Patent Publication Number: US-8123792-B2

Title: Perioperative warming device

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. 120 as a continuation of U.S. patent application Ser. No. 11/057,396 filed Feb. 11, 2005, now U.S. Pat. No. 7,276,076 B2, which is a continuation-in-part of U.S. patent application Ser. No. 10/895,672 filed Jul. 21, 2004, now abandoned. 
    
    
     This application contains subject matter related to the subject matter of the following patent applications, commonly owned herewith: 
     Patent Cooperation Treaty (PCT) Application No. PCT/US2003/11128, filed Apr. 10, 2003 for “Patient Comfort Apparatus and System”, and published Oct. 23, 2003 as WO 2003/086500; 
     PCT Application No. PCT/US2005/025355, filed Jul. 18, 2005, for “Perioperative Warming Device”, and published Feb. 23, 2006 as WO 2006/020170; 
     PCT Application No. PCT/US2005/043968, filed Dec. 6, 2005, for “Warming Device with Varied Permeability”, and published Jun. 15, 2006 as WO 2006/062910; 
     PCT Application No. PCT/US2005/044214, filed Dec. 6, 2005, for “Warming Device”, and published Jun. 15, 2006 as WO 2006/063027; 
     PCT Application No. PCT/US2006/004644, filed Feb. 9, 2006, for “Warming Device for Perioperative Use”, and published Aug. 17, 2006 as WO2006/086587; 
     PCT Application No. PCT/US2006/41028, filed Oct. 19, 2006, for “Multifunction Warming Device for Perioperative Use”, and published as Apr. 26, 2007 WO 2007/047917; 
     U.S. patent application Ser. No. 10/411,865, filed Apr. 10, 2003 for “Patient Comfort Apparatus and System”, and published Oct. 16, 2003 as U.S. 2003/0195596, now U.S. Pat. No. 7,001,416; 
     U.S. patent application Ser. No. 10/508,319, filed Sep. 20, 2004, for “Patient Comfort Apparatus and System”, and published Jun. 30, 2005 as U.S. 2005/0143796; 
     U.S. patent application Ser. No. 10/895,672, filed Jul. 21, 2004 for “Perioperative Warming Device”, now abandoned, published on Jan. 20, 2005, as U.S. 2005/0015127; 
     U.S. patent application Ser. No. 11/006,491, filed Dec. 7, 2004, for “Warming Device”, and published Jun. 8, 2006 as U.S. 2006/0122672; 
     U.S. patent application Ser. No. 11/057,396, filed Feb. 11, 2005, for “Perioperative Warming Device”, and published Aug. 17, 2006 as U.S. 2006/0184215; 
     U.S. patent application Ser. No. 11/057,397, filed Feb. 11, 2005, for “Thermal Blanket for Warming the Limbs”, and published Aug. 17, 2006 as U.S. 2006/0184216; 
     U.S. patent application Ser. No. 11/057,403, filed Feb. 11, 2005, for “Warming Device for Perioperative Use”, and published Aug. 17, 2006 as U.S. 2006/0184217; 
     U.S. patent application Ser. No. 11/057,404, filed Feb. 11, 2005, for “Clinical Garment for Comfort Warming and Prewarming”, and published Aug. 17, 2006 as US 2006/0184218; 
     U.S. patent application Ser. No. 11/260,706, filed Oct. 27, 2005, for “Patient Comfort Apparatus and System”, and published Mar. 9, 2006 as U.S. 2006/0052853; 
     U.S. patent application Ser. No. 11/363,136, filed Feb. 27, 2006, for “Forced Air Warming Unit”, and published Jul. 6, 2006 as U.S. 2006/0147320; 
     U.S. patent application Ser. No. 11/492,425, filed Jul. 25, 2006, for “Warming Device”, and published Nov. 16, 2006 as U.S. 2006/0259104; 
     U.S. patent application Ser. No. 11/583,432, filed Oct. 19, 2006, for “Multifunction Warming Device for Perioperative Use”, and published Apr. 26, 2007 as U.S. 2007/0093882; 
     U.S. patent application Ser. No. 11/583,477, filed Oct. 19, 2006, for “Multifunction Warming Device with Provision for Being Secured”, and published Apr. 26, 2007 as U.S. 2007/0093883; 
     U.S. patent application Ser. No. 11/583,480, filed Oct. 19, 2006, for “Multifunction Warming Device with Provision for Warming Hands”, and published Apr. 26, 2007 as U.S. 2007/0093884; 
     U.S. patent application Ser. No. 11/583,481, filed Oct. 19, 2006, for “Multifunction Warming Device with an Upper Body Convective Apparatus”, and published Apr. 26, 2007 as U.S. 2007/0093885; 
     U.S. patent application Ser. No. 11/656,777, filed Jan. 23, 2007, for “Convective Warming Device With a Drape”; and, 
     U.S. patent application Ser. No. 11/704,547, filed Feb. 9, 2007, for “A Forced Air Warming Unit”. 
     BACKGROUND OF THE INVENTION 
     A warming device for perioperative use includes a clinical garment and convective apparatus with multiple stacked, separately inflatable sections supported on the inside of the garment. 
     Convective devices that transfer heat to a human body are known. For example, there are devices that receive a stream of warmed pressurized air, inflate in response to the pressurized air, distribute it within a pneumatic structure, and emit the warmed air onto a body to accomplish such objectives as increasing comfort, reducing shivering, and treating or preventing hypothermia. These devices are typically called “convective thermal blankets” or “covers”. Arizant Healthcare Inc., the assignee of this application, makes and sells such thermal blankets under the BAIR HUGGER® brand. One such device is the Model 522 Upper Body Blanket. 
     Use of the term “convective” to denote the transfer of heat between a warming device and a body refers to the principal mode of heat transfer, it being understood that heat may at the same time be transferred between a convective warming device and a body by conduction and radiation, although not to the degree of convection. 
     A recent invention disclosed in the referenced PCT application adapts a clinical garment such as a robe or gown to receive a convective warming device in order to warm a person wearing the garment in a clinical setting for comfort and mobility of the person. Arizant Healthcare Inc., the assignee of this application, makes and sells such warming devices under the BAIR PAWS® brand. There is a need to further adapt such a combination for use perioperatively. 
     The term “perioperative” is defined in the  PDR Medical Dictionary , Second Edition, (Medical Economics Company, 2000), as “around the time of operation.” The perioperative period is characterized by a sequence including the time preceding an operation when a patient is being prepared for surgery (“the preoperative period”), followed by the time spent in surgery (“the intraoperative period”), and by the time following an operation when the patient is closely monitored for complications while recovering from the effects of anesthesia (“the postoperative period”). 
     According to Mahoney et al. (Maintaining intraoperative normothermia: A meta-analysis of outcomes with costs.  AANA Journal April  1999; 67, 2:155-164.), therapeutic warming is employed during at least the intraoperative period in order to prevent or mitigate a constellation of effects that result from hypothermia. In fact, it is increasingly manifest that maintenance of normothermia perioperatively enhances the prospects for a quick, successful recovery from surgery. The effectiveness of therapeutic warming depends upon delivery of enough heat to a patient&#39;s body to raise the patient&#39;s core body temperature to, or maintain it within, a narrow range, typically near 37° C. This range is called “normothermic” and a body with a core temperature in this range is at “normothermia.” Hypothermia occurs when the core body temperature falls below 36° C.; mild hypothermia occurs when core body temperature is in the range of 34° C. to 36° C. Therefore, “perioperative therapeutic warming” is warming therapy capable of being delivered during one or more of the perioperative periods for the prevention or treatment of hypothermia. 
     Therapeutic warming is contrasted with “comfort warming” which is intended to maintain or enhance a patient&#39;s sense of “thermal comfort”. Of course, therapeutic warming may also comfort a patient by alleviating shivering or a feeling of being cold, but this is a secondary or ancillary effect. Thermal comfort is a subjective notion; however, the environmental conditions necessary to produce a sense of thermal comfort in a population of human beings are known and well tabulated. For example, Fanger ( Thermal Comfort: Analysis and Applications of Environmental Engineering . Danish Technical press, Copenhagen, 1970) defines thermal comfort as “that condition of mind which expresses satisfaction with the thermal environment.” Even when a patient is normothermic, less than ideal environmental conditions can result in acute feelings of discomfort. Under normothermic conditions, thermal comfort is largely determined with reference to skin temperature, not core body temperature. Comfort warming is warming applied to a patient to alleviate the patient&#39;s sense of thermal discomfort. 
     Therapeutic warming may be indicated during any one or more of the perioperative periods. For example, for a short operation in a surgery with no warming equipment available, a person may be warmed preoperatively in a preparation area to raise mean body temperature to a level higher than normal in order to store enough thermal energy to maintain normothermia, without heating, intraoperatively. After surgery, it may be necessary to apply therapeutic warming in a recovery area to raise the core temperature to normothermia and maintain it there for a period of time while anesthesia wears off. Alternatively, for a long surgery in an arena with heating equipment available, a person may be warmed for comfort before surgery and warmed therapeutically during and after surgery. 
     Both therapeutic warming and comfort warming may be provided by convective devices such as convective thermal blankets that receive and distribute warmed, pressurized air and then expel the distributed air through one or more surfaces toward a patient in order to prevent or treat hypothermia in the patient. An example of use of such a device for therapeutic warming is found in U.S. Pat. No. 6,524,332, “System and Method for Warming a Person to Prevent or Treat Hypothermia”, commonly owned with this application. Comfort warming by convective means is described in the referenced U.S. patent application, and the referenced Publication No. WO 03/086500. 
     When delivered by convective devices, therapeutic warming is distinguished from comfort warming by intended effects and by the parameters of heat delivery that produce those effects. In this regard, a convective warming system typically includes a source of warmed pressurized air (also called a heater/blower unit, a forced air warming unit, a heater unit, etc.), a convective device such as a thermal blanket (which is, typically, inflatable), and a flexible conduit or air hose connecting the heater/blower unit with the thermal blanket. Use of such a system for a particular type of warming requires delivery of warmed air through a thermal blanket at parametric values that achieve a particular objective. The conditions by which a convective device such as a thermal blanket produces thermal comfort in normothermic individuals at steady state are significantly different from those necessary to treat hypothermia. Typically the conditions for thermal comfort are met in a system with a relatively low capacity heater/blower unit, while those in a therapeutic warming system are achieved with a relatively high capacity heater/blower unit. The different capacities have led to use of air hoses with different capacities, with those delivering air flow for thermal comfort typically having smaller diameters than those serving a therapeutic warming requirement. The result is a divergence of designs leading to installation of different air delivery infrastructures for therapeutic and comfort warming. 
     Health care cost is an issue of national importance. The cost of warming perioperatively is directly related to the number of perioperative periods in which a person is warmed; the cost increases when different warming apparatus are used in different periods to accomplish different goals. For example, when comfort and mobility are objectives of warming a person during the preoperative period and therapy is the objective of warming during one or more of the intraoperative and postoperative periods, it is presently necessary to use different warming configurations. Manifestly, if one warming device could be used or adapted to be used perioperatively, significant savings in thermal care could be realized. 
     SUMMARY 
     In one aspect, a perioperative warming device includes a clinical garment having an inside surface supporting a convective apparatus with stacked, separately inflatable sections. At least one section is adapted for comfort warming and at least another section is adapted for therapeutic warming. 
     In another aspect, a perioperative warming device includes a clinical garment and stacked convective apparatus in an integrated structure attached to the inside of the garment. At least one convective apparatus is adapted for comfort warming and at least another apparatus is adapted for therapeutic warming. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a person wearing a perioperative warming device constituted of a clinical garment and a convective apparatus with stacked sections mounted to the inside of the garment. 
         FIG. 2  illustrates a perspective view of the perioperative warming device looking into the clinical garment. 
         FIGS. 3A-3C  illustrate assembly of a convective apparatus. 
         FIGS. 4A and 4B  illustrate assembly of another convective apparatus. 
     
    
    
     SPECIFICATION 
     A perioperative warming device is constituted of a clinical garment and a convective apparatus with multiple stacked sections supported on an inside surface of the garment. In this regard, a “clinical garment” is a garment that is typically used to temporarily clothe a patient in a clinical setting. Such garments include hospital gowns, robes, bibs and other equivalents. The clinical setting may be a medical or dental office or clinic, a hospital, or any facility or institution that provides medical or dental treatment to patients. The convective apparatus has multiple stacked sections, preferably two sections sharing a common member. The sections may be separate. Each section may receive and distribute at least one stream of warmed pressurized air in a pneumatic structure and circulate the air through a permeable member to thereby convectively warm a person wearing the clinical garment. One section is adapted for comfort warming by convection, the other for therapeutic warming by convection. 
     In one aspect, a warming device for perioperative use may be worn on a person where it receives a first stream of warmed pressurized air in one section of the convective apparatus, distributes the pressurized air within the one section, and emits the air through a permeable sheet of the one section to convectively warm the person&#39;s body for comfort. In another aspect, a warming device for perioperative use may be worn on a person where it receives a second stream of warmed pressurized air in the other section of the convective apparatus, distributes the pressurized air within the other section, and emits the air through a permeable sheet of the other section to convectively warm the person&#39;s body for therapy. 
     In the perioperative warming device illustrated and discussed below, each of the sections of the convective apparatus is inflatable. That is, the structure of each section, flaccid when not in use, tautens when receiving a stream of pressurized air. 
     Refer now to  FIG. 1  in which a person  10  wearing a warming device  12  for perioperative use is shown. The perioperative warming device  12  is constituted of a clinical garment  13  and a convective apparatus with multiple stacked sections that is supported on an inside surface of the clinical garment  13 . The convective apparatus has for example two separate sections that share a common member, each of which has at least one inlet port through which the section may receive warmed pressurized air from a heater/blower unit (not seen). Each inlet port is accessible through an aperture in the clinical garment  13 . For example one inlet port  14  for one of the sections may be accessed through a lower flap  18  near the lower hem  25  of the clinical garment  13 . The lower flap is lifted and an air hose  19  with a nozzle  20  received in the inlet port  14  provides a pathway for a stream of warmed pressurized air to be conducted from a heater/blower unit  16  into the section through the inlet port  14 . An inlet port of another section may be accessed through an upper flap  18  near the left sleeve of the clinical garment  13 . 
     Convective apparatus such as thermal blankets have been specifically designed for particular uses. For example, a full body thermal blanket is adapted to lie upon the person and to extend longitudinally along the body of the person in order to cover substantially the person&#39;s entire body, from near the ankles or feet up to the neck. A lower body thermal blanket is adapted to lie upon the person and to extend longitudinally along the body of a person in order to cover the person&#39;s lower body, from near the ankles or feet up to the waist or pelvis of the person. An upper body thermal blanket has a bow-tie shape that is adapted to lie upon and extend transversely across the upper body of a person in order to cover the person&#39;s chest and extended arms. When fed a stream of warmed pressurized air, each of these thermal blankets inflates and distributes the air within itself. The pressurized air flows through apertures on a permeable surface of the thermal blanket which faces the person. These thermal blankets may have one, two, or more inlet ports through which an air hose provides warmed pressurized air from a heater/blower unit. The construction of thermal blankets is well understood. Examples of specific constructions are given in U.S. Pat. No. 5,620,482, U.S. Pat. No. 5,443,488, U.S. Pat. No. 5,360,439, and U.S. Pat. No. 5,304,213. 
     Most convective warming products are designed to provide a single mode of warming. Each of the thermal blankets described above is designed for therapeutic warming. The devices described in publication WO 03/086500 are designed for comfort warming. In contrast, the perioperative warming device described in this specification may provide either therapeutic warming or comfort warming, depending on the need. One section of the convective apparatus is constructed to provide comfort heating at steady state. Another section is constructed to provide therapeutic heating at steady state. 
     A convective apparatus with multiple sections is illustrated in  FIG. 2  supported on the inside surface  21  of the clinical garment  13 . In  FIG. 2 , the view is toward the inside of the clinical garment  13 , looking toward a permeable surface (indicated by the hash lines) of at least one section of the convective apparatus  68 ,  90 . 
     The convective apparatus  68 ,  90  has multiple sections. A “section” of the convective apparatus  68 ,  90  is a portion or division of the convective apparatus  68 ,  90  that may be inflated and operated separately from any other section of the convective apparatus  68 ,  90 . For example, the convective apparatus  68 ,  90  has two sections. A first section may be inflated and operated separately from the second section, and the second section may be inflated and operated separately from the first section. 
       FIG. 3A  illustrates assembly of a convective apparatus  68  by joining multiple sheets of material, with one of the sheets being common to both sections. An impermeable sheet  70  of material with a surface  71  has an inlet port  72  that opens through the sheet  70 , near its periphery. A first permeable sheet  75  of material has a notch  77  formed near its periphery at a location corresponding to the location where the inlet port  72  is provided. The first permeable sheet  75  has another inlet port  79  provided at another location near its periphery; the inlet port  79  opens through the first permeable sheet  75 . For example, the sheets  70  and  75  may have generally rectangular shapes with the inlet port  72  provided near a corner of the impermeable sheet  70  and the notch  77  provided at a corresponding corner of the first permeable sheet, and the inlet port  79  provided at a corner of the first permeable sheet  75  opposite the notch  77 . The first permeable sheet  75  is brought to the surface  71  of the impermeable sheet  70  and the sheets  70  and  75  are joined by a seal (“the first peripheral seal”) between the sheets along a trace that follows the peripheral outline of the first permeable sheet  75 . The sheets  70  and  75  may be further joined by seals at stake points within the first peripheral seal. Thus a first section of the convective apparatus  68  is constituted of the impermeable sheet  70 , the first permeable sheet  75 , and the inlet port  79 . The first section is an inflatable pneumatic structure with a permeable surface constituted of the outer surface of the first permeable sheet  75 . As can be appreciated, with warmed pressurized air flowing into the first section through the inlet port  79 , the first section will inflate and warmed pressurized air will circulate from within the section through the first permeable sheet  75 . A second section is formed by bringing a second permeable sheet  82  to the surface of the impermeable sheet  70  opposite the surface  71  and joining the sheets  70  and  82  by a seal (“the second peripheral seal”) between the sheets along a trace that follows the peripheral outlines of both sheets  70  and  82 . The sheets  70  and  82  may be further joined by seals at stake points within the second peripheral seal. Thus a second section of the convective apparatus  68  is constituted of the impermeable sheet  70 , the second permeable sheet  82 , and the inlet port  72 . The second section is an inflatable pneumatic structure with a permeable surface constituted of the outer surface of the second permeable sheet  82 . As can be appreciated, with warmed pressurized air flowing into the second section through the inlet port  72 , the second section will inflate and warmed pressurized air will circulate from within the section through the second permeable sheet  82 . As can further be appreciated, the first and second sections may be said to be stacked in that the sections have an orderly arrangement one on top of the other when the convective apparatus  68  has the orientation shown in  FIG. 3A . Further, the impermeable sheet constitutes a common element of the two sections. 
     In one aspect each of the inlet ports  72  and  79  may comprise a collar of relatively stiff material with an opening that is mounted to a sheet at an inlet port location. The opening in the collar of relatively stiff material coincides with an opening through the sheet on which it is mounted. Such inlet ports are taught for example in U.S. Pat. No. 6,666,879. Alternatively, each of the inlet ports may be a sleeve of material. The inlet port  79  of the first section has a smaller opening  79   b  than the opening  72   b  through the inlet port  72  of the second section. Consequently, the inlet port  79  accepts an air hose nozzle with a smaller diameter than the air hose nozzle diameter accepted by the inlet port  72 . The smaller nozzle diameter signifies a comfort warming air supply with an air hose having a smaller diameter than the air hose of a therapeutic warming air supply. Further, the smaller air hose may be coupled to a heater/blower unit with a smaller capacity than that of the heater/blower unit of the therapeutic warming air supply. The smaller-diameter, smaller-capacity comfort warming air supply ensures that the first section operates in response to a heater/blower unit designed for comfort warming, while the larger-diameter, higher-capacity therapeutic air supply ensures that the second section operates in response to a heater/blower unit designed for therapeutic warming. 
     In another aspect, the permeabilities of the sheets  75  and  82  may differ. In this regard, the permeability of each sheet may be inherent in the material of which the sheet is made, or it may result from an assembly step in which apertures are formed in the sheet, or both. In any event, to further adapt the sheets  75  and  82  for their respective roles (comfort warming and therapeutic warming), the permeability of the sheet  82  may be greater than the permeability of the sheet  75 . For example, the sheet  82  may have a permeability that is twice that of the sheet  75 . According to another example the difference between the permeability of the sheet  75  and the permeability of the sheet  82  may result from manufacturing steps in which apertures are formed in the sheet  75  and in the sheet  82 . In this example fewer apertures would be formed in the sheet  75  than in the sheet  82 ; for example sheet  75  would be manufactured to have no more than half the apertures of the sheet  82 . 
     With reference to  FIGS. 2 ,  3 A and  3 B, the convective apparatus  68  is supported in the clinical garment  13  on the inside surface  21  with the first permeable sheet  75 , and thus the first section, facing the inside surface  21  and the second permeable sheet  82 , and thus the second section, facing the interior of the clinical garment  13 . Accordingly, when a stream of warmed pressurized air is provided through the inlet port  79  for comfort warming, the warmed pressurized air circulates through the first permeable sheet  75  toward the inside surface  21  of the clinical garment  13 . When warmed pressurized air for therapeutic warming is provided through the inlet port  72 , the warmed pressurized air circulates through the second permeable sheet  82  toward the interior of the clinical garment  13 . In order to promote the circulation of warmed air for comfort warming to the interior of the clinical garment  13 , one or more vents opening through the sheets  70 ,  75 , and  82  may be provided as shown in  FIG. 3C . Each such vent  86  must be completely surrounded around its periphery by a seal between the sheets  70  and  75  and a seal between the sheets  70  and  82 . These seals are indicated in  FIG. 3C  by reference numeral  87 . 
     Another convective apparatus  90  is shown in  FIGS. 4A and 4B . According to the exploded view shown in  FIG. 4A , the convective apparatus  90  includes first and second impermeable sheets  91  and  92  of material and a permeable sheet  93  of material. For example, each of the sheets  91 ,  92 , and  93  may have a generally rectangular shape, with the sheets  91  and  93  having substantially equal dimensions and the sheet  92  being substantially as long as, but narrower than, the sheets  91  and  93 . Further, the sheet  92  is substantially centered between the long edges of the sheets  91  and  93 . Aligned concentric openings  96  and  97  are provided in the first and second impermeable sheets  91  and  92 , respectively. An inlet port  98  is mounted to the outside surface  99  of the first impermeable sheet  91 . Another inlet port  101  is provided near a periphery of the first impermeable sheet  91 , between an edge of the second impermeable sheet and the corresponding edge of the first impermeable sheet  91 . The inlet ports  98  and  101  may have a structure as described above in connection with  FIG. 3A . The second impermeable sheet  92  is brought to the surface  94  of the permeable sheet  93  and sealed thereto by interrupted lateral seals  103  and  104  and continuous end seals  105  and  106 . The first impermeable sheet  91  is brought to the surface  94  of the permeable sheet  93 , over the second impermeable sheet  92  and sealed to the surface  94  by a continuous seal  107  between the sheets  91  and  93  along their common periphery. Thus assembled, the second impermeable sheet  92  is sandwiched between the first impermeable sheet  91  and the permeable sheet  93 . As can be seen in  FIGS. 4A and 4B , this construction yields the convective apparatus  90  having a first section comprising the two permeable portions  108  and  109  of the permeable sheet  93  and a second section comprising the entirety of the permeable sheet  93 . In this regard, when a stream of warmed pressurized air is introduced through the inlet port  101 , the air flows into the first section and inflates the space between the sheets  91  and  93 , and the pressure of the air in this space forces the second impermeable sheet  92  against and blocks the flow of air through the portion of the permeable sheet  93  between the portions  108  and  109 . Consequently warmed pressurized air only circulates from the interior of the first section through the permeable portions  108  and  109 . When a stream of warmed pressurized air is introduced through the inlet port  98 , the air flows in the space between the sheets  92  and  93 , through the interrupted lateral seals  103  and  104  and inflates the structure between the sheets  92  and  93  and the structure between the sheets  91  and  93 . Air pressure in the structure between the second impermeable sheet  92  and the permeable sheet  93  keeps the second impermeable sheet  92  from contacting the permeable sheet  93 . Consequently warmed pressurized air circulates from the interior of the second section through substantially the entirety of the permeable sheet  93 . 
     The inlet port  101  of the first section has a smaller opening than the opening  96  through the inlet port  98  of the second section. Consequently, the inlet port  101  accepts an air hose nozzle with a smaller diameter than the air hose nozzle diameter accepted by the inlet port  98 . The smaller nozzle diameter signifies a comfort warming air supply with an air hose having a smaller diameter than the air hose of a therapeutic warming air supply. Further, the smaller air hose may be coupled to a heater/blower unit with a smaller capacity than that of the heater/blower unit of the therapeutic warming air supply. The smaller-diameter, smaller-capacity comfort warming air supply ensures that the first section operates in response to a heater/blower unit designed for comfort warming, while the larger-diameter, higher-capacity therapeutic air supply ensures that the second section operates in response to a heater/blower unit designed for therapeutic warming. 
     As can be appreciated, the first and second sections may be said to be stacked in that the sections have an orderly arrangement one on top of the other when the convective apparatus  90  has the orientation shown in  FIG. 4A . Further, the second impermeable sheet  92  and the permeable sheet  93  constitute common elements of the two sections. 
     An impermeable sheet or a permeable sheet described above may be a single sheet or may have a laminate structure. A laminate sheet structure may include a layer of extruded synthetic material lined with a layer of non-woven material. If the permeable sheet has a laminate structure, holes or apertures are formed through both layers of the sheet to provide a permeable surface through which warmed pressurized air can be circulated. For sealing to form a convective apparatus, such laminate sheets may be oriented to have the extruded layers facing, and the seals may then be formed by a gluing process or by a heating or ultrasonic process acting through one of the layers of non-woven material. Once constructed, the convective apparatus may be attached to the inside surface of the clinical garment by known means and mechanisms. 
     In another construction of a convective apparatus a permeable sheet may comprise a sheet of permeable material in which the apertures are interstices in the material structure on the condition that the permeable material be capable of being sealed to an impermeable sheet of material. 
     In yet another alternative construction of a convective apparatus such as the convective apparatus  90 , the clinical garment  13  may be constructed of a laminate sheet to which an apertured laminate sheet or a single sheet of permeable material, woven or non-woven, may be sealed. 
     Examples of non-woven material include any one or more of polyester, cotton, rayon, polypropylene, and wood pulp. Examples of extruded synthetic material include polypropylene, polyesters, and polyurethanes. Polyolefin plastics, including polyethylene, may provide the best results in terms of manufacturability since both woven and extruded materials may be made from them. Examples of attachment materials and mechanisms by which a convective apparatus as presented in  FIGS. 3A and 4A  can be attached to the inside surface  21  of the clinical garment  13  include two-sided adhesive, hook and loop, sewing, snaps, heat, ultrasonic, rivets, and any and all equivalents thereof. 
     The clinical garment  13  may be a standard gown, a modified gown or a special purpose gown. The gown may have a rear opening, a front opening or other suitable openings, such as a head opening in a poncho type gown. One type of gown shown in the figures has a rear opening. The clinical garment may be made of a woven cloth, such as cotton, or a non-woven such as spunbond-meltblown-spunbond material (SMS). 
     To secure the convective apparatus to a patient, a strip of double sided adhesive may be adhered along an edge of the device. During use of the perioperative warming device  12 , a release liner may be removed from a surface of the strip facing the patient and adhered to the patient to prevent unintended movement of the convective apparatus  68 ,  90  during warming. 
     In use, a person is warmed perioperatively using a warming device constituted of a clinical garment and a dual-section convective apparatus supported on an inside surface of the clinical garment by dressing a person with the clinical garment during the preoperative period, coupling a first section of the convective apparatus to a source of warmed pressurized air for comfort warming, and convectively warming the person for comfort by way of the first section. To prepare for surgery, the first section is decoupled from the comfort warming source and the clinical garment is arranged to afford access to a surgical site. In preparation for surgery, the clinical garment may be left on the person, with its skirts rolled up to provide surgical access. Alternatively, the clinical garment may be removed to allow the convective apparatus to be positioned on the person to provide surgical access. In this latter case, the skirts, sleeves and other loose parts of the clinical garment may be rolled or folded onto the convective apparatus. In yet another alternative, if the convective apparatus is releasably attached to the inside surface of the clinical garment, the garment may be separated from the convective apparatus during surgery and reattached later postoperatively. During surgery, the convective apparatus may be secured to the person by means of the double sided adhesive and a second section of the convective apparatus may be coupled to a source of warmed pressurized air for therapeutic warming, and the person may be convectively warmed for therapy by way of the second section. Following surgery, the convective apparatus is detached from the person (but only if secured to the person for surgery), the convective device is reattached to the clinical garment (but only if detached therefrom for surgery), the person is again dressed with the clinical garment and either warmed for comfort or warmed for therapy. 
     Manifestly, the descriptions and illustrations in this specification are presented for an understanding of how to make and use an exemplary perioperative warming device. The only limitations on the scope of protection afforded the inventive principles presented are in the following claims.