HEATING BLANKETS AND PADS
An electric heating blanket includes a flexible sheet-like heating element, a first unheated flap extending from a first edge of the heating element, and a second unheated flap extending from a second edge of the heating element. A flexible water-resistant shell may cover the heating element.
The present application claims priority to co-pending provisional applications Ser. No. 60/825,573, entitled HEATING BLANKET SYSTEM filed on Sep. 13, 2006; Ser. No. 60/722,106, entitled ELECTRIC WARMING BLANKET INCLUDING TEMPERATURE ZONES AUTOMATICALLY OPTIMIZED, filed Sep. 29, 2005; and Ser. No. 60/722,246, entitled HEATING BLANKET, filed Sep. 29, 2005; all of which are incorporated by reference in their entireties herein.
RELATED APPLICATIONSThe present application is related to the following commonly assigned utility patent applications, all of which are filed concurrently herewith and all of which are hereby incorporated by reference in their entireties: A) ELECTRIC WARMING BLANKET HAVING OPTIMIZED TEMPERATURE ZONES, Practitioner docket number 49278.2.5.2; B) TEMPERATURE SENSOR ASSEMBLIES FOR ELECTRIC WARMING BLANKETS, Practitioner Docket Number 49278.2.9.2; C) FLEXIBLE HEATING ELEMENT CONSTRUCTION, Practitioner Docket Number 49278.2.15; D) BUS BAR ATTACHMENTS FOR FLEXIBLE HEATING ELEMENTS, Practitioner Docket Number 49278.2.16; and E) BUS BAR INTERFACES FOR FLEXIBLE HEATING ELEMENTS, Practitioner Docket Number 49278.2.17.
TECHNICAL FIELDThe present invention is related to heating or warming blankets or pads and more particularly to those including electrical heating elements.
BACKGROUNDIt is well established that surgical patients under anesthesia become poikilothermic. This means that the patients lose their ability to control their body temperature and will take on or lose heat depending on the temperature of the environment. Since modern operating rooms are all air conditioned to a relatively low temperature for surgeon comfort, the majority of patients undergoing general anesthesia will lose heat and become clinically hypothermic if not warmed.
Over the past 15 years, forced-air warming (FAW) has become the “standard of care” for preventing and treating the hypothermia caused by anesthesia and surgery. FAW consists of a large heater/blower attached by a hose to an inflatable air blanket. The warm air is distributed over the patient within the chambers of the blanket and then is exhausted onto the patient through holes in the bottom surface of the blanket.
Although FAW is clinically effective, it suffers from several problems including: a relatively high price; air blowing in the operating room, which can be noisy and can potentially contaminate the surgical field; and bulkiness, which, at times, may obscure the view of the surgeon. Moreover, the low specific heat of air and the rapid loss of heat from air require that the temperature of the air, as it leaves the hose, be dangerously high—in some products as high as 45° C. This poses significant dangers for the patient. Second and third degree burns have occurred both because of contact between the hose and the patient's skin, and by blowing hot air directly from the hose onto the skin without connecting a blanket to the hose. This condition is common enough to have its own name—“hosing.” The manufacturers of forced air warming equipment actively warn their users against hosing and the risks it poses to the patient.
To overcome the aforementioned problems with FAW, several companies have developed electric warming blankets. However, these electric blankets have a number of inadequacies, for example, the risk of heat and pressure injuries that may be suffered by a patient improperly coming into contact with the electrical heating elements of these blankets. It is well established that heat and pressure applied to the skin can rapidly cause thermal injury to that skin. Such contact may arise if a patient inadvertently lies on an edge of a heated blanket, if a clinician improperly positions an anesthetized patient atop a portion of the heated blanket, or if a clinician tucks an edge of the blanket about the patient. Thus, there is a need for a heating blanket that effectively forms a cocoon about a patient, in order to provide maximum efficacy in heating, without posing the risk of burning the patient.
BRIEF DESCRIPTION OF THE DRAWINGSThe following drawings are illustrative of particular embodiments of the present invention and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements.
FIGS. 1B-C are end views of two embodiments of the subassembly shown in
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 exemplary embodiments of the present invention. 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 of the invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized. The term ‘blanket’, used to describe embodiments of the present invention, may be considered to encompass heating blankets and pads.
According to some preferred embodiments, two or more rows of stitches are applied to each bus bar 15 for added safety and stability of the bus bar/heating element interface. Preferably, the two rows of stitches are oriented in a “zigzag” pattern so that each row of stitches captures an edge of bus bar 15. A zigzag pattern of relatively closely positioned stitches stabilizes flexible heating element 10 and holds it in close opposition to bus bar 15 so that the fabric cannot physically pull away from the bus bar during flexing. According to some additional embodiments, a ribbon of highly conductive material is interposed between bus bar 15 and heating element 10.
According to an exemplary embodiment, a conductive fabric comprising heating element 10 comprises a non-woven polyester having a basis weight of approximately 130 g/m2 and being 100% coated with polypyrrole (available from Eeonyx Inc., Pinole, Calif.); the coated fabric has an average resistance, for example, determined with a four point probe measurement, of approximately 15-20 ohms per square inch at about 48 volts, which is suitable to produce the preferred watt density of 0.2 to 0.4 watts/sq. in. for surface areas of heating element 10 having a width, between bus bars 15, in the neighborhood of about 20 inches. Such a width is suitable for a lower body heating blanket, some embodiments of which will be described below. A resistance of such a conductive fabric may be tailored for different widths between bus bars (wider requiring a lower resistance and narrower requiring a higher resistance) by increasing or decreasing a surface area of the fabric that can receive the conductive coating, for example by increasing or decreasing the basis weight of the fabric. Resistance over the surface area of the conductive fabrics is generally uniform in many embodiments of the present invention. However, the resistance over different portions of the surface area of conductive fabrics such as these may vary, for example, due to variation in a thickness of a conductive coating, variation within the conductive coating itself, variation in effective surface area of the substrate which is available to receive the conductive coating, or variation in the density of the substrate itself. Local surface resistance across a heating element, for example element 10, is directly related to heat generation according to the following relationship:
Q(Joules)=I2(Amps)×R(Ohms)
Variability in resistance thus translates into variability in heat generation, which is measured as a temperature. According to preferred embodiments of the present invention, which are employed to warm patients undergoing surgery, precise temperature control is desirable. Means for determining heating element temperatures, which average out temperature variability caused by resistance variability across a surface of the heating element, are described below in conjunction with FIGS. 2A-B.
A flexibility of blanket subassembly 100, provided primarily by flexible heating element 10, and optionally enhanced by the incorporation of flexible bus bars, allows blanket subassembly 100 to conform to the contours of a body, for example, all or a portion of a patient undergoing surgery, rather than simply bridging across high spots of the body; such conformance may optimize a conductive heat transfer from element 10 to a surface of the body. However, as illustrated in
The uniform watt-density output across the surface areas of preferred embodiments of heating element 10 translates into generally uniform heating of the surface areas, but not necessarily a uniform temperature. At locations of heating element 10 which are in conductive contact with a body acting as a heat sink, for example, body 16, the heat is efficiently drawn away from heating element 10 and into the body, for example by blood flow, while at those locations where element 10 does not come into conductive contact with the body, for example lateral portions 11, 12 as illustrated in
According to embodiments of the present invention, zones of heating element 10 may be differentiated according to whether or not portions of element 10 are in conductive contact with a body, for example, a patient undergoing surgery. In the case of conductive heating, gentle external pressure may be applied to a heating blanket including heating element 10, which pressure forces heating element 10 into better conductive contact with the patient to improve heat transfer. However, if excessive pressure is applied the blood flow to that skin may be reduced at the same time that the heat transfer is improved and this combination of heat and pressure to the skin can be dangerous. It is well known that patients with poor perfusion should not have prolonged contact with conductive heat in excess of approximately 42° C. 42° C. has been shown in several studies to be the highest skin temperature, which cannot cause thermal damage to normally perfused skin, even with prolonged exposure. (Stoll & Greene, Relationship between pain and tissue damage due to thermal radiation. J. Applied Physiology 14(3):373-382. 1959. and Moritz and Henriques, Studies of thermal injury: The relative importance of time and surface temperature in the causation of cutaneous burns. Am. J. Pathology 23:695-720, 1947) Thus, according to certain embodiments of the present invention, the portion of heating element 10 that is in conductive contact with the patient is controlled to approximately 43° C. in order to achieve a temperature of about 41-42° C. on a surface a heating blanket cover that surrounds element 10, for example, a cover or shell 20, 40 which will be described below in conjunction with
Referring now to the end view of
Preferably, coupling 145 includes two or more rows of stitches for added security and stability. However, due to the flexible nature of blanket subassembly 100, the thread of stitched couplings 145, for either embodiment of
Referring back to
Returning now to
According to some embodiments of the present invention, for example as illustrated in
According to some embodiments of the present invention, shell 20 includes top and bottom sheets extending over either side of assembly 250; the two sheets of shell 20 are coupled together along a seal zone 22 (shown with cross-hatching in the cut-away portion of
Returning now to
FIGS. 3C-D further illustrate a pair of securing strips 217, each extending laterally from and alongside respective lateral portions 11, 12 of heating element 10 and each coupled to side 13 of heating element 10 by the respective row of stitching 345. Another pair of securing strips 271 is shown in
With reference to
With further reference to
In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims. Although embodiments of the invention are described in the context of a hospital operating room, it is contemplated that some embodiments of the invention may be used in other environments. Those embodiments of the present invention, which are not intended for use in an operating environment and need not meet stringent FDA requirements for repeated used in an operating environment, need not including particular features described herein, for example, related to precise temperature control. Thus, some of the features of preferred embodiments described herein are not necessarily included in preferred embodiments of the invention which are intended for alternative uses.
Claims
1. An electric heating blanket, comprising:
- a flexible sheet-like heating element including a first side, a second side, a first end, a second end, a first edge extending between the first and second ends, and a second edge, opposite the first edge, and extending between the first and second ends;
- a flexible shell covering the heating element and comprising a water resistant material layer;
- a first unheated flap extending away from the first edge of the heating element; and
- a second unheated flap extending away from the second edge of the heating element.
2. The heating blanket of claim 1, wherein the heating element has a substantially uniform watt density output across a surface area thereof when electrically powered.
3. The heating blanket of claim 1, further comprising a flexible layer of insulating material extending between the at least one of the first and second sides of the heating element and the flexible shell.
4. The heating blanket of claim 3, wherein the layer of insulating material is bonded to a surface area of at least one of the first and second sides.
5. The heating blanket of claim 3, wherein the layer of insulating material comprises a foam.
6. The heating blanket of claim 3, wherein the layer of insulating material comprises a high loft non-woven fibrous material.
7. The heating blanket of claim 3, wherein the shell is un-adhered to the layer of insulating material.
8. The heating blanket of claim 1, further comprising:
- a first conductive bus bar coupled to the heating element and extending alongside the first edge of the heating element from a first point in proximity to the first end of the heating element to a second point in proximity to the second end of the heating element;
- a second conductive bus bar coupled to the heating element and extending alongside the second edge of the heating element from another first point in proximity to the first end of the heating element to another second point in proximity to the second end of the heating element;
- a first lead coupled to the first bus bar between the first and second points; and
- a second lead coupled to the second bus bar between the other first and second points;
- wherein the first and second leads are adapted for coupling to a power source for powering the bus bars.
9. The heating blanket of claim 1, further comprising:
- a first conductive bus bar coupled to the heating element and extending alongside the first edge of the heating element between the first and second ends thereof; and
- a second conductive bus bar coupled to the heating element and extending alongside the second edge of the heating element between the first and second ends thereof;
- wherein the first edge of the heating element is stitched to the first bus bar with a conductive thread;
- the second edge of the heating element is stitched to the second bus bar with another conductive thread; and
- the first and second bus bars are adapted for coupling to a power source for powering the heating element.
10. The heating blanket of claim 1, further comprising:
- a first conductive bus bar coupled to the heating element and extending alongside the first edge of the heating element between the first and second ends thereof; and
- a second conductive bus bar coupled to the heating element and extending alongside the second edge of the heating element between the first and second ends thereof;
- wherein the first and second conductive bus bars extend beyond the first and second ends of the heating element; and
- the first and second bus bars are adapted for coupling to a power source for powering the heating element.
11. The heating blanket of claim 8, further comprising a temperature sensor coupled to the heating element at a location where the heating element will be in conductive contact with a body when the blanket is draped over the body.
12. The heating blanket of claim 1, wherein a length from the first end to the second end of the heating element is greater than approximately seven times a width of the heating element.
13. The heating blanket of claim 1, wherein the flexible sheet-like heating element comprises a conductive fabric.
14. The heating blanket of claim 1, wherein the flexible sheet-like heating element comprises carbon.
15. The heating blanket of claim 1, wherein the flexible sheet-like heating element comprises a nonconductive layer coated with a conductive material.
16. The heating blanket of claim 15, wherein the nonconductive layer comprises polyester and the conductive material comprises polypyrrole.
17. The heating blanket of claim 1, wherein the flexible sheet-like heating element comprises a fabric incorporating closely spaced conductive elements.
18. The heating blanket of claim 1, wherein the shell is un-adhered to the first and second sides of the heating element.
19. The heating blanket of claim 1, wherein the shell further comprises an anti-microbial material.
20. The heating blanket of claim 1, wherein the flexible shell further comprises a layer of nylon and the water-resistant material layer comprises a polyurethane coating extending over at least one side of the nylon.
21. The heating blanket of claim 1, wherein:
- the shell includes a first sheet extending over the first side of the heating element and a second sheet extending over the second side of the heating element; and
- the first sheet is heat sealed to the second sheet around a perimeter of the heating element.
22. The heating blanket of claim 21, wherein the water-resistant material layer of the shell comprises a coating of polyurethane extending over facing sides of the first and second sheets.
23. The heating blanket of claim 21, further comprising:
- a first layer of electrical insulation extending over the first side of the heating element and bonded thereto;
- a second layer of electrical insulation extending over the second side of the heating element and bonded thereto; and
- a layer of thermal insulation extending over the first side of the heating element, being adjacent to the first layer of electrical insulation and un-adhered thereto;
- wherein the first sheet of the shell extends adjacent to the layer of thermal insulation, being un-adhered thereto; and
- the second sheet of the shell extends adjacent to the second layer of electrical insulation, being un-adhered thereto.
24. The heating blanket of claim 21, further comprising:
- a first securing strip coupled to the first edge of the heating element and extending laterally away from the heating element; and
- a second securing strip coupled to the second edge of the heating element and extending laterally away from the heating element;
- wherein the first and second securing strips are engaged with the first and second sheets.
25. The heating blanket of claim 1, further comprising:
- a first conductive bus bar coupled to the heating element and extending alongside the first edge of the heating element between the first and second ends thereof; and
- a second conductive bus bar coupled to the heating element and extending alongside the second edge of the heating element between the first and second ends thereof;
- wherein the first edge of the heating element extends laterally from the first bus bar and the second edge extends laterally from the second bus bar, each of the first and second edges including at least one opening extending therethrough;
- the shell includes a first sheet extending over the first side of the heating element and a second sheet extending over the second side of the heating element;
- the first sheet is heat sealed to the second sheet around a perimeter of the heating element and through the openings of the first and second edges; and
- the first and second bus bars are adapted for coupling to a power source for powering the heating element.
26. The heating blanket of claim 1, wherein the first and second flaps are extensions of the flexible shell.
27. The heating blanket of claim 26, further comprising:
- a first weighting member coupled to the first flap; and
- a second weighting member coupled to the second flap;
- wherein the shell includes a first sheet extending over the first side of the heating element and a second sheet extending over the second side of the heating element; and
- the first sheet is heat sealed to the second sheet around a perimeter of the heating element and around a perimeter of each of the first and second weighting members.
28. The heating blanket of claim 1, wherein the first and second flaps are weighted.
29. The heating blanket of claim 28, wherein the first and second flaps are weighted with relatively stiff members.
30. The heating blanket of claim 28, further comprising:
- a third weighted flap extending from the first edge of the heating element and spaced apart along the first edge from the first weighted flap; and
- a fourth weighted flap extending from the second edge of the heating element and spaced apart along the second edge from the second weighted flap;
- wherein the first, second, third and fourth weighted flaps are weighted with a relatively stiff member.
31. The heating blanket of claim 1, further comprising:
- a third unheated flap extending from the first edge of the heating element and spaced apart along the first edge from the first flap; and
- a fourth unheated flap extending from the second edge of the heating element and spaced apart along the second edge from the second flap.
32. The heating blanket of claim 31, further comprising:
- a first strap disposed between the first and third flaps; and
- a second strap disposed between the second and fourth flaps;
- wherein the first and second straps mate to secure the blanket about a body, when the blanket is draped over the body.
33. The heating blanket of claim 32, wherein the first and second straps mate via one of: magnetic fasteners coupled thereto, mating hook-and-loop fasteners coupled thereto, and mating snap fasteners coupled thereto.
34. The heating blanket of claim 1, further comprising an unheated foot drape extending from one of the first and second ends of the heating element.
35. The heating blanket of claim 34, wherein the foot drape includes at least one pair of reversible fasteners, and each fastener of the at least one pair being disposed to secure the foot drape in a folded configuration for forming a pocket about feet of a patient.
36. An electric heating blanket, comprising:
- a flexible sheet-like heating element including a first side, a second side, a first end, a second end, a first edge extending between the first and second ends, and a second edge, opposite the first edge, and extending between the first and second ends;
- a first unheated flap extending from the first edge of the heating element;
- a second unheated flap extending from the second edge of the heating element; and
- a third unheated flap extending from one of the first and second ends of the heating element.
37. The blanket of claim 36, wherein the third flap has sufficient length to be folded back toward the heating element in order to create a pocket for enclosing feet of a patient when the blanket is draped over the patient.
38. The blanket of claim 37, wherein the third flap includes at least one pair of reversible fasteners coupled thereto in order to secure the flap in the folded pocket configuration.
39. An upper body electric heating blanket, comprising:
- a flexible sheet-like heating element including a first side, a second side, a first end, a second end, a first edge extending between the first and second ends, and a second edge, opposite the first edge, and extending between the first and second ends;
- a first unheated flap extending from the first edge of the heating element;
- a second unheated flap extending from the second edge of the heating element;
- a third unheated flap extending from the first edge of the heating element and spaced apart, along the first edge, from the first flap, the spacing leaving a gap between the third and first flaps in which the first edge is free from flaps so as to accommodate a patient's head within the gap; and
- a fourth unheated flap extending from the second edge of the heating element and spaced apart, along the second edge, from the second flap.
40. The blanket of claim 39, further comprising:
- a first strap disposed between the first and third flaps; and
- a second strap disposed between the second and fourth flaps;
- wherein the first and second straps mate to secure the blanket about a body, when the blanket is draped over the body.
41. The blanket of claim 39, further comprising a central narrowed portion between the first and third flaps and the second and fourth flaps; wherein, when the blanket is draped across an upper body portion of a patient, the first and second flaps extend on either side of a first arm of the patient, the third and fourth flaps extend on either side of a second arm of the patient, and the central portion extends over a chest of a patient.
42. The blanket of claim 41, further comprising a temperature sensor coupled to the heating element at a location coinciding with the central narrowed portion of the blanket.
Type: Application
Filed: Sep 29, 2006
Publication Date: Apr 12, 2007
Inventors: Scott Augustine (Bloomington, MN), Randall Arnold (Minnetonka, MN), Rudolf Deibel (Eden Prairie, MN), Scott Entenman (St. Paul, MN), Keith Leland (Medina, MN), Thomas Neils (Minneapolis, MN)
Application Number: 11/537,179
International Classification: H05B 3/00 (20060101); H05B 1/00 (20060101); H05B 11/00 (20060101);