Abstract:
A low-cost contour cuff for surgical tourniquet systems comprises: a sheath containing an inflatable bladder, the sheath having an arcuate shape, an outer surface and a centerline equidistant between first and second side edges; a securing strap non-releasably attached to the outer surface and formed of substantially inextensible material having a shape that is predetermined and substantially flat, wherein the strap includes a bending portion near a first strap end and a fastening portion near a second strap end, and wherein the bending portion is adapted to allow twisting of the bending portion out of the substantially flat shape to facilitate positioning of the fastening portion into any of a plurality of positions in the substantially flat shape; and fastening means for releasably attaching the fastening portion of the securing strap to the outer surface whenever the sheath is curved into a position for surrounding a limb.

Description:
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. Nos. 4,469,099, 4,479,494, 5,439,477 and McEwen and Jameson in U.S. Pat. Nos. 5,556,415 and 5,855,589. 
   Standard cylindrical tourniquet cuffs are ideally suited for application to patients with cylindrical limbs. However, when applied to a patient with a tapered limb, a cylindrical cuff will not optimally match the limb taper, and will typically result in a snug fit proximally and a loose fit distally. Consequently, a cylindrical cuff may prove unable to achieve a bloodless field distal to the cuff at normal pressures or may require a substantially higher and more hazardous inflation pressure to achieve a bloodless field, and when inflated may have a tendency to roll or slide distally on the limb during a surgical procedure. In an effort to match the taper of a patient&#39;s limb at a desired cuff location, some tourniquet cuffs of the prior art are designed to have an arcuate shape, and are commonly called contour cuffs. When a contour cuff surrounds a limb having a matching taper, a uniformly snug fit can be achieved between the cuff and the limb from the proximal to distal cuff edges. Wide contour tourniquet cuffs of the prior art have been shown in the surgical literature to substantially reduce pressures required to create a bloodless surgical field distal to the inflated cuff (Younger et al., ‘Wide Contoured Thigh Cuffs and Automated Limb Occlusion Measurement Allow Lower Tourniquet Pressures’, Clin Orthop 428:286-293, 2004). Lower tourniquet pressures are associated in the surgical literature with lower risk of injuries to surgical patients. 
   Examples of contour cuffs of 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.). Cuffs described by Robinette-Lehman have an arcuate shape (defined by the distal radius), contain a single fastening system with fixed orientation, and include a rigid plastic stiffener. The cuff described in the &#39;635 patent matches only a single limb taper for each particular cuff radius. For a limb with a differing taper, a cuff with a different arcuate shape matching that taper must be selected. When the cuff described by Robinette-Lehman &#39;635 is applied to a limb with a differing taper, the overlapping proximal and distal edges of the cuff will not be superimposed upon one another, and will instead need to be skewed to obtain a sufficiently snug application and maximize the contact area between the cuff and the limb. The thick laminate construction and rigid stiffener included by Robinette-Lehman makes skewing the respective overlapping ends of the cuff difficult, and when skewed the orientation of the fixed fastening system may not be appropriate to safely and effectively allow the complete engagement of the velcro-type fastener to secure the cuff on the limb when inflated. 
   Other contour cuffs of the prior are described by McEwen in U.S. Pat. Nos. 5,312,431, 5,454,831, 5,578,055, 5,649,954, and 5,741,295. McEwegn &#39;431 describes a cuff with an arcuate shape which overcomes the limitations noted above, by replacing the rigid stiffener with fluted welds in the bladder, and by including a complex pivoting means for securing the cuff around a limb having any one of a wide range of limb tapers at the cuff location. Although the cuff described by McEwen &#39;431 provides increased safety and improved shape-matching over a wide range of limb tapers, it does so by including a number of expensive components and laminated materials, with subassemblies that are labor-intensive and time-consuming to manufacture. As a result, the contour cuff of McEwen &#39;431 has a high cost of manufacture, preventing its cost-effective use as sterile disposable tourniquet cuff for single surgical procedures. 
   The prior-art contour cuff described in McEwen &#39;431 employs multiple pivoting velcro-type hook fastening straps attached to D-shaped rings so that they may pivot when the cuff is wrapped around a tapered limb, and align with corresponding velcro-type loop material fastened to the surface of the cuff. These D-shaped ring assemblies are in turn attached near one end of the cuff. The ring assemblies allow the straps to pivot over a predetermined range when the cuff is wrapped around the limb to fully engage with the corresponding loop material on the outer surface of the cuff. Manufacturing the ring assemblies described in McEwen &#39;431 requires relatively large amounts of different materials, and requires numerous labor-intensive steps including cutting, alignment, sewing and welding, all of which must be completed by skilled operators. 
   There is a need for a contour cuff for surgical tourniquet systems that overcomes the hazards, problems and limitations of performance associated with prior-art contour cuffs, and that can be manufactured at a cost that is substantially lower than prior-art contour cuffs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a view of the preferred embodiment applied to a tapered patient limb. 
       FIG. 2  is a view of the preferred embodiment applied to a cylindrically shaped patient limb. 
       FIG. 3  is an exploded view of the preferred embodiment. 
       FIG. 4  is a top view of the preferred embodiment. 
       FIG. 5  is a section view taken from  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows the preferred embodiment in a surgical application and depicts contour tourniquet cuff  10  secured circumferentially around a tapered patient limb  12 .  FIG. 2  depicts contour cuff  10  secured circumferentially around a substantially cylindrically shaped patient limb  14 . 
   Referring to  FIG. 1 , the inflatable portion of contour tourniquet cuff  10  completely encircles patient limb  12  and is inflated by a source of pressurized gas to a pressure that will occlude the flow of arterial blood in patient limb  12  distal to cuff  10 . Cuff port  15  is comprised of port inlet  16  and tubing  18  and provides a gas tight pneumatic passageway to the inflatable portion of cuff  10 . Tubing  18  is made from flexible thermoplastic tubing and is permanently bonded to port inlet  16 . Tubing  18  is fitted with a suitable connector (not shown) to permit attachment to a tourniquet instrument such as that described by McEwen et al. in U.S. patent application Ser. No. 11/122,600, for the inflation of cuff  10 . Tubing  18  has a length at least equal to the maximum width of cuff  10  and allows cuff  10  to be used inside a sterile surgical field. In the preferred embodiment shown, cuff  10  is a single port cuff, where cuff port  15  provides a single pneumatic passageway to 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. Nos. 4,469,099, 4,479,494, and 5,254,087. 
   As shown in  FIGS. 3 and 4  cuff  10  has a substantially arcuate shape with the width of the cuff reduced near the end edges. The arcuate shape of cuff  10  and the degree to which the width near the end edges is reduced are predetermined to allow cuff  10  to be applied to limbs with a predetermined range of tapers such that cuff  10  remains substantially in contact with the limb along its width around the circumference of the limb. When cuff  10  is correctly applied to a patient limb as shown in  FIGS. 1 and 2 , the side edge of cuff  10  with the greater radius is proximal and the side edge with the lesser radius is distal on the limb. 
   As shown in  FIGS. 1 and 2 , cuff  10  is secured around the limb by securing straps  20  and  22 . Securing straps  20  and  22  are non-releasably attached to a non-inflating region of cuff  10  near an end edge. Securing straps  20  and  22  have fastening portions which releasably engage with the outer surface of cuff  10  and bending portions which permit the fastening portions to be positioned such that they can completely engage the outer surface within the side edges of cuff  10 . In the preferred embodiment the outer surface of cuff  10  and the fastening portions of securing straps  20  and  22  are formed from velcro-type materials. The outer surface of cuff  10  is a loop type material and the fastening portions of securing straps  20  and  22  are formed from hook type material. 
   Limb  14  shown in  FIG. 2 , has a substantially cylindrical shape and has been selected to represent a limb with the minimum amount of taper to which cuff  10  can be applied. As shown in  FIG. 2 , the bending portions of securing straps  20  and  22  twist to permit the fastening portions to move towards the proximal side edge of the cuff so that they may completely engage the outer surface of cuff  10  and maintain their substantially flat shape. 
   Limb  12  shown in  FIG. 1  has a substantially tapered shape and has been selected to represent a limb with the maximum amount of taper to which cuff  10  can be applied. As shown in  FIG. 1 , the bending portions of securing straps  20  and  22  twist to permit the fastening portions to move towards the distal side edge of the cuff so that they may completely engage the outer surface of cuff  10 . 
   When cuff  10  is properly secured around a limb the fastening portions of securing straps  20  and  22  are completely engaged within the side edges of the cuff. The materials comprising the outer surface of cuff  10  and the fastening portions of securing straps  20  and  22  have contrasting colors. In the preferred embodiment, the outer surface of cuff  10  is colored black and the fastening portions of securing straps  20  and  22  are colored white. The contrasting colors provide a user of cuff  10  with a visual indication that the securing straps have been correctly positioned within the side edges of the cuff. When the securing straps are correctly positioned the outer surface of the cuff will be clearly visible completely around the perimeter of the ends of the securing straps. 
   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 . 
     FIG. 3  is an exploded view of the individual components that are joined together as described below to form cuff  10 . For clarity, cuff tubing  18  is not shown in  FIG. 3 . 
   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 as described below. 
   Top sheet  24  forms the outer surface of cuff  10  and is a flexible knit loop nylon material (for example, 200 Series Loop Material, Aplix Inc., Charlotte, N.C. 28241) adapted for secure engagement with the hook material of the fastening portions of securing straps  20  and  22  and secondary fastener  26 . It will be appreciated that top sheet  24  may be made from other types of flexible sheet materials to which velcro-type materials have been permanently attached and that the sheet material may not be completely covered by the velcro-type material. For example top sheet  24  may be comprised of a woven nylon fabric with nylon loop material bonded to the fabric only in predetermined areas for engagement with the fastening portions of securing straps  20  and  22 . 
   Securing straps  20  and  22  are formed from substantially flat flexible inextensible materials, such as the nylon hook material that is commonly used in hook and loop velcro-type fastening applications. As described above, securing straps  20  and  22  have a fastening portion and a bending portion. The bending portion of securing strap  20  and  22  has a width less than the width of the fastening portion, the reduced width of the bending portion allows the bending portion to twist out of its substantially flat shape to facilitate positioning of the fastening portion. It will be appreciated that the fastening portion and bending portion of securing straps  20  and  22  may be comprised of different materials that are permanently joined together to form the securing strap, for example the bending portion may be comprised of a material that is substantially more flexible than the material comprising the fastening portion. For further example, securing straps  20  and  22  could be comprised of a bending portion formed from a segment of grosgrain ribbon which is permanently joined to a fastening portion formed from a segment of nylon hook material. As described above the material comprising the fastening portion of securing straps  20  and  22  is a contrasting color to the material comprising top sheet  24 . 
   Secondary fastener  26  is comprised of hook material similar to the hook material that forms the fastening portions of securing straps  20  and  22 . Secondary fastener  26  is attached to the outer surface of bottom sheet  30  and engages with the loop material of top sheet  24 . Secondary fastener  26  facilitates cuff application and alignment by providing a means for maintaining cuff  10  in position around patient limb  12  while securing straps  20  and  22  are positioned and engaged. The additional fastening surface area provided by secondary fastener  26  allows the length of securing straps to be reduced from what otherwise would be required to maintain cuff  10  secured around a limb and thereby increases the range of limb tapers to which cuff  10  can be applied. Secondary fastener  26  also helps improve the stability of cuff  10  on the limb by resisting lateral movement of the overlapped cuff end. 
   Bottom sheet  30  and middle sheet  32  are made of a flexible woven nylon cloth, coated on one surface with a thermoplastic polymer (for example, 70 Denier nylon cloth coated with thermoplastic polyurethane 0.004″ thick). The thermoplastic polymer coating prevents the passage of gas through bottom sheet  30  and middle sheet  32  and allows bottom sheet  30  to be welded to middle sheet  32  in selected areas to form an inflatable bladder  34  as shown in cross-section in  FIG. 5 . In the preferred embodiment the thermoplastic coating on bottom sheet  30  and middle sheet  32  is polyurethane, but it will be appreciated by those skilled in the art that other thermoplastic polymers may be used as coatings on bottom sheet  30  and middle sheet  32  providing they can be joined with sufficient strength to maintain the integrity of cuff  10  when inflated. 
   Tie strap  36  is a soft fabric polymer coated ribbon material (Grosgrain ⅝″ wide, Dynatex Textiles Inc., Toronto, Ontario, Canada) that is shown in  FIG. 3  positioned between middle sheet  32  and bottom sheet  30  at an end edge of cuff  10 . Tie strap  36  is secured to bottom sheet  30  and middle sheet  32  by welds and provides a means for the user to align and pull cuff  10  snug around the limb. When cuff  10  has been secured around a limb the ends of tie strap  36  are tied together to help maintain the overlapping portion of the cuff in alignment around the limb by preventing the cuff from twisting, telescoping and rolling on the limb when inflated. It will be apparent that tie strap  36  may also be positioned between top sheet  24  and middle sheet  32  near an end edge of cuff  10  and secured by stitching at the side edges of cuff  10 . 
   As shown in  FIG. 4  and in cross-section in  FIG. 5 , port inlet  16  has a right angle configuration and has a flange for bonding with middle sheet  32 . Port inlet  16  is made of a thermoplastic polymer that is compatible with and can be welded to the thermoplastic coating of middle sheet  32  to form a gas-tight seal. 
   Port mask  38  is interposed between port inlet  16  and bottom sheet  30 . In the preferred embodiment, port mask  38  is formed from the same material as bottom sheet  30 . 
   To permit the cost effective manufacture of cuff  10  it is desirable to form the welds joining middle sheet  32  to bottom sheet  30  and port inlet  16  in a single dielectric welding operation. To prevent port inlet  16  from bonding to bottom sheet  30  during the dielectric welding operation port mask  38  is placed below port inlet  16  such that the polyurethane coated surface of port mask  38  is facing the polyurethane surface of bottom sheet  30  and the nylon cloth surface is facing port inlet  16 . 
   During the welding operation, port mask  38  bonds to bottom sheet  30  in the region of the weld area joining the flange of port inlet  16  to middle sheet  32  and forms port mask weld  40  as shown in the cross-section of cuff  10  depicted in  FIG. 5 . Port mask weld  40  secures port mask  38  within inflatable bladder  34  preventing it from interfering with the inflation and deflation of inflatable bladder  34 . The nylon fabric surface of port mask  38  is not compatible with the material comprising port inlet  16  and thereby prevents port inlet  16  from bonding to the top surface of port mask  38  during the welding operation. 
     FIG. 4  is a top view of the preferred embodiment laid flat and shows the areas where middle sheet  32  is welded to bottom sheet  30  and port inlet  16 . Port inlet  16  is welded to middle sheet  32  at port weld  42 . Middle sheet  32  is also welded to bottom sheet  30  at bladder perimeter weld  44 , non-inflating region weld  46 , and flute welds  48 . Top sheet  24  is secured to middle sheet  32  and bottom sheet  30  by stitching  49  around the perimeter of top sheet  24  as shown in  FIG. 5 . 
   Bladder perimeter weld  44  defines inflatable bladder  34  of cuff  10  which is shown in cross-section in  FIG. 5 . Bladder  34  has distal and proximal side edges; the proximal side edge of bladder  34  has a greater radius than the distal side edge of bladder  34 . In the preferred embodiment bladder perimeter weld  44  has a greater width along the distal side edge of bladder  34  than it has along the proximal side edge of bladder  34 . The increased width of the bladder perimeter weld along the distal edge of bladder  34  acts to stiffen the edge of the cuff and thereby help improve the cuff&#39;s roll stability when inflated. Only the width of the bladder weld along the distal edge is increased as inflated cuffs tend to roll only distally down the limb. By increasing the width of the bladder weld only along one side edge in the preferred embodiment the width of the inflatable bladder is maximized for a given overall cuff width. Prior art cylindrical cuffs that are substantially rectangular in shape do not have defined proximal and distal side edges; their orientation when applied to a limb is not predetermined by their shape. Wide bladder welds in prior art cuffs to improve stability must be made along both side edges of the bladder as the cuff may be applied in either orientation, thereby reducing the maximum possible bladder width for a given cuff width. 
   Middle sheet  32  and bottom sheet  30  are joined together by several flute welds  48 ; these welds are perpendicular to the side edges of cuff  10  and extend radially towards the centerline of cuff  10 . Flute welds  48  act in place of a stiffing element to constrain inflatable bladder  34  of cuff  10  when inflated. Flute welds  48  prevent relative lateral movement between selected areas of bottom sheet  30  and top sheet  24  reducing the tendency of cuff  10  to roll along the longitudinal axis of the limb. 
   The perimeter of non-inflating region weld  46  shown in  FIG. 4 , defines a non-inflating region near an end edge of cuff  10 . Secondary fastener  26  is attached to the outer surface of bottom sheet  30  by stitching around its perimeter within the non-inflating region. Securing straps  20  and  22  are attached to the outer surface of top sheet  24  within the non-inflating region also by stitching. The stitching attaching securing straps  20  and  22  passes through the material of secondary fastener  26  which helps to distribute the loads at the attachment points of securing straps  20  and  22  across the end edge of cuff  10 . 
   As shown in  FIG. 4 , securing straps  20  and  22  are attached near the bending portion to the outer surface of top sheet  24  such that they are substantially parallel to the center line of cuff  10 . Securing strap  20  is attached between the centerline and the proximal side edge of the cuff. Securing strap  22  is attached between the centerline and the distal side edge of the cuff. As described above the bending portions of securing straps  20  and  22  allow the fastening portions to be placed in positions other than those substantially parallel to the center line of cuff  10 . 
   It will be apparent that securing straps  20  and  22 , and secondary fastener  26  may be attached by other mechanical fastening means or by welding or adhesives. It will also be apparent that bladder  34  could be extended eliminating non-inflating region weld  46  and the non-inflating region of the cuff. 
   Cuff  10  includes a label  50 , shown in  FIG. 3 and 4 . Label  50  has printed marks to indicate to a user of cuff  10 : that cuff  10  is intended for a single use; the proximal and distal side edges of cuff  10 ; the area of top sheet  24  that secondary fastener  26  and securing straps  20  and  22  are to be completely engaged with. Label  50  is comprised of printed Tyvek label material with a thermally activated adhesive backing. Label  50  is die cut to match the shape of cuff  10  near an end edge and adhered to top sheet  24  near an end edge as shown in  FIGS. 3 and 4 . The Tyvek material of label  50  does not engage with the hook materials of secondary fastener  26  and securing straps  20  and  22 . Label  50  acts as a barrier, preventing secondary fastener  26  and securing straps  20  and  22  from engaging with the loop material of top sheet  24  in the region covered by label  50 . To insure that inflatable bladder  34  completely encircles a limb when secondary fastener  26  and securing straps  20  and  22  are completely engaged with top sheet  24 , the length of label  50  is selected in the preferred embodiment to be substantially equivalent to or greater than the length of the non-inflating region of cuff  10  to which securing straps  20  and  22  and secondary fastener  26  are fixed. 
   Label  50  also acts to stiffen the end edge of cuff  10  and helps prevent the end edge from curling as cuff  10  is pulled snug around a limb by tension on tie strap  36 . 
   The preferred embodiment is substantially comprised of top sheet  24 , middle sheet  32  and bottom sheet  30 . It will be apparent that top sheet  24  may be coated with a thermoplastic coating compatible with the coating on bottom sheet  30  and that middle sheet  32  may be eliminated and an inflatable bladder formed between top sheet  24  and bottom sheet  30 . This would also eliminate the need for stitching  49  securing top sheet  24  to middle sheet  32  and bottom sheet  30 . 
   In the preferred embodiment flute welds  48  help improve the roll stability of cuff  10  when inflated on a limb by preventing middle sheet  32  from moving laterally with respect to bottom sheet  30  at selected locations. It will be apparent that flute welds  48  could be replaced by other means to help prevent roll, such as a stiffening sheet made from a thermoplastic material less flexible than middle sheet  32  and having an arcuate shape. A stiffening sheet may be interposed between top sheet  24  and middle sheet  32  or be interposed between middle sheet  32  and bottom sheet  30  within the perimeter of inflatable bladder  34 . To further improve stability, the stiffening sheet may be bonded to the inner surface of middle sheet  32  such as described in U.S. patent application Ser. No. 11/304,363. 
   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.