Compression device, particularly for preventing deep vein thrombosis

Abstract

A compression device particularly suited for DVT prophylaxis includes a disposable wrap and a reusable controller that is removably attached to the wrap to apply tension to the wrap as it encircles a patient's limb. The wrap includes a strap that wraps around a pulley driven by an electric motor; during operation, an encoder determines the amount of pulley rotation and a current sensor determines the current load on the motor. A pretensioning protocol sets the wrap's pulley to the appropriate slack-tightening position, allowing the wrap to properly perform the DVT prophylaxis protocol.

Description

[Background technology]

[0001] The human circulatory system includes arteries, which carry oxygen-rich blood throughout the body. Veins are blood vessels that return oxygen-poor blood and waste products to the heart for regeneration through the lungs and liver. Veins have tiny valves that keep blood moving back toward the heart, rather than collecting at the end.

[0002] Deep vein thrombosis (DVT) occurs when a blood clot forms in one or more of the body's deep veins or when one or more of the vein's valves are compromised by a blood clot. DVT can result from certain medical conditions that affect the formation of a blood clot or affect blood flow, typically in the extremities, such as the legs. DVT can be serious because the blood clot can break away, travel with the bloodstream, and lodge in another location, blocking blood flow to the body at that location.

[0003] DVT can occur when a person's legs remain motionless for an extended period of time because the leg muscles are not contracting to help circulate blood. DVT often occurs during or as a result of surgery. A DVT condition has been known to occur after a patient has been on the operating table for as little as 20 minutes. The risk of DVT increases during prolonged recovery times after surgery, when patients may spend most of each day in bed. The treatment of choice to reduce the risk of blood clots and DVT is to have patients up and walking as soon as possible after surgery.

[0004] Another preferred treatment, usually in addition to walking, is the use of a compression device, which is wrapped around the extremities, usually the lower legs. The compression device intermittently compresses the limb, encouraging blood flow through the veins and back to the heart. The cyclical compression can also encourage the body's natural release of substances that help prevent blood clots. A typical DVT compression device is a pneumatic device that applies pressure to the affected limb by pumping air into a hollow cuff that surrounds the limb. The pressure compresses the veins, forcing blood from the veins toward the heart. The pressure is relieved by puncturing the cuff to allow the air to escape. This inflation-deflation cycle continues as long as the cuff is worn by the patient.

[0005] Patient compliance is necessary to avoid DVT, which means that the patient wears an active DVT cuff for a predetermined amount of time and leaves the hospital bed to walk for a predetermined period of time. However, patient compliance is often a major problem. One problem is that wearing a DVT cuff for extended periods of time can be uncomfortable, yet the recommendation to avoid DVT can exceed 18 hours per day. Some DVT cuffs include a means for monitoring the time the cuff has been activated and performed its pressure cycles. However, some patients, especially those prescribed DVT cuffs for home treatment, find ways to "trick" the DVT cuff by attaching it to a solid object and inflating and deflating it over an inanimate object.

[0006] Another problem is that DVT cuffs do not contribute to patient mobility. Typical DVT cuffs require a source of compressed air to inflate the cuff during pressure cycles. Early systems used a large pump unit located on the floor next to the patient's bed. Later, smaller pumps that could be carried by the patient were developed. However, many patients, especially elderly patients, lack the strength and / or endurance to carry an air pump connected to a DVT cuff attached to the patient's leg. Furthermore, the air hose between the pump and the cuff can become tangled and uncomfortable.

[0007] There is a need for a maneuverable compression device that is particularly suitable for DVT prevention, and that can ensure patient compliance, or at least ensure that non-compliant patients cannot "trick" themselves into thinking that the DVT cuff is being used properly. Summary of the Invention

[0008] The compression device includes a disposable wrap configured to be wrapped around a patient's limb and a reusable controller removably attached to the disposable wrap. The controller is a non-pneumatic device that operates to contract the wrap around the patient's limb in a controlled manner and according to a predetermined compression protocol. In one configuration, the compression protocol is adapted for deep vein thrombosis prophylaxis, although other compression protocols are possible.

[0009] In one configuration, the controller includes a DC motor and a gearbox that reduces the motor's rotational output speed to a speed appropriate for use in retracting the wrap. The wrap is connected at its looped end to a D-ring that is connected to a pull strap, and the pull strap is attached to a pulley that is rotated by the motor to at least partially wrap the pull strap around the pulley. The opposite end of the wrap includes a controller mounting portion that allows for removable attachment or installation of a controller to the wrap. In one embodiment, the controller mounting structure includes a load cell at the interface between the wrap and the controller and is configured to measure the tension created when the wrap is tightened around the patient's limb. In one specific embodiment, the controller mounting structure uses a load cell axle that engages within a pair of clips affixed to the wrap. In another specific embodiment, a keyed hinge structure is provided between the wrap and the controller housing. The controller mounting structure is configured to allow the controller to be removed from the wrap and replaced with a different controller, if necessary.

[0010] The controller can include an accelerometer or position sensor for sensing the patient's physical position and movement. Data from the accelerometer or position sensor is provided to an on-board digital processor, such as a microprocessor, which generates compliance data that can be uploaded to or displayed on a display screen of the compression device.

[0011] In another configuration, the wrap is provided with an RF chip or tag that can be specifically associated with a patient. The controller contains RF sensing circuitry that detects the RF chip and reads information from the chip, including a unique identifier. Before the controller can operate, a concordance between the unique identifier on the chip and a database of known valid identifiers maintained in the controller is required. Regardless of which controller is attached to the wrap, the unique identifier associated with the wrap, and therefore the patient, follows the wrap. This feature allows the same wrap to be recognized when the patient moves from one hospital unit to another.

[0012] The compression device of the present disclosure is a non-pneumatic wearable device that allows for patient mobility. Thus, the patient is not confined to a hospital bed or chair during the compression protocol. Additionally, the controller's sensors and microprocessor are configured to monitor the amount of time the patient spends lying / reclining, sitting / standing, or moving while wearing the device. The controller displays information indicating the type of activity while wearing the device.

[0013] In another aspect of the present disclosure, the non-pneumatic mobile compression device disclosed herein is configured to apply a compression profile that reduces the risk of DVT. Specifically, the device's controller is configured to apply compression to the patient's limb / leg to achieve a blood flow rate known to reduce or eliminate the risk of DVT. The application operates to produce a blood flow rate approximately three times greater than the patient's baseline rate.

[0014] In a further feature of the compression device, the processor determines a patient-specific Body Compression Index (BCI), which corresponds to the range of movement of the wrap or pull strap between a predetermined pre-tension and the maximum compressive force applied to the patient during the compression protocol. The BCI ensures consistent application of minimum and maximum compressive forces regardless of any physiological changes in the patient, such as limb swelling.

[0015] In another feature of the present disclosure, a Mobility Health Index (MHI) number is calculated as a function of data indicative of the patient's compliance with the patient's recovery protocol. The data can include the length of time the compression device was worn and operated in DVT prevention mode, the amount of time spent sitting or lying down, and the amount of walking the patient undertakes. The MHI provides a direct measure of how the patient is progressing toward recovery goals established by a medical professional. The MHI can be displayed on the compression device worn by the patient and on a separate display used by the medical professional for quick access to the patient's progress. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view of a compression device according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is another perspective view of the compression device shown in FIG. [Figure 3] FIG. 3 is a partially exploded perspective view of the compression device shown in FIG. [Figure 4] 4 is another partially exploded perspective view of the compression device shown in FIG. 3. FIG. [Figure 5] Figure 5 is an enlarged view of the load cell attachment to the compression device shown in Figures 1-4. [Figure 6] 6 is a perspective view of the disposable wrap of the compression device shown in FIG. 1. [Figure 7] FIG. 7 is a perspective view of a disposable wrap of a compression device according to another embodiment of the present disclosure. [Figure 8A] FIG. 8 is a perspective view of a controller for use with the disposable wrap shown in FIG. [Figure 8B] FIG. 8a is an enlarged partial cross-sectional view of the interface keyed hinge shown in FIG. [Figure 9] FIG. 9 is a front view of a kiosk for storing and securing the compaction device shown in FIGS. 1-7. [Figure 10A] 10A-10C are screen shots of the displays provided by the compressor of FIGS. 1-7. [Figure 10B] 10A-10C are screen shots of the displays provided by the compressor of FIGS. 1-7. [Figure 10C] 10A-10C are screen shots of the displays provided by the compressor of FIGS. 1-7. [Figure 10D] FIG. 10D is a display device that displays a summary of the information displayed by the compressor. [Figure 11A] FIG. 11A is a graph showing blood flow velocity in the femoral vein during a compression cycle using the compression device shown in FIGS. 1-7 for DVT prophylaxis. [Figure 11B] FIG. 11B is a graph of an ideal force profile to produce the blood flow velocity profile shown in FIG. 11A. [Figure 11C] FIG. 11C is a graph of the actual force profile of the compression device shown in FIGS. 1-7 that produced the blood flow velocity profile shown in FIG. 11A. [Figure 12] FIG. 12 is a flow chart of steps for initializing a controller for the compression device disclosed herein. [Figure 13] FIG. 13 is a flow chart of the steps for initializing a controller for a compression device paired with a kiosk as disclosed herein. [Figure 14] FIG. 14 is a flow chart of the operation of the controller of the compressor disclosed herein in a DVT prevention mode of operation. [Figure 15] FIG. 15 is a flow chart of the controller operation for replacing wraps in the compression device disclosed herein. [Figure 16] FIG. 16 is a flow chart of the display of various operating modes of the controller for the compressor disclosed herein. [Figure 17]FIG. 17 is a flow chart of the controller operation for storage of the compression device disclosed herein. [Figure 18] FIG. 18 is a flow chart of the controller operation for removing the compression device disclosed herein from the patient. [Figure 19] FIG. 19 is a summary of the display screen produced by the kiosk of FIG. [Figure 20] Figure 20 shows details of the drive pulley for the mounting shown in Figures 1-7. [Figure 21] FIG. 21 is a flow chart of the controller operation for creating pretension in the compression device disclosed herein. [Figure 22A] 22A-22B are graphs of pulley movement in relation to Body Compression Index (BCI). [Figure 22B] 22A-22B are graphs of pulley movement in relation to Body Compression Index (BCI). [Figure 23A] FIG. 23A is a graph of the BCI position shift due to swelling in the patient. [Figure 23B] FIG. 23B is a graph of the BCI position shift caused by the compression device being too loose. [Figure 23C] FIG. 23C is a graph of the BCI position shift due to the compression device being overtightened. [Figure 24] FIG. 24 is a flow chart of the controller operation for performing DVT compression. [Figure 25] FIG. 25 is a perspective view of a disposable wrap according to a further embodiment of the present disclosure. [Figure 26] FIG. 26 is a view of the wrap of FIG. 25 engaged with a patient's limb in a first temporary attachment configuration. [Figure 27] 27 is a view of the wrap of FIG. 26 with the controller of FIG. 8 attached and engaged with a patient's limb in a second attachment position. [Figure 28]FIG. 28 is a flow chart of the controller operation for booting up a laptop as disclosed herein. [Figure 29] FIG. 29 is a flow chart of the controller operation for establishing a slack-tightening position for a wrap as disclosed herein. [Figure 30] FIG. 30 is a flow chart of the controller operation for creating pretension in the wraps disclosed herein prior to use in DVT prophylaxis. [Figure 31] FIG. 31 is a diagram of the encoder pulse count during the operation of the wrap in the pretensioning operation of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] For the purposes of promoting an understanding of the principles of this disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following specification. It will be understood that no limitation on the scope of this disclosure is therefore intended. It will be further understood that this disclosure includes all alterations and modifications of the illustrated embodiments as would normally occur to one skilled in the art to which this disclosure pertains, and includes any further applications of the principles disclosed herein.

[0018] The compression device 10 shown in FIGS. 1-6 includes a wrap 12 and a controller 14 attached to the wrap. The wrap 12 is a flexible sheet material configured to be wrapped around a portion of a patient's body. For a DVT cuff, the wrap is specifically sized to be wrapped around a person's lower leg or calf. It has been found that to adequately combat a DVT attack, the wrap should have a width of approximately 4.0 inches (approximately 4.0 x 25.4 mm) to apply a compressive force over a sufficient area of ​​the patient's limb, most specifically the calf. The wrap 12 is preferably formed of a "breathable" material with minimal or no stretch, such as a breathable polyester woven fabric. The "breathability" of the woven fabric is important to avoid overheating of the patient's limb around which the cuff is wrapped. This characteristic makes the wrap more tolerable to patients when worn for extended periods of time. With regard to "stretchability," to maintain proper compression, the wrap should not stretch more than 0.5 inches (0.5 x 25.4 mm) when the compression device is exerting its maximum tension or compression force. The wrap material may also include wicking features to allow perspiration to wick from the skin surface to the exterior of the wrap. A suitable high-tech polyester woven fabric can combine adequate wicking ability with breathability to enhance user comfort.

[0019] The wrap includes a flap 17 that has one end tied to wrap 12. The flap is positioned under controller 14 and is operable to protect the patient's skin from any heat generated by controller 14 or the patient's skin. Flap 17 can be made of the same material as wrap 12 or can be made of a different material adapted to protect the skin from pressure exerted by the controller and / or heat from the controller or the patient's skin. When wrap 12 encircles the limb, flap 17 has a free end under controller 14 so that it does not exert pressure on the limb.

[0020] The controller 14 includes a base plate 42 and a cover 44 that contains the cuff's drive components and electronics. As shown in Figures 3-4, the cover 44 can be secured to the base plate 42 at a number of latches 47, preferably located at the corners of the plate.

[0021] The wrap 12 includes an end loop 24 that is configured to be removably wrapped around a D-ring 22 that is connected to the controller 14. The end loop 24 may include a releasable opposing surface, such as a hook-and-loop or VELCRO®-type fastener, that allows the wrap to pass through the D-ring and overlap itself to form the end loop. It can be appreciated that the releasable opposing surface can have a sufficient length to allow for varying amounts of overlap. This allows the DVT cuff to be comfortably wrapped around a patient's limb regardless of the patient's size.

[0022] As best shown in FIG. 6 , the opposite end of the wrap includes an attachment structure 40, which includes a pair of clips 60 attached to an attachment plate 61. The attachment plate 61 is secured to the end of the wrap 12. As described herein, the wrap is essentially secured to the controller 14 at the attachment structure 40, with the opposite end connected to the D-ring 22, allowing movement when the wrap is fastened. In one important feature of the present disclosure, the wrap 12 is configured to be independent of the controller 14, with features connecting the wrap to the controller. The wrap 12 can therefore be a disposable component. Furthermore, this feature allows the wrap 12 to remain with the patient even when a new controller 14 is provided. In one embodiment, the flap 17 can be configured to releasably engage the end loop 24 of the wrap, particularly the peelable (VELCRO®) facing surface of the loop. Alternatively, the underside of the wrap adjacent the attachment structure 40 can be configured to engage the facing surface of the loop. This feature allows the wrap to be kept on the patient's limb without a controller while waiting for a new controller.

[0023] Clip 60 is configured to removably receive axle 58 and, in one embodiment, can be in the form of or the like of a spring clip that can be resiliently pushed to allow the axle to enter the clip. The clip is sufficiently flexible to allow the axle to be pushed into the clip, yet strong enough to prevent the axle from moving during a compression cycle of cuff 10. As best seen in the enlarged view of FIG. 5, the axle provides a connection to load cell 57. Axle 58 includes a pull bar 30 attached at one end to the axle and at the other end to load cell 57. In one embodiment, the load cell is in the form of a plate supporting strain gauge 57c. One end of load cell plate 57 is secured to base plate 42 at mounting pad 57a, such as by a screw or other suitable fastener. The other end of load cell plate 57 is secured to pull bar 30 at mounting pad 57b. Thus, the load cell 57 serves as a connection interface between the mounting structure 40 at one end of the wrap 12 and the controller 14 .

[0024] 1, the other end of the wrap, including end loop 24, is connected to D-ring 22, which itself is connected to pull strap 20 that passes through slot 46 in housing 44. Strap 20 engages pulley 34 driven by electric motor 32 at mounting portion 35. The motor is secured to base plate 42, thereby closing the loop around the patient's limb. In other words, wrap 12 is removably secured to controller 14 at end loop 24 by D-ring 22, pull strap 20, pulley 34, and motor 32, and the other end of wrap 12 is removably secured to the controller by mounting structure 40 and load cell 57.

[0025] As described above, the load cell 57 provides one connection interface between the controller 14 and the wrap 12 that surrounds the patient's limb. Because the axle 58 is held on the wrap by the clip 60, the axle, and therefore the pull bar 30, is pulled by a circumferential force when the wrap is tightened around the circumference of the patient's limb. This force, in turn, causes the load cell plate 57 to bend because one end of the plate is fixed to the pull bar and the other end is essentially a cantilever attached to the base plate 42 of the controller 14. As the plate bends, a strain gauge 57c attached to the surface of the plate stretches. The strain gauge 57c is connected by wire 57d to the controller electronics, which is configured to interpret the measured strain and convert it into a force value.

[0026] In an alternative embodiment, the load cell 57 is omitted if a direct attachment between the pull bar 30 and the controller 14, and more particularly, the controller base plate 42, is preferred. In that embodiment, the circumferential force exerted by the wrap as it is tightened around the patient's limb can be determined by a sensor associated with the motor. One such sensor can be a current sensor associated with the motor 32, which measures the current through the DC motor. The current required to maintain the motor rotational speed (at a given voltage) is a function of the resistive force from the wrap as it is tightened. The current sensor can be connected to the controller electronics, which is configured to interpret the measured current and convert it into a force value.

[0027] In one feature of the DVT cuff, best seen in FIG. 5 , the controller 14, and particularly the base plate 42, defines a curved surface 45 that faces the patient's limb when the cuff is wrapped around the limb. The curvature of the curved surface is configured so that the surface does not contact the patient's skin, even through the flap 17. Instead, the curvature of the surface 45 serves as a visual and physical guide for properly orienting the DVT cuff 10 on the patient's limb. For example, the controller can be configured to be placed on the ventral side of the lower leg, near the tibia. The curvature of the surface 45 prevents direct pressure on the bone, which can be uncomfortable when the wrap is tightened or loosened around the leg. Instead, compressive pressure is limited to the wrap 12 and the lateral edges of the controller 14 on either side of the tibia. In one particular embodiment, the curved surface 45 can define a radius of at least 1.5 inches (1.5 x 25.4 mm).

[0028] Returning to the drive train of the controller 14, the pulley 34 can be coupled to the motor 32 by a transmission 33, which is configured to reduce the rotational speed and increase the torque of the output driving the pulley. In one particular embodiment, the transmission can be configured to provide a speed reduction of 388:1-488:1. For DVT devices, a specific compression protocol requires a no-load output speed of at least 30 rpm and a torque of at least 310 inch-ounce-force (310 x 0.007 Nm (1 inoz = 0.007 Nm)). The motor specifications and transmission gearbox drive train can be selected to achieve these output characteristics.

[0029] The motor 32 is driven by a control circuit 50, which controls the operation of the motor to reel in and reel out the pull strap 20 relative to the pulley 34. Accordingly, the control circuit includes a digital processor, such as a microprocessor 52, and a motor controller 53. The microprocessor includes one or more stored programs that control the motor controller according to a compression profile and also control the transfer of data to and from the controller 14. The control circuit 50 can include a pulley sensor 54 electrically connected to the microprocessor and configured to determine the position of the pulley as it rotates to reel in and reel out the pull strap 20. A load cell 57 (or a current sensor in an alternative embodiment) is also electrically connected to the microprocessor and configured to provide a measurement of the tension in the wrap 12, which directly correlates to the amount of compression on the patient's limb. Regarding certain features of the DVT cuff 10, the control circuit can also include an accelerometer 55, electrically connected to the microprocessor and operative to provide motion data representative of the patient's position, posture, and movement.

[0030] The cuff 10 includes a visual display 15 on the cover 44, which is also connected to the microprocessor. The display 15 can display information regarding the operation of the cuff and / or indicative of patient compliance with wearing the cuff. In one configuration, the display can be a touch screen device, allowing the medical professional to scroll through various screens displaying various information. The display 15 can be an electronic paper or electronic ink display, which reduces the power requirements to maintain the display. A battery (not shown) is contained within the controller 14, such as in the space between the microprocessor 52 and the base plate 42, and provides power to all electrical components of the control circuit 50. The battery is preferably rechargeable. The controller can include a jack for receiving a cable for connection to a charging station and can also include circuitry to allow for proximity charging of the battery.

[0031] In a further feature of the disclosed DVT cuff, the control circuitry 50 includes an RF (radio frequency) sensor 56 in communication with the microprocessor 52. The RF sensor 56 is configured to detect an RF chip 65 inserted into the wrap 12. In one embodiment, shown in FIG. 6, the chip 65 is located in the flap 17' of the wrap 12. In one configuration of the present disclosure, the RF chip includes an RFID feature to provide a unique ID for the particular wrap 12. This feature allows the disposable wrap 12 to be uniquely associated with a particular cuff worn by a particular patient. The RF chip is read by a sensor 56 in the controller 14 attached to the wrap. Software within the microprocessor can control the function or operation of the DVT cuff based on the unique ID of the RF chip. In one configuration, the microprocessor allows the DVT cuff to operate only if there is a concordance between the unique ID of the RF chip and a database of known IDs.

[0032] The RF chip 65 is also configured to store data regarding the operation of the DVT cuff 10 and patient compliance. In one configuration, the chip includes sufficient memory to store data for 30 consecutive days. The microprocessor of the controller 14 is configured to upload the stored data from the RF chip through the RF circuitry 50 to on-board memory within the microprocessor 52. Note that the controller can be configured to limit the cumulative data displayed to the immediately preceding 48-hour period rather than the full 30-day period stored in the RF chip memory.

[0033] In a further configuration, the RF chip can store accumulated data regarding the use of the compression device. This data can be in the form of a cycle count representing the number of compression cycles performed by the device or an accumulated pulse count representing the rotational movement of the pulley, as described in further detail herein. The accumulated usage data can be compared to a threshold value within the controller 14 when the wrap 12 is paired with the controller. If the accumulated usage data stored in the wrap's RF chip 65 exceeds the threshold, the controller can deny concordance between the wrap and the controller and prevent the device from operating. This feature can ensure that the disposable wrap 12 is not used beyond its preferred useful life and that the wrap cannot be reused after disposal.

[0034] An alternative embodiment of a DVT cuff is shown in FIGS. 7-8. The modified cuff includes a modified wrap 12', which is configured similarly to wrap 12' to encircle a patient's limb and includes end loops 24' and flaps 17'. However, the mounting structure 40' for removably mounting a controller 14' is modified from the mounting structure 40. In this embodiment, the mounting structure 40' is a keyed hinge structure that includes a mounting pad 70 secured to the wrap 12'. The pad 70 includes a pair of keyed bases 72 integral with or attached to the pad. Each keyed base defines a keyed slot 73a that opens into a rectangular channel 73b. As shown in FIG. 8A, the slots 73a are wide enough to accommodate the rectangular hinge beam 76 of the controller 14' when inserted into the narrow portion facing the slot. As beam 76 passes through the slot and into channel 73b, the beam can be rotated (counterclockwise in the drawing) so that its wider dimension is aligned with the opening of the slot, thereby preventing the beam from being removed from the slot without rotating it in the opposite direction.

[0035] A hinge beam 76 is attached between a pair of mounting portions 75 that protrude from the base plate 42' of the controller 14'. The hinge beam 75 is configured as a rectangular beam for insertion into and rotation within the keyed slots and channels 73a, 73b, as described above. The controller 14' may otherwise be configured similarly to the controller 14, including a curved base plate 42' and a cover 44' that defines a pull strap slot 46' through which a pull strap (not shown) extends. With respect to the controller 14', the drive mechanism and control circuitry 50 may be the same as that of the controller 14. However, in this embodiment, because the controller 14' is attached to the wrap by a keyed hinge interface, the cuff 10' does not include the load cell feature of the cuff 10, which is configured to determine the load or force applied to the patient through the cuff. Instead, in this embodiment, the monitor can include the current sensor described above, which is used to determine the motor current during compression and therefore the tension in the wrap which correlates to the compressive force applied to the patient's limb.

[0036] Wrap 12' includes an RF chip 65' similar to RF chip 65 of wrap 12. However, in this embodiment, chip 65' may be attached to or embedded in mounting pad 70. Thus, chip 65', like chip 65, may be positioned to be detected by RF circuitry 56 of the control circuit.

[0037] Mounting pad 70 may incorporate ventilation holes 71. Similarly, flap 17' may incorporate ventilation holes or perforations, such as openings 71. In this particular embodiment, flap 17' is not formed of the same breathable material as wrap 12', but instead is formed of a flexible material that is not completely rigid, such as a low-density foam, specifically PORON® foam. A flap formed of low-density foam may have a basic shape that follows the curvature of the patient's limb, but is flexible enough to bend as needed to avoid applying pressure to the skin. In this case, ventilation holes 71 in flap 17' are beneficial for providing airflow to the patient's skin in contact with the flap. While openings or perforations 71 are shown as circular, they may have other configurations, such as extending slots through pad 70 and flap 17'.

[0038] The wrap 12' for the compression device 10 can be modified, as shown in FIGS. 25-27, to facilitate positioning the device on a patient's limb. As shown in FIG. 25, wrap 12' can be replaced with wrap 1200, which can be formed of the same material and have the same overall length as wrap 12' to encircle a portion of the patient's body, typically a limb. Wrap 1200 includes a portion 1202, which can generally correspond to flap 17' of wrap 12' in that an attachment structure 40' is attached to one end of portion 1202. Like flap 17', portion 1202 is also positioned between the controller 14' (FIG. 27), which is attached to the attachment structure 40', and the patient's skin. As shown in FIG. 25, portion 1202 of wrap 1200 terminates at end 1204 in a slot 1206 configured to receive the opposite end 1210 of the wrap in a loop, as shown in FIG. 26. Thus, slot 1206 allows wrap 1200 to be temporarily attached to a patient's limb, such as the leg shown in FIG. 26, before a controller is attached to the wrap. This feature facilitates initial placement of compression device 10 on the patient, as wrap 1200 and attachment structure 40' can be optimally positioned on the patient's limb before engaging the controller. This feature also facilitates removal and replacement of the controller while the wrap is still engaged to the patient, without having to remove the entire device, wrap and all, from the patient.

[0039] As shown in FIG. 27, the controller 14' can be attached to the wrap by engaging the attachment structure 40' as described above. As shown in FIG. 27, the controller is engaged with the attachment structure and pivoted toward the portion 1202 with the pull strap 20 fully extended. In this configuration, the D-ring 22 is positioned directly over the slot 1206, around which the end 1210 of the wrap is looped. The loop can be removed, and the end 1210 can be threaded through the D-ring 22 and extended further through the slot 1206. Once the end 1210 is threaded through the slot, it is threaded through the D-ring 22 and looped around it, so that the wrap holds the portion on the patient's limb. As described above, the end 1210 can be tightened as needed to provide initial attachment tension for the wrap 1200.

[0040] As shown in FIG. 25 , strap 1200, and specifically portion 1202, is configured to provide a predetermined distance D between attachment structure 40′ and slot 1206. This distance corresponds to the extended length of pull strap 20 relative to controller 14′, which allows D-ring 22 to be aligned with slot 1206, as shown in FIG. 27 . In one specific embodiment, distance D is 4.91 inches (4.91 × 25.4 mm), and the distance from attachment structure 40′ to the edge of wrap end 1204 is 5.75 inches (5.75 × 25.4 mm). This dimension not only allows for proper orientation of the D-ring relative to the slot, but also avoids issues with portion 1202 crimping when pull strap 20 is retracted during a compression cycle. Wrap portion 1202 engages pull strap 20 by looping end 1210 through both D-ring 22 and slot 1206. Thus, when the pull strap is retracted, it pulls on the end loop 1210, thereby reducing the effective diameter of the wrap 1200 and causing compression. Retraction of the pull strap also pulls the end 1204 of the portion 1202 toward the controller 14'. If the portion is too short, the portion will tend to bunch up under the controller, thereby interfering with the compression applied to the patient. In the illustrated embodiment, distance D allows portion 1202 to bunch outside of the controller in a way that does not change or interfere with the compressive force applied to the patient.

[0041] In both of the DVT cuff embodiments of FIGS. 1-8 and 25-27, the cuff 12, 12', 1200 and the controller 14, 14' are separate, separable units. The cuff 12 includes a chip 60 that can easily receive the load cell axle 60 for attaching the controller 14 to the cuff. The cuffs 12' and 1200 include a keyed base 72 that allows the controller 14' to be quickly attached to the cuff 12'. Each of the cuffs 12, 12', 1200 is configured to be patient-specific and disposable. The RF chip 65, 65' for each cuff includes a unique ID or serial number stored on the chip and readable by the RF circuitry 56 of each controller, which ID can be associated with a particular patient. As mentioned above, the microprocessor 52 includes software that reads the chip's ID and authenticates the chip, and therefore the wrap, as an authorized unit. Furthermore, in a patient setup, the unique ID also becomes the patient's unique ID. Regardless of which controller reads the RF chip data, that data is always associated with the unique chip ID and therefore with the particular patient to whom the cuff 12, 12', 1200 was issued.

[0042] The controller is not intended to be disposable and is reusable with all certified and authorized cuffs. Because the controller is not specific to any particular cuff, it can be used with multiple cuffs, making it particularly useful in a hospital setting. Because DVT cuffs are not used sequentially on a patient, one controller can be used to control compression protocols for multiple patients, with each patient uniquely identified by the cuff 12, 12', 1200 issued to that patient. The cuff always remains with the patient, but the controller can be maintained in a separate storage unit. In a hospital, each ward or unit in the hospital can have its own controller, and all can be used interchangeably with all patient-specific cuffs in all wards or units in the hospital. Thus, a patient undergoing surgery can be fitted with a DVT cuff that operates during surgery to prevent the onset of a DVT condition. When surgery is complete, the controller is removed and maintained on the surgical unit, and the patient is sent to a recovery ward or ICU where the controller maintained on the ward or unit can be engaged with the patient's cuff, and DVT prevention treatment continues during recovery. If the patient is transferred to a long-term care unit, the recovery ward controller is removed, and a controller maintained on the treatment ward is engaged with the patient's cuff. If the patient is released but DVT treatment is still prescribed, the patient can take home their assigned cuff 12, 12', 1200, along with a separately prescribed controller for home use. Once treatment is complete or the risk of DVT has passed, the patient can dispose of the cuff and return the controller 14, 14' to the medical facility.

[0043] In one aspect of the present disclosure, a kiosk 80 can be provided, as shown in FIG. 9 , that includes multiple bays 82 for storing several controllers 14, 14′. Each bay can include a charging station for charging the batteries of each controller. Each bay can also include a data cable for connecting to the controller's data jack, allowing for the uploading and downloading of data, information, application software, updates, upgrades, and the like. The digital processor or microprocessor of each controller includes software and / or firmware for handling this data transmission. The control circuitry 50 can also include a wireless transmitter / receiver, such as a WiFi-enabled antenna, to allow remote data transmission and reception, and the kiosk can be similarly configured for wireless communication. The controller storage bays 82 of the kiosk 80 can include a digital processor that controls communication with each of the controllers stored therein. The processor can communicate with each controller's processor via wired or wireless means, such as using WiFi or Bluetooth transmission protocols. Each controller or microprocessor 52 is uniquely identifiable, such as by a unique stored address, thereby facilitating communication between the kiosk processor 84 and the microprocessor 52. The kiosk processor may include software for manipulating and / or analyzing data downloaded from the controllers and a user interface (not shown) for providing access to this information to medical personnel. For example, it is contemplated that each unit or ward of a hospital may have one or more kiosks 80 for storing and maintaining multiple controllers 14, 14' for use by patients in that hospital unit. For ease of use, the kiosks may be carried on a mobile base 81.

[0044] The kiosk may also include a module 88 for use in charging replaceable batteries. Another module 87 may incorporate a disinfection device, such as a UV-C lamp, which may aid in disinfecting the controller after each use. The kiosk also includes multiple bays 85 for storing new wraps 12, 12' for initial dispensing to patients.

[0045] Returning to the controller 14, 14' associated with the wrap 12, 12', 1200, the microprocessor 52 can execute software or firmware that monitors various attributes of the DVT cuff and the patient, and then displays the relevant information on the display 15. An exemplary data display is shown in FIGS. 10A-10C. The display includes a header band that describes the treatment, in this case "DVT Prophylaxis," and also provides the current time in box 100 and battery status in box 101. The next row of the display includes three boxes indicating the patient's activity: box 102 corresponds to "In Bed" time, box 103 corresponds to "Sit-Stand" time, and the final box 104 corresponds to "Step" time. The accelerometer 55 and microprocessor 52 integrated into the controller 14, 14' are configured to ascertain the patient's physical position (i.e., supine, sitting, or standing) and the patient's activity (i.e., walking). It should be noted that a gyroscope may be included along with the accelerometer to enhance detection of the patient's position and movement. The microprocessor 52 is configured to evaluate all sensor data and to accumulate activity information that is displayed on the device. It should be noted that this same information is communicated to and stored in the RF chip 56 associated with the wrap 12 as the data is generated. This data maintained by the RF chip can be later uploaded by another controller or by another digital processor.

[0046] As reflected in FIG. 10C, the first activity box 102, the "in bed" time box, is highlighted to indicate that the information in the next row of the display is related to that patient activity. The other two boxes 103, 104 can be highlighted using the touchscreen feature of the display 15, in which case the next row will display information related to either a "sit-to-stand" activity or a "step" activity. In the display shown in FIG. 10A, the healthcare professional has selected the "in bed" information, so the third row of the display identifies in box 105 the amount of time the patient spent in this current "activity," i.e., how long the patient was lying supine or lying down in bed. Box 106 displays the total amount of time the patient spent in "in bed" activity for the current day. This information is also displayed in box 102 in the second row of the display, even if the "in bed" activity is not selected. The final box 107 displays the amount of time spent in "in bed" activity for the previous day.

[0047] FIG. 10B shows the display when the "Sit-Stand" box 103 is selected by the healthcare professional. The third row of boxes 105', 106', and 107' displays the current session time, the accumulated time for the current day, and the accumulated time for the previous day in the "Sit-Stand" activity. For this activity, the accelerometer 55 data indicates that the patient is no longer lying or supine. Note that because the DVT cuff is on the patient's leg, the lower leg is substantially vertical during the "Sit-Stand" activity but substantially horizontal during the "In Bed" activity. Microprocessor 52 can distinguish the accelerometer data to accurately determine the patient's physical position. The total time for that day, displayed in box 106', is also displayed in activity selection box 103.

[0048] FIG. 10C shows the display when the third "Step" activity in box 104 is selected. Again, the third row of displays 105", 106", and 107" provide an indication of the level of "Step" activity. However, rather than displaying time data, the displays show the number of walking steps taken by the patient, as determined by the accelerometer data. The total steps for that day, displayed in box 106", are also displayed in activity selection box 104. Thus, by viewing the second row of display boxes 102, 103, and 104, a medical professional can at a glance determine patient compliance with DVT prophylaxis. It can be appreciated that the microprocessor can determine the amount of time spent walking, rather than the number of walking steps, and therefore the data in box 106" can be time data.

[0049] All of this information gives the healthcare professional or caregiver a complete description of patient compliance with compression protocols and mobility regimens. "Early mobility" or "progressive mobility" programs have been shown to reduce the incidence of hospital-acquired and recovery-acquired events, including not only DVT but also pressure ulcers and infections. Mobility protocols have also been associated with reduced length of hospital stay, readmission rates, and overall cost of stay. Having readily available patient compliance and activity information can enable healthcare professionals to address deviations from recommended prophylaxis protocols.

[0050] In one embodiment, patient compliance information is displayed on the controller, as described above. In another embodiment, patient compliance information is sent from the controller to a separate display in the patient's hospital room. However, rather than cycling through the various screens shown in FIGS. 10A-10C, the room display summarizes the compliance data to provide the healthcare professional or caregiver with a quickly understandable reading of the patient's status. The summary includes total DVT prophylaxis time, total time in bed, total sitting time, and total steps over a predetermined elapsed time. According to one configuration of the present disclosure, a display device 110 can be provided as shown in FIG. 10D. The device 110 includes a housing 112, which can be wall-mounted or freestanding. The device can be battery-powered or tethered to a separate power source. The device includes a digital processor, such as a microprocessor, that can wirelessly communicate with a cuff 12, 12', 1200 worn by a person in the healthcare facility. Thus, the cuff worn by the user may include wireless communication features, such as Bluetooth, that allow data to be transmitted from the cuff to the display device 110. The data transmitted from the patient-worn cuff 12, 12', 1200 to the device 110 may be the same information displayed on the patient's cuff as shown in FIGS. 10A-10C. This information may be displayed in the display field 115 of the device 110. In addition to accumulated time (prophylaxis, in bed, etc.), the display field 115 may display the patient's goals. Thus, as shown in FIG. 10D, the patient has a goal of 18 hours of total DVT prophylaxis time. The total prophylaxis time to date is displayed near the goal, in this case 10 hours, so that the medical professional can immediately get a sense of the patient's progress. For example, the physician may establish goals for DVT prophylaxis time, bed time, sitting time, and steps to enable the patient to be released from treatment. The display field 115 can act as a motivator for the patient as they see their progress towards their goals.The display field can also provide the physician with a quick and understandable reference for making a decision as to whether the patient needs further interaction and encouragement to reach stated goals.

[0051] In another aspect, the disclosed compression therapy system uses a Mobility Health Index (MHI) to provide a single number indicating patient compliance and progress. The MHI is based on all of the information listed above, with each type of data assigned a different weight. The weights are established according to the desired focus among four types of data (DVT time, time in bed, sedentary time, and walking volume). For example, in one example, DVT prophylaxis time can be weighted more heavily than the other three types of data, while the other three types of data can be weighted equally. Thus, in this example, DVT prophylaxis time can be weighted 0.40, and time in bed, sedentary time, and step count can each be weighted 0.20. Physicians can adjust the weights to fit their desired recovery protocol for their patients. For example, a lower weight can be applied to step count for an otherwise very immobile patient, and a lower weight can be applied to time in bed if the physician wants to encourage the patient to get out of bed.

[0052] For a patient, goals can be established for each type of data. For example, a patient's goals for DVT prophylaxis time can be 18 hours, time in bed 12 hours, sedentary time 6 hours, and steps 100. The percentage of actual time spent in each activity toward the goal can be multiplied by the weight for that particular activity to determine the contribution of that particular activity to the patient's overall MHI. In other words, the following calculation is performed:

[0053] DVT contribution = DVT prevention time × (DVT weight ÷ DVT target)

[0054] If actual time in bed ≦ target, In-bed contribution = in-bed time × (in-bed weight ÷ in-bed goal) If not, (In-bed target - in-bed time) x (In-bed weight ÷ (DVT target - in-bed target))

[0055] Sedentary contribution = sedentary time × (sedentary weight ÷ sedentary goal)

[0056] Step contribution = number of steps × (step weight ÷ step goal)

[0057] MHI = DVT contribution + bed contribution + sitting contribution + step contribution

[0058] The table below represents a specific example of an MHI calculation according to the present disclosure shown in the display of FIG. 10D.

[0059] [Table 1]

[0060] According to this embodiment, a separate in-room display device prominently displays the MHI number, in this case 48, in display field 117, providing attending medical personnel with an immediate and direct indication of how well the patient is recovering. An MHI of 100% means the patient has met all of their prescribed mobility goals. A number significantly less than 100% may indicate that the patient is not complying with their DVT treatment regimen, which may lead to medical personnel intervention to motivate and monitor the patient to improve compliance. To further assist medical personnel, and even patients, in tracking the progress of the patient's recovery, display device 110 may include a display field 118 for a three-day history of calculated MHI. The device may also include a whiteboard field 119 where the medical personnel or doctor can write the MHI goal for the day, which is 56 in this example of FIG. 10D. The physician may set goals based on the physician's assessment of the patient's abilities and competence with respect to the goals to motivate the patient to work hard in the recovery process. The whiteboard field 119 may be a whiteboard or other similar physical surface on which the healthcare professional can write the goals with an appropriate pen, or it may be a touch screen or similar electronic device on which the healthcare professional can create images by moving a stylus or finger within the field.

[0061] The collection of data for the MHI calculation and those calculations can be performed by the compressor controller or processor and then transmitted wirelessly to the device 10 configured as a room-mounted display. Alternatively, the room-mounted display can include its own processor that can receive activity data transmitted from the compressor controller and perform the MHI calculation. Further alternatively or additionally, the common station can display room-specific information, where the display shows information identifying a particular patient.

[0062] The DVT cuff can be placed on a patient's limb, such as the patient's leg, as described above. The end loop 24 can be used to tighten the wrap 12, 12', 1200 around the leg, providing a light grip but sufficient to hold the cuff in place. A power switch (not shown) on the controller 14, 14' is actuated to activate the microprocessor 52 and initiate a start-up screen on the display 15. The microprocessor first checks the pulley sensor 54 to determine if the pulley 34 is in its proper initial or "home" position. If not, the microprocessor commands the motor controller 53 to operate the motor 32 in an "unwind" direction, such as counterclockwise. Power remains supplied to the motor until the pulley sensor 54 detects that the pulley is in its home position.

[0063] Once the pulley returns to home position, the microprocessor prompts the operator by displaying a "Pretension" button on the touchscreen display. When the operator presses "Pretension," the microprocessor sends a command to the motor controller to set the motor direction to the "winding" direction, i.e., clockwise in this example. The microprocessor then sends a second command to the motor controller to energize the motor and set the motor speed to a predetermined speed, preferably in the medium range for this motor. As the motor runs, the transmission 33 reduces the motor speed to a suitable medium range for the pulley, such as 10-15 rpm. As the pulley retracts the wrap, the microprocessor monitors the force applied to the wrap via the load cell 57. Alternatively, or additionally, the microprocessor can monitor the motor current, as described above, which varies as a function of the load applied to the wrap (or, more precisely, the reaction load experienced by the controller). When the minimum pretension is achieved, which in a specific example is about 1 pound (about 0.453 kilograms), the microprocessor commands the motor controller to stop the motor and hold the pulley in its current position. Thus, the wrap is pretensioned with a known amount of compression on the patient's leg. In one embodiment, a new home position for the pulley can be set to correspond to the pulley's position with the wrap pretensioned.

[0064] Once the wrap and controller are properly attached and the desired pretension is achieved, the microprocessor notifies the display 15 that a compression protocol is being initiated. In one exemplary embodiment of the compression cuff 10, the compression protocol may be for DVT prevention. However, it is understood that other compression protocols are also contemplated and readily implemented with the cuff herein. The set of instructions from the microprocessor 52 to the motor controller 53 is generated by software / firmware executed by the microprocessor. This software may be configured as a general set of commands that reads compression variables, such as variables including on-off times, dwell times, power levels, etc., from a stored database. This database may be included in the microprocessor's memory or downloaded from a remotely stored database. Alternatively, the software itself may be application-specific, with all of the protocol-specific variables hardwired into the software commands. Thus, it is contemplated that the variable database and / or protocol-specific software may be patient-specific and built into each controller 14 used by a particular patient. In this regard, the variable database may be stored on the RF chip 65, 65' associated with the patient's cuff and then uploaded to each controller 14 that is connected to the patient's cuff.

[0065] Returning to the operation of the drive system for the cuff 10, when a compression protocol is initiated, the microprocessor sends commands to the DC motor controller circuit to set the motor direction to clockwise and the motor power value to full power. In one embodiment, the motor controller is a pulse-width modulation controller, in which case full power mode corresponds to a PWM input of 254 for 100% duty. In one particular embodiment, in the motor's full power mode, the pulley rotates at approximately 30 revolutions per minute (rpm) with a torque of 310 inch-ounces (310 x 0.007 Nm). During compression, the microprocessor continuously monitors the compression wrap force via the load cell 57 (DC motor current). When the force applied to the wrap equals the pretension plus a predetermined offset force, for example 7 lb (7 x 0.453 kilograms (1 lb is approximately 0.453 kg)), the microprocessor sends a "stop" command to the DC motor controller, cutting energy to the DC motor. The microprocessor holds the pulley position for 500 milliseconds. After the "hold," the microprocessor sends a counterclockwise motor direction command to the DC motor controller and sets the motor power to a "low" speed, which may correspond to a PWM input of 60 for a 25% duty cycle. As the motor rotates counterclockwise toward the home position, loosening the pull strap 20 and reducing the wrap compression, the microprocessor monitors the force until the pretension is met, after which the microprocessor sends a stop command to the DC motor controller. In an alternative embodiment where the new home position of the pulley is reset to correspond to the pretensioned pulley position, the microprocessor can monitor the pulley sensor and send a stop command when the pulley reaches the updated home position. After the stop command is executed, the microprocessor updates the compression duration and resets the cycle timer to 0. When the cycle timer reaches a predetermined dwell time, such as 60 seconds, the compression process begins again.

[0066] As mentioned above, the compression achieved by the DVT cuff is produced by a small DC motor 32 within the controller 14. The cuff 12, 12' is secured at one end of the controller housing, either directly or via a load cell 57, as described above. The opposite end of the cuff is an end loop 24, which connects to a D-ring 22 at the end of a pull strap 20. The pull strap is secured to a rotating pulley 34, so that rotation in one direction, such as clockwise, reels the pull strap around the pulley. As the strap reels, it pulls on the D-ring, which pulls on the wrap 12, essentially shortening the effective length of the wrap and tightening it around the patient's limb / leg.

[0067] As described above, the microprocessor 52 of the controller 14, 14' can be programmed for many different compression protocols. In the illustrated embodiment, the cuff 10 serves as a DVT cuff to prevent deep vein thrombosis in a patient's limb, specifically the leg. To avoid DVT, the goal is to push blood from the femoral vein toward the heart. However, it is known that simply applying pressure to the lower leg to push blood toward the heart does not eliminate the risk of DVT. Instead, achieving a specific flow rate in the femoral vein is critical for successful DVT prevention. Specifically, it is known that a flow rate approximately three times the patient's baseline flow rate in the femoral vein is effective for DVT prevention.

[0068] In one aspect of the present disclosure, an optimal compression protocol for DVT prevention has been developed for implementation in the non-hydraulic compression cuffs disclosed herein. The graph shown in FIG. 11A is a Doppler image of blood flow velocity in the femoral vein of a patient wearing the DVT cuff 10 of the present disclosure. The graph in FIG. 11B is a compression profile applied by the controller 14, 14′ via the wraps 12, 12′ to achieve the blood flow profile shown in FIG. 11A. The graph also shows the tension applied to the wraps, which translates to compression force applied to the patient's limb. As shown in the graph in FIG. 11B, the compression protocol includes four segments: one pretension segment and three compression segments, which occur over a period of less than approximately six seconds. The pretension stage establishes a baseline pressure at the limb, which holds the DVT cuff on the patient's limb without exerting significant pressure. In one embodiment, the pretension (again, the tension in the wraps) is less than 1 lbf (approximately 4.448 N). As noted above, during pretensioning, the DVT cuff is actuated at a relatively slow speed (pulley speed of 10-15 rpm) for less than 1 second, so as not to produce any appreciable upward blood flow, as reflected in the Doppler image in Figure 11A. While the pretension segment is immediately followed by the compression segment in the graph in Figure 11B, there may be some delay after pretension is established. However, it is preferable that the compression cycle begin immediately after the appropriate pretension is achieved.

[0069] In the second stage, or first stage of the repeated compression protocol, the motor is driven at its maximum speed for less than one second until a predetermined maximum tension in the wrap is reached. In one embodiment, this maximum force can be in the range of 5.5-6.5 lbf (5.5 x 4.448 N to 6.5 x 4.448 N), which corresponds to a maximum tension in the wrap of between about 6.5 lbf (about 6.5 x 4.448 N) and about 7.5 lbf (about 7.5 x 4.448 N) (for a pretension of 1.0 lbf (4.448 N)). The required upward flow of blood into the limb at three times the normal flow rate or flow velocity in the femoral vein can be achieved by tensioning the wrap. It is known that the amount of compressive force applied is not the only factor that determines its rapid application. Thus, in the exemplary embodiment, the DVT cuff achieves maximum applied force in less than about 1 second. This pressure is maintained during the hold segment shown in FIG. 11B, which in this exemplary embodiment is preferably about 0.5 seconds. This hold time is important to avoid a sudden collapse of the compression profile due to the elasticity of the femoral vein and fluid pressure within the circulatory system.

[0070] The fourth, or third, segment of the compression cycle releases the tension on the wrap, and therefore the compression on the patient's limb, gradually to allow blood flow to return to the patient's normal baseline rate. Thus, the motor is reversed and driven at approximately one-quarter motor speed during the third segment of the repeated compression cycle. In an exemplary embodiment, the motor is driven at approximately a 25% duty cycle for a period of approximately three seconds. At the end of the relaxation segment, the DVT cuff is returned to its pretensioned state (1.0 lbf (4.448 N) in this embodiment), and the motor is deactivated for a predetermined dwell time before another compression, hold, and relaxation cycle. As mentioned above, this dwell time can be approximately 60 seconds. The controller 14, 14' repeats these three segments for the prescribed treatment period, which can range from 15 minutes to 1 hour, or 15-60 compression cycles, as needed for the patient. During each compression cycle (compression, hold, and relaxation), blood velocity follows the profile shown in Figure 11A for optimal DVT protection. Once the treatment time is reached, the controller can continue the final relaxation stage until all compression forces, including pretension, are removed. Alternatively, after the force has decreased to the pretension, the DVT cuff can be removed by simply peeling the end loops 24 off the D-rings 22 of the controller.

[0071] Note that the graph in Figure 11B is an idealized force profile for producing the desired blood velocity. The graph in Figure 11C is the force profile of actual actuation of DVT cuff 10 on a patient's leg, which produced the flow velocity in Figure 11A. During the hold segment of the force profile, it can be seen that the compressive force drops slightly from the hold value in the idealized graph in Figure 11B. This slight drop is believed to be due to the elastic response of body tissue to rapid compression. Nevertheless, even with this slight deviation from maximum compressive force, the blood velocity still follows the preferred profile of Figure 11A for preventing the onset of a DVT condition.

[0072] As described above, the DVT cuff 10, 10′ includes a removable and replaceable controller 14, 14′, which includes a control circuit 50 for controlling the operation of the cuff, i.e., the pretension and compression stages, as well as data collection and retrieval. The control circuit 50 includes a microprocessor 52 and associated digital memory, which contains software and / or firmware that controls the operation of the cuff. FIGS. 12-19 show flowcharts of various functions performed by the DVT cuff 10, 10′ and kiosk 80. It is contemplated that the DVT cuff of the present disclosure can be used as a “standalone” device, such as for treatment in an individual patient’s home, rather than in association with a kiosk, as may be the case in a hospital setting. Accordingly, the steps for initializing the controller for a stand-alone (i.e., not associated with a kiosk) DVT cuff are shown in flowchart 200 of FIG. 12. The controller can be provided pre-packaged with a replaceable battery separated by a tab. In a first step 201, the tab is removed and the controller is powered on. In a next step 202, the microprocessor automatically initiates a boot-up process in which various electrical components and sensors are activated and checked. In step 203, a battery check is performed, and in step 204, a "low battery" indication is provided on the controller screen 15. If the battery has sufficient power, in step 205, the controller activates the wireless communication component, which allows the controller to communicate with a kiosk. In step 206, a "Connect to Kiosk" indication is generated along with a "No Kiosk" button, which can be pressed on the touchscreen display 15 in step 207 to indicate that the controller is not operating in association with a kiosk. Note that in this disclosure, the controller 14, 14' is configured for operation with or without a kiosk, hence steps 206 and 207.However, in an alternative embodiment, for DVT cuffs intended for use outside of a hospital setting, the wireless kiosk communication feature may be omitted, and the wireless communication feature may still be activated in step 205 for communication with a different device, such as a Bluetooth-enabled smartphone or similar device.

[0073] In the next step 208, a display is provided that allows the operator to select between two optional modes of the DVT cuff: mobility and DVT prophylaxis, and DVT prophylaxis only. In both modes, the DVT compression protocol is enabled, but in the first mode, the patient is expected to move away from the hospital bed. The mode selection is dependent on the patient's treatment protocol. If "mobility and DVT" is selected, the controller sends that display to the screen in step 209, which allows the operator to enter the elapsed time for use of the DVT cuff in mobility mode. Once that mode is selected, the controller displays that the controller is ready for use in step 210, after which the controller powers down in step 211.

[0074] Flowchart 300, shown in FIG. 13, is provided for a controller 14, 14' paired with a kiosk 80. In this case, both the DVT cuff controller and the kiosk are activated, following separate operational flowcharts 301, 302, respectively. In the cuff controller sequence, the first five steps 304, 305, 306, 307, and 308 are identical to the non-kiosk controller operation of flowchart 200 of FIG. 12. However, in step 308, program flow continues based on the cuff controller being used with the kiosk. If so, a determination is made in step 309 whether the cuff controller is paired with the kiosk. If not, an error message is displayed in step 310, and the process returns to step 307 to activate the wireless or Bluetooth mode. If pairing is successful, a message is displayed on the controller screen 15 in step 311, and the controller is powered down in step 312 until future use by the patient.

[0075] It is understood that conventional Bluetooth pairing techniques can be implemented between the controller and the kiosk. It should also be understood that the pairing step requires activation of the kiosk in accordance with flowchart 302. Thus, when the kiosk data processor 84 is activated, an initial setup screen is displayed in step 313, which allows the operator to set the date and time, and then activate the pairing sequence in step 314. A pairing screen is displayed by the kiosk processor 84, as shown in step 315, which detects a table of uniquely identified cuff controllers in the vicinity of the kiosk. The user can select the appropriate controller to pair, after which a successful pairing is displayed in step 316.

[0076] Flowchart 400 of FIG. 14 illustrates the steps implemented by the DVT cuff controller in a DVT prevention mode of operation. This mode of operation begins with the selected controller 14, 14' activated to perform the initialization steps described in connection with flowcharts 200, 300 of FIGS. 12-13. In response to a display on the controller screen 15 in step 402, the selected controller is attached to the wrap 12, 12' in step 401. An authentication process for the wrap is initiated in step 403, with the controller's onboard RF sensor 56 reading the wrap's RF chip 65 in step 40. If the identifier does not match a database of appropriate identifiers, the controller displays a message in step 405 that the cuff is not compatible with the controller, i.e., the cuff is unreliable for use as a DVT compression device.

[0077] On the other hand, if the RFID proves reliable, the controller writes the start date and time to the RF chip 65 of the wrap 12, 12' and stores the wrap's identifier in the memory of the controller 14, 14'. In step 407, the controller checks whether the two writes were successful; if not, it generates an error message in step 408 and returns the controller to the initial step 402. If step 407 determines that the writes were successful, program flow proceeds to step 409, where pretension is applied to the straps. In this first step, the patient, or preferably a healthcare professional, adjusts the end loops 24 of the straps at the D-rings 22 of the controller 14, 14' to apply initial tension to the wrap at the patient's limb, typically the leg. In initial step 410, the controller measures the force on the wrap and makes a determination as to whether the proper amount of pretension or tightness of the wrap has been achieved. In one specific embodiment, that force value is 1.0 lbf (4.448 N), which has been found to be the optimal starting tension for DVT prophylaxis protocols. If the amount of pretension is not the desired value, the controller attempts to determine whether the wrap is too loose or too tight in step 411. If too loose, a message is displayed in step 412; if too tight, an appropriate message is provided in step 413. In step 414, the patient or healthcare professional adjusts the cuff pretension by adjusting the end loop 24 at the D-ring 22. This process continues until the appropriate tension is applied to the wrap. In an alternative embodiment, if the wrap is less than the desired pretension by a predetermined amount, the controller can activate the motor 32 to pull the D-ring 22 until the required pretension is reached. Of course, if the current wrap force is greater than the desired pretension, the motor cannot loosen the wrap tension; only adjustment of the D-ring loop allows for a reduction in the initial wrap tension.

[0078] Once the amount of pretension or initial force is achieved, the controller initiates the DVT protocol in step 415 and displays the message "DVT Prevention Running" on the controller screen. In step 417, a determination is made as to whether the DVT cuff is to be operated in DVT only mode or DVT + mobility mode. This determines whether to continue the "DVT Prevention Running" screen in step 418 or to display additional display related to the mobility function in step 419 (see FIG. 16). In the former case, the "DVT Prevention Running" screen continues as long as the DVT compression protocol is active. This protocol can continue for a predetermined time or number of compression cycles, as monitored and controlled by the controller 14, 14'.

[0079] As noted above, the DVT cuff of the present disclosure contemplates removal and replacement of the controller from a particular patient's wrap. The present disclosure also contemplates removing a patient's current wrap and replacing it with a new one. After extended use, the wrap may become soiled with sweat or other liquids, necessitating the need for a new wrap. The wraps disclosed herein are intended to be disposable; therefore, there is no particular benefit to removing, cleaning, and replacing a particular wrap, particularly in a hospital setting. A method for changing a given wrap for a new one is shown in flowchart 500 of FIG. 15. In a first step 501, the current controller is deactivated and removed from the current wrap, which can then be disposed of in a conventional manner. A new wrap is provided, and in step 502, the current controller is attached to the new wrap. In step 503, the authentication process begins: the RF chip 65 of the new wrap is read and compared to a database of acceptable identifiers in step 504, as with the initial use of the wrap described in flowchart 400. If the new wrap is not properly authenticated, a message is displayed in step 505. If not, process flow continues to step 506, where the RF identifier stored in the controller 14, 14' is updated to the identifier of the new, properly authenticated wrap. In step 507, the identifier is re-authenticated, a new start date and time for that particular wrap is written to the RF chip of the new wrap, and the new identifier is written to the current controller. If step 509 determines that the write was unsuccessful, an error message is displayed in step 510, and the process returns to the earlier step to verify proper attachment of the controller to the wrap. If the write was successful, steps 511-516 of the pretensioning process are performed, similar to steps 409-414 described above in connection with flowchart 400.Similarly, once pretensioning is complete, the controller proceeds to DVT prevention and mobility activities in steps 517-521, which are similar to steps 415-419 of flowchart 400.

[0080] A mobility display is provided in flowchart 600 of FIG. 16. The controller makes a determination about the patient's location or activity based on data obtained from the accelerometer 55 or other physiological sensors integrated into the controller 14, 14′. Thus, the patient is lying down in step 601, sitting in step 607, or walking in step 613. Each patient state has an associated set of screens shown on the controller's touchscreen display 15. If the patient is lying down or in bed, in step 602, the screen display highlights or illuminates the display box 102 ( FIG. 10A ) corresponding to the “In Bed” screen. However, the user can switch the display to one of two other displays by pressing the corresponding tabs 103, 104 on the touchscreen display. Touching one of the other displays for 15 seconds in steps 603, 605 causes the controller to switch the display to the associated “Walking” or “Sitting” display in steps 604, 606, respectively. If the display is initially "sitting" in step 607, the same process applies, with steps 608-611 being performed to change the display to either "in bed" or "ambulatory" view, and if the display is initially "ambulatory" in step 613, steps 614-617 are performed to change the display to either "in bed" or "sitting" view. This feature allows medical personnel to always have a complete picture of patient compliance with the prescribed DVT prevention protocol.

[0081] Regarding patient compliance, as discussed above, compliance with DVT protocols is often problematic. Similarly, determining the level of patient compliance is always difficult and often requires firsthand knowledge from a healthcare professional as to whether the patient is engaging in the required physical activity and activating the DVT cuff according to the prescribed protocol. The DVT cuff 10 of the present disclosure provides healthcare professionals with important information for assessing the level of compliance for a particular patient. In addition to the various indicators discussed above, the pretensioning step also ensures compliance. If the cuff is not properly wrapped around the patient's limb with the appropriate amount of pretension, the controller will not allow the DVT prophylaxis sequence to begin. The RF chip in the patient's wrap can store time and date information regarding the initiation and completion of the DVT prophylaxis sequence, information that can be accessed by healthcare professionals to verify patient compliance. Additionally, the controller can display information indicative of patient compliance, such as a "DVT prophylaxis in progress" message (see, e.g., steps 416 and 418 of FIG. 14), as well as an error message if the wrap is not properly placed on the patient's limb. The RF chip 65 can also store error messages indicating non-compliance that can be accessed by medical personnel.

[0082] When a particular controller is no longer in use, it can be stored, such as in the kiosk 80 described above. In this case, the controller and kiosk follow a flowchart 700 for storing the controller, as shown in FIG. 17 . The controller flowchart 701 includes a first step 703 for storing the controller under two scenarios. In the first scenario, the controller is configured and ready to be used, and in the second scenario, the controller has just been used by a patient. In both cases, the controller is turned off, and the replaceable battery is removed and placed in a charging station in one of the bays 82 of the kiosk 80. In step 704, a determination is made as to whether the controller contains patient data uploaded from the RF chip in the patient's lap. If no, control passes to step 705, and a "Ready for Use" message is displayed in step 706. Note that in one embodiment of the present disclosure, the display 15 is an E-ink display, and therefore, the "Ready for Use" message remains on the screen even when the controller is powered down.

[0083] If the controller contains uploaded patient data, the controller displays a message in step 707 and activates wireless or Bluetooth communication between the controller and the kiosk in step 708. The controller times out after a predetermined "connect" time and determines in step 709 whether the data download to the kiosk was successful. If not, the controller returns to steps 707 and 708 to attempt the download again. If the download was successful, the controller clears its memory of the patient data, resets any control variables that may have been changed, activates the "Ready for Use" display in step 706, and powers down the controller.

[0084] On the kiosk side 702 of flowchart 700, the kiosk processor displays a selection screen in step 711, where the user can select “Services” to proceed to display in step 712. This screen allows the user to select from the following service functions: patient data upload, controller software / firmware upload, or kiosk software / firmware upload. For controller storage, the user selects to upload patient data, and the kiosk processor automatically connects with the previously paired controller in step 713. In step 714, an automatic download process occurs, followed by a message on the kiosk processor indicating the download is complete and including an identifier for the particular controller. It is understood that a given kiosk can store multiple controllers, so the download can be from multiple controllers. Patient-related data is maintained in the kiosk processor's memory for later review and / or processing by medical personnel. The kiosk can be paired with another device other than a DVT cuff controller, allowing patient data to be downloaded to a device such as a smartphone or smart pad for review by healthcare professionals.

[0085] At the end of a patient's DVT session, it is desirable to remove the controller from the wrap associated with the patient. Flowchart 800 illustrates the steps, with a first step 801 being to press and hold the power button for a specified period of time, such as three seconds. This activates the controller, which then determines, in step 802, whether any patient data has been provided in the controller memory. If not, a "Controller Ready for Use" message is generated in step 803, after which the controller powers down in step 804. If patient data is found, the data is uploaded in step 805, after which the controller powers down in step 804. In one configuration, step 802 can first determine whether the wrap's RF chip 65 contains patient usage data, and then upload that data to the controller's processor memory.

[0086] Figure 19 provides a summary of display screens 900 generated by the kiosk processor. Main screen 901 provides access to various tasks performed by the kiosk, including setting the day 902 and time of day 903. The kiosk can be paired with multiple controllers via screens 904, 905. Selecting "Services" on the main screen leads to services screen 906, which, as described above, allows selection of various sources of download information, which, once selected, is automatically downloaded in step 907.

[0087] In one modification of the controller 14, the pulley 34 can incorporate a hard stop component 36, which is configured and positioned to contact a hard stop component 37a attached to the base plate 42, as shown in FIG. 20. The two hard stops 36, 37a prevent the pulley from rotating beyond the hard stop 37 on the base plate. This mechanical stop thus limits the rotational movement of the pulley 35 in the direction of compression, and therefore limits how tight the wrap 12 can be tightened around the patient's limb. It can be appreciated that the amount of movement of the wrap 12 is based on the amount of movement of the strap 20 to which the wrap is connected, or the amount the strap is wound around the pulley 34. This distance of movement, in turn, is a function of the circumference (and therefore diameter) of the pulley. The mechanical stops 36, 37a prevent the pulley from rotating more than 360 degrees, so the maximum distance the strap 20 can be pulled by the pulley 24 is less than the circumference of the pulley. In one particular embodiment, the pulley can have a diameter of 0.5 inches (0.5 x 25.4 mm), resulting in a maximum travel of the pull strap of less than about 1.5 inches (1.5 x 25.4 mm). This amount of travel is sufficient to create a compressive force on the patient's cuff that exceeds the desired maximum compressive force, which can be, for example, 9 lbf (9 x 4.448 N) in one particular embodiment.

[0088] The controller may further include a switch or sensor 37b that corresponds to a "home" position for the strap 20, meaning the position when the strap 20 is extended to its maximum from the pulley 20. In this "home" position, the wrap 12 engages with the D-ring 22 attached to the strap 20, and at the end of the treatment cycle, the pulley, and thus the wrap, is returned to this "home" position. The pulley stop 38 may be in the form of a tab that engages with the switch or sensor 37b when the strap and wrap are in this "home" position. Thus, the switch 37b may be connected to the microprocessor 52 and to the motor controller 53 to automatically shut off the motor 32 when the pulley is in the "home" position. Alternatively, the microprocessor may issue a command to the motor controller in response to receiving a signal from the switch 37b.

[0089] In a further feature, the pulley 34 can be configured so that the amount of pulley rotation can be accurately determined by a rotary encoder, such as the encoder 39 mounted on the base plate 42 shown in FIG. 20 . Accordingly, the pulley 34 can include encoder markings 38 that can be detected and counted by the rotary encoder 39. The encoder markings shown in FIG. 20 are merely exemplary, as it is contemplated that a large number of encoder markings will be provided on the pulley to allow for extraction of a measurement of the degree of pulley rotation. Thus, in one particular embodiment, the pulley 34 can be provided with 1,500 encoder markings, with the rotary encoder 39 being able to distinguish between finely spaced markings. Note that any rotary encoder that can be mounted within the envelope of the device 10 and that is capable of sensitively measuring the amount of pulley rotation from a home position is contemplated, including magnetic, optical, and mechanical encoders. In another embodiment, the encoder can be associated with the drive shaft of the motor 32 prior to the transmission 33. In that embodiment, the encoder can have fine resolution because the motor is rotating faster than the pulley 20 because the pulley is slowed down by the transmission.

[0090] The encoder 39 communicates with the microprocessor 52 and provides a signal or pulse to the microprocessor each time an encoder marking is passed. The microprocessor is configured to count the pulses received from the encoder during movement of the pulley in the direction of compression, i.e., the direction that tensions the strap 20. The pulse count can be used to accurately determine the neutral or start position for the compression cycle and the position where compression stops and the wrap 12 is released from the patient's limb.

[0091] The pulse count is automatically reset to 0 when pulley 24 is at "home." In particular, when stop 36 engages switch 37b, the microprocessor or motor controller can reset the pulse count, if any, to identify the home position.

[0092] The encoder 39 facilitates applying pretension to the wrap 12 in anticipation of a compression treatment protocol. Thus, in one embodiment, the pretensioning steps 409-413 in the flowchart of FIG. 14 can be accomplished according to the steps shown in the flowchart of FIG. 21, which are performed by the microprocessor 52 and / or motor controller 53. Thus, the pretensioning step 409 in FIG. 14 begins with establishing a starting pulley position at step 1000 in FIG. 21. In this step, the motor 32 operates in the "unwind" direction (i.e., counterclockwise in FIG. 20), thereby moving the stop 36 of the pulley 34 toward the switch 37b. Once the stop contacts the switch, the starting position of the motor and pulley is established, and the microprocessor (or controller) sets the number of encoder pulses to 0. From this initial home position, any rotation of the pulley in either the "winding" or "tightening" direction (i.e., clockwise in FIG. 20) will increase the pulse count, and any rotation in the opposite direction will decrease the pulse count. In this regard, the microprocessor knows the direction of rotation of the motor: clockwise (increases count) or counterclockwise (decreases count). Once the home position is established, the motor is energized for rotation in the tightening (clockwise) direction in step 1001. The motor is rotated for a predetermined time, such as 150 milliseconds, after which the force exerted by the strap on the patient is measured. As mentioned above, force can be measured as a function of motor current, which means that the motor must be rotating at the time of measurement. Furthermore, due to hysteresis effects in the motor, there is a 150 millisecond delay in the initial force measurement because an accurate count reading cannot be obtained immediately. Alternatively, force can be measured with the load cell described above, which can be done when the motor is rotating or stopped.

[0093] In step 1003, the measured force is evaluated to determine whether it exceeds a desired pretension load. In the illustrated embodiment, the pretension load is set to 3 lbf (3 x 4.448 N), which has been determined to be an optimal compression force as a baseline for the continuous compression protocol, which does not restrict blood flow or cause user discomfort, yet ensures that the cuff remains in position on the patient's limb. If the load is found to exceed the desired pretension load, in step 1004, a message is displayed on screen 15 indicating that the straps are too tight. In that case, control passes to calibration steps 1005-1008, where in step 1006, it is determined whether the pulley is at the beginning of the home position set in step 1000; if not, in step 1007, the motor is operated in the reverse (loosening) direction to return the pulley to its home position. Next, in step 1008, the user, patient, or healthcare professional adjusts the wrap at the D-ring, and specifically loosens the wrap at the D-ring, as reflected in step 404 of the flowchart in Figure 14. Once the straps are adjusted, the pretensioning steps 1001-1003 are performed again.

[0094] If, after the predetermined time in step 1002, the measured force is less than the pretension (i.e., 3 lbf (3 x 4.448 N)), control passes to step 1009, where the pulley is rotated in increments to tighten the strap until the pretension (3 lbf (3 x 4.448 N)) is reached. As the pulley rotates, encoder pulses are counted, and in step 1010, the pulse count at pretension is stored in the microprocessor and / or controller memory as the value PTP (pretension position). The microprocessor 52 and / or motor controller 53 now know the angular position of the pulley at the baseline or pretension. The microprocessor and / or motor controller controls the rotation of the motor during the compression cycle to return the pulley to PTP at the end of one cycle and the beginning of a new cycle.

[0095] The next step in the calibration and pretensioning process is to determine whether the wrap 12 is too loose on the patient / user. If the wrap is too loose, the device will not be able to produce the desired compression needed to perform the desired function of the device, such as DVT protection. Therefore, in step 1011, the motor is again activated to rotate in the compression direction (clockwise) starting from pretension and PTP. In step 1012, the motor is rotated for a predetermined time, such as 150 ms, after which the tension is measured in the manner described above. In step 1013, the measured force is compared to a desired full compression force known to produce the desired compression, such as 9 lbf (9 x 4.448 N). If the measured force is less than the desired full compression force, the wrap is determined to be too loose, and a message to that effect is displayed in step 1014. Control then returns to calibration steps 1005-1008, allowing manual readjustment of the wrap at the D-ring. Calibrating and pretensioning then begins again at step 1000 .

[0096] If the result of step 1013 is that the measured force is less than the desired maximum compression force (i.e., 9 lbf (9 x 4.448 N)), then in step 1014 the motor is rotated incrementally until the measured force reaches the desired value. In step 1015, the number of encoder pulses accumulated to reach the desired maximum compression force is stored in memory as the value FCP (full compression position). The microprocessor and / or motor controller now knows the angular rotation of the pulley that corresponds to the desired maximum compression force to be applied to the patient. This value FCP is used by the microprocessor and / or motor controller during the compression protocol to determine when to reverse the motor to release the compression applied by the wrap to the patient's limb. In step 1016, a patient-specific value BCI (Body Compression Index) is calculated as the difference between the number of encoder pulses at full compression (FCP) and the number of encoder pulses at the pretension position (PTP), i.e., BCI=FCP-PTP. The BCI value is used by the microprocessor and / or motor controller to determine the amount of forward (tightening or compressing) and reverse (relaxing) rotation during the compression protocol to ensure that the compression force remains within the desired range, i.e., the range between pretension and maximum compression force.

[0097] BCI is a patient-specific value that is a function of the patient's limb anatomy, such as limb circumference and muscle and soft tissue density. Thus, a typical male patient may have a BCI of 600, while a patient using a larger cuff may have a BCI of 650. This difference is illustrated graphically in Figures 22A-22B. In the example of Figure 22A, the PTP for a particular patient is 300 encoder pulses from the pulley's home position; therefore, by the time the wrap reaches a pretension compression of 3 lbf (3 x 4.448 N), the pulley rotates past the 300 encoder marking 38 on the pulley. As the motor and pulley continue to rotate, the pulley reaches a point of maximum compression (9 lbf (9 x 4.448 N)) at an FCP of 900 pulses. The difference of 600 (900 - 300) is the BCI for that patient.

[0098] On the other hand, because the patient in the example of FIG. 22B has larger and / or denser limbs, the number of pulses corresponding to the amount of angular rotation of the pulley to reach a pretension of 3 lbf (3 x 4.448 N) is fewer than for the patient in the example of FIG. 22A. For this patient in FIG. 22B, the point of maximum compression (9 lbf (9 x 4.448 N)) is also at an FCP of 900. Therefore, the BCI for this second patient is 650 (900 - 250), which is more than the BCI for the first patient. This means that the motor rotates longer from the pretension position to reach maximum compression for the second patient than it did to reach compression for the first patient.

[0099] The BCI can be used during the compression protocol to account for deviations. For example, the patient's limb may expand during treatment, which can cause changes in PTP and FCP as a function of total pull strap travel, as shown in Figure 23A. The device can continuously monitor the applied force and determine if the amount of pulley rotation and pull strap travel required to reach the pretension (3 lbf (3 × 4.448 N)) decreases, indicating that the patient's limb has expanded and that expansion exerts an opposing pressure, causing the measured force to exceed the pretension. In this situation, the pretension position (PTP) may shift to the left in Figure 23A relative to the calibration position shown in Figure 22A for the same patient. However, because the BCI remains the same, the compression cycle is guaranteed to occur over the same pulley rotations corresponding to a 600 pulse count BCI. The BCI therefore provides a mechanism for adapting the compression cycle's behavior to the patient's physiological changes and maintaining pretension and maximum compression.

[0100] As shown in FIG. 23B, the wrap can be loosened during the compression protocol, causing the BCI band to move to the right in FIG. 23B relative to the calibration position shown in FIG. 22A. When the FCP reaches the maximum pulley rotation, which in one example may be 2000 pulse counts, a determination can be made that any compression is disabled and the wrap is too loose for the patient. In that case, a warning can be displayed on the device screen 15 along with an audible warning to alert the healthcare professional or user that attention to the device is required. Similarly, if the wrap becomes too tight, such as by the patient tightening the wrap, the BCI band will move to the left in FIG. 23C, causing the PTP to reach the home position. At that position, a visual and audible warning can be generated by the device to alert the user or healthcare professional that immediate attention to the compression device is required, as further tightening of the wrap could pose a risk of injury to the patient.

[0101] The flowchart of Figure 24 illustrates one firmware or software program flow for performing DVT compression, which may be implemented in step 418 of Figure 14 or step 520 of Figure 15. Steps 1021-1022 verify that a genuine compression wrap is engaged with the D-ring of the controller. If not, control passes to steps 1023-1024, where the user or medical professional attaches the appropriate wrap to the device. Note that these steps, i.e., verifying the wrap, can occur early in the process, as illustrated in the flowcharts of Figures 14-15, and each time a DVT compression protocol is initiated.

[0102] If a suitable strap is found, the microprocessor and / or motor controller activates the motor in step 1025, whereby the motor now operates at its 100% PWM state to tighten the wrap. As shown in step 1026, as long as the measured compression force is below the desired maximum force (in this case 9 lbf (9 × 4.448 N)), and as long as the FCP is less than the maximum possible encoder pulse count (2000 in one example), encoder pulses are counted in step 1027. As the motor is running and the wrap is tightened around the patient's limb, the encoder pulse count is stored as the value tempFCP. When the motor is activated in step 1025, the value of tempFCP is set to 0 and counting begins. If the value of tempFCP reaches the maximum encoder pulse count, the strap is determined to be too loose, as described in connection with FIG. 23B. If this determination is made, an error message is displayed in step 1029 and control passes to steps 1030-1033, which are the same as steps 1005-1008 described above in Figure 21. Notably, these steps allow the user or medical personnel to correct the loose strap condition.

[0103] If the value of tempFCP has not reached the maximum encoder pulse count, the strap is at least not too loose, and therefore the motor continues operating under the assumption that the maximum compression force has not been reached (step 1026). Once the maximum compression force is measured, the motor is de-energized for a predetermined delay (e.g., 1 second) in step 1027, and a value deltaBCI is calculated and stored as the difference between the current encoder pulse count and the BCI determined in the calibration step described above. Next, in step 1034, the motor is reversed to loosen the wrap from the maximum compression force, and a value tempPCP is stored as equal to the value PCP determined in the calibration step described above. If it is determined in step 1035 that the current encoder pulse count is greater than the value deltaBCI calculated in step 1027, then the value tempPCP is decremented in step 1036. As long as the conditions of step 1035 are met, and as long as the value of tempPCP is greater than zero in step 1037, the motor continues to rotate and the value of tempPCP is continually decreased by the processor. However, if the value of tempPCP reaches zero in step 1037, the wrap is too tight on the patient. A message is displayed in step 1038, and control passes to the calibration steps 1030-1033, where adjustments to the wrap are made as described above.

[0104] On the other hand, if the motor properly tightens a properly applied wrap, the value of tempPCP will not reach zero, and the encoder pulse count will eventually reach the value of deltaBCI in step 1035. At that time, the motor will have fully rewound the wrap to its pretensioned position, and the motor is turned off in step 1039. The processor then returns control to the start of DVT compression in step 1020 in step 1040, beginning another cycle of the DVT compression protocol. It can be appreciated that each of the steps shown in the flowchart of FIG. 24 are repeated with each compression cycle to ensure that the wrap is properly engaged and functioning. Alternatively, the initial verification steps 1021 and 1022 can be limited to the initial start-up of the compression device. However, testing of wrap tightness and looseness should remain in the program sequence to account for variations during a given DVT compression procedure.

[0105] The wrap 12' of the compression device 10 can be modified, as shown in FIGS. 25-27, to facilitate positioning the device on a patient's limb. As shown in FIG. 25, wrap 12' can be replaced with wrap 1200, which can be formed of the same material and have the same overall length as wrap 12' to encircle a portion of the patient's body, typically a limb. Wrap 1200 includes a portion 1202, which can generally correspond to flap 17' of wrap 12', in that an attachment structure 40' is attached to one end of portion 1202. Similarly, flap 17', portion 1202, is positioned between the patient's skin and a controller 14' (FIG. 27) attached to the attachment structure 40'. As shown in FIG. 25, portion 1202 of wrap 1200 terminates at end 1204 of slot 1206, which is configured to receive the opposite end 1210 of the wrap in a loop, as shown in FIG. 26. Thus, slot 1206 allows wrap 1200 to be temporarily attached to a patient's limb, such as the leg shown in FIG. 26, before a controller is attached to the wrap. This feature facilitates initial placement of compression device 10 on the patient, as wrap 1200 and mounting structure 40' can be optimally positioned on the patient's limb before engaging the controller. This feature also allows for easy removal and replacement of the controller, even when the wrap is engaged with the patient, without having to remove the entire device, wrap and all, from the patient.

[0106] As shown in FIG. 27, the controller 14' can be attached to the wrap by engaging it with the attachment structure 40' as described above. The controller engages the attachment structure as shown in FIG. 27 and pivots toward portion 1202, fully extending the pull strap 20. In this configuration, the D-ring 22 is positioned directly over the slot 1206, around which the end 1210 of the wrap is looped. The loop can be removed, and the end 1210 can be threaded through the D-ring 22, still extending through the slot 1206. Once the end 1210 is threaded through the slot, the wrap will hold its position on the patient's limb as it is threaded through the D-ring and looped around it. The end 1210 can be tightened as needed to provide initial attachment tension for the wrap, as described above.

[0107] Strap 1200, and particularly portion 1202, is configured to provide a predetermined distance D between attachment structure 40′ and slot 1206, as shown in FIG. 25 . This distance corresponds to the extended length of pull strap 20 relative to controller 14′, which allows D-ring 22 to be aligned with slot 1206, as shown in FIG. 27 . In one particular embodiment, this distance D is 4.92 inches (4.92 × 25.4 mm), and the distance from attachment structure 40′ to the edge of the wrap at end 1204 is 5.75 inches (5.75 × 25.4 mm). This dimension not only allows for proper orientation of the D-ring relative to the slot, but also avoids issues with portion 1202 crimping when pull strap 20 is retracted during a compression cycle. Wrap portion 1202 engages pull strap 20 by looping end 1210 through both D-ring 22 and slot 1206. Thus, when the pull strap is retracted, it pulls on the end loop 1210, thereby reducing the effective diameter of the wrap 1200 and causing compression. Retraction of the pull strap also pulls the end 1204 of the portion 1202 toward the controller 14'. If the portion is too short, the portion will tend to bunch up under the controller, thereby interfering with the compression applied to the patient. In the illustrated embodiment, distance D allows portion 1202 to bunch outside of the controller in a way that does not change or interfere with the compressive force applied to the patient.

[0108] The present disclosure provides an alternative approach for pretensioning a patient's strap before initiating a new compression cycle. As mentioned above, patient compliance is necessary, meaning that the patient must wear an active DVT cuff for the prescribed amount of time to avoid DVT or other complications. In a hospital setting, a caregiver is responsible for activating and initializing the controller for the presently disclosed DVT cuff and for comfortably applying the cuff to the patient. In an ideal environment, the caregiver would set the DVT cuff to the optimal tightness or pretension once at the patient's location, and that initial setting would be overridden each time the patient applies the cuff. However, in most cases, a patient's cuff tightness changes over time. For example, one common secondary issue with bedridden recovering patients is the development of edema, when limbs swell due to fluid accumulation. In such cases, the previous DVT cuff setting may become too tight. Conversely, for patients undergoing DVT compression procedures, the previous DVT cuff setting may become too loose as the edema is treated and swelling may decrease. This change in tightness can also occur during a compression cycle. In each case, the caregiver must take the time needed to recalibrate the DVT cuff tightness for the particular patient. In a typical hospital setting, the time required to recalibrate a patient's DVT cuff exacerbates the workload of an already overburdened caregiver. In some cases, proper care and even use of the DVT cuff tightness can be compromised.

[0109] The present disclosure provides a streamlined and accurate process for establishing pretension in a DVT cuff, as many times as necessary throughout a patient's compression protocol. As described above, the wrap 12, 12', 1200 is tightened by a pull strap 20 connected to the strap by a D-ring 22. The pull strap 20 is wound onto and unwound from a pulley 34, which is driven to rotate by a motor 32. Once the wrap / strap 12, 12', 1200 is wrapped around the patient's limb, the pretensioning process begins at the "slack-tight" position of the pull strap and pulley, which represents the position at which the DVT cuff wrap 12, 12', 1200 is wrapped with optimal initial tightness on the patient's limb. For the DVT cuff wraps of the present disclosure, the slack-tight position is a predetermined number of rotational steps of the motor, and therefore the pulley, from the "0" position, where the pull strap 20 is fully unwound. In one embodiment, the maximum number of encoder steps for a pulley rotation is 1100 steps. However, to ensure proper motor performance throughout forward and reverse motor / pulley rotation, the number of usable steps is preferably 80% of the maximum, or 880 steps. The slack take-up position can be 28-32% of the maximum, or preferably 325 encoder steps from the 0 position, to provide adequate rotation to loosen the wrap as needed.

[0110] The general system flow of the software controlling the operation of the wrap 12, 12', 1200 is shown in the flowchart of FIG. 28. In step 1300, power is turned on to the controller 14, 14', and the software begins a boot-up routine to ensure the controller is properly functioning and configured. Once the boot-up process is complete, program flow continues to step 1302, where the pulley's take-up slack position is verified and established. According to the flowchart of FIG. 29, in step 1304, a determination is made as to whether the take-up slack position flag stored in the controller's memory is set to "false," indicating that the motor / pulley has not been moved to the take-up slack position. If so, flow continues to step 1305, where the pulley is moved to its home or fully extended position and the encoder pulse count is set to 0, establishing a baseline for future readings of the encoder 39 as the pulley rotates from its home position. It can be appreciated that this calibration occurs before the wrap 12, 12', 1200 is wrapped around the patient's limb. The goal is to ensure that the pull strap 20 is fully unwound before calibrating the take-up slack position. Next, in step 1306, the pulley is rotated to the take-up slack position, which slightly retracts the pull strap 20. In certain embodiments, the take-up slack position is a partial pulley rotation, such as 325 steps from the home position, as described above. The take-up slack position flag is then set to "true," causing the calibration subroutine to exit at next step 1310. It should be appreciated that at the end of the calibration process, the pulley is in the take-up slack position, where the pull strap 20 is slightly retracted, and the take-up slack position flag is set to true, meaning the take-up slack position has been set.

[0111] Returning to the flowchart of FIG. 28 , once the slack-tightening position for the controller has been established, in the next step 1310, the controller is attached to the wrap 12, 12′, 1200 as described above. Once the controller is attached to the DVT cuff strap, the strap is authenticated in step 1311 and verified in step 1312 to ensure that the proper controller / strap combination is used, as described above. Once the strap is verified, the DVT cuff strap is pretensioned in step 1312 according to the flowchart of FIG. 30 . The pretension adjustment is based on the compressive force generated by the wrap when it is tightened by the motor on the patient's limb, and also based on the encoder pulse count, which indicates the amount of rotation of the pulley 34. In one feature of the DVT cuff disclosed herein, the force generated by the compression device is determined from the current load on the motor 32. As a result, the compressive force being applied by the DVT cuff can only be determined while the motor is running.

[0112] In the pretensioning protocol 1320 of FIG. 30, in step 1321, the pulley 20 is moved to its home position and the encoder pulse count is set to 0. In step 1322, the slack tightening position flag is set to "false" to indicate that the pull strap is no longer in the slack tightening position. In step 1323, energy is applied to the motor, and in step 1324, the force exerted by the patient's wrap is measured after a predetermined delay required to determine the motor current load. In a specific embodiment, the delay is 150 milliseconds. In step 1325, the measured force at the time delay is compared to a maximum threshold force, "loosen force," which indicates that the strap is too tight. In a specific embodiment, "loosen force" is 7.5 lbf (7.5 x 4.448 N). For example, FIG. 31 shows the progression of the encoder pulse count as the pulley rotates relative to the target zone of DVT cuff operation for DVT prophylaxis. The target zone is defined by a target minimum number of encoder pulse counts, TL, and a target maximum number, TH. This zone represents the optimal starting position of the pulley and pull strap for effective DVT prophylaxis compression, and therefore strap tension. The goal of this pretensioning logic is to ensure that the force generated by the wrap and the number of encoder counts fall within the target zone.

[0113] Returning to FIG. 30, a "yes" response to the conditional statement in step 1325 corresponds to graph position *1 in FIG. 31, where the pulley has not yet rotated toward the target zone, but the force generated by the DVT cuff exceeds the threshold or "loosen" force. In step 1326, if the "loosen force" has not been exceeded, the encoder pulse count is compared to the target minimum TL. As discussed above, the target minimum TL corresponds to the minimum amount of pull strap 20 wound onto pulley 34 for proper starting positioning of the pulley and pull strap. Furthermore, the measured force is compared to a desired force, "tighten," which represents the optimal starting force or pretension for the DVT cuff within the target zone of FIG. 31. A "yes" response to the conditional statement in step 1326 corresponds to position *2 in Figure 31, which means the DVT cuff has reached the optimal starting force with very few motor / pulley rotational steps for effective DVT cuff operation. If the "loosen force" is exceeded (step 1325), or if the encoder pulse count is less than the target minimum when the measured force equals the "tighten" force, the "tighten flag" is set to a value of "1" in step 1327, indicating that the straps 12, 12', 1200 are too tight on the patient to allow for proper preventative compression. In such cases, the pretensioning protocol returns to step 1302 to recalibrate the cuff slack / tighten position (Figure 29). At this time, caregiver intervention may be required to adjust the wrap on the patient's limb, such as by loosening the strap end loops 24 at the D-rings 22.

[0114] A "no" response to the conditional statements in steps 1325 and 1326 means that the maximum force has not been exceeded and the encoder pulse count is not below the target minimum TL. The pretension logic then proceeds to determine whether the patient cuff strap is too loose. In step 1328, a determination is made as to whether the measured force is less than or equal to the "tighten" force and whether the encoder pulse count is greater than the target maximum TL. This condition corresponds to position *3 in FIG. 31, where the pulley is rotating outside the target zone but the measured force has not yet reached the desired "tighten" force. In that case, the "tighten flag" is set to a value of "2," indicating that the patient strap 12, 12', 1200 is too loose. Control then returns to the calibration protocol in step 1302. Again, caregiver intervention may be required to adjust the engagement of the end loop 24 at the D-ring 22.

[0115] If a determination is made in step 1328 that the measured force is greater than the "tighten" force and the encoder pulse count is less than or equal to the target minimum TL, the flowchart proceeds to step 1330. In that step, the motor continues to operate until the measured force reaches the "tighten" force. In step 1331, a determination is made as to whether the encoder pulse count has reached the maximum number of steps, corresponding to position *4 in FIG. 31. If this conditional statement is answered affirmatively, the strap is determined to be too loose, and control passes to step 1329, described above. However, if the conditional statement in step 1331 is answered negatively, step 1304 determines that the encoder pulse count is within the target zone, corresponding to position 5* in FIG. 31. If the measured force and encoder pulse count place the strap within the target zone, the strap is properly calibrated and is ready to provide DVT prophylaxis to the patient. In the preferred embodiment, the minimum force for the target zone is 4.0 lbf (4.0 x 4.448 N). Any force below this value means the strap is too loose on the patient.

[0116] In step 1341, the controller may operate in a manner similar to step 1016 (FIG. 21) described above. More specifically, a value "cml" is calculated, which corresponds to the number of encoder pulses for reversing the motor or loosening the strap during a compression-release cycle. The number of encoder pulses determined in step 1331 sets the maximum force, and the number of encoder steps "cml" determines the pretension force, thus bounding the forward and reverse motor rotation. Once the calculation is made, in step 1342, the motor is reversed and the motor and strap are moved to the "cml" position. Next, in step 1350, the DVT compression process begins.

[0117] If the encoder pulse count and force measurements are outside of the target zones, such as positions 1*, 2*, 3*, and 4*, caregiver intervention is required to readjust the patient's wrap. If the straps are too tight at positions 1* or 2*, the value of the "tighten flag" is set to "1." If the straps are too loose at positions 3* or 4*, the value of the "tighten flag" is set to "2." When process flow proceeds to calibration step 1302, the "tighten flag" is evaluated in step 1332 to determine which message path is applicable. Specifically, if the straps are too loose, the message path generates a "tighten straps" message in the controller. Similarly, if the straps are too tight, the message path generates a "loosen straps" message. Simultaneously, the processor can generate a warning signal to draw the caregiver's attention to the error condition message.

[0118] In one embodiment, the processor can indicate to the caregiver the degree of loosening or tightening required to place the compression cuff in the target zone. This determination is based on the encoder pulse count, as reflected in conditional statements 1333 and 1334. Specifically, the conditional statements determine the difference between the target encoder pulse count value and the measured encoder pulse count value. For straps that are too loose, conditional statement 1333 evaluates the difference between the target value at position 5* (FIG. 31) of the target zone and the current encoder pulse count at positions 1* or 2*. If the difference is less than 100 counts, the strap only needs to be tightened toward the "half position line" identified on the strap itself. Alternatively, if the count difference is greater than 100, the caregiver is instructed to tighten the strap to the "full position line" on the strap. For straps that are too tight, a similar evaluation is made in conditional statement 1334 based on the difference between the target value at position 5* and the current encoder pulse count at positions 3* or 4*. If so, the strap is loosened toward the full or half position line on the strap. In one embodiment, the target value at position 5* is 530. Then, for conditional statement 1333, the decision threshold is at 530-100=430, and for conditional statement 1334, the threshold value is 530+100=630.

[0119] It can be appreciated that the controller and associated software can continuously monitor the force applied by the wrap to the patient via the current driving the motor. If the sensed force falls outside of the desired minimum and maximum forces, an alarm can be sounded to notify the caregiver that an adjustment is needed. The controller can then immediately release the cuff toward the pulley home position, deenergize the motor, and provide a message to the patient indicating whether the straps are too loose or too tight.

[0120] The present disclosure should be considered as illustrative and not restrictive in character, it being understood that only certain embodiments have been provided and that protection is desired for all alterations, modifications, and further applications that come within the spirit of this disclosure.

Claims

1. 1. A compression device, comprising: a flexible, elongated wrap sized to encircle a patient's limb, the wrap including a first end and an opposite second end configured to form a loop to adjust the length of the wrap from the first end to the loop, the first end including an end portion defining a slot therethrough sized to receive the second end of the wrap to form the loop; Controller and the controller comprising: an electric motor driving the rotating pulley; a current sensor for sensing a current driving the electric motor; an encoder for generating a pulse for each predetermined amount of rotation of the pulley; a pull strap attached to the pulley, the pull strap being wound onto the pulley when the pulley is rotated in a compression direction by the motor and unwound from the pulley when the pulley is rotated in a release direction, the pull strap being configured to releasably engage the second end of the wrap; a processor configured and operative to control operation of the motor according to a predetermined compression protocol to rotate the pulley in the compression direction to wind the pull strap onto the pulley to create a predetermined compressive force on the patient's limb surrounded by the wrap, and to rotate the pulley in the release direction to unwind the pull strap from the pulley to decrease the compressive force on the limb; the processor further comprises: determining a force exerted by the lap as a function of the sensed drive current for the motor; generating an encoder pulse count corresponding to a count of the number of pulses generated by the encoder as the pulley rotates to determine a travel distance corresponding to a distance the pull strap is wound onto or unwound from the pulley; stopping rotation of the pulley in the compression direction when the pulse count reaches a predetermined pulse count value indicative of a maximum desired compression for the predetermined compression protocol; establishing an optimal pretension in the wrap when the wrap is wrapped around the limb of the patient, the pretension corresponding to a slack-tightening position of the wrap and a target force to be applied by the wrap; A compression device configured and operative to then initiate a DVT compression prophylaxis protocol on the patient, wherein the wrap is repeatedly tightened from the slack tightened position and relaxed back to the slack tightened position.

2. 2. The compression device of claim 1, wherein the processor: providing energy to the electric motor to wind the pull strap around the pulley to tighten the wrap around the patient's limb; after a time delay, measuring the force exerted by said lap during said time delay; if the force exceeds a maximum threshold force value, the strap generates an overtightness notification; if the force does not exceed the maximum threshold force value, comparing the encoder pulse count during the time delay with a target minimum pulse count value; a compression device configured and operative to establish an optimal pre-tension for the wrap by making a determination as to whether the strap is too tight by generating a notification to the patient that the strap is too tight if the encoder pulse count during the time delay is less than the target minimum pulse count value.

3. 2. The compression device of claim 1, wherein the processor: providing energy to the electric motor to wind the pull strap around the pulley to tighten the wrap around the patient's limb; after a time delay, measuring the force exerted by said lap during said time delay; generating a notification that the strap is too loose if the force is less than an optimum force value and the encoder pulse count during the time delay is greater than a target maximum pulse count value; if the force is less than an optimum force value and the encoder pulse count during the time delay is less than the target maximum pulse count value, then further operating the motor until the measured force equals the optimum force value; If the encoder pulse count when the measured force is equal to the optimum force value is equal to a maximum encoder pulse count value, a notification is generated that the strap is too loose. and determining whether the strap is too loose for the patient by determining whether the strap is too loose for the patient. Compression device.

4. 2. The compression device of claim 1, wherein the processor: providing energy to the electric motor to wind the pull strap around the pulley to tighten the wrap around the patient's limb; after a time delay, measuring the force exerted by said lap during said time delay; if the force exceeds a maximum threshold force value, the strap generates an overtightness notification; if the force does not exceed the maximum threshold force value, comparing the encoder pulse count during the time delay with a target minimum pulse count value; generating a notification that the strap is too tight if the encoder pulse count during the time delay is less than the target minimum pulse count value; generating a notification that the strap is too loose if the force is less than an optimum force value and the encoder pulse count during the time delay is greater than a target maximum pulse count value; if the force is less than an optimum force value and the encoder pulse count during the time delay is less than the target maximum pulse count value, then further operating the motor until the measured force equals the optimum force value; a compression device configured and operative to establish an optimal pre-tension for the wrap by making a determination as to whether the straps are too tight or too loose for the patient by generating a notification that the straps are too loose if the encoder pulse count at which the measured force equals the optimal force value equals a maximum encoder pulse count value.

5. 1. A method of actuating a compression wrap around a patient's limb to initiate deep vein thrombosis (DVT) compression prophylaxis, the compression wrap including a controller for controlling an electric motor that winds and unwinds a pull strap to tighten and loosen the compression wrap around the limb, the method comprising: prior to wrapping the compression wrap around the limb of the patient, operating the electric motor to wind up the pull strap from a home position to a slack-tight position corresponding to a desired initial tension in the compression wrap when the compression wrap is first wrapped around the limb; wrapping the compression wrap around the limb of the patient such that the electric motor is in the slack tightening position; providing a drive current to the motor for a predetermined period of time to first reel the pull strap back to the home position and then reel the pull strap up to tighten the compression wrap on the limb; At the end of the predetermined time period, transmitting the drive current and determining a compressive force applied to the limb as a function of the drive current; and determining the travel distance of the pull strap; comparing the compression force and the travel distance with a target zone of a target compression force range and a target travel distance range; if the measured compression force and travel distance are outside the target zone, operating the motor to rewind the pull strap to the home position to provide notification that the compression wrap is too tight or too loose around the patient's limb and to allow manual adjustment of the compression wrap on the patient's limb; if the measured compression force and travel distance are within the target zone, initiating a DBT compression prophylaxis protocol in which the pull strap is moved to the slack tightening position and the wrap is repeatedly rolled up from the slack tightening position and back up to the slack tightening position; The method includes:

6. 6. The method of claim 5, the target compressive force range is defined by a maximum force value and a minimum force value; the target movement distance range is determined by a maximum movement distance and a minimum movement distance; if the compression force exceeds the maximum force value, or if the compression force does not exceed the maximum force value but the travel distance is less than the minimum travel distance, the notification is that the step is too tight for the patient; If the compression force is less than the minimum force value and the travel distance is greater than the maximum travel distance, the notification is that the step is too gentle for the patient.

7. 7. The method of claim 6, if the compressive force is less than the minimum threshold force value and the movement is less than the maximum movement maximum force value, further operating the motor until the measured compressive force is equal to the minimum force value; The method generates a notification that the strap is too loose if the travel when the measured compressive force equals the minimum force value equals or exceeds the maximum travel distance.

8. 6. The method of claim 5, wherein the motor drives a pulley to which the pull strap is attached, the controller includes an encoder that generates a pulse for each predetermined amount of rotation of the pulley, and the step of determining the travel distance of the pull strap includes counting the number of pulses generated by the encoder when the motor rotates the pulley, and the target travel distance range is a range of a target number of pulses.

Images