Patent Description:
The present invention relates generally to a pressure management device, and more particularly to a pressure management device with an integrated warming apparatus.

It is well known that the back part of the head is at risk for pressure ulcers if the patient is not properly positioned. Therefore, pressure management with respect to surgical headrests often focuses on pressure management for the occiput. There are many existing occiput pressure management devices. Such devices are typically donut-shaped, U-shaped, stepped conformal, and T-shaped; made of materials, including, but not limited to, gel and foam; and sized for pediatric, adult, and bariatric patients. Several existing occipital pressure management devices have a round hole or recess to provide pressure management for the occiput. However, it is believed that the round hole or recess is not best suited to the anatomy of the human head in either the supine or side-laying positions. Accordingly, there are drawbacks to existing surgical headrests with respect to pressure management. <CIT> discloses a heating blanket that is removably attached to a helmet casing using a biased clip which is spring loaded and attached to an upper edge of the helmet casing, wherein wires of said heating blanket might also be a flat strip style wire that is appliqued to the exterior surface of the helmet casing and an interface on the clip such that attaching the clip to the helmet casing would also provide power to the blanket through the interface in the clip, and wherein a soft foam facial cushion comprises central ocular and mouth apertures, said apertures in the cushion being comprised of various curved, convex and concave regions.

With regard to patient warming, several studies have shown significant heat loss from a patient under anesthetic during surgery (<NUM> in <NUM> minutes [<NPL>], and <NUM> in <NUM> minutes [<NPL>]). Furthermore, it has been recognized that uncovered head losses for cooler temperatures can account for a large portion of a body's heat loss (<NUM>% at -<NUM> [<NPL>:]). This is particularly important in neonate and pediatric cases where physiologic thermoregulation of patients and smaller sizes relative to head sizes make it difficult to maintain normothermia [(<NPL>) and (<NPL>)].

When exposed to a cool environment, a newborn infant responds by nonshivering thermogenesis. The increased heat production is at the expense of body fuel and energy stores. A significant quantity of heat is lost from the head because of its large surface area and the high metabolic activity of the neonatal brain. Studies have been conducted to determine whether dry cranial heat loss can be significantly reduced by covering the head with a highly insulated material, and to determine whether plastic lined head coverings decrease evaporative heat loss. A total of <NUM> full term and premature infants were studied. Head coverings insulated with material made of olefin and polyester reduced cranial dry heat loss by <NUM>% and <NUM>%. Plastic-lined head coverings reduced evaporative heat loss by <NUM>%. The insulated and lined head coverings proved to be a simple and safe method of effectively reducing dry and evaporative heat loss [https://doi. org/<NUM>/S0022-<NUM>(<NUM>)<NUM>-<NUM>].

The hypothalamus region of the brain is the physiological control center for human temperature regulation. Warming of the hypothalamus can actuate the Arterio-venous anastomoses (AVA) causing more blood to flow to the extremities and promote future warming of the patient under anesthesia [<NPL>]. Furthermore, studies of human anatomy have shown that the most important areas of the head to warm are the vascular region of the neck, sides, and the back of the head.

Moreover, it has also been observed that the operating room is a crowded environment with minimal storage space. Many existing pressure management devices are bulky and can take up a considerable amount of storage space. For example, foam-based pressure management devices are typically stored in cardboard boxes that take up significant amounts of limited storage space.

In view of the foregoing, there is a need for a pressure management device that provides improvements to pressure management for patients in the supine and side-laying positions; warms a patient's head during surgery; and allows for compact storage.

The present invention provides a pressure management device with an integrated warming apparatus that overcomes drawbacks of prior art surgical headrests.

In accordance with the present invention, there is provided a pressure management warming headrest comprising a spacer layer; a heating layer including a heating member having a heating element; and a pressure management layer comprised of at least one foam layer, wherein said spacer layer, heating layer and pressure management layer are bonded together; and wherein the pressure management warming headrest comprises the further features of claim <NUM>.

In accordance with the present invention, there is provided a pressure management warming headrest system comprising: a pressure management warming headrest according to claim <NUM> and a controller for controlling operation of the pressure management warming headrest. The pressure management warming headrest comprises a spacer layer, a heating layer including a heating member having a heating element, and a pressure management layer comprised of at least one foam layer, wherein said spacer layer, heating layer and pressure management layer are bonded together and wherein the pressure management layer has a central opening comprised of a rectangular region and a semicircular region.

An advantage of the present invention is the provision of a pressure management warming headrest that combines a pressure management device with an integrated warming apparatus.

Another advantage of the present invention is the provision of a pressure management warming headrest that accommodates patients in both supine and side-laying positions.

Another advantage of the present invention is the provision of a pressure management warming headrest that provides convective warming of a patient.

Still another advantage of the present invention is the provision of a pressure management warming headrest that can be stored in a minimal volume storage package.

Still another advantage of the present invention is the provision of a pressure management warming headrest that can be easily adapted to a size accommodating bariatric, adult, pediatric, and neonatal patients.

These and other advantages will become apparent from the following description of illustrated embodiments taken together with the accompanying drawings and the appended claims.

The invention may take physical form in certain parts and arrangement of parts, an embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein:.

Referring now to the drawings wherein the showings are for the purpose of illustrating embodiment(s) of the invention only and not for the purposes of limiting same, <FIG> show a pressure management warming headrest (PMWH) <NUM> according to an embodiment of the present invention. In the illustrated embodiment, PMWH <NUM> is generally comprised of a high density (HD) foam layer <NUM>, a low density (LD) foam layer <NUM>, a heating layer <NUM>, a spacer layer <NUM>, and a head cover <NUM>. It should be noted that head cover <NUM> is omitted from <FIG>, <FIG> and <FIG> for greater clarity. PMWH <NUM> is a component of a PMWH system <NUM> shown in <FIG>.

HD foam layer <NUM> has a central opening <NUM>, a lower surface <NUM>, and an upper surface <NUM>, as best seen in <FIG>. In one embodiment of the present invention, HD foam layer <NUM> takes the form of a high density polyurethane foam, such as <NUM> (<NUM>-inch) thick SENL polyether polyurethane foam from William T. Burnett & Co. having a density of <NUM> +/-<NUM>% kg/m<NUM> (<NUM> +/- <NUM>% lbs/ft<NUM>) and an indentation load deflection (ILD) <NUM> N/<NUM><NUM> to <NUM> N/<NUM><NUM> (of <NUM> lbs/<NUM> in<NUM> to <NUM> lbs/<NUM> in<NUM>). According to the illustrated embodiment, rear corners <NUM> of HD foam layer <NUM> are curved to accommodate head cover <NUM>, described below. For example, rear corners <NUM> may be a curved surface defined by a radius of <NUM>.

Referring now to <FIG>, exemplary dimensions for an illustrated embodiment of HD foam layer <NUM> will be discussed. In the illustrated embodiment, opening <NUM> is comprised of a substantially rectangular region <NUM> and a semi-circular region <NUM>. As shown in <FIG>, rectangular region <NUM> is defined, in part, by a pair of curved surfaces <NUM>. For example, curved surfaces <NUM> may be defined by a radius of <NUM>. Exemplary dimensions for the illustrated embodiment are as follows:.

The dimensions for opening <NUM> are preferably selected to facilitate superior pressure management for patients oriented on PMWH <NUM> in both supine and side-laying positions.

LD foam layer <NUM>, according to the invention, has a central opening <NUM>, a lower surface <NUM>, and an upper surface <NUM>. In one embodiment of the present invention, LD foam layer <NUM> takes the form of a low density polyurethane foam, such as Flexible Foam Products (#<NUM>) <NUM> (<NUM>-inch) thick <NUM>% open cell polyurethane foam having a density <NUM>-<NUM>/m<NUM> ( <NUM>-<NUM> lbs/ft<NUM>) and an indentation load deflection (ILD) of <NUM> N/<NUM> cm2 to <NUM> N/<NUM> cm2 (<NUM> lbs/<NUM> in<NUM> to <NUM> lbs/<NUM> in<NUM>). In the illustrated embodiment, LD foam layer <NUM> has substantially the same shape and dimensions as HD foam layer <NUM>, except thickness T is reduced.

HD foam layer <NUM> and LD foam layer <NUM>, in combination, provide a pressure management layer for PMWH <NUM>. In accordance with contemplated alternative embodiments of the present invention, the pressure management layer may be comprised of one or more foam layers.

Heating layer <NUM> is generally comprised of a flexible heating member <NUM> and a connector interface <NUM>, as best seen in <FIG> and <FIG>. According to an embodiment of the present invention, flexible heating member <NUM> is comprised of a heating element in the form of a conductive material that is applied to a flexible substrate (e.g., polyester (PET), polyimide (PI), polycarbonate (PC), and thermoplastic polyurethanes (TPU)). The flexible substrate provides support for the heating element and serves as a dielectric. In one embodiment of the present invention, the heating element is sandwiched between a pair of the flexible substrates. The heating element may be applied to the flexible substrate by a screen printing process or other well-known fluid deposition processes, such as gravure/flexographic, ink jet, controlled spray, and the like. In the illustrated embodiment, the flexible substrate is a PET substrate having a thickness in the range <NUM> to <NUM> (<NUM> inch to <NUM> inch).

In accordance with one embodiment of the present invention, the heating element takes the form of a positive temperature coefficient (PTC) material (e.g., a PTC heating film or PTC thermistor). A PTC heating element is typically made with a thermoplastic PTC carbon ink. A PTC heating element is a self-regulating heating element because as the PTC heating element warms up, its resistance increases (i.e., conductivity decreases), thereby reducing power. Accordingly, a PTC heating element is capable of regulating its temperature without any outside controls. The PTC heating element is preferably configured with a watt density (watts/area) such that the size of the heating element provides a thermal flux that matches the heat loss of a patient.

In one exemplary embodiment of the present invention, heating member <NUM> is comprised of a heating element applied to a PET substrate (e.g., having a thickness of <NUM> ( <NUM> inch)). The heating element takes the form of a layer of conductive particles. The conductive particles may be applied to the substrate by processes such as screen printing, gravure/flexographic, ink jet, controlled spray, and the like. The conductive particles can take several forms, including, but not limited to, carbon ink (e.g., Engineered Conductive Materials CI-<NUM> Series), carbon nanotube, graphite, and a carbon-based PTC resistor paste (PTC ink), such as DuPont <NUM> PTC Carbon Resister. It should be appreciated that use of a PTC ink provides a safety benefit by allowing PMWH <NUM> to have a resistance magnification effect at <NUM> which is the desired heating temperature for spacer layer <NUM> to achieve a desired <NUM> patient surface contact temperature. Furthermore, carbon is a desirable material since it allows for radiolucency.

In one embodiment of the present invention, heating member <NUM> also includes a silver bus bar of interdigitated fingers to bring current to the PTC carbon resistor ink that serves as the heating element. The silver bus bar is formed on the substrate by screen printing.

After the process of applying the PTC ink is completed, heating member <NUM> is silkscreened for labelling, and die-cut using a steel-ruled die (or alternatively a laser, a water jet, or the like) to form a spiral <NUM> for pressure management, as best seen in <FIG>. Spiral <NUM> has a corresponding gap <NUM> (e.g., approximately <NUM>). The die cutting also forms a circular center disk <NUM> having a slit <NUM> (e.g., <NUM> (<NUM> inch)) for additional pressure management. Slit <NUM> preferably extends along the direction of the electron path, as shown in <FIG>. However, slit 64may be oriented orthogonal to the electron path with perforations in the heating element to control undesirable electron flow. It should be appreciated that die-cutting heating member <NUM> in the manner described above allows the other layers of PMWH <NUM> to move, thereby reducing pressure on the patient's tissues.

In accordance with an alternative embodiment of the present invention, it is contemplated that slit <NUM> may be replaced with a hole, thereby making center disk <NUM> ringshaped.

As illustrated, the spiral configuration preferably has a double start helix so that positive and negative terminal connections can be provided at a peripheral outer exposed end of heating member <NUM> for easier connection with a controller. This configuration also eliminates the need to locate copper connecting wires within an X-ray zone.

To be a low heat transfer device in accordance with ISA Standard IEC80601-<NUM>-<NUM>, it is desirable to have a heating element density (Watts/area) that is less than <NUM> W/m<NUM>. In the illustrated embodiment, the total heating area of heating element is. <NUM><NUM>. Therefore, wattage is <NUM>. 325W for this embodiment of the present invention. The wattage of heating member <NUM> according to an embodiment of the present invention may be in the range of about 5W to 45W.

While heating member <NUM> has been described herein with respect to a PTC heating element, it is contemplated that other types of heating elements, including those that are not self-regulating may be implemented in connection with the present invention. Furthermore, it is contemplated that according to alternative embodiments of the present invention heating member <NUM> may be die-cut into forms other than the illustrated spiral shape.

Connector interface <NUM> of heating layer <NUM> will now be described with particular reference to <FIG> and <FIG>. Connector interface <NUM> is comprised of a conductive layer (e.g., silver) sandwiched between two flexible substrates. The conductive layer is electrically connected with the heating element of heating member <NUM>. The substrates may be formed of the same material as the substrates described above in connection with heating member <NUM> (e.g., PET).

Holes (e.g., <NUM>) are formed in the substrates and conductive layer to receive positive and negative terminals <NUM>, <NUM>. In an illustrated embodiment of the present invention, positive and negative terminals <NUM>, <NUM> take the form of studs or snaps that are crimped onto the holes. It is contemplated that terminals <NUM>, <NUM> may take other forms, including, alligator clips or CrimpFlex™ contacts that are crimped through the PET substrate into the conductive inks forming the conductive layer.

Connector interface also includes an alignment hole <NUM> (e.g., <NUM>) and a thermal pad <NUM> which serves as a proxy for the temperature of the heating element of heating member <NUM>. In one embodiment of the present invention, thermal pad <NUM> takes the form of screen printed carbon and silver sandwiched by dielectric substrates. To serve as the proxy for the temperature of the heating element, the area of thermal pad <NUM> is selected to have substantially the same thermal wattage density as the heating area of the heating element. Therefore, a costly temperature sensor does not need to be an integral component of PMWH <NUM>, thereby making PMWH <NUM> less costly to implement as a disposable article. In an illustrated embodiment, thermal pad <NUM> is a square having side dimensions of <NUM>-<NUM>.

Spacer layer <NUM>, functioning as a comfort layer, includes a lower surface <NUM> and an upper surface <NUM>. According to an embodiment of the present invention, spacer layer <NUM> is formed of a spacer fabric, such as Muller Textil GmbH 3mesh® three-dimensional spacer knit fabric T6010-<NUM> or 3mesh® three-dimensional spacer knit fabric T5975-<NUM>. The spacer fabric provides pressure immersion and comfort to the touch. In one embodiment of the invention, spacer layer <NUM> has a thickness of approximately <NUM>, but can be increased to allow for better pressure management. While an increased layer thickness increases thermal resistance, this can be accommodated by increasing the power to heating member <NUM> to allow for the same resultant patient contact temperature. 3mesh® spacer fabric has a substantially consistent temperature with a drop of (<NUM>. 25C) for both the compressed and uncompressed state. In the illustrated embodiment, spacer layer <NUM> has substantially the same shape and dimensions as HD foam layer <NUM>, except thickness T is reduced and a central opening is omitted.

It should be understood that HD foam layer <NUM>, LD foam layer <NUM>, heating layer <NUM> and spacer layer <NUM> are bonded to each other by use an adhesive, such as SIMALFA® water-based adhesive, <NUM>™ Super <NUM>™ multipurpose spray adhesive, or Claire® Mist Adhesive. Accordingly, thin layers of adhesive (not shown) are located between these layers. It should be appreciated that the adhesive may be applied to all or only portions of the layer surfaces.

Head cover <NUM> will now be described with reference to <FIG> and <FIG>. In the illustrated embodiment, head cover <NUM> is made of a lightweight, non-woven material such as an air-laid non-woven material. Air-laid non-woven materials are preferable since they are more thermally resistive than carded non-woven materials. A <NUM> mil air-laid polyolefin fabric provides a thermal resistance of approximately <NUM> R ([M<NUM>K]/W) which optimizes the insulation value based on the maximum desired thickness of the non-woven material. Head cover <NUM> is stretched over a patient's head to capture and trap convective warming heat. Other suitable materials for head cover <NUM> include olefin and polypropylene.

In one embodiment of the present invention, the flat pattern unsewn shape of head cover <NUM> is circular with a diameter of <NUM> (<NUM> inches). Head cover <NUM> includes an elastic gather <NUM> stitched into the round edge to keep it gathered around a patient's face. Elastic gather <NUM> is lightly stretched during the sewing process for a finished size of <NUM> to <NUM> (<NUM> to <NUM> inches) diameter when relaxed. The inner surface of head cover <NUM> is attached to lower surface <NUM> of HD foam layer <NUM> using an adhesive <NUM>, as illustrated in <FIG>. The adhesive may be the same as the adhesive used for bonding together HD foam layer <NUM>, LD foam layer <NUM>, heating layer <NUM>, and spacer layer <NUM>.

It is contemplated in accordance with an alternative embodiment of the present invention that elastic gather <NUM> may be replaced or supplemented with a repositionable, biocompatible adhesive bonded onto a plastic film. The adhesive allows the head cover to stick to a region surrounding the patient's face.

Head cover <NUM> includes a hole <NUM> and a slit <NUM>. Hole <NUM> aligns with the central opening <NUM> of HD foam layer <NUM>. This allows the head cover <NUM> to be stuffed into central opening <NUM> for packaging and shipping. Since PMWH <NUM> is typically placed on a foam table pad for usage there is negligible heat loss through hole <NUM>. Slit <NUM> provides an opening that allows connector interface <NUM> to pass through head cover <NUM> for connection with controller cable interface <NUM>.

PMWH <NUM> may be compressed for compact storage by vacuum packing. In this regard, air may be removed from the foam layers to reduce volume.

Controller <NUM> is a conventional processing device programmed to control operation of PMWH <NUM>. In one embodiment of the present invention, controller <NUM> may take the form of a control unit running an open loop at 36V designed to a self-regulating <NUM> max, at an ambient temperature of <NUM>. Accordingly, the voltage delivered to the heating element is 36V with a desired temperature up to <NUM>. An open loop controller may drive a PTC ink heating element with a corresponding pulse width modulation (PWM) duty cycle to obtain a desired operating temperature, as selected at controller <NUM> (e.g., <NUM>, <NUM>, <NUM> <NUM>, or <NUM>). For example, a <NUM>% PWM duty cycle may achieve a temperature of <NUM>, while a <NUM>% PWM duty cycle may achieve a temperature of <NUM>. It is also contemplated that temperature sensor <NUM> of controller cable interface <NUM> could be used to drive the heating element in a closed loop fashion.

Controller <NUM> includes a connecting cable having a controller cable interface <NUM>, as shown in <FIG>. Controller cable interface <NUM> includes an insulated housing <NUM> having a recess dimensioned to receive connector interface <NUM> of heating layer <NUM>. Controller cable interface <NUM> also includes positive and negative contacts <NUM>, <NUM>, alignment pin <NUM>, and a temperature sensor <NUM>. Positive and negative contacts <NUM>, <NUM> respectively engage with positive and negative terminals <NUM>, <NUM> of connector interface <NUM>. Alignment pin <NUM> is dimensioned to be received in alignment hole <NUM> to align and secure connector interface <NUM> to controller cable interface <NUM>. Temperature sensor <NUM> is aligned with thermal pad <NUM> to sense the temperature of thermal pad <NUM> in order to determine the temperature of heating member <NUM>. For example, temperature sensor <NUM> may take the form of a thermocouple, a thermistor, or a resistance temperature detector (RTD). Temperature sensor <NUM> functions as a safety backup for the self-regulating heating element of heating member <NUM>. Accordingly, temperature sensor <NUM> ensures that a maximum allowable temperature is not exceeded. While controller <NUM> is shown herein as an external device to PMWH <NUM>, it is also contemplated that controller <NUM> may be integrated into PMWH <NUM> to form a non-disposable PMWH <NUM>.

Claim 1:
A pressure management warming headrest (<NUM>) comprising:
a spacer layer (<NUM>);
a heating layer (<NUM>) including a heating member (<NUM>) having a heating element; and
a pressure management layer comprised of at least one foam layer (<NUM>),
wherein said spacer layer (<NUM>), heating layer (<NUM>) and pressure management layer are bonded together, and
wherein the pressure management layer has a central opening (<NUM>) comprised of a rectangular region (<NUM>) and a semicircular region (<NUM>).