Abstract:
An adaptive tourniquet cuff system comprises: a tourniquet cuff having a physical characteristic and including an inflatable bladder of a length greater than the circumference of a limb at a selected location; a cuff connector carried on the cuff and communicating pneumatically with the bladder for releasably connecting to a tourniquet instrument to establish a gas-tight passageway between the bladder and the tourniquet instrument; and an identifying collar including identification means indicative of the physical characteristic and detectable by the tourniquet instrument upon establishment of the gas-tight passageway. The tourniquet instrument may supply gas to the bladder through the gas-tight passageway at a pressure sufficient to stop arterial blood flow into the limb distal to the cuff at the selected location, and may adapt its operation in response to the detected physical characteristic of the cuff.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. patent application No. 09/920,341, filed Aug. 14, 2001, now U.S. Pat. No. 6,682,547. 

   BACKGROUND 
   The use of an inflatable tourniquet cuff to occlude blood flow into a subject&#39;s limb, thereby providing a bloodless surgical field in the portion of the limb distal to the cuff over a period of time suitably long for the performance of a surgical procedure, is well known in surgical practice. Tourniquet systems typically include an inflatable cuff for encircling a limb at a selected location and a tourniquet instrument for maintaining the pressure in the cuff near a selected pressure. Such tourniquet instruments of the prior art typically contain, or connect to, a source of pressurized gas and include a pressure regulating mechanism for controlling and maintaining the pressure of the gas supplied to the tourniquet cuff near the selected pressure. 
   Typically a variety of cuff sizes are provided so that a cuff that overlaps itself when encircling the limb may be selected, thereby ensuring that pressure is applied to the limb around its entire circumference. Cuffs are also provided in a variety of shapes, widths, materials, configurations and other physical characteristics as required for different types of patients, limb locations, and surgical procedures. 
   Other physical characteristics of the cuff may be the manufacturer of the cuff, the state of sterility or non-sterility of the cuff as supplied by the manufacturer, the size, shape and potential volume of the inflatable bladder or chamber within the cuff, the number of uses the cuff is designed for, and any physical changes that may have resulted from surgical use and any reprocessing after use. 
   Other physical characteristics of the cuff may be the manufacturer of the cuff, the state of sterility or non-sterility of the cuff as supplied by the manufacturer, the size, shape and potential volume of the inflatable bladder or chamber within the cuff, the number of uses the cuff is designed for, and any physical changes that may have resulted from surgical use and any reprocessing after use. 
   Modern tourniquet instruments of the prior art employ digital electronic technology in the regulation of pressure for the tourniquet cuff and in the detection of certain hazardous conditions. However the pressure selected at the tourniquet instrument for regulation within the tourniquet cuff has often been very arbitrarily chosen by surgical staff, regardless of the type or size of cuff connected to the tourniquet instrument. More recently, some surgical staff are selecting lower tourniquet pressures based on the surgeon&#39;s estimate of the minimum pressure required to safely occlude blood flow past the cuff in a specific patient. This minimum safe pressure is affected by a number of variables, including the physical characteristics of the specific tourniquet cuff attached to the patient, and so providing a convenient, reliable and automatic means for the tourniquet instrument to identify certain physical characteristics of that cuff (such as length, width, and type) is useful for adapting the estimate of the minimum safe pressure, either manually with the involvement of the surgical staff or automatically by the tourniquet instrument connected to the cuff. For example, if a wide cuff is identified as being connected to the tourniquet instrument, then the instrument may display instructions to the surgeon to select a lower tourniquet pressure setting than the arbitrary pressure setting that might otherwise be used, to reduce the likelihood of pressure related injury while still stopping blood flow effectively, or the tourniquet instrument may automatically adapt the tourniquet pressure setting to that lower pressure. 
   Automatic identification of the specific cuff connected to the tourniquet instrument also allows adaptation of the settings of important operating and safety parameters of the tourniquet instrument and system as a whole. For example, if a very small pediatric tourniquet cuff is automatically identified as being connected to the tourniquet instrument, then the maximum allowable tourniquet pressure setting can be adapted and reduced to a much lower and safer maximum level without affecting the efficacy of the overall system. Also, the settings of certain alarm parameters within the instrument may be adapted upon automatic identification of the cuff connected to the instrument; for example, the maximum time limits allowed within the instrument for cuff inflation and for cuff deflation may be automatically adapted as a function of the size of the inflatable portion of the connected cuff, to provide a safety alarm signal in the event of a hazardous inability of the instrument to inflate or deflate the cuff within a normal maximum time period while also preventing the generation of false alarm signals. 
   Upon automatic identification of the specific size and type of cuff connected to the tourniquet instrument, and thus the size, shape and potential volume of the inflatable portion of the connected cuff, the settings of other parameters important in the regulation of tourniquet pressure can be adapted to improve the accuracy and responsiveness of pressure regulation. Further, if the cuff type can be automatically identified by a connected tourniquet instrument, then cuff-related data needed for a surgical record may be automatically generated and kept more easily and more accurately for inventory control and cuff utilization purposes. Such a record may also be used (in combination with recording of other parameters such as pressure used) to aid in establishing safer practice guidelines for the use of surgical tourniquets. 
   Cuffs and tourniquet instruments are made by various manufacturers, and it is presently possible for users to connect a tourniquet instrument made by one manufacturer to tourniquet cuffs made by other, unknown manufacturers. However, at least one tourniquet instrument known in the prior art has advanced safety and performance features that are specifically designed to work with tourniquet cuffs that are made by the same manufacturer (see, for example McEwen in U.S. Pat. No. 5,649,954 and McEwen in U.S. Pat. No. 5,681,339). Such safety features and operational features in a tourniquet instrument may not function, or may not function predictably or properly if a cuff from an unknown manufacturer is connected to the tourniquet instrument. Therefore, to avoid or minimize safety hazards, and to minimize potential legal liability for users and for the manufacturer of the tourniquet instrument, it is useful to have a tourniquet instrument that has the capability to automatically identify the manufacturer of the connected cuff and to accordingly adapt the settings of important safety parameters, operating parameters and messages and warnings to users. For example, if such an instrument detects that an unknown cuff type is connected, the instrument could display a warning to the user that certain important functions relating to safety and performance may be disabled. Also, a tourniquet system having the capability to automatically identify the type of connected cuff can permit the sale or lease of the instrument to a user on a peruse basis or in connection with the purchase of specified quantities of cuffs of a known and identifiable type. A variety of related functions could also be performed by a tourniquet instrument having the capability to automatically identify that connected cuffs were, or were not, made by a known manufacturer. For example if an unidentifiable cuff from an unknown manufacturer were connected to such an instrument, the instrument could be programmed to be non-operational; alternatively, the tourniquet instrument could be programmed to remain as operational as possible but warn of the use of an unidentifiable cuff and record the event, so as not to prevent or delay needed surgery. 
   Many tourniquet cuffs are designed for to be reused in multiple surgical procedures and are supplied by the manufacturer in a non-sterile state. Other tourniquet cuffs are designed for single use only, and are supplied in a sterile state (eg. ‘Comforter™ Disposable Gel Cuff’ sold by DePuy Orthopaedics Inc., ‘Zimmer ATS Disposable Tourniquet Cuffs’, Zimmer Patient Care, Dover, Ohio). These cuffs are used when sterility is required in the area where the cuff is applied, and when the cuff must not be re-used in order to prevent cross-contamination between patients. Such single-use sterile cuffs are designed to withstand a specified sterilization process (conducted by the manufacturer) and the typical stresses encountered in a single surgical procedure. Subsequent sterilization or processing may lead to hazardous conditions such as compromised sterility, deteriorated physical condition and possibly sudden failure of the cuff during surgery. In particular, exposure to high temperatures or ethylene oxide gas during sterilization can degrade the materials in these cuffs. Despite these risks, it is increasingly common for users to attempt to reprocess and re-use single-use sterile cuffs using cleaning processes that have not been approved or tested by the original manufacturer. For example, single-use sterile cuffs are routinely reprocessed by at least one company that uses a pasteurization process (which subjects the cuff to high temperature and humidity), and then returned to the user in a ‘high-level disinfected’ state, a non-sterile, lower state of cleanliness than when originally supplied by the manufacturer. Several other companies routinely reprocess single-use sterile tourniquet cuffs using ethylene oxide gas sterilization methods, returning the cuff in a surgically sterile state. Other sterilization methods (such as gamma or electron beam radiation and gas plasma processes) could conceivably be used to reprocess cuffs; however ethylene oxide gas is currently the most common and practical method due to availability of facilities and its suitability for small batch sizes. If exposure to such attempts to reprocess and re-sterilize sterile cuffs after surgical use could be automatically identified by the tourniquet instrument, the tourniquet instrument could adapt by activating various warning functions to alert the user and reduce potential hazards to the patient. No tourniquet cuff is known in the prior art that allows a tourniquet instrument to identify whether a connected cuff has been subjected to a subsequent re-sterilization process, and to adapt its operation accordingly. 
   Many prior-art tourniquet cuffs are color-coded to indicate size to a user by visual inspection. For example the ‘Comforter™ Disposable Gel Cuff’ sold by DePuy Orthopaedics Inc. has a color dot on the outer packaging label corresponding to the cuff size, but no indication of cuff size on the cuff itself. In several other types of tourniquet cuff (for example ‘Zimmer ATS Disposable Tourniquet Cuffs’, Zimmer Patient Care, Dover, Ohio), components permanently attached to the cuff (such as edge trim and/or tie ribbon) are made of a selected color of material corresponding to the cuff size. These identification means are solely visual and interpretable by the user who is familiar with the color coding scheme. No communication with a tourniquet instrument is automatically established by connection of the cuff to the instrument, and therefore the instrument necessarily cannot automatically adapt the settings of important parameters of operation and safety in response to the size and type of cuff connected to the instrument. 
   In U.S. Pat. No. 4,605,010, McEwen describes a tourniquet cuff that includes an electrical means for identifying remotely the physical characteristics of the cuff, as well as for remotely determining the circumference of the limb encircled by the cuff. To permit remote identification of cuff type, the McEwen &#39;010 cuff includes electrically conductive components within the cuff structure, and requires an electrical connection as well as a pneumatic connection between the tourniquet cuff and the tourniquet instrument. Thus electrical power and an electrically conductive pathway are necessarily present within the cuff, in close proximity to the patient&#39;s limb encircled by the cuff. This can present a hazard to the patient under some circumstances. Also, inclusion of electrical components within the tourniquet cuff significantly increases the cost and complexity of manufacture of such cuffs, and their reliability at time of manufacture and subsequently during use. The prior art tourniquet cuff described by McEwen &#39;010 includes means for allowing a connected tourniquet instrument to remotely determine the circumference of the limb encircled by the cuff. This permits the tourniquet pressure setting to be adjusted, based on the relationship between the physical characteristics of the remotely identified cuff and the remotely identified circumference of the limb encircled by the cuff. No other tourniquet systems in the prior art known to the inventors of the current invention establish a connection other than a pneumatic connection between the cuff and the instrument, such that information about the cuff can be received by the instrument and such that the settings of important safety and operating parameters of the instrument can be adapted in response. Further, fundamental problems inherent in the significantly increased cost and complexity, and in the inherently decreased reliability, of the apparatus described in McEwen &#39;010, have prevented the commercial realization of any tourniquet systems incorporating apparatus such as described in McEwen &#39;010. 
   No adaptive tourniquet cuff system is known in the prior art that includes provision for the tourniquet instrument to automatically identify physical characteristics of the connected tourniquet cuff and to adapt the settings of certain safety and operating parameters in response. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to an adaptive tourniquet cuff system that comprises: a tourniquet cuff having a physical characteristic and including an inflatable bladder of a length greater than the circumference of a limb at a selected location; a cuff connector carried on the cuff and communicating pneumatically with the bladder for releasably connecting to a tourniquet instrument to establish a gas-tight passageway between the bladder and the tourniquet instrument; and an identifying collar including identification means indicative of the physical characteristic and detectable by the tourniquet instrument upon establishment of the gas-tight passageway. The tourniquet instrument may supply gas to the bladder through the gas-tight passageway at a pressure sufficient to stop arterial blood flow into the limb distal to the cuff at the selected location, and may adapt its operation in response to the detected physical characteristic of the cuff. 
   The methods and apparatus for carrying out the invention are described in detail below. Other advantages and features of the present invention will become clear upon review of the following portions of this specification and the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is shows the tourniquet system with cuff identification means and a set of cuffs. 
       FIG. 2  is a section view through the connection arrangement between the fill line assembly and the tourniquet instrument, with block diagrams of the related electronic components in the instrument and the fill line assembly. 
       FIG. 3  is a detail view of the connection arrangement between the cuff and the fill line assembly with the connectors disengaged. 
       FIG. 3   a  is a section view from  FIG. 3 , showing the connectors engaged. 
       FIG. 4  is a detail view of the identifying collar. 
       FIG. 4   a  is a section view of the identifying collar of  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A specific embodiment illustrated is not intended to be exhaustive or to 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. 
     FIG. 1  shows the preferred embodiment of the invention consisting of tourniquet instrument  12 , fill line assembly  14 , and cuff set  16 . Fill line assembly  14  includes fill line connector  26  and cuff identification module  32 . Cuff set  16  comprises contour calf cuff  50  which has physical characteristics suitable for application to a lower leg within size and shape limits and contour thigh cuff  51  which has different physical characteristics suitable for application to a thigh within different size and shape limits. For clarity, physical characteristics of cuff  50  and cuff  51  include their size, shape, materials, and stiffness. Also for clarity, a physical characteristic may be predetermined to allow identification of the manufacturer of cuff  50  and  51  by tourniquet instrument  12  in the same way that a label allows visual identification of the manufacturer. Similarly, a physical characteristic may be predetermined to allow identification that cuffs  50  and  51  have been exposed to a predetermined process such as sterilization, in the same way that a process indicator label allows visual identification of exposure to the process. As described below cuff  50  includes an inflatable bladder portion and has a port manifold  76 , hose  74 , and cuff connector  20  permanently attached allowing a source of pressurized gas to be connected to the bladder. Cuff set  16  may comprise, for example, different size cuffs of similar design, a selection of cuffs designed for use on pediatric patients, or cuffs made by a particular manufacturer and are appropriate for use with the system. Each cuff in cuff set  16  has a cuff connector  20  and a distinctly colored identifying collar  21  indicating the cuff&#39;s distinct physical characteristic, both to the user (visually) and to instrument  12  as described below. 
   When the system is being used in surgery, at least one cuff from cuff set  16  is wrapped around the patient&#39;s limb  13  at a location proximal to the surgical site. Cuff  50  from cuff set  16  is shown in  FIG. 1  connected to fill line assembly  14  by engaging cuff connector  20  (DSM2202, Colder Products Company, St. Paul, Minn.) with fill line connector  26  (a suitable connector being a modified version of a PMC 17-02 female locking connector made by Colder Products Company, St. Paul, Minn.). The embodiment shown is a “single port” system in which fill line assembly  14  provides a single gas-tight passageway from instrument  12  to cuff  50  for the purpose of inflating, sensing and regulating the pressure in, and deflating the cuff as required by the user (as is typical in many modern tourniquet systems). In the current invention fill line assembly  14  additionally provides a means for transmitting light between fill line connector  26  and cuff identification module  32 , and a means for transmitting electrical signals between cuff identification module  32  and instrument  12 . Fill line assembly  14  may be disconnected from instrument  12  for cleaning or replacement, therefore cuff identification module  32  incorporates means for making both pneumatic and electrical connections to instrument  12 . Instrument  12  additionally includes a cuff identification display  15 , both described below and shown in detail in  FIGS. 2 and 3 . The current invention is equally well suited to “dual port” systems (as described by McEwen in U.S. Pat. No. 4,469,099, also typical in modern tourniquet practice), which include two separate pneumatic connections to the cuff, one for sensing the pressure within the cuff and one for supplying pressurized gas to the cuff. With a dual port system, cuff identification module  32  and the associated light and electrical signal transmitting means may be incorporated into either pneumatic connection or both. 
     FIG. 2  shows a section view through the connection arrangement between cuff identification module  32  (included in fill line assembly  14 ) and tourniquet instrument  12 . The body of cuff identification module  32  slides into socket assembly  19 , which is rigidly mounted in instrument  12 . To prevent accidental disconnection, locking tab  23  engages slot  25  in socket assembly  19  and upon engagement makes an audible click indicating to the user that the connection is complete. Locking tab  23  can be released by applying pressure in the direction of arrow  27  and pulling cuff identification module  32  out of socket assembly  19 . 
   Fill line assembly  14  further comprises: hose  36  made of flexible polyurethane; fill line connector  26  shown in  FIGS. 1 and 3 ; send fiber  24 ; and return fiber  28  (both made of 0.035″ diameter plastic optical fiber PGR F3500, Moritex USA Inc., San Diego Calif.). Send fiber  24  and return fiber  28  lie within the lumen of hose  36  and are thus protected from damage. In the preferred embodiment hose  36  has an outside diameter of 0.25 inches and an inside diameter of 0.13 inches. Hose  36  is coupled to pneumatic connector  33 , which in turn makes a releasable pneumatic connection to gas pressure source and regulating means  18  included in instrument  12  via socket assembly  19 . Send fiber  24  and return fiber  28  pass through holes  40  and  42  and are bonded in place such that a gas-tight passageway is maintained from gas pressure source  18  to the lumen of hose  36  and in turn to the inflatable bladder of the cuff attached to the system. One end of send fiber  24  is optically coupled to three-color light emitting diode (LED)  22  (NSTM515AS, Nichia Corp., Tokushima, Japan) and one end of return fiber  28  is optically coupled to photodiode  30  (TSL 257, Texas Advanced Optoelectronic Solutions, Plano, Tex.). Light emitting diode  22  and photodiode  30  are controlled by additional hardware and software included in circuit board  34 . 
   Cuff identification module  32  communicates with instrument  12  and cuff identification display  15  (see  FIG. 1 ) via electrical connector  35  to indicate to a user the physical characteristic of the cuff connected to instrument  12 . Those skilled in the art will appreciate that electrical connector  35  and cuff identification display  15  have communication pathways to the control electronics and system software of instrument  12  such that various functions of instrument  12  may be modified and information may be recorded based on the physical characteristic of the cuff connected to the system as detected by cuff identification module  32 . It will also be appreciated that fill line assembly  14  and the associated software included in cuff identification module  32  can be easily adapted to function with a variety of different tourniquet instruments that can be equipped with socket assembly  19 . 
   It will also be obvious that advancements and continued miniaturization and integration of color light emitting diodes and photodiodes may permit these elements to be readily incorporated in fill line connector  26  and that send and return optical fibers  24  and  28  could be replaced with electrical conductors. One current example of such miniature integrated color LED and photodiode reflective color sensors are the TTRS1722, TRS1755, and TRS1766 from Texas Advanced Optoelectronic Solutions, Plano, Tex. 
   Those skilled in the art will appreciate that incorporating electrical connector  35  into instrument  12  such that pneumatic and electrical connections to the fill line assembly are made simultaneously allows easy adaptation of instrument  12  to work with tourniquet cuffs using electrical identification means (such as those described by McEwen in U.S. Pat. No. 4,605,010) by use of a corresponding fill line assembly. 
     FIGS. 3 and 3   a  show the connection arrangement between cuff  50  and fill line assembly  14  (see  FIG. 1 ). Cuff connector  20  is permanently attached to hose  74 , which in turn is permanently attached to cuff  50  (see  FIG. 1 ). Cuff connector  20  and fill connector  26  are a positive locking design and produce an audible ‘click’ when fully engaged, maintain a gas-tight passageway when rotated relative to one another about the lumen centerline and when subjected to tension along the lumen centerline, and require a releasing force substantially perpendicular to the lumen centerline in order to be disengaged. In particular, flange front surface  110  of cuff connector  20  actuates the locking pin  112  of fill line connector  26  and gap  114  (see  FIG. 3   a ) between flange front surface  110  and fill connector front face  116  is typically 0.030 inches when the connectors are fully engaged. The design of connectors  20  and  26  is based on connectors described by McEwen in U.S. Pat. No. 5,649,954. 
   Collar  21  (shown in detail in  FIGS. 4 and 4   a ) is held against flange back surface  118  of cuff connector  20  when hose  74  is in place. Referring to  FIGS. 4 and 4   a , collar  21  comprises disc portion  120  and flange portion  122  with central hole  124  having a diameter greater than the inside diameter of hose  74  and less than the outside diameter of hose  74 . Collar  21  is made entirely of electrically insulating, non-conductive material of selected color and opacity, with the color corresponding to a chosen physical characteristic of the cuff. 
   Referring to  FIGS. 3 and 3   a , identifying surface  126  of collar  21  extends proud of flange front surface  110  of cuff connector  20  by overlap  128  so that identifying surface  126  is in contact with fill line connector front face  116  when the connectors are fully engaged. Overlap  128  is greater than gap  114  and disc portion  120  of collar  21  is of selected stiffness such that when the connectors are engaged, disc portion  120  of collar  21  flexes, acting as a spring maintaining contact between identifying surface  126  and fill connector front face  116  when the connectors are engaged and also when tensile and bending forces typically encountered during use are applied between the connectors. 
   For adaptation to the current invention, fill connector  26  has holes  130  and  132  and holes  134  and  136  extending from the outer surface to the inner bore of fill connector  26 . Holes  130 ,  132 ,  134 , and  136  have diameters matching send fiber  24  and return fiber  28 , and the fibers are bonded into the holes such that their ends lie within distance  138  (approximately 0.030 inches) from the fill connector front face  116 . This physical configuration of send fiber  24  and return fiber  28  within fill connector  26  permits light emitted by send fiber  24  to illuminate identifying surface  126  and light reflected from identifying surface  126  to be transmitted to instrument  12  by return fiber  28 . Holes  130  and  132  are each arranged at angle  140  (26 degrees) determined by the optical properties of send and return fibers  24  and  28  to optimize the collection of reflected light by return fiber  28 . Thus when connectors  20  and  26  are fully engaged, a pneumatic pathway is established between cuff  50  and instrument  12  and at the same time light can be transmitted between collar  21  and instrument  12  allowing cuff  50  to be identified as described below. Both the pneumatic pathway and the light transmission pathway are maintained if the connectors are rotated relative to one another about the lumen centerline or subjected to tension along the lumen centerline. 
   Maintenance of contact by the selected stiffness of disc portion  120  and the selected interference between identifying surface  126  and fill connector front face  116  as described above helps minimize interference and signal saturation due to high intensity ambient light (for example if the coupled connectors  20  and  26  fall under the beam of surgical lamps during use). The body of fill line connector  26  is preferably opaque to minimize interference and signal saturation due to high intensity ambient light. Collar  21  is manufactured to have consistent color and opacity such that the light reflected from the collar remains within predetermined limits when cuff connector  20  and collar  21  are rotated relative to fill line connector  26  about the lumen centerline, and such that the light reflected from mass produced colored collars is also within predetermined tolerance limits. 
   It will be appreciated by those skilled in the art that the color and properties of collar  21  are selected depending on the physical characteristic to be identified. For example if only the cuff manufacturer needs to be identified, then all cuffs in cuff set  16  would have the same color of collar  21 . If different sizes and types of cuffs within cuff set  16  need to be identified, then each distinct size and type would have a particular color of collar  21 . If exposure to a selected process such as ethylene oxide (EO) sterilization must be identified, collar  21  may be coated on identifying surface  126  with an active indicating compound which responds to the selected process by changing color. For example, identifying surface  126  may be coated with EO sterilization indicating ink (Tempil Inc., South Plainfield N.J.) which is red and remains stable throughout packaging, gamma radiation or electron beam sterilization by the manufacturer, and use. Upon exposure to a subsequent EO sterilization process, identifying surface  126  changes to a brown color. It will be appreciated by those skilled in the art that identifying surface  126  may alternately be formed by applying a separate material containing indicating ink such as an adhesive film (eg. Steri-Dot #361001, Propper Manufacturing Company, Long Island City, N.Y.) or, as chemical indicators of EO exposure continue to be developed, formed by including the indicating compound in the material used to form collar  21 . 
   It will also be appreciated that collar  21  may be integrated into cuff connector  20  for ease of manufacture, in which case the integrated collar and connector may be made of a non-electrically conducting material of selected color and opacity for each physical characteristic requiring identification. It will also be appreciated that other connector arrangements are possible which establish a pneumatic communication between the cuff and the instrument and a means for transmitting light between the cuff and the instrument. For example send and return fibers  24  and  28  may be arranged such that light is transmitted through collar  21  (if collar  21  is made from translucent material) rather reflected from collar  21  as described above. Also the current invention may be adapted for dual port tourniquet systems (as described in the background) that comprise a single connector with two separate gas passageways and send and return fibers  24  and  28  applied to a selected passageway as shown in  FIGS. 3 and 3   a , or a pair of send and return fibers applied to each passageway as shown in  FIGS. 3 and 3   a.    
   It will also be appreciated that because collar  21  provides means for identifying the cuff without interfering with or modifying the pneumatic connection means, the invention may be adapted to various other types of pneumatic connectors other than the particular type shown in the preferred embodiment. 
   Referring to  FIGS. 1 ,  2 , and  3 , cuff identification module  32  operates as described below to determine the type of cuff connected to instrument  12  as indicated by the color of identifying collar  21 . Cuff identification module  32  communicates with cuff identification display  15  and to other components within instrument  12  to indicate the type of cuff connected to instrument  12 . When instrument  12  is switched on cuff identification module  32  is activated. In operation cuff identification module  32  activates LED  22  to emit a continuous series of red, green, and blue light pulses in succession (for example a 0.5 millisecond pulse of each color with a 1.5 millisecond delay between colors). The light output from LED  22  is optically coupled to send fiber  24  and transmitted to connector  26 . The light pulses generated by LED  22  are emitted from send fiber  24  within connector  26  and illuminate identifying collar  21  when cuff connector  20  is engaged in fill line connector  26  to establish the gas-tight passageway between cuff  50  and instrument  12 . 
   One end of return fiber  28  is optically coupled to photodiode  30 , the other end is terminated within connector  26  such that light reflected from identifying collar  21  can be transmitted to photodiode  30 . In the absence of identifying collar  21  ambient light is transmitted to photodiode  30 . 
   Cuff identification module  32  monitors the intensity level of light detected by photodiode  30 . By recording the detected intensity levels at the times when red, green and blue light is being emitted from LED  22  and when LED  22  is inactive, cuff identification module  32  can compute the relative intensities of red, green and blue light reflected from identifying collar  21  and the intensity of ambient light detected when LED  22  is inactive. The detected intensity levels of ambient light recorded when LED  22  is inactive are used by cuff identification module  32  to compensate for variations in ambient lighting conditions and detect error conditions such as the complete saturation of photodiode  30 . The computed relative intensity levels of red, green and blue light reflected by identifying collar  21  are compared by cuff identification module  32  to predetermined ranges of relative intensities stored within cuff identification module  32  and corresponding to each cuff in cuff set  16 . The cuff type is determined when a predetermined number of reflected light pulses (for example five consecutive series of red, green and blue light pulses) all have relative intensities falling within the predetermined range matching the cuff type. Once identified, the cuff type and/or related predetermined information may be displayed on cuff identification display  15  and recorded within cuff identification module  32 , information from other components within instrument  12  such as time and date, pressure setting, and tourniquet inflated time may also be recorded by cuff identification module  32 . 
   The colors corresponding to the various different cuff types in cuff set  16  are selected to produce distinct relative intensity levels of reflected red, green and blue light. Cuff identification module  32  may be initially calibrated in order to adjust the stored predetermined ranges of relative intensities corresponding to specific cuff types to compensate for changes in component specifications and manufacturing variations. Calibration may be performed by using a series of reference colored connectors, and similarly re-calibration may be performed in the field by the user or by service personnel. 
   An example of the operation of cuff identification module  32  is as follows. When a specific type of cuff from cuff set  16  having a red identifying collar  21  is connected to fill line assembly  14 , green and blue light pulses generated by LED  22  are absorbed by the red identifying collar  21  to a greater degree than the red light pulses generated by LED  22 . Consequently the intensity of the red light pulses reflected from the red identifying collar  21  relative to the intensity of the reflected green and blue light pulses is greater. Cuff identification module  32  will identify the attached cuff as corresponding to a specific type having a red identifying collar  21  by comparing the relative intensities of the light reflected from the red colored cuff connector and sensed by photodiode  30  to a predetermined selection of stored relative intensity values. Once the color of identifying collar  21  has been identified or it has been determined that no identifying collar  21  with a identifiable color is present, predetermined signals are sent by cuff identification module  32  to instrument  12  via electrical connector  35 , and instrument  12  automatically adapts selected functions and parameter settings accordingly. 
   Cuff identification module  32  in conjunction with instrument  12  also operates to detect potentially hazardous conditions. During operation cuff identification module  32  continuously monitors the absolute intensity levels of the reflected red, green and blue light pulses and the intensity level of ambient light when LED  22  is inactive. A sudden drop in intensity levels indicates possible disengagement of connectors  20  and  26  or a kink in hose  36 . If hose  36  and fibers  24  and/or  28  are kinked such that the specified minimum bend radius of the fiber(s) is exceeded, the intensity level of light detected by photodiode will be reduced as light can no longer be transmitted by the optical fibers. If a sudden reduction in detected light levels is concurrent with falling cuff pressure and a corresponding high demand for pneumatic pressure from instrument  12 , warning of a possible disconnection at connectors  20  and  26  may be activated. If signal loss is not accompanied by loss of pressure or high demand for pneumatic pressure from instrument  12 , warning of a possible kink in hose  36  may be activated. 
   Cuff identification module  32  can, by recording the intensity levels of detected light over a number of uses, enable various automatic system optimization and self-calibration functions. For example a gradual reduction in detected light levels over time or a number of uses may indicate wear and degradation of the fill line assembly  14  and a service advisory message may be displayed. Similarly, changes in light levels corresponding to a particular type of cuff over time may activate a self-calibration function or service advisory. 
   Once the cuff has been identified or it has been determined that an unidentifiable cuff is connected, the operation of instrument  12  is adapted accordingly. Some examples of the automatic adaptation of the operation of instrument  12  are as follows: 
   As an example of the physical characteristic of the cuffs being type and size, cuff identification module  32  and instrument  12  may be programmed to identify and adapt to a predetermined set of colors of identifying collar  21  each corresponding to a cuff size and type in cuff set  16 . In this example, contour thigh cuff  51  ( FIG. 1 ) is equipped with a blue identifying collar  21  and upon identification of the blue color by cuff identification module  32 , instrument  12  adapts the default pressure setting to 250 mmHg, which has been found to be appropriate for most patients when this particular cuff is used. To inform the user, cuff identification display  15  is adapted to show ‘Contour Thigh Cuff’ and ‘Default Pressure 250 mmHg’ messages. Similarly, contour calf cuff  50  is equipped with a yellow identifying collar  21 , and when this cuff is connected and identified, instrument  12  automatically adapts the default pressure setting to 200 mmHg, a more appropriate pressure setting for contour calf cuff  50 , and display  15  is adapted to show ‘Calf Cuff’ and ‘Default Pressure 200 mmHg’ messages. In addition, the settings of selected parameters affecting the operation of instrument  12  (such as alarm delay times and pressure regulation limits as described by McEwen in U.S. Pat. No. 4,469,099) may be automatically adapted to better suit the smaller inflated volume of contour calf cuff  50  as compared to contour thigh cuff  51 . If a cuff that is not equipped with an identifying collar  21  having one of the predetermined colors (and therefore does not belong to cuff set  16 ), instrument  12  adapts the default pressure setting to zero and displays an ‘Unknown Cuff Type’ message in display  15 ; the user must then set the tourniquet pressure manually. 
   As an example of the physical characteristic of the cuff being the cuff manufacturer, all cuffs made by the cuff manufacturer may be equipped with red identifying collars  21  and form cuff set  16 . Upon connection of any cuff in cuff set  16 , instrument  12  adapts display  15  to show an ‘Approved Cuff’ message and adapts predetermined parameter settings (such as tubing obstruction signals as described by McEwen in U.S. Pat. No. 5,861,339) to suit the physical characteristics of manufacturer&#39;s cuffs. If the connected cuff is not equipped with a red identifying collar  21 , instrument  12  adapts display  15  to show ‘Unapproved Cuff Type’ and ‘Line Occlusion Alarms Disabled’ messages. Additionally, instrument  12  may be programmed to be non-operational, to operate only after user intervention, or operate for a limited number of surgical cases only with unidentifiable cuffs connected. Instrument  12  may also be programmed to record the number of times unapproved cuffs are used. 
   As an example of the physical characteristic of the cuff being whether the cuff has been subjected to a subsequent re-sterilization process, cuffs in cuff set  16  may be equipped with identifying collars  21  having a process indicating ink coating on identifying surface  126  (see  FIGS. 4 and 4   a ). Upon identification of the color of identifying surface  126  representing exposure to the re-sterilization process, instrument  12  adapts display  15  to show warning messages ‘Used Cuff’ and ‘Cuff may not be sterile’. Additionally, instrument  12  may be programmed to be non-operational, to operate only after user intervention, or operate for a limited number of surgical cases only with reprocessed cuffs connected. Instrument  12  may also be programmed to record the number of times reprocessed cuffs are used. 
   It will be appreciated that a combination of different physical characteristics may be identified by using a plurality of identifying surfaces, each having a send/return fiber pair. For example if both cuff type and exposure to ethylene oxide sterilization must be detected, type could be identified by a distinct color of connector  20  (as described in the parent application) and exposure to EO sterilization could be identified by identifying collar  21  as described above. If multiple identifying surfaces are used, detected colors may be compared to enable various automatic system optimization and self-calibration functions. For example if identifying collar  21  has a common color for all cuffs in cuff set  16  indicating that the cuff has not been exposed to EO sterilization and cuff connector  20  has a predetermined color corresponding to the cuff type, the relative intensity level of light reflected from identifying collar  21  may also be used as a reference to adjust the stored predetermined ranges of relative intensities corresponding to specific cuff types. 
   It is to be understood that the invention is not to be limited to the details herein given but may be modified within the scope of the appended claims.