U.S. patent application number 12/694256 was filed with the patent office on 2011-01-06 for method and system for integrating a passive sensor array with a mattress for patient monitoring.
This patent application is currently assigned to HOANA MEDICAL, INC.. Invention is credited to Scott A. Christensen, Jason M. Gentry, Matthew S. Glei.
Application Number | 20110001622 12/694256 |
Document ID | / |
Family ID | 34886275 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110001622 |
Kind Code |
A1 |
Gentry; Jason M. ; et
al. |
January 6, 2011 |
METHOD AND SYSTEM FOR INTEGRATING A PASSIVE SENSOR ARRAY WITH A
MATTRESS FOR PATIENT MONITORING
Abstract
A system is provided for integrating a passive sensor or sensor
array into a patient's mattress to support continuous passive
monitoring of a patients' physiological conditions in a hospital
setting. The sensor or sensor array may be incorporated into the
mattress by fixing it to a coverlet that surrounds the mattress, or
by embedding it within the mattress core. Alternatively, the sensor
or sensor array may be fixed to an underlayer positioned between
the mattress core and the coverlet.
Inventors: |
Gentry; Jason M.; (Berkeley,
CA) ; Glei; Matthew S.; (Honolulu, HI) ;
Christensen; Scott A.; (Danville, CA) |
Correspondence
Address: |
FULWIDER PATTON LLP
HOWARD HUGHES CENTER, 6060 CENTER DRIVE, TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Assignee: |
HOANA MEDICAL, INC.
Honolulu
HI
|
Family ID: |
34886275 |
Appl. No.: |
12/694256 |
Filed: |
January 26, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11061213 |
Feb 18, 2005 |
7652581 |
|
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12694256 |
|
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60546695 |
Feb 18, 2004 |
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Current U.S.
Class: |
340/573.1 |
Current CPC
Class: |
G08B 21/0461 20130101;
A61B 5/021 20130101; A61B 5/11 20130101; A61B 5/1102 20130101; A61B
2562/0247 20130101; A61B 5/1127 20130101; A61B 5/6892 20130101;
A61B 5/113 20130101; A61B 5/6887 20130101; A61B 2562/046 20130101;
A61B 2562/043 20130101; A61B 5/02444 20130101 |
Class at
Publication: |
340/573.1 |
International
Class: |
G08B 23/00 20060101
G08B023/00 |
Claims
1. A system for integrating a passive sensor into a bed to support
continuous passive monitoring of a patient, comprising: a passive
sensor for monitoring a patient; a mattress core; and a coverlet
configured to surround the mattress core; wherein the sensor is
attached to the coverlet.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of, and claims priority
to, U.S. application Ser. No. 11/061,213, filed Feb. 18, 2005,
which claims the benefit of U.S. Provisional Application No.
60/546,695, filed Feb. 18, 2004, the contents of which are
incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to medical monitors
and more specifically to a medical monitoring system for providing
an invisible "safety net" for a patient that will observe and
analyze the physiological parameters of a patient, and, in the
event of a clinically significant negative condition, notify and
report the event to the care staff utilizing the existing nurse
call system of a hospital. Specifically the invention is directed
to methods and systems for integrating a passive sensor array for
such a system into a medical mattress used by a patient.
[0004] 2. General Background and State of the Art
[0005] Monitoring patients is an important aspect of patient care
in many different settings. In a general care floor or ward of a
hospital, for example, monitoring vital physiological signs such as
respiratory rate, heart rate and blood pressure is a basic
component of patient care. Monitoring the presence or absence of a
patient in a hospital bed and monitoring patient movement on that
bed may also be beneficial in a general care ward or other areas of
a hospital. If certain patients leave their beds, they run a risk
of falling and/or injuring themselves. If a patient stops moving in
bed, it may mean that the patient is dying, is in a coma or is
suffering from a medical complication that makes movement difficult
or impossible and requires attention. Excessive movement may
indicate a seizure or other condition.
[0006] Current systems for patient monitoring do not generally
provide for convenient, constant, around-the-clock monitoring. On a
general care ward of a hospital, for example, monitoring typically
consists of a team of nurses circulating from patient to patient,
at three- or four-hour intervals, to take vital signs such as
respiratory rate and heart rate. In some hospitals, this monitoring
may be augmented by one or more devices, such as a bedside
pulse-oximeter, which monitors pulse and oxygen saturation via a
small clamp-like device attached to a patient's finger. The
pulse-oximeter may be designed to sound an alarm, if a certain
pulse or oxygen threshold level is reached.
[0007] The currently available systems and methods for patient
monitoring have several characteristics in common. Virtually all
require a patient to be physically connected to a monitor
apparatus. Many, such as automatic blood pressure cuffs, provide
only for intermittent monitoring. Physical connection to monitoring
apparatus can be cumbersome and inconvenient for patients,
sometimes leading to patient noncompliance, such as when a patient
removes a device due to discomfort. Attached devices may also
loosen, change position, fall partially off the patient and the
like, leading to inaccurate monitoring data. Intermittent
monitoring can lead to missed or late diagnosis and adverse patient
outcomes, especially in very sick patients whose conditions may
change rapidly.
[0008] Currently available systems generally do not monitor patient
movement or positioning. As described above, patient movement can
be an essential monitoring tool. For example, complete absence of
patient movement on a bed could indicate that the patient has left
the bed. Relatively slight movement, a significant reduction in
movement or the like could indicate that the patient is
sufficiently still that some medical problem might have occurred.
Significant increases in patient movement might indicate a seizure
or significant patient discomfort.
[0009] Thus, efforts have been made to develop passive monitoring
systems with sensors that are effectively "invisible" to the
patient, i.e., hidden within the bedding or in the bed clothes used
by a patient, where they may passively monitor the patient's
physiological conditions and movement without the patient or
hospital staff being aware of their presence. However, one of the
challenges is how to mount the sensor to the bed in a way that does
not degrade the properties of the original mattress or sleep
surface, that is thin and comfortable for the patient, that is held
securely in place on the mattress, does not crumple, fold, crease
or bunch up, is cleanable using typical disinfecting agents used on
healthcare mattresses, does not significantly attenuate or degrade
the passive sensor electronic signal, fits mattresses of different
manufacturers, sizes and materials, and does not affect the typical
hospital workflow in making or changing the bedding.
[0010] The present invention addresses these needs.
SUMMARY OF THE INVENTION
[0011] Briefly, in general terms, the present invention provides a
new and improved method and system for integrating a passive sensor
or sensor array into a patient's mattress to support continuous
passive monitoring of a patients' physiological conditions in a
hospital setting. "Passive monitoring" generally refers to the fact
that monitoring according to the invention does not require direct
attachment of a device to a patient. Rather, a patient is coupled
with a sensor device by simply allowing the patient lie, or sit, on
the surface of a hospital bed.
[0012] In particular, the present invention provides a thin
comfortable sensor pad or carrier sheet which can be securely
integrated with the mattress assembly of a patient's hospital bed,
and which will maintain the desirable properties of the patient's
mattress assembly while allowing hospital personnel to change the
bedding or clean the mattress without undue interference.
[0013] The pad or carrier sheet of the present invention can be
mounted to the top or bottom side of the mattress assembly, as
desired. It can be integrated within a mattress coverlet that fits
over the original coverlet, or alternatively, can be used to
replace the existing coverlet. It can be integrated into a
replacement, additional, or existing underlayer disposed between
the coverlet and the mattress assembly core. It also can be placed
into the existing mattress assembly core, or integrated into a new
replacement core.
[0014] In a preferred embodiment, the sensor device of the present
invention includes an array of piezoelectric sensing elements
and/or pressure switches mounted in a flat pad or carrier sheet,
positioned on or within the mattress assembly of a hospital bed
integrated with the sleep surface. In that location, the sensor is
capable of monitoring the patient through one or more layers of
bedding or patient clothing, or the like. The sensor is typically
coupled to a processor, either by wired or wireless communication.
The processor receives sensed data from the sensors and processes
that sensed data into a form that is usable by a physician, nurse
or other user. Any suitable patient parameter may be monitored,
such as but not limited to patient movement, patient position,
respiratory rate, heart rate, blood pressure and/or the like.
[0015] The sensor pad or carrier sheet may include any suitable
number of sensors. Specifically, any number, pattern, size, shape
or type of sensors is contemplated. Where more than two sensors are
included in the sensor device, any combination of sensors may be
used to sense signals and any combination of signals from various
sensors may be compared to provide patient data to a user.
[0016] The piezoelectric sensors may be fabricated from any
suitable material. However, in a preferred embodiment, the sensors
are made of polyvinylidene fluoride film or other polarized polymer
film with piezoelectric properties.
[0017] In some embodiments, the sensors may be embedded in a layer
of resilient foam in the form of a pad suitable for enabling
monitoring of a patient. In a preferred embodiment, the sensor
array is mounted on the surface of a thin carrier sheet. The
surface of the pad or carrier sheet may have any suitable
dimensions. Preferably, the dimensions are sufficient to allow the
pad or carrier sheet, and thus the sensor array, to extend across a
substantial portion of the mattress surface between the patient's
shoulder and buttocks.
[0018] Optionally, the sensor pad or carrier sheet may further
include a protective layer disposed between the surface of the pad
and the patient. Typically, such a protective layer will be water
resistant.
[0019] Other features and advantages will become apparent from the
following detailed description, taken in conjunction with the
accompanying drawings, which illustrate, by way of example, the
features of the present invention.
DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic view of a system for passive patient
monitoring, showing the relationship between an array of sensors,
an anchor box, a processor, and a display device.
[0021] FIG. 2 is a partial cutaway plan view of an array of sensors
forming a pad suitable for use as part of a passive patient
monitoring system in accordance with the present invention.
[0022] FIG. 2A is a top view of an alternative embodiment of the
sensor array shown in FIG. 2.
[0023] FIG. 3 is a cross-sectional view taken substantially through
line 3-3 of FIG. 2.
[0024] FIG. 3A is a cross-sectional view taken substantially
through line 3A-3A of FIG. 2A.
[0025] FIG. 4 is an exploded perspective view of a mattress
assembly, showing the sensor pad of FIG. 2 or 2A, reduced in size,
being attached directly to the outer surface of the mattress.
[0026] FIG. 5 is a perspective view of a mattress assembly, showing
another method of attaching the sensor pad of FIG. 4 to the surface
of the mattress, using wide straps.
[0027] FIG. 6 is a perspective view of a mattress assembly, showing
yet another method of attaching the sensor pad of FIG. 4 to the
surface of the mattress, using narrow straps.
[0028] FIG. 7 is a perspective view of a mattress assembly, showing
still another method of attaching the sensor pad of FIG. 4 to the
surface of the mattress, using webs.
[0029] FIG. 8 is a perspective view of a mattress assembly, showing
still another method of attaching the sensor pad of FIG. 4 to the
surface of the mattress, using a membrane.
[0030] FIG. 9 is a perspective view of a mattress assembly, showing
yet another method of attaching the sensor pad of FIG. 4 to the
surface of the mattress, using an envelope or pocket.
[0031] FIG. 10 is a perspective view of a mattress assembly,
showing a method of enclosing the mattress core in a coverlet which
has the sensor pad of FIG. 4 embedded therein.
[0032] FIG. 11 is a perspective view of a mattress assembly,
showing an alternative method of enclosing the mattress core in a
coverlet which has the sensor pad of FIG. 4 embedded therein.
[0033] FIG. 12 is a perspective view of a mattress assembly,
showing a further alternative method of enclosing the mattress core
in a coverlet which has the sensor pad of FIG. 4 embedded
therein.
[0034] FIG. 13 is a perspective view of a mattress assembly,
showing yet a further alternative method of enclosing the mattress
core in a coverlet which has the sensor pad of FIG. 4 embedded
therein.
[0035] FIG. 14 is a perspective view of a mattress assembly,
showing the sensor pad of FIG. 4 embedded between layers of the
mattress core.
[0036] FIG. 15 is an exploded perspective view of a mattress
assembly, showing the sensor pad of FIG. 4 placed within a cavity
in the mattress core formed by removing a block of mattress core
material.
[0037] FIG. 16 is a perspective view of a mattress assembly,
showing the sensor pad of FIG. 4 attached to the surface of the
mattress core by anchors.
[0038] FIG. 17 is a fragmentary sectional view, taken substantially
along line 17-17 of FIG. 16.
[0039] FIG. 18 is a perspective view of a mattress assembly,
showing a mattress core encased in a coverlet with an underlayer
placed between the coverlet and the mattress core and the sensor
array of FIG. 4 embedded in the underlayer, with portions of the
mattress assembly separated to show the construction thereof.
[0040] FIG. 19 is a sectional view through the mattress assembly of
FIG. 18, substantially along line 19-19, when the mattress core is
fully enclosed by the coverlet.
[0041] FIG. 20 is a perspective view of a mattress assembly,
showing the relative positions of a sensor array and an anchor box
attached to a coverlet.
[0042] FIG. 21 is a sectional view of an anchor box attached to a
coverlet.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] As shown in the drawings, which are provided for purposes of
exemplary illustration, the invention is embodied in a variety of
methods for mounting or integrating a passive sensor array, to be
used for medical monitoring, onto or into a mattress assembly in a
hospital or other healthcare facility.
[0044] Referring more specifically to FIG. 1, there is shown a
generalized system 20 for passive patient monitoring including a
sensor device 21 having at least two piezoelectric sensors 23,
coupled with a processor 24, which is in turn coupled with a data
display device 25 for providing physiological data to a user.
Generally, the sensor device 21 may be coupled with the processor
24 via any suitable connector 26 (or multiple connectors), such as
a cable, wire, wireless transmitter or the like. Similarly, any
suitable connector 26 may be used for coupling the processor 24
with the data display device 25. In a preferred embodiment, the
sensor device 21 may be coupled to the processor 24 through an
anchor box 27 which houses signal conditioning or other electronic
circuitry such as a wireless link. The processor also may be
coupled to the existing nurse call system (not shown) of a hospital
by any suitable connection. In a preferred embodiment, the
processor 24 and display device 25 may be integrated into a single
bedside unit.
[0045] A piezoelectric sensor generally acts as a strain gauge to
measure changes in stress in the sensor. Detected stress changes
may then be converted to electronic data useful for patient
monitoring. A plurality of such sensors may be included in an
array. The sensor array is placed under a patient, and, upon the
application of a varying force due to movement of the patient's
body, the piezoelectric sensors produce a small electrical voltage
indicative of the varying applied force. When in use, each sensor
element in the array may independently measure forces from the
patient's body caused by the cardiac cycle, the respiratory cycle,
and other physical movements and provide a representative voltage
signal. Analysis is performed on these signals using digital
processing techniques to separate the signals of interest from
other physiological signals and noise. These types of sensors are
advantageous when used in an array, because they can sense the
signals of interest from the patient as long as the patient's body
has some contact with the sensor array area. Sensing is not
dependent upon specific placement of sensors in active areas to
sense particular body functions.
[0046] Preferably, each piezoelectric sensor in the array is a thin
film made of polyvinylidene fluoride (PVDF) polymer that is
polarized during its original manufacture by a very strong electric
field. After polarization, the molecular structures stay in
alignment so that, when force is applied to the structure, a
voltage difference between the top surface and the bottom surface
is created. Silver ink or metal foils typically are applied to the
top and bottom surfaces of the sensor element to allow detection of
this voltage.
[0047] For a full description of the pressure sensing capabilities
of piezoelectric films, their use for sensing patient parameters,
and methods of processing the signals from these films to generate
cardiac, respiratory or other signals of a patient, reference may
be had to a co-pending application commonly assigned to the
assignee of the present invention, Hoana Medical, Inc., namely,
U.S. patent application Ser. No. 10/301,524 entitled "Devices and
Methods for Passive Patient Monitoring," filed Nov. 20, 2002, (now
published as U.S. Patent Publication No. 20040111045 on Jun. 10,
2004) the full disclosure of which is hereby incorporated by
reference.
[0048] As previously noted, the sensor array 21 is designed to be
attached to the patient's bed, under the bottom sheet, and not in
direct contact with the patient's skin. The array is electronically
connected or coupled to the bedside processor unit 24, which in
turn, is coupled to a display and to an existing hospital nurse
call system (not shown). Within the bedside unit 24 is a signal
processor and an alarm processor that together measure the data
from the sensor array and evaluate whether a clinically-significant
event is occurring. The bedside unit may be a wall-mounted unit
with a data display 25 that is activated when an alarm condition is
enabled or on command by a nurse. The processor unit 24 may have a
number of dedicated and softkey buttons and controls for entering
information, setting up specific items and interacting with the
system. The nurse call feature includes hardware, software and
cabling to connect to a nurse call system already installed in the
hospital or care facility. The signal processor 24 includes
hardware and software that accepts, buffers and converts the sensor
array 21 signal from analog to digital format for subsequent
processing. The alarm processor uses logic functions to monitor the
patient's parameter trends and determine when a negative condition
is occurring. It then actuates the alarm circuitry for local and/or
remote alarm.
[0049] In one embodiment, the processor activates an alarm if the
comparison of the digital signals suggests that the patient is not
moving on the surface, the patient is not in contact with the
surface, or the patient is moving excessively on the surface. In
another embodiment, the processor activates an alarm if a
respiratory rate of the patient falls below a minimum respiratory
rate or rises above a maximum respiratory rate. In yet another
embodiment, the processor activates an alarm if a heart rate of the
patient falls below a minimum heart rate or rises above a maximum
heart rate. In other embodiments, an alarm may be activated if any
combination of the above occurs. Some embodiments sound an alarm if
a negative trend occurs, such as a negative heart rate trend,
respiratory rate trend, patient movement or other trend or
combination of trends. In some embodiments, the processor further
provides the patient data in the form of a patient respiratory
rate, heart rate or both. Preferably, the alarm is activated
locally and over the existing nurse call system within the
hospital.
[0050] The plurality of piezoelectric films 23 in the sensor array
21 may assume any configuration or number, individually, and in
relation to each other. For example, as exemplified in FIGS. 2-3,
the sensor array 21 may include an array of at least eight
piezoelectric sensor elements 23 arranged adjacent and parallel to
each other in a vertical column. In this example, each sensor
element is paper thin, or thinner, and forms a thin flat elongate
rectangular strip approximately twenty four inches by three
quarters of an inch. Each sensor element also includes a set of
terminals 29 which are connected to a suitable connector 26 that
communicates the sensor signal to the bedside unit 24 (FIG. 1). In
one embodiment, each sensor element 23 and the entire sensor array
21 may be protected, on both top and bottom surfaces, by soft foam
padding 30 such as neoprene for patient comfort. (FIG. 3)
Surrounding the soft padding and enclosing the entire array, is an
external moisture barrier 31 which provides an impervious outer
surface protecting the sensors in the array from fluids or other
contaminants and also providing an additional electrical isolation.
The overall thickness of the sensor pad array is typically between
1 mm-7 mm, and preferably less than 5 mm thick, and forms a
flexible, thin rectangular pad of approximately thirty two inches
by twenty four inches, large enough to span almost the entire width
of the bed, and to extend across the patient's torso from shoulders
to buttocks. If desired, additional sensors or sensor arrays can be
positioned in the bed under the patient's legs for monitoring bed
elopement and leg movement.
[0051] Alternatively, as exemplified in FIG. 2A-3A, each sensor
element 23 in the array may be connected directly to the surface of
a carrier sheet 33 by suitable adhesive or bonding material, to
provide a significantly thinner sensor device that will less
readily be detected by the patient. For example, a sensor array
mounted on the surface of a urethane carrier sheet by adhesive may
be less than 1 mm, and preferably less than 200 .mu.m, thick.
[0052] It will be appreciated that the sensor pad or carrier
arrangements described may be easily handled and cleaned, and are
suitable for placing in the patient's bed under the sheets to form
part of the patient's sleep surface. Because the sensors are not
directly in contact with the skin of the patient, they can be made
more compliant than an array that depends on direct skin contact or
specific body position or orientation. This allows the array to be
more easily attended to or integrated more closely with the
mattress surface or interior, as desired, without necessarily being
built into the bed or mattress in a permanent manner. Instead, by
using the locations and methods of attachment described in greater
detail below, the sensor array can be easily and inexpensively
retro-fit to an existing bed without replacing the entire bed or
mattress.
[0053] It will be appreciated that a typical hospital bed comprises
a bed frame and a mattress assembly. A medical mattress assembly
typically has a foam core surrounded by a waterproof coverlet,
typically made of a low friction urethane or butyl coated fabric
and supplied by the mattress manufacturer as a part of the mattress
assembly. The coverlet normally has a bottom portion below, and a
top portion above, the mattress core. In most cases, the coverlet
is replaceable and is closed around the core with a zipper or
similar arrangement on at least one side of the mattress core. The
coverlet, which can act as a vapor permeable moisture barrier, is
usually wiped down with germicides by housekeeping personnel
between patients. Washable bed sheets, either fitted sheets or flat
sheets, are typically placed over the mattress coverlet. In some
cases, an underlayer, typically made of a stretchable low weight
mesh or gauze, or a thin polyurethane film, is supplied by the
manufacturer to act as a vapor barrier between the coverlet and the
core, preventing moisture vapor from entering the foam core and
providing a smooth, slippery interface between the coverlet and the
foam core.
[0054] In accordance with the present invention, the thin sensor
pad or carrier sheet assembly used to passively monitor the
patient's physiological conditions and movement is securely affixed
to the coverlet in the patient's mattress assembly, to an
additional coverlet placed securely over the mattress assembly, or
to an additional or existing layer disposed between the mattress
core and coverlet, where it lies smooth and flat when in use, under
the sheets or other bedding, substantially hidden from the patient
and hospital staff. This flexible pad or carrier sheet assembly is
comfortable for a patient lying on top of the bed, and may be
conveniently deployed on a variety of different types of medical
mattress without undue interference with the desired mattress
properties.
[0055] In one embodiment, exemplified in FIG. 4, a sensor array 21
provided in the form of a separate freestanding pad or carrier
sheet as previously described is arranged to be placed directly
against the top or bottom surface of the mattress assembly 32, on
the outside of the coverlet 56. Such pad or carrier sheet may be
protected by a covering envelope or other protective layer (not
shown), or may be protected by the bed sheets alone. The pad or
carrier may be permanently or removably connected to the mattress
coverlet surface in a desired location in a variety of different
ways.
[0056] For example, a simple and inexpensive method of attachment
is by bonding, wherein an adhesive layer or a double-sided adhesive
film may be applied between the underside of the sensor pad or
carrier sheet 21 and the outside of the coverlet 56. Adhesive has
the advantage of effectively securing the pad or carrier sheet 24
to the coverlet 56, while making the pad or carrier sheet 21
selectively removable from the coverlet 56 for replacement or
repair. A removable release liner can be applied to the exposed
tacky side of the adhesive backing for ease of handling, storage
and transport of a sensor pad or carrier sheet before it is
attached to the mattress.
[0057] Alternatively, permanent bonding agents can also be used
such as glues, epoxies, chemical bonders, and the like, in lieu of
the adhesive backing. Suitable permanent bonding methods also
include radio frequency welding, ultrasonic welding, and heat
sealing. Mechanical bonds are also possible such as stitching or
sewing of the pad or carrier sheet to the coverlet for a permanent
attachment, or using hook and loop (Velcro.TM.) fasteners, or
providing a high friction interface between the pad or carrier
sheet and the coverlet, for a releasable attachment.
[0058] In an alternative method, shown in FIGS. 5-7, the sensor pad
or carrier sheet 21 may be attached to the mattress assembly 32 by
using straps. As exemplified in FIG. 5, wide straps 34 joined to
the sides of the pad or carrier sheet 21 may be positioned to run
laterally around, or partially around, the mattress assembly 32 so
as to hold the pad or carrier sheet 21 against a top or bottom
surface of the mattress assembly 32. The straps can be in the form
of a continuous band that extends around the mattress assembly, or
they can be formed as segments that join together with buckles,
hook and loop (Velcro.TM.) fasteners, or some other kind of
attachment. Straps that run only partially around the mattress fit
under the mattress and are held in place by the weight of the
mattress and the patient. In another aspect, exemplified in FIG. 6,
narrow straps 36 connected to the corners of the pad or carrier
sheet 21 may be oriented in a multitude of ways such as laterally,
lengthwise diagonal to corners of the mattress, or a combination of
the two, effectively holding the pad or carrier sheet against the
mattress assembly 32. Alternatively, as shown in FIG. 7, webs of
elastic or stretchable material can be used that extend from
opposite sides of the pad or carrier sheet to provide
multi-directional support, such as webs that capture two corners
and the shared surface such as the top two corners of the mattress
assembly. Alternatively, a system of large and wide straps can be
used. Such straps may go entirely around the mattress assembly or
just to the sides or underside. Sections of the straps may
incorporate one of the securing methods listed above, such as
temporary or permanent bonding. Straps or webs that secure the pad
or carrier sheet to the corners of the mattress assembly, such as
those shown in FIGS. 6-7, provide enhanced positional
stability.
[0059] In yet another aspect, the sensor pad or carrier sheet 21
may be placed within or under a protective layer attached to the
mattress assembly to hold the pad or carrier sheet against the
coverlet surface of the mattress assembly 32. For example, as shown
in FIG. 8, a protective layer 40 may be a single layer of material
that covers the exposed side of the pad or carrier sheet 21 (not
shown in FIG. 8), sandwiching the pad or carrier sheet between the
layer 40 and the mattress assembly coverlet. In another aspect, as
shown in FIG. 9, the pad or carrier sheet 21 may be held against
the mattress assembly 32 by a sheet of fabric forming a pocket or
envelope 44 of material that encloses and protects the pad or
carrier sheet and allows the pad or carrier sheet to be inserted
and removed through an opening 48 along an edge of the pocket or
envelope. By closing the opening 48 with an adhesive layer or hook
and loop (Velcro.TM.) fastener, the pad or carrier sheet can be
made selectively removable from the pocket or envelope. The
protective layer 40, or the pocket or envelope 44, may be formed of
any suitable material or combination of materials preferably having
some degree of water resistance, such as Tyvek.TM. (a non-woven
high density polyethylene material) to protect the sensor pad or
carrier sheet from urine, water, blood, or any other fluid that may
be spilled on the patient's bed, and may be placed either on the
top side or bottom side of the mattress assembly. The protective
layer can be secured to the mattress coverlet 56 using any of the
methods listed above, such as temporary or permanent bonding. In
one embodiment, the protective layer may be disposable and used for
only one patient, for only one day, or the like. In an alternative
embodiment, the protective layer 40 or pocket or envelope 44 could
be used to hold a sensor pad or carrier sheet against the surface
of the sheets or other conventional bedding, instead of the
mattress coverlet.
[0060] When a water resistant protective layer is used to hold a
pad 21 against the mattress assembly 32, the external moisture
barrier that forms a part of the sensor pad may be replaced with a
stretchable mesh or gauze material, that fits more loosely around
the sensor elements, potentially improving sensor signal
characteristics and patient comfort. The water resistant protective
layer can be made disposable and does not need to be cleaned.
[0061] In a further alternative embodiment, exemplified in FIGS.
10-13, the sensor array in the form of the pad or carrier sheet
previously described, may be integrated into the coverlet. This may
be achieved by replacing the conventional coverlet with a new
coverlet containing the sensor array as an integral part thereof.
Alternatively, the existing mattress assembly with its conventional
coverlet may be surrounded with an additional new mattress cover or
coverlet containing the sensor array. Both alternatives may utilize
a number of alternative ways, alone or in combination, for
removably attaching the cover or coverlet to the mattress. These
may include a zipper, hook and loop fasteners (for example
Velcro.TM.) or straps to attach the new or replacement cover or
coverlet to the mattress, or by gathering and holding the cover or
coverlet around the base of the mattress using, for example,
elastic, string, or clips.
[0062] The additional replacement cover or coverlet may be formed
of more than one material, such as a patient contact material on
one side and an underside material on the opposite side. The sensor
array may be disposed between the two layers of material, which are
then sealed together to hold the array in place. At least one
opening may be present in the cover or coverlet to allow insertion
of the mattress core inside. The location, shape and size of this
opening is variable as are the methods of closing it.
[0063] In one embodiment, as shown in FIG. 10, a zipper 52 may be
used to close a seam in the cover or coverlet 56. The cover or
coverlet 56 may consist of two halves 60, 64 that are zippered 52
together along all four sides of the mattress at the height midline
or are zippered together along only one, two or three sides.
Alternatively, as shown in FIG. 11, zippers 52 can be placed
entirely on the bottom surface 68 of the cover or coverlet 56
rather than on a side and used to close a seam around the perimeter
of the bottom surface 68. Hook and loop (Velcro.TM.) fasteners, and
adhesive tape are also suitable for closing up overlapping seams of
an opening in the cover or coverlet.
[0064] In another aspect, exemplified in FIG. 12, a large opening
70 is provided at the bottom of the coverlet 56 for receiving the
mattress core 35. The perimeter of fabric surrounding the opening
then may be gathered together and tied, to create tension in the
coverlet and prevent slippage. In one alternative, an elastic band
72 may be threaded either fully or partially through a hem at the
edge of the cover or coverlet, to pull the cover or coverlet
automatically into a tight arrangement. In another alternative, a
string may be threaded through the hem, in which case the string is
manually pulled together via a drawstring to synch and reduce the
size of the opening.
[0065] In yet a further alternative, exemplified in FIG. 13, straps
may be used to tension the cover or coverlet 56 around the mattress
core 35. On the underside of the cover or coverlet, a plurality of
straps 74 or ties may be arranged to extend across an opening 70 in
the cover or coverlet in a zig-zag or criss-cross fashion to permit
the straps 74, and hence the cover or coverlet, to be tensioned so
as to hold the cover or coverlet securely in place. Preferably, the
straps engage and pass through a series of eyelets disposed along
the edge of the cover or coverlet.
[0066] In yet a further alternative, magnets (not shown) may be
attached to the inside of the cover or coverlet on the underside of
the mattress and adhered to the bed frame to achieve a suitable
tension in the cover or coverlet to secure it in place.
[0067] In a presently preferred aspect of the invention,
exemplified in FIGS. 18 and 19, the sensor array 21 may be attached
to or embedded in an underlayer 102 disposed between the coverlet
56 and the mattress core 35. The underlayer is preferably a thin
urethane film which is placed around and secured to the core 35
like a fitted sheet and enclosed by the coverlet (FIG. 19). The
sensor pad may be attached to the inner or outer surface of the
underlayer above the core 35 using any of the methods described as
suitable for attaching the sensor pad or carrier sheet to the
coverlet 56. This arrangement may be achieved by replacing the
conventional underlayer with a new underlayer containing the sensor
array as an integral part thereof. Alternatively, the sensor array
can be attached to the existing underlayer or to an additional
underlayer placed over the existing underlayer. Attaching the
sensor array to the underlayer can help protect the array from
moisture and provides extra patient comfort due to the additional
layers of material between the patient and the sensor array.
[0068] All of the approaches described for attaching the sensor
array to an existing coverlet (FIGS. 4-9), for integrating it into
a replacement or additional coverlet (FIGS. 10-13) or attaching or
integrating it into an existing, additional, or replaced underlayer
(FIGS. 18-19) have the advantage of integrating the sensor directly
into the mattress assembly, while allowing the sensor to be
effectively changed or replaced without replacing the entire
mattress assembly.
[0069] In a further embodiment, the sensor array of the present
invention may also be integrated within the mattress core itself,
either by replacing the mattress core, by positioning the array
within the existing mattress core, or by positioning the array
between the mattress core and the top or bottom portions of the
mattress coverlet.
[0070] For example, as exemplified in FIGS. 14-15, the array 21 may
be placed within an existing mattress core 32, either between
layers 82, 86 of foam or other material that make up the core (FIG.
14) or by creating a pocket 90 or opening in the core (FIG. 15) and
inserting the sensor pad or carrier sheet 21. Preferably, the
pocket is formed by removing a rectangular block 92 of material
from a surface of the foam core. The pad or carrier sheet can be
secured within the pocket by the use of bonding anchors or straps,
in the same way that a freestanding pad or carrier sheet can be
attached to the outside surface of the coverlet. Preferably, the
block 92 of material removed from the core is replaced and secured
by any suitable means once the pad or carrier sheet is placed in
the opening. Alternatively, the entire mattress core can be
manufactured with the sensor elements inside so that it is one
integrated unit. This core could then be inserted into a
conventional mattress coverlet to replace the existing mattress
core.
[0071] In yet another alternative (not shown), the sensor pad or
carrier sheet 21 can be placed between the mattress coverlet 56 and
the mattress core 35 either on the top side of the mattress core or
on the underside. The pad or carrier sheet 21 can be secured to the
adjacent core 32 or the adjacent coverlet 56. Either way, most all
of the previously disclosed attachment methods are appropriate.
[0072] If the pad or carrier sheet 21 is relatively small, bonding
and straps are suitable methods of attachment. Alternatively, the
sensor pad or carrier sheet 21 may be mechanically attached to the
mattress core 35. FIGS. 16-17 exemplify the manner in which small
barbed anchors 78 may be placed through a sensor pad or carrier
sheet 21 and set into the mattress core to secure the sensor pad or
carrier sheet 21 in place. These anchors 78 may be removably or
permanently set. Multiple locations for anchors 78 will likely be
needed, such as at each corner of the pad or carrier sheet 21 or
around the perimeter of the pad or carrier sheet. It will be
appreciated that anchors 78 may be set on any surface of the
mattress core.
[0073] A large pad or carrier sheet resembling the shape of a cover
may be wrapped around the mattress core and be secured by the
methods described above for attaching a new cover or replacement
coverlet to a mattress core. These include seam closure, elastic or
string gathers, straps, or magnets.
[0074] It will be appreciated that the sensor array used in any of
the foregoing embodiments also can be made of free-standing sensor
elements that are assembled and attached discretely and separately
to the corresponding portions of the mattress assembly, rather than
being mounted to a pre-formed sensor pad or carrier sheet. However,
use of the pad or carrier sheet can help insure proper relative
positioning of the sensor elements, provide additional structural
support for the sensor films, and facilitate ease of removal or
attachment of the sensor array to the mattress assembly.
[0075] In yet another aspect of the invention, an apparatus and
method is provided for connecting the processor 24 to the sensor
pad or carrier sheet 21. It may be found that a problem sometimes
arises with regard to the connector cable 26 extending between
processor 24 and the sensor 21 in that accidental force applied to
the cable 26 may damage the connection to the sensors or dislodge
the sensor array 21 from its desired location. In the present
invention, the problem may be solved by firmly attaching an anchor
box 27 to the coverlet 56, as shown in FIG. 20. The connector cable
26 is arranged to extend from the processor 24 to the anchor box 27
so that accidental forces applied to the cable 26 are transmitted
into the coverlet 56 via the anchor box, and are not transmitted to
the sensor array 21 itself. As exemplified in FIG. 21, the anchor
box 27 may comprise a housing 106 and a lid 108 which together
define an enclosed box with an internal space 112. A printed
circuit board 110 is mounted within the internal space, and the
connector cable 26 is arranged to extend from the processor 24 (not
shown in FIG. 21), through an aperture provided in the lid 108 of
the anchor box to the printed circuit board 110. The connector
cable 26 is further arranged to extend from the printed circuit
board to the sensor array 21 (not shown in FIG. 21), passing
through another aperture, preferably in the bottom surface 114 of
the housing. In a preferred embodiment, the lid 108 may be
configured in relation to the housing 106 so that, if the lid is
placed outside the coverlet 56 and the housing is placed inside the
coverlet in juxtaposition with the lid 108, the lid 108 may engage
the housing 106 with a snap fit to achieve a sealed connection
while trapping the fabric of the coverlet 56 between the lid 108
and the housing 106 so that the anchor box 27 is held fixedly in
place on the surface of the coverlet, with the beneficial result as
described above.
[0076] From the foregoing, it will be appreciated that the present
invention allows a passive sensor or sensor array to be integrated
into a patient's mattress in a variety of different ways to support
continuous passive monitoring in a hospital setting. The thin,
flexible sensors are comfortable for the patient to lie on and are
hidden from both the patient and hospital staff when in use. The
sensors maintain the desirable properties of the medical mattress
yet are rugged enough to withstand being crumpled or creased by the
movement of the patient.
[0077] While the specification describes particular embodiments of
the present invention, it will also be apparent to those of
ordinary skill that various modifications can be made without
departing from the spirit and scope of the invention.
* * * * *