Patent Publication Number: US-2020297569-A1

Title: Compression devices

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to compression devices for applying compression to a limb of a subject. In particular, embodiments disclosed herein relate to actuators for compression devices for applying compression to different zones on a limb and to compression patterns applied by compression devices. 
     BACKGROUND OF THE INVENTION 
     Arteries carry blood from the heart out to the rest of the body and veins carry blood back to the heart, and valves in the veins stop the blood from flowing backward. About 90% of venous return from the legs is through the action of the muscle pumps. The calf muscle pump is the most important muscle pump in the leg and is active during walking and ankle movement. As a result, the effectiveness of the calf muscle pump depends on normal calf muscle activity. This itself requires good ankle mobility, a normal gait and lack of neurological deficit. 
     Calf muscle function decreases with increasing age, at least partly as a result of reduced muscle bulk. In addition, when veins have trouble sending blood from the limbs to the heart venous insufficiency occurs. In this condition, the flow of blood through the veins is inadequate, causing blood to pool in the legs. 
     Active compression benefits people with lower limb circulation issues or at risk for blood clots in the legs by improving venous return through effective muscle pump action. 
     For athletes, adequate recovery has been shown to result in the restoration of physiological and psychological processes, so that the athletes can compete or train again at an appropriate level. Many recovery strategies for elite athletes are based on medical equipment or therapies used in patient populations. Compression clothing is one of these strategies that have been traditionally used to treat various lymphatic and circulatory conditions. Compression garments are thought to improve venous return through application of graduated compression to the limbs from distal to proximal. The external pressure created may reduce the intramuscular space available for swelling and promote stable alignment of muscle fibers, attenuating the inflammatory response and reducing muscle soreness. 
     Massage is a widely used recovery strategy among athletes. However, apart from perceived benefits of massage on muscle soreness, few reports have demonstrated positive effects on repeated exercise performance. Furthermore, increased blood flow is one of the main mechanisms proposed to improve recovery (thus improving clearance of metabolic waste products). 
     Active compression devices may also be beneficial for athletes by improving venous return through the application of active compression to the limbs from distal to proximal. The external pressure created reduces the intramuscular space available for swelling and promote stable alignment of muscle fibers, reducing the inflammatory response and muscle soreness. Also, the contraction and relaxation of the muscle groups and blood vessels will mimic the calf muscle pump activity, thereby increasing circulation and reducing the lactic acid build up on the muscles. This is beneficial in improving psychological aspects of recovery and may have potential benefits for injury prevention, management and improving performance. 
     SUMMARY OF THE INVENTION 
     Some aspects of the present disclosure relate to compression patterns which are applied to the limb of the subject. The compression patterns generally comprise a sequence of compression cycles. Each compression cycle may comprise a compression period followed by a relaxation period. In the compression period compression pressure is applied to the limb of the subject. In the relaxation period, the compression pressure is reduced to a initial pressure. 
     According to first aspect of the present disclosure, a method of controlling a compression device is provided. The compression device is configured to apply compression to a plurality of compression zones on a limb of a subject. The compression zones are each at a different distance from the torso of the subject. The method comprises: in a compression period, generating control signals to separately vary the pressure applied in each of the compression zones such that for each adjacent pair of compression zones the pressure applied at a distal zone of the pair of compression zones is greater than to the pressure applied at a proximal zone of the pair of compression zones. 
     In some embodiments in at least part of the compression period, the pressure in each of the compression zones is varied simultaneously. The fact that the zones operate simultaneously, and sometimes with a few seconds between starting of the compression cycle, ensures that the subject&#39;s blood is continuously moving in the limb without any holding periods. 
     Many existing compression devices compress a leg zone by zone individually which makes the blood stagnant in one particular zone or compartment. 
     In some embodiments the method comprises generating control signals for a plurality of compression cycles, each compression cycle comprising a compression period followed by a relaxation period. 
     In some embodiments the method comprises generating control signals to reduce the pressure applied in each compression zone during the relaxation period. 
     In some embodiments, a first type of compression pattern is used wherein during the compression period, the pressure applied in each of the zones is gradually increased from a first pressure to a second pressure and compression of the distal zone of a pair of compression zones starts before the proximal zone of the pair of zones. 
     In some embodiments, a second type of compression pattern is used wherein the compression pressure applied to each compression zone is repeatedly varied between a maximum value for that zone and a minimum value for each zone. This pulsing sequence creates a vacuum in the veins of the subject causing more blood to be drawn in from lower zones which makes the compression therapy more effective. 
     In some embodiments, the method comprises reducing the compression pressure applied at a given zone within 5 seconds of the applied compression pressure reaching the maximum value for that zone. In some embodiments the method comprises reducing the compression pressure applied at a given zone within 2 seconds of the applied compression pressure reaching the maximum value for that zone. 
     If a zone is held at its maximum pressure for a more than a few seconds, the result is that there is no antegrade blood flow from that zone. Thus by starting the relaxation period within 5 seconds or less after a zone reaches its maximum pressure it is ensured that there is always a continuous blood flow in the veins. 
     In an embodiment during a compression period, the maximum value for the proximal zone of the pair of zones is substantially equal to the minimum value for the distal zone of the pair of zones. The difference between the maximum value and the minimum value for a zone is less than 30 mmHg and preferably less than 20 mm Hg in some embodiments. 
     An advantage of such embodiments is that during the compression period, the pressure only varies by a relatively small amount, thus energy consumption is reduced. 
     In some embodiments, the compression device is configured to send a synchronization signal to a second compression device. This provides for synchronization of compression patterns applied to each leg of a subject. The synchronization signal may be an infrared signal or a wireless network signal. The synchronization signal may comprise an indication of the compression pattern. 
     According to a second aspect of the present disclosure, there is provided a compression device which is configured to apply compression to a limb of a subject according to one of the compression patterns described above. The compression device may be operable to provide both patterns and may be provided with a user interface to allow selection of a desired compression pattern. 
     According to a third aspect of the present disclosure there is provided a computer readable carrier medium carrying instructions which are executable by a controller of a compression device to cause the device to apply compression to a limb of a subject according to one of the compression patterns described above. A user may be able to select a desired compression pattern from a plurality of options. 
     According to a fourth aspect of the present disclosure, there is provided a method of enhancing blood flow in a limb of a subject. The method comprises applying a compression device to a limb of a subject and controlling the compression device to apply compression according to one of the compression patterns described above. 
     According to a fifth aspect of the present disclosure there is provided a method of aiding recovery from physical exertion in a subject. The method comprises applying a compression device to a limb of a subject and controlling the compression device to apply compression according to one of the compression patterns described above. 
     A compression sleeve, such as a passive compression sock may be applied to the limb of the subject under the compression device. 
     According to a sixth aspect of the present disclosure, a method in a master compression device being configured to apply compression to a limb of a subject is provided. The method comprises receiving a user input indicating a selection of a compression sequence; generating control signals to apply the selected compression sequence to the limb of the subject; generating a synchronization signal for a slave compression device, the synchronization signal comprising an indication of the selected compression sequence; and transmitting the synchronization signal to the slave device. 
     According to a seventh aspect of the present disclosure a compression device configured to apply compression to a limb of a subject according to a compression pattern is provided. The compression device comprises a communication module configured to send a synchronization signal to a second compression device and/or receive a synchronization signal from a second compression device. 
     According to an eighth aspect of the present disclosure, a compression device comprising: a first inflatable bladder formed between a first membrane and a second membrane is provided. A plurality of baffles are provided that couple the first membrane to the second membrane. 
     The compression device may comprise a second inflatable bladder formed between the first membrane and the second membrane, wherein the first bladder and the second bladder are arranged to apply compression to compression zones each being a different distance from the torso of the subject. The first bladder and the second bladder may be configured to be independently inflated/deflated. 
     In some embodiments, the first bladder and the second bladder are separated by a boundary formed by bonding the first membrane to the second membrane. 
     In some embodiments the baffles are arranged parallel to an axis of the limb of the subject when the compression device is in use. Gaps may be provided in the baffles and the positioning of the gaps is offset between neighbouring baffles. 
     According to a further aspect of the present invention an actuator module for a compression device is provided. The actuator comprises a body portion and a pair of coupling portions. The body portion comprises an actuator configured to urge the coupling portions towards the body portion. The coupling portions are attached or attachable to an active layer which is configured to apply a compression pressure to a limb of a subject when the coupling portions are drawn towards the body portion. 
     In an embodiment, wherein the coupling portions are removably attachable to the active layer. The coupling portions are removably attachable to different locations on the active layer. This allows for adjustment to be made of the fit of the compression device to the subject. This may also allow the active layer to be pretensioned. 
     The actuator module may comprise a motor and the motor is coupled to a cable and pulley system configured to urge the coupling portions towards the body portion. 
     An actuator portion for a compression device may be formed from a plurality of actuator modules such that the coupling portions of each of the actuator modules is attached or attachable to different locations on the active layer such that different compression pressures can be applied to different compression zones of the limb of the subject. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, embodiments of the present invention will be described as non-limiting examples with reference to the accompanying drawings in which: 
         FIG. 1  shows a compression device according to an embodiment of the present invention; 
         FIGS. 2 a  and 2 b    respectively show an active layer and an actuator portion of a compression device according to an embodiment of the present invention; 
         FIGS. 3 a  and 3 b    show the internal arrangement of an actuator component of a compression device according to an embodiment of the present invention; 
         FIG. 4  shows an actuator module which incorporates a controller and a battery according to an embodiment of the present invention; 
         FIGS. 5 a  and 5 b    show an actuator portion of a compression device according to an embodiment of the present invention; 
         FIG. 6  is a block diagram that schematically shows an actuator component of a compression device according to an embodiment of the present invention; 
         FIGS. 7 a  to 7 i    show variations of a first compression pattern type according to an embodiment of the present invention; 
         FIGS. 8 a  to 8 f    show variations of a second compression pattern type according to an embodiment of the present invention; 
         FIGS. 9 a  to 9 d    are graphs showing results of a sports study using a compression device according to an embodiment of the present invention; 
         FIGS. 10 a  and 10 b    are graphs showing results of a travel study using a compression device according to an embodiment of the present invention; 
         FIG. 11  shows schematically a pneumatic compression device according to an embodiment of the invention 
         FIGS. 12 a  to 12 f    show a pneumatic compression device according to an embodiment of the present invention; 
         FIG. 13  shows the internal configuration of an actuator portion of a pneumatic compression device according to an embodiment of the present invention; 
         FIG. 14  shows an inflatable bladder component within a pneumatic compression device according to an embodiment of the present invention; 
         FIG. 15  shows an inflatable bladder module of a compression device according to an embodiment of the present invention; 
         FIG. 16  shows a pair of compression devices which are provided with infrared communication modules according to an embodiment of the present invention; and 
         FIG. 17  shows a pair of compression devices which are provided with wireless communication modules. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a compression device according to an embodiment of the present invention. The compression device  100  comprises an active layer  110  and an actuator portion  120 . The active layer  110  forms a compression sleeve or sock, which is worn on a limb of a subject. In this example, the active layer  110  is shaped to be worn on the lower leg of a human subject. 
     The actuator portion  120  is detachable from the active layer  110 . When the actuator portion  120  is attached to active layer  110 , the compression device  100  is operable to apply varying compression to different zones of the limb of the subject. 
       FIGS. 2 a  and 2 b    respectively show an active layer and an actuator portion of a compression device according to an embodiment of the present invention. 
     As shown in  FIG. 2 a   , the active layer  110  is formed from a fabric material. In this example, the active layer  110  comprises a stretchable material part  112  that is located at the front of the wearer&#39;s leg and is located over the wear&#39;s shin when the active layer is worn. The active layer  110  further comprises a coupling portion  114  which allows actuator modules of the actuator portion to be attached to the active layer  110  and thereby apply compression to the limb of a subject. In this example, the coupling portion  114  of the active layer  110  is provided as a loop material provided on the exterior of the sides of the compression sleeve. This loop material can be detachably coupled to a hook material provided on arms of the actuator portion  120 . The active layer  110  has a non-stretchable fabric part that is located at the sides and back of the wearer&#39;s leg when the active layer  110  is worn. The top and bottom edges of the active layer  110  are provided with an elastic edge binding  116 . 
     In the embodiment described above in relation to  FIG. 2A , the stretchable material part  112  serves two purposes. Firstly, it provides for adjustability to allow the active layer  110  fit closely to the limb of the subject. Secondly, the force provided by the stretchable material part  112  provides a base level of compression. In the following description this base level of pressure is called pretension pressure or initial pressure. It is envisaged that in embodiments, these attributes may be provided by alternative features, such as an adjustable strap and fastener which would allow the subject to manually vary the base level of compression and also to fit the active layer  110  to their limb. In some embodiments, a compression sock or sleeve may be worn under the active layer  110  to provide a base level of compression. 
     The non-stretchable part of the active layer  110  allows the transfer of mechanical energy generated by the actuator portion  120  to the leg muscles as a form of a compression without significant energy loss. 
     The materials of the active layer  110  may be selected to provide a smooth surface finish of the active layer  110  reducing friction between contact surfaces. Furthermore, fabrics with breathability, and moisture-wicking may be used. 
     As shown in  FIG. 2 b   , the actuator portion  120  comprises three actuator modules  122 ,  124  and  126 . A top actuator module  122  corresponds to an upper calf region, a middle actuator module  124  corresponds to a lower-calf region and a bottom actuator module  126  corresponds to an ankle region. 
     In this embodiment, a pair of arms  132   134  and  136  extends from each of the actuator modules  122   124  and  126 . The inner surface of the arms comprises a hook material which can attach to the loop material on the active layer  110 . Thereby a high shear resistant connection can be formed between the active layer  110  and the arms of the actuator modules. The arms  132   134  and  136  provide coupling portions of the respective actuator modules which are detachably couplable to the coupling portion  114  of the active layer  110 . 
     It is envisaged that alternative methods of coupling the actuator modules  122   124  and  126  to the active layer may be used. For example, the arms  132   134  and  136  may be coupled to the active layer  110  via a hook and eye system, magnetic strips or via snap buttons. In alternative embodiments, the arms  132   134  and  136  may be replaced by straps which attach to the active layer  110  via buckles or other types of strap fasteners. Alternatively, cable loops may extend from the actuator modules and the active layer  110  may be provided with attachments for these cable loops. 
     Thus, the actuator portion  120  can be attached to the active layer  110  via respective coupling portions on the top actuator module  122 , the middle actuator module  124  the bottom actuator module  126 . 
     Each of the top actuator module  122 , the middle actuator module  124  and the bottom actuator module  126  comprises a motor which is configured to pull the arms or more generally the coupling portion towards the actuator modules and thus increase the tension in the active layer  110 . Thus the actuator portion  120  when attached to the active layer  110  operates to selectively increase the tension in different regions of the active layer  110  and thereby apply or modify compression pressure applied to different zones of the subject&#39;s leg or limb. 
     In the embodiment shown in  FIGS. 1, 2   a  and  2   b , three zones are defined by the actuator module. Thus, the top actuator module  122  defines a top compression zone, the middle actuator module  124  defines a middle compression zone and the bottom actuator module  126  defines a bottom compression zone. 
     Each of the actuator modules can be separately controlled to apply compression patterns to the subject&#39;s limb. These compression patterns are described in more detail below. 
     It is envisaged that actuators within the actuator modules  122   124  and  126  may be implemented with various actuation types. For example, pneumatic actuators which apply compression using a pump, or a compressed air or gas source which may be controlled by an electric current or voltage; electric actuators such as electric motors which convert electrical energy from a battery or other power source into mechanical energy; shape memory alloy actuators; or electro-active polymer based actuators may be used to implement the actuator modules. Examples of shape memory alloy based actuators are provided in PCT application publication WO2015038599; US patent application publication US20150073318; US patent application publication US20160374886; and U.S. Pat. No. 9,161,878. An example of an electro-active polymer material is provided in U.S. Pat. No. 9,433,537. 
       FIGS. 3 a  and 3 b    show the internal arrangement of an actuator component of a compression device according to an embodiment of the present invention. In this example, the actuation is provided by an electric motor. The actuator component  300  comprises a body portion  300  and two arm portions  320   a  and  320   b . The arms  320   a  and  320   b  are mounted on sliders  325  which allow the arms  320   a  and  320   b  to move relative to the body portion  300 . 
     The body portion  300  forms a housing for a motor  330 , a gear box  332 , and a worm gear set  334 . The each of the cam gears  336   a  and  336   b  is coupled to a respective cable and pulley system which acts to pull the arm portions  320   a  and  320   b  towards the body portion  300 . 
     A first cable (not shown in  FIGS. 3 a  and 3 b   ) runs from a spindle beneath one of the cam gears  336   a  through to pulleys  340   a  mounted on an arm  320   a  and back to an anchor point  344   a  on the body portion  300 . Similarly, a second cable (also not shown in  FIGS. 3 a  and 3 b   ) runs from a spindle beneath the other of the cam gears  336   b  through to pulleys  340   b  mounted on an arm  320   b  and back to an anchor point  344   b  on the body portion  300 . The arms  320   a  and  320   b  each have a travel relative to the body portion in the range 15 mm to 30 mm. 
     Compression is applied to a limb of the subject by the cables wound around the respective spindles and thus producing a force urging the arms towards the body of the actuator module. Thus causing the motors to rotate in one direction causes the compression pressure applied at a given zone to increase. Similarly, when the motors rotate in the opposite direction, the cable is released and the compression pressure applied to the limb of the subject reduces. In some embodiments, the actuator portion may be provided with a spring or similar mechanism to urge the arms outwards when the cable is released. In other embodiments, this outward force may be provided by either a stretchable portion of the active layer or simply by the release of compression pressure on the limb of the subject. 
       FIG. 4  shows an actuator module which incorporates a controller and a battery according to an embodiment of the present invention. As shown in  FIG. 4 , a controller module  360  in the form of a printed circuit board is mounted on one side of the actuator  300  and a battery is mounted on the opposite side of the actuator  300 . 
       FIGS. 5 a  and 5 b    show an actuator portion of a compression device according to an embodiment. As shown in  FIG. 5 a   , the top actuator module  300   a  and the middle actuator module  300   b  each comprise a respective controller module  360   a  and  360   b ; and a respective battery  370   a  and  370   b  in this example, the bottom actuator module  300   c  does not include a controller module and battery. It is noted that the control modules  370   a  and  370   b  may each contain parts of a complete controller which function together to control all three of the actuator modules. Similarly, the two batteries  370   a  and  370   b  may be coupled to the three actuators which in this example are motors. Thus the two controller modules  370   a  and  370   b  may be considered together as a single controller. Similarly, the two batteries  370   a  and  370   b  may be considered together as a single battery. In alternative embodiments the actuator modules may each comprise a separate controller and battery. 
     As shown in  FIG. 5 b   , each of the respective actuator modules  300   a    300   b  and  300   c  has a cover  380   a    380   b  and  380   c  which protects the internal components of the actuator module. In an alternative embodiment, the three actuators may be covered by a single enclosure. 
       FIG. 6  is a block diagram that schematically shows an actuator component of a compression device according to an embodiment of the present invention. The actuator component  800  comprises a controller  810 , a battery  820 , a top actuator module  830 , a middle actuator module  840 , and a bottom actuator module  850 . 
     The controller  810  comprises a control processor  812 , storage for compression patterns  814 , a user interface  816  and a wireless network interface  818 . The control processor  812  may be implemented as a general-purpose processor that is operable to execute processor executable instructions or may be a hard-wired control processor. The storage for compression patterns  814  stores data that indicates compression patterns that may be used by the control processor  812  to generate control signals for motors in the actuator modules. The storage for compression patterns  814  may be implemented as a non-volatile storage. The user interface  816  may be implemented as any form of interface that allows a user to input commands and parameters. For example, the user interface may be implemented as a display and a plurality of input buttons, or a touch screen display. The wireless network interface  818  is an interface such as a Wi-Fi or Bluetooth interface which allows the controller to send and receive data and commands from a wireless enabled device such as a smartphone device or a computer device. 
     The battery  820  may be a rechargeable battery or a primary battery and may be implemented as a plurality of cells. The battery  820  supplies electrical power to the controller and the components of the actuator modules. In some embodiments, the battery may be replaced by a power supply configured to provide suitable electrical power, for example by converting a mains voltage. 
     As described above in relation to  FIG. 5 a   , the battery  820  and controller  810  may be distributed among the actuator modules, alternatively, they may be housed in a separate control module. 
     The top actuator module  830  comprises an actuator  832  and a sensor  834 . As described above, the actuator  832  is configured to apply a compression pressure to a top compression zone of a subject&#39;s limb. The sensor  834  is arranged on the compression device to measure the compression pressure applied to the top compression zone. 
     The middle actuator module  840  comprises an actuator  842 , and a sensor  844 . As described above, the actuator  842  is configured to apply a compression pressure to a middle compression zone of a subject&#39;s limb. The sensor  844  is arranged on the compression device to measure the compression pressure applied to the middle compression zone. 
     The bottom actuator module  850  comprises an actuator  852 , and a sensor  854 . As described above, the actuator  852  is configured to apply a compression pressure to a bottom compression zone of a subject&#39;s limb. The sensor  854  is arranged on the compression device to measure the compression pressure applied to the bottom compression zone. 
     The sensors  834   844  and  854  may be located on the respective actuator modules or may be located on the arms which couple to an active layer  110 . The sensors  834   844  and  854  may be implemented as pressure sensors which directly measure the pressure applied to one of the respective compression zones, alternatively the sensors may be configured to indirectly measure a quantity from which the applied pressure can be derived or estimated, for example the sensors may be implemented as strain gauges mounted on the body of the actuator device and configured to measure the tension in the cables. In some embodiments the sensors may be implemented to measure variables of the actuator, such as the current or rotational in a motor position from which the torque on the motors and therefore the pressure applied to the compression zones can be derived. When the actuators are pneumatic the sensors may be air pressure sensors. When the actuators are shape memory alloys, the sensors may be temperature sensors. 
     Generally, the sensors will be configured to measure or sense the compression force or pressure. This measurement may be carried out by sensing variables of the actuators, such as input current, and deriving the compression pressure from these variables, or the compression force or compression pressure may be measured by the sensors. 
     When in operation, the control processor  812  generates control signals for the actuators of the actuator modules based on compression pattern data stored in the storage for compression patterns  814 . These control signals may be, for example, controlled current and voltage signals to drive the respective motors. The control processor  812  may receive feedback signals from sensors such quadrature encoders and may adjust the current and voltage supplied to the actuators such that the pressure applied to the compression zones is as specified by compression pattern data stored in the storage for compression patterns. 
     While  FIG. 6  shows the controller  810 , the battery  820 , the top actuator module  830 , the middle actuator module  840  and the bottom actuator module  850  are separate modules, this is for illustrative purposes to simplify the functionality and it should be appreciated that the various functionalities may be housed in combination. For example, the functionality of the controller  810  and the battery  820  may be included in the housing of one or more of the actuator modules. The battery  820  may be implemented as a plurality of cells which may be split between housings of different actuator modules. In some embodiments the actuator modules may all be contained in a single housing with the controller  810  and battery  820  included in this housing. 
     It is also envisaged that some of the control processing implemented by the controller  810  by be carried out by a smart phone or other computing device which is coupled to the controller via the wireless interface  818 . In such embodiments, the storage for compression patterns  814  may also be implemented in the smart phone or other computing device. It will also be appreciated that additional compression patterns may be downloaded and stored in the storage for compression patterns  814 . 
       FIGS. 7 a - i  and 8 a - f    below show examples of compression patterns which may be stored in the storage for compression patterns  814 . 
       FIGS. 7 a  to 7 i    show variations of a first compression pattern type according to an embodiment of the present invention. 
     The first compression pattern type involves a sequence of compression cycles. Each compression cycle may be considered to comprise a compression period followed by a relaxation period. During the compression period, the compression pressure in each of the compression zones is increased from an initial pressure or pretension pressure to a peak pressure value. During the relaxation period, the pressure in each of the compression zones returns to the initial pressure pressure. 
     Initially all of the compression zones are set to the initial pressure. This initial step may be implemented by the control processor  812  receiving feedback data from the sensors and controlling the actuators such that the pressure is adjusted to the initial pressure. Alternatively, the user may set the initial pressure by adjusting active layer  110 . 
     In the Figures, the initial pressure is shown as 20 mmHg, however, this may be adjusted, either by the user as mentioned above, or to pre-programmed set values stored in the controller  810 . In some embodiments, the initial pressure is set at a value in the range 10 to 30 mmHg for each of the compression zones. In other embodiments, different initial pressures or pretension pressures are set for different zones, for example the bottom zone may be set to an initial pressure of 110 mmHg, the middle zone to a initial pressure of 100 mmHg and the top zone may be set to an initial pressure of 90 mmHg. 
     Then, as shown in  FIG. 7 a   , at a bottom zone start point  902 , the compression pressure of the bottom zone is increased gradually from the initial pressure to a bottom zone peak value  912 . Starting at a later time, the middle zone start point  904 , the compression pressure of the middle zone is gradually increased from the initial pressure to a middle zone peak value  914 . The middle zone peak value  914  is lower than the bottom zone peak value  912 . Starting at a later time, the top zone start point  906 , the compression pressure of the top zone is gradually increased from the initial pressure to a top zone peak value  916 . The top zone peak value  916  is lower than the middle zone peak value  914 . 
     The bottom zone reaches the bottom zone peak value  912  at approximately the same time as the middle zone reaches the middle zone peak value  914  and the top zone reaches the top zone peak value  916 . The period between the bottom zone compression starting and all three zones reaching their respective peak values is referred to as a compression period  910 . 
     Following the compression cycle  910 , the compression pressure of the three zones is gradually reduced to the initial pressure. This reduction is referred to as a relaxation period  920 . Once the three zones have returned to the initial pressure, a second compression period  930  begins and this is followed by a second relaxation period  940 . A third compression period  950  and relaxation period  960  are then carried out. 
     In the embodiment shown in  FIG. 7 a   , the bottom zone start point  902  is at 0 seconds, the middle zone start point  904  is at 3 seconds and the top zone start point  906  is at 5 seconds; the bottom zone peak value  912  is 110 mmHg, the middle zone peak value  914  is 100 mmHg and the top zone peak value  916  is 90 mmHg. The compression periods  910 ,  930  and  950  each last 20 seconds and the relaxation periods each last 10 seconds. 
     In the embodiment shown in  FIG. 7 b   , the bottom zone peak value  912  is 110 mmHg, the middle zone peak value  914  is 100 mmHg and the top zone peak value  916  is 90 mmHg. The compression periods  910 ,  930  and  950  each last 15 seconds and the relaxation periods each last 10 seconds. 
     In the embodiment shown in  FIG. 7 c   , the bottom zone peak value  912  is 80 mmHg, the middle zone peak value  914  is 70 mmHg and the top zone peak value  916  is 60 mmHg. The compression periods  910 ,  930  and  950  each last 20 seconds and the relaxation periods each last 10 seconds. 
     In the embodiment shown in  FIG. 7 d   , the bottom zone peak value  912  is 80 mmHg, the middle zone peak value  914  is 70 mmHg and the top zone peak value  916  is 60 mmHg. The compression periods  910 ,  930  and  950  each last 15 seconds and the relaxation periods each last 10 seconds. 
     In the embodiment shown in  FIG. 7 e   , the bottom zone peak value  912  is 50 mmHg, the middle zone peak value  914  is 40 mmHg and the top zone peak value  916  is 30 mmHg. The compression periods  910 ,  930  and  950  each last 20 seconds and the relaxation periods each last 10 seconds. 
     In the embodiment shown in  FIG. 7 f   , the bottom zone peak value  912  is 50 mmHg, the middle zone peak value  914  is 40 mmHg and the top zone peak value  916  is 30 mmHg. The compression periods  910 ,  930  and  950  each last 15 seconds and the relaxation periods each last 10 seconds. 
       FIGS. 7 g  to 7 i    show a variation on the embodiments described above. As shown in  FIG. 7 g   , at the bottom zone start point  902 , the compression pressure of the bottom zone is increased gradually from the initial pressure to a bottom zone peak value  912 . Starting at a later time, the middle zone start point  904 , the compression pressure of the middle zone is gradually increased from the initial pressure to a middle zone peak value  914 . The middle zone peak value  914  is lower than the bottom zone peak value  912 . Starting at a later time, the top zone start point  906 , the compression pressure of the top zone is gradually increased from the initial pressure to a top zone peak value  916 . The top zone peak value  916  is lower than the middle zone peak value  914 . 
     In this embodiment, the bottom zone reaches the bottom zone peak value  912  at earlier than the middle zone reaches the middle zone peak value  914  which is earlier than the time the top zone reaches the top zone peak value  916 . 
     In this embodiment, the bottom zone is maintained at the bottom zone peak value  912  for a bottom zone peak period  922 , the middle zone is maintained at the middle zone peak value  912  for a middle zone peak period  922  and the top zone is maintained at the top zone peak value  914  for a top zone peak period  924 . The compression period for this embodiment includes the bottom zone peak period  924  and period between the bottom zone compression starting and the bottom zone reaching the bottom zone peak value  912  is referred to as a compression period  910 . 
     Following the compression cycle  910 , the compression pressure of the three zones is gradually reduced to the initial pressure. This reduction is referred to as a relaxation period  920 . Once the three zones have returned to the initial pressure, a second compression period  930  begins and this is followed by a second relaxation period  940 . A third compression period  950  and relaxation period  960  are then carried out. 
     In the embodiment shown in  FIG. 7 g   , the bottom zone start point  902  is at 0 seconds, the middle zone start point  904  is at 5 seconds and the top zone start point  906  is at 10 seconds; the bottom zone peak value  912  is 110 mmHg, the middle zone peak value  914  is 100 mmHg and the top zone peak value  916  is 90 mmHg. The bottom zone peak period  922  is 12 seconds, the middle zone peak period  924  is 8 seconds and the top zone peak period  926  is 5 seconds. The compression periods  910 ,  930  and  950  each last 20 seconds and the relaxation periods each last 5 seconds. 
     In the embodiment shown in  FIG. 7 h   , the bottom zone start point  902  is at 0 seconds, the middle zone start point  904  is at 3 seconds and the top zone start point  906  is at 5 seconds; the bottom zone peak value  912  is 80 mmHg, the middle zone peak value  914  is 70 mmHg and the top zone peak value  916  is 60 mmHg. The bottom zone peak period  922  is 10 seconds, the middle zone peak period  924  is 8 seconds and the top zone peak period  926  is 5 seconds. The compression periods  910 ,  930  and  950  each last 20 seconds and the relaxation periods each last 5 seconds. 
     In the embodiment shown in  FIG. 7 i   , the bottom zone start point  902  is at 0 seconds, the middle zone start point  904  is at 3 seconds and the top zone start point  906  is at 5 seconds; the bottom zone peak value  912  is 110 mmHg, the middle zone peak value  914  is 100 mmHg and the top zone peak value  916  is 90 mmHg. The bottom zone peak period  922  is 10 seconds, the middle zone peak period  924  is 8 seconds and the top zone peak period  926  is 5 seconds. The compression periods  910 ,  930  and  950  each last 20 seconds and the relaxation periods each last 5 seconds. 
     In the embodiments described above, it is noted that during the compression cycles which may be considered to be formed from a compression period followed by a relaxation period, apart from when the zones are at the initial pressure, at any given time, the compression pressure applied to the bottom zone is greater than the compression pressure applied to the middle zone which in turn is greater than the compression pressure applied to the top zone. 
     Further embodiments are possible in which the bottom, middle and top peak values are equal and as described above in reference to  FIGS. 8 a  to 8 f   , the compression in the bottom compression zone starts earlier than the compression in the middle compression zone which in turn starts earlier than the compression in the top compression zone. Thus, the compression pressure applied in the bottom zone is therefore greater than or equal to the compression pressure applied in the middle which in turn is greater than or equal to the compression pressure applied in the top zone. 
     Further modifications to the values are possible, the compression pressure may take any values in the range 20 mmHg to 200 mmHg. The compression periods may last for between 5 seconds and 5 minutes. The relaxation periods may last for between 5 seconds and 60 seconds. The overall therapy time may last between 5 minutes and 2 hours. 
       FIGS. 8 a  to 8 f    show variations of a second compression pattern type according to an embodiment of the present invention. 
     The second compression pattern type involves a sequence of compression cycles. Each compression cycle may be considered to comprise a compression period followed by a relaxation period. The compression pressure in each of the compression zones is increased from a initial pressure to a peak pressure value, then the pressure in the zone is decreased to a lower pressure value which is less than the peak pressure value but greater than the initial pressure. Each of the compression periods includes a plurality of mini cycle in which the compression pressure is varied between the peak pressure value and the lower pressure value for that compression zone. Following the compression period, there is a relaxation period. During the relaxation period, the pressure in each of the compression zones returns to the initial pressure. 
     As shown in  FIG. 8 a   , initially all of the compression zones are set to the initial pressure of 20 mmHg. Then the compression pressure at the bottom compression zone is gradually increased from the initial pressure to bottom compression zone peak value  1003 . At approximately the time that the bottom zone reaches the bottom zone peak value  1003 , the compression pressure at the middle compression zone is gradually increased from the initial pressure to a middle compression zone peak value  1005 . As the compression pressure in the middle compression zone is increased, the compression pressure in the bottom zone is gradually decreased to a bottom compression zone lower value  1004 . In the example shown in  FIGS. 8 a  to 8 f   , the bottom compression zone lower value  1004  is equal to the middle compression zone peak value  1005 . The compression pressure at the bottom compression zone reaches the bottom zone lower compression value  1004  at approximately the same time as the middle compression zone reaches the middle compression zone peak value  1005 . At approximately the same time, compression in the top compression zone begins and the compression pressure in the top compression zone is gradually increased to a top compression zone peak value  1007 . The compression pressure in the middle compression zone decreases to a middle compression zone lower value  1006  and the compression pressure in the bottom compression zone increases back to the bottom compression zone peak value  1003 . The compression pressure in the top zone then decreases to a top compression zone lower value  1008 . Thus as shown, the compression pressure in each of the zones alternates between a peak value and a lower value. This alternation may be considered as a series of mini-cycles  1015  in which the compression pressure varies out of phase in neighboring compression zones so that when the compression pressure at the bottom compression zone is at the bottom compression zone peak value  1003 , the compression pressure at the middle compression pressure is at the middle compression zone lower value  1006  and the compression pressure at the top zone is at the top compression zone peak value  1007 . Further in the example shown in  FIGS. 8 a  to 8 f   , the bottom compression zone lower value  1004  is equal to the middle compression zone peak value  1005 . Similarly, the middle compression zone lower value  1006  is equal to the top compression zone peak value  1007 . 
     Following two complete mini-cycles  1015 , the compression pressure in each of the compression zones is gradually decreased back to the initial compression. Thus a complete compression cycle may be considered as a compression period  1010  followed by a relaxation period  1020  in which the compression pressure is reduced to the initial compression. The compression period  1010  comprises a plurality of mini-cycles  1015 . A second compression period  1030  and a second relaxation period  1040  then, a third compression period  1050  and a third relaxation period  1060  follow. 
     In the embodiment shown in  FIG. 8 a   , the compression in the middle compression zone starts 15 seconds after compression in the bottom compression zone. Compression in the top compression zone starts 27 seconds after compression in the bottom zone. The bottom compression zone peak value  1003  is 110 mmHg. The bottom compression zone lower value  1004  is 90 mmHg. The middle compression zone peak value  1005  is 90 mmHg. The middle compression zone lower value  1006  is 70 mmHg. The top compression zone peak value  1007  is 70 mmHg. The top compression zone lower value  1008  is 50 mmHg. Each mini-cycle  1015  lasts 12 seconds. The compression period  1010  lasts 60 seconds and the relaxation period  1020  lasts 10 seconds. 
     In the embodiment shown in  FIG. 8 b   , the compression in the middle compression zone starts 10 seconds after compression in the bottom compression zone. Compression in the top compression zone starts 18 seconds after compression in the bottom zone. The bottom compression zone peak value  1003  is 110 mmHg. The bottom compression zone lower value  1004  is 90 mmHg. The middle compression zone peak value  1005  is 90 mmHg. The middle compression zone lower value  1006  is 70 mmHg. The top compression zone peak value  1007  is 70 mmHg. The top compression zone lower value  1008  is 50 mmHg. Each mini-cycle  1015  lasts 8 seconds. The compression period  1010  lasts 40 seconds and the relaxation period  1020  lasts 10 seconds. 
     In the embodiment shown in  FIG. 8 c   , the compression in the middle compression zone starts 15 seconds after compression in the bottom compression zone. Compression in the top compression zone starts 27 seconds after compression in the bottom zone. The bottom compression zone peak value  1003  is 90 mmHg. The bottom compression zone lower value  1004  is 70 mmHg. The middle compression zone peak value  1005  is 70 mmHg. The middle compression zone lower value  1006  is 50 mmHg. The top compression zone peak value  1007  is 50 mmHg. The top compression zone lower value  1008  is 40 mmHg. Each mini-cycle  1015  lasts 12 seconds. The compression period  1010  lasts 60 seconds and the relaxation period  1020  lasts 10 seconds. 
     In the embodiment shown in  FIG. 8 d   , the compression in the middle compression zone starts 10 seconds after compression in the bottom compression zone. Compression in the top compression zone starts 18 seconds after compression in the bottom zone. The bottom compression zone peak value  1003  is 90 mmHg. The bottom compression zone lower value  1004  is 70 mmHg. The middle compression zone peak value  1005  is 70 mmHg. The middle compression zone lower value  1006  is 50 mmHg. The top compression zone peak value  1007  is 50 mmHg. The top compression zone lower value  1008  is 40 mmHg. Each mini-cycle  1015  lasts 8 seconds. The compression period  1010  lasts 40 seconds and the relaxation period  1020  lasts 10 seconds. 
     In the embodiment shown in  FIG. 8 e   , the compression in the middle compression zone starts 15 seconds after compression in the bottom compression zone. Compression in the top compression zone starts 27 seconds after compression in the bottom zone. The bottom compression zone peak value  1003  is 70 mmHg. The bottom compression zone lower value  1004  is 50 mmHg. The middle compression zone peak value  1005  is 50 mmHg. The middle compression zone lower value  1006  is 40 mmHg. The top compression zone peak value  1007  is 40 mmHg. The top compression zone lower value  1008  is 30 mmHg. Each mini-cycle  1015  lasts 12 seconds. The compression period  1010  lasts 60 seconds and the relaxation period  1020  lasts 10 seconds. 
     In the embodiment shown in  FIG. 8 f   , the compression in the middle compression zone starts 10 seconds after compression in the bottom compression zone. Compression in the top compression zone starts 18 seconds after compression in the bottom zone. The bottom compression zone peak value  1003  is 70 mmHg. The bottom compression zone lower value  1004  is 50 mmHg. The middle compression zone peak value  1005  is 50 mmHg. The middle compression zone lower value  1006  is 40 mmHg. The top compression zone peak value  1007  is 40 mmHg. The top compression zone lower value  1008  is 30 mmHg. Each mini-cycle  1015  lasts 8 seconds. The compression period  1010  lasts 40 seconds and the relaxation period  1020  lasts 10 seconds. 
     In addition to the embodiments described above, modifications to the values are possible, the compression pressure may take any values in the range 20 mmHg to 200 mmHg. The compression periods may last for between 5 seconds and 5 minutes. The relaxation periods may last for between 5 seconds and 60 seconds. The overall therapy time may last between 5 minutes and 2 hours. 
     As described above, in the compression patterns, graduated compression is applied to the different compression zones. The compression patterns may be applied to different parts of the limb and the patterns may be applied to either the arms or legs of a subject. It is noted that there is a pressure gradient in the patterns from a distal part of the limb to a proximal part of the limb. This graduated pressure improves venous return. It is noted that in addition to enhancing blood circulation, the compression devices and compression patterns described herein may also enhance lymph flow in a limb of a subject. 
     In addition, the compression patterns may be beneficial for subjects such as athletes when recovering. This is because the external pressure reduces intramuscular space available for swelling and promotes the stable alignment of muscle fibers. This reduces the inflammatory response and muscle soreness. This is beneficial in improving psychological aspects of recovery and may have potential benefits for injury prevention and management. 
     Usage of active compression has been rapidly increasing due to its added benefits compared to static compression. 
     Static compression which is mostly provided through compression socks reduces valve distension which in turn improves blood flow. Degradation of valves (which causes valve distension) results in venous insufficiency and possibly other conditions such as varicose veins as the blood flow to the heart is reduced due to reflux. 
     However, static compression assists the user mostly when he/she is mobile as calf muscle pump is inactive when seated. 
     Added advantage of active compression is that it mimics the calf muscle pump and supports the user even when he/she is seated. Active compression empties lower compartments of the leg preventing blood pooling which in turn increases venous flow towards the heart. 
     Given the fact that static and active compressions serve two different purposes it is evident that having both components in a compression therapy device is an advantage, thus in some embodiments, the compression devices and compression patterns described above are used in conjunction with a compression sock. 
     The inner compression sock would hold the valves conjointly whilst the outer active layer sequentially compresses the calf muscle and empties the veins. 
     The following studies were conducted for the compression pattern described above with reference to  FIGS. 7 a    to  7   f.    
       FIGS. 9 a  to 9 d    show results of a study done to evaluate the benefit of using a compression device according to an embodiment of the present invention on a group of athletes. A group of subjects (3 males and 3 females) between the age of 19-40 years with no vasoactive or glycemic-control related medications were chosen for this randomized trial. A sub-group of participants (3 subjects) were treated with active compression and the other group was used as the control (with passive rest). 
     Following parameters were assessed using the respective techniques. The calf circumference was measured using a tape, Femoral arterial blood flow was quantified using a 5-12 MHz multi-frequency linear phase array ultrasound transducer (SonoScape S2, SonoScape Medical Corp, Shenzhen, China), pressure-to-pain threshold (PPT) of the calf was measured using an algometer (to assess muscle soreness) and static vertical jump and countermovement jump tests was performed to assess the improvement in performance. 
     Following the baseline measurements of the above parameters the participants completed 10 sets of 10 drop jumps from a 0.43 m high box with 10 sec rest between repeats and 1-min rest between sets. Immediately following exercise, muscle soreness was again measured and half of the participants were then treated for 30-min via the active compression device. At 15-min of treatment, femoral artery blood flow was measured. After treatment, all baseline measurements were repeated. 
       FIG. 9 a    shows the difference in calf circumference pre-treatment and post-treatment for subjects using active compression. Following the above intense workout protocol and respective treatments, the change in circumference of the calf tended to be smaller with active compression treatment compared to control. On average active compression reduced calf circumference by 0.6 cm, compared to the control group in which the reduction was 0.37 cm. In the treated group, pre-treatment calf circumferences of Subject 1, Subject 2 and Subject 3 were 37.75 cm, 36.55 cm and 35.6 cm, respectively. Following treatment the respective calf circumferences reduced to 36.5 cm, 36.35 cm and 35.25 cm 
       FIG. 9 b    shows the difference in femoral arterial blood flow for the group of subjects treated with the compression device and the control group. Femoral artery blood flow was increased relative to baseline during treatment with active compression device and decreased during time-control (Active compression treated: 44.3 mL/min; control group: −35.0 mL/min). 
       FIG. 9 c    shows the difference in counter-movement jump height for the subjects treated with the compression device and the control group. Compared to baseline, there was a reduction in counter-movement jump performance for both groups. For the control group this was 3.4 cm. However, this reduction was 1.7 cm in the group treated with active compression. Thus, active compression treatment resulted in 50% improvement in performance compared to the control group. 
       FIG. 9 d    shows an indication of soreness for for the subjects treated with the compression device and the control group. Compared to baseline measurements, the active compression treatment was associated with marked reduction in calf soreness following the intense workout protocol and treatment. Active compression: −7.4 N, Control: 24.1 N. It is noted that a decrease in the pressure to pain threshold (PPT) indicates more soreness as less pressure needs to be applied before pain is felt by the participant. 
     This study has shown that the said active compression technology appears to mitigate calf swelling which occurs due to intense workout procedures, which in this study was mimicked by 100 jumps. Active compression increases blood flow during the treatment and thereby improves performance. The said active compression technology is associated with marked reduction in calf muscle soreness which occurs due to tiring activities. 
       FIGS. 10 a  and 10 b    show results of a study done to evaluate the benefit of using a compression device according to an embodiment of the present invention on a group of subjects who were seated for a long period. A group of subjects (1 male and 2 females) between the age of 19-40 years with no vasoactive or glycemic-control related medications were chosen for this crossover trial. Each participant completed 2 protocols (i.e., two conditions). Treatment modalities included active compression and control (i.e., passive rest). The subjects had to report to the trial site on two separate, adjacent days. 
     Following parameters were assessed using the respective techniques. Calf circumference was measured using a measuring tape and femoral arterial blood flow was quantified using a 5-12 MHz multi-frequency linear phase array ultrasound transducer (SonoScape S2, SonoScape Medical Corp, Shenzhen, China). 
     The baseline of above measurements was acquired after which the subjects were asked to sit for a prolonged period of time to represent the long distance traveller&#39;s condition—upright sitting in a chair with hips and knees at a 90 degree angle for 2 hrs. 
     The subjects were randomly assigned to either active compression or passive rest on Day 1 (Active compression—continuous cycles of 20-min on, 10-min off during their sitting period). The subjects assigned to active compression on Day 1 received passive rest on Day 2 and vice versa. 
       FIG. 10 a    shows the difference in calf circumference pre-treatment and post-treatment for subjects using active compression. As a result of sitting quietly for 2-h, calf circumference increased by 0.57 cm from the baseline measurements when the subjects were not exposed to active compression. When the subjects were treated with Active compression (continuous cycles of 20-min on, 10-min off) for 2-h, calf circumference decreased by 1.11 cm. Pre-treatment calf circumferences of Subject 1, Subject 2 and Subject 3 were 37.15 cm, 37.65 cm and 41.4 cm, respectively. Following treatment the respective calf circumferences reduced to 36.25 cm, 36.35 cm and 40.25 cm 
       FIG. 10 b    shows the difference in femoral arterial blood flow for the group of subjects treated with the compression device and the control group. Compared to baseline measurements, femoral artery blood flow was decreased by 28.3 mL/min at 2-h of sitting, when the subjects were not exposed to active compression. However, when the subjects were treated with Active compression (continuous cycles of 20-min on, 10-min off) for 2-h, femoral artery blood flow was decreased only by 10.1 mL/min at 2-h of sitting. 
     These experiments confirmed the said active compression technology appears to prevent calf swelling which occurs due to long-term sitting and it also acts to mitigate decrease in blood flow. 
       FIG. 11  schematically shows a pneumatic compression device according to an embodiment of the invention. The pneumatic compression device  1100  comprises three inflatable bladders: a top inflatable bladder  1102 , a middle inflatable bladder  1104  and a bottom inflatable bladder  1106 . As shown in  FIG. 11 , the three inflatable bladders are arranged to apply compression to top, middle and bottom compression zones respectively of a calf of a wear&#39;s leg  1108 . 
     A top compression zone pump  1112  is connected to the top inflatable bladder  1102  via a top compression zone valve  1122 . A middle compression zone pump  1114  is connected to the middle inflatable bladder  1104  via a middle compression zone valve  1124 . A bottom compression zone pump  1116  is connected to the bottom inflatable bladder  1106  via a bottom compression zone valve  1126 . The respective inflatable bladders, valves and pumps are connected by tubing. A top compression zone pressure sensor  1132  is connected to the tubing between the top inflatable bladder  1102  and the top compression zone valve  1122 . A middle compression zone pressure sensor  1134  is connected to the tubing between the middle inflatable bladder  1104  and the middle compression zone valve  1124 . A bottom compression zone pressure sensor  1136  is connected to the tubing between the bottom inflatable bladder  1106  and the bottom compression zone valve  1126 . 
     A microcontroller  1140  is coupled to driver circuits  1142  which allow individual control of the top compression zone pump  1112 , the middle compression zone pump  1114  and the bottom compression zone pump  1116 , and individual control of the top compression zone valve  1122 , the middle compression zone valve  1124  and the bottom compression zone valve  1126 . The microcontroller  1140  is coupled to the A top compression zone pressure sensor  1132 , the middle compression zone pressure sensor  1134  and the bottom compression zone pressure sensor  1136 . 
     A set of three push buttons  1144  allow user input of commands into the pneumatic compression device  1100 . A set of 6 RGB (red, green, blue) light emitting diodes (LEDs)  1146  display information about the selected mode of the pneumatic compression device  1100 . Power is supplied to the pneumatic compression device  1100  by a battery  1150 . 
     In use, the pumps are controlled by the microcontroller  1140  to inflate respective individual inflatable bladders according to a compression pattern such as those described above with reference to  FIGS. 7 a - f  and 8 a - f   . The pressure sensors provide feedback to the microcontroller  1140  so that the inflatable bladders can individually be inflated to a required pressure. In order to hold individual inflatable bladders at a desired pressure, the corresponding valve is closed. To release the pressure in one of the inflatable bladders, the corresponding valve is opened with allows air to flow out of the bladder and through the corresponding pump. 
       FIGS. 12 a  to 12 f    show a pneumatic compression device according to an embodiment of the present invention.  FIG. 12 a    is a front view of the pneumatic compression device in a closed configuration.  FIG. 12 b    is a front view of an actuator portion of the pneumatic compression device.  FIG. 12 c    is s front view of the pneumatic compression device in an open configuration.  FIG. 12 d    is a rear view of the pneumatic compression device in a closed configuration.  FIG. 12 e    is a rear view of the actuator portion of the pneumatic compression device.  FIG. 12 f    is a rear view of the pneumatic compression device in an open configuration. 
     As shown in  FIGS. 12 a  to 12 f   , the pneumatic compression device  1200  comprises flexible portion or active layer  1210  which is in the form of a sleeve that is wrapped around lower leg of the user, and an actuator portion  1250  which is accommodated in a pocket in the front of the body portion  1210 . When the compression device  1200  is worn, the actuator portion  1250  is located over the shin of the wear. The actuator portion  1250  has six LEDs  1252  which correspond to LEDs  1146  shown in  FIG. 11  located at the top end. Below the LEDs  1252  are three control buttons: a power on/off button  1254 ; a compression intensity selection button  1256  and a compression pattern selection button  1258  which correspond to the push buttons  1144  shown in  FIG. 11 . 
     The active layer  1210  comprises an upper fastening portion  1222  and a lower fastening portion  1224  and an upper fastening tab  1126  on one side and a lower fastening tab  1128  on the other side. The upper fastening portion  1222 , the lower fastening portion  1124 , the upper fastening tab  1226  and the lower fastening tab  1128  comprise a fastening surface such as Velcro which allow the pneumatic compression garment to be fastened around the lower leg of the wearer. 
     The active layer  1210  comprises a pocket  1230  into which the actuator portion  1250  is inserted. The top of the pocket  1230  has labels corresponding to the control buttons of the actuator portion  1250 . 
       FIG. 13  shows the internal configuration of an actuator portion of a pneumatic compression device according to an embodiment of the present invention.  FIG. 13  is a view from the back of the actuator portion  1250  with the back cover (which faces the shin of the wearer when the actuator device is in use) removed. 
     As shown in  FIG. 13 , a first printed circuit board (PCB)  1260  is located at the top of the actuator portion  1250 . Six LEDs  1252  and three buttons  1266  are arranged on the PCB  1260 . At the side of the PCB  1260  an infrared communication module  1262  and a universal serial bus (USB) charging port  1264  are mounted. It is noted that the infrared communication module  1262  is located on the left hand side of the actuator portion  1250  as shown in  FIG. 13 . When two compression devices are used together with one on each leg of a wearer, the infrared communication modules of the two compression devices are arranged to face one another. Thus, the actuator portion  1250  shown in  FIG. 13  corresponds to a right leg compression device and a corresponding left leg compression device would have the infrared communication module arranged at the opposite side. 
     The battery  1150  is located below the first PCB  1260 . The top compression zone pump  1112  and the top compression zone valve  1122  are located laterally from the battery  1150 . A top compression zone tube connector  1272  is connects to tubing from the top compression zone pump  1112 . A second PCB  1268  is located below the battery  1150  and comprises circuitry associated with the pressure sensors. The middle compression zone pump  1114  and the middle compression zone valve are located laterally from the second PCB  1268 . A middle compression zone connector  1274  connects to tubing from the middle compression zone pump  1114 . The bottom compression zone pump  1116  and the bottom compression zone valve  1126  are located below the middle compression zone pump  1114 . A bottom compression zone connector  1276  connects to tubing from the bottom compression zone pump  1116 . 
       FIG. 14  shows an inflatable bladder component within a pneumatic compression device according to an embodiment of the present invention. The inflatable bladder component  1400  is located within a pocket in the active layer  1210  of the pneumatic compression device. The inflatable bladder component  1400  comprises three inflatable bladders: a top inflatable bladder  1410 , a middle inflatable bladder  1420  and a bottom inflatable bladder  1430 . The top inflatable bladder  1410  has a top bladder port  1412  which is connected to a top bladder connecting tube  1414 . The top bladder connecting tube  1414  connects the top inflatable bladder  1410  to the top compression zone tube connector  1272  of the actuator module  1250 . The middle inflatable bladder  1420  has a middle bladder port  1422  which is connected to a middle bladder connecting tube  1424 . The middle bladder connecting tube  1424  connects the middle inflatable bladder  1420  to the middle compression zone connector  1274  of the actuator module  1250 . The bottom inflatable bladder  1430  has a bottom bladder port  1432  which is connected to a bottom bladder connecting tube  1434 . The bottom bladder connecting tube  1432  connects the bottom inflatable bladder  1430  to the bottom compression zone connector  1276  of the actuator module  1250 . 
     When the compression device  1200  is worn, the three inflatable bladders are arranged against calf muscle of the wearer. By inflating the inflatable bladders, compression patterns can be applied to the wearer&#39;s calf. 
       FIG. 15  shows an inflatable bladder module of a compression device according to an embodiment of the present invention. The inflatable bladder module  1500  is formed from two membranes formed from sheets of Thermoplastic polyurethane (TPU) which are bonded together along bonding lines. For example, heat bonding may be used to bond the two sheets together. The top inflatable bladder  1510 , the middle inflatable bladder  1520  and the bottom inflatable bladder  1530  are formed by an exterior boundary  1540  which is formed from a bond that runs around the circumference of the inflatable bladder module  1500 . Two internal boundaries  1542  separate the top inflatable bladder  1510  from the middle inflatable bladder  1520 , and the middle inflatable bladder  1520  from the bottom inflatable bladder  1530 , respectively. In this embodiment, the internal boundaries  1542  are substantially straight and run in a horizontal direction. 
     The top bladder port  1512 , the middle bladder port  1522  and the bottom bladder port  1532  located close to the exterior boundary  1540  in the respective inflatable bladders. 
     As shown in  FIG. 15 , a plurality of baffles  1544  are located within each of the inflatable bladders. The baffles  1544  are formed as bonds between the membranes that form the inflatable bladder module  1500 . The baffles  1544  run in a vertical direction which is along the axis of the leg of the wearer of the compression device. The baffles  1544  form a set of parallel lines with breaks that are offset on neighboring baffles. 
     The baffles  1544  prevent the inflatable bladders from bulging excessively. The arrangement of baffles in the vertical direction allows the bladder component  1500  to bend around the leg of the wearer. 
     In some embodiments, a pair of compression devices are each provided with a wireless communication module to allow synchronization of compression patterns applied to each leg of a wearer. 
       FIG. 16  shows a pair of compression devices which are provided with infrared communication modules according to an embodiment of the present invention. As shown in  FIG. 16 , a first compression device  1710  comprises a first infrared communication module  1712  and a second compression device  1720  comprises a second infrared communication module  1722 . 
     In this example embodiment, the first compression device is configured as a master device and the second compression device is configured as a slave device. The master compression device comprises three buttons: a power on/off button, an intensity selection button and a mode selection button. In this example, there are two possible modes which may be selected and three possible intensities for each mode. Table 1 below shows the signals generated by the infrared communication module  1712  of the master device (the first compression device  1710 ) and the synchronization carried out by the slave device (the second compression device  1720 ) in response to receiving an infrared signal at the second infrared communication module  1722 . 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Signal Generated 
                   
               
               
                 Button Pressed 
                 by Master 
                 Synchronization by Slave 
               
               
                 in Master Device 
                 through IR 
                 Device 
               
               
                   
               
             
            
               
                 Power On 
                 0 
                 The slave restarts the default 
               
               
                   
                   
                 therapy &amp; intensity as soon as it 
               
               
                   
                   
                 receives a “0” through IR. 
               
               
                   
                   
                 This action syncs the compression 
               
               
                   
                   
                 pattern with Master. 
               
               
                 Resume (Power 
                 1 
                 The slave resumes to therapy as 
               
               
                 Button- Short 
                   
                 soon as it receives a “1” through 
               
               
                 Press) 
                   
                 IR 
               
               
                 Pause (Power 
                 2 
                 The slave pauses the therapy as 
               
               
                 Button- Short 
                   
                 soon as it receives a “2” through 
               
               
                 Press) 
                   
                 IR 
               
               
                 Mode (choose 
                 3 
                 The slave begins the compression 
               
               
                 Mode 1 when 
                   
                 therapy in Mode 1 &amp; Intensity 1 as 
               
               
                 Intensity 1) 
                   
                 soon as it receives a “3” through 
               
               
                   
                   
                 IR 
               
               
                 Mode (choose 
                 4 
                 The slave begins the compression 
               
               
                 Mode 1 when 
                   
                 therapy in Mode 1 &amp; Intensity 2 as 
               
               
                 Intensity 2) 
                   
                 soon as it receives a “4” through 
               
               
                   
                   
                 IR 
               
               
                 Mode (choose 
                 5 
                 The slave begins the compression 
               
               
                 Mode 1 when 
                   
                 therapy in Mode 1 &amp; Intensity 3 as 
               
               
                 Intensity 3) 
                   
                 soon as it receives a “5” through 
               
               
                   
                   
                 IR 
               
               
                 Mode (choose 
                 6 
                 The slave begins the compression 
               
               
                 Mode 2 when 
                   
                 therapy in Mode 2 &amp; Intensity 1 as 
               
               
                 Intensity 1) 
                   
                 soon as it receives a “6” through 
               
               
                   
                   
                 IR 
               
               
                 Mode (choose 
                 7 
                 The slave begins the compression 
               
               
                 Mode 2 when 
                   
                 therapy in Mode 2 &amp; Intensity 2 as 
               
               
                 Intensity 2) 
                   
                 soon as it receives a “7” through 
               
               
                   
                   
                 IR 
               
               
                 Mode (choose 
                 8 
                 The slave begins the compression 
               
               
                 Mode 2 when 
                   
                 therapy in Mode 2 &amp; Intensity 3 as 
               
               
                 Intensity 3) 
                   
                 soon as it receives a “8” through 
               
               
                   
                   
                 IR 
               
               
                 Power off 
                 9 
                 The slave will power off as soon as 
               
               
                   
                   
                 it receives a “9” through IR 
               
               
                   
               
            
           
         
       
     
     As shown in table 1 above, in response to an input on the master device, the slave device will perform a corresponding action following receipt of an infrared signal. 
       FIG. 17  shows a pair of compression devices which are provided with wireless communication modules. As shown in  FIG. 17 , the first compression device  1810  comprises a first wireless transceiver  1812  and the second compression device  1820  comprises a second wireless transceiver  1822 . The first and second wireless transceivers may be Bluetooth low energy (BLE) transceivers. 
     In this embodiment the two compression devices communicate with each other using Bluetooth Low Energy (BLE) communication technology to ensure the compression sequence in both devices are time, pattern &amp; intensity synchronized. Each device in a pair has a BLE transceiver unit which can send and receive BLE signals which contains mode, intensity, pause, resume related data encoded in it. The data in BLE signal is decoded by the receiving unit and processed to implement synchronization between the sending device and receiving device. 
     The first compression device  1810  is configured as a Master and the second communication device  1820  is configured as a Slave. Both the devices (Master &amp; Slave) must be powered on independently. Once the devices are powered on, the user can select the Mode and/or intensity by pressing Mode &amp; Intensity buttons on the master device. The BLE transceiver inside the Master device will transmit a data packet to the Slave device when one of the User Interface buttons (Mode, Intensity &amp; Pause) are pressed. The data packet will include information about the Mode, Intensity selected in the Master device. The Slave device will receive the data packet instantaneously and will use the information in the data packet to set the Mode and Intensity of the Slave device—this way, both the devices will be time, mode &amp; intensity synched. 
     The Master device and Slave device doesn&#39;t need to aligned to face each other for successful communication between them. They both have to within a range of 5 m to have successful communication and they have to be “paired” prior to successful communication. This pairing will done at factory during mass production. 
     The table shows the BLE signals sent by Master Device to the Slave device based on button press. When these BLE signals are received by the Slave, it will choose a state (Pause, Resume, Mode, Intensity, Power-off) from the pre-programmed look-up table based on the received BLE signal ( 1 ,  2 ,  3  . . .  9 ) from the Master. 
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Signal Generated 
                   
               
               
                 Button Pressed 
                 by Master 
                 Synchronization by Slave 
               
               
                 in Master Device 
                 through BLE 
                 Device 
               
               
                   
               
             
            
               
                 Power On 
                 0 
                 The slave restarts the default 
               
               
                   
                   
                 therapy &amp; intensity as soon as it 
               
               
                   
                   
                 receives a “0” through BLE. 
               
               
                   
                   
                 This action syncs the compression 
               
               
                   
                   
                 pattern with Master. 
               
               
                 Resume (Power 
                 1 
                 The slave resumes to therapy as 
               
               
                 Button- Short 
                   
                 soon as it receives a “1” through 
               
               
                 Press) 
                   
                 BLE 
               
               
                 Pause (Power 
                 2 
                 The slave pauses the therapy as 
               
               
                 Button- Short 
                   
                 soon as it receives a “2” through 
               
               
                 Press) 
                   
                 BLE 
               
               
                 Mode (choose 
                 3 
                 The slave begins the compression 
               
               
                 Mode 1 when 
                   
                 therapy in Mode 1 &amp; Intensity 1 as 
               
               
                 Intensity 1) 
                   
                 soon as it receives a “3” through 
               
               
                   
                   
                 BLE 
               
               
                 Mode (choose 
                 4 
                 The slave begins the compression 
               
               
                 Mode 1 when 
                   
                 therapy in Mode 1 &amp; Intensity 2 as 
               
               
                 Intensity 2) 
                   
                 soon as it receives a “4” through 
               
               
                   
                   
                 BLE 
               
               
                 Mode (choose 
                 5 
                 The slave begins the compression 
               
               
                 Mode 1 when 
                   
                 therapy in Mode 1 &amp; Intensity 3 as 
               
               
                 Intensity 3) 
                   
                 soon as it receives a “5” through 
               
               
                   
                   
                 BLE 
               
               
                 Mode (choose 
                 6 
                 The slave begins the compression 
               
               
                 Mode 2 when 
                   
                 therapy in Mode 2 &amp; Intensity 1 as 
               
               
                 Intensity 1) 
                   
                 soon as it receives a “6” through 
               
               
                   
                   
                 BLE 
               
               
                 Mode (choose 
                 7 
                 The slave begins the compression 
               
               
                 Mode 2 when 
                   
                 therapy in Mode 2 &amp; Intensity 2 as 
               
               
                 Intensity 2) 
                   
                 soon as it receives a “7” through 
               
               
                   
                   
                 BLE 
               
               
                 Mode (choose 
                 8 
                 The slave begins the compression 
               
               
                 Mode 2 when 
                   
                 therapy in Mode 2 &amp; Intensity 3 as 
               
               
                 Intensity 3) 
                   
                 soon as it receives a “8” through 
               
               
                   
                   
                 BLE 
               
               
                 Power off 
                 9 
                 The slave will power off as soon as 
               
               
                   
                   
                 it receives a “9” through BLE 
               
               
                   
               
            
           
         
       
     
     Whilst the foregoing description has described exemplary embodiments, it will be understood by those skilled in the art that many variations of the embodiments can be made within the scope and spirit of the present invention.