Abstract:
A pneumatic tourniquet adapted for self application by an injured person in a military or emergency situation to stop arterial blood loss in an injured arm or leg comprises: a bladder having a width dimension and having a length dimension greater than the circumference of an injured limb of a subject at a selected location; and clamp means for securing the bladder around the limb at the selected location and adapted for sealing the bladder across the bladder width to establish an inflatable portion of the bladder to be the portion of the bladder that encircles the injured limb at the selected location.

Description:
BACKGROUND 
     Loss of blood is a major cause of death in military combat and emergency situations in which the injured person is alone or medical assistance is not immediately available. The use of a tourniquet to stop blood loss from an injured arm or leg is a well-known technique for preventing death in these situations. Once the primary objective of preventing death due to blood loss is achieved, it is desirable to prevent further injury to the limb due to excessive pressure and time of tourniquet application. To minimize mechanical injury to the tissues under the tourniquet, the pressure applied by the tourniquet should be only slightly higher than that required to stop blood flow and the pressure should be applied evenly and uniformly around the limb beneath the tourniquet, without localized regions of very high or very low pressures. To help prevent gangrene and other complications related to the lack of arterial blood flow into the portion of the limb distal to the tourniquet, it is widely accepted that the tourniquet pressure should be released for a period of 5-10 minutes and then reapplied after each two hour period of stoppage of arterial blood flow, also called arterial blood flow occlusion. When more sophisticated care becomes available (such as emergency medical personnel arriving at the scene or evacuation to a field hospital), it is advantageous to have the emergency tourniquet compatible with more sophisticated pneumatic tourniquet systems (such as the pneumatic systems described by McEwen in U.S. Pat. No. 4,469,099) which allow precise control of tourniquet cuff pressure and application time. 
     Published US Army research (Calkins et al, ‘Evaluation of possible battlefield tourniquet systems for the far-forward setting’,  Military Medicine Vol . 165, 5:379, May 2000) defines the need for a light, compact, yet rugged tourniquet for far-forward battlefield use. The victim must be able to apply the tourniquet to his or her own arm or leg and occlude blood flow using only their non-dominant hand. In the Calkins study, a variety of prior art pneumatic and non-pneumatic tourniquets and other non-pneumatic devices adapted for use as a tourniquet (such as ratcheting cargo straps) were tested and found to have disadvantages or to be ineffective in occluding arterial blood flow, particularly when self-applied. Calkins et al reviewed issued patents and found no suitable devices disclosed. 
     In U.S. Pat. No. 4,243,039, Aginsky discloses an emergency tourniquet consisting of a strap and ratchet-type tensioning device, including a tension indicating device and a pointer intended to be set by the user to indicate the time of tourniquet application. In the Calkins study a similar ratchet type devices did not successfully occlude arterial blood flow in all cases and the noisy operation, pinching of the skin, and questionable durability of these types of device was criticized. The pointer device disclosed by Aginsky in the &#39;039 patent requires the victim to set the pointers at the time of tightening the tourniquet and then monitor the current time using separate means to determine when to release the tourniquet. This is a disadvantage in the battlefield or emergency situation because the user, who may be injured and under extreme stress, must have a reliable separate means of measuring time, must remember to set the pointers immediately after tightening the tourniquet the limb, and must be alert enough to monitor the time throughout the maximum desirable period of continuous arterial occlusion. 
     There are many other non-pneumatic constricting devices (such as elastic and non-elastic straps) in the prior art. For example the emergency bandage described by Grau in U.S. Pat. No. 5,628,723 is intended to be wrapped tightly around the limb as a pressure dressing, but may be used as a tourniquet by using a windlass to twist the wrapped bandage and generate sufficient inward radial pressure on the limb to stop arterial blood flow. However the Calkins study showed that these types of devices were generally not capable of stopping arterial blood flow in the limb, particularly when self-applied by the victim. In U.S. Pat. No. 5,314,437, Holtsch describes a constricting device for body parts in which a non-inflating band encircles the body part. When the band is pulled tight, the resulting tension activates a rocker clamp which locks the band at a fixed circumference. Although this device may be easier to self-apply due to the automatic clamp, it is intended for venous occlusion only and it would be difficult or impossible for the victim to generate sufficient tension in the band to occlude arterial blood flow. In U.S. Pat. No. 6,149,666, Marsden describes a constricting strap and fastener device with a battery powered timer and alarm system activated by closure of the fasteners at one or more discrete circumferences. However this non-pneumatic device is a venous tourniquet to assist in various intravenous procedures and is not suitable for arterial occlusion. 
     Non-pneumatic strap type tourniquets such as those described above generate inward radial compression on the limb by being put into high levels of circumferential tension when wrapped around the limb. In ratcheting strap devices (such as that described by Aginsky in the &#39;039 patent) and other strap and buckle type devices (such as that described by Holtsch in the &#39;437 patent and the cargo strap device tested by Calkins), tension is generated by shortening the strap wrapped around the limb. As the pressure on the limb increases, the friction between the strap and the limb also increases, causing the underlying soft tissue to move with the strap as it is drawn tight. This tends to draw soft tissues underlying the strap into the ratchet or buckle device, pinching the soft tissue and creating a region of very high localized pressure which will cause unnecessary injury. This effect may also create high shearing stresses in the underlying soft tissues, increasing the probability of nerve and tissue injury. Friction between the strap and the limb may also create regions of low pressure by preventing tension from being distributed evenly in the strap around the entire limb circumference, and as a result arterial blood may still flow through these low pressure regions although overall strap tension is very high. In general, the uneven or non-uniform application of pressure around the limb resulting from the use of non-pneumatic strap type tourniquets leads to the need for unnecessarily high overall tourniquet pressures to reliably and predictably stop arterial blood flow, and this need for unnecessarily high pressure increases the probability of a range of unnecessary injuries to nerves, muscles and limb. Using a pressure transducer as described by McEwen in U.S. Pat. No. 4,869,265, the inventors of the current invention have found that pressure distribution under non-pneumatic strap type tourniquets is difficult to regulate and can vary significantly between different locations around the limb circumference and between the proximal and distal edges of the strap. In particular, pressures actually applied to the limb can be dangerously high in certain areas (such as the pinched areas described above) with corresponding increased risk of soft tissue and nerve damage. Areas of low pressure can allow arterial blood flow past the tourniquet and lead to higher overall strap tensions being used to maintain arterial occlusion. Furthermore, none of the non-pneumatic devices described above are compatible with typical operating room or field hospital tourniquet systems allowing precise control of tourniquet pressure. 
     Pneumatic tourniquet cuffs have been proven to be effective and safe devices for stopping arterial blood flow and are the standard of care in modern surgery. A pneumatic cuff was the only device tested that successfully stopped arterial blood flow in all trials in the Calkins study. When a pneumatic tourniquet cuff is in use, an inflatable bladder completely encircles the limb and is inflated, causing the bladder to expand and apply inward radial compression to the limb around the entire limb circumference. In contrast to the non-pneumatic devices described above, pneumatic tourniquets apply pressure to the limb that is very closely related to the inflation pressure of the cuff, and this pressure is applied evenly around the entire limb circumference. It is therefore easy to control the pressure applied to the limb by monitoring the cuff inflation pressure, and low pressure areas are minimized. Because the inward radial pressure on the limb is provided by the inflation pressure in the bladder rather than circumferential tension, the cuff does not need to be applied with great tension and the problems of pinching and shearing of the soft tissues (as described in the preceding paragraph) are minimized and self application is easier. A pneumatic tourniquet cuff must, however, be snugly applied around the limb and secured at a fixed circumference to be effective. 
     The pneumatic cuff tested in the Calkins study was similar to the overlapping occlusive cuffs for surgical use described by McEwen in U.S. Pat. Nos. 5,649,954 and 5,741,295. These cuffs consist of an inflatable bladder portion longer than the circumference of the largest limb expected to be occluded with the cuff, such that the bladder overlaps upon itself when wrapped around the limb. To help maintain an even pressure distribution around the limb and to reduce the likelihood of slippage of overlapping regions of the cuff along the limb, the amount of overlap in surgical tourniquet cuffs is generally limited to a range of roughly 1 to 5 inches, meaning that different cuff sizes are required to accommodate the arm and leg circumferences of different individuals. Overlapping pneumatic tourniquet cuffs are intended for use in the surgical setting where a source of compressed gas is available and the cuff is applied by a skilled technician. Typically the appropriate size of cuff is selected and wrapped around the limb and secured by hook and loop type fastening straps. The cuff is then inflated, and the full length of the bladder (both the portion contacting the limb and the overlapping portion) inflates. This type of cuff is undesirable in the battlefield or emergency situation because: 
     It is difficult to wrap these cuffs and close the fasteners with one hand (particularly on one&#39;s own limb), 
     Hook and loop type fasteners can become unreliable when wet and fouled with dirt, 
     The inflated volume of these overlapping cuffs is always large enough for the largest limb in the recommended size range, even when the cuff is applied to the smallest limb in the range. This is a disadvantage when the user must inflate the cuff quickly with a manual pump, and 
     The limb size range of these overlapping cuffs is typically too narrow for a single cuff type to be applied to either an arm or a thigh, and so several different cuff sizes would have to be carried. 
     A non-overlapping tourniquet is described by McEwen in U.S. Pat. No. 4,770,175. This cuff has a sliding clamp that secures the cuff snugly around the limb before inflation, and the excess length of the bladder hangs loose from the clamp. The bladder is inflated from the end of the excess bladder portion, and the clamp therefore allows air inside the bladder to pass through from the excess bladder portion into the bladder portion encircling the limb such that the full length of the bladder inflates; the cuff will not function if the clamp seals the bladder into separate sections. The inflated bladder portions on both sides of the clamp prevent the bladder from sliding through the clamp and therefore help maintain a fixed bladder circumference around the limb. However the additional inflated volume of the excess bladder length is a disadvantage in military and emergency situations, as described above. Furthermore, the clamp described in the &#39;175 patent is intended to be applied by a skilled technician and is not adapted to single-handed operation; specifically the ends of the bladder are held in one hand and the clamp is slid down to the limb and closed using a second hand. 
     Pneumatic tourniquet cuffs require a source of pressurized gas to inflate the bladder, but the weight, bulk, and power requirements of surgical type pressure regulation and time monitoring systems (such as the pneumatic systems described by McEwen in U.S. Pat. No. 4,469,099) make them impractical for emergency self-use. Manual inflation means such as a hand pump or bulb (as shown with the overlapping pneumatic cuff tested by Calkins) is a practical alternative. However, even with manual inflation means, elapsed inflation time and cuff pressure should be monitored and indicated to the user to allow for minimization of the injuries and complications described in the opening paragraph. These monitoring and indicating functions ideally require minimal input from the user, who is likely under extreme stress while using the tourniquet. 
     There is no prior art pneumatic tourniquet for stopping arterial blood flow known to the inventors of the current invention which provides for self-application of the cuff with one hand, is suitable for a range of circumferences allowing application to the upper or lower limb, and inflates only in the region encircling the limb to which the cuff is applied. Furthermore there is no prior art pneumatic tourniquet cuff as described above known to the inventors of the current invention which also includes inflated time indication means automatically activated by manual pressurization of the tourniquet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is shows the tourniquet in use on a user&#39;s thigh. 
     FIG. 2 is an overall view of the tourniquet. 
     FIG. 3 is cross sectional view through the tourniquet showing a flute. 
     FIG. 4 is a section view through a limb with the tourniquet applied snug and inflated with the clamp in the locked position. 
     FIG. 5 is a detail section view through the tourniquet loose on the limb with the clamp in the open position. 
     FIG. 6 is a detail section view through the tourniquet snug on the limb with the clamp in the intermediate position. 
     FIG. 7 is a block diagram of the indicator module. 
    
    
     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. 
     Throughout this document the terms ‘bond’ and ‘bonded’ will generally refer to processes such as radio frequency (RF) welding, ultrasonic sewing and welding, other forms of plastic welding, adhesive bonding, or solvent bonding selected to be suitable for the materials and coatings chosen for the various components of the cuff. Width and thickness of the bonds are selected to produce a joint of sufficient strength to withstand the stresses produced by typical cuff inflation pressures up to 1000 mmHg at various limb circumferences, and in selected areas, to form a gas impermeable joint between the materials. The terms ‘seal’ and ‘sealed’ refer specifically to gas-tight or gas impermeable joints forming an inflatable bladder. 
     FIG. 1 shows the preferred embodiment of the invention applied to a thigh. Cuff  20  is secured around limb  34  by clamp  22 . Port  24 , cuff connector  26 , hose connector  28 , and hose  30  form a gas-tight passageway between inflation bulb  32  and cuff  20 . To apply cuff  20 , the user passes the looped cuff  20  over the distal end of the injured limb  34 , positions it proximal to the wound, then pulls cuff  20  snug around limb  34  and locks clamp  22 . The user then manually inflates cuff  20  by squeezing inflation bulb  32  repeatedly until cuff  20  applies sufficient inward radial compression to the limb to prevent blood from flowing distally past cuff  20 . It will be appreciated that cuff  20  may also be used to apply pressure to a dressing lying directly on the wound, in which case the inflation pressure required will be substantially less than that required to occlude arterial blood flow as described above. 
     Indicator module  36  (described in detail in FIG. 7) is connected pneumatically to the gas tight passageway in hose  30  and indicates cuff pressure and elapsed inflation time to the user of cuff  20 . Indicator module  36  also operates to alert the user and provide instructions if predetermined alarm conditions are present. 
     FIG. 2 is an overall view of cuff  20  laid out flat. Cuff  20  has fixed end  38 , sliding end  40 , and bladder  42  having a length  48  selected to be sufficient for the bladder  42  to completely encircle the largest limb intended for cuff  20 . Cuff  20  is constructed of inner layer  44  lying against the limb and outer layer  46  facing away from the limb, both made of gas impermeable material bonded together along a perimeter to form inflatable bladder  42 . It will be appreciated inflatable bladder  42  may also be formed by bonding together inner layer  44  and outer layer  46  along their long edges and across fixed end  38  only, with the sealed perimeter closed by clamp  22  as shown in FIG.  4 . 
     For illustrative purposes cuff  20  is shown laid out flat with sliding end  40  unthreaded from clamp  22 ; in use sliding end  40  slides through clamp  22  as shown in FIGS. 4,  5 , and  6 . Thus the minimum limb circumference that cuff  20  can be used on is defined by distance  50 , at which circumference port  24  prevents sliding end  40  from continuing through clamp  22 . A suitable length  48  of bladder  42  is 34 inches and a suitable distance  50  is 5 inches. A suitable overall cuff width  52  is 3.5 inches, and bond width  54  is 0.20 inches. Clamp  22  is permanently attached to fixed end  38 , and bladder  42  extends into clamp  22  as shown in detail in FIGS. 4,  5 , and  6 . 
     Clamp width  53  is selected to be larger than overall cuff width  52  to permit sliding end  40  to pass through clamp  22  at an angle relative to fixed end  38 , thus allowing cuff  20  to assume a conical shape when wrapped around a conical limb (such as a typical thigh). This is important in achieving a snug fit around limbs of various degrees of conical shape, thereby reducing the pressure and inflated volume required to stop arterial blood flow in the limb. 
     At sliding end  40 , pull tab  56  is bonded to cuff  20 . Pull tab  56  is made of thin, stiff sheet material such as 0.020 thick polyurethane, durometer 75D, and is cut out along edge  58  to allow the user&#39;s thumb or finger to pass through and pull on sliding end  40  to tighten cuff  20  around the limb. 
     To prevent cuff  20  from rolling down the limb when inflated (particularly when used on a conical limb), inner layer  44  and outer layer  46  are further bonded together at flute  60 . A plurality of flutes  60  are located at selected distances along bladder  42  and prevent expansion of bladder  42  in the region of each flute  60 . A suitable flute spacing  62  is  5  inches and a suitable gap  64  is 0.625 inches. Expansion of bladder  42  is controlled in the area of each flute  60 , eliminating the need for a stiffener as used in typical surgical pneumatic tourniquet cuffs. Fluted bladder designs are further described by McEwen in U.S. Pat. Nos. 5,312,431 and 5,584,853 which are hereby incorporated by reference. 
     Port  24  is permanently bonded to outer layer  46  and includes cuff connector  26  (PMC2202, Colder Products Company, St. Paul Minn.). Hose connector  28  (PMC1702, Colder Products Company, St. Paul Minn.) is permanently attached to hose  30 , which in turn is permanently attached to indicator module  36  and inflation bulb  32 , thereby providing a gas tight passageway from inflation bulb  32  to bladder  42  with a releasable connection at connectors  26  and  28 . If the victim is transferred to a more sophisticated care setting where a conventional surgical tourniquet system (such as that described by McEwen in U.S. Pat. No. 4,469,099) is available, connectors  26  and  28  allow cuff  20  to be connected to the system without removal of cuff  20 . Connectors  26  and  28  are a positive locking design (as described by McEwen in U.S. Pat. No. 5,649,954) which produce an audible click sound when fully engaged and locked, and allow hose  30  to rotate about its cylindrical axis relative to cuff  20  without unlocking or affecting the pneumatic connection. 
     Instructions  66  and symbols  68  are permanently marked on outer layer  46  to aid the user in applying cuff  20 . 
     FIG. 3 is cross sectional view through cuff  20  in the region of bladder  42  passing through flute  60  at one side edge of cuff  20  and through an area between flutes  60  on the opposite side edge of cuff  20 . Inner layer  44  is made of  70  denier woven nylon material with inner surface  70  against the limb and bladder surface  72  coated with a gas impermeable layer of thermoplastic. Smoothness of inner surface  70  is selected to allow cuff  20  to slide against the limb surface as cuff  20  is pulled tight, allowing clamp  22  (shown in FIG. 4) to remain accessible, while not being slippery enough to allow the cuff to slide distally on the limb upon inflation when the cuff and limb are wet. Outer layer  46  is made of  200  denier woven nylon material with a matte, brushed finish on outer surface  76  and coated on bladder surface  78  with a gas impermeable layer of thermoplastic. A suitable thermoplastic layer for both inner layer  44  and outer layer  46  is 0.006 inch thick polyurethane. Outer surface  76  has a selected color to suit the application, such as black for military applications or bright orange for emergency applications. The color of inner surface  70  may be chosen to be different from the color of outer surface  76  to help prevent the user from applying cuff  20  inside out or twisted. To further help prevent application error, symbols may be printed on inner surface  70  indicating that the surface must lie against the limb. 
     For military and emergency applications where cuff  20  may be carried by the user or is part of a compact kit of supplies carried by a medic, it is particularly important that the packed size and overall weight of cuff  20  be minimized. Accordingly the materials for inner and outer layers  44  and  46  are selected to be flexible so that cuff  20  can be easily rolled or folded into a small package, and lightweight. In contrast, many conventional surgical tourniquets have a stiffener within or lying against the bladder, hook or loop type fasteners attached along most of the bladder length, and hook or loop type straps extending beyond a bladder end, all of which prevent compact rolling or folding of the cuff and increase weight. 
     It will be appreciated that a variety of materials and thermoplastics may be chosen for various applications of the invention; for example non-woven fabrics and polyvinylchloride (PVC) thermoplastic may be used if a less costly, less durable version of the invention is desired. 
     It will also be appreciated that to further simplify manufacture, cuff  20  could also be formed out of a gas impermeable tube material (such as 0.025 inch thick 73 durometer flexible PVC) cut to the overall cuff length with a gas-tight bond formed across fixed end  36  (shown in FIG.  2 ). 
     FIG. 4 is a section view through limb  34  with cuff  20  applied and inflated and clamp  22  in the locked position. Also visible are port  24  and pull tab  56 . Application of cuff  20  and operation of clamp  22  are shown in detail in FIGS. 5 and 6. Base  78  and rocker  80  are joined by pivot pin  82  and are free to rotate relative to each other about pivot pin  82 . When clamp  22  is in the locked position as shown, the circumference of cuff  20  is fixed and bladder  42  is sealed across its entire width at sealing ridge  84 , thereby creating inflating portion  86  in contact with the limb and non-inflating portion  88 . Upon inflation, inflating portion  86  expands and, due to its fixed circumference, inward radial pressure is applied to the limb. With sufficient inflation pressure, arterial blood flow in limb  34  distal to cuff  20  is stopped. 
     Sealing the bladder at clamp  22  ensures that the inflated volume is minimized for the particular limb cuff  20  is applied to; for example the length of cuff  20  must be sufficient to encircle most thighs, yet when applied to the typical arm approximately 60% of the length of bladder  20  is not required and not in contact with the limb. The sealing function of clamp  22  is therefore an important advantage minimizing the time and effort required to inflate the cuff and stop bleeding. This is particularly important in the battlefield or emergency situation when cuff  20  is self-applied by the injured person. 
     As clamp  22  is closed, rotation of rocker  80  relative to base  78  is stopped by stop pin  90  striking rocker  80 . Gap  92  between base  78  and sealing ridge  84  is selected to be less than the uncompressed total thickness of the fixed end  38  and the sliding end  40  of cuff  20 . Therefore in the locked position the thermoplastic layers on surfaces  72  and  76  are compressed and form an airtight seal against each other. Fixed end  38  passes through gap  92  to provide two additional layers of compressible material underneath sealing ridge  84 , thereby improving the reliability of the seal between inflating portion  86  and non-inflating portion  88 . Because bladder  42  is compressed against itself underneath sealing ridge  84 , inflating portion  86  completely encircles the limb and has a length substantially equivalent to the limb circumference. 
     To further improve clamping and sealing functions of clamp  22 , in the locked position the center of area of sealing ridge  84  lies over-center distance  94  from the line lying perpendicular to base  78  and passing through the center of pivot pin  82 , thereby forming an over-center lock in which forces resulting from the compression of cuff  20  in gap  92  act to hold rocker  80  in the locked position. Circumferential tension in cuff  20  resulting from inflation also acts to hold clamp  22  in the locked position due to friction in gap  92  acting on rocker  80  in the direction of arrow  100 . An appropriate gap  92  is 0.015 inches and an appropriate over-center distance  94  is 0.030 inches. 
     When clamp  22  is in the locked position, inflating portion  86  encircles the entire circumference of the limb, and the lengths of inflating portion  86  and non-inflating portion  88  vary depending on the circumference of the limb. This is an important distinction from blood pressure cuffs in the prior art (for example the cuff described by Ruff in U.S. Pat. No. 4,727,885), which typically have an inflating portion of fixed length and substantially shorter than the maximum limb circumference intended for the cuff. In these blood pressure cuffs the inflating portion must be positioned over a particular artery and the cuff is not intended to occlude all blood flow in the limb. 
     Inflating portion  86  does not overlap itself, as is typical in occlusive cuffs of the prior art with fixed length, overlapping bladders (for example cuffs described by McEwen in U.S. Pat. Nos. 5,649,954 and 5,741,295). 
     To unlock clamp  22 , rocker  80  must be rotated relative to base  78  in the direction of arrow  96 . Due to the over-center distance  94 , maximum compression of cuff  20  under sealing ridge  84  occurs when rocker  80  is rotated in the direction of arrow  96  to a position where over-center distance  94  is reduced to zero. Therefore the force required to open clamp  22  from the locked position increases slightly as rocker  80  is rotated in the direction of arrow  96 , reducing the chance of accidental unlocking. 
     Secondary locking means is provided by tie strap  98  joining rocker  80  and base  78  and may be applied by the user or other personnel in situations where clamp  22  may be accidentally be opened, such a dragging of the injured person over rough terrain. 
     FIG. 5 is a detail section view through cuff  20 , clamp  22 , and limb  34  similar to FIG. 4, but prior to tightening and inflating cuff  20  and with clamp  22  in the open position. Fixed end  38  of cuff  20  passes through gap  102  between base  78  and rocker  80  and is permanently attached to base  78 . Sliding end  40  passes though gap  102  and is folded over base  78  and retained in the folded over position by hook fastener  104  permanently attached pull tab  56 , and corresponding loop fastener  106  permanently attached to base  78 . Cuff  20  is packaged in the configuration shown in FIG.  5  and thus forms a loop ready to be tightened around the limb. Referring also to FIGS. 1 and 4, upon unpacking the user passes the looped cuff  20  over the distal end of the injured limb, slides it to a position proximal to the bleeding wound, and pulls on pull tab  56 , releasing hook and loop fasteners  104  and  106  and pulling sliding end  40  radially away from the limb (as seen in FIG.  6 ). Gap  102  is sufficient to allow sliding end  40  to pass through clamp  22  easily until cuff  20  is snugly applied to the limb. The opening angle formed as rocker  80  pivots relative to base  78  about pivot pin  82  is limited by stop pin  90 , thereby ensuring that even when fully opened, clamp  22  may be grasped and locked as described in FIG. 4 with one hand. 
     In the event that it is impossible to pass the looped cuff  20  over the distal end of the injured limb, the user may release hook and loop fasteners  104  and  106 , pull sliding end  40  out of clamp  22  in the direction of arrow  100 , wrap the unlooped cuff around the limb, rethread sliding end  40  through gap  102 , and tighten cuff  20  as described above. Pull tab  56  is of selected stiffness greater than that of inner and outer layers  44  and  46  and thereby provides a thin, stiff edge allowing sliding end  40  to be more easily passed through gap  102 . Hook and loop fasteners  104  and  106  prevent accidental unthreading of sliding end  40  from clamp  22  if, for example, the user pulls on region  108  of cuff  20  during unpacking or application. 
     FIG. 6 is a detail section view through cuff  20  pulled snug around limb  34  with clamp  22  in the intermediate position. Snugness can be increased by pulling sliding end  40  in the direction of arrow  110 , creating a pulley effect around rocker  80 . However because the inward radial pressure on the limb is provided by inflation pressure in inflating portion  86  (shown in FIG.  4 ), cuff  20  need only be snug enough around limb  34  to lie closely against the surface of limb  34  and to remain in position until inflation is completed. At the typical snugness required, cuff  20  does not normally apply enough pressure to occlude venous blood flow (typically 20 mmHg). In contrast to prior art non-pneumatic strap type tourniquets which generate sufficient pressure to stop arterial blood flow through cinching up the strap portion encircling the limb to a high tension level (as described in the background), cuff  20  is easier to apply and there is less tendency for soft tissue and clothing underlying cuff  20  to be pinched or drawn into clamp  22  as cuff  20  is made snug around the limb. 
     As cuff  20  becomes snug around the limb, ridge  112  of rocker  80  contacts the limb. The position of ridge  112  relative to pivot pin  82  is selected such that the resulting force from the limb acting on ridge  112  creates a torque acting to turn rocker  80  relative to base  78  such that gap  114  is reduced. Furthermore, edge  116  of base  78  is positioned relative to pivot pin  82  such that contact with limb  34 , along with the increasing snugness of cuff  20  acting on base  78  at fixed end  38 , applies a torque acting to turn base  78  relative to rocker  80  such that gap  114  is reduced. Sufficient snugness of cuff  20  causes gap  114  to reduce to a point where sliding end  40  is held against fixed end  38  with sufficient force to prevent sliding end  40  from passing back through clamp  22  in a direction opposite to arrow  110  (thereby loosening the cuff) if pull tab  56  is released by the user. In this intermediate position of clamp  22 , the user may release pull tab  56  after applying the cuff and use the same hand to lock clamp  22  as described below, allowing the user to apply cuff  20  with one hand. 
     To lock clamp  22  and thereby secure cuff  20  around the limb, the user squeezes pivot  80  towards base  78  in the direction of arrow  118  as far as possible, putting clamp  22  in the locked position shown in FIG.  4 . As clamp  22  moves from the open position shown in FIG. 5 to the intermediate position shown in FIG.  6  and finally the locked position shown in FIG. 4, the distance between ridge  112  on rocker  80  and edge  116  on base  78  increases, so there is no tendency for clamp  22  to pinch the underlying soft tissues or to gather up underlying clothing as cuff  20  is made snug around the limb and secured. 
     FIG. 7 is a block diagram of indicator module  36  connected to cuff  20 . Indicator module  36  operates as described below to indicate cuff pressure (the pressure of gas in bladder  42 ) and elapsed inflation time (the duration of time that the cuff pressure has exceeded a predetermined pressure threshold) to the user of cuff  20 . Indicator module  36  also operates to alert the user and provide instructions if predetermined alarm conditions are present. As shown in FIG. 7 indicator module  36  consists of battery  122 , pressure switch  120 , power switch  136 , pressure transducer  124 , microprocessor  132 , mode switch  134 , display  130  and alarm indicator  128 . 
     Pressure switch  120  communicates pneumatically with bladder  42  and closes when the pressure in bladder  42  increases to a predetermined threshold pressure indicating that cuff  20  is in use and is being inflated. In the preferred embodiment the predetermined threshold pressure that switch  120  closes at is 20 mmHg. Pressure switch  120  makes indicator module  36  easier to use by allowing indicator module  36  to automatically power up upon the inflation of bladder  42 . Furthermore, power is drawn from battery  122  only when cuff  20  is in use, thereby preserving the life of battery  122  and allowing cuff  20  to be stored unused for long periods. When pressure switch  120  is closed, battery  122  supplies power to pressure transducer  124 , alarm indicator  128 , display  130 , and microprocessor  132 . Power switch  136  is connected in parallel with pressure switch  120  and is controlled by microprocessor  132 . When activated by microprocessor  132 , power switch  136  allows battery  122  to continue to supply power to pressure transducer  124 , alarm indicator  128 , display  130 , and microprocessor  132 . 
     When power is first applied to microprocessor  132  through the closure of pressure switch  120 , microprocessor  132  activates power switch  136 , this ensures that microprocessor  132  and related components will remain powered regardless of the pressure in bladder  42 . Microprocessor  132  is programmed to deactivate power switch  136  when the pressure in bladder  42  has remained below a predetermined threshold pressure of 20 mmHg for a predetermined time interval of 60 minutes, thereby further conserving battery  122 . 
     Pressure transducer  124  communicates pneumatically with bladder  42  and provides an indication of the pressure within bladder  42  to microprocessor  132 . Microprocessor  132  is programmed to determine elapsed inflation time by measuring the duration of time that the pressure in bladder  42  has exceeded a predetermined pressure threshold, as indicated by pressure transducer  124 . 
     Display  130  is controlled by microprocessor  132  to indicate cuff pressure, elapsed inflation time, and other instructions to the user. Mode switch  134  allows the user to select which of the monitored parameters, elapsed inflation time or cuff pressure is shown on display  130 . 
     Alarm indicator  128  provides an audible and visual indication of alarm conditions to the user. Microprocessor  132  activates alarm indicator  128  under certain predetermined conditions of pressure and elapsed inflation time. For example, if the pressure in bladder  42  has been inflated above a predetermined threshold and has remained above this threshold continuously for a predetermined elapsed time interval, alarm indicator  128  is activated to warn the user to deflate cuff  20  for a reperfusion period of 5 to 10 minutes to reduce the extent of avoidable ischaemic damage to the limb. A suitable elapsed time interval is 2 hours, suggested by some in the surgical literature as a generally safe period for continuous occlusion in a limb. Alarm indicator  128  may also be activated by microprocessor  132  if unusually high pressures are detected in bladder  42  (for example pressures greater than 400 mmHg) to warn the user that the pressure may be higher than necessary and that the risk of limb injury has increased. 
     Microprocessor  132  may also be programmed to monitor rate of pressure change and activate alarm indicator  128  if a predetermined rate of pressure decline is exceeded, which may mean that cuff  20  is failing to maintain pressure due to damage or improper application. 
     Microprocessor  132  may also be programmed to monitor the difference between a reference pressure and the current pressure in bladder  42  and activate alarm indicator  128  if a predetermined difference is exceeded. For example the reference pressure may be indicated by the user via mode switch  134  when bladder  42  is inflated to sufficient pressure to stop bleeding, and alarm indicator  128  activated if the pressure in bladder  42  falls a predetermined amount below or rises a predetermined amount above the reference pressure, alerting the user to check for bleeding and adjust the inflation pressure if required. 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.