation in established acute
compartment syndrome patients the diagnosis of compartment syndrome
was made. Its purpose was to evaluate the ability of the inventive
compartment monitoring system 400 to detect hypoperfusion in the
different compartments of the lower leg. This evaluation was made
to demonstrate the invention's sensitivity to increased pressures
versus uninjured legs.
Hypothesis:
[0211] There will be a significant difference between the injured
and uninjured values of the compartment monitoring system 400.
There will also be an inverse relationship between compartment
pressures and measured oxygenation levels by the sensors 405. In
other words, the oxygenation values would be directly proportional
to perfusion pressures.
Material & Methods:
[0212] Oxygenation levels and pressure measurements for each
compartment in established compartment syndromes were obtained.
Readings for both legs were compared for each compartment.
Unknowns:
[0213] How will thick subcutaneous fat affect the compartment
sensors 405?
[0214] What values will we obtain for the posterior
compartments?
Preliminary Results:
[0215] Hyperemia (increased oxygenation levels) for fractures
without any compartment syndrome symptoms has been demonstrated by
the inventors studies (Table #3 and #4). In early compartment
syndromes, the oxygenation values were equal between the two
different legs. Once the compartment syndrome became advanced, and
the perfusion pressure was decreased or eliminated, the oxygenation
values in the injured leg dropped below the uninjured leg. There
was some difficulty in obtaining oxygenation levels over a
hematoma. Therefore, when oxygenation values between the two legs
become equal, there should be concern for a compartment syndrome
and fasciotomy should be considered. Once the injured levels drop
below the uninjured leg, a fasciotomy should be performed.
[0216] Oxygenation levels are extremely responsive to changes in
perfusion in regards to pressure changes. Compartment sensors 405
can differentiate between compartments. Oxygenation levels can work
and are accurate in intubated patients. Oxygenation levels do
respond over extended time periods and over very short periods of
time and rapid changes in intra-compartmental pressures.
[0217] Oxygenation levels and hyperemia are maintained at least two
to three days post injury or surgery. Post-operative values are
also high in the operated on leg--.about.69-72 (Standard deviation
of 9-12) with an average difference of 15-17%. The compartment
sensors 405 work as a noninvasive tool. Oxygenation levels can be
monitored by sensors 405 over extended periods of time. Compartment
sensors 405 do respond to changes in perfusion both gradual and
sudden. The sensors 405 can differentiate between different
compartments.
TABLE-US-00002 TABLE #2 Comparison of Oxygenation Levels between
Injured Limb and Non-injured Limb Avg Injured Uninjured Diff p
value Anterior 46 54 -6 0.07 Lateral 45 54 -9 0.01 Deep Post 54 68
-14 0.05 Sup Post 50 60 -10 0.04
Significant difference using one tailed, paired student t-test was
used for statistical analysis.
[0218] In three out of four compartments, the p-value showed
statistical significance (p-value<0.05). The one compartment
that was not less than 0.05, the anterior compartment, the p-value
was 0.07 which is very close to 0.05. As described below, the
normal situation should be the opposite. The injured side should be
and is shown to be significantly higher when compared to the
uninjured side. The p-value can be described as the chance that
these findings were due to chance alone. By convention,
statistically significant findings are considered to be less than
5% or a p-value of <0.05 in comparison. This means that there is
a 5% chance that these findings are due to chance alone and that
there is no difference between the two groups. See APPENDIX A for
the raw data that supports this data.
Study of Fracture Hyperemia with Inventive Compartment Monitoring
System 400
[0219] A study of fracture hyperemia with the inventive compartment
monitoring system 400 was made. The purpose of this study was to
examine non compartment syndrome patients with fractures of the
lower leg.
Hypothesis:
[0220] The injured leg will show a hyperemic response to injury and
have elevated blood flow causing an increase in oxygenation
values.
Materials & Methods:
[0221] Compare uninjured leg to injured leg to see if there is a
statistical and reproducible increase at time of injury. The data
is important to describe normal fracture response to compare with
compartment syndrome response.
Results:
[0222] Patients have approximately 15 pts higher on the injured
side compared to the uninjured side. Time of measurement was
approximately 16 hours post injury (range 2, 52).
TABLE-US-00003 TABLE #3 Oxygenation Values for Injured versus
Uninjured Lower Leg Measurements. Avg Injured Uninjured Diff p
value Anterior 69 55 14 <0.0001 Lateral 70 55 15 <0.0001 Deep
Post 74 57 17 <0.0001 Sup Post 70 56 14 <0.0001
N=26 (there were 26 subjects examined in this study.) Statistical
Analysis Calculated p-Values Using a Two Tailed, Paired Student
t-Test.
[0223] In normal lower leg fracture situations without vascular
injury or compartment syndrome, comparison between injured and
uninjured legs show that the injured leg should be significantly
higher with and average elevation of between 14 and 17 points. This
finding is consistent with the hyperemia associated with injury.
This effect is a long lasting effect that lasts over 48 hours after
injury and surgery as seen by these results. The p-value can be
described as the chance that these findings were due to chance
alone. In all four compartments, the chance of finding the
difference (14-17) in average value between the two groups (injured
and uninjured) was less than 0.01% or less than 1 out of 10,000. In
other words the likelihood of these findings occurring by chance
alone is very unlikely. By convention, statistically significant
findings are considered to be less than 5% or a p-value of <0.05
in comparison. See APPENDIX A for the raw data that supports this
data.
TABLE-US-00004 TABLE #4 Oxygenation Values for Injured versus
Uninjured Lower Leg Measurements 2 Days After Surgery. Avg Injured
Uninjured Diff p value Anterior 71 55 16 <0.0001 Lateral 70 54
16 <0.0001 Deep Post 73 58 15 <0.0001 Sup Post 73 56 17
<0.0001
[0224] N=17 (This study included 17 patients)
Average time of measurement was 71 hours after injury and 44 hours
after operation
[0225] The p-value can be described as the chance that these
findings were due to chance alone. In all four compartments, the
chance of finding the difference (15-17) in average value between
the two groups (injured and uninjured) was less than 0.01% or less
than 1 out of 10,000. In other words the likelihood of these
findings occurring by chance alone is very unlikely. By convention,
statistically significant findings are considered to be less than
5% or a p-value of <0.05 in comparison. See APPENDIX A for the
raw data that supports this data.
TABLE-US-00005 TABLE #5 Uninjured Controls Comparing Right and Left
Leg Differences. Avg Right Left Diff Avg Val Anterior 55 54 1 55
Lateral 56 54 2 56 Deep Post 60 58 2 59 Sup Post 59 58 1 58
[0226] N=to 25 (There were 25 patients included in this study.)
No difference was found between right and left sides.
[0227] These findings are important for two different reasons.
First, the difference between the two legs was very small (on
average between 1 or 2 points). Therefore, the other findings that
show significant differences between legs cannot be explained as
normal variance. Uninjured patients have oxygenation values between
the two legs that are typically very similar (within 1-5 points of
each other). Second, normal oxygenation values for uninjured
subjects were in the high 50's. This value varied based on
pigmentation of the skin as showed above. See APPENDIX A for the
raw data that supports this data.
Exemplary Method for Monitoring Oxygenation Levels of a
Compartment
[0228] Referring now to FIG. 25, this figure is logic flow diagram
illustrating an exemplary method 2500 for monitoring oxygenation
levels of a compartment according to one exemplary embodiment of
the invention. The processes and operations of the inventive
compartment monitoring system 400 described below with respect to
the logic flow diagram may include the manipulation of signals by a
processor and the maintenance of these signals within data
structures resident in one or more memory storage devices. For the
purposes of this discussion, a process can be generally conceived
to be a sequence of computer-executed steps leading to a desired
result.
[0229] These steps usually require physical manipulations of
physical quantities. Usually, though not necessarily, these
quantities take the form of electrical, magnetic, or optical
signals capable of being stored, transferred, combined, compared,
or otherwise manipulated. It is convention for those skilled in the
art to refer to representations of these signals as bits, bytes,
words, information, elements, symbols, characters, numbers, points,
data, entries, objects, images, files, or the like. It should be
kept in mind, however, that these and similar terms are associated
with appropriate physical quantities for computer operations, and
that these terms are merely conventional labels applied to physical
quantities that exist within and during operation of the
computer.
[0230] It should also be understood that manipulations within the
computer are often referred to in terms such as listing, creating,
adding, calculating, comparing, moving, receiving, determining,
configuring, identifying, populating, loading, performing,
executing, storing etc. that are often associated with manual
operations performed by a human operator. The operations described
herein can be machine operations performed in conjunction with
various input provided by a human operator or user that interacts
with the computer.
[0231] In addition, it should be understood that the programs,
processes, methods, etc. described herein are not related or
limited to any particular computer or apparatus. Rather, various
types of general purpose machines may be used with the following
process in accordance with the teachings described herein.
[0232] The present invention may comprise a computer program or
hardware or a combination thereof which embodies the functions
described herein and illustrated in the appended flow charts.
However, it should be apparent that there could be many different
ways of implementing the invention in computer programming or
hardware design, and the invention should not be construed as
limited to any one set of computer program instructions.
[0233] Further, a skilled programmer would be able to write such a
computer program or identify the appropriate hardware circuits to
implement the disclosed invention without difficulty based on the
flow charts and associated description in the application text, for
example. Therefore, disclosure of a particular set of program code
instructions or detailed hardware devices is not considered
necessary for an adequate understanding of how to make and use the
invention. The inventive functionality of the claimed computer
implemented processes will be explained in more detail in the
following description.
[0234] Further, certain steps in the processes or process flow
described in the logic flow diagram must naturally precede others
for the present invention to function as described. However, the
present invention is not limited to the order of the steps
described if such order or sequence does not alter the
functionality of the present invention. That is, it is recognized
that some steps may be performed before, after, or in parallel
other steps without departing from the scope and spirit of the
present invention.
[0235] Referring again to FIG. 25, Step 2501 is the first step in
the process 2500 for monitoring oxygenation levels of a compartment
according to one exemplary embodiment of the invention. In step
2501, a compartment sensor 405 may be manufactured from sterile
materials as described above in connection with FIG. 21.
Alternatively, a compartment sensor 405 can be encapsulated with
sterile materials so that it can be used in a surgical environment
or so that it can be place adjacent to wounds (or both).
[0236] In step 2503, a central scan depth marker 415 can be
provided on a compartment sensor 405. In step 2506, an alignment
mechanism 410 can also be provided on the compartment sensor 405 to
allow a medical practitioner to orient a sensor 405 along a
longitudinal axis of a compartment of interest.
[0237] In step 2509, an expansion device 535 may be provided
between two or more grouped compartment sensors 405 as illustrated
in FIG. 5A. In step 2512, the processor and display device 420 may
receive input from a user on the type of compartment that is to be
monitored by the inventive system 400.
[0238] In step 2515 and in response to the input of step 2512, the
display device 420 can display a location of the selected
compartment of interest such as illustrated in FIG. 14D. The
display device 420 can also display the longitudinal axis 450 of
the compartment of interest. Next, in step 2518, the display device
420 may display an ideal or optimal position for the compartment
sensor 405 along the longitudinal axis of the compartment of
interest as illustrated in FIG. 14D.
[0239] In step 2521, with the information from steps 2515-2518, the
medical practitioner can identify a proper position of the
compartment sensor on a patient through orienting the alignment
mechanism 410 with the longitudinal axis of the compartment and by
using the central scan depth marker 415.
[0240] In step 2527, the compartment sensor 405 can be placed on
the patient. In step 2530, the compartment sensor can obtain a skin
pigment value of the patient's skin through using a skin sensor
1820 as illustrated in FIG. 18C or thorough using a shallow sensor
405 as illustrated in FIG. 17. In step 2533, the processor 420A can
determine an oxygenation offset value based on the skin pigment
value obtained in step 2530.
[0241] Next, in step 2536, the offset value from step 2533 can be
used during oxygenation level monitoring. In step 2539, the blood
pressure of the patient can be monitored with a probe 440 and blood
pressure monitor as illustrated in FIGS. 4 and 19. In step 2542,
the system 400 can monitor the oxygenation levels of one or more
compartments of interest over time. In step 2545, the system 400
can also monitor the oxygenation levels of healthy compartments to
obtain a baseline while monitoring the compartments adjacent to an
injury or trauma as illustrated in FIG. 15B.
[0242] In step 2547, the oxygenation levels of compartments of
interest can be displayed on the display device 420 as illustrated
in FIGS. 10, 14C, 15B-C, 16, and 20. In step 2550, the blood
pressure of the patient can also be displayed on the display device
as illustrated in FIG. 20. In step 2553, the display device 420 and
its processor can monitor the relationship between the blood
pressure values and oxygenation levels as illustrated in FIG.
20.
[0243] In step 2556, the display device 420 can activate an alarm
in the form of an audible or visual message (or both), when the
oxygenation levels drop below a predetermined value or if a
significant change in the levels is detected as illustrated in FIG.
20. In step 2559, the display device can also activate an alarm in
the form of an audible or visual message (or both), when both the
oxygenation levels and blood pressure drop simultaneously or if one
of them falls below a predetermined threshold value as described in
connection with FIG. 20.
[0244] In step 2562, the display device 420 and its processor can
increase a frequency of data collection for oxygenation levels and
blood pressure values if both values drop. The exemplary process
then ends.
ALTERNATIVE EXEMPLARY EMBODIMENTS
[0245] The inventive compartment monitoring system 400 could also
be used for free flap as well as tissue transfer monitoring.
Currently skin color and capillary refill are used to evaluate flap
viability. This practice requires repeated examinations and
subjective criteria. The conventional method requires leaving skin
exposed or taking down dressings which can be very labor intensive.
As a solution to the conventional approach, a sensor 405 can be
sterilized and it can record average oxygenation levels over time.
The sensor 405 can be placed on the flap (free or transferred).
[0246] The compartment sensor 405 can also be used to monitor
oxygenation of tissue transferred for vascular patency.
Specifically, for hand or any upper extremity surgery, the
compartment sensor can be used to monitor the progress of
revascularization of fingers, hands and arms based on measured
oxygenation levels. The sensor 405 can be applied to the injured
extremity once vascular repair has been performed in order to
continue monitoring of vascular repair. A baseline of a
corresponding uninjured or healthy extremity can be made once
repair to the injured extremity is done--before closure--in order
to get a baseline value while looking at the repair. Sensors 405
for this application will also need to be sterilized and be able to
conduct scans with depths of at least 0.5 centimeters.
[0247] It should be understood that the foregoing relates only to
illustrate the embodiments of the invention, and that numerous
changes may be made therein without departing from the scope and
spirit of the invention as defined by the following claims.
* * * * *