PATENT DOCUMENT

Abstract:
A covering to treat tissue by raising the temperature of the tissue toward a normothermic level includes a flexible material with upper and lower surfaces and an opening to face a tissue treatment area, an attachment portion near the lower surface, and a heater layer supported by the upper surface, over the opening, to maintain tissue at a temperature in a range from a pretreatment temperature to about 38° C.

Full Description:
CROSS REFERENCES TO RELATED CO-PENDING APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 09/491,722, filed Jan. 27, 2000 now U.S. Pat. No. 6,213,966 which is a continuation of U.S. patent application Ser. No. 09/271,822, filed Mar. 18, 1999, now U.S. Pat. No. 6,113,561, which is a divisional of U.S. patent application Ser. No. 08/786,713, filed Jan. 21, 1997, now U.S. Pat. No. 5,964,723, which is a continuation-in-part U.S. patent application Ser. No. 08/356,325, filed Feb. 21, 1995, now abandoned, which is a 35 U.S.C. 371 priority application of PCT International Application Ser. No. PCT/US93/05876, filed Jun. 18, 1993, which is a continuation-in-part of, and claims priority from, U.S. patent application Ser. No. 07/900,656, filed Jun. 19, 1992, now abandoned. 
     This application is related to U.S. patent application Ser. No. 08/785,794, filed Jan. 21, 1997, now U.S. Pat. No. 5,986,163, and U.S. patent application Ser. No. 08/786,714, file Jan. 21, 1997, now U.S. Pat. No. 5,954,680. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a wound covering for wound treatment and, in particular, wound covers having a substantial portion of the wound cover in non-contact with the wound and capable of delivering heat to the wound. The wound covering preferably controls the temperature, humidity and other aspects of the environment at the wound site. 
     BACKGROUND OF THE INVENTION 
     Wounds in general, as used in this context, are breaks in the integrity of the skin of a patient. Wounds may occur by several different mechanisms. One such mechanism is through mechanical traumatic means such as cuts, tears, and abrasions. There are many instruments of causality for mechanical wounds, including a kitchen bread knife, broken glass gravel on the street, or a surgeon&#39;s scalpel. A different mechanism cause for mechanical wounds is the variable combination of heat and pressure, when the heat alone is insufficient to cause an outright burn. Such wounds that result are collectively referred to as pressure sores, decubitus ulcers, or bed sores, and reflect a mechanical injury that is more chronic in nature. 
     Another type of mechanism causing a wound is vascular in origin, either arterial or venous. The blood flow through the affected region is altered sufficiently to cause secondary weakening of the tissues which eventually disrupt, forming a wound. In the case of arterial causes, the primary difficulty is getting oxygenated blood to the affected area. For venous causes, the primary difficulty is fluid congestion to the affected area which backs up, decreasing the flow of oxygenated blood. Because these wounds represent the skin manifestation of other underlying chronic disease processes, for example, atherosclerotic vascular disease, congestive heart failure, and diabetes, these vascular injuries also are chronic in nature, forming wounds with ulcerated bases. 
     Traditional wound coverings, such as bandages, are used to mechanically cover and assist in closing wounds. Such bandages typically cover the wound in direct contact with the wound. This may be acceptable for acute, non-infected traumatic wounds, but it must be kept in mind that direct bandage contact with a wound can interfere with the healing process. This interference is particularly prevalent for chronic ulcerated wounds because of the repeated mechanical impact and interaction of the bandage with the fragile, pressure sensitive tissues within the wound. 
     The benefits of application of heat to a wound are known, and documented benefits include: increased cutaneous and subcutaneous blood flow; increased oxygen partial pressure at the wound site; and increased immune system functions, both humoral and cell mediated, including increased migration of white blood cells and fibroblasts to the site. 
     However, heat therapy for the treatment of wounds, either infected or clean, has been difficult to achieve in practice. For instance, heating lamps have been used, but these resulted in drying of wounds, and in some cases, even burning tissue from the high heat. Due to these and other difficulties, and since most acute wounds usually heal over time, physicians no longer consider the application of heat to the wound as part of the treatment process. The thinking among medical personnel is that any interference in a natural process should be minimized until it is probable that the natural process is going to fail. Additionally, the availability of antibiotics for use in association with infected wounds has taken precedence over other therapies for the treatment of chronic wounds and topical infections. 
     In French patent number 1,527,887 issued Apr. 29, 1968 to Veilhan there is disclosed a covering with a rigid oval dome, its edge resting directly on the patient&#39;s skin. One aspect of the Veilhan wound protector is a single oval heating element resting on the outer surface of the rigid dome, positioned at the periphery of the rigid dome. Veilhan does not discuss the heating aspect other than to state that it is a component. 
     The benefit of controlling other environmental parameters around the wound site are not as well known. Control the humidity at the wound site and the benefits of isolating the wound have not been extensively studied and documented. 
     While the benefit of applying heat to wounds is generally known, the manner of how that heat should be used or applied is not known. Historically, heat was applied at higher temperatures with the goal of making the wound hyperthermic. These higher temperatures often resulted in increasing tissue damage rather than their intended purpose of wound therapy and healing. There is a need for appropriate wound care management incorporating a heating regimen that is conducive to wound healing, yet safe and cost effective. 
     SUMMARY OF THE INVENTION 
     The present invention disclosed herein approaches the treatment of wounds with heat based on an understanding of physiology. The normal core temperature of the human body, defined herein for purposes of this disclosure, is 37° C.±1° C. (36°-38° C.), which represents the normal range of core temperatures for the human population. For purposes of discussion and this disclosure, normal core temperature is the same as normothermia. Depending on the environmental ambient temperature, insulative clothing and location on the body, skin temperature typically ranges between about 32° C. and about 37° C. From a physiologic point of view, a 32° C. skin temperature of the healthy distal leg is moderate hypothermia. The skin of the distal leg of a patient with vascular insufficiency may be as low as 25° C. under normal conditions, which is severe hypothermia. 
     A fundamental physiologic premise is that all cellular physiologic functions, biochemical and enzymatic reactions in the human body are optimal at normal body core temperature. The importance of this premise is seen in how tightly core temperature is regulated. Normal thermoregulatory responses occur when the core temperature changes as little as ±0.1° C. However, the skin, as noted above, is usually hypothermic to varying degrees. For example, the skin of the torso is usually only slightly hypothermic, whereas the skin of the lower legs is always hypothermic. Consequently, wounds and ulcers of the skin, regardless of location, are usually hypothermic. This skin hypothermia slows cellular functions and biochemical reactions, inhibiting wound healing. 
     The effects of hypothermia on healing are well known. A number of regulatory systems with a human are affected, such as the immune system and coagulation, with both platelet function as well as the clotting cascade affected. Patients with hypothermic wounds experience more infections which are more difficult to treat, have increased bleeding times and have been shown to require more transfusions of blood. All of these complications increase morbidity and the cost of patient care and, to a lesser extent, increase the likelihood of mortality. 
     One purpose of the present invention is to raise the wound tissue and/or periwound tissue temperatures toward normothermia to promote a more optimal healing environment. The present invention is not a “heating therapy”, per se, where it is the intent of “heating therapy” to heat the tissue above normothermia to hyperthermia levels. Rather, the present invention is intended to bring the wound and periwound tissues toward normothermia without exceeding normothermia. 
     The medical community has not historically considered normothermic heating to be therapeutic. Many physicians feel that hypothermia is protective and, therefore, desirable. Studies with the present invention would indicate that this widely held belief that hypothermia is at least benign or possibly beneficial incorrect with regard to wound healing. 
     The present invention is a wound covering for application to a selected treatment area of a patient&#39;s body that includes, at least as a portion of the selected treatment area, a target tissue of a selected wound area. The selected treatment area may also include a portion of the area immediately proximate to the wound area referred to as the periwound area. The wound covering comprises a heater suitable for providing heat to at least a portion of the selected treatment area, an attachment for attaching the heater in a non-contact position proximate the selected treatment area, a heater controller, connected to the heater and including a power source for the heater, for controlling the heater, and an input control to the heater controller providing guidance to the heater controller so as to heat the wound and/or periwound tissue to a temperature in a range from a pretreatment temperature to about 38° C. Pretreatment temperature is that temperature the wound tissue is at when therapy begins and is usually somewhat above ambient temperature and also is variably dependent on where the wound is located on a patient&#39;s body skin surface. The ambient temperature is that temperature of the environment immediately around the selected treatment area not a part of the patient&#39;s body, i.e., the bed, the air in the room, the patient&#39;s clothing. 
     The heater is selectable from among several types of heat sources such as warmed gases directed over the selected treatment area and electrical heater arrays placed proximate the selected treatment area. Electrical heater arrays are adaptable for construction into a layer of variable proportion and geometry or as a point source. The present invention anticipates the ability to provide several different sizes and geometric configurations for the heater. The present invention is flexible in being able to provide uniform heating over the entire selected treatment area or provide a non-uniform heating distribution over selected portions of the selected treatment area. Alternate heat source embodiments could include warm water pads, exothermic chemical heating pads, phase-change salt pads, or other heat source materials. 
     The present invention anticipates that the controller is able to control both the temperature and the duration of the application of heat. This control may extend from manual to fully automatic. Manual control anticipates the controller maintaining the heater temperature at an operator-selected temperature for as long as the operator leaves the heater on. More automatic modes provide the operator an ability to enter duty cycles, to set operating temperatures, as well as to define therapy cycles and therapeutic sequences. As used herein, a duty cycle is a single on cycle when heating of the heater is occurring, measured from the beginning of the on cycle to the end of that on cycle. A heater cycle is a single complete on/off cycle measured from the beginning of a duty cycle to the beginning of the next duty cycle. Consequently, a duty cycle may also be represented in a percentage of, or as a ratio of the time on over the time off. A plurality of heater cycles are used to maintain heater temperature around a selectable temperature set point during a therapy cycle which is defined as an “on” period, composed of a plurality of heater cycles, and an “off” period equivalent to remaining off for an extended period of time. A therapeutic sequence, as used herein, is a longer period of time usually involving a plurality of therapy cycles spread out over an extended period of time, the most obvious being a day in length. The present invention anticipates the use of any period of time as a therapeutic sequence and involving one, or more than one therapy cycles. 
     The present invention also anticipates programmability for a number of modalities including peak heater temperature for a duty cycle and/or therapy cycle, average heater temperature for a duty cycle and/or therapy cycle, minimum heater temperature for a heater cycle and/or therapy cycle, ratio of duty cycle, length of therapy cycle, number of duty cycles within a therapy cycle, and number of therapy cycles in a therapeutic sequence. Different duty cycles within a therapy cycle may be programmed to have different peak heater temperatures and/or heater cycles may have average heater temperatures over that therapy cycle. Different therapy cycles within a therapeutic sequence may be programmed to have different peak heater temperatures and/or average heater temperatures over each therapy cycle. The wound covering control is operator-programmable or may have preprogrammed duty cycles, therapy cycles, and therapeutic sequences selectable by the operator. 
     The input control may take several forms. One form of input control is a temperature feedback from a temperature sensor placed proximate the selected area of treatment to monitor the target tissue temperature response. The sensor provides to the input control, a sequence of temperature values for the target tissue of the selected treatment area. Programmability may provide for variable heater output dependent on the actual target tissue temperature as well as the rate of target tissue temperature change within the selected treatment area. 
     Another form of input control is for the controller of the present invention to follow a temperature treatment paradigm programmable within the controller which is based on one or more parameters derived empirically, such as: the thermodynamic characteristic of tissue, the heat conduction rate of tissue types, the wound location, the wound type, the wound stage, the wound blood flow, the tissue surface area involved in the selected treatment area, the tissue volume involved in the selected treatment area, the heater geometry, the heater output, the heater surface area, and the ambient temperature. This paradigm programming provides an operator the ability, when selecting a treatment mode or method, to take into account all of these parameters. More importantly, the operator is able to tailor a treatment mode based on the type of wound to be treated. For example, wound types, such as wounds secondary to arterial insufficiency verse those secondary to venous insufficiency, or the location of the tissue on the body, for example, the leg versus the sacrum or abdomen, are sufficiently different so as to necessitate different heater treatment methods that take into account the myriad number of differences between wound types. One or more parameters are inputted to the controller to provide a sequence of target tissue temperatures over time to the heater controller based on the parameters used. 
     A preferred form of the wound covering includes an attachment as a peripheral sealing ring which, in use, completely surrounds the area of the wound and periwound, i.e., the selected treatment area. The upper surface of the peripheral sealing ring is spanned by a continuous layer which is preferably transparent and substantially impermeable, although the present invention also anticipates the use of a gas permeable layer suitable for some applications. Once in position, the sealing ring and the layer define a wound treatment volume which surrounds the wound. Additionally, the layer spanning the peripheral sealing ring maybe sealed about the periphery of the sealing ring and act as a barrier layer over the wound treatment volume. Optionally, the heater may be incorporated into the barrier layer or the barrier layer may be incorporated into the heater. An adhesive and a suitable release liner is applied to the lower surface of the peripheral sealing ring to facilitate the application of the wound covering to the patient&#39;s skin. 
     The barrier layer may include a pocket adapted to receive an active heater. An alternate form of the invention provides for the transport of heated air from a remote heat source to the wound treatment volume. In the active heater embodiments a thermostat and/or a pressure-activated switch may be used to control the heating effects of the heater. Passively heated embodiments are contemplated as well. These passive versions of the device include the use of thermally insulating coverings which retain body heat within the treatment volume. These reflectors or insulators may be placed in a pocket formed in the barrier layer. Each of these heated embodiments promote wound healing by maintaining the wound site at a generally elevated, but controlled, temperature. 
     In general, the peripheral sealing ring is made from an absorbent material which may act as a reservoir to retain and/or dispense moisture into the treatment volume increasing the humidity at the wound site. The reservoir may also contain and deliver medicaments and the like to promote healing. 
     The present invention is designed to directly elevate the temperature of the hypothermic skin and subcutaneous tissue of the selected wound area to a temperature which is close to or at normothermia. The purpose of this device is to create within the wound and periwound tissues of the selected treatment area a more normal physiologic condition, specifically a more normothermic condition, which is conducive to better wound healing. The present invention anticipates the use of an active heater that creates a heat gradient from heater to wound and periwound tissues. The usual temperature gradient for tissues goes to about 37° C. deep in the body core down to about 32° C. at the skin surface of the leg. The heater of the present invention operates in an output range suitable to raise the temperature of the selected treatment tissue from its pretreatment temperature to not more than 38° C. 
     In contrast, typical local heating therapy (e.g. hot water bottles, hot water pads, chemical warmers, infrared lamps) deliver temperatures greater than 46° C. to the skin. The goal of traditional heating therapy is to heat the tissue above normal, to hyperthermic temperatures. 
     The present invention differs from infrared lamps two ways. First, the present invention includes a dome over the wound that is relatively impermeable to water vapor transmission. After application of the bandage, moisture from the intact skin or wound evaporates, and air within the dome quickly reaches 100% relative humidity. The interior of the present invention is now warm and humid. For example, a 2.5 square inch bandage at 28° C. requires only 0.0014 g of water to reach saturation. When the air is thus saturated, no further evaporation can occur and, therefore, no drying of the wound can occur. This equilibrium will be maintained as long as the bandage is attached to the patient. 
     When heat is provided by the preferred embodiment of the present invention, the absolute amount of water needed to reach 100% relative humidity is slightly increased since warm air has a greater capacity for holding moisture. However, the air within the dome of the bandage still reaches water vapor saturation very quickly, and no further evaporation occurs. For example, a 2.5 square inch bandage of the present invention at 38° C. requires only 0.0024 g of water to reach saturation. Excess moisture is absorbed by the foam ring, but still is retained within the bandage. The enclosed dome design maintains 100% humidity over the wound which also prevents evaporation due to the heat. As long as the humidity is retained within the bandage, heating therapy could theoretically be continued indefinitely without causing the wound to dry. In contrast, when using infrared lamps, the wounds are open and exposed to the environment. The result is excessive drying of the wound, increasing tissue damage. 
     Secondly, the present invention operates at low temperatures, from above ambient to about 38° C. This causes only minimal heating of the skin. In contrast, infrared lamps operate at temperatures in excess of 200° C. These lamps heat the wound to hyperthermic temperatures which can cause thermal damage to the tissue of the wound. 
     At the low (normothermic) opening temperatures of the present invention, the heat transfer to the skin is minimal. The low wattage heater, the inefficiencies of the heat transfer into the tissue, the thermal mass of the tissue and the blood flow (even if markedly reduced), all prevent the wound temperature from reaching the heater temperature. Hypothermic wound tissue is warmed as a result of “migration” of the body&#39;s core temperature zone toward the local wound area. 
     The following data document the tissue temperatures resulting from a 38° C. heater of the present invention on: 
     
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Average 
                 Maximum 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Normally perfused human skin 
                 36° C. 
                 36° C. 
               
               
                   
                 Arterial/diabetic foot ulcers 
                 32° C. 
                 35° C. 
               
               
                   
                 Venous/arterial leg/foot ulcers 
                 33° C. 
                 35° C. 
               
               
                   
                 Non-perfused human model 
                 35° C. 
                 35° C. 
               
               
                   
                   
               
             
          
         
       
     
     When warmed with a 38° C. heater, wounds on poorly perfused legs reach stable average temperatures of 32-33° C. In contrast, normally perfused skin reaches 36° C. It is important to note that these data are contradictory to the assumption that poorly perfused tissue would reach a higher temperature than normally perfused tissue. This result substantiates the physiologic finding that the “migration” of the core temperature zone toward the local wound zone, decreasing the gradient difference between the core and surface temperatures, is the cause for the observed increase wound temperatures. Core temperature regulation is heavily dependent on perfusion, and migration of the core temperature zone is also heavily dependent on perfusion. At no point in time did the poorly perfused tissue reach normothermia. Consequently, poorly perfused legs are much colder than normally perfused legs, and, thus, poorly perfused legs constitute a substantially deeper heat-sink. 
     A wound-healing pilot study is under way, studying patients with chronic arterial and/or venous ulcers of the lower leg. These patients have suffered from these ulcers for many months and, in some cases, even years, despite aggressive medical and surgical therapy. Of 29 patients enrolled, 24 have completed the study protocol or are still being treated. Of these 24 patients, 29% are completely healed, and 38% show a significant reduction of the wound size within 2-5 weeks of receiving therapy with the present invention. 
     A known consequence of restoring normothermia to tissues is to induce some degree of vasodilatation which increases local blood flow. Preliminary data collected during trials of the present invention, studying the effects of the present invention on normal subjects and on wound healing, has borne this out. An added effect has been to increase the partial pressure of oxygen in the subcutaneous tissues (P sq O 2 ), which is an indirect indicator of the status of the tissue. The higher the P sq O 2 , the greater the likelihood the tissue will benefit and improve the healing process. The results of some of these studies are presented in Tables 1-4. 
     In conducting the studies presented in Tables 1-4, a wound covering according to the present invention is placed over the skin. The temperature of the subcutaneous tissue is then measured over time. From −60 minutes to the 0 minute mark, the heater is off in order to obtain a baseline temperature. At the 0 minute mark the heater is activated and its temperature kept constant over the next 120 minutes when it is turned off. Temperature measurements were taken during this 120 minute period and for an additional 180 minutes after turning the heater off. As shown in Table 1, with activation of the heater to 38° C., the subcutaneous tissue temperature rapidly rose from about 34.3° C. to about 36° C. over the first 30 minutes. The temperature of the subcutaneous tissue continued to slowly raise over the next 90 minutes to a temperature of about 36.7° C. After turning the heater off, the temperature of the subcutaneous tissue fell to about 35.9° C. and held this temperature fairy uniformly for at least the next 120 minutes. 
     Table 2 presents the skin temperature data collected from within the wound cover of the present invention for the same periods as those in Table 1. The general curve shape is similar to the subcutaneous tissue temperature curve. The baseline temperature at the 0 minute mark was about 33.5° C. After turning the heater on to 38° C., the skin temperature rose rapidly to about 35.8° C. in the first 30 minutes, then slowly rose to about 36.2° C. by the end of the 120 minute heating period. After turning the heater off, the skin temperature fell to about 35° C. and held there for at least the next two hours. 
     Table 3 represents laser Doppler data collected from the tissue during the experiments and correlates to blood flow through the local area being treated with heat. The baseline flow is approximately 80 ml/100 g/min and rises to about 200 ml/100 g/min at its peak, half way through the heating period. The flow “normalizes” back to baseline during the last half of the heating period and remains at about baseline for the remainder of the measuring period. 
     The change in P sq O 2  is followed in Table 4. The baseline P sq O 2  is about 75 when heating begins and rises steadily to about 130 by the end of the heating period. The P sq O 2  remains at this level for the remainder of the measuring period despite the lack of heating for the last 180 minutes. The added benefit of increased P sq O 2  by heating continues well into the period of time after active heating has ceased. Wounds will continue to benefit from the effects of heating for substantial periods of time after the heating is turned off. The consequences of this study with the present invention is that the heating need not be constant, but deliverable over a heater therapy cycle or cycles that may or may not be part of a larger therapeutic sequence. 
     Similar trials were conducted using a heater temperature of 46° C. This data is presented in tables 5-8. Only slight additional benefits were found in any of the four measured parameters when studied at this higher temperature. The benefits imparted by active heating according to the present invention seem to peak at about 46° C. In many instances, 43° C. appears to be the optimal temperature for maximal efficiency in terms of least energy required for the greatest therapeutic gain. 
     Our initial human clinical data shows that the beneficial effects of heating on blood flow and P sq O 2  last at least one hour longer than the actual duration of heat application. Further, we have noted that cycled heating seems to be more effective for wound healing than continuous heating. Therefore, the data recommends cycling the heater in a therapy cycle (e.g. 1 hour “on” and 1 hour “off”) for a total heating time of 2-8 hours per day as a therapeutic sequence. 
     None of the 29 patients with compromised circulation treated to date have shown any indication of skin damage due to 38° C. heat. Furthermore, none of these wounds have exceeded 35° C. tissue temperature, with an average wound temperature of 32-33° C. The present invention raises the wound temperature toward normothermia, but even on a poorly perfused leg, the tissue does not reach normothermia. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Illustrative but not limiting embodiments of the invention are shown in the attached drawings. Throughout the several figures like reference numerals refer to identical structure throughout, in which: 
     FIG. 1A is an exploded view of a wound covering according to the present invention; 
     FIG. 1B illustrates an assembled view of the wound covering of FIG. 1A; 
     FIG. 2A is a view of an alternate wound covering; 
     FIG. 2B is a view of an alternate wound covering of FIG. 2A with passive heating card inserted in the wound covering; 
     FIG. 3A is an exploded view of an additional alternate wound covering; 
     FIG. 3B is an assembled view of the wound covering of FIG. 3A; 
     FIG. 4 is a side elevation view of a wound covering; 
     FIG. 5 is an enlarged top plan view of a wound covering; 
     FIG. 6 is an enlarged sectional view taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is a bottom view of the wound covering of FIG. 4; 
     FIG. 8A is an exploded view of an alternate wound covering: 
     FIG. 8B is an assembly view showing the air flow through the wound covering; 
     FIG. 9A is a perspective view of an alternate wound covering; 
     FIG. 9B is a side view of the wound covering of FIG. 9A; 
     FIG. 10 is a perspective view of an alternate wound covering; 
     FIG. 11A is a perspective view of an alternate wound covering; 
     FIG. 11B is a side elevational view of the wound covering of FIG. 11A; 
     FIG. 11C is a view of the wound covering of FIG. 11A; 
     FIG. 12 is a perspective view of an alternate connector apparatus for the wound covering; 
     FIG. 13A is an alternate connector arrangement for the wound covering; 
     FIG. 13B is a side sectional view of the wound covering of FIG. 13A; 
     FIG. 14 is a view of a rigid connector for engagement with a wound covering; 
     FIG. 15 is an alternate fluid inlet line for the wound covering; 
     FIG. 16A is a view of a two ply barrier layer wound covering; 
     FIG. 16B is a side elevational view of the wound covering of FIG. 16A; 
     FIG. 17 is an alternate wound covering; 
     FIG. 18A is an alternate wound covering; 
     FIG. 18B is a side sectional view of the wound covering of FIG. 18A; 
     FIG. 19 is a side elevational view of an alternate wound covering 
     FIG. 20 is a schematic diagram of an embodiment of the present invention; and 
     FIG. 21A is a schematic representation of an alternate embodiment of the heater array distribution shown in FIG. 20; 
     FIG. 21B is a schematic representation of an alternate embodiment of the heater array distribution shown in FIGS. 20 and 21A; 
     FIG. 21C is a schematic representation of an alternate embodiment of the heater array distribution shown in FIGS. 20,  21 A, and  21 B; 
     FIG. 21D is a schematic representation of an alternate embodiment of the heater array distribution shown in FIGS. 20,  21 A,  21 B, and  21 C; 
     FIG. 22 is a graphical representative sample of an operational scheme for an embodiment of the present invention, such as the embodiment shown in FIG. 20; 
     FIG. 23 is a graphical representative sample of an additional operational scheme for an embodiment of the present invention, such as the embodiment shown in FIG. 20 using the scheme depicted in FIG. 22; and 
     FIG. 24 is a graphical representative sample of another additional operational scheme for an embodiment of the present invention, such as the embodiment shown in FIG. 20 using the schemes depicted in FIGS.  22  and  23 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to a non-contact wound covering for controlling the local environment at a wound site on a patient. A wound site includes those portions of the patient&#39;s skin obviously definable as the wound area and the immediately adjacent periwound area as the selected treatment area of the wound site. The wound covering protects the wound from contamination by materials from the outside environment and also prevents the wound site from shedding contaminants into the local environment of the patient, i.e. the hospital room. The treatment volume formed proximate the wound site can be controlled to create an optimal healing environment. The word “wound” as used herein refers generically to surgical incisions, ulcers, or other lesions or breaks in the skin. 
     First, a substantially vertical wall is provided to encircle the selected treatment area on the surface of the patient&#39;s skin. This vertical wall provides an upper surface to support a layer spanning this structure above the level of the wound and a lower surface suitable for attachment to the patient&#39;s skin. This structure is referred to throughout as an attachment or a peripheral sealing ring. Together these elements form a wound treatment volume between the layer and the surface of the selected treatment area. The fact that the layer does not contact the wound itself promotes healing by minimizing mechanical stresses on the tissues. The lower surface suitable for attaching to the skin may include an adhesive and a complimentary release liner assembly to facilitate the attachment of the wound covering to the skin of the patient. The present invention anticipates using a heater such that the layer may comprise the heater formed as the layer or as a layer which includes a heater within some portion of the layer. The layer may also include functioning as a barrier layer completely enclosing the wound treatment volume. 
     In accordance with the present invention, the climate within the wound treatment volume may be controlled. Typically the temperature, humidity, and gas composition, for example adding oxygen, nitric oxide or ozone, are controlled. Also, aerosolized medications or compounds may be released into this volume as well. The above list is exemplary of the climate controls which may promote healing of the wound, and is not intended to limit the scope of the present invention. It will be understood by those skilled in the art that numerous other climate factors can be controlled within the treatment volume of the present wound covering system without departing from the scope of the invention. 
     FIG. 1A illustrates an exploded view of a wound covering  50 . In this embodiment, a peripheral sealing ring  52  is substantially square in outline. Peripheral sealing ring  52  is intended to be attached to uninjured skin surrounding a selected treatment area  54  using an adhesive  56 . In this embodiment, a layer of adhesive hydrogel is shown as the adhesive  56 . Additionally, peripheral sealing ring  52  is preferably constructed of an open cell hydrophilic foam plastic having a sealed outer surface  58  which isolates the wound from the environment. The peripheral sealing ring is fabricated from a material which may conform to the curved surface of the patient&#39;s body. An inner surface  60  of sealing ring  52  is preferably porous or absorbent so that it can form a reservoir to contain and release moisture or water vapor into the air within a treatment volume  62  to create a high humidity environment if desired. Additionally, the hydrophilic absorbent nature of peripheral sealing ring  52  absorbs fluids and blood weeping from the wound. 
     A layer  64  is preferably attached to an upper surface  66  of peripheral sealing ring  52  as a barrier layer to seal treatment volume  62 . Layer  64  is preferably constructed of a flexible synthetic polymeric film, such as polyethylene, polyvinyl chloride, polyurethane, or polypropylene. Additionally, other polymeric films, natural and semi-synthetic, that are suitable for use in medical applications such as cellulose and cellulose acetate, may be used. A wound tracing grid  68 , also constructed of a substantially clear flexible material, may optionally be used as, or attached to, layer  64  to facilitate wound care management so that the physician can draw an outline of the wound as an aid to tracking the healing process of the wound. The wound tracing grid preferably contains a labeling area  70  for identifying the patient, date when the wound was traced, and other patient medical data. 
     It will be understood by those skilled in the art that the volume of peripheral sealing ring  52  will depend on the structural strength of the support material and the amount of fluid absorption desired. Additionally, the total area of peripheral sealing ring  52  is dependent on the size of the wound. For example, larger wounds and more flexible covers will require a thicker sealing ring so that the center of the cover does not touch the wound. 
     Upper surface  66  of peripheral ring  52  is preferably sealed by extending barrier layer  64  over the entire area of upper surface  66  as shown in FIGS. 1A and 1B. Adhesive  56  for attaching peripheral sealing ring  52  to uninjured skin surrounding selected treatment area  54  may take any form, however, the preferred adhesive is preferably a two-faced hydrogel which attaches to a lower surface  72  of peripheral sealing ring  52 . This adhesive  56  permits the attachment of peripheral sealing ring  52  to the patient&#39;s skin. Finally, peripheral sealing ring  52  may serve as a reservoir for retaining water or medicaments in treatment volume  62  in order to maintain a high humidity in the air within the volume. Water may be added to peripheral sealing ring  52  at any time during treatment. 
     It will be understood by those skilled in the art that peripheral sealing ring  52  can be supplied in a variety of shapes and sizes to accommodate various wounds. The shapes may include circles, squares, or rectangles. Although it is preferred to dispense the wound covering as a unitary assembly it should be apparent that individual segments of peripheral ring material could be assembled into any shape necessary to form a perimeter around the wound area. Likewise barrier layer  64  and wound tracing grid  68  could be provided in large sheets which may be cut to size and then attached to the peripheral sealing ring. 
     FIG. 1B is an assembled view of wound covering  50  of FIG.  1 A. To dispense the assembled product, a release liner  74  of FIG. 1B is applied to adhesive  56  in FIG.  1 A. Release liner  74  may span the entire lower surface of the covering to maintain the sterility of treatment volume  62 . Release liner  74  preferably has a grip tab  76  to facilitate removal of release liner  74  from wound covering  50  immediately prior to application of wound covering  50  to the skin of a patient. 
     FIGS. 2A and 2B illustrate an alternate embodiment of the present invention as a wound covering  80  utilizing passive heating of the treatment volume  62 . Because heat is constantly being radiated from the patient&#39;s skin surface, the insulation properties of the trapped air within treatment volume  62  will reduce this heat loss. By adding an infrared reflector  82  over treatment volume  62 , the infrared heat from the body can be reflected back to the skin for added passive heating. 
     An edge  84  of wound tracing grid  86  is preferably not attached to the barrier layer to form an envelope or a pocket  94  between the wound tracing grid  86  and the barrier layer. A piece of reflective foil material  88  may be inserted into pocket  94 . A thin layer of insulating material  90  may be optionally attached to foil layer  88  to enhance heat retention and to provide foil layer  88  with additional resiliency. A tab  92  is preferably attached to infrared reflector  82  to allow easy insertion and removal from pocket  94  and wound covering  80 . 
     FIGS. 3A and 3B illustrate a preferred alternate embodiment of a non-contact wound covering  108  utilizing active heating of a treatment volume  112 . Wounds may be safely and easily heated utilizing a heater assembly  100 . Heater assembly  100  alternatively comprises a pressure-sensitive switch  102 , an insulating layer  104 , and a foil heater  106 . 
     Pressure-sensitive switch  102  is optionally laminated to the upper surface of heater assembly  100 . The purpose of switch  102  is to shut off power to foil heater  106  in the event that external pressure is applied to wound covering  108  with sufficient force to cause foil heater  106  to contact the skin or wound below. This feature prevents the possibility of applying heat and pressure to the skin at the same time. The combination of heat and pressure is known to cause burns even at low temperatures (40° C.) because the pressure prevents blood flow in the skin making it susceptible to thermal injury. Pressure-sensitive switch  102  preferably covers the entire area of heater assembly  100  so that pressure applied anywhere to the surface of heater assembly  100  will deactivate foil heater  106 . 
     It will be understood by those skilled in the art that a variety of devices are suitable for use as pressure-sensitive switch  102 . Force sensing resistors, resembling a membrane switch, which change resistance inversely with applied force are one such example of a pressure sensitive switch. Devices of this type offer the substantial advantage of being low cost, flexible, and durable. A variety of other force sensing switch devices may be utilized as well. 
     An alterative safety feature anticipated by the present invention is a monitoring function for detecting dramatic increases in power utilization by the heater trying to maintain an operating temperature. Under normal operation, the heater is in a non-contact position proximate the selected treatment area and the heater will have been programmed to operate at a temperature that may be either a straight temperature value or an averaged value for either a duty cycle, therapy cycle or therapeutic sequence. If physical pressure is placed on the heater and it comes into contact with the patient&#39;s body, there will be a considerable increase in the rate of heat loss from the heater because of the body&#39;s greater heat sink capacity. The heater controller would sense this drop in temperature and initially adjust either the duty cycle ratio or power output, or both, in an attempt to compensate for the increase rate of loss. The safety aspect of this monitoring function would be to override this increase and turn off the device, thus preventing heating the tissue while in direct contact with, and under pressure from, the heater. 
     Heater element  106  is preferably a thin film type resistance heater which is commercially available. Such thin film resistance heaters utilize low voltage, minimizing the electrical risk to the patient and allowing for battery-powered mobility. Foil heater  106  is preferably sized for each wound covering  108 . In actual use, foil heater  106  is preferably provided in sheets with a pair of electrical leads  110  along one edge. While an electrical resistance heater is the preferred embodiment of the invention, other heating devices are anticipated such as warm water pads, exothermic chemical heating pads, and phase-change salt pads. 
     Heater assembly  100  is preferably insertable into a pocket  114  formed between wound tracing grid  86  and the barrier layer as discussed above. Finally, a temperature monitoring device, such as a liquid crystal temperature monitor, may be applied to an upper surface of heater assembly  100  or within treatment volume  112  to monitor the temperature within treatment volume  112 . 
     FIGS. 4-7 illustrate an alternate embodiment of wound covering  10 . In this embodiment, wound covering  10  includes a generally circular head, designated generally at  12 , which transitions to an elongated non-kinking, collapsible air supply or hose  14 . 
     The apparatus, as illustrated in FIG. 4, is connected by suitable supply line or tube  16  to a source  18  of thermally controlled air which is schematically illustrated. The term air as used herein is intended to encompass mixtures of gases of controlled composition. The apparatus is constructed to apply a continuous stream of thermally controlled air to a wound treatment volume. 
     The specific form of the apparatus and details of construction can best be understood by reference to the various figures. The overall appearance of the wound covering is best seen in FIG.  4  and FIG.  5 . It is preferred to construct the apparatus from top and bottom sheets of thin heat-sealable polymer film which overlay one another. A top sheet or membrane  20  overlies a bottom sheet or membrane  22  which are heat sealed together along a plurality of seal lines, including a continuous outer seam  24 , which extends in a circle around head  12  and continues in a sinusoidal or convoluted fashion along and forming hose  14 . An inner continuous circular seam  26  is provided as best seen in FIGS. 6 and 7. This inner seam  26  secures the sheets together along a continuous circle to form the inner wall of a torus defining a supply volume  28 . 
     The inner circular portion of the two sheets  20 ,  22  lying in the plane within the center of the supply volume  28  forms a wall  30  separating a lower wound treatment volume  32  from an upper insulation chamber  34 . Wall  30  includes a plurality of apertures  36  formed by making small circular seals  38  and cutting and removing circular portions within the circular seals  38 . Thus, wall  30 , with a plurality of apertures  36 , is formed between the wound treatment volume  32  and insulation chamber  34 . A plurality of apertures  40  are formed in the common circular wall surrounding treatment volume  32  for distributing and conveying heated air or gases from supply volume  28  into wound treatment volume  32 . 
     The heated air flowing into treatment volume  32  bathes the wound surface of a patient&#39;s body  42 . The air circulates throughout wound treatment volume  32 , and then passes through apertures  36  into the upper or insulating chamber  34 , where it the passes through filter  44  forming an outer wall of insulation chamber  34 . Filter  44  filters the air leaving wound treatment volume  32 , trapping contaminants shed from the wound. Filter  44  may be constructed of a filter paper bonded along its periphery to the outer tangential walls of head  12  forming the torus. The filter paper also provides an insulating layer which suppresses loss of heat by radiation through upper wall  30 . 
     The lower surface of the head  12  as shown in FIGS. 6 and 7 is provided with a peripheral sealing ring  46  made of an absorbent material such as foam and bonded by a suitable adhesive to the walls of head  12  and skin  42  of the patient around the wound. Preferably, foam or cotton peripheral seal ring  46  is provided with a peel-off tape so that it adheres to the wall of the housing and on the other side to the skin of the patient. The adhesive or tape holds the apparatus in place and prevents airflow escape between the device and the skin of the patient. The absorbent material of the ring absorbs weeping blood and fluids and insulates the skin from direct conduction of heat from head  12 . 
     Hose  14  is designed to be non-kinking by forming it of symmetrically convoluted flexible material. The hose and housing are integrally formed essentially of a unitary structure, such as a thin film membrane. Hose  14  is inflatable upon the application of heated air through supply line  16 . The indentations in hose  14  permit it to bend without kinking and, thus, differentiate from a straight tubular hose which may kink when bent. 
     Since the thermal body treatment apparatus of the invention and the supply hose section are formed from two, thin, sealed-together membranes, the hose, and in fact the entire apparatus, is collapsible. This prevents the possibility of applying heat and pressure to the skin as might happen if a patient rolled over on the device. Instead, the weight of the patient&#39;s body collapses the device, obstructing the flow of air, and preventing the application of heat. 
     The film membrane may preferably be transparent to enable viewing the wound without removal. However for cosmetic reasons the layer may be opaque. Filter paper  44  is attached across the tangential surfaces of the toroidal housing, thus providing a large area of filter for the escaping air. Head  12  of the apparatus may be about one foot in diameter for most applications. However, it may be made smaller for certain other applications. 
     FIG. 8A illustrates an exploded view of an alternate embodiment of a non-contact wound covering  120  with climate control within a treatment volume  122  as shown in FIG.  8 B. An inflatable structure  124  is preferably attached to a fluid inlet line  126  at a fluid inlet port  129  on the perimeter of inflatable structure  124 . Inflatable structure  124  is preferably attached to an absorbent peripheral sealing ring  128 , which is in turn attached to a wound area  54  by a suitable adhesive  56 . Peripheral sealing ring  128  preferably has a sealed outer surface and a porous inner surface which performs the same function as peripheral sealing ring  52  discussed above. A barrier layer  130  having an exhaust filter  132  is attached to a top surface  134  on inflatable structure  124 . 
     Turning now to the assembly illustrated in FIG. 8B, a gas, illustrated by direction arrows “A”, is introduced into inflatable structure  124  from an external source (not shown) through inlet line  126 . The gas pressurizes inflatable structure  124  in order to maintain barrier layer  130  and exhaust filter  132  in an elevated position relative to wound area  54 . An inner surface  136  of inflatable structure  124  preferably has a plurality of apertures  138  through which the fluid is introduced into wound treatment volume  122 . As pressure within the chamber increases, excess pressure is relieved through exhaust filter  132 . In this fashion, various fluids or gases can be introduced into wound treatment volume  122 . 
     The use of the term “fluid” in the context of this application refers to both liquid and gaseous materials, and combinations thereof. In one embodiment, oxygen may be introduced into treatment volume  122  through apertures  138  of inflatable structure  124 . The presence of oxygen within wound treatment volume  122  may increase the oxygen available to the superficial layer of growing cells in wound area  54 . Nitric oxide alternatively may be infused into treatment volume  122 . Nitric oxide (NO) is a potent vasodilator which in theory may be absorbed across the wound surface and increase localized blood flow. A very small concentration of NO (parts per million) may provide this effect. NO may also be pre-absorbed into absorbent peripheral sealing ring  128  and then allowed to passively diffuse into the volume once it is applied to the wound. Finally, gaseous or aerosolized medications or compounds may be introduced into the gas flow entering treatment volume  122 . 
     FIGS. 9A and 9B illustrate an alternate embodiment of the climate control system discussed above wherein a fluid inlet line  140  may form part of a barrier layer  142 . Barrier layer  142  is unitary with fluid inlet line  140  and is preferably attached to an exhaust filter media  144  to allow excess pressure to be released from a wound treatment volume  146 . In this embodiment, filter media  144  forms part of barrier layer  142 . The arrows “A” in FIG. 9B illustrate the movement of the fluid through fluid inlet line  140 , treatment volume  146 , and exhaust filter  144 . 
     FIG. 10 illustrates an alternate embodiment wherein an exhaust filter  154  is retained in a recess  150  formed in one side of a peripheral sealing ring  152 . This structure allows excess fluid to be exhausted through the side of peripheral sealing ring  152 , rather than through the top, as illustrated in FIGS. 9A and 9B. 
     FIG. 11A is a perspective view of the embodiment illustrated in FIG. 9A, wherein a connector  160  on the end of a fluid supply line  162  engages with an opening  164  on fluid inlet line  140 . FIG. 11B illustrates a side view of fluid supply line  162  as it engages with fluid inlet line  140 . FIG. 11C illustrates the embodiment in FIGS. 11A and 11B where fluid inlet line  140  is folded over the top of peripheral sealing ring  152  to seal treatment volume  146  when supply line  162  is uncoupled. 
     FIG. 12 illustrates an alternate embodiment in which a fluid inlet slot  170  engages with a rigid connector  172  on a fluid inlet line  174 . Fluid inlet slot  170  forms an opening in one portion of a peripheral sealing ring  176 . The opening is in fluid communication with a treatment volume  178 . This configuration allows for quick disconnection of fluid inlet line  174  from wound covering  180  providing the patient with additional mobility. 
     FIG. 13A is a perspective view of an alternate non-contact wound covering  190  having a fluid inlet connector  192  attached to a top surface  194  of a peripheral sealing ring  196 . Fluid inlet connector  192  preferably contains an inlet filter media  198 . A rigid connector  200  on a fluid inlet line  202  mates with fluid inlet connector  192 . As illustrated in FIG. 13B, a cover  204  extends from the top of fluid inlet connector  192  across the top of peripheral sealing ring  196  where it engages with an exhaust filter media  206 . FIG. 14 illustrates the embodiment of FIGS. 13A and 13B utilizing a non-disposable fluid supply line  210 . 
     FIG. 15 illustrates an alternate embodiment which utilizes a manifold structure  220  as part of a fluid inlet line  222  to provide even distribution of the fluid being introduced into a treatment volume  224 . Fluid inlet line  222  preferably has a series of seals  226  along its edge which are interrupted by a plurality of side openings  228  from which the fluid can be transmitted into treatment volume  224 . The embodiment disclosed in FIG. 15 illustrates an exhaust filter  230  recessed into the side of peripheral sealing ring  232 . However, it will be understood that a variety of exhaust filter configurations are possible with the disclosed manifold structure  220 . 
     FIGS. 16A and 16B illustrate an alternate wound covering  240  with a top barrier layer  242  and a lower layer  244  having a plurality of holes  246 . As is illustrated in FIG. 16B, a top cover  243  forms the barrier layer  242  and it extends substantially across the area of the peripheral sealing ring  248 . Lower layer  244  likewise extends across the peripheral sealing ring  248 . Thus, an upper insulating layer  250  is formed between lower layer  244  and the top of barrier layer  242 . Fluid in a fluid inlet line  252  is directed into upper insulating layer  250 . The pressurized fluid in upper insulating layer  250  passes through holes  246  into a treatment volume  254 . Holes  246  in lower layer  244  provide a generally even distribution of the fluid within wound treatment volume  254 . An optional seal  258  may be formed in the center portion of barrier layer  242  and lower layer  244  to provide these layers with additional structural support. An exhaust filter medium  256  is provided in a recess along one side of peripheral sealing ring  248  to relieve pressure in treatment volume  254 . 
     FIG. 17 illustrates an alternate embodiment of a non-contact wound covering  260  utilizing semi-rigid supports  262  to retain a barrier layer  264  above a wound area. It will be understood by those skilled in the art that a variety of semi-rigid supports  262  may be utilized for this application. For example, plastic or resilient rubber materials may provide sufficient support to barrier layer  264  with a minimum risk of injuring the patient. 
     FIGS. 18A and 18B illustrate an alternate exhaust filter medium  270  with an enlarged surface area to accommodate larger volumes of air flow through a non-contact wound covering  280 . Exhaust filter  270  is incorporated into a fluid inlet line  272 . Fluid inlet line  272  also forms a portion of a barrier layer  274 , which is in turn attached to a peripheral sealing ring  276 . As is best shown in FIG. 18B, fluid illustrated as the arrows “A” is introduced into a fluid inlet line  272 , where it is directed into a wound treatment volume  278 , past the wound area and out through exhaust filter medium  270 . 
     FIG. 19 illustrates a bi-directional line  290  with a center divider  292 . Fluid is introduced into a fluid inlet line  294  where it proceeds through a fluid inlet port  296  into a treatment volume  298 . The fluid then is forced through a fluid outlet port  300  where it is driven away from treatment volume  298  in a fluid outlet line  302 . It will be understood by those skilled in the art that it would be possible to utilize separate fluid inlet and outlet lines to achieve the same result. 
     A schematic diagram of an embodiment of the present invention using active heating and control is depicted in FIG. 20 as an active heater assembly  310  including a heater  312 , a heater filament  314  within heater  312 , a controller  316 , electrically coupled between heater filament  314  and a power source  318  by electrical connectors  315 , and using a tissue temperature sensor  320 , and an operator input interface  322  suitable for an operator to input programming parameters into controller  316 . Heater assembly  310  is useful in several different configurations, for example, as providing a heater layer for use directly in a pocket such as that depicted by heater  100  inserted into pocket  114  shown in FIGS. 3A and 3B or as a heat source for warming air that is circulated over the wound as is depicted in the several embodiments of FIGS. 4 through 19. 
     In addition to the various suggested fluid delivered heater “geometries” depicted in FIGS. 4-19, the present invention anticipates numerous possible heater electrical resistive filament  314  geometries. Examples of four such geometries are shown in FIGS. 21A, B, C, and D wherein there is depicted additional alternate heater array geometries for heating filament  314  within heater  312 . In FIG. 21A, there is depicted a linear geometry for heater filament  314 . This geometry is suitable for non-uniform heating where maximum heating is desired over a linear area, such as a linear surgical wound without direct heating over adjacent periwound areas. FIG. 21B depicts a geometry for heater filament  314  consistent more as a point source. FIG. 21C depicts an ovoid geometry for filament  314  suitable for non-uniform heating of selected periwound area. Alternatively, this non-uniform heating may be achievable with circular, square, rectangular, triangular or other such geometries depending on the type and shape of wound encountered. 
     In operation, heater assembly  310  is programmable, controlling one or more parameters, such as heater temperature, duty cycle, therapy cycle duration, number of duty cycles per therapy cycle, average heater temperature per duty cycle, and average heater temperature per therapy cycle. The programming may be preset at time of manufacture into controller  316  and provide a menu including treatment scenarios operator selectable at input interface  322 . Additionally, the parameter programmability may be entirely under the control of an operator through input interface  322  and suitable for inputting any number of custom treatment regimens. For example, one regimen anticipates that an operator may input a desired tissue temperature and the target tissue is then monitored through tissue temperature sensor  320 . 
     Alternatively, another regimen anticipates that an operator may input a treatment paradigm using parameters based on empirical modeling of tissue temperature responses for the various types of wounds, wound size, wound stage and wound location. Desired tissues targeted for monitoring may be the wound surface, the tissue below the wound surface, the periwound surface and tissue below the periwound surface. Empirical modeling may be based on parameters such as thermodynamic characteristics of tissue temperature conduction rates, surface area to be treated, tissue volume to be treated, wound type, wound location, wound staging, and heater geometries and heater outputs as a few of the paradigm values. Such programmable treatment paradigms are tissue temperature sensor independent and therefor tissue temperature sensor  320  is not needed in this mode. 
     By way of example, and not liming in scope of treatment versatility, FIG. 22 is a graphic representation of one such regimen. In FIG. 22, several heater duty cycles have been depicted as a curve  330  and the tissue temperature response as a curve  332 . Tune (t) is represented along the abscissa and temperature (T) along the ordinate. A tissue temperature target value T tar    334  has been entered either by program or direct input from the operator and the heater started at t 0    334 . The tissue start temperature is at a temperature T a    336  and the starting heater temperature is at ambient temperature T amb    338 . By turning on the heater at t 0    334 , the first of several duty cycles for the heater begins in order to provide heat with which to raise the tissue temperature to T tar    334 . A heater operating temperature T h    340  is chosen by the controller based on the value, either programmed or inputted, for T tar    334  and the heater controller provides the appropriate duty cycle ratio and heater cycle period so as to provide a safe and efficacious heating of at least a portion of the selected wound treatment area. The tissue target temperature T tar    334  value is reached at t 1    342 , at which time the heater is turned off. Alternatively, although not shown, upon reaching T tar    334 , the controller could have changed T h    340  to a lower value and kept the heater active in order to maintain the tissue temperature at T tar    334 . 
     By way of another example, and not limiting in scope of treatment versatility, a plurality of therapy cycles are depicted in FIG. 23, wherein individual heater cycles within each therapy cycle have been averaged out for purposes of clarification and for purposes herein are treated as the heater being “on”. A first therapy cycle begins at t 0    350  as depicted by the heater turning “on”, i.e., a series of heater cycles is begun as shown by a heater temperature curve  352 . A tissue temperature target value T tar    354  has been entered either by program or direct from the operator and the tissue temperature response is shown in a curve  356 . The tissue start temperature is at a temperature T a    358  and the starting heater temperature is at about ambient temperature T amb    360 . The heater remains “on” until the tissue temperature has reached T tar    354  as monitored directly or as predicted by an appropriate heating paradigm. As shown T tar    354  is reached at t 1    362  at which time the heater is turned “off”. As in the previous example, an alternative is that the heater controller selects an alternate heating output, chosen to maintain the tissue temperature at about T tar    354 . As depicted in FIG. 23, however, the tissue temperature is allowed to drift downwardly with the heater “off” until the tissue temperature reaches a temperature T min    364  that is either programmed or pre-selected as a value in the selected paradigm. Upon reaching T min    364 , the heater is turned “on” again, as shown at t 2    366 , so as to provide heat to the selected treatment area to raise the tissue temperature to T tar    354 . This first therapy cycle ends at t 2    366  when a second therapy cycle begins by turning “on” the heater again. As in the first therapy cycle, this second therapy cycle provides heat to the tissue to reach the tissue target temperature, T tar    354 . Alternatively this second therapy cycle may have a different T tar    354 , or optionally may have a different cycle length calling for the controller to change the heater output. The present invention anticipates the use of any number of therapy cycles having any length or duration per cycle and different set temperatures, and a plurality of therapy cycles contributing to a therapeutic sequence. 
     For the above examples, T tar    354  may be programmed as a paradigm or directly inputted into the controller. For the present invention, this tissue target temperature is in a range preferably from a pretreatment temperature to about 38° C. Another aspect of therapy control according to the present invention is the averaging of therapy cycle and therapeutic sequence tissue target temperatures, as depicted in FIG.  24 . The example is not intended to be limiting in scope of treatment versatility. 
     In FIG. 24, a therapy cycle starts at t 0    370  and ends at t 1    372 . The tissue target temperature average T ave    374  for this therapy cycle may be pre-selected or programmed. The tissue temperature change, as depicted by a temperature curve  376 , begins at a temperature T a    376 , rises as it is heated by the heater to T b    378  during the “on” phase of the heater, as depicted by a heater temperature curve  380 , and then drifts downwardly to T c    382  over an additional period of time such that the total period of time is equivalent to the period t 0    370  to t 1    372 . T ave    374  represents the average of the temperatures between T a    376  and T b    378 , or in the alternative the average between T a    376  and T c    382  over the time period t 0    370  to t 1    372 . 
     An alternative approach, also depicted in FIG. 24, anticipates the programming of a number of therapy cycles as elements of a therapeutic sequence, in this example there being two therapy cycles of varying times and tissue target temperatures. The present invention provides for the inputting of an average tissue target temperature T ave    384  for the therapeutic sequence, in this example, extending from t 0    370  to t 0    386 . Each of these average temperatures, whether an average over a therapy cycle or over a therapeutic sequence, is intended to have the same temperature range from a pretreatment temperature to about 38° C. A secondary consequence of this controller regimen is that if average temperatures are used, either over the therapy cycle and/or therapeutic sequence, then the resultant peak tissue temperature may be higher than this range. These peak temperatures are short lived by comparison and do not represent a safety concern. 
     The present invention is the development of a safe, efficacious non-contact heater wound covering providing heat to a patient&#39;s wound from the heater that warms a target tissue controlled to a temperature in a range from a pretreatment temperature to about 38° C., or controlled to an average temperature in a range from a pretreatment temperature to about 38° C. While the invention has been illustrated by means of specific embodiments and examples of use, it will be evident to those skilled in the art that many variations and modifications may be made therein without deviating from the scope and spirit of the invention. However, it is to be understood that the scope of the present invention is to be limited only by the appended claims. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Time 
                 Subcutaneous Temperature 
               
               
                   
                 (in minutes) 
                 (° C. mean ± S.D.) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 −60 
                 33.9 ± 1.1 
               
               
                   
                 0 
                 34.7 ± 1.2 
               
               
                   
                 30 
                 36.9 ± 0.6 
               
               
                   
                 60 
                 37.1 ± 0.4 
               
               
                   
                 90 
                 37.4 ± 0.5 
               
               
                   
                 120 
                 37.6 ± 0.5 
               
               
                   
                 180 
                 36.0 ± 0.4 
               
               
                   
                 240 
                 36.1 ± 0.2 
               
               
                   
                 300 
                 35.8 ± 0.6 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Time 
                 Skin Temperature Inside Covering 
               
               
                   
                 (in minutes) 
                 (° C. mean ± S.D.) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 −60 
                 33.2 ± 1.1 
               
               
                   
                 0 
                 33.9 ± 1.1 
               
               
                   
                 30 
                 36.7 ± 0.5 
               
               
                   
                 60 
                 37.0 ± 0.4 
               
               
                   
                 90 
                 37.1 ± 0.4 
               
               
                   
                 120 
                 37.2 ± 0.4 
               
               
                   
                 180 
                 35.2 ± 0.5 
               
               
                   
                 240 
                 35.2 ± 0.4 
               
               
                   
                 300 
                 35.1 ± 0.5 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Time 
                 Laser Doppler Flow 
               
               
                   
                 (in minutes) 
                 (ml/100 g/min mean ± S.D.) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 −60 
                 64 ± 42 
               
               
                   
                 0 
                 110 ± 100 
               
               
                   
                 30 
                 199 ± 191 
               
               
                   
                 60 
                 178 ± 131 
               
               
                   
                 90 
                 222 ± 143 
               
               
                   
                 120 
                 271 ± 235 
               
               
                   
                 180 
                 158 ± 146 
               
               
                   
                 240 
                 146 ± 125 
               
               
                   
                 300 
                 173 ± 158 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Time 
                 Subcutaneous Oxygen Tension (P sq O 2)   
               
               
                   
                 (in minutes) 
                 (mm Hg mean ± S.D.) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 −60 
                  54 ± 10 
               
               
                   
                 0 
                 110 ± 60 
               
               
                   
                 30 
                 109 ± 58 
               
               
                   
                 60 
                 122 ± 59 
               
               
                   
                 90 
                 136 ± 57 
               
               
                   
                 120 
                 159 ± 55 
               
               
                   
                 180 
                 153 ± 60 
               
               
                   
                 240 
                 156 ± 61 
               
               
                   
                 300 
                 148 ± 52 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                 Time 
                 Subcutaneous Temperature 
               
               
                   
                 (in minutes) 
                 (° C.) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 −60 
                 33.8 ± 1.5 
               
               
                   
                 0 
                 35.2 ± 1.5 
               
               
                   
                 30 
                 37.1 ± 1.1 
               
               
                   
                 60 
                 37.3 ± 0.8 
               
               
                   
                 90 
                 37.4 ± 0.7 
               
               
                   
                 120 
                 37.3 ± 0.8 
               
               
                   
                 180 
                 35.8 ± 1.2 
               
               
                   
                 240 
                 35.8 ± 1.0 
               
               
                   
                 300 
                 36.1 ± 0.9 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                 Time 
                 Skin Temperature Inside Covering 
               
               
                   
                 (in minutes) 
                 (° C.) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 −60 
                 32.9 ± 1.5 
               
               
                   
                 0 
                 34.5 ± 1.0 
               
               
                   
                 30 
                 37.1 ± 0.6 
               
               
                   
                 60 
                 37.5 ± 0.5 
               
               
                   
                 90 
                 37.6 ± 0.5 
               
               
                   
                 120 
                 37.6 ± 0.5 
               
               
                   
                 180 
                 34.9 ± 0.8 
               
               
                   
                 240 
                 35.0 ± 0.7 
               
               
                   
                 300 
                 35.2 ± 0.6 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 7 
               
               
                   
                   
               
               
                   
                 Time 
                 Laser Doppler Flow 
               
               
                   
                 (in minutes) 
                 (ml/100 g/min) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 −60 
                 44 ± 22 
               
               
                   
                 0 
                  95 ± 132 
               
               
                   
                 30 
                 142 ± 155 
               
               
                   
                 60 
                 191 ± 150 
               
               
                   
                 90 
                 207 ± 209 
               
               
                   
                 120 
                 161 ± 91  
               
               
                   
                 180 
                 73 ± 29 
               
               
                   
                 240 
                 70 ± 30 
               
               
                   
                 300 
                 71.5 ± 25   
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 8 
               
               
                   
                   
               
               
                   
                 Time 
                 Subcutaneous Oxygen Tension (P sq O 2 ) 
               
               
                   
                 (in minutes) 
                 (mm Hg) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 −60 
                  58 ± 11 
               
               
                   
                 0 
                 123 ± 73 
               
               
                   
                 30 
                 128 ± 67 
               
               
                   
                 60 
                 145 ± 69 
               
               
                   
                 90 
                 157 ± 73 
               
               
                   
                 120 
                 153 ± 55 
               
               
                   
                 180 
                 148 ± 73 
               
               
                   
                 240 
                 142 ± 73 
               
               
                   
                 300 
                 143 ± 76