Patent Application
20110066093
The present invention generally relates to compression devices, and more particularly to a portable, self-contained compression device having a flexible shaft that is rotatable to constrict a sleeve to apply compression on a limb.
Compression garments for applying compressive forces to a selected area of a patient's anatomy are used in many situations. For example, compression garments may be used to treat venous insufficiency or edema, to heal wounds, or to prevent deep vein thrombosis (DVT).
Many devices on the market and in the prior art provide compression by using one or more pneumatic bladders that encircle the leg or other limb(s). The bladders are inflated in a predetermined sequence and to a prescribed pressure at timed intervals. The device that controls the inflation typically employs an air pump or compressor and a number of valves that operate to direct the flow of air to the bladders. Conventional products use a sleeve containing such bladders. The sleeve is wrapped around the limb and the bladder(s) are inflated by a controller device that resides separately from the patient such as on the footboard of a bed, on the floor, or on a night stand. If the patient must move, the sleeve must be removed. In addition, while the sleeve is on the patient, the tubes connecting the bladder and controller device may become entangled with the patient's limbs and/or become a nuisance or safety hazard to caregivers and visitors who may be close to the bed.
There is a need, therefore, for an improved compression device.
In one aspect, a portable, self-contained compression device of this invention is wearable by a person for applying intermittent compression on a limb of the person. The device comprises a sleeve having a longitudinal axis and is adapted for placement on the limb. An actuator assembly on the sleeve comprises a flexible shaft operably connected to the sleeve and extending generally parallel to the longitudinal axis of the sleeve. The shaft is flexible to allow for conformance of the shaft to the limb when the sleeve is on the limb. The actuator assembly further comprises an actuator for rotating the flexible shaft in a first direction to constrict the sleeve to apply compression on the limb and for rotating the flexible shaft or allowing the flexible shaft to rotate in a second direction to relax constriction of the sleeve to relieve compression on the limb.
In another aspect, the invention involves a method of applying compression on a limb of a person using a portable, self-contained compression device completely wearable by the person. The method comprises placing on the limb a sleeve having a flexible shaft connected to the sleeve that allows for conformance of the flexible shaft to the limb. The method further comprises rotating the flexible shaft in a first direction to constrict the sleeve to apply compression on the limb and rotating the flexible shaft or allowing the flexible shaft to rotate in a second direction to relax constriction of the sleeve to relieve compression on the limb. The flexible shaft is repeatedly rotated in the first direction and rotated or allowed to rotate in the second direction to apply intermittent compression on the limb.
In another aspect, a method of applying compression on a limb of a person using a portable, self-contained compression device completely wearable by the person comprises placing on the limb a sleeve having an actuator assembly on the sleeve. The actuator assembly includes a motor and a battery connected to the motor. The method further comprises moving a motor shaft of the motor via power from the battery in a first direction in which the motor shaft causes the actuator assembly to constrict the sleeve to compress the limb and generating electrical current by allowing the motor shaft to rotate in a second, opposite direction in response to a force on the sleeve from the compressed limb. The electrical current is used to charge the battery.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the drawings.
Referring to the drawings,
In general, the device 10 comprises a sleeve 20 adapted for placement on a limb L. The device 10 includes an actuator assembly, generally designated 30, for constricting the sleeve 20 to apply compression on the limb L. The compression device 10 is portable and self-contained because the actuator assembly 30 is supported on the sleeve 20 and has a portable power source such as a battery. Thus, a patient is not “tethered” to a stationary controller or an electrical outlet while wearing the device, thereby providing greater patient mobility.
The sleeve 20 may be sized and shaped for encircling different limb lengths. For example, the sleeve 20 may be knee-length, for encircling a leg L from the ankle to below the knee. In the illustrated embodiment, the sleeve 20 is thigh-length, for encircling a leg L from the ankle to above the knee. The sleeve 20 comprises a proximal (top) end 40, a distal (bottom) end 42, and opposite sides 44, 46. As shown in
The actuator assembly 30 comprises a controller 60 positioned near the proximal end 40 of the sleeve 20 and a flexible shaft 64 that extends generally parallel to the longitudinal axis A—A of the sleeve at a location generally between the two sleeve portions 50, 52. As described in further detail below, the flexible shaft 64 is connected to the sleeve 20 at locations along the length of the sleeve between a proximal end 66 and a distal end 68 of the shaft. The controller 60 comprises a housing 70 containing an actuator 74 and a control system 76. A portion of the controller housing 70 is broken away in
The actuator 74 rotates the flexible shaft 64 in a first direction (e.g., clockwise as viewed in
The actuator may comprise a small electric motor, also indicated 74. The motor may be a brushless design or may be a stepper type motor. An example motor has an electrical load between approximately 10 to 25 watts. Desirably, the motor 74 is capable of driving the flexible shaft 64 at a rate of 56 rotations per minute with 40 ounce-inches of torque. Motors with other operational parameters may be used.
The actuator 74 may include a gearbox (also designated 74) to reduce the required motor speed so that a much smaller motor may be used. The gearbox 74 may contain, for example, a simple, plastic-cased, plastic/nylon-geared, planetary reduction or a plastic-cased, plastic/nylon-gear train. The planetary reduction or gear train desirably allows the motor 74 to generate sufficient torque for a motor shaft operably linked to the flexible shaft 64 to rotate the flexible shaft to impart sufficient compression on the limb L. The gearbox 74 has a ratio that not only allows the motor 74 to sufficiently drive the flexible shaft 64 but also allows the flexible shaft to be unwound or reversed easily to relax constriction of the sleeve 20, which is desirable to allow the reverse spin of the motor to charge a battery, as described in more detail below.
The illustrated flexible shaft 64 extends along substantially all of the length of the sleeve 20 and is flexible to allow for conformance of the shaft to the limb L when the sleeve is on the limb. For example, the shaft 64 is flexible to conform to the curved shape of a calf muscle. The shaft 64 may have sufficient flexibility to conform to the shape of the leg L when the leg is bent at the knee (see
As shown in
Desirably, the springs 80, 82, 84 have successively decreasing spring rates from the distal end 68 of the flexible shaft 64 toward the proximal end 66 of the flexible shaft such that rotation of the shaft in the first direction causes sequential and gradient compression on the limb L. Desirably, the ankle spring 80 has a tighter, quicker wind than the calf spring 82, and the calf spring 84 has a tighter, quicker wind than the thigh spring. When the motor rotates the flexible shaft, the springs 80, 82, 84 first coil more tightly before applying substantial force tending to constrict the sleeve. When the flexible shaft 64 is rotated, the ankle spring 80 is wound tight first so that it is the first among the three springs 80, 82, 84 to constrict the sleeve 20. Upon further rotation of the flexible shaft 64, the calf spring 82 constricts the sleeve 20, and the thigh spring 84 follows. Slits 86 are formed in the first sleeve portion 50 so that sections 90, 92, 94 of the first sleeve portion 50 associated with each spring 80, 82, 84 may be constricted independently of each other. In other words, the sections 90, 92, 94 are independently movable circumferentially of the leg L with respect to one another. As a result, sequential constriction of the sleeve 20 occurs, and the maximum pressure applied by the sleeve increases progressively from the ankle spring 80 to the thigh spring 84.
The second sleeve portion 52 is connected at its inner side margin 52a to the flexible shaft by at least one bearing connection 100. In the illustrated embodiment, four bearing connections 100 are used. The connections 100 allow the flexible shaft 64 to rotate without winding the inner side margin 52a of the second sleeve portion around the flexible shaft. Although the connections 100 are free to rotate about the flexible shaft 64, the connections desirably maintain their general longitudinal position along the flexible shaft. The bearing connections 100 may have various configurations. For example, the connections 100 may comprise fabric loops, also indicated 100, which extend around the flexible shaft 64 and ends of which are attached to the second sleeve portion 52. Alternatively, the second sleeve portion 52 may be connected to one or more tubes (not shown) positioned over part or substantially all of the length of the flexible shaft 64. Other bearing connections 100 may be used.
The sleeve 20 may be releasably connected to the actuator assembly 30 so the actuator assembly may be used with disposable sleeves. For example, the controller housing 70 may be releasably mounted on the sleeve 20. In addition, the inner side margin 50a of the first sleeve portion 50 may be connected to the springs 80, 82, 84 by hook and loop fabric (not shown) or another type of releasable connection. Moreover, the inner side margin 52a of the second sleeve portion 52 may be releasably connected to the bearing connections 100 such as by hook and loop material (not shown). Alternatively, the springs 80, 82, 84 and/or the bearing connections 100 may be permanently attached to the inner side margin 50a of the first sleeve portion 50 and to the inner side margin 52a of the second sleeve portion, respectively. Thus, the flexible shaft 64 would be removable from the springs 80, 82, 84 and the bearing connections 100 on the sleeve. Such configurations allow the entire sleeve 20 or sleeve portions 50, 52 to be easily replaced. In addition, such releasable connections allow the sleeve 20 to be secured around a limb L by connection of the sleeve 20 to the flexible shaft 64, instead of by wrapping the outer side margins 50b, 52b around the limb and securing them in an overlapping fashion, as described above.
The control system 76 may be programmed to monitor feedback data from the actuator 74 and programmed to set operational parameters of the compression device 10 based on the feedback data. For example, the control system 76 may monitor venous refill time, venous refill volume, actuator current, actuator voltage, and/or actuator force. Feedback data may be collected by a motor monitoring system 120 that measures motor current. For example, the motor monitoring system may include a current shunt resistor (also indicated 120) placed in series with drive circuits of the motor, which will be understood by one having ordinary skill in the art. The resistor 120 is used to collect voltage measurements, which correspond to the amount of load supplied by the motor 74. The controller 60 is programmed to use these voltage measurements to set speed and torque of the motor 74. In addition, a load cell 122 may be used within the controller housing 70 to measure the torsional forces on the motor 74. For example, as shown in
Using the motor monitoring system 120 and/or the load cell 122, feedback data is collected during constriction of the sleeve 20 and/or during venous refill. To measure data relating to venous refill, a minimal amount of compression is maintained on the limb L at the end of a compression cycle, as controlled by the CPU 110 based on measurements received from the motor monitoring system 120 and/or the load cell 122. The minimal compression maintained on the limb L may comprise approximately 10 mmHg of pneumatic compression or about eight ounce-inches of torque on the flexible shaft 64. As blood returns to the limb L, the limb applies a force against the sleeve 20 that generates a small amount of reverse torque on the flexible shaft 64 and thus the actuator 74. An increase in effort to maintain the minimal amount of compression as the blood returns to the limb is measured by the motor monitoring system 120 and/or load cell 122 and recognized by the CPU 110 as venous refill data.
The increased effort may be measured in various ways. For example, the current shunt 120 may be used to measure the resulting higher current. The controller 60 recognizes the additional voltage across the shunt 120 as venous refill data. Alternatively, the controller 60 may recognize voltage created by the load cell 122 corresponding to the torsional and compressive forces of the motor and/or gearbox 74. If the load cell is used, the minimal compression on the limb L is maintained by locking the rotor of the motor so that forces (e.g., torque) experienced by the flexible shaft 64 are transmitted to the motor and/or gearbox 74 and sensed by the load cell 122. At the completion of venous refill, the controller 60 recognizes less voltage across the shunt 120 and/or from the load cell 122. The controller 60 then uses the venous refill data to calculate venous refill time and/or volume.
The control system 76 may set at least one operational parameter of the compression device 10 based on the monitored feedback data. For example, the control system 76 may set frequency of sleeve constriction, magnitude of sleeve constriction, or duration of sleeve constriction. For example, the CPU 110 may be programmed to set the operational parameters by comparing measured values from the motor monitoring system 120 and/or load cell 122 to stored target values for various compression therapy regimens. These operational parameters may be set at the end of each compression cycle (i.e., after each time the flexible shaft 64 is rotated or allowed to rotate in the second direction) or at other intervals.
The compression device 10 may also include at least one motion sensor 130 (e.g., accelerometer). The motion sensor 130 may be located anywhere on the device 10, but is shown in the illustrated embodiment within the controller housing 70 (
In another feature, the compression device 10 may include an expansion detection mechanism 140. The expansion detection mechanism is capable of detecting when the sleeve 20 is in a condition having a certain amount of irreversible expansion. In this regard, the life of the sleeve 20 may be deliberately limited because of the fiber design and construction of the soft sleeve material. As the fibers break down, the sleeve 20 may tear or stretch beyond acceptable limits. The expansion detection mechanism may comprise, for example, at least one sensor 142 (e.g., strain gauge sensor) applied to the surface of the sleeve 20 or woven into the sleeve fabric.
As shown in
Each sensor 142 may comprise a conductive/resistive coating (e.g., sprayed-on powdered carbon) or conductive/resistive fibers on the sleeve 20. The coating and the fibers are carbon-based and therefore offer a resistive electrical path through them. As the material of the sleeve 20 is stretched or torn, the coating and/or fibers of the sensors 142 permanently elongate and thus increase in resistance. The sensors 142 are oriented on the sleeve 20 along an axis of expansion (e.g., transversely to longitudinal axis A—A) to maximize their sensitivity to fiber tears of the sleeve material.
The conductive/resistive coating or fibers of each sensor 142 is electrically connected to resistance measuring circuits in the controller 60 via fully conductive, printed-on traces or printed circuits 146 on the sleeve 20. The printed circuits are fully conductive even when stretched out by a failing/tearing sleeve 20. As shown in
The result of this electrical design and construction is to allow continued electrical resistive measurement by the sensors 142 as the sleeve 20 begins to tear apart. As the sleeve 20 begins to tear apart, the combined system of the conductive/resistive coating or fibers of the sensors 142 and the fully conductive printed/woven conductors 146 measures a rapid increase in resistance. This substantial increase in resistance is measured by the controller 60 and recognized as a failing sleeve 20.
In another embodiment, the motor 74 is equipped with an optical encoder 150 used to detect sleeve expansion. The optical encoder 150 counts the number of rotations of the motor 74 during each constriction cycle of the controller 60. The rotations of the motor 74 are indicative of the number of revolutions of the flexible shaft 64 required to complete a compression cycle. The CPU 110 stores this data and averages the number of revolutions required per cycle. A new average is calculated beginning each time the controller 60 is re-started because the required revolutions is dependant on the particular application (e.g., orientation or tightness) of the sleeve 20 on the limb L and the specific installation of the sleeve on the flexible shaft 64. If the sleeve 20 begins to fail, the number of revolutions required to complete a compression cycle will increase. The CPU 110 may be programmed with an algorithm to recognize the increase in required revolutions and to signal the existence of the condition to the wearer, inhibit operation of the compression device 10 whenever the condition exists, or take any other required action.
In yet another feature, the controller 10 is capable of energy recovery. As the motor 74 executes a compression cycle, the motor draws power from the battery 116. More specifically, the controller 10 causes the motor shaft operably linked to the proximal end 66 of the flexible shaft 64 to rotate the flexible shaft in the first direction to constrict the sleeve 20 to compress the limb L. When the compression cycle is finished, the controller 60 allows the reverse force exerted by the springs 80, 82, 84 and/or the compressed limb L to cause the motor shaft to rotate in the second direction. This rotation in the second direction generates electrical current that is used to charge the battery 116. Thus, the motor 74 is used as a generator.
In one cycle of use, the compression device 10 is placed on a limb L by aligning the longitudinal axis A-A of the sleeve 20 with the limb L, wrapping the sleeve sides 44, 46 around the limb, and securing the sides in an overlapping fashion using the hook and loop fasteners 56. The controller 60 is then activated to provide signals to operate the actuator 74 to carry out a desired compression treatment regimen. The actuator 74 repeatedly rotates the flexible shaft 64 in the first direction (e.g., clockwise as viewed in
The compression device 10′ is used much the same way as the sleeve 10. However, instead of using springs, the device 10′ uses the elastic sections 110, 112, 114 to impart sequential, gradient compression.
Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
