UNDERBODY WARMING SYSTEM WITH FOCAL COOLING

An underbody warming system may include a skin contacting surface configured to be positioned on the skin of a user. A plurality of thermoelectric devices may be provided. A first thermoelectric device of the plurality of thermoelectric devices may have a first temperature to create a first temperature gradient between the skin and the first thermoelectric device. A second thermoelectric device of the plurality of thermoelectric devices may have a second temperature different from the first temperature to create a second temperature gradient between the skin and the thermoelectric device. A first flow path may be configured to allow heat to flow between the skin and the first thermoelectric device. A second flow path may be configured to allow heat to flow between the skin and the second thermoelectric device.

BACKGROUND

The subject matter disclosed herein relates generally to an underbody patient warming device. More specifically, the present disclosure is related to a patient warming device having an array of thermoelectric devices to prevent ischemic pressure injuries.

Pressure injuries and deep tissue injury may be caused by excessive pressure, surface shear, moisture, and temperature on a patient's skin over time, for example when a patient uses a hospital bed or other patient support apparatus for an extended period. Protective barrier dressings (e.g., bandages) or surfaces (e.g., mattresses) may be used to prevent pressure injuries by reducing friction, surface shear, and/or moisture on the patient's skin. Cooling of the patient's skin may have a significant impact on prevention and treatment of pressure injuries and tissue damage. Pressure injuries are caused primarily by ischemia which is a combination of tissue deformation (pressure) causing occlusion and reduced supply versus temperature (increased demand). Reduced temperature may reduce moisture accumulation on the skin. Also, reduced temperature reduces tissue metabolic rate, which also reduces the severity of tissue damage. As a result, cooling the patient's skin may allow the skin to tolerate a given pressure for a longer time period. Researchers have hypothesized that if tissue temperature could be reduced to approximately 60° F., the tissue could survive occlusion-level pressures near indefinitely. Existing underbody warming systems heat the bony prominences in contact with the warming surface and thus increase the risk of pressure injury development. Micro-climate management (MCM) layers capable of reducing the temperature of patient support surfaces (e.g. mattresses) are known, but may be incompatible with some underbody warming systems. Underbody warming reduces interference with procedures and access to the body. Unfortunately, existing underbody warming solutions have been shown to increase pressure injuries at the bony prominences.

SUMMARY

According to one aspect of the disclosed embodiments, an underbody warming system may include a skin contacting surface configured to be positioned on the skin of a user. A plurality of thermoelectric devices may be provided. A first thermoelectric device of the plurality of thermoelectric devices may be positioned adjacent a first section of the skin contacting surface and may have a first temperature different from the temperature of the skin being contacted by the first section of the skin contacting surface to create a first temperature gradient between the skin and the first thermoelectric device. A second thermoelectric device of the plurality of thermoelectric devices may be positioned adjacent a second section of the skin contacting surface and may have a second temperature different from the first temperature and the temperature of the skin being contacted by the second section of the skin contacting surface to create a second temperature gradient between the skin and the thermoelectric device. An insulator may be positioned between the first thermoelectric device and the second thermoelectric device. A first flow path may be configured to allow heat to flow between the skin and the first thermoelectric device. A second flow path may be configured to allow heat to flow between the skin and the second thermoelectric device. In some embodiments, a cushion layer that may include a thermally conductive material may be positioned between the skin contacting surface and the plurality of thermoelectric devices.

In some embodiments, at least one pressure sensor may detect a bony prominence of the user. The second thermoelectric device may be positioned at the bony prominence of the user. A controller may selectively operate the second thermoelectric device based on data from the pressure sensor.

Optionally, the first temperature may be greater than the second temperature. The first temperature gradient may provide heat to the skin being contacted by the first section of the skin contacting surface. The second temperature gradient may remove heat from the skin being contacted by the second section of the skin contacting surface. The second section of the skin contacting surface may be configured to be positioned at a bony prominence of the user.

Alternatively or in addition to, at least one of the plurality of thermoelectric devices may include a thermometer to monitor a temperature of at least one of the thermoelectric device and a temperature of the skin. A controller may alter a current to the thermoelectric device in response to the temperature monitored by the thermometer.

It may be desired that the thermoelectric device includes a channel to circulate fluids through a cold sink of the thermoelectric device. A thermal exchanger may circulate fluids to and from the thermoelectric device. The skin contacting surface may be disposed within a surgical platform. A power supply may be positioned on the surgical platform.

According to another aspect of the disclosed embodiments, an underbody warming system may include a skin contacting surface configured to be positioned on the skin of a user. A plurality of thermoelectric devices may be provided. A first thermoelectric device of the plurality of thermoelectric devices may be positioned adjacent a first section of the skin contacting surface and may have a first temperature different from the temperature of the skin being contacted by the first section of the skin contacting surface to create a first temperature gradient between the skin and the first thermoelectric device. The first temperature gradient may provide heat to the skin being contacted by the first section of the skin contacting surface. A second thermoelectric device of the plurality of thermoelectric devices may be positioned adjacent a second section of the skin contacting surface and may have a second temperature different from the first. temperature and the temperature of the skin being contacted by the second section of the skin contacting surface to create a second temperature gradient between the skin and the thermoelectric device. The second temperature gradient may remove heat from the skin being contacted by the second section of the skin contacting surface. A first flow path may be configured to allow heat to flow between the skin and the first thermoelectric device. A second flow path may be configured to allow heat to flow between the skin and the second thermoelectric device. A cushion layer may be positioned between the skin contacting surface and the plurality of thermoelectric devices. In some embodiments, the second section of the skin contacting surface may be configured to be positioned at a bony prominence of the user.

Optionally, at least one of the plurality of thermoelectric devices may include a thermometer to monitor a temperature of at least one of the flexible substrate and the skin. A controller may alter a current to the thermoelectric device based on the temperature monitored.

It may be desired that the thermoelectric device includes a channel to circulate fluids through a cold sink of the thermoelectric device. A thermal exchanger may circulate fluids to and from the thermoelectric device. The skin contacting surface may be disposed within a surgical platform. A power supply may be positioned on the surgical platform.

According to yet another aspect of the disclosed embodiments, a method of providing localized cooling to the skin of an underbody warming system user includes positioning a skin contacting surface on the skin of the user. The method may also include positioning a first thermoelectric device adjacent a first section of the skin contacting surface. The method may also include altering a temperature of the first thermoelectric device to create a first temperature gradient between the skin and the first thermoelectric device. The method may also include positioning a second thermoelectric device adjacent a second section of the skin contacting surface. The method may also include altering a temperature of the second thermoelectric device to create a second temperature gradient between the skin and the second thermoelectric device. The method may also include providing a first flow path through the first thermoelectric device to allow heat to flow between the skin and the first thermoelectric device. The method may also include providing a second flow path through the second thermoelectric device to allow heat to flow between the skin and the second thermoelectric device.

In some embodiments, the method may include positioning a cushion layer between the skin contacting surface and the first thermoelectric device. The method may also include positioning the cushion layer between the skin contacting surface and the second thermoelectric device.

Optionally, the method may include altering the temperature of the first thermoelectric device to a temperature that is greater than the temperature of the second thermoelectric device. The method may also include providing heat to the skin being contacted by the first section of the skin contacting surface through the first temperature gradient. The method may also include removing heat from the skin being contacted by the second section of the skin contacting surface through the second temperature gradient. The method may also include positioning the second section of the skin contacting surface at a bony prominence of the user.

It may also be desired that the method include monitoring a temperature of the skin. The method may also include altering a current to the thermoelectric device in response to the temperature monitored by the thermometer. The method may also include circulating fluids from a thermal exchanger through a cold sink of the first thermoelectric device. The method may also include circulating fluids from a thermal exchanger through a cold sink of the second thermoelectric device.

Alternatively, or in addition to, the method may include disposing the skin contacting surface within a surgical platform. The method may also include disposing a power supply on the surgical platform.

DETAILED DESCRIPTION

The embodiments described herein relate to devices, systems and methods to warm a patient, while reducing the risk of pressure injuries by cooling the tissue over the bony prominences. The device also allows unrestricted access to the surgical site which is usually facing upward toward the surgeon's field of view. Generally, underbody warming systems heat the bony prominences in contact with the warming surface, thereby increasing the risk of pressure injury development. The devices, systems and methods described herein use focal cooling of the bony prominences to reduce pressure injuries originating in the operating room, which are estimated to account for 40% of hospital-acquired pressure injuries. In other embodiments, the devices, systems and methods described herein may be used outside of the operating, e.g. in a patient room, an ambulance, an emergency transport, or a homecare setting to name a few non-limiting examples.

The described devices, systems and methods are not limited to the specific embodiments described herein. In addition, components of each device, system and/or steps of each method may be practiced independent and separate from other components and method steps, respectively, described herein. Each component and method also can be used in combination with other systems and methods.

Referring toFIGS. 1-2, a surgical platform10includes a plurality of patient support cushions12, which are the areas that have the highest interface pressure with a patient. The cushions12include a skin contacting surface14that contacts the skin of the patient. The cushion12may include a thermally conductive material. An underbody warming device16is positioned within at least one of the cushions12. It should be noted that the underbody warming device16may be positioned on any area of the surgical platform10that requires warming for a patient, e.g. the upper back, the buttocks, the legs, and/or the arms. A heat exchanger module18is positioned within the underbody warming device16and includes a plurality of thermoelectric coolers20(described in detail with respect toFIGS. 4-6). InFIG. 2, the heat exchanger module18is illustrated as being positioning within the cushion12. Optionally, the heat exchanger module18may be positioned on top of the cushion12and retained on the cushion12with straps. In some embodiments, the heat exchanger module18may be strapped to the patient. the As described in more detail below, the thermoelectric coolers20may be heated to provide heat to a user and/or the thermoelectric coolers20may be cooled to provide selective cooling to the user to prevent pressure injuries. The thermoelectric coolers20are be powered through removable cords that plug into a thermal controller22on a support column24of the surgical platform10. Alternatively, power busses26may be integrated into table rails28of the surgical platform10to eliminate the need for cords, as illustrated inFIG. 2. The surgical platform10may include a plurality of power buses26positioned adjacent the heat exchanger modules18within the surgical platform10. Alternatively, the power buses26may extend a length of the rail28and include a plurality of ports to receive cables from the individual heat exchanger modules18. The warming thermoelectric coolers20may be attached to the unsupported areas of the patient with elastic straps. The heating thermoelectric coolers20should cover the width of the surgical platform10. The length should reach from just above the shoulders to the foot section. The cooling thermoelectric coolers20are positioned within the same thermoelectric cooler array, e.g. in the pelvic region, occiput region or heel region.

The controller22powers the heat exchanger module18to heat and cool the thermoelectric coolers20. The controller22may be a proportional integral derivative controller that provides a feedback loop between the heat exchanger module18and the controller22. For example, temperature sensors30may monitor a temperature of the patient's skin adjacent each thermoelectric cooler20. Optionally, the temperature sensors30may monitor a temperature of the thermoelectric cooler20. A signal indicative of the temperature of each thermoelectric cooler20is delivered to the controller22. The controller22may then alter a current to any number of thermoelectric cooler20to alter the temperature of the thermoelectric coolers20. The controller22is illustrated as being physically integrated into a patient support apparatus10; however, the controller22may be a standalone unit that is electrically coupled to the heat exchanger module18.

In some embodiments the underbody warming device16may be used with a stretcher that is used to transport patients to the operating room and/or post-anesthesia care unit. In some embodiments the underbody warming device16may be used in the emergency room on stretchers and procedural chairs for hypothermic patients, in emergency transports, e.g. ambulances, planes, helicopters, or for use with Xport boards and stretchers. The underbody warming device16may also be used on the patient floors to optimize patient comfort. The underbody warming device16may also be utilized with wheelchairs, chairs, and vehicle seats.

Referring now toFIG. 3, a surgical platform50is illustrated with a patient52positioned on the cushions54of the surgical platform. A heat exchanger module18is positioned within the cushions54below the patient's back and buttocks. A thermal exchanger58for circulating liquids to and from the heat exchanger module18is coupled to a stand60of the surgical platform50. Notably, the thermal exchanger58may be positioned at any location within the surgical room and fluidly coupled to the heat exchanger module18. The heat exchanger module18includes a heating zone70and a cooling zone72. The heating zone70is positioned adjacent the patient's back and the cooling72is positioned adjacent the patient's buttocks. The heating zone70includes a plurality of thermoelectric coolers20that are configured to provide heat to the patient's skin, specifically, the section of the patient's skin positioned on the heating zone70. The cooling zone72includes a plurality of thermoelectric coolers20that are configured to removes heat from the patient's skin, specifically, the section of the patient's skin positioned on the cooling zone72. For example, in the illustrative embodiment, the heating zone70provides heat to the patient's back and the cooling zone72removes heat from the patient's buttocks.

Generally, the cooling thermoelectric coolers20are positioned under the bony prominences, e.g. those around the pelvis including the sacrum, trochanters, ischial tuberosity, and iliac crest, as this area accounts for approximately 55% of pressure injuries originating in the operating room. Other bony prominences may include ankles, greater trochanters, iliac crest, elbows, knees, occiput, nose, forehead and other facial bony prominence, heels, and scapulae, clavicle. In one embodiment, pressure mapping is utilized to detect bony prominences and other areas with a high risk of developing injuries where cooling would be focused. Pressure sensors within the heat exchanger module18monitor a degree of pressure being applied to each thermoelectric cooler20. The controller22detects areas of high pressure. High pressure may be determined as a function of the patient's weight, the patient's size, and/or the patient's position. By monitoring areas of high pressure, the controller22determines where the patient's bony prominences and other areas of high risk are located. The controller22utilizes this information to selectively operate certain thermoelectric coolers20at the bony prominence as cooling thermoelectric coolers20. In some embodiments, if the patient is moved during the operation, the controller22may monitor changes in pressure to reconfigure the cooling thermoelectric coolers20.

Referring toFIG. 4, the heating zone70may partially surround the cooling zone72.FIG. 4illustrates the heating zone70having a first plurality74of thermoelectric coolers20configured to provide heat. The cooling zone72includes a second plurality76of thermoelectric coolers20configured to remove heat. The first plurality74of thermoelectric coolers20extend from a shoulder position78of the surgical platform to a buttocks position80of the surgical platform. The second plurality76of the thermoelectric coolers20are positioned adjacent the buttocks position80and isolated around a sacral position82of the surgical table where the patient's sacrum is positioned during surgery. Each of the thermoelectric coolers20is surrounded by an insulating material84, e.g. an insulating metal or polymer, and insulating gel, and/or an insulating fluid. The insulating material84facilitates limiting heat loss from the thermoelectric cooler20. In some embodiments, the first plurality74of thermoelectric coolers20may be collectively surrounded by an insulating material84. Likewise, the second plurality76of thermoelectric coolers20may be collectively surrounded by an insulating material84.

Referring now toFIGS. 5-6, the thermoelectric coolers20are used as direct cooling or heating agents to create normothermia, hypothermia, or hyperthermia in a patient. The thermoelectric cooler20includes a body100having a top102that provides a thermal gradient. The skin contacting surface14extends across the top102. The body100has a fluid inlet104and a fluid outlet106. A fluid channel108extends through the body100between the fluid inlet104and the fluid outlet106. Both the fluid inlet104and the fluid outlet106are fluidly coupled to the thermal exchanger58. The liquid that is passed through the fluid channel108acts as a thermal reference for the thermoelectric coolers20. Current is supplied by a controller to the thermoelectric coolers20to induce cooling or heating relative to the liquid. The liquid may be deionized water, e.g. deionized water with one or more additives to increase cooling performance, operational temperature zone, or corrosion properties, or another fluid with thermal conductivity properties. The thermoelectric coolers20operating as cooling devices remove heat from the user upon application of an applied electrical current. The thermoelectric coolers20may also be used as heating devices by reversal of the applied electrical current. Each thermoelectric cooler20includes a separate wired connection for an independent electrical current. Accordingly, some thermoelectric coolers20may be selectively used for cooling, and some thermoelectric coolers20may be selectively used for heating.

The controller22alters currents to each of the thermoelectric coolers20to control the temperature of each thermoelectric cooler20such that some of the thermoelectric coolers20are in cooling mode and others are in heating mode. A feedback loop on the controller22minimizes temperature variability. The cooling thermoelectric coolers20may be set to reach and maintain temperature at a point that reduces the risk of pressure injuries. In some embodiments, the optimal cooling temperature of the skin may be between approximately 30° C. and 33° C. Cooling below 30° C. may provide greater protection against pressure injury development; however, the loss of warming arising from greater cooling may offset the relatively smaller gains attained from cooling below 30° C. For example, reducing skin temperature from 33° C. to 30° C. may lead to a greater reduction in pressure injury risk than moving from 30° C. to 27° C. All thermoelectric coolers20in the heat exchanger module18may be set to maintain a target temperature between approximately 15° C. and 42° C. For example, the thermoelectric coolers20that are not in a cooling mode may be set to a warming mode between approximately 33° C. to 42° C.

Referring toFIGS. 7-8, a simulation model150of human tissue including skin, fat, muscle, and bone demonstrates that it is possible to maintain local cooling that is thermally distinct from heating in the periphery and beyond. It should be noted that the simulation is an extreme case, as typical cooling only needs to be a few degrees below average skin temperature of 32.7° C. The simulation model150simulates human tissue having a thickness of 100 millimeters. As illustrated inFIG. 7, cooling can be applied to a localized region152of the model150, while heating is achieved in surrounding regions154of the model150. Referring toFIG. 8, the graph158illustrates an amount of cooling required to remove heat from various thicknesses of body tissue. As illustrated by line160, 37° C. to 10° C. cooling of the skin will cool approximately 1 millimeter of skin. 37° C. cooling of fat will cool approximately 1 millimeter of fat as illustrated by point162of line164. As shown in line164, the amount of cooling required to remove heat from thicker fat increases with the thickness of the fat, e.g. as illustrated by point166, 16° C. of cooling is required to remove the heat from 35 millimeters of fat. 37° C. cooling of bone will cool approximately 1 millimeter of bone as illustrated by point168of line170. As shown in line170, the amount of cooling required to remove heat from thicker bone increases with the thickness of the bone, e.g. as illustrated by point172, 26° C. of cooling is required to remove the heat from 35 millimeters of bone. 37° C. warming of skin will heat approximately 1 millimeter to approximately 35 millimeters of skin as illustrated by line180.

FIG. 9is a perspective view of another embodiment of a surgical platform200having cushions202. As illustrated inFIG. 9, the cooling zone204is positioned at the patient's hip206. The heating zone208is positioned at the patient's shoulders210and side212. Notably, as described herein, the cooling zones and heating zones may be positioned at any locations on the patient's body as desired.

The heat exchanger module18of the underbody warming device16provides the heat required to prevent perioperative hypothermia. Most perioperative warming devices on the market used to prevent perioperative hypothermia put out about 200 watts, and warming can be achieved with just 20% of the body surface area in contact with the warming device. Given an average body surface area of 1.8 m2, 0.4 m2of body surface area delivers 200 W at 0.5 W/cm2of heating.

It should be noted that the embodiments described herein may be utilized for local cooling without warming to facilitate preventing pressure injuries. The embodiments may also be utilized for local warming for comfort with protective cooling. Moreover, the embodiments described herein may be used for local cooling for any purpose, such as comfort, relief from inflammation, burns, fever, perspiration, etc.

The embodiments described herein minimize the risk of pressure injuries originating in the operating, e.g. when bony prominences in contact with the surface of the surgical table are heated. Increased tissue temperatures increase the risk of pressure injuries. Accordingly, the embodiments described herein use thermoelectric coolers20for focal cooling of the bony prominences. Through use of the embodiments described herein, a solid working surface is regained by eliminating the puffy forced-air warming blanket underneath the surgical drape. Also, immediate warmth and comfort is provided to alert but apprehensive patients placed onto the operating table. Moreover, issues and concerns associated with the use of forced air blankets including the disruption of the sterile field are eliminated.

Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, the invention contained herein is not limited to this precise embodiment and that changes may be made to such embodiments without departing from the scope of the invention as defined by the claims. Additionally, it is to be understood that the invention is defined by the claims and it is not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the interpretation of any claim element unless such limitation or element is explicitly stated. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.