Abstract:
A tourniquet cuff includes a first sheet, a second sheet, and a seal joining the first sheet and second sheet to form an inflatable bladder. A securing strap is attached to the cuff. The cuff encircles the limb so that the bladder overlaps upon itself. A stiffener fits inside the bladder and sized to extend substantially the length of the bladder but not the entire bladder length, and to fit completely within the seal. A tubular port is connected to the bladder for directing gas into the bladder from a tourniquet instrument to which the port may be releasably connected, and a cuff marking weld is located on an outer surface of the cuff, having a shape selected to form a symbol or indicia that is visible to a user.

Description:
This is a continuation of U.S. patent application Ser. No. 13/424,067, now U.S. Pat. No. 8,425,551 filed Apr. 23, 2013, which is a continuation of U.S. patent application Ser. No. 12/497,515, filed Jul. 2, 2009, now U.S. Pat. No. 8,142,472, which is a continuation of U.S. patent application Ser. No. 11/346,846, filed Feb. 3, 2006, now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 11/304,363, filed Dec. 14, 2005, now U.S. Pat. No. 8,137,378, all three of which applications are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention pertains to pneumatic tourniquet cuffs commonly used for stopping arterial blood flow into a portion of a surgical patient&#39;s limb to facilitate the performance of a surgical procedure, and for facilitating intravenous regional anesthesia. 
     BACKGROUND OF THE INVENTION 
     Typical surgical tourniquet systems of the prior art include a tourniquet cuff which encircles the limb of a surgical patient and a tourniquet instrument which is releasably connected to an inflatable bladder within the tourniquet cuff through a length of tubing, thereby establishing a gas-tight passageway between the cuff and the tourniquet instrument. The tourniquet instrument contains a pressurized gas source which is used to inflate and regulate the pressure in the tourniquet cuff above a minimum pressure required to stop arterial blood flow distal to the cuff, for a duration suitably long for the performance of a surgical procedure. Many types of surgical tourniquet systems have been described in the prior art, such as those described by McEwen in U.S. Pat. No. 4,469,099, No. 4,479,494, No. 5,439,477 and McEwen and Jameson in U.S. Pat. No. 5,556,415 and No. 5,855,589. 
     A number of different types of disposable tourniquet cuffs are known in the prior art. These cuffs are intended to be used within sterile surgical fields, and are typically sterilized at the time of manufacture. Examples of multi-layer disposable cuffs in the prior art are described by Robinette-Lehman in U.S. Pat. No. 4,635,635, and in commercial products manufactured in accordance with its teachings (“Banana Cuff” sterile disposable tourniquet cuffs, Zimmer Arthroscopy Systems, Englewood Colo.), and by Guzman et al. in U.S. Pat. No. 6,506,206, and in commercial products manufactured according to its teachings (“Comfortor™ Disposable Gel Cuff”, DePuy Orthopaedics Inc., Warsaw Ind.). A two-layer disposable cuff of the prior art is described by Spence in U.S. Pat. No. 5,733,304. Other disposable cuffs of the prior art have been constructed using multiple layers of costly materials such as cloth/thermoplastic laminates and gels. The use of multiple layers of such materials in prior-art cuffs has increased their overall thickness and stiffness, making these cuffs difficult for a surgical user to apply consistently. Thicker and stiffer cuffs of the prior art may also degrade performance after cuff application so that higher tourniquet pressures may be required to reliably occlude blood flow; this is undesirable because higher tourniquet pressures are associated in the surgical literature with a higher risk of patient injury. 
     Typical tourniquet cuffs of the prior art include a sealed inflatable bladder that encircles the limb and communicates pneumatically with a connected tourniquet instrument through one or more cuff ports, a stiffener that helps direct the expansion of the bladder radially inwards towards the limb and helps prevent any twisting or rolling of the cuff on the limb, and one or more fasteners that secure the cuff around the limb. 
     In order to facilitate the attachment of fasteners and cuff ports, the manufacture of prior art cuffs having multiple layers typically includes several labor-intensive operations, some of which require a high level of skill, quality and consistency on the part of manufacturing personnel. These operations can include sewing fastener materials to an outer cuff layer, adding a structural reinforcing patch to the outer layer, sealing one or more ports to a layer forming part of the inflatable bladder, and sealing layers around a perimeter to form the bladder. 
     Cuff layers consisting of compatible thermoplastic polymeric materials are typically joined together using a radio frequency (RF) welding process, which uses a combination of heat and pressure to cause compatible polymers to flow together by molecular diffusion. Welding operations to make cuffs of the prior art are typically completed in multiple steps, each of which typically requires the involvement of manufacturing personnel. For example, some cuffs have inflatable bladders formed from two separate sheets of thermoplastic coated material that are sealed around a perimeter using an RF welding process. Gas passageways into the bladder are typically formed using single or multiple ports welded to one layer before the bladder is formed. Each port provides a gas passageway into the bladder through a reinforced structure that is attached to tubing extending outside the sterile surgical field for connection to a tourniquet instrument. During the manufacturing process, the port is typically attached to one side of the bladder in a welding operation before the bladder is formed, to prevent the opposite bladder surface from being welded at the port location. 
     Many tourniquet cuffs of the prior art include a thermoplastic stiffener, which helps direct the expansion of the cuff bladder radially inward toward the limb when pressurized and helps reduce any tendency of the cuff to twist when pressurized or to roll distally down a tapered limb. The absence of a stiffener can lead to a reduction of the efficient application of pressure to the limb and thus can lead to an increase in the level of pressure required to stop blood flow past the cuff and into the limb. Also, the absence of a stiffener can lead to additional stresses in the outer cuff surface due to less constrained bladder expansion. 
     In many commonly used types of tourniquet cuffs of the prior art (such as Zimmer ATS sterile disposable tourniquet cuffs distributed by Zimmer Inc., Dover Ohio), a non-inflating sheath contains a stiffener outside an inflatable bladder. This configuration helps constrain the expansion of the bladder inwardly into the soft tissues of the limb encircled by the cuff when the cuff is pressurized, and helps prevent any twisting or rolling of the cuff on the limb. A second type of stiffener configuration involves increasing the thickness and rigidity of the material forming the outer cuff layer, to obtain a stiffening function from the outer layer in a two-layer cuff design (for example, as described by Eaton in U.S. Pat. No. 5,413,582, and in tourniquet cuffs distributed by Oak Medical, Briggs, North Lincs, UK). The outer layer of these prior-art tourniquet cuffs serves both as a stiffener and as one side of the inflatable bladder. The thick outer layer extends to all of the cuff edges, and includes an area for sealing the inner layer to the thick outer layer to form an inflatable bladder, resulting in the bladder always having a bladder width that is less than the width of the stiffener; this is undesirable because cuffs having narrower bladder widths require higher tourniquet pressures to stop blood flow, and higher tourniquet cuff pressures are associated with a higher risk of patient injury. Also, this second type of stiffener configuration in cuffs of the prior art, in which the stiffener forms part of the inflatable bladder, greatly limits the extent to which the cuff can expand inwardly into soft tissue when the cuff is pressurized; this limitation increases the pressure required to stop or occlude blood flow in the encircled limb, especially in obese patients and patients having large amounts of soft tissue. Further, the thick and stiff edges formed at the side edges of these prior-art cuffs may have a tendency to buckle towards the limb when the bladder is pressurized, leading to a potential soft-tissue hazard. A third stiffener configuration in tourniquet cuffs of the prior art includes an unsecured stiffener located within the inflatable bladder (for example, as described by Goldstein et al. in U.S. Pat. No. 5,411,518, by Spence in U.S. Pat. No. 5,733,304, and as seen in “Color Cuff II” sterile disposable tourniquet cuffs distributed by InstruMed Inc., Bothell Wash.). In this configuration, the stiffener is unsecured within the bladder and does not constrain the expansion of the outer cuff surface. This reduces the effectiveness of the stiffener in directing cuff pressure toward the encircled limb across the width of the cuff, and it reduces the extent to which the cuff can expand inwardly when pressurized, thereby making its performance more sensitive to variations in application technique and thereby leading to the possible need for higher tourniquet pressures to stop blood flow past the cuff and into the limb, particularly in patients having large amounts of soft tissue and in patients with poor muscle tone. Further, an unsecured stiffener within the cuff bladder is not as effective as a secured stiffener in helping to prevent the cuff from twisting or rolling on the limb. In addition, to reduce the limitations of performance that are inherent in a cuff having an unsecured stiffener within the inflatable bladder, the width of the stiffener in prior art cuffs must be as close as possible to the bladder width; this can impair cuff performance and requires precise alignment of the stiffener during manufacture. 
     Many cuffs of the prior art include velcro-type fastening elements, commonly referred to as hook and loop fasteners. The most common configuration consists of a hook-type fastening strap adapted for engaging with a loop-type material on the outer surface of the cuff to form a releasable velcro-type attachment when the cuff encircles a limb. In U.S. Pat. No. 5,201,758 Glover describes a multi-layer tourniquet cuff having a bladder contained within a flexible covering and a backing plate, and a fabric strap of loop-type material attached at one end to the outer side of the backing plate, for releasably engaging with a strip of hook-type material permanently mounted to the outer side of the backing plate. In U.S. Pat. No. 5,411,518 Goldstein et al. describe a two-layer tourniquet cuff having a hook or loop fastening strap for engaging with an outer cuff surface of loop or hook material. In U.S. Pat. No. 5,413,582 Eaton describes a tourniquet cuff having two sheets joined at the sides and ends to form an inflatable bladder, wherein a fabric strap of hook-type material is attached to the outer sheet of the cuff by welding or by an adhesive, and wherein one end of a loop-type fabric tongue is attached to the outer cuff sheet by welding or by an adhesive. Eaton &#39;582 further describes a flange that passes through an opening in the fabric tongue to help reduce the potential for a user accidentally pulling the fabric tongue off the outer sheet while tightening the cuff about a patient&#39;s limb. In U.S. Pat. No. 5,733,304 Spence describes a tourniquet cuff having a bladder with inner and outer walls and a fastening strap with anchored and free portions, wherein the anchored portion is attached to the outer wall of the bladder with a velcro-type connection and wherein the free portion is adapted to be releasably anchored by a user to the outer wall with a velcro-type connection. Spence &#39;304 includes a hole in the fastening strap to allow the cuff port to help permanently secure the fastening strap, as described previously in Eaton &#39;582. 
     Some tourniquet cuffs of the prior art include secondary fastening elements to provide increased safety and to facilitate cuff application. In U.S. Pat. No. 5,312,431 McEwen describes a tourniquet cuff having a primary fastening means to secure the bladder and a secondary fastening means which is independent of the primary fastening means. McEwen &#39;431 provides increased safety by ensuring the bladder remains overlapped and secured in a substantially circumferential direction by the secondary velcro-type fastening means even if the primary fastening means is not engaged or becomes ineffective while the cuff is inflated. The primary fastening means of McEwen &#39;431 further facilitates cuff application and alignment of a cuff end by providing a velcro-type patch near the cuff end for releasable attachment of the end to a surface of the cuff. In U.S. Pat. No. 5,193,549 Bellin et al. describe a tourniquet cuff with a hook-type patch attached to a loop-type cuff surface near an end by welding, adhesive or sewing, wherein the patch facilitates releasable attachment of the cuff end to the surface to secure the cuff around a limb. The two-layer tourniquet cuff described in Spence &#39;304 includes primary and secondary fastening means similar to McEwen &#39;431, wherein a velcro-type fastening patch facilitates releasable attachment of a cuff end to a mating velcro-type cuff surface as in Bellin &#39;549 so that the overlapping bladder is secured in a substantially circumferential direction around the limb, and wherein a velcro-type fastening strap engages with a mating velcro-type surface of the cuff to secure the cuff around the limb. 
     To help secure the end of the cuff in contact with the limb and to aid in cuff alignment during application, a number of cuffs in the prior art include a tie strap attached near one end of the cuff. Typical cuffs which include a tie strap are described by McEwen et al. in U.S. Pat. No. 6,682,547 and by Robinette-Lehman in U.S. Pat. No. 4,635,635. A tie strap allows a surgical user to achieve a snug application of the cuff to the limb, and when tied helps assure that the overlapping portion of the cuff remains aligned, thus helping to prevent twisting, telescoping and rolling of the cuff when inflated, and thus helping to assure the most effective transmission of pressure from the cuff to the limb. Prior-art tourniquet cuffs include tie straps that are attached to cuffs in a variety of ways, including sewing or bonding to a surface of the cuff. It is not desirable to attach the tie strap to the cuff surface facing the patient&#39;s limb, where such attachment may distort the cuff surface and thus lead to uneven pressure distribution and possible soft-tissue injury. An alternate method of attaching the tie strap to the end of a cuff is shown in Goldstein et al. &#39;518. Some prior art cuffs such as Spence &#39;304 do not include a tie strap, but such cuffs are less conveniently applied, and may result in an applied cuff that is less snug and less effective in transmitting pressure from the cuff to the limb. 
     Some prior art cuffs carry marking visible to a surgical user, as described for example by McEwen in U.S. Pat. No. 4,605,010 and U.S. Pat. No. 5,312,431. Typical markings carried on tourniquet cuffs of the prior art have included labels sewn to cuff components and ink lettering and symbols marked on cuff surfaces. Some tourniquet cuffs of the prior art are marked by manufacturers to indicate that they are intended for single use only. Unauthorized reprocessing and reuse of such tourniquet cuffs in multiple surgical procedures may be hazardous for patients. However, such marking on prior-art cuffs may be easily removed or obscured if the cuffs are reprocessed, leading to the possibility that surgical staff may unknowingly use disposable tourniquet cuffs that have been reprocessed in a manner not authorized by the manufacturer and hazardous to patients. 
     In general, it is desirable to construct the thinnest tourniquet cuff possible for a given application. Thinner cuffs have smaller differences in circumference between inner cuff surfaces and outer cuff surfaces when encircling a patient&#39;s limb, in comparison to thicker cuffs. Such smaller differences in circumference reduce folding and wrinkling at the inner cuff surface. This reduces the possibility of wrinkling, pinching, bruising and other injuries to the skin and soft tissue encircled by such cuffs. Further, thinner cuffs tend to be less rigid than thicker cuffs and thus allow a surgical user to apply the cuff more snugly and more easily to the limb. 
     The manufacturing and assembly process of prior art cuffs consists of numerous cutting, sewing, and sealing operations which require substantial investment in both equipment and skilled operators. The manual labor component of cuff assembly is high, especially where multiple sewing and sealing operations are required. It is therefore desirable to reduce the skill and time required by the cuff assembly process, while continuing to utilize readily available manufacturing equipment. A reduction in the amount of time and skill required to manufacture tourniquet cuffs can be accomplished by reducing the number of manual assembly operations. This may include the elimination of numerous sewing operations, and the consolidation of multiple RF sealing steps into a single operation. Reducing the number of manual operations provides a savings not only in the labor to construct a cuff, but also provides the potential for the automation of a number of steps leading to the single cuff sealing operation. 
     In U.S. Pat. No. 6,682,547 McEwen et al. describe a method for automating the cuff manufacturing process by constructing the top layer of the cuff in a continuous strip having varying thickness to provide the stiffening functions described previously while not limiting the inward radial expansion of the bladder. McEwen &#39;547 describes a custom manufacturing process which allows the bottom and top layers to be joined in a continuous process, whereby the edge of the inner layer is folded over the outer layer and sealed. The end edges of the cuff are sealed at various intervals to allow the construction of cuffs of a variety of lengths. The stiffened top layer therefore extends to the ends of the resulting cuff. Manufacturing the tourniquet cuff described in McEwen &#39;547 requires a high level of investment in automated manufacturing equipment and processes, and necessarily requires a high volume of cuff manufacture to produce low-cost cuffs. 
     There is a need for a disposable tourniquet cuff which overcomes the hazards, problems and limitations of performance associated with prior-art cuffs as described above, and which can be manufactured at substantially lower cost with few changes to existing manufacturing equipment and processes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial representation of the preferred embodiment in a surgical application. 
         FIG. 2  is an exploded view of the preferred embodiment. 
         FIGS. 3 a  and 3 b    are top views of the preferred embodiment. 
         FIGS. 4 a , 4 b  and 4 c    are section views taken from  FIG. 3   a.    
         FIG. 5  is a section view taken from  FIG. 3   b.    
         FIG. 6  is a top view of the preferred embodiment showing a securing strip. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a pictorial representation of the preferred embodiment in a surgical application, showing tourniquet cuff  10  secured circumferentially around patient limb  12  proximal to surgical site  14 . Tie strap  16  described further below, is tied as shown in  FIG. 1  to help prevent the cuff  10  from sliding proximally or distally on patient limb  12  when cuff  10  is inflated. 
     The inflatable portion of tourniquet cuff  10  completely encircles patient limb  12  and is pneumatically connected to tourniquet instrument  18  via cuff port  20 , cuff tubing  22 , cuff connector  24 , instrument connector  26  and instrument tubing  28 . Tourniquet instrument  18  supplies pressurized gas for the inflation of cuff  10  and is capable of inflating cuff  10  to a pressure that will occlude the flow of arterial blood in patient limb  12  distal to cuff  10 . 
     The perimeter of a sterile surgical field  30  encloses surgical site  14 , a portion of patient limb  12 , tourniquet cuff  10 , and a portion of cuff tubing  22 . Cuff tubing  22  is of sufficient length to permit cuff connector  24  to be releasably mated with instrument connector  26  outside of sterile surgical field  30 . In the preferred embodiment shown, cuff  10  is a single port cuff, where cuff port  20  provides a single pneumatic passageway into the inflatable portion of cuff  10 . Those skilled in the art will appreciate that the features described in the preferred embodiment may also be applied to tourniquet cuffs having more than one port, such as those described by U.S. Pat. No. 4,469,099, No. 4,479,494, and No. 5,254,087. 
     As described below, cuff  10  is constructed of materials that are appropriate for a single-use sterile disposable tourniquet cuff. To permit cuff  10  to be used in a sterile surgical field, cuff  10  is sterilized at time of manufacture by exposure to a sterilizing agent within a sterilizing process determined to be safe and effective. To prevent deterioration of the cuff, and to maintain the integrity of the pneumatic passageways within cuff  10 , a sterilization agent and process that will not harm the materials or components of cuff  10  is selected by the manufacturer. In the preferred embodiment cuff  10  is sterilized by exposure to gamma radiation or electron beam radiation. 
     The cost of materials and labor are important considerations in the manufacture of tourniquet cuffs intended for a single use and then disposal. To minimize the cost of materials and assembly of cuff  10 , materials are selected which are not intended to withstand exposure to subsequent sterilization and cleaning processes. The subsequent sterilization or cleaning of cuff  10  by agents and processes commonly used in health care facilities, such as ethylene oxide gas sterilization, hydrogen peroxide gas sterilization, high temperature and pressure steam sterilization, sterilization by other chemical agents, and pasteurization, are all capable of adversely affecting the integrity of the materials and pneumatic passageways of cuff  10 . 
     Cuff  10  includes marking such as symbols or letters to indicate to that cuff  10  is intended for a single patient use and is to be discarded after use. Marking may also be present to identify the manufacturer of cuff  10  and indicate a manufacturing lot number. 
     The preferred embodiment includes marking to indicate that the cuff is intended for a single use and the marking is permanently formed in selected welded areas of cuff  10  as described further below. This permanent marking can be easily read by a user and cannot be easily obscured or removed from the cuff without causing damage to the cuff. Typical prior art cuffs include marking printed with ink onto labels which are then sewn onto the cuff or printed with ink directly onto the cuff, and marking printed onto the sterile packaging in which the cuff is provided to the user. Additionally, marking within bonded areas of a cuff is described by McEwen et al. in U.S. Pat. No. 6,682,547. 
     Printed cuff packaging can be easily lost or thrown away and sewn on labels can be inadvertently or intentionally removed from these prior art cuffs. Marking printed with ink directly on the cuff may be obscured, and ink fragments may come loose and contaminate the surgical field. If a cuff is not clearly marked as intended for single use a user or third party could unknowingly attempt to re-manufacture and re-sterilize the cuff contrary to the original manufacturer&#39;s instructions thereby producing a cuff that is possibly hazardous to patients. 
       FIG. 2  is an exploded view of the individual components that are joined together as described below to form cuff  10 . For clarity, cuff tubing  22  and cuff connector  24  are not shown in  FIG. 2 . 
     Those skilled in the art will appreciate that many conventional methods exist for joining the thermoplastic polymers that comprise the materials of cuff  10 . Joining processes can be separated into two broad groups: adhesive bonding, and thermal or solvent welding. In an adhesive bonding process, an adhesive layer is applied between two or more materials and when cured, the adhesive holds the materials together at their surfaces. In a thermal or solvent welding process, the surfaces of two or more materials are made fluid by applying either thermal heating or a solvent, which allow the thermoplastic materials to molecularly diffuse into one another forming a weld. For molecular diffusion to occur the thermoplastic polymers being thermally or solvent welded must be sufficiently compatible. Thermal or solvent welding will not occur between incompatible materials, for example, polyurethane and polyethylene. Thermal welding can be accomplished by numerous methods, including direct heating (e.g., hot gas, infrared, extrusion), induced heating (e.g., radio frequency (RF) or dielectric welding), and frictional heating (e.g., ultrasonic welding). In the preferred embodiment and as described below, the thermoplastic polymers comprising components of cuff  10  are joined together by the dielectric welding process, in which materials are brought together under pressure in a die and radio frequency energy is applied to temporarily melt a portion of the thermoplastic materials causing them to weld together in a selected area. Dielectric welding relies on the principle of dielectric heating to induce heat in thermoplastic materials placed within an alternating electromagnetic field. The amount of potential heating generated is dependent upon the dielectric properties of the thermoplastic materials, known as loss factor or dissipation factor. Thermoplastics with a relatively high dissipation factor such as polyurethane can be readily dielectrically welded, while thermoplastics with low dissipation factors such as polyethylene can not be readily welded by this process. While thermoplastic polyethylene will not heat substantially during the dielectric welding process it will still provide a conductive path through which the alternating electromagnetic field will propagate allowing welding to occur in adjacent materials. 
     Some materials that comprise components of cuff  10  are attached by stitches formed from nylon thread. It will be apparent that other types of mechanical fastening methods such as stapling and riveting could be used to attach selected components of cuff  10 . Unlike joints formed by adhesive bonds and welds described above that can form gas-tight seals, materials that are sewn together or otherwise mechanically fastened generally do not form gas-tight seals between components. 
     To reduce manufacturing equipment and labor costs it is desirable to manufacture cuff  10  in a single dielectric welding operation. This requires that the thermoplastic polymers comprising the components of cuff  10  be prevented from welding at selected surfaces. Preventing thermoplastic materials from welding together can be accomplished by several methods. One method involves coating the surface of a thermoplastic material with a material that prevents the molecular diffusion into another otherwise compatible material. Another method involves selecting thermoplastic materials that have markedly different dissipation factors, preventing one or more of the materials from heating during a dielectric welding operation. As described above, both methods may be employed in the manufacture of cuff  10 . 
     Referring to the components of cuff  10  shown in  FIG. 2 , securing strap  32  is made of a nylon hook material that is commonly used in hook and loop velcro-type fastening applications. Velcro-type fasteners form releasable connections between two mating surfaces. When the velcro-type surfaces are engaged they resist shear and tensile forces. The surfaces are typically released by peeling the surfaces apart from an edge. In use, securing strap  32  engages with loop material on the outer surface of top sheet  34 . When cuff  10  is applied to a limb, securing strap  32  is engaged by a user to the loop material of top sheet  34  to secure cuff  10  circumferentially around the limb. The length and specifications of the hook material comprising securing strap  32  are selected to maintain cuff  10  securely around the limb circumference when cuff  10  is inflated. 
     Top sheet  34  is a thin flexible nylon loop material adapted for secure engagement with the hook material of securing strap  32 . Top sheet  34  is coated on the inner surface with a thermoplastic polymer. This thermoplastic polymer coating prevents the passage of gas through top sheet  34  and allows top sheet  34  to be joined to cuff port  20 , bottom sheet  36  and to stiffener  38  as described below. In the preferred embodiment the thermoplastic coating on top sheet  34  is polyurethane. It will be apparent that securing strap  32  could be comprised of a loop material and top sheet  34  could be a hook material. It will also be appreciated that other velcro-type materials, including adhesives that have velcro-type properties, could be selected to comprise securing strap  32  and top sheet  34 . 
     Bottom sheet  36  is made of flexible woven cloth coated on the inner surface with a thermoplastic polymer. The thermoplastic polymer coating prevents the passage of gas through bottom sheet  36  and allows bottom sheet  36  to be joined to top sheet  34  as described above and below. In the preferred embodiment the thermoplastic coating on bottom sheet  36  is polyurethane. It will be appreciated by those skilled in the art that other thermoplastic polymers, polyvinylchloride for example, may be used as coatings on top sheet  34  and bottom sheet  36  providing they can be joined with sufficient strength to maintain the integrity of cuff  10  when inflated. 
     As shown in  FIG. 2 , cuff port  20  has a right angle configuration and includes a flange. Cuff port  20  is made of a thermoplastic polymer that is compatible with and can be joined to the thermoplastic coating of top sheet  34  to form a gas-tight seal. 
     Tie strap  16  is a soft fabric ribbon material that is shown in  FIG. 2  positioned between bottom sheet  36  and top sheet  34 . As described below, tie strap  16  is secured to the inner coated surface of bottom sheet  36 . This configuration positions the tie strap  16  away from the surface of the patient limb and promotes even pressure distribution from the overlapping bladder. Tie strap  16  may also be secured to the inner surface of top sheet  34 . Tie strap  16  provides a means for the user to align and pull cuff  10  snug around the limb when tied as shown in  FIG. 1 , helps maintain the overlapping portion of the cuff in alignment around the limb by preventing the inflated cuff from twisting, telescoping and rolling on the limb when inflated. Tie strap  16  may be coated with a thermoplastic polymer that is compatible with the polymer coating on bottom sheet  36  to permit it to be welded to bottom sheet  36  or may be comprised of materials that adhere to the coated surfaces of bottom sheet  36  and top sheet  34 . 
     Secondary fastener  40  is hook material similar to the hook material that comprises securing strap  32 . Secondary fastener  40  is attached to the outer surface of bottom sheet  36  and engages with the loop material of top sheet  34 . Secondary fastener  40  facilitates cuff application and alignment of the cuff by providing a means for maintaining cuff  10  in position around patient limb  12  while securing strap  32  is engaged. Secondary fastener  40  acts independently of securing strap  32  providing increased safety by helping to ensure the cuff remains overlapped and secured in a substantially circumferential direction if securing strap  32  is not engaged or becomes ineffective while the cuff is inflated. 
     Stiffener  38  is made of a gas impermeable thermoplastic polymer sheet cut to a rectangular shape to fit within the perimeter of bladder perimeter weld  42  shown in  FIGS. 3 a , 3 b    and  6 . The length dimension of stiffener  38  is at least equal to the circumference of patient limb  12  at the location that cuff  10  is applied to patient limb  12 . Top sheet  34  and bottom sheet  36  are welded together at bladder perimeter weld  42  to form an inflatable bladder  44  shown in  FIGS. 4 a , 4 b , 4 c   , and  5 . The length dimension of inflatable bladder  44  is greater than the circumference of patient limb  12  at the location that cuff  10  is applied to patient limb  12 . 
     Stiffener  38  is less flexible than top sheet  34  and bottom sheet  36  but is flexible enough to be wrapped around a limb (for example, 0.020″ thick polyurethane/polyvinylchloride alloy sheet or polyethylene sheet). The properties of stiffener  38  are selected such that the forces required to bend stiffener  38  across its width are significantly greater than those required to bend top sheet  34  across its width by an equal amount. When secured circumferentially around the limb as shown in  FIG. 1 , stiffener  38  helps direct the expansion of inflatable bladder  44  radially inwards towards the limb upon inflation of cuff  10 . The stiffener thus provides uniformly distributed pressure onto limb. Attaching stiffener  38  to top sheet  34  prevents top sheet  34  from moving relative to stiffener  38  and thereby helps prevent cuff  10  from rolling down patient limb  12  when cuff  10  is inflated. The attachment of stiffener  38  to top sheet  34  permits the use of thin flexible materials for top sheet  34  and bottom sheet  36  making for a thinner overall cuff which is desirable as thin cuffs afford an improved fit to the patient limb with less wrinkling of materials. Some prior art cuffs with a stiffener floating within the bladder use heavier stiffer materials for the bladder walls to resist rolling along the limb. These thick materials result in increased wrinkling of the bladder surfaces when the cuff is applied to the limb. 
     The width of stiffener  38  is less than the width of inflatable bladder  44  when cuff  10  is laid flat. The width of stiffener  38  determines the degree to which bladder  44  can expand (or reach) to apply pressure into the limb. Unlike prior art cuffs that have a stiffener extending beyond the width of the inflatable bladder, cuff  10  has greater reach and thereby results in lower limb occlusion pressures than those obtainable with prior art cuffs. In the preferred embodiment a surface of the thermoplastic polymer that comprises stiffener  38  is compatible with the thermoplastic coating of top sheet  34  and is welded to the inner surface of top sheet  34  by the dielectric welding process described above. Stiffener  38  is prevented from welding to the inner surface of bottom sheet  36  by an incompatible coating which is applied as described below to either a surface of stiffener  38  or to a portion of the inner surface of bottom sheet  36 . 
     Welds that attach the inner surface of top sheet  34  to stiffener  38  form gas-tight seals at their perimeters and define a non-inflatable portion or portions of top sheet  34 . In prior art cuffs with floating or unattached stiffeners within the bladder the outer surface of the bladder is free to expand outward away from the limb when the cuff is inflated. This expansion or “ballooning” of the outer surface of the bladder is undesirable, especially in areas where velcro-type fasteners are mated to the outer surface to secure the cuff around the limb. In the preferred embodiment non-inflatable portions of top sheet  34  and stiffener  38  remain in substantially the same plane and do not balloon outward when the cuff is inflated thus providing a more secure attachment area for velcro-type fasteners. 
       FIGS. 3 a  and 3 b    are top views of the preferred embodiment laid flat showing the areas where the inner surface of top sheet  34  are welded to bottom sheet  36 , cuff port  20  and stiffener  38 . The separate weld areas shown in  FIGS. 3 a  and 3 b    are: bladder perimeter weld  42 , cuff port weld  46 , tie strap retaining weld  48 , and stiffener retaining weld  52 . The dies used to form these welds may be adapted to produce marking in bladder perimeter weld  42  and stiffener retaining weld  52 . The marking that is formed is integral to the welded areas and easily visible to a user as described above to indicate to a user that cuff  10  is intended for a single use only. Bladder perimeter weld  42  defines inflatable bladder  44  of cuff  10  which is shown in  FIGS. 4 a , 4 b , 4 c   , and  5 . Cuff port  20 , cuff tubing  22  and cuff connector  24  provide a pneumatic passageway communicating with inflatable bladder  44  through which bladder  44  may be inflated. 
     The perimeters of stiffener retaining weld  52  and cuff port weld  46  define a non-inflatable portion of top sheet  34 . This non-inflatable portion of top sheet  34  does not form part of inflatable bladder  44  and pressurized gas does not contact this portion of top sheet  34 . 
       FIG. 3 a    shows non-inflating region weld  50 , the perimeter of which defines a non-inflating region near the end edge of cuff  10 . In  FIG. 3 a   , securing strap  32  is shown sewn at location  54  to the upper surface of cuff  10  (outer surface of top sheet  34 ) within the perimeter of non-inflating region weld  50 , in the preferred embodiment secondary fastener  40  is also sewn to the bottom surface of cuff  10  (outer surface of bottom sheet  36 ) at location  54  opposite the attachment point of securing strap  32 . It will be apparent that securing strap  32  and secondary fastener  40  may be attached by other mechanical fastening means or by welding or adhesives. It will also be apparent that a surface of securing strap  32  may be coated with a thermoplastic polymer and joined by welding in between top sheet  34  and bottom sheet  36 . 
     In  FIG. 3 b    bladder perimeter weld  42  is shown extended to near the end edge of cuff  10  eliminating non-inflating region weld  50 . It will be apparent that the width of the bladder perimeter weld  42  may be increased near the end edge of the cuff to join top sheet  34  to bottom sheet  36  out to the end edge of cuff  10 . 
     In  FIG. 3 b    securing strap  32  is shown non-releasably attached to the non-inflatable portion of top sheet  34  within the perimeter of stiffener retaining weld  52  at location  56 . Securing strap  32  may be sewn or attached by other mechanical fastening means to top sheet  34  as the attachment is not required to be gas-tight as it is made within the non-inflatable portion of top sheet  34 . Securing strap  32  may also be welded or adhesively bonded at location  56  to non-releasably attach securing strap  32  to top sheet  34 . 
     The length of securing strap  32  may also be increased to permit a greater area of engagement of the hook and loop materials of securing strap  32  and top sheet  34  within the non-inflatable portion of top sheet  34 . If the area of hook and loop engagement is sufficiently large to maintain cuff  10  secured around a limb when inflated, the attachment at location  56  may be eliminated. 
     When cuff  10  is secured around a limb and inflated, securing strap  32  comes under considerable tension. The amount of tension securing strap  32  and its attachment location is subject to and dependent upon the circumference of the limb and the pressure to which bladder  44  is inflated. In the configuration of cuff  10  shown in  FIG. 3 b    securing strap  32  includes a hole formed to allow cuff port  20  to pass through securing strap  32 . When securing strap  32  comes under tension securing strap  32  may stretch and move slightly. In the preferred embodiment the hole formed in securing strap  32  is sized, shaped, and positioned to prevent securing strap  32  from transferring load to the sides of cuff port  20  when securing strap  32  is tensioned. 
     As shown in  FIG. 3 b    and shown in cross section in  FIG. 5  securing strap  32  is also non-releasably attached to cuff  10  by retaining ring  58 . Retaining ring  58  is formed from rigid thermoplastic and non-releasably engages within a grove formed in cuff port  20 . Retaining ring  58  has an outer diameter that is greater than the diameter of the hole that is formed in securing strap  32  for cuff port  20  to pass through. Retaining ring  58  acts to prevent detachment of securing strap  32  by a surgical user from top sheet  34  near the location of cuff port  20 . 
     The attachment of securing strap  32  within the non-inflatable portion of top sheet  34  allows loads to be transferred from securing strap  32  to stiffener  38  by stiffener retaining weld  52 . Top sheet  34  may be joined to stiffener  38  in additional locations to aid in the transfer of loads from securing strap  32  to stiffener  38 . 
     When cuff  10  is configured as shown in  FIG. 3 b   , secondary fastener  40  may be attached to the outer surface of bottom sheet  36  by welding or by an adhesive. 
     Tie strap  16  is permanently attached to cuff  10  by tie strap retaining weld  48  shown in  FIGS. 3 a , 3 b   , and  6 . Top sheet  34 , tie strap  16 , and bottom sheet  36  are joined together at tie strap retaining weld  48 . 
     Cross section  4  from  FIG. 3 a    of cuff  10  is shown in  FIGS. 4 a , 4 b  and 4 c   .  FIGS. 4 a , 4 b  and 4 c    depict the regions where surfaces of the components of cuff  10  are joined together by welds and show alternate methods for preventing selected surfaces of the components of cuff  10  from forming welds during the welding process. 
     Referring to  FIG. 4 a   , top sheet  34  is joined to bottom sheet  36  at bladder perimeter weld  42  forming inflatable bladder  44 . In the preferred embodiment bladder perimeter weld  42  does not extend to the longitudinal side edges of top sheet  34  and bottom sheet  36  thereby leaving a non-welded edge  60  along the length of cuff  10 . This non-welded edge provides a softer more compliant edge for patient comfort than can be obtained when the width of the bladder perimeter weld  42  extends completely to the side edges of top sheet  34  and bottom sheet  36 . 
     Cuff port  20  is joined to the inner surface of top sheet  34  and outer surface of stiffener  38  at the location of cuff port weld  46 . 
     As shown in  FIGS. 3 a  and 3 b   , stiffener retaining weld  52  is formed around the perimeter of stiffener  38  and acts to non-releasably attach the outer surface of stiffener  38  to the inner surface of top sheet  34 , thereby preventing stiffener  38  from moving relative to top sheet  34  when cuff  10  is inflated. As described above, the perimeter of stiffener retaining weld  52  defines a non-inflatable portion of top sheet  34 . Stiffener retaining weld  52  is shown in  FIGS. 3 a  and 3 b    as a contiguous weld defining a single non-inflatable portion of top sheet  34 , it will be apparent that top sheet  34  could be joined to stiffener  38  by multiple welds forming multiple non-inflatable portions of top sheet  34 . 
     As shown in  FIG. 4 a    the thermoplastic polymer of stiffener  38  is compatible with the thermoplastic coating on the inner surface of top sheet  34  and the two surfaces can be welded to each another. To permit cuff  10  to be manufactured in a single dielectric welding operation, a barrier  62  is applied to the inner surface of stiffener  38 . Barrier  62  is a coating of thermoplastic material (for example polyethylene) that is not compatible with the thermoplastic coating on the inner surface of bottom sheet  36  and acts to prevent stiffener  38  from welding to the thermoplastic coating on the inner surface of bottom sheet  36  at the location of stiffener retaining weld  52  and cuff port weld  46 . 
     The cross section of cuff  10  shown in  FIG. 4 b    illustrates an alternate location for barrier  62 . As shown in  FIG. 4 b    barrier  62  is applied to a region of the inner surface of bottom sheet  36  such that stiffener  38  is prevented from welding with the thermoplastic coating on the inner surface of bottom sheet  36  at the location of stiffener retaining weld  52  and cuff port weld  46 . 
     In  FIG. 4 c   , stiffener  38  is formed from a thermoplastic which will not weld with the thermoplastic coatings on top sheet  34  and bottom sheet  36 , such as polyethylene. To permit a stiffener made of an incompatible thermoplastic to be attached to the inner surface of top sheet  34 , a stiffener coating  64  of a compatible thermoplastic such as polyurethane is laminated to the outer surface of stiffener  38 . This laminated coating allows stiffener  38  to be non-releasably attached to the inner surface of top sheet  34 . It will also be appreciated that stiffener  38  may be non-releasably attached to the inner surface of top sheet  34  by an adhesive bond by selecting and applying an adhesive compatible with the thermoplastic surfaces of top sheet  34  and stiffener  38 . 
     To reduce material costs cuff  10  may be configured as shown in  FIG. 6 . In  FIG. 6  cuff  10  is shown with a securing strip  66  joined to the outer surface of top sheet  34 . Securing strip  66  is a strip of nylon loop material compatible with the hook material of securing strap  32 . Securing strip  66  is coated on one surface with thermoplastic polymer material. In  FIG. 6  top sheet  34  is configured as woven nylon fabric with a thermoplastic polymer coating on both the inner and outer surfaces. The thermoplastic polymer coating on the outer surface is typically thinner than the coating on the inner surface and provides a weldable surface for the attachment of securing strip  66 . As shown in  FIG. 6 , securing strip  66  is attached to top sheet  34  at securing strip perimeter weld  68 . Securing strip  66  is also attached to top sheet  34  by cuff marking weld  70 . The shape of cuff marking weld  70  is selected to form the standard symbol for single use only devices to indicate to a user that cuff  10  is intended for a single use only. Stiffener  38  may also be bonded to the inner surface of top sheet  34  at the locations of securing strip perimeter weld  68  and cuff marking weld  70  to form non-inflatable portions of top sheet  34 . 
     A portion of securing strap  32  is non-releasably attached to securing strip  66  at location  72 . Securing strap  32  may be attached to securing strip  66  by sewing or welding. The length of securing strap  32  may also be increased to permit a greater area of engagement of the hook and loop materials of securing strap  32  and securing strip  66 . If the area of hook and loop engagement is sufficiently large to maintain cuff  10  secured around a limb when inflated, the attachment at location  72  may be eliminated. 
     A hole formed in securing strap  32  as described above allows cuff port  20  to pass through securing strap  32 . As shown in  FIG. 6  securing strap  32  is also attached to cuff  10  at location  74  beyond the end edge of bladder perimeter weld  42 . In the preferred embodiment securing strap  32  is attached at location  74  by sewing through top sheet  34  and bottom sheet  36 . The attachment of securing strap  32  at location  74  allows loads from securing strap  32  to be distributed to bottom sheet  36  and evenly to both sides of cuff port  20 , it also prevents a user from applying loads to cuff port  20  when manipulating securing strap  32  during cuff application and removal. If securing strap  32  is not non-releasably attached at location  72 , the non-releasable attachment at location  74  acts to maintain securing strap  32  in the correct position and orientation on cuff  10  and prevents securing strap  32  from being inadvertently removed from cuff  10  by a user. Securing strap  32  may also be attached at location  74  by other mechanical fastening methods or by adhesives or welding. Top sheet  34  and bottom sheet  36  may be welded together at location  74  to provide a stronger area for the attachment of securing strap  32 . 
     The embodiment illustrated is not intended to be exhaustive or limit the invention to the precise form disclosed. It is chosen and described in order to explain the principles of the invention and its application and practical use, and thereby enable others skilled in the art to utilize the invention.