U.S. patent application number 09/792001 was filed with the patent office on 2002-02-07 for pressure sensitive mat with breathing tube apparatus.
Invention is credited to Fitzgerald, Sanford G., Smith, Toby E..
Application Number | 20020014968 09/792001 |
Document ID | / |
Family ID | 22676806 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014968 |
Kind Code |
A1 |
Fitzgerald, Sanford G. ; et
al. |
February 7, 2002 |
Pressure sensitive mat with breathing tube apparatus
Abstract
This invention relates generally to patient monitoring systems
and more particularly concerns devices and systems used to monitor
bed patients in hospital or other care-giving environments. In
accordance with a first aspect of the instant invention, there is
provided a pressure sensitive mat which has been completely sealed
around its exterior edges. The interior of the mat is kept in
communication with the atmosphere by way of a section of flexible
tubing which encloses the attached electrical line. One end of the
tubing is sealed inside of the mat and the other end is open to the
atmosphere, thereby providing a passageway for air to reach the
interior of the mat. This arrangement, however, protects the
interior of the mat from exposure to fluids near the perimeter of
the mat and allows the mat-portion of the invention to be
completely submersed without adverse effect, if that should become
necessary.
Inventors: |
Fitzgerald, Sanford G.;
(Tulsa, OK) ; Smith, Toby E.; (Broken Arrow,
OK) |
Correspondence
Address: |
Terry L. Watt, Esq.
Suite 800
321 S. Boston Ave.
Tulsa
OK
74103-3318
US
|
Family ID: |
22676806 |
Appl. No.: |
09/792001 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60184424 |
Feb 23, 2000 |
|
|
|
Current U.S.
Class: |
340/573.1 ;
340/540 |
Current CPC
Class: |
H01H 3/141 20130101;
H01H 9/047 20130101; A61B 5/1126 20130101 |
Class at
Publication: |
340/573.1 ;
340/540 |
International
Class: |
G08B 023/00 |
Claims
What is claimed is:
1. A device for use with an electronic patient monitor and for
detecting a presence or an absence of a patient, comprising: (a) a
pressure sensitive binary switch, said binary switch having an
upper member and a lower member being joined together along a
common perimeter, said upper and said lower members together
defining an interior of said binary switch; (b) an electrical line
in electrical communication with said interior of said binary
switch, said electrical line being for the transmission of said
response of said binary switch to said electronic patient monitor,
and, said electrical line penetrating said perimeter of said binary
switch between said upper and lower members; and, (c) a breathing
tube, said breathing tube having a first terminus and a second
terminus, said first terminus being in fluid communication with
said interior of said binary switch and said second terminus being
in fluid communication with the atmosphere, wherein said breathing
tube enters said binary switch between said upper member and said
lower member, and, wherein said perimeter of said binary switch is
substantially sealed except where said breathing tube and said
electrical line enter said interior of said binary switch
2. An apparatus according to claim 1, wherein said pressure
sensitive binary switch is suitable for use on a device selected
from the group consisting of a bed, a chair, and a toilet.
3. An apparatus according to claim 1, wherein said electrical line
contains at least two electrically isolated conductors.
4. An apparatus according to claim 3, wherein said upper member has
a inner conductive surface, and said lower member has an inner
conductive surface, wherein said upper and lower member inner
conductive surfaces are positionable to be proximate to each other,
and, wherein said upper and lower member inner conductive surfaces
are positionable to face each other across said interior of said
binary switch, and, wherein said electrical line has a first
conductor and a second conductor, said first conductor being in
electrical communication with said upper member inner conductive
surface and said second conductor being in electrical
communications with said lower member inner conductive surface.
5. An apparatus according to claim 1, wherein said breathing tube
is proximate to said electrical line where said breathing tube
penetrates said perimeter of said binary switch.
6. An apparatus according to claim 5, wherein said breathing tube
encloses said electrical line.
7. An apparatus according to claim 1, wherein said upper member and
said lower member are substantially planar.
8. An apparatus according to claim 1, wherein said electrical line
and said breathing tube taken together are a multi-lumen cable.
9. A device for detecting a presence or an absence of a patient,
comprising: (a) a pressure sensitive binary switch, said binary
switch having an upper member and a lower member, said binary
switch having an interior and a perimeter, said perimeter being
defined where said upper member and said lower member are joined
together, and said binary switch being responsive to at least two
conditions, (a1) a first condition corresponding to said presence
of the patient on said binary switch, and, (a2) a second condition
corresponding to said absence of the patient from said binary
switch; (b) an electrical line in electrical communication with
said interior of said binary switch, said electrical line passing
into said interior of said binary switch along said perimeter and
between said upper member and said lower member, said electrical
line having an enclosed terminus and a remote terminus, said
enclosed terminus being within said interior of said binary switch
and said remote terminus being outside said binary switch; (c) a
breathing tube, said breathing tube providing a passageway for air
into and out of said interior of said binary switch, said perimeter
of said binary switch being completely sealed except where said
breathing tube and said electrical line penetrates it; and, (d) an
electronic patient monitor, said electronic patient monitor being
in electrical communication with said remote terminus of said
electrical line, said electrical monitor for at least sensing said
first and said second condition of said binary switch and being
responsive thereto.
10. An apparatus according to claim 9, wherein said pressure
sensitive binary switch is suitable for use on a device selected
from the group consisting of a bed, a chair, and a toilet.
11. An apparatus according to claim 9, wherein said electrical line
contains at least two electrically isolated conductors.
12. An apparatus according to claim 11, wherein said upper member
has a inner conductive surface, and said lower member has an inner
conductive surface, wherein said upper and lower member inner
conductive surfaces are positionable to be proximate to each other
within said interior of said binary switch, and, wherein said upper
and lower member inner conductive surfaces are positionable to face
each other across said interior of said binary switch, and, wherein
said electrical line has a first conductor and a second conductor,
said first conductor being in electrical communication with said
upper member inner conductive surface and said second conductor
being in electrical communications with said lower member inner
conductive surface.
13. An apparatus according to claim 9, wherein said breathing tube
is proximate to said electrical line where said electrical line
penetrates said perimeter of said binary switch.
14. An apparatus according to claim 13, wherein said breathing tube
encloses said electrical line.
15. A device for detecting a presence or an absence of a patient,
comprising: (a) a pressure sensitive binary switch having an
interior and a perimeter, said binary switch having an
substantially planar upper member and a substantially planar lower
member, wherein said upper member and said lower member together
define at least a portion of said interior of said binary switch,
at least a portion of a periphery of said upper member and a
periphery of said lower member are joined together, and at least a
portion of said perimeter is formed where said upper member
periphery and said lower member periphery are joined together; (b)
an electrical line in electrical communication with said interior
of said binary switch, said electrical line passing into said
interior of said binary switch along said perimeter between said
upper member and said lower member; and, (c) a breathing tube for
providing a passageway for air into and out of said interior of
said binary switch, said breathing tube having a first terminus and
a second terminus, said first terminus being in fluid communication
with said interior of said binary switch, said second terminus
being in fluid communication with the atmosphere and extending
outwardly beyond said perimeter of said binary switch, said
perimeter of said binary switch being completely sealed except
where said breathing tube and said electrical line penetrates
it.
16. An apparatus according to claim 15, wherein said pressure
sensitive binary switch is suitable for use on a device selected
from the group consisting of a bed, a chair, and a toilet.
17. An apparatus according to claim 15, wherein said electrical
line contains at least two electrically isolated conductors.
18. An apparatus according to claim 15, wherein said upper member
has a inner conductive surface, and said lower member has an inner
conductive surface, wherein said upper and lower member inner
conductive surfaces are positionable to be proximate to each other,
and, wherein said upper and lower member inner conductive surfaces
are positionable to face each other across said interior of said
binary switch, and, wherein said electrical line has a first
conductor and a second conductor, said first conductor being in
electrical communication with said upper member inner conductive
surface and said second conductor being in electrical
communications with said lower member inner conductive surface.
19. An apparatus according to claim 15, wherein said breathing tube
is proximate to said electrical line where said breathing tube
penetrates said perimeter of said binary switch.
20. An apparatus according to claim 19, wherein said breathing tube
encloses said electrical line.
Description
RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 60/184,424 filed Feb. 23, 2000, the
disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates generally to monitoring systems and,
more particularly, concerns pressure-sensitive devices and systems
used to monitor patients in hospital or other care giving
environments.
BACKGROUND OF THE INVENTION
[0003] It is well documented that the elderly and post-surgical
patients are at a heightened risk of falling. There are many
reasons for this but, broadly speaking, these individuals are often
afflicted by gait and balance disorders, weakness, dizziness,
confusion, visual impairment, and postural hypotension (i.e., a
sudden drop in blood pressure that causes dizziness and fainting),
all of which are recognized as potential contributors to a fall.
Additionally, cognitive and functional impairment, and sedating and
psychoactive medications are also well recognized risk factors.
[0004] A fall places the patient at risk of various injuries
including sprains, fractures, and broken bones--injuries which in
some cases can be severe enough to eventually lead to a fatality.
Of course, those most susceptible to falls are often those in the
poorest general health and least likely to recover quickly from
their injuries. In addition to the obvious physiological
consequences of fall-related injuries, there are also a variety of
adverse economic and legal consequences that include the actual
cost of treating the victim and, in some cases, caretaker liability
issues.
[0005] In the past, it has been commonplace to treat patients that
are prone to falling by limiting their mobility through the use of
restraints, the underlying theory being that if the patient is not
free to move about, he or she will not be as likely to fall.
However, research has shown that restraint-based patient treatment
strategies are often more harmful than beneficial and should
generally be avoided--the emphasis today being on the promotion of
mobility rather than immobility. Among the more successful
mobility-based strategies for fall prevention include interventions
to improve patient strength and functional status, reduction of
environmental hazards, and staff identification and monitoring of
high-risk hospital patients and nursing home residents.
[0006] Of course, monitoring high-risk patients, as effective as
that care strategy might appear to be in theory, suffers from the
obvious practical disadvantage of requiring additional staff if the
monitoring is to be in the form of direct observation. Thus, the
trend in patient monitoring has been toward the use of electrical
devices to signal changes in a patient's circumstance to a
caregiver who might be located either nearby or remotely at a
central monitoring facility, such as a nurse's station. The obvious
advantage of an electronic monitoring arrangement is that it frees
the caregiver to pursue other tasks away from the patient.
Additionally, when the monitoring is done at a central facility a
single nurse can monitor multiple patients which can result in
decreased staffing requirements.
[0007] Generally speaking, electronic monitors work by first
sensing an initial status of a patient, and then generating a
signal when that status changes, e.g., he or she has sat up in bed,
left the bed, risen from a chair, etc., any of which situations
could pose a potential cause for concern in the case of an at-risk
patient. Electronic bed and chair monitors typically use a pressure
sensitive switch in combination with a separate
monitor/microprocessor. In a common arrangement, a patient's weight
resting on a pressure sensitive mat (i.e., a "sensing" mat)
completes an electrical circuit, thereby signaling the presence of
the patient to the microprocessor. When the weight is removed from
the pressure sensitive switch, the electrical circuit is
interrupted, which fact is 10 sensed by the microprocessor. The
software logic that drives the monitor is typically programmed to
respond to the now-opened circuit by triggering some sort of
alarm--either electronically (e.g., to the nursing station via a
conventional nurse call system) or audibly (via a built-in
siren).
[0008] General information relating to mats for use in patient
monitoring may be found in patent application 09/285,956 filed Apr.
2, 1999 the disclosure of which is specifically incorporated herein
by reference. Additionally, U.S. Pat. Nos. 4,179,692, 4,295,133,
4,700,180, 5,600,108, 5,633,627, 5,640,145, and 5,654,694
(concerning electronic monitors generally) contain further
information generally pertinent to this same subject matter, as do
U.S. Pat. Nos. 4,484,043, 4,565,910, 5,554,835, and 5,623,760
(switch patents), the disclosures of all of which are all
incorporated herein by reference.
[0009] By way of general background, in a typical arrangement, a
pressure-sensing mat is a sealed "sandwich" composed of three
layers: two outer layers and an inner (central) layer positioned
therebetween. The outer layers are usually made of some sort of
plastic and are impermeable to fluids and electrically
non-conductive on their outer faces, where "outer" is determined
with respect to the middle layer. The inner surface of each of the
outer layers--which inner surfaces are oriented to face each other
from opposite sides of the central layer--is made to be
electrically conductive, usually by printing a conductive (e.g.,
carbon-based) ink on that surface. The compressible middle "central
spacer" is made of a non-conductive material and serves to keep the
two conductive faces apart when a patient is not present on the
sensor. The central spacer is discontinuous, which makes it
possible for the two conductive inner surfaces to be forced into
contact through the discontinuities when weight is applied to the
switch. By attaching a separate electrical lead to each of the
conductive inner faces, it can readily be determined (e.g., via a
simple continuity check) whether a weight is present on the sensor
(e.g., whether a patient is seated thereon). Removal of the weight
causes the central spacer to expand and press apart the two
conducting faces, thereby breaking the electrical connection
between them. Thus, a device that monitors the resistance across
the two electrical leads may determine when a patient has risen to
his or her feet.
[0010] One disadvantage of the current generation of pressure
sensitive mats is that they cannot be completely (e.g.,
hermetically) sealed against the external environment. The reason
for this should be clear: if the interior of the mat were
completely sealed, air pressure inside of the mat would tend to
oppose the urging of the mat faces into contact, thereby making it
difficult or impossible to complete the circuit (e.g., think of
compressing an "air pillow"). Thus, it is customary to
intentionally leave gaps in the seal between the two halves of the
mat which allow for movement of air into and out of the switch.
[0011] Another disadvantage of the prior art is that partial
sealing of the perimeter of the mat can cause it to resist
expansion after weight is removed therefrom. That is, when a
patient places weight on a conventional mat, air is slowly expelled
from the mat interior, typically through a small opening in the
perimeter of the mat. However, when the patient rises the opening
in the mat can collapse or narrow in response to air pressure on
the now-deflated mat body, thereby retarding the process of
reinflating it. As a consequence, the mat may continue to signal
that the patient is still present on the mat for a time after he or
she has risen.
[0012] Of course, the fact that the interior of the mat must kept
open to the atmosphere results in a mat that is highly susceptible
to invasion by bodily fluids or cleaning solutions, as the
in-rushing air tends to carry fluids along with it into the
interior of the mat. Further, it is well known that some common
disinfecting cleaners can loosen the adhesives that hold the layers
of the mat together, thereby ruining the sensor. Thus, cleaning
soiled mats that have air passages placed therein becomes
problematic. In summary, what is needed is a pressure sensitive mat
that is more resistant to invasion by fluids than is presently
available.
[0013] Heretofore, as is well known in the patient monitoring arts,
there has been a need for an invention to address and solve the
above-described problems. Accordingly, it should now be recognized,
as was recognized by the present inventors, that there exists, and
has existed for some time, a very real need for pressure sensitive
mat and monitoring system that would address and solve the
above-described problems.
[0014] Before proceeding to a description of the present invention,
however, it should be noted and remembered that the description of
the invention which follows, together with the accompanying
drawings, should not be construed as limiting the invention to the
examples (or preferred embodiments) shown and described. This is so
because those skilled in the art to which the invention pertains
will be able to devise other forms of this invention within the
ambit of the appended claims.
SUMMARY OF THE INVENTION
[0015] In accordance with a first aspect of the instant invention,
there is provided a pressure sensitive mat which has preferably
been completely sealed around its exterior edges except where a
breathing tube passes therethrough. The interior of the mat is kept
in communication with the atmosphere by way of a section of
flexible tubing which encloses the attached electrical line. One
end of the tubing is sealed inside of the mat and the other end is
open to the atmosphere, thereby providing a passageway for air to
reach the interior of the mat. This arrangement, however, protects
the interior of the mat from exposure to fluids that might be
present near its perimeter. In fact, this innovation allows the
mat-portion of the invention to be completely submersed without
adverse effect, if that should be come necessary.
[0016] According to another aspect of the instant invention, there
is provided a pressure sensitive mat and breathing tube combination
wherein the wires that transmit status information from the
interior of the mat to a separate electronic monitor are not inside
of the breathing tube, but instead are adjacent to it through at
least part of their length. One example of such an arrangement
would be found in a multi-lumen tube of the sort that are well
known to those skilled in the medical arts, wherein the electrical
wires are preferably placed in one tube (or lumen), with one or
more other tubes being kept clear to permit the passage of air
therethrough.
[0017] Finally, according to still another aspect of the instant
invention, there is provided a pressure sensitive mat and breathing
tube combination, wherein the breathing tube is completely
separated from the electrical wires and separately penetrates the
mat perimeter to reach its interior.
[0018] The foregoing has outlined in broad terms the more important
features of the invention disclosed herein so that the detailed
description that follows may be more clearly understood, and so
that the contribution of the instant inventor to the art may be
better appreciated. Although the instant invention will be
described in connection with a preferred embodiment, it is to be
understood that it is not intended to limit the invention to that
embodiment. That is, the instant invention is not to be limited in
its application to the details of the construction and to the
arrangements of the components set forth in the following
description or illustrated in the drawings. Rather, the invention
is capable of other embodiments and of being practiced and carried
out in various other ways not specifically enumerated herein.
Further, it should be understood that the phraseology and
terminology employed herein are for the purpose of description and
should not be regarded as limiting, unless the specification
specifically so limits the invention. Finally, the disclosure that
follows is intended to apply to all alternatives, modifications and
equivalents as may be included within the spirit and scope of the
invention as defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Other objects and advantages of the invention will become
apparent upon reading the following detailed description and upon
reference to the drawings in which:
[0020] FIG. 1 illustrates the general environment of the
invention.
[0021] FIG. 2 contains a schematic illustration of a convention
pressure sensitive mat.
[0022] FIG. 3 contains a cross-sectional view of a pressure
sensitive mat.
[0023] FIG. 4 illustrates a preferred embodiment of the instant
invention.
[0024] FIG. 5 contains a cross-sectional view of a preferred
connecting tube arrangement of the instant invention, wherein the
tube encloses the electrical wire.
[0025] FIGS. 6A and 6B illustrate cross sections of another
wire/tube configuration, wherein the electrical wire and tube are
run roughly in parallel.
[0026] FIG. 7 contains a plan view of another preferred embodiment,
wherein the electrical wire and breathing tube are run roughly in
parallel.
[0027] FIG. 8 illustrates another preferred arrangement, wherein
the electrical wire and breathing tube enter the mat in different
locations.
DETAILED DESCRIPTION OF THE INVENTION
General Background
[0028] Turning first to FIG. 1 wherein the general environment of
the instant invention is illustrated, in a typical arrangement a
sensing mat 100 is placed on a hospital bed 20 where it will lie
beneath a weight-bearing portion of the reclining patient's body,
usually the buttocks and/or shoulders. It should be noted at the
outset, however, that although the language that follows is largely
confined to illustrations involving bed-type sensors, the range of
application of the instant invention is much broader and could
include chair sensors, potty sensors, and any other type of
pressure-sensitive switch that is used in a patient monitoring
environment where invasion by fluids is a concern.
[0029] Generally speaking, the mat 100/monitor 50 combination works
as follows. When a patient is placed atop the mat 100, the
patient's weight compresses the mat 100 and closes an electrical
circuit, which closure is sensed by the attached electronic patient
monitor 50 through electrical line 10 and connector 40 (FIG. 2).
When the patient attempts to leave the bed, weight is removed from
the sensing mat 100, thereby breaking the electrical circuit. The
patient monitor 50 senses the change in electrical continuity and
signals the caregiver per its pre-programmed instructions. Note
that additional electronic connections not pictured in this figure
might include a monitor 50 to nurse-call-station connection, a
monitor 50 to computer connection, and an A/C power cord--although
the monitor 50 can certainly be configured to be battery
operated.
[0030] FIG. 2 contains a schematic drawing of a prior art pressure
sensitive patient mat. As is indicated in that figure, a typical
pressure sensitive mat 100 includes upper and lower non-conductive
outer members 220 and 240 (FIG. 3), respectively, which serve to
protect the interior from contact with the environment. These
members are usually made of a flexible impermeable electrically
non-conductive material such as plastic, with polyester being the
preferred material. These two members are separated by an internal
non-conductive spacer 260, which has at least one aperture
therethrough 250. In FIG. 2, the central spacer 260 is shown in
phantom because it is hidden from view within the assembled
product.
[0031] As is further indicated in FIG. 3, the typical pressure
sensitive switch is a "sandwich" type arrangement with the two
outer members surrounding the inner non-conductive spacer 260. The
perimeters of the upper 220 and lower 240 members are
conventionally sealed together by a heat activated adhesive (such
as polyethylene) or by some form of pressure sensitive
adhesive.
[0032] Affixed to the inner surface of each of the outer members
220 and 240 is a conductive layer (320 and 340, respectively)
which, for safety purposes, preferably does not extend to the edges
of the mat. As should be clear, pressure on the mat 100 tends to
urge the conductive faces 320 and 340 into contact through aperture
250, thereby completing an electrical circuit. When pressure is
released, the central spacer 260, which is preferably constructed
of a compressible and resilient material, expands and pushes the
conductive layers apart. As is suggested in FIG. 2, when the
electrical line 10 enters the mat it is typically separated into
two electrically isolated elements, one of which is placed in
electrical communication with the conductive layer 320 atop of the
spacer 260 and the other which is placed in electrical
communication with the conductive layer 340 underneath the
spacer.
[0033] As is generally illustrated in FIG. 3, the central spacer
260 usually fits loosely within an envelope formed by the two outer
layers 220 and 240. This arrangement allows air to move freely
throughout the interior of the mat 100. Fluid communication between
the interior of the mat and the atmosphere is typically provided in
the form of one or more breaches in the seal between the upper 220
and lower 240 members. These breaches are created during the
manufacturing process and provide a means for the mat 100 to
"breathe" when compressed. A first natural breach occurs at the
point where electrical line 10 enters the mat between the upper 220
and lower 240 mat members. Typically, the mat material fits loosely
around the electrical line 10, thereby providing a ready passageway
for air (and fluids) to enter and exit the mat. Where more airways
are needed, it is possible to create gaps between the outer members
along their common perimeter. One way of doing this involves
placing a piece of monofiliment line between the upper 220 and 240
members before they are sealed. After the two members have been
sealed together, the line is withdrawn, leaving behind a small gap
230 in the seal between the layers.
Preferred Mat Embodiments
[0034] A first preferred embodiment of the instant mat is
illustrated in FIG. 4, which contains a plan view of the device. As
is illustrated there, the mat portion of the sensor 400 is
configured in a "sandwich" arrangement as has been described above.
However, the instant embodiment differs from the prior art in that
it contains a separate open-ended "breathing tube" 420 which
loosely encloses the electrical line 10. This tube 420 enters the
mat between the upper 220 and lower 240 members. The upper 220 and
lower 240 members may now be completely sealed along their
perimeters, including where the tube 420/electrical line 10
combination enters the mat 400. When pressure is applied to the mat
400, the air inside of the mat 400 is pushed toward and out of the
breathing tube 420, thereby allowing the mat 400 to compress.
Similarly, when pressure is removed, air returns from the
atmosphere to the interior of the mat 400 via the same conduit,
thereby allowing the mat 400 to quickly expand to its un-weighted
configuration which separates the upper 220 and lower 240
members.
[0035] FIG. 5 illustrates a preferred embodiment of the breathing
tube 420 in cross section. As can be seen in this figure, tube 420
is sized so that the electrical line 10 fits loosely therein,
thereby providing at least a partially unobstructed air passageway.
The breathing tube 420 is preferably round or oval, although
obviously the precise shape of the tube 420 is unimportant, so long
as an air-tight seal may be created around the perimeter of the
tube 420 where it enters the mat 400 between the two outer mat
members. Within electrical line 10 will typically be found two or
more electrically isolated conductors 510, with the use of a
four-conductor wire being a common arrangement. It should be
apparent that the number of electrical conductors 510 that might be
found within the electrical line 10 is unimportant to the practice
of the instant invention. As has been described previously, it is
customary to use two of these conductors 510 to establish separate
electrical communications between the monitor 50 and the upper 320
and lower 340 conducting members inside of the mat.
[0036] In operation, the sensing portion of the instant invention
400 may be completely submerged without risk of fluid invasion, so
long as the outer terminus of the breathing tube 420 (i.e., the end
nearest the connector 40) is kept clear of the fluid. Further, the
instant mat 400 may be fully compressed and then released while
held under water without risk of drawing fluid into its interior,
provided that the perimeter has been completely sealed. Finally, in
a patient monitoring situation where there has been a release of
fluid into the bed or chair, the mat 400 can be cleaned and reused
without endangering its structural integrity.
[0037] FIG. 7 contains another preferred arrangement. In this
variation, the tube 420 and electrical wire 10 run roughly in
parallel into the mat 700. A cross sectional view of this
arrangement may be found in FIGS. 6A and 6B, these two figures
differing only in the size of the breathing tubes 420 and 620
attached thereto. This configuration of breathing tube/electrical
conductors 510 is sometimes referred to as a "multi-lumen" cable by
those skilled in the art. Of course, the diameter of the breathing
tube 420 is unimportant to the operation of the instant invention,
except that it should be large enough to convey sufficient air into
and out of the interior of the mat 700 to allow it to be readily
compressed and then expanded again. The best tube 420 diameter will
ultimately depend on the specifics of the mat to which it is
attached and will need to be determined empirically for each type
of mat.
[0038] FIG. 8 contains still another variation, wherein the
electrical line 10 and the breathing tube 420 enter the mat 800
independently. As should be clear from this figure, this
arrangement suffers from the disadvantage that two different
breaches of the mat perimeter would need to be sealed. However,
having the electrical line 10 and breathing tube 420 separated
might be advantageous in some circumstances.
[0039] Finally, it should be noted and remembered that although it
is preferable that the mat be completely sealed along its perimeter
except where the breathing tube penetrates it, that is not strictly
required. The breathing tube acts to assist in reinflation of the
any sort of mat when weight is removed therefrom, so it would also
be useful with a conventional mat which is not hermetically sealed.
However, if the mat is not completely sealed along its perimeter
there is a risk that fluid will enter the interior of the mat
through those breaches, as has been a problem in the past.
[0040] Clearly, many variations of this and the previous
arrangements are possible and have been specifically contemplated
by the instant inventor.
[0041] Conclusions
[0042] Although the preceding text has occasionally referred to the
sensor of the instant invention as a "bed" mat that was done for
purposes of specificity only and not out of any intention to limit
the instant invention to that one application. In fact, the
potential range of uses of this invention is much broader than
bed-monitoring alone and might include, for example, use with a
chair monitor, urinal monitor, or other pressure sensitive patient
monitor application which is configurable as a binary switch, a
binary switch being one that is capable of sensing at least two
conditions and responding to same via distinct electronic signals.
In the preferred embodiment, those two conditions would be the
presence of weight on the switch. Additionally, it should be noted
that the use of the term "binary" is not intended to limit the
instant invention to use only with sensors that can send only two
signal types. Instead, binary switch will be used herein in its
broadest sense to refer to any sort of sensor that can be utilized
to sense the condition or location of a patient, even if that
sensor can generate a multitude of different signals.
[0043] Thus, it is apparent that there has been provided, in
accordance with the invention, a patient sensor and method of
operation of the sensor that fully satisfies the objects, aims and
advantages set forth above. While the invention has been described
in conjunction with specific embodiments thereof, it is evident
that many alternatives, modifications and variations will be
apparent to those skilled in the art and in light of the foregoing
description. Accordingly, it is intended to embrace all such
alternatives, modifications and variations as fall within the
spirit of the appended claims.
* * * * *