U.S. patent application number 14/683892 was filed with the patent office on 2015-10-15 for underbody warming systems with core temperature monitoring.
The applicant listed for this patent is Augustine Biomedical and Design, LLC. Invention is credited to Randall C. Arnold, Brent M. Augustine, Garrett J. Augustine, Scott D. Augustine, Rudolf Andreas Deibel, Scott A. Entenman.
Application Number | 20150290027 14/683892 |
Document ID | / |
Family ID | 52992025 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150290027 |
Kind Code |
A1 |
Augustine; Scott D. ; et
al. |
October 15, 2015 |
Underbody Warming Systems with Core Temperature Monitoring
Abstract
Apparatus and methods related to a non-invasive core temperature
monitor for monitoring the temperature of a patient. In certain
embodiments, the monitor may include a heated underbody support for
heating at least a portion of a patient. The heated underbody
support may include a low thermal mass heater and a temperature
sensor. The heater may heat the peripheral thermal compartment of
the patient to a temperature that is greater than the core
temperature of the patient. The monitor may reduce the temperature
of the low thermal mass heater to a set-point temperature that is
less than the core temperature, allowing the temperature of the low
thermal mass heater to move towards being in thermal equilibrium
with the core body temperature. The core temperature may be
determined when the peripheral thermal compartment of the patient
is in substantial thermal equilibrium with the temperature of the
core thermal compartment of the patient.
Inventors: |
Augustine; Scott D.;
(Deephaven, MN) ; Arnold; Randall C.; (Minnetonka,
MN) ; Entenman; Scott A.; (St. Paul, MN) ;
Deibel; Rudolf Andreas; (Eden Prairie, MN) ;
Augustine; Brent M.; (Minneapolis, MN) ; Augustine;
Garrett J.; (New York, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Augustine Biomedical and Design, LLC |
Eden Prairie |
MN |
US |
|
|
Family ID: |
52992025 |
Appl. No.: |
14/683892 |
Filed: |
April 10, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61977930 |
Apr 10, 2014 |
|
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Current U.S.
Class: |
607/114 |
Current CPC
Class: |
A61G 7/05769 20130101;
A61G 7/005 20130101; A47C 21/048 20130101; A61B 2562/043 20130101;
A61G 2203/46 20130101; A61B 2562/0247 20130101; A61G 2210/50
20130101; A61B 2562/24 20130101; A61F 7/08 20130101; A61G 13/1265
20130101; A61B 5/01 20130101; A47C 27/081 20130101; A61B 2562/18
20130101; A61F 2007/0096 20130101; A61G 2203/34 20130101; A61B
18/16 20130101; A61F 7/007 20130101; A61B 5/6892 20130101; A61G
2210/90 20130101; A61B 5/1116 20130101; A61F 2007/0091 20130101;
A61G 7/05 20130101; H05B 3/36 20130101; A47C 27/10 20130101; A61G
2203/40 20130101; A61G 13/12 20130101; A61F 2007/0071 20130101 |
International
Class: |
A61F 7/00 20060101
A61F007/00; A61F 7/08 20060101 A61F007/08 |
Claims
1. A non-invasive core temperature monitor for monitoring the
temperature of a patient, the core temperature monitor comprising:
a heated underbody support for heating and supporting at least a
portion of the patient, the heated underbody support including a
low thermal mass heater that is configured to be in thermal contact
with at least a portion of the patient during a core temperature
measurement; a temperature sensor configured to be interposed
between an upper surface of the low thermal mass heater and the
patient during temperature monitoring, the temperature sensor
further configured to be in thermal contact with the patient's skin
during temperature monitoring; a switch that controls electric
power to the low thermal mass heater; wherein activation of the
switch can rapidly reduce the electric power supplied to the low
thermal mass heater allowing the low thermal mass heater to rapidly
cool.
2. The non-invasive core temperature monitor of claim 1, wherein
the low thermal mass heater is made of electrically conductive
fabric, film or foil.
3. The non-invasive core temperature monitor of claim 1, wherein a
small amount of thermal insulating material is interposed between
the temperature sensor and the low thermal mass heater.
4. The non-invasive core temperature monitor of claim 1, wherein
the temperature of the low thermal mass heater is controlled to a
temperature that is greater than the core temperature of the
patient, and then rapidly reduced to a temperature that is less
than the core temperature of the patient when the switch is
activated.
5. The non-invasive core temperature monitor of claim 4, wherein
the activation of the switch also activates a timer that measures a
predetermined amount of time to pass while the over-heated
peripheral thermal compartment of the patient cools and comes into
thermal equilibrium with the core thermal compartment at a
predetermined thermal equilibrium time; when the predetermined
thermal equilibrium time is reached, the temperature sensor
measures the skin temperature of the patient; wherein the skin
temperature reflects the temperature of the peripheral thermal
compartment that is in thermal equilibrium with the temperature of
the core thermal compartment and thus the measured skin temperature
correlates with the core temperature of the patient.
6. The non-invasive core temperature monitor of claim 5, wherein
the predetermined amount of time is in the range of 0.5-5
minutes.
7. The non-invasive core temperature monitor of claim 4, wherein
the activation of the switch activates an algorithm that monitors
the temperature-time curve of the measured skin temperatures
following the rapid reduction in heater temperature.
8. The non-invasive core temperature monitor of claim 7, wherein
core temperature corresponds to the temperature of the
temperature-time curve at which a rapid decline in measured skin
temperature transitions to a gradual decline in the measured skin
temperature.
9. The non-invasive core temperature monitor of claim 5, wherein
the measured skin temperature is compared to a desired patient
temperature and the result of this comparison is used to
automatically control a set-point operating temperature of the
heated underbody support.
10. The non-invasive core temperature monitor of claim 8, wherein
the measured skin temperature is compared to a desired patient
temperature and the result of this comparison is used to
automatically control the set-point operating temperature of the
heated underbody support.
11. A method for non-invasive core temperature monitoring, the
method comprising: providing a heated underbody support for heating
at least a portion of a patient, the heated underbody support
comprising: a low thermal mass heater arranged to be in thermal
contact with at least a portion of the patient during core
temperature monitoring; a temperature sensor configured to be in
thermal contact with the patient's skin to measure the temperature
of the peripheral thermal compartment of the patient during
temperature monitoring; a switch that can rapidly reduce the
electric power supplied to the low thermal mass heater; controlling
the low thermal mass heater to a temperature that is greater than
the core temperature of the patient; activating the switch to
rapidly reduce the temperature of the low thermal mass heater to a
set-point temperature that is less than the core temperature of the
patient; and measuring the temperature of the peripheral thermal
compartment that is in substantially thermal equilibrium with the
temperature of the core thermal compartment.
12. The method of claim 10, wherein activating the switch activates
a timer, and wherein measuring the temperature of the peripheral
thermal compartment that is in thermal equilibrium with the
temperature of the core thermal compartment comprises waiting a
predetermined amount of time after activating the switch to allow
the over-heated peripheral thermal compartment of the patient to
cool and come into thermal equilibrium with the core thermal
compartment.
13. The method of claim 11, wherein the predetermined amount of
time is in the range of 0.5-5 minutes.
14. The method of claim 11, wherein the low thermal mass heater is
made of electrically conductive fabric, film or foil.
15. The method of claim 11, wherein activating the switch activates
an algorithm that monitors the temperature-time curve of the
peripheral thermal compartment following the rapid reduction in
heater temperature, and wherein measuring the temperature of the
core thermal compartment comprises monitoring the temperature-time
curve to determine when a rapid decline in measured skin
temperature transitions to a gradual decline in measured skin
temperature indicating that thermal equilibrium between the
peripheral thermal compartment and the core thermal compartment has
been reached and the temperature of the peripheral thermal
compartment is substantially equal to the temperature of the core
thermal compartment.
16. The method of claim 15, wherein the low thermal mass heater is
made of electrically conductive fabric, film or foil.
17. The method of claim 15, wherein thermal insulating material is
interposed between the temperature sensor and the low thermal mass
heater.
18. A non-invasive core temperature monitor for monitoring the
temperature of a patient, the core temperature monitor comprising:
a heated underbody support for heating at least a portion of a
patient; the heated underbody support including a low thermal mass
heater, the low thermal mass heater configured to be in thermal
contact with at least a portion of the patient during temperature
monitoring, the low thermal mass heater configured to heat the
peripheral thermal compartment of the patient to a temperature that
is greater than the core temperature of the patient; a temperature
sensor configured to be in thermal contact with the patient's skin
during temperature monitoring; a switch, or an algorithm of a
processor, that is configured to reduce the temperature of the low
thermal mass heater to a set-point temperature that is less than
the core temperature of the patient allowing the temperature of the
low thermal mass heater to move towards being in thermal
equilibrium with the core body temperature of the patient, and
wherein the algorithm monitors the temperature-time curve; and
wherein the core temperature of the patient corresponds to the
temperature sensed by the temperature sensor when the peripheral
thermal compartment of the patient is in substantial thermal
equilibrium with the temperature of the core thermal compartment of
the patient.
19. The core temperature monitor of claim 18, wherein the low
thermal mass heater is made of electrically conductive fabric, film
or foil.
20. The support of claim 18, wherein the switch, or the algorithm
of the processor, is configured to discontinue or substantially
reduce the power that is supplied to the heater assembly.
21. The support of claim 18, wherein the temperature of the
peripheral thermal compartment that is in substantial thermal
equilibrium with the temperature of the core thermal compartment is
determined by waiting a predetermined amount of time.
22. The support of claim 18, wherein the temperature of the
peripheral thermal compartment that is in substantial thermal
equilibrium with the temperature of the core thermal compartment is
determined by monitoring the temperature-time curve to determine
when a rapid decline in measured skin temperature transitions to a
gradual decline in measured skin temperature indicating that
thermal equilibrium between the peripheral thermal compartment and
the core thermal compartment has been reached and the temperature
of the peripheral thermal compartment is substantially equal to the
temperature of the core thermal compartment.
Description
RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application 61/977,930, filed Apr. 10, 2014, the entire
contents of which are incorporated herein by reference.
BACKGROUND
[0002] Some underbody support mattresses for use during medical
procedures use inflatable chambers as the support mechanism. The
patient must be allowed to "sink" into the inflatable chambers if
they are going to provide maximal surface contact with the
patient's body in order to minimize the contact pressure at any
given point, thus preventing pressure injury to the patient's skin.
"Maximally" sinking into the inflatable chamber could be achieved
by releasing air from the chamber until the moment before the most
protruding body part of the patient touches the base layer of the
mattress or the hard surface below the mattress. At this moment,
the patient is maximally engulfed and supported by the mattress,
much like floating in water. The problem is that there is currently
no reliable way of determining when the most protruding patient
part is near bottoming out versus actually touching the bottom.
[0003] Currently available underbody support mattresses with
inflatable chambers adjust to a desired air pressure that is
determined by the operator. Whether or not the patient sinks into
the mattress and whether or not the body part that is most
protruding "bottoms out" by touching the base layer of the mattress
is totally a function of the operator guessing at the correct
pressure setting. Some mattresses with inflatable chambers claim to
analyze derivatives of the change in pressure to determine the
optimal support pressure. However, none of these pressure-based
control systems reliably allow the patient to sink maximally into
the mattress until the most protruding body part is an optimal
0.5-1.0 inches from bottoming out. In this condition, all body
parts are supported by air and yet the mattress maximally
accommodates the patient's body for maximal contact pressure
relief--similar to floating in water. There is a need for a better
and more reliable control mechanism for reliably determining the
maximum safe accommodation before any body part "bottoms out."
Additionally, there is a need for a safety sensor that can detect
changes in body positioning and/or loss of air from the inflatable
chambers resulting in inadvertent "bottoming out," that may convert
a safe condition into a dangerous condition over time, for example
due to an air leak.
[0004] In addition, there are challenges to accurately measuring
core body temperature through the skin and peripheral thermal
compartment. There is a need for accurately and non-invasively
measuring core body temperature during medical procedures such as
surgery.
[0005] Grounding electrodes have been used during surgery for many
decades. The electrical pathway for the radio-frequency (RF)
electro-surgical units can be completed by directly applying a
grounding pad to the patient's skin for direct electrical
conduction. Alternately, grounding can be accomplished by placing a
larger electrode under the patient which is not in direct
electrical contact but rather creates a condition of capacitive
coupling for grounding the RF electrical current, as described; for
example, in U.S. Pat. Nos. 6,053,910 and 6,214,000. However, these
capacitive coupling electrodes have been generally utilized as
mattress overlays which are inconvenient, require extra cleaning
and are usually embedded into a heavy, cumbersome gel pad.
[0006] Keeping the patient from sliding off of the surgical table
when the table is tilted into a steep, head-down (Trendelenburg)
position, is a constant challenge for surgical personnel and a
danger for the patient. This problem has gotten worse in recent
years with the advent of laparoscopic surgery and particularly with
the advent of robotic surgery. In both of these instances, the
patients are regularly placed into steep Trendelenburg so that
gravity can move the internal organs out of the way of the
laparoscopes. A reliable and convenient way of stabilizing the
patient on the surgical table is needed for the Trendelenburg and
other unusual positions.
SUMMARY
[0007] The underbody support mattresses of this disclosure are
intended for use in medical settings generally. These include the
operating room, the emergency room, the intensive care unit,
hospital rooms, nursing homes and other medical treatment
locations. They may also be used in other settings. Embodiments
described in this application are related to U.S. Pub. Numbers
2012/0279953, 2012/0238901, and provisional application Nos.
61/812,987 and 61/936,508, the disclosures of all of which are
incorporated herein by reference.
[0008] Various embodiments include flexible and conformable heated
underbody supports including mattresses, mattress overlays, and
pads for providing therapeutic warming to a person, such as to a
patient in an operating room setting. In various embodiments, the
heated underbody support is maximally flexible and conformable
allowing the heated surface to deform and accommodate the person
without reducing the accommodation ability of any under-lying
mattress, for example.
[0009] In some embodiments, the heated underbody support includes a
heater assembly and a layer of compressible material. The heater
assembly may include a heating element including a sheet of
conductive fabric having a top surface, a bottom surface, a first
edge and an opposing second edge, a length, and a width. The
conductive fabric may include threads separately and individually
coated with an electrically conductive or semi-conductive material,
with the coated threads of the fabric being able to slide relative
to each other such that the sheet is flexible and stretchable. The
heater assembly may also include a first bus bar extending along
the entire first edge of the heating element and adapted to receive
a supply of electrical power, a second bus bar extending along the
entire second edge of the heating element, and a temperature
sensor. The layer of compressible material may be adapted to
conform to a person's body under pressure from a person resting
upon the support and to return to an original shape when pressure
is removed. It may be located beneath the heater assembly and may
have a top surface and an opposing bottom surface, a length, and a
width, with the length and width of the layer being approximately
the same as the length and width of the heater assembly.
[0010] In some embodiments, the bus bars may preferably be braided
wire. In some embodiments, it may be preferably to coat the bus
bars with a flexible rubber material such as silicone rubber,
during construction of the heater. While braided wire is relatively
tolerant of repeated flexion, if the flexion occurs enough times at
the same spot, even braided wire bus bars can fracture and fail.
Coating the bus bars with silicone rubber can significantly
increase the durability of the bus bars to survive repeated
flexion.
[0011] In some embodiments, the conductive or semi-conductive
material is polypyrrole. In some embodiments the compressible
material includes a foam material and in some embodiments it
includes one or more air filled chambers. In some embodiments, the
heated underbody support also includes a water resistant shell
encasing the heater assembly, including an upper shell and a lower
shell that are sealed together along their edges to form a bonded
edge, with the heater assembly attached to the shell only along one
or more edges of the heater assembly. In some embodiments, the
heating element has a generally planar shape when not under
pressure. The heating element is adapted to stretch into a 3
dimensional compound curve without wrinkling or folding while
maintaining electrical conductivity in response to pressure, and
may return to the same generally planar shape when pressure is
removed.
[0012] In some embodiments, the heated underbody support includes a
heater assembly including a flexible heating element comprising a
sheet of conductive fabric having a top surface, a bottom surface,
a first edge and an opposing second edge, a length, and a width, a
first bus bar extending along the first edge of the heating element
and adapted to receive a supply of electrical power, a second bus
bar extending along the second edge of the heating element, and a
temperature sensor. The underbody support may further include a
layer of compressible support material located beneath the heater
assembly, which conforms to a patient's body under pressure and
returns to an original shape when pressure is removed.
[0013] In some such embodiments, the heating element includes a
fabric coated with a conductive or semi-conductive material, which
may be a carbon or metal containing polymer or ink, or may be a
polymer such as polypyrrole. In some embodiments, the heated
underbody support also includes a shell including two sheets of
flexible shell material surrounding the heater assembly, the shell
being a water resistant plastic film or fiber reinforced plastic
film with the two sheets sealed together near the edges of the
heater assembly. In some embodiments, the heated underbody support
also includes a power supply and controller for regulating the
supply of power to the first bus bar.
[0014] In some embodiments, the compressible material comprises one
or more flexible air filled chambers. In some such embodiments, the
compressible material is a foam material. The heater assembly may
be attached to the top surface of the layer of compressible
material. In some embodiments, the heated underbody support
includes a water resistant shell encasing the heater assembly and
having an upper shell and a lower shell that are sealed together
along their edges to form a bonded edge. In some such embodiments,
one or more edges of the heater assembly may be sealed into the
bonded edge. In some embodiments, the heater assembly is attached
to the upper layer of water resistant shell material. In some
embodiments, the heater assembly is attached to the shell only
along one or more edges of the heater assembly. In some
embodiments, the heated underbody support also includes an
electrical inlet, wherein the inlet is bonded to the upper shell
and the lower shell and passes between them at the bonded edge.
[0015] In some embodiments, the heating element has a first Watt
density when in a generally planar shape and a second Watt density
when stretched into a 3 dimensional shape such as a compound curve,
with the first Watt density being greater than the second Watt
density.
[0016] In some embodiments, the temperature sensor is adapted to
monitor a temperature of the heating element and is located in
contact with the heating element in a substantially central
location upon which a patient would be placed during normal use of
the support. In some embodiments, the heated underbody support also
includes a power supply and a controller for regulating a supply of
power to the first bus bar.
[0017] In some embodiments, the heated underbody support is a
heated mattress and includes a heater assembly and a layer of
compressible material which conforms to a patient's body under
pressure and returns to an original shape when pressure is removed
located beneath the heater assembly. The layer of compressible
material may include one or more inflatable chambers positioned
under the heater assembly. A flexible, water resistant cover may
encase the heater assembly, the layer of compressible material and
the inflatable chambers.
[0018] In some embodiments, the heated underbody support may also
include one or more additional inflatable chambers positioned under
the layer of compressible material, with each of the inflatable
chambers being elongated, having a longitudinal axis and optionally
being positioned side-by-side one another with their longitudinal
axes extending substantially from the first end to the second end
of the support. In some embodiments, the inflatable chambers can be
inflated and deflated in two groups while the support is in use,
with the inflatable chambers being in alternating groups such that
each inflatable chamber is in a different group from each
inflatable chamber which is beside it.
[0019] In some embodiments, the heated underbody support includes a
plurality of additional inflatable chambers. In some embodiments,
the inflatable chambers can each be inflated and deflated
independently while the support is in use. In some embodiments, the
inflatable chambers can all be inflated and deflated simultaneously
as a group while the support is in use. In some embodiments, the
inflatable chambers can be inflated and deflated in two or more
groups while the support is in use. In some embodiments, each of
the chambers belongs to one of two or more groups, and the support
includes separate conduits to each group with each conduit
providing independent fluid communication to one of the groups of
inflatable chambers for independently introducing or removing air
from that group of inflatable chambers.
[0020] In some embodiments, the heated underbody support also
includes a pressure sensor for measuring an actual internal air
pressure of the groups of inflatable chambers, and a controller
including a comparator for comparing a desired internal air
pressure for each group of inflatable chambers with the actual
internal air pressure of each group of inflatable chambers. The
controller may be operatively connected to each of the conduits and
to an air pump and may further include or be operatively associated
with a pressure adjusting assembly for adjusting the actual
internal pressure. The controller may be adapted to cause inflation
or deflation of each group of inflatable chambers to adjust the
actual internal air pressure of each of the group of inflatable
chambers toward the desired internal air pressure.
[0021] In some embodiments, each inflatable chamber within each
group of inflatable chambers is in fluid connection with every
other inflatable chamber of its own group so that air pressure
changes in one inflatable chamber redistribute to all of the other
inflatable chambers in the same group. In some embodiments, an
interface pressure is maintained on a top surface of each group of
chambers at a location which supports a patient's body during
normal use, the interface pressure being below a capillary
occlusion pressure threshold of 32 mm Hg.
[0022] In some embodiments, an inflation characteristic, such as
the volume of air within the inflatable chambers is controlled.
Controlling the volume of air is different than other air
mattresses that control the pressure within the inflatable
chambers. It is impossible to detect changes in pressure as the
patient begins to "bottom out" and therefore pressure control
cannot reliably produce a state of "maximal accommodation" into the
mattress.
[0023] In some embodiments the underbody support includes flexible,
optionally radiolucent compression sensitive switches (e.g.,
compression sensing switches) within one or more of the inflatable
chambers. These switches may be sized to detect when the patient
has sunk into a partially inflated mattress to a point of "maximal
accommodation." The switches may have a large surface area and may
extend substantially the entire length of the inflatable chamber.
These compression sensitive switches are positioned to detect a
body part that is protruding down into the support mattress the
furthest and to prevent that body part from "bottoming out" or
touching the hard surface below the underbody support. The height
of the inflatable chamber(s) at this point may be determined by the
volume of the air in the chamber, not the pressure of the air in
the chamber.
[0024] In some embodiments, the controller including a controller
algorithm of the inflatable underbody support initiates the release
of air from the inflated chambers after the patient is positioned
on the support. The release of air allows the patient to sink into
the support for maximal surface contact and therefore minimal
surface contact pressure. Maximal surface contact occurs just
before the most protruding body part "bottoms out" on the hard
surface below. To achieve this, the air may be released from the
inflatable chambers and the patient may be allowed to sink into the
support until the most protruding body part reaches a predetermined
distance from the bottom. At that point the most protruding body
part may contact and close one or more of the switches.
[0025] In some embodiments the switch may be a compression switch,
including a flexible compression sensitive switch. The switch may
be radiolucent so as not to interfere with x-rays or other imaging
systems. The closed switch may allow a small electric current to
flow to the controller which may respond by stopping the air
release and initiating the next sequence in the controller
algorithm. In some embodiments, the controller algorithm then
energizes the air pumps to re-inflate the inflatable chambers until
the most protruding body part no longer compresses the compression
sensitive switch(es) and the electric current no longer flows
through the switch. In this position, the most protruding body part
is accurately positioned at a predetermined distance above the hard
base surface. With the compression sensitive switch(es) in the open
position, it can then function as a safety sensor, detecting shifts
in patient positioning or loss of air from the inflatable chambers
that may result in inadvertent "bottoming out." Should the
compression sensitive switch(es) close at this point, the
controller algorithm may automatically add more air to the
inflatable chambers until the switch(es) opens and/or may activate
an alarm.
[0026] In some embodiments, the assembly of volume-controlled
inflatable chambers is encased in a foam box-like structure. The
box-like structure operating in conjunction with the inflatable
chambers, creates a structure that allows the side walls to hinge
inward for strain relief of the materials of the upper surface, in
order to prevent "hammocking."
[0027] In some embodiments, one or more temperature sensors are
interposed between the heated underbody support and the back or
dependent body surface of the patient. The heated underbody support
warms the peripheral thermal compartment of the patient that is in
contact with the heated support surface of the underbody support,
creating a condition of near thermal equilibrium between the core
thermal compartment and the peripheral thermal compartment of the
patient's back. In this situation, the skin temperature of the
patient's back in contact with the heater accurately correlates
with core body temperature.
[0028] In some embodiments, the underbody support includes a
grounding electrode for electro-surgical equipment, such as
capacitive coupling grounding electrodes as known in the art. This
electrode may consist of a sheet of flexible and preferably
stretchable conductive fabric that extends substantially across the
entire surface area of the support mattress. Some electrodes have
been supplied as mattress overlays and are generally incorporated
into one or more layers of gel pads which can result in an overlay
that is heavy, cumbersome and interferes with optimal pressure
off-loading. To avoid these problems, various embodiments
incorporate the electrode into the stack construction of the
underbody support, eliminating the need for a heavy and cumbersome
gel pad.
[0029] In some embodiments, the underbody support or the related
heated electric blankets incorporate certain materials that can
protect the polypyrrole heater (e.g., heating element 10), and
other oxidizable electrical components not just from liquids, but
also from oxidizing agents such as hydrogen peroxide
(H.sub.2O.sub.2) disinfecting solutions. In some embodiments,
urethane film may be used as the shell material for the underbody
support or related blankets; however, urethane film is relatively
permeable to hydrogen peroxide vapors, allowing the highly
oxidizing vapors to enter the support or blanket. Once inside, the
peroxide vapors may attack any oxidizable material. These vapors
can cause oxidation and failure of electrical components,
especially polypyrrole. In some embodiments, sacrificial materials
are added that can be preferentially oxidized. Sacrificial
materials are preferably organic materials such as cellulose. In
some embodiments, materials that are known to be catalysts for the
breakdown reaction of peroxide to water and oxygen may be added.
For example, manganese dioxide (MnO.sub.2) powder or other
sacrificial material may be added to one or more of the fabric or
foam layers or adhered to the heater with adhesive.
[0030] In some embodiments, the underbody support uses the fact
that the patient sinks into the support and achieves maximal body
surface contact with the support, to aid in preventing the patient
from sliding off of the surgical table when placed in the steep
Trendelenburg position (head down). In some embodiments, a sheet of
fabric or other material that has been at least partially coated on
both sides with high-friction plastic or rubber may be interposed
between the patient and the support in order to increase the
coefficient of friction. An example of this may be a PVC foam or
silicone rubber applied as a pattern of three dimensional raised
dots onto a fabric. In some embodiments, a foam cushion may be
anchored to the head end portion 410 of the support and extend onto
the mattress portion at the head end portion 410 of the surgical
table 412 for added safety.
[0031] In some embodiments, the underbody support includes a layer
of water-circulating channels over the surface area of the
underbody support. Cold water can be circulated through these
channels for inducing therapeutic hypothermia or therapeutic
cooling.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a cross-sectional view of a heater assembly in
accordance with illustrative embodiments.
[0033] FIGS. 2. is a cross-sectional view of an underbody support
in accordance with illustrative embodiments, including the heater
assembly of FIG. 1.
[0034] FIGS. 3-4. are cross-sectional views of an underbody support
with optional heater assembly in accordance with illustrative
embodiments.
[0035] FIG. 5 is a cross-sectional view of an underbody support
with optional heater assembly in accordance with illustrative
embodiments.
[0036] FIGS. 6-7 are cross-sectional views of an inflatable chamber
including a sensing device in accordance with illustrative
embodiments.
[0037] FIGS. 8-11 are cross-sectional views of an inflatable
chamber in accordance with illustrative embodiments and a
protruding part of the patient.
[0038] FIG. 12 is an illustrative plot of the volume of a most
depressed inflatable chamber vs. time in accordance with
illustrative embodiments.
[0039] FIG. 13 is an illustrative plot of air pressure in an
inflatable chamber vs. time in accordance with illustrative
embodiments.
[0040] FIG. 14 is a cross-sectional view of a compressive sensing
switch in accordance with illustrative embodiments.
[0041] FIG. 15 is a top view of the compressive sensing switch of
FIG. 14 in accordance with illustrative embodiments.
[0042] FIG. 16 is a cross-sectional view of an inflatable chamber
surrounded by a box-like structure in accordance with illustrative
embodiments.
[0043] FIG. 17 is a top view of the inflatable chamber and portions
of the box-like structure of FIG. 16 in accordance with
illustrative embodiments.
[0044] FIG. 18 is a cross-sectional view of the embodiment of the
inflatable chamber and box-like structure of FIG. 17 as deformed by
the weight of a patient in accordance with illustrative
embodiments.
[0045] FIG. 19 is a cross-sectional view of a heater assembly
overlaying an underbody support in accordance with illustrative
embodiments.
[0046] FIG. 20 is a cross section view of a heater assembly folded
up against a patient's front and back side by an underbody support
in accordance with illustrative embodiments.
[0047] FIG. 21 is a temperature sensor interposed between a heated
underbody support and a body surface of the patient in accordance
with illustrative embodiments.
[0048] FIG. 22 is an illustrative plot of skin temperature vs. time
as measured by the temperature sensor of FIG. 21 in accordance with
illustrative embodiments.
[0049] FIG. 23. is a top view of patient anchoring support features
in accordance with illustrative embodiments.
[0050] FIG. 24. is a cross-sectional view of an embodiment the
patient anchoring support features of FIG. 23 in accordance with
illustrative embodiments.
[0051] FIGS. 25-27. are cross-sectional views of a layer of
water-circulating channels in accordance with illustrative
embodiments.
DETAILED DESCRIPTION
[0052] The following detailed description is exemplary in nature
and is not intended to limit the scope, applicability, or
configuration of the invention in any way. Rather, the following
description provides practical illustrations for implementing
various exemplary embodiments. Examples of constructions,
materials, dimensions, and manufacturing processes are provided for
selected elements, and all other elements employ that which is
known to those of skill in the field. Those skilled in the art will
recognize that many of the examples provided have suitable
alternatives that can be utilized.
[0053] Embodiments include underbody supports such as heated
underbody supports, including heated mattresses, heated mattress
overlays, and heated pads. The term underbody support may be
considered to encompass any surface situated below and in contact
with a user in a generally recumbent position, such as a patient
who may be undergoing surgery, including heated mattresses, heated
mattress overlays and heated pads.
[0054] Heated mattress overlay embodiments may be identical to
heated pad embodiments, with the only difference being whether or
not they are used on top of a mattress. Furthermore, the difference
between heated pad embodiments and heated mattress embodiments may
be the amount of support and accommodation they provide, and some
pads may be insufficiently supportive to be used alone like a
mattress. As such, the various aspects which are described herein
apply to mattresses, mattress overlay and pad embodiments, even if
only one type of support is shown in the specific example.
[0055] While there is repeated reference to "heated underbody
supports" in this disclosure, it must be noted that the heat
feature is not a necessary component of every embodiment.
Non-heated underbody support embodiments are also anticipated.
[0056] Various embodiments improve patient warming effectiveness by
increasing accommodation of the patient into the heated mattress,
mattress overlay, or pad, in other words, by increasing the contact
area between the patient's skin and the heated surface of the
mattress or mattress overlay. The heating element, and the foam or
inflatable chambers (e.g., air bladders) of the mattress, which may
also be included, are easily deformable to allow the patient to
sink into the mattress, mattress overlay, or pad. This
accommodation increases the area of the patient's skin surface in
contact with the heated mattress, mattress overlay, or pad and
minimizes the pressure applied to the patient at any given point.
It also increases the surface contact area for heat transfer and
maximizes blood flow to the skin in contact with the heat for
optimal heat transfer. The accommodation of the patient into the
mattress, mattress overlay, or pad is not hindered by a stiff,
non-conforming, non-stretching, hammocking heater. Additionally, in
various embodiments, the heating element is at or near the top
surface of the underbody support, in thermally conductive contact
with the patient's skin, not located beneath thick layers of foam
or fibrous insulation.
[0057] As shown in FIGS. 1-2, the combination of the thermal
warming effectiveness and the skin pressure reduction effectiveness
of a heated underbody support 3 (e.g., FIGS. 2, 19 and 23) can be
optimized when a heating element 10 is overlaying a layer, such as
a compressible material layer 20, that can provide maximal
accommodation 22 of a patient (e.g., FIG. 23) positioned on the
underbody support 3 (e.g., mattress).
[0058] In this condition, the heating element 10 is in contact with
a maximal amount of the patient's skin surface 232 which maximizes
heat transfer and pressure reduction. Heated underbody supports 3
made with inflatable chambers 170 (FIG. 2) forming or included in
the compressible material layer 20, or in addition to the
compressible material layer 20, can also provide excellent
accommodation. Further, a heated underbody support 3 with excellent
accommodation properties having a heating element 10 as described
herein avoids degrading the accommodation properties of the
underbody support 3 when a heater assembly 1 is added or included.
Therefore, the combination of the heater assembly 1 design with an
accommodating underbody support 3, made with one or more inflatable
chambers 170, is advantageous and synergistic for the effectiveness
of both technologies. However, all features described herein may be
used independently, or in combination with one another. For
example, the underbody support 3 described herein may or may not
be: heated, include grounding, have hydrogen peroxide protection,
patient securing features, water circulating channels, or any other
features described herein. Likewise, the heater assembly 1
described herein may or may not include: an underbody support 3,
include grounding, have hydrogen peroxide protection, patient
securing features, water circulating channels, or any other feature
described herein. Illustrative examples are provided, and all
possible combinations of the features herein are considered
embodiments of this disclosure.
[0059] As shown in FIG. 1, some embodiments of the heater assembly
1 include a heating element 10 coupled by a layer of adhesive 30 to
the layer of compressible material 20. The heating element 10, the
layer of compressible material 20 and the adhesive 30 may then be
encapsulated and sealed by upper and lower shells 42, 44. The seal
may be a hermetic seal.
[0060] In some embodiments, as shown in FIG. 2, bus bars 62, 64 of
the heating element 10 are optionally made of braided wire. While
braided wire is relatively tolerant of repeated flexion, if the
flexion occurs enough times at the same spot, even braided wire bus
bars can fracture and fail. In some embodiments, the bus bars 62,
64 may be braided wire bus bars 62, 64 and may be coated with a
flexible rubber-like material such as silicone. The coating may be
applied during construction of the heater assembly 1.
[0061] Coating the bus bars 62, 64 with silicone can vastly
increase the durability of the bus bars 62, 64 to repeated flexion.
The silicone or other coating can serve at least two functions,
first, it forces the individual wire strands to form a larger
radius during flexion and second, it stabilizes the individual wire
strands so that they do not abrade each other during flexion.
Thicker coats of silicone rubber or other material on the bus bars
62, 64 may provide more protection from flexion fractures than thin
coats.
[0062] Our testing has shown that braided bus bars, like bus bars
62, 64, sewn in parallel on a heating element 10 made from a piece
heater material such as a non-woven heater fabric, can be
repeatedly and bent or flexed at a specific point. During testing
all of the bus bars were flexed along a single crease in the heater
fabric, through a 360.degree. arc, gently creasing the bend and
then flexing it in the other direction though a 360.degree. arc.
This process was repeated until the bus bars failed at the bend.
Uncoated and thinly coated bus bars began to fail at approximately
350 flexions and totally failed by 450 flexions. Bus bars with a
"medium" coating of silicone rubber (approximately 1/32 inches
thick) failed between 1900 and 2100 flexions. Bus bars with a
"thick" coating of silicone rubber (approximately 1/16 inches
thick) showed no signs of failure after 2500 flexions.
[0063] FIGS. 2, 3 and 4 show an embodiment of an underbody support
3 comprising one or more inflatable chambers 170 (e.g., air
chamber, fluid chamber), and a heater assembly 1 overlaying the one
or more inflatable chambers 170. In some embodiments, a single
inflatable chamber 170, or a plurality of elongated inflatable
chambers 170 are positioned under the heater assembly 1. The
plurality of elongated inflatable chambers 170 may be cylindrical
in shape and may be oriented in parallel and positioned
side-by-side one another, with their long axes extending
substantially from one side of the underbody support 3 mattress to
the other side. However, other inflatable chamber 170 shapes and
orientations are anticipated. The inflatable chambers 170 may be
round or ovoid in cross section. They may or may not be physically
secured to an adjacent inflatable chamber 170. Alternately, they
could be secured to a base sheet or simply positioned and contained
within a cover 160 (e.g., mattress cover) without being secured.
The inflatable chambers 170 may be made of a fiber-reinforced
plastic film or a plastic film that has been bonded, laminated or
extruded onto a woven or non-woven fabric reinforcing layer.
Urethane may be used as the plastic film, but other plastic film
materials are anticipated. Woven nylon may be used as the
reinforcing layer, but other fabric materials are anticipated. The
inflatable chambers 170 may also be used for pressure reduction
alone, in an underbody support 3 without a heater assembly 1 or
heating element 10.
[0064] The inflatable chambers 170 can be sealed and static, or
connected together in fluid connection to allow redistribution of
air between the inflatable chambers 170. In some embodiments, the
inflatable chamber 170 can be actively inflated and deflated while
the underbody support 3 is in use. The inflatable chambers 170 may
be inflated and deflated each independently, all simultaneously, or
in separate groups, while the underbody support 3 is in use. In
some embodiments, the inflatable chambers 170 are each a part of
two separate groups and may be segregated, for example, by every
other inflatable chamber 170 (e.g., alternating inflatable chambers
170) according to their relative side-by-side positions. A conduit
or conduits may be in separate independent fluid communication with
each inflatable chamber 170 of the group of inflatable chambers 170
for independently introducing or removing air from that group of
inflatable chambers 170.
[0065] Alternately, there may be only a single group of inflatable
chambers 170 or there may be more than two groups of inflatable
chambers 170 which can be separately inflated or deflated. If
multiple groups of inflatable chambers 170 are used, they may or
may not be evenly or symmetrically arranged. For example,
inflatable chamber 170 groups may be separated according to the
amount of weight-bearing associated with that area. Inflatable
chambers 170 in greater weight bearing areas, such as the torso and
hips, may be in a first group, while inflatable chambers 170 in
areas bearing less weight, such as those supporting the head and
legs, may be a separate group of inflatable chambers 170. In this
way, the lighter portions of the patient's body may be supported by
inflatable chambers 170 that are inflated to a lower air pressure
than inflatable chambers 170 that support more weight/heavier body
portions.
[0066] Inflatable chambers 170 may be secured to the adjacent
inflatable chamber 170 or to a base sheet or may be secured by the
ends to an element running along each side of the underbody support
3, and in some embodiments the inflatable chambers 170 and their
connectors for fluid connection may be individually detachable. In
this instance, if a single inflatable chamber 170 or connector
fails or is damaged, it can be replaced without requiring the
replacement of the entire inflatable underbody support 3.
[0067] The material forming the inflatable chamber 170, such as a
plastic film, may be bondable with RF, ultrasound, heat, solvent,
or other bonding techniques. The film or film layer of the laminate
may be folded back on itself and a single longitudinal and two end
bonds that may cooperate to form an inflatable chamber 170. More
complex inflatable chamber 170 construction and bonding embodiments
are anticipated.
[0068] The conduit fluid connection for air flow to and from and
between the inflatable chambers 170 may be plastic tubing, for
example. The inlet into the inflatable chamber 170 can be through
one of the bonded seams or may be through a surface of the
inflatable chamber 170. To prevent occlusion of the tubing at the
inlet, the tubing may extend one or more inches into the inflatable
chamber 170. Other conduits are anticipated, such as a molded or
inflatable plenum that may run the length of the underbody support
3.
[0069] In some embodiments such as FIG. 2, a heater assembly 1 (a
heater assembly 1 encased within a water resistant shell 42, 44) is
placed on top of the inflatable chambers 170 so that the conductive
fabric heating element 10 is at or near the top surface of the
underbody support 3. Alternately such as shown in FIG. 5, a heater
assembly 1 (without a shell 42, 44) could be placed on top of the
inflatable chambers 170 so that the heating element 10 is at or
near the top surface of the underbody support 3 mattress. The
underbody support 3 may include a flexible, water resistant cover
160 that encases the heater assembly 1 and the inflatable chambers
170. Alternately as shown in FIG. 5, heater assembly 1 could be
placed on top of a polymeric foam pad 150 such as viscoelastic or
urethane foam. In some embodiments the inflatable chambers 170 may
be used as an underbody support 3 mattress without a heater
assembly 1.
[0070] In some embodiments, the water resistant cover 160 is a
plastic film laminated or extruded onto a woven or knit fabric such
as "Naugahyde." This construction is soft and durable. Alternately,
the cover 160 can be made of plastic film, fiber-reinforced plastic
film or a plastic film laminated or bonded to a woven, non-woven,
or knit fabric. Covering 160 made of plastic film laminated or
extruded onto a woven or knit fabric may include sealed seams such
as RF, ultrasound or heat, if the plastic film side is inverted
into the seams so that layers of plastic film are in opposition to
each other. Alternately, the polymer coated fabric is well-suited
to a sewing process for creating the seams. Seams created by a
sewing process may advantageously include an adhesive bond for
sealing the sewn seam against liquid intrusion.
[0071] The heater assembly 1 of the underbody support 3 may be
"free floating" within the water resistant cover 160 of the
underbody support 3. Alternately, the heater assembly 1 may be
attached to the inflatable chamber 170 or foam pad 150, or attached
to the cover 160, either at the edges of the heater assembly 1 or
on or across the top or bottom surface of the heater assembly
1.
[0072] One or more edges of the heater assembly 1, such as two or
four edges, may be attached to the ends of the elongated inflatable
chambers 170 or compressible material layer 20 by snaps, Velcro or
any other suitable forms of attachment. Such embodiments may
stabilize the heater assembly 1 within the underbody support 3. A
series of independent securing tabs or flaps may extend laterally
from the bonds 48 of the heater assembly 1 encapsulation shell 42,
44. As the inflatable chambers 170 inflate and become turgid, they
simultaneously stretch the heater assembly 1 laterally, assuring
that the heating element 10 cannot wrinkle and fold on itself or
become displaced.
[0073] In some embodiments, an inflation characteristic such as the
volume of air within the inflatable chambers 170 is controlled.
Controlling the volume of air is different than all other air
mattresses known to the instant inventors that control the pressure
within the inflatable chambers 170. In other systems, it is
impossible to detect changes in pressure as the patient begins to
"bottom out" and therefore pressure control cannot reliably produce
a state of "maximal accommodation" into the mattress. In contrast,
controlling for and measuring an inflation characteristic (e.g.,
air volume, indication of near collapse, a distance between
portions of the inflatable chamber 170) in the most depressed
inflatable chamber 170 with an appropriate sensor, can insure
"maximal accommodation." "Maximal accommodation" is the point when
the patient has maximally sunk into the underbody support 3, but
has not yet touched the hard base with their most protruding body
part 230 (e.g., FIGS. 8-11). A variety of sensing technologies for
determining air volume within the inflatable chambers 170 may be
used in various embodiments.
[0074] As in FIGS. 6 and 7, some embodiments of the underbody
support 3 include sensing devices such as switches 200. Switches
200 may be flexible, radiolucent compression sensing devices within
one or more of the inflatable chambers 170. In some embodiments,
switches 200 may be other types of switches other than flexible,
radiolucent compression sensitive switches. The switches 200 may be
positioned to sense the patient body part that is protruding down
into the underbody support 3 the furthest and to prevent that body
part from "bottoming out" or touching the hard surface below the
underbody support 3. Since the "most protruding body part," or
portion of the body sinking deepest into the underbody support 3
(e.g., element 230, FIGS. 8-11), is unpredictable (buttocks, hip,
elbow, shoulder), the location of the most protruding body part on
the underbody support 3 is also unpredictable. Therefore, the
switches 200 are preferably located in each of the inflatable
chambers 170 and have a large surface area relative to the
inflatable chamber 170 size.
[0075] In the embodiment of FIGS. 6 and 7, the compression
sensitive switches 200 are sized and shaped to fit the size and
shape of the inflatable chamber 170 and to activate at a given
volume of air that correlates with the height thickness of the
switch 200. In the case of a tubular inflatable chamber 170, the
switches 200 are preferably relatively wide, covering 0.3-0.7 of
the diameter of the inflated inflatable chamber 170 (FIG. 6) and
preferably extending substantially the entire length of the
inflatable chamber 170 (FIG. 7). For example, if the inflatable
chamber 170 is 3 inches in diameter and is 18 inches long, the
surface area of the switch 200 may be 1-2 inches wide and 16 inches
long. Other switch 200 widths and lengths are anticipated. The
relatively large surface area of the individual switches 200, and
the arrangement of the individual switches 200 into a pattern may
cover substantially the surface area of the underbody support 3.
This assures that the "most protruding body part" at any location
on the surface of the underbody support 3 can be detected.
[0076] The compression sensitive switches 200 may be physically
located within the inflatable chamber(s) 170, so that they are
protected from random compression by the adjacent inflatable
chamber 170, when the inflatable chamber 170 is inflated and the
underbody support 3 is in use. In some embodiments, being located
within the inflatable chamber 170 also protects the switch 200 from
damage. It also assures that the compression sensitive switch 200
is contacted by "the most protruding body part" 230 (FIGS. 8-11) at
a precise height above bottoming out against the hard base, or
above the bottom of the inflatable chamber 170 or other surface,
which allows maximum accommodation of the patient 230 (FIGS. 8-11)
into the underbody support 3 and yet protects against bottoming
out. For example, in FIGS. 8 and 9, if the inflatable chamber 170
has a cross-sectional diameter of 3 inches, the switch 200 may
preferably be designed to sense contact when "the most protruding
part" of the patient 230 is 0.75-1.0 inches above bottoming out.
This height correlates with a given volume of air in the inflatable
chamber 170. Other switch contact heights are anticipated which
correlate with other volumes of air. If additional accommodation of
the patient into the support is desirable, the switch 200 may be
designed to sense contact at a height of less than 0.75 inches. If
added safety is desired, the switch 200 may be designed to sense
contact at a height of more than 1.0 inches. While the compression
sensitive switches 200 disclosed herein may be preferred, other
types and construction of switches, including volume measuring
switches and distance measuring switches are anticipated.
[0077] Other switches 200, such as pressure-sensing membrane
switches are well-known in the art. Pressure-sensing membrane
switches generally consist of two separated metal foil contacts
that can be pressed together to make contact in response to applied
pressure. The precise positioning of the metal foil is determined
by the shape of the stiff plastic film (membrane) to which the foil
is applied. These switches are minimally flexible because flexion
may cause the metal foil contacts to close in the absence of
applied pressure. These membrane switches are hard, generally made
of a stiff plastic film adhered to a hard surface like metal or
glass in order to protect the fragile metal foil contacts. Finally,
the metal foil conductors and contacts are radio-opaque, meaning
that they show up on x-ray. While these pressure sensing membrane
switches may be used in various embodiments, the switches 200 used
in various embodiments may alternatively be flexible, radiolucent,
durable compression sensitive switches, and not require mounting to
a hard surface to assure proper functioning. The instant invention
may use any other suitable type of switch.
[0078] As shown in FIGS. 6-9, the compression sensitive switches
200 of the instant invention may use electrically conductive fabric
pieces as the conductor and/or contacts 202, 204. The conductive
fabric pieces (e.g., 202, 204) may be polypyrrole coated onto any
woven or non-woven fabric. Alternately, the conductive fabric in
the switch 200 may be carbon fiber fabric or fabric that has been
coated with conductive ink or metal such as silver. Alternately,
the conductor 202, 204 in the switch 200 may be conductive ink
applied to polymeric film or conductive materials such as carbon or
metal impregnated into polymeric films.
[0079] For the following description, it is assumed that the
inflated inflatable chamber 170 is a tube that is approximately 3
inches in diameter and 18 inches long as in FIGS. 6 and 7. However,
the size and shape of the compression sensitive switches 200 may
change for inflatable chambers 170 of other sizes and shapes. The
contacts 202, 204 and conductors of the switch 200 may include two
pieces of conductive fabric. In this example, each of the two
pieces of the conductive fabric contacts 202, 204 may be 1.5 inches
wide and 16 inches long. The two conductive fabric contacts 202,
204 may be adhesively bonded to both sides of a strip of
compressible material that forms a compressible switch layer 206.
The compressible switch layer 206 may be a resilient open-cell foam
material, such as urethane foam. However, other materials such as
polymeric foam materials or high-loft fibrous materials may be
used.
[0080] In some embodiments, the compressible switch layer 206 may
be 3/16-3/4 inches thick, however, other thicknesses of
compressible switch layers 206 may be used. One or more holes 208
may be cut through the compressible switch layer 206. Preferably, a
pattern of multiple holes 208 may be cut through the compressible
switch layer 206. The size and shape of the holes 208 may be
determined by the thickness, size, shape and compressibility of the
compressible switch layer 206. For example, if the compressible
switch layer 206 is 3/16 inch thick, the holes 208 may be 1/2-3/4
inches in diameter. If the compressible switch layer 206 is 3/4
inches thick, the holes 208 may be 3/4-1 inch in diameter.
Embodiments include holes 208 of various number, shape, size and
pattern.
[0081] In the embodiment of FIGS. 6 and 7, the compression
sensitive switches 200 may also include two layers of compressible
foam. An upper compressible foam layer 210 and a lower compressible
foam layer 212, sandwiching the conductive fabric pieces/contacts
202, 204 and the compressible switch layer 206 there-between. The
compressible foam layers 210, 212 may be attached to the conductive
fabric pieces/contacts 202, 204 with adhesive forming a five-layer
sandwich construction. The compressible foam layers 210, 212 may be
1/4-1/2 inches thick but other thicknesses may be used. Many foam
materials are suitable including open cell urethane. While foam may
be used for these layers, other materials such a high-loft fibrous
materials may also be used. The lower compressible foam layer 212
that is positioned on the bottom side of the switch 200 may be
tapered toward its long edges in order to seat in the curved shape
of the inflated inflatable chamber 170. Curving the lower
compressible foam layer 212 allows the conductive fabric pieces
202, 204 and the compressible switch layer 206 (the active part of
the switch) to remain relatively flat, despite being located within
a curved chamber.
[0082] When the compressible switch layer 206 is compressed as
shown in FIGS. 8 and 9, the two pieces of conductive fabric 202,
204 contact each other within the space(s) created by the one or
more holes 208. A wire conductor may be attached to each of the
conductive fabric contacts/pieces 202, 204. A small electric
potential is applied to the conductive fabric contacts/pieces 202,
204 and when they contact each other, an electric current flows
through the switch 200, activating the controller.
[0083] The controller may be activated by active feedback data
derived from the current flowing through one or more of the
compressed compression sensitive switches 200. This signal allows
the system to maintain a desired internal air volume within the
most depressed inflatable chamber 170 by adjusting the amount of
inflation of the most depressed inflatable chamber 170 or of the
groups of inflatable chambers 170, such as first and second groups
of inflatable chambers 170. Controlling the air volume in the most
depressed inflatable chamber 170 independent of air pressure,
allows maximal accommodation of the patient 230 into the inflatable
underbody support 3. This is in contrast to all other air-filled
support mattresses and air-filled support surfaces known to the
instant inventors, which rely on controlling air pressure.
[0084] FIG. 12 illustrates the volume vs. time curve measured when
air is released from the most depressed inflatable chamber 170 with
a patient laying on the underbody support 3 mattress. This allows
the patient to progressively sink into the underbody support 3,
which if carried to a conclusion would result in the patient laying
on the hard base layer without any air there between at point E.
However, when the volume decreases to the point B where the
compression sensitive switch(es) 200 is compressed in the most
depressed inflatable chamber 170, deflation is reliably stopped
before the patient "bottoms out," point E. This condition is also
illustrated in FIGS. 8 and 9.
[0085] In contrast, FIG. 13 illustrates the pressure vs. time curve
measured when air is released from the inflatable chambers 170 with
a patient laying on the underbody support 3. This allows the
patient to progressively sink into the underbody support 3, which
if carried to a conclusion would result in the patient laying on
the hard base layer without any air there between. At time F, the
chambers 170 are inflated to a pressure that is higher than the
pressure exerted by the weight of the patient. With deflation, the
pressure gradually drops and at time G the pressure in the
underbody support 3 is determined by the weight and geometry of the
patient. With continued deflation, the pressure remains
substantially unchanged as the patient continues to sink into the
deflating underbody support (GI). At time H, the most protruding
point of the patient 230 (FIGS. 8-11) bottoms out on the hard base
layer; however, no change in pressure is noted despite "bottoming
out" having occurred. A reduction in measured pressure is not noted
until time I, when a majority of the patient is "bottomed out" and
is resting on the hard base layer of the underbody support 3.
[0086] From FIG. 12, it is apparent that the precise switch 200
closure at time B as shown in FIGS. 8 and 9, indicating that the
appropriate "maximal accommodation" volume has been reached, is a
safe and reliable way to optimally support the patient. In
contrast, the subtle changes in pressure shown in FIG. 13 cannot be
reliably detected and do not correlate with the "bottoming out" (H)
of the patient's most protruding part. Therefore, it should be
evident that controlling the inflatable chambers 170 of this
support surface by detecting and controlling air volume is a
significant improvement in reliability and safety compared to the
standard method of detecting and controlling air pressure.
[0087] Alternately, or additionally, the inflatable underbody
support 3 may include pressure sensor assemblies capable of
detecting, in real time, the actual internal air pressure of the
inflatable chambers 170 and may also include a comparator which may
be in operational communication with the controller for comparing a
desired internal air pressure value of the inflatable chambers 170
with the actual internal air pressure, and a pressure adjusting
assembly, also in operational communication with the controller,
for adjusting the actual internal pressure. The controller may be
activated by active feedback data derived from the comparator for
maintaining a desired internal pressure value in the inflatable
chambers 170 by adjusting the amount of inflation of the inflatable
chamber 170 or of the groups of inflatable chambers 170, such as
first and second groups of inflatable chambers 170.
[0088] The controller may be operationally connected to a first
conduit and a second (or multiple) conduit and a pump for inflating
the inflatable chamber 170 or plurality of inflatable chambers 170.
Each inflatable chamber or plurality of chambers 170 may be
independent of each other inflatable chamber 170 so that each
inflatable chamber 170 may react to air pressure changes
independently, or may be connected as a group and may react in
concert with the air pressure changes in the other inflatable
chambers 170 of the group. The air may be redistributed within the
chambers 170 and the interface pressure may be maintained at any
point on the top surface of each of the plurality of chambers 170
which is engaged with an anatomical portion of the user's body, at
an average pressure below a capillary occlusion pressure threshold
of 32 mm Hg, for example.
[0089] The total thickness of the compression sensitive switch 200
is determined by the desired distance between the patient's "most
protruding part" 230 (FIGS. 8-11) and the point of "bottoming out."
For example, if the desired resting distance between the most
protruding part and the base of the support is 3/4-1 inch, the
total thickness of the stack of materials forming the compression
sensitive switch 200 should be approximately 1-11/4 inch. This may
consist of an upper compressible foam layer 210 that is 1/4 inch
thick and a compressible switch layer 206 that is 1/4 thick and a
lower compressible foam layer 212 that is 1/2-3/4 inch thick. Other
heights and thicknesses are anticipated.
[0090] As shown in FIGS. 8-11, the entire switch 200 assembly may
be a laminated compression sensitive switch 200 advantageously
encapsulated in a durable and preferably vapor resistant switch
encapsulation shell 214 for added durability and protection from
mechanical and chemical damage. The encapsulation material may be a
coating such as silicone rubber, urethane, PVC or neoprene. A
spray-on vinyl coating may be applied to the outer surface of
switch 200. Alternately, the switch encapsulation shell 214 may be
made of one or more layers of plastic film such as urethane or PVC,
formed into a sealed shell, hermetically-sealed or otherwise. Other
suitable polymeric encapsulation materials and techniques are
anticipated.
[0091] As shown in FIGS. 6 and 7, the entire compression sensitive
switch 200 may be located within an inflatable chamber 170. The
switch 200 may be anchored into a specific position, such as at the
bottom of the inflatable chamber 170. However, in some embodiments,
the switch could be attached to the top of the inflatable chamber
170. The switch 200 may be bonded to the material of the inflatable
chamber 170 with adhesive or by thermal bonding techniques.
Alternately the switch encapsulation shell 214 may include one or
more stripes of plastic film material that can be bonded to the
inflatable chamber 170 material. For example, plastic film may
extend from each end of the switch 200 and be bonded into the
bonded seam forming the ends of the inflatable chambers 170.
[0092] In some embodiments, the controller algorithm inflates the
inflatable underbody support 3 to a predetermined air pressure such
as 1 psi, while the patient is being moved and positioned on the
underbody support 3 (FIG. 13, Time F). Positioning the patient is
facilitated by having the underbody support 3 in a relatively firm
condition, preventing the patient from sinking into the underbody
support as shown in FIGS. 6 and 7.
[0093] In some embodiments, the controller is then signaled, for
example, by the operator pressing an operation switch, that the
patient is positioned and the controller should initiate the
algorithm that releases air from the inflated inflatable chambers
170. Alternately, the controller may automatically sense the
positioning of the patient by a change in air pressure in the
underbody support 3 caused by the patient's weight and initiate the
algorithm to start. The release of air may allow the patient to
sink into the underbody support 3 for maximal surface contact with
the patient's skin and therefore minimal surface contact pressure
with the skin (FIG. 12, Time AB).
[0094] Maximal surface contact may occur just before the most
protruding body part 230 (FIGS. 8-11) "bottoms out" on the hard
surface below. In this position, the patient is as close to
floating (as in floating in water) as can be achieved with an
inflatable underbody support 3 of any given thickness. The air may
be released and the patient may be allowed to sink into the
underbody support until the most protruding body part 230 reaches a
predetermined distance from the bottom of the most depressed
inflatable chamber 170. At that point the most protruding body part
230 contacts and closes one or more switches 200 (e.g., flexible,
radiolucent compression sensitive switches) (FIG. 12, Time B). This
situation is also illustrated in FIGS. 8 and 9.
[0095] The closed switch 200 allows a small electric current to
flow to the controller activating the next step in the sequence of
the algorithm, which stops the air release. In some embodiments,
the next sequence in the controller algorithm is then activated and
it energizes the air pumps to re-inflate the inflatable chambers
170 until the most protruding body part of the patient 230 is
lifted and no longer compresses the compression sensing or pressure
sensing switch 200 within the most depressed inflatable chamber 170
and the electric current is no longer flowing through the switch
200 (FIG. 12, point C). This situation is also illustrated in FIGS.
10 and 11. In this position, the most protruding body part of the
patient 230 is accurately positioned at a predetermined distance
above hard base surface. To achieve and maintain this maximally
accommodating position, the air volume within the inflatable
chambers 170 must be controlled, not the air pressure.
[0096] With the compression sensitive switch 200 in the open
position, it can then function as a safety sensor, detecting shifts
in patient positioning or inadvertent loss of air from the
inflatable chambers 170 that may result in "bottoming out." Should
the switch 200 re-close during the operation (FIG. 12, point D),
reestablishing the situation illustrated in FIGS. 8 and 9, the
controller will sense the electrical current flow and the algorithm
may automatically activate the air pumps to inflate the inflatable
chambers 170 until the switch 200 once again opens and/or an alarm
may be activated.
[0097] The safety sensor feature of the compression sensitive
switch(es) can also be used to document that the patient did not
have a body part that was inadvertently "bottomed out" for a
prolonged period during the operation. This information can be
automatically transmitted to the electronic medical record (EMR)
for documentation. Documentation that the patient did not "bottom
out" during surgery indicates that the patient was well supported
and protects the surgical staff from blame should a pressure ulcer
later form.
[0098] At the end of the surgical or medical procedure, the
operator may once again signal the controller, such as by pressing
a switch, to initiate the algorithm that energizes the air pumps to
re-inflate the inflatable chambers 170 to a predetermined air
pressure. The relatively firm underbody support 3 may facilitate
moving the patient off of the underbody support 3.
[0099] Embodiments of the switches 200 for control of the volume of
air within the inflatable chambers 170 have been disclosed. Other
technologies for detecting air volume or a minimum
distance/clearance between portions of the inflatable chambers 170
may alternatively be used. Other designs of switches 200, such as
compression sensitive switches including different materials,
different stacks of materials and different constructions may also
be used. Different algorithms used to control the function of the
inflatable chambers 170 in response to inputs from the volume
sensors or compression sensitive switches 200 may also be used in
various embodiments.
[0100] In some embodiments, the inflatable chambers 170 of the
underbody support 3 include a surrounding structure that preferably
may be made of foam. As shown in FIGS. 16-18, the compressible
material layer 20 may be a layer of foam positioned on top of the
inflatable chambers 170. Many types of foam are anticipated for
this use but urethane upholstery foam that is both durable and
inexpensive may be used. Two flexible side walls 80, 82 may also be
made of foam and may be bonded 84 (FIG. 18) to the compressible
material layer 20. Two flexible end walls 88, 90 may also be made
of foam and may be bonded 84 to the compressible material layer 20
and bonded 98 (FIG. 18) to the flexible side walls 80, 82. The
resulting box-like structure 92 may be open on the bottom and fit
over the assembly of inflatable chambers 170, creating the external
appearance of a cut foam mattress, rather than the rounded and
poorly fitted look of the inflatable chambers 170. In some
embodiments, the bonded joints 84 and 98 may be reinforced by
bonding a layer of fabric to the foam adjacent the joints with the
fabric traversing the joints for added strength.
[0101] In some embodiments, the box-like structure 92 may be made
of foam and may sit on a base layer 86, also optionally made of
foam. The fasteners 94 between the flexible side 80, 82 (FIG. 16),
the end walls 88, 90 (FIG. 17), and the base layer 86 are
preferably detachable. The fasteners 94 may be strips of Velcro
hook and loop fasteners. However, other fasteners such as zippers
and snaps may be used. The box-like structure 92 may be encased
within a water resistant cover 160.
[0102] The box-like structure 92 of this invention may not only
improve the cosmetic appearance of the underbody support 3 compared
to the look of tubular inflatable chambers 170, it may also serve
the function of preventing "hammocking." Hammocking occurs when the
materials of the upper surface of a support or mattress cannot
stretch adequately to allow the patient to optimally sink into the
support. If the materials of the upper surface of the support are
stretched laterally, the materials may act like a cot or hammock
when the person lays on the support and prevent the person from
sinking into the support. This may negate the pressure relieving
purpose of the support.
[0103] In various embodiments, the flexible side walls 80, 82 and
to some extent the flexible end walls 88, 90 in combination with
the collapsible inflatable chambers 170, may create a tension
relieving hinge shown in FIG. 18. As the inflatable chambers 170
are deflated, the person laying on the underbody support 3 sinks
into the underbody support 3, depressed by the weight of the
patient 180 on the upper surface. When depressed by the weight of
the patient 180, the upper surface (e.g., upper surface of 160, 20,
FIG. 18) pulls the materials of the upper surface of the underbody
support 3 toward the center line of the underbody support 3. This
would cause hammocking but for the flexible side walls 80, 82
hinging inward 190 as shown in FIG. 18, to provide strain relief
for the materials of the upper surface (e.g., 160, 20 in FIG.
18).
[0104] Surgeons have been known to complain about legacy air
mattresses used during surgery. Since the patient is "floating" on
a cushion of air, they also tend to move when they are leaned
against or pulled, as in the firm application of a surgical
retractor. The lateral movement of the anesthetized patient can
make the delicate sewing or cutting of the surgical procedure more
challenging. Therefore, it is advantageous to have a stabilizing
means in conjunction with the air mattress to prevent inadvertent
lateral movements of the patient on the mattress. In various
embodiments, the flexible side walls 80, 82 and to some extent the
flexible end walls 88, 90 in combination with the collapsible
inflatable chambers 170, may create a tension relieving hinge as
shown in FIG. 18. As the inflatable chambers 170 are deflated, the
person laying on the underbody support 3 mattress sinks into the
underbody support 3, depressing by the weight of the patient 180,
the upper surface (e.g., 160, 20 in FIG. 18). Depressing the upper
surface pulls the materials of the upper surface of the support
toward the center line. This causes the flexible side walls 80, 82
to hinge inward 190 as shown in FIG. 18. In this position, the top
of the flexible side walls 80, 82 are moved into a position
proximate the sides of the patient laying on the underbody support
3. The flexible side walls 80, 82 are relatively stiff compared to
the inflatable chambers 170 and when the side walls 80, 82 abut the
sides of the patient, they stabilize the patient preventing lateral
movement that may be caused by the surgeon leaning or pulling the
patient. By configuring the flexible side walls 80, 82 to hinge
inward 190 as shown in FIG. 18, they effectively stabilize the
patient from lateral movement.
[0105] Indentations 96 may advantageously be added to the inner
surface of the flexible side walls 80, 82 that correspond with the
rounded ends of the inflatable chambers 170. These indentations 96
in the foam flexible side walls 80, 82 create more space for the
hinging action of the flexible side walls 80, 82. The hinging
action that may result in strain relief for the materials of the
upper surface can be achieved by creating a space in the internal
region of the underbody support 3 into which the flexible side
walls 80, 82 can hinge inward. This space may be created by the
deflating of the volume-controlled, inflatable chambers 170. As the
inflatable chambers 170 collapse to a smaller volume creating an
empty space, the flexible side walls 80, 82 may hinge inwardly into
the newly formed space, providing strain relief for the materials
of the upper surface. Since pressure regulated inflatable chambers
may not be able to safely collapse to a partial volume, inflatable
mattresses with pressure control may not be able to create the
hinging action and strain relief of this invention.
[0106] In some embodiments as shown in FIGS. 19 and 20, the
underbody support 3 may include the assembly of inflatable chambers
170 of the instant invention, advantageously combined with a heater
assembly 1 (FIG. 20), for use when orthopedic surgery positioning
apparatuses are used. For example, one type of positioning
apparatus is a bean bag 520 (FIG. 20) which are large bags full of
Styrofoam "beans" that can be put under and then formed around at
least a portion of the patient (e.g., 244). A vacuum removes the
air from within the bean bag 520, locking the otherwise flexible,
malleable bag full of beans, into a firm shape that can be used to
hold the patient in a given position such as laying on their side
(lateral) 244 for hip surgery. The part of the stiffened bean bag
520 under the patient (e.g., 244) is a relatively hard, uneven,
lumpy surface that can cause significant localized pressure to be
applied to the patient's skin, causing pressure ulcers. Another
example is the well-known peg board positioner. In this case a
board with holes in it is placed on top of the mattress of the
surgical table. The patient is positioned on their side (laterally)
244 and held firmly in this position by pegs (not shown) that are
inserted into holes in the board and pressed firmly against the
front and back sides of the patient. Lying on a hard board
obviously increases the chances of pressure ulcers forming.
However, the surgeons need the patients to be well-secured and
stabilized, especially for operations such as hip replacements that
require sawing and hammering. Padding these hard and irregular
surfaces while preserving their ability to stabilize the patient,
is very difficult.
[0107] In some embodiments, it is advantageous to shorten the
inflatable chambers 170 (e.g., transverse inflatable chambers) so
that they extend over approximately the middle 2/3 of the table
width (e.g., central portion). This allows the patient who is lying
on their side, to be supported by the inflatable chambers but the
ends of the chambers do not interfere with the pegs of the peg
board or the vertical side walls formed by the bean bag. The weight
of the patient is supported by the inflatable chambers 170 but the
securing function of the positioning apparatuses is not
encumbered.
[0108] In some embodiments as shown in FIG. 19, the heater assembly
1 (FIG. 20) overlaying the underbody support 3, extends as lateral
portions 522 beyond the ends of the transverse array of inflatable
chambers 170. The flexible heater assembly 1, can be folded upward
along the front and back of the laterally positioned patient (e.g.,
244), without interfering with the security of the bean bag 520 or
peg board. In this position, the lateral portions 522 of the heater
assembly 1 are tucked between the patient and the positioning
apparatus (e.g., 170, 520), which holds the heater assembly 1
against the patient's skin (e.g., 244) for optimal heat
transfer.
[0109] In some embodiments, the algorithm for controlling the
heated mattress overlay (e.g., 3, 1, 170, 520) during certain uses,
such as orthopedic surgery, may be different than previously
described. For example, it may be advantageous to have the mattress
overlay (e.g., 3, 1, 170) fully deflated while positioning the
patient and forming the bean bag 520 or inserting the pegs in the
peg board. As shown in FIG. 20, the flexible heater assembly 1, is
folded up against the patient's front and back side and held in
that position by the bean bag 520 or peg board pegs.
[0110] Once the patient is positioned, the staff may start the
control algorithm, which actuates the air pump(s) to inflate the
inflatable chambers 170 from their collapsed condition. In the
collapsed or deflated condition, the most if not all of the
compression sensitive switches 200 will be in the closed position
due to the weight of the patient. Air is pumped into the inflatable
chambers 170 until the compression sensitive switch 200 in the most
depressed chamber opens. When this last switch 200 opens, the
electric current ceases flowing to the controller and the control
algorithm interprets this as evidence that the patient is totally
supported by air with no pressure points. No contact is occurring
between the dependent, weight bearing skin of the patient and the
hard surface of the bean bag 520 or peg board.
[0111] In some embodiments, the compression sensitive switches 200
in their "open" position (indicating that the patient is well
supported) then may become safety sensors. If due to movement of
the patient or inadvertent air loss from the system, the most
protruding part of the patient contacts the bean bag 520 or peg
board, the compression sensitive switch 200 at that location
closes, causing the control algorithm to add more air to the
inflatable chambers 170 until the compression sensitive switch 200
reopens indicating a safe condition. The control algorithm may also
sound an alarm to alert the surgical staff of the patient contact.
The compression sensitive switches 200 may also serve as a
documentation system for safety. If the control algorithm documents
that none of the compression sensitive switches 200 were closed for
a prolonged period of time during any operation, it can be assumed
that the patient was not subjected to prolonged pressure against
the skin. The documented safe condition may be automatically
charted in the electronic medical record (EMR), protecting the
surgical staff from liability should a pressure ulcer develop
later.
[0112] In some embodiments as in FIG. 21, one or more temperature
sensors 250 may be arranged or configured to be interposed between
the heated underbody support 3 and skin of the back or another
dependent body surface of the patient 232 during a temperature
measurement. The heated underbody support 3 may warm a peripheral
thermal compartment 234 of the patient 230 that is in contact with
the heated surface, creating a condition of near thermal
equilibrium (e.g., thermal equilibrium or in substantially thermal
equilibrium) between a core thermal compartment 236 and the
peripheral thermal compartment 234. In this situation, the
temperature of the skin of the patient that is in contact with the
heated underbody support 3 accurately reflects core body
temperature.
[0113] This may be accomplished by sensing the core temperature
using the technique described in U.S. Patent Application
2012/0238901, Non-invasive Core Temperature Sensor, filed Mar. 17,
2012, for example. In FIGS. 21 and 22, the heating element 10 of
the underbody support 3 may heat the skin of the patient's back 232
to a temperature slightly greater than core (Time AB) and then the
temperature of the heating element 10 (e.g., a set-point
temperature) may be reduced to a temperature equal or below the
core temperature of the patient. When the heating element 10
temperature is reduced or turned off (Time C), a temperature sensor
250 which may be a single temperature sensor 250 contacting the
body surface of the patient 232 that is interfaced with the
underbody support 3, may detect the decrease in skin temperature as
the excess heat from the peripheral thermal compartment 234
equilibrates by flowing into the core thermal compartment 236 (Time
CD). The temperature sensor 250 may be a single temperature sensor
250 and the body surface of the patient 232 may be the skin of the
back of the patient.
[0114] The curve of plotted skin temperatures in FIG. 22 shows an
early phase of rapid temperature reduction (Time CD), followed by a
phase of slow or even zero temperature reduction (Time DE). The
temperature at the point where the temperature curve transitions
from rapid reduction to slow reduction (Time D), may correlate with
the temperature at which equilibrium is reached between the
peripheral and core thermal compartments 234, 236 (Time DE). At
equilibrium, the measured peripheral temperature can reliably
correlate with core temperature. Alternately, the temperature may
be recorded at a predetermined time after the heater temperature is
reduced (Time E), for example between 1 and 5 minutes, when
equilibrium between the peripheral compartment 234 and the core
compartment 236 of the patient can be assumed to have been
reached.
[0115] In some embodiments, determining when the equilibrium has
been reached between the peripheral compartment 234 core
compartment 236 may be determined by calculations calculated at
regular intervals or on an ongoing basis rather than at a
predetermined time. For example, the rate of temperature change
(dT/dt) of the peripheral compartment 234 falling below a rate of
temperature change threshold may be used to indicate that
equilibrium has essentially been reached and the temperature may be
read. In some embodiments, a comparison of a first rate of change
over a first time period, to a second rate of change over a second
time period falling below some value (e.g., percent change or the
difference between the first rate of change and the second rate of
change) may indicate that equilibrium has essentially been
reached.
[0116] The temperature sensor 250 may be a thermistor or
thermocouple mounted on a thermally insulating material 252, such
as a disc of foam. The thermally insulating material 252 may be
many sizes and shapes but may optionally be between 1/2-1 inch in
diameter and may be 1/8-3/8 inch thick. The thermally insulating
material 252 may thermally insulate the temperature sensor 250 from
direct thermal contact with the heating element 10 (e.g., low mass
thermal heater). The temperature sensor 250 may be placed so that
it is directly contacting the body surface of the patient 232 and
is thus positioned between the body surface of the patient 232 and
the underbody support 3. For example, the temperature sensor 250
may be in contact with the skin of the back of the patient 232.
Although any other suitable skin surface may be used. The thermally
insulating material 252 that may be attached to the temperature
sensor 250 may be interposed between the temperature sensor 250 and
the heating element 10, minimizing the direct influence of the
heating element 10 on the temperature sensor 250. In some
embodiments, the one or more temperature sensors 250 are not
interposed as previously described, but rather is surrounded (e.g.,
about its diameter), by the heated underbody support 3.
[0117] When first used, such as at the beginning of a surgical
procedure, the peripheral thermal compartment 234 may be much
cooler than the core thermal compartment 236 (Time A), and the
temperature of the heating element 10 may be raised well above the
normal safe operating temperature for a heated support, for a short
time. This heats the peripheral thermal compartment 234 faster
(Time AB), allowing a faster initial temperature recording and more
rapid onset of effective patient warming. For example, if the
normal safe operating temperature for a heated underbody support 3
is 40.degree. C., the underbody support may be initially heated to
45.degree. C. for 5-15 minutes and then automatically reduced to
the normal safe operating temperature of 40.degree. C.
[0118] Another way to approximate core temperature utilizes the
fact that the heater assembly 1 of the underbody support 3 cannot
be significantly warmer than the core thermal compartment 236 and
not cause thermal injuries. In this condition, if the temperature
sensor 250 is in contact with the skin of the patient's back 232
and the temperature sensor 250 is thermally insulated 252 from
direct contact with the heating element 10 and/or heater assembly
1, the core thermal compartment 236 temperature can be approximated
once the peripheral thermal compartment 234 has been warmed and
allowed to be brought into equilibrium with the core thermal
compartment 236 temperature.
[0119] The temperature monitor may include a power supply switch to
facilitate the steps of heating and rapid cooling of the heating
element 10, and thus the heater assembly 1. For example the power
supply switch can supply power to the heater assembly 1 to control
the heating element 10 (e.g., low thermal mass heater) to a
temperature that is greater than core thermal compartment
temperature 236. Then the heating element 10 temperature rapidly
reduces to a temperature that is less than the core body
temperature 236 when the power supply switch cuts off power to the
heating element 10. It may be preferable to discontinue power to
the heating element 10, however, in some embodiments, the power may
be substantially discontinued rather than completely discontinued.
For example, the power may be reduced by 90%, or the cycle time
between power supplies may be reduced by 90%.
[0120] An alternative way which may be used to determine core
temperature is for the temperature monitor to have two temperature
sensors (e.g., 250) separated by a small piece of thermal
insulation, in a construction known as a "heat-flux transducer,"
for example. The first temperature sensor 250 in contact with the
body surface of the patient 232 may reflect the patient's
temperature and the second temperature sensor (not shown) in
contact with the heating element 10 may reflect the heating element
10 temperature. The heating element 10 temperature may then adjust
until the two temperature sensors equal each other and reach
equilibrium. At that point there may be zero heat flow (heat flux)
and the patient's core temperature may be equal to the skin
temperature. This technique may reduce the heating effectiveness of
the surface of the heater assembly 1, but it will allow continuous
temperature monitoring.
[0121] Various temperature monitoring techniques described herein
use the heating element 10 of the underbody support 3 to
equilibrate the temperature of peripheral thermal compartment 234
with the temperature of the core thermal compartment 236. These
temperature monitoring techniques may also efficiently use the
heating element 10 and underbody support 3 itself as the thermal
insulation between the patient and the environment.
[0122] The temperature monitoring techniques of the instant
invention may rely on excess heat being added to the peripheral
thermal compartment 234. The excess heat may then be allowed to
flow into the cooler core thermal compartment 236 (Time CD) until
thermal equilibrium is reached (Time DE). This is different than
all other core body temperature monitors that attempt to measure
the temperature of the heat flowing out from the core thermal
compartment 236 to the peripheral thermal compartment 234 and then
to the skin (e.g., 232).
[0123] In some embodiments, the underbody support 3 includes a
grounding electrode for electro-surgical equipment. As shown in
FIGS. 2-4, the grounding can be accomplished by placing an
electrode 254 under the patient but not in direct electrical
contact with the patient. Electrode 254 may be a large electrode.
This can create a condition of capacitive coupling for grounding
the RF electrical current without actually touching the patient.
These capacitive coupling grounding electrodes 254 are well known
in the art. For example, U.S. Pat. Nos. 6,053,910 and 6,214,000
describe embodiments which may be used. However, these capacitive
coupling electrodes have been generally utilized as mattress
overlays which are inconvenient and require extra cleaning.
Further, these electrodes may be embedded into a gel pad, resulting
in an overlay that is heavy, cumbersome and interferes with optimal
pressure off-loading.
[0124] To avoid these problems, various embodiments include
capacitive coupling grounding electrode 254 in the stack
construction of the underbody support 3. The preferred location for
the capacitive coupling electrode 254 in the stack is under the
compressible material layer 20; however, other locations are
anticipated. The electrode 254 may include or consist of a sheet of
flexible and preferably stretchable electrically conductive fabric
that extends substantially across the entire area of the underbody
support 3. The stretchable fabrics may be woven twills or knits,
for example. If a non-stretchable or less stretchable fabric such
as woven nylon or polyester is chosen, care must be taken in the
design to avoid anchoring the non-stretchable fabric to the
periphery of the underbody support 3 in order to prevent
"hammocking" Various methods of preventing hammocking have been
discussed in other applications already incorporated herein.
[0125] The electrode 254 may be a conductive fabric electrode that
may be coated with silicone rubber, as described in U.S.
Provisional Patent Application 61/812,987, to prevent electrical
contact with the other electrically conducting components while
maintaining optimal flexibility and stretchability. In some
embodiments, the conductive fabric grounding electrode 254 may be
the heating element 10 (e.g., conductive fabric heater material,
fabric or film). Proper grounding of the heater material (e.g.,
heating element 10) may provide electrosurgical capacitive
grounding without the need for an additional layer of conductive
material.
[0126] To clean and sanitize medical equipment, hydrogen peroxide
(H.sub.2O.sub.2) disinfecting solutions have recently been
introduced into the operating room and hospital. H.sub.2O.sub.2 is
a well-known, powerful oxidizing agent that kills bacteria and
viruses in a mechanical way that cannot lead to resistant strains.
The oxidation reaction causes the H.sub.2O.sub.2 to break down into
water and oxygen, two harmless, or less harmless by-products. The
problem is that H.sub.2O.sub.2 vapor is also highly oxidizing for
electrical components, including flexible heater materials
(including polypyrrole), metal bus bars and conductive metal
coatings such as silver on fabric or thread. There is a need for
better protection of the sensitive electrical components from
oxidation by H.sub.2O.sub.2 and other oxidizers.
[0127] In some embodiments, urethane film may be used as the shell
42, 44 material for the underbody support 3 or related blankets,
because of its strength, flexibility durability and response to
heat sealing. Unfortunately, although urethane film may be good for
providing a water-resistant and encapsulating shell 42, 44,
urethane film is relatively permeable to hydrogen peroxide vapors,
allowing the highly oxidizing vapors to enter the underbody support
3 or a related heated electric blanket. Once inside, the peroxide
vapors attack any oxidizable material. These vapors can cause
oxidation and failure of electrical components, especially
polypyrrole. Other plastic films such as PVC are much less
permeable to peroxide vapor than urethane. Since peroxide is
becoming more and more common as a disinfectant for operating room
and other hospital use, a way of protecting vulnerable internal
components from oxidation due to peroxide is needed.
[0128] In some embodiments, the underbody support 3 or the related
heated electric blankets incorporate certain materials that can
protect the polypyrrole heater (e.g., heating element 10) and other
oxidizable electrical components from oxidizing agents such as
hydrogen peroxide (H.sub.2O.sub.2) disinfecting solutions. In some
embodiments, a catalyst to accelerate hydrogen peroxide
decomposition may be coated on or impregnated into an element
within the shell 42, 44, or on the interior surface of the shell
42, 44.
[0129] In some embodiments, sacrificial materials may be included
in the internal construction that can be preferentially oxidized.
Sacrificial materials may be organic materials such as cellulose.
For example, sacrificial materials such as one or more sacrificial
layers 256 of cotton, linen or paper, as shown in FIGS. 2-4, may be
added to the inside of the underbody support 3 or the related
heated electric blanket so that the peroxide vapors preferentially
attack and oxidize the sacrificial material. Other oxidizable
sacrificial materials may be used. In the process of oxidizing
these sacrificial materials, the peroxide breaks down into inert
(e.g., less corrosive, less problematic) water and oxygen before it
can attack the electrical components. The catalyst for accelerating
hydrogen peroxide decomposition may decompose all, substantially
all, or the majority of the hydrogen peroxide vapors before they
reach the electrical components, depending on how the catalyst is
incorporated into the particular apparatus.
[0130] In some embodiments, materials that are known to be
catalysts for the breakdown reaction of peroxide to water and
oxygen may be added. For example, manganese dioxide (MnO.sub.2)
powder may be added to one or more of the sacrificial layers 256 in
FIGS. 2-4, or the compressible material layer 20, the inside
surface of the shell 42, 44, or adhered directly to any suitable
component of the heater assembly 3 by an applied coating, by
impregnation into, by adhesive, or by any other suitable
process.
[0131] In some embodiments, the insoluble manganese dioxide powder
may be suspended in water and the sacrificial layer 256 of fabric
or foam can be dipped in this water/manganese dioxide powder
suspension to evenly disperse the powder throughout the sacrificial
layer 256 of fabric or foam when the water evaporates. In some
embodiments, a small amount of methyl cellulose can be added to the
water/manganese dioxide powder suspension in order to increase the
duration of the suspension time of the powder in water. The small
amount, or sufficient amount of methyl cellulose to increase the
viscosity of the water and manganese dioxide suspension to between
10 and 120 centipoise. The methyl cellulose may also act as a
binding agent, improving adherence of the manganese dioxide powder
to the fabric, foam or other material. Other binding agents, and/or
suspension improvers besides methyl cellulose may be used. Adding
too much binding agent (e.g., greater than 120 centipoise) can
cause the binding agent to completely encapsulate the manganese
dioxide powder when it dries, and too little (e.g., less than 10
centipoise) will not hold the powder in suspension very long. Other
carriers besides water may also be used.
[0132] In some embodiments, the one or more sacrificial layers 256
of manganese dioxide impregnated fabric or compressible material
layer 20 may be added to the inside of the underbody support 3 or
related heated electric blanket so that the catalyst can
preferentially attack the peroxide vapors and neutralize them to
water and oxygen, before they can damage the electrical components.
Other liquids are anticipated for suspending the manganese dioxide
powder. Examples of catalysts that can be used in place of
manganese dioxide powder include: silver, platinum and transition
metal salts. Other catalysts may also be used. In some embodiments
the catalysts may be added to another feature of the underbody
support 3 or the related heated electric blanket, and to a material
other than fabric or foam.
[0133] The effectiveness of these measures for preventing the
oxidation and degradation of the heater fabric and other mattress
or blanket components by peroxide vapor were tested. During testing
similar squares of heater material with bus bars attached were
sealed into shells of urethane film. The heaters were then placed
into a chamber that continuously exposes the shell to peroxide
vapor. Over the course of 9-12 days, the change in resistance of
the heater material was measured and correlated with the
degradation of the conductance of the heater material. Over the
course of 9 days of exposure to peroxide vapor, the resistance of
unprotected polypyrrole heater material increased from 58.4 to
238.2 ohms on the square. The significant increase in resistance,
indicates that the conductivity of the unprotected conductive
heater material (e.g., heating element 10) was rapidly degraded by
the peroxide vapors.
[0134] Over the course of 12 days of exposure to peroxide vapor,
the resistance of heaters that included two layers of sacrificial
cotton fabric inside the shell, increased from 53.5 to 84.8 ohms on
the square. Over the course of 12 days of exposure to peroxide
vapor, the resistance of heaters that included two layers of
polyester fabric impregnated with manganese dioxide inside the
shell, did not increase resistance at all (52.8 to 52.8 ohms on the
square). The MnO.sub.2 was very effective as a catalyst
neutralizing the peroxide vapor before it could destroy the heater.
The sacrificial layer of cotton fabric was also quite effective in
protecting the heater but less so than the MnO.sub.2.
[0135] This disclosure of using MnO.sub.2 or sacrificial cellulose
layers to protect oxidizable components, especially electrical
components, is not limited to underbody supports 3 and heating
blankets. In some embodiments, other medical equipment (e.g.,
apparatus) including electrical components such as patient
monitors, patient monitoring electrodes, patient monitoring sensors
and medical equipment control circuits may be protected from
oxidation and damage by peroxide vapors or liquid, by incorporating
MnO.sub.2 or sacrificial cellulose layers into the equipment, as
disclosed in this application.
[0136] In some embodiments, the underbody support 3 uses the fact
that the patient sinks into the underbody support 3 and achieves
maximal body surface contact with the underbody support 3, to aid
in preventing the patient from sliding off of the surgical table
412 when placed in the steep Trendelenburg position (head down).
This is in contrast to a traditional mattress wherein the torso of
the patient may only contact the mattress at the buttocks and
shoulders. This relatively small contact area means that the
coefficient of friction must be much greater in order to prevent
the patient from slipping off of the mattress when placed in the
Trendelenburg position. Various embodiments allow contact with the
entire back of the patient and curve up along their sides allowing
a much lower coefficient of friction to prevent slipping.
[0137] The underbody support 3 may include elements for anchoring
the support to the surgical table 412. In some embodiments, the
elements for anchoring may be a Velcro attachment between the upper
surface of the surgical table 412 and the lower surface of the
underbody support 3. In some embodiments, the elements for
anchoring may be a strap attachment between the side of the
surgical table 412 and the underbody support 3. The lower surface
may also be called the table interface surface.
[0138] In some embodiments, a sheet of fabric that has been at
least partially coated on both sides with high-friction plastic or
rubber, or a material having similar characteristics, may be
interposed between the patient and the support in order to increase
the coefficient of friction. An example of this may be PVC or
silicone that may be applied as a three dimensional pattern or
three dimensional raised dots, onto a fabric (e.g., friction
enhancing elements). The high-friction plastic or rubber that may
be in the form of a pattern or dots, "grip" the upper surface of
the underbody support 3 on one side and the back of the patient on
their other side, dramatically increasing the coefficient of
friction between the patient and the underbody support 3 surface,
preventing the two from slipping against each other. Alternately,
the high-friction plastic or rubber forming a pattern or dots may
be applied directly to the upper surface of the underbody support
3. The upper surface may also be called a patient interface
surface.
[0139] In some embodiments, a method of supporting and restricting
a sliding motion of a patient on a surgical table including the
features described previously herein includes (i) providing an
underbody support configured to support the patient on the table,
the underbody support including a compressible material layer
having an upper surface configured to face the patient opposite a
base layer having a lower surface configured to face the surgical
table; (ii) coupling the underbody support to the surgical table;
(iii) placing a layer of material between the upper surface of the
underbody support and the patient, the layer of material comprising
friction enhancing elements on both sides of the layer of material,
wherein the layer of material is configured to grip both the
underbody support and the patient to prevent the patient from
inadvertently slipping off the underbody support; and (iv)
positioning the patient on the underbody support.
[0140] In some embodiments of the method, the layer of material may
be a draw sheet that is configured to be positioned over the
underbody support for lifting the patient. In some embodiments the
layer of material including friction enhancing elements includes
PVC or silicone.
[0141] In some embodiments of the method, positioning the patient
on the underbody support comprises positioning the patient in the
head down Trendelenburg position, the friction enhancing elements
being configured to reduce sliding of the patient relative to the
underbody support when the patient is positioned on the underbody
support in the head down Trendelenburg position.
[0142] In some embodiments of the method, the underbody support
includes two side walls; two end walls; a base layer having a lower
surface configured to face the table and a base layer perimeter;
the compressible material layer may have a compressible material
layer perimeter, the compressible material layer bonded to the two
side walls and to the two end walls about the perimeter of the
compressible material layer; and one or more inflatable chambers,
wherein the two side walls and two end walls are fastened to the
perimeter of the base layer, and the base layer, the two side
walls, the two end walls, and the compressible material layer form
a box-like structure made of flexible foam. In some embodiments the
box-like structure surrounds the one or more inflatable
chambers.
[0143] In some embodiments of the method, the upper edges of the
two flexible side walls can hinge inward in response to the weight
of a patient depressing the central region of the layer of
compressible material, and the hinging inward of the flexible side
walls allows the layer of compressible material to deform maximally
while accommodating the patient without creating a hammock
effect.
[0144] In some embodiments of the method, the upper edges of the
two flexible side walls can hinge inward in response to the weight
of a patient depressing the central region of the layer of
compressible material, and the hinging inward of the flexible side
walls allows the tops of the flexible side walls to substantially
abut the sides of the patient stabilizing the patient against
inadvertent lateral movement.
[0145] In some embodiments of the method, the method may further
include: placing the patient in the head down Trendelenburg
position, and fastening shoulder straps that extend from a head end
portion of the underbody support over the shoulders of the patient
to a central portion of the underbody support or the surgical table
when the patient is in the head down Trendelenburg position to
secure the patient to the surgical table.
[0146] In some embodiments as shown in FIGS. 23 and 24, a cushion
400 (e.g., foam cushion) may be anchored to the head end of the
support surface 410 and extend onto the mattress portion at the
head end of the surgical table 412. The cushion 400 may optionally
be substantially yoke-shaped extending transversely across the
surgical table 412, with a depression in the middle to accommodate
a patient's head 240 and neck 242 and with raised lateral portions
402 to engage the patient's shoulders 238. The raised lateral
portions 402 interface with a patient's shoulders 238, to
effectively prevent the patient from slipping off of the head end
of the surgical table 412. Other cushion shapes may also be used.
The cushion 400 may be formed of foam or any other suitable
material.
[0147] In some embodiments, the yoke-shaped cushion 400 may also
include shoulder straps 404, much like the shoulder straps of a
backpack, may extend substantially from a yoke-shaped cushion 400
over the front of the patient's shoulders 238 and anchor on side
rails 414 of the surgical table 412 or other surface. For example,
at a central portion of the underbody support 3. Other strap
configurations may be used for anchoring the yoke-shaped cushion
400 to the side rails 414 of the surgical table 412. The anchoring
shoulder straps 404 may be adjusted in length as well as anchored
at different locations along the side of the surgical table 412, or
another part of the surgical table 412 allowing the patient to be
repositioned along the surgical table 412 if necessary. In some
embodiments, the yoke-shaped cushion 400 may be attached to and
anchored to the head end of the underbody support 410. In some
embodiments, the yoke-shaped cushion 400 may also include one or
more cushion inflatable chambers to minimize point pressure on the
patient's shoulders 238. The cushion inflatable chambers of the
yoke-shaped cushion 400 may be similar or different to inflatable
chambers 170 previously disclosed.
[0148] In some embodiments as shown in FIGS. 25-27, the underbody
support 3 includes a layer of water-circulating channels 500 that
optionally cover substantially the entire surface area of the
underbody support 3. The layer of water-circulating channels 500
may be located near the patient surface of the underbody support 3,
or the yoke-shaped cushion 400, including the raised lateral
portions 402. Cold water may optionally be circulated through
water-circulating channels 502 for inducing therapeutic
hypothermia. Hypothermia has been shown to be neuro-protective for:
closed head injuries; post successful CPR for heart attacks and for
some strokes. Therapeutic cooling has is also useful for heat
stroke and certain hypermetabolic states like malignant
hyperthermia.
[0149] The water-circulating channels 502 may be molded into the
two film layers 510, 512 of polymeric film that are then sealed
together 504 (e.g., hermetically sealed) between the
water-circulating channels 502. This construction of a layer of
water-circulating channels 502 may be done according to methods
known in the art. Relatively thick PVC or urethane film may be used
for this purpose. The sealed portions 504 may be created using RF,
ultrasound, heat, or any other suitable method of sealing. This
construction results in a flexible layer of water-circulating
channels 500 that can be positioned near the upper surface of the
underbody support 3. Since the film layers 510, 512 forming the
water-circulating channels 502 are relatively thick, they may also
be relatively resistant to collapse from supporting the weight of a
patient.
[0150] In some embodiments, longitudinal slits are made through the
sealed portions 504 of the layer of water-circulating channels 500.
These longitudinal slits allow lateral expansion of the layer of
water-circulating channels as the layer is deformed by the weight
of a patient. The lateral expansion of the layer of
water-circulating channels 500 due to the slits may facilitate the
accommodation of the patient into the underbody support 3, while
preventing "hammocking."
[0151] An advantage of adding a layer of water-circulating channels
500 to the inflatable underbody support 3 of various embodiments is
that the patient sinks further into this underbody support 3 than
into a foam mattress, for example. By sinking into the underbody
support 3, the underbody support 3 may curve up along side the
patient forcing the water-circulating channels 500 into close
opposition to the patient's skin over a much larger surface area
than can be accomplished with a foam mattress. The greater surface
area in contact with the cold water-circulating channels 500
results in more effective heat or cold transfer. Therefore, the
combination of the maximally accommodating underbody support 3 of
various embodiments with a layer of water-circulating channels 500
is both unique and advantageous.
[0152] In some embodiments as shown in FIG. 26, the upper surface
of the layer of water-circulating channels 500 may have a coating
of gel 514 to fill in the uneven surface created by the molded
channels. The gel coating produces a relatively smooth upper
surface for contacting the patient while maintaining thermal
conductivity. Alternately, in some embodiments as shown in FIG. 27,
the molded channels are only molded into the lower film layer 512
of polymeric film. This leaves the upper film layer 510 of
polymeric film smooth for optimal contact with the patient.
[0153] Whereas particular embodiments of the invention have been
described for the purposes of illustration, it will be evident to
those skilled in the art that numerous variations of the details
may be made without departing from the invention as set forth in
the embodiments described herein.
* * * * *