Pneumatic compression devices and garments for the prevention of deep vein thrombosis

A pneumatic compression device for non-invasive external intermittent pneumatic compression system used as prophylaxis for reducing the incidence of Deep Vein Thrombosis (DVT). The system consists of a pneumatic compression pump, valves for control of air flow, a pressure sensor, and a controlling circuitry. The controlling circuitry receives input from the pressure sensor and switch ON/OFF one or more control valves based on the pressure sensor input to dynamically controlling the pressure of the regulated compressed air flow.

TECHNICAL FIELD

This description relates generally to medical devices and more specifically to devices for periodically compressing a part of a human body to improve circulation, and to prevent blood clots.

BACKGROUND

The technology of compressing a part of a body to improve circulation can be applied to several medical conditions, such as peripheral artery disease, venous insufficiency, lymphedema, and prevention of Deep Vein Thrombosis. Deep vein thrombosis (DVT) is a blood clot in a large vein, usually in the leg or pelvis. Sometimes the blood clot detaches from the site of formation and becomes mobile. If the circulating clot moves through the heart to the lungs, it can block an artery supplying blood to the lungs, resulting in pulmonary embolism. The disease process that includes DVT and/or pulmonary embolism is called venous thromboembolism (VTE). Each year in the United States, approximately 350,000-900,000 persons develop VTE, and of those, approximately 100,000 die. Additionally, 30%-50% of persons with lower-extremity DVT develop a long-term complication that causes swelling, pain, discoloration, and, in severe cases, ulcers in the affected limb.

It is therefore desirable to provide an effective, user friendly, and patient compliant pneumatic compression device and garment, including a system in order to achieve effective treatment, which are important components to promoting patient compliance and positive clinical outcomes.

SUMMARY

The present example provides a non-invasive external intermittent pneumatic compression system used as prophylaxis for reducing the incidence of Deep Vein Thrombosis (DVT). The system may consist of a pneumatic compression pump, valves for control of air flow, a pressure sensor, and an orifice. Also included is a method of operating the pneumatic compression pump. The system also includes a variety of breathable garments, including foot, calf-length, thigh-length, and the like, and a unique device for coupling the pneumatic compression pump to the garment. The compression system is designed to be a user friendly and patient compliant system that will help prevent the formation of clots.

DETAILED DESCRIPTION

The examples below describe a unique intermittent pneumatic compression system that may include a pneumatic compression device, interconnections, and garments that may be useful for the prevention of DVT. As those skilled in the art will appreciate, the present examples are suitable for application in a variety of different types of external compression systems.

FIG. 1is an overview of a patient being treated with an intermittent pneumatic compression system of the present invention. The patient100is shown being treated to prevent DVT, and is wearing a compression garment102on the right leg and a compression garment104on the left leg. The pressure supply and control unit108pressurizes the limb garments102,104, via the tubing106, by supplying varying amounts of pressure at varying times. This varying pressure applied to areas covered by the garments102,104tends to help prevent the formation of blood clots. Although two garments are shown, any number of garments may be used in alternative examples.

Although the patient100is shown wearing calf-length garments, garments can be calf-length, foot length, thigh length or configured as appropriate for other appendages, such as the hands and arms. The unique pressure supply and control unit108is coupled to the compression garments102and104via pneumatic connector tubing106that may include connectors designed to facilitate proper hook up. The tubing106is typically made from a flexible plastic material such as PVC, polyethylene, or similar materials. In one alternative example, the tubing106is an anti-kink, and anti-crush air delivery tube. A stat or ribbed flexible extrusion may be disposed at the center of the pneumatic connector tubing106. In a further alternative example a unique identification mechanism may be incorporated into the tubing connections.

The pressure supply and control unit108is constructed as a portable external medical device designed to operate on line voltage, on battery backup power, or the like. The pressure supply and control unit108provides compressed air to the garments such that the medically desired inflation and deflation pressures and rate of inflation and deflation are applied to the limbs of the patient100. The pressure supply and control unit contain a pump and a manifold mechanism operating according to a unique process for controlling air movement to and from the garments.

FIG. 2shows an air flow schematic of the four-valve air delivery manifold that may be used for controlling air movement to the garments under control of a unique valve control process214, as controlled by a controlling circuitry216. The 4-valve manifold system200may be contained within the pressure supply and control unit108. The 4-valve manifold system includes a pump (or equivalently a compressor, or a compressor pump)201to provide compressed air to the system. The flow of the compressed air may be controlled by four valves202,204,206, and208, an orifice210, and a pressure sensor212, all of which may be activated and otherwise controlled by process214. Also included is an atmospheric vent251, and a vent orifice250. This works well for sea level situations, but where the elevation is above sea level it is desirable that the patient receives the optimal pressure differential above the pressure that the patient is at, relative to ground level thereby insuring you have an optimal clinical pressure differential at for example a mile high city like Denver. This feature is implemented in an exemplary 5 valve design.

An additional example may be a 5-valve manifold which utilizes the same unique 4-way valve schematic as described above but may include an extra 3-way valve that is plumbed inside the manifold, upstream of the two three way valves that supply and distribute air to the limbs. The extra 3-way valve eliminates the typical need for an air bleed orifice in the manifold block (normally placed in conjunction with the pressure transducer line) since when the leg air distribution valves close and stop supplying air to the limb, air pressure must vent to zero pressure (relative to the ambient air pressure) before the start of the next cycle of pressure to the next limb so that a calibrated and measured pressure that is in a therapeutic range above the ambient air pressure is delivered to the limb on the following cycle.

The additional example may include an extra three way valve that is between the leg output valves1and2and the incoming control valves3and4. This extra three way valve is a normally closed valve which eliminates the need for a bleed orifice in the block that brings its internal pressure between leg compressions to zero pressure. When this extra valve shuts off and de-energizes it is normally closed and therefore any air pressure in the manifold goes to zero (relative to the ambient air pressure) before the start of the next cycle. Because this valve zeroes the pressure in the block like the bleed/vent orifice in the four valve system, this insures delivery of an optimum, clinically proven exemplary 40 mm Hg above the variable air pressure on the patient which may be seen at altitude.” This feature may be useful because conventional systems typically do not compress at the clinically proven values of pressure above the zeroed values of where the patient is being treated and therefore don't take into account a patient well below sea level or well above sea level.

Pump201supplies air to valve3206, and valve4,208. Valve4is coupled to valve2,204, and to valve1,202via the pressure sensor212, and orifice210. Valve2,204is also coupled to garment limb2,104.

Valve1,202is coupled to valve2,204before the pressure sensor212. The output of valve1,201is an output coupled to Garment limb1,102. The direction of airflow is generally shown by the arrows on the diagram.

In one example, valve1202and valve2204are conventionally constructed normally closed 3-way valves. When they are de-energized, such as would occur in a fault condition, like a depleted battery or power failure, they vent to atmosphere, effectively eliminating any air pressure in the garment and system providing additional patient safety. Valve1202and valve2204are two downstream distribution valves to route the compressed air flow to garment1and garment2respectively.

Valve3206and valve4208are normally closed 2-way valves so when they are energized, the valves open, allowing air flow. Valve3206and valve4208are configured as two parallel upstream valves.

The exemplary air delivery manifold system design controls air movement to the garments102and104. The 4-valve manifold system is a dynamic system designed to function with the compression garments of the present example that deliberately leak air. The deliberate air leakage of the present example provides for an added level of safety to the patient. The pressure within a garment moves to zero pressure in any of the risk scenarios are encountered. For example where the deflation of a garment might be prevented, such as batteries losing power, power interruptions, wires breaking, valves sticking, a patient occluding the tubing in their sleep when the garment is inflated, or circuit boards de-energized; the present example allow for the pressure to be released.

An example of the activation and utilization of the 4 valve manifold system can be as follows: The pump201provides compressed air to the system. When inflation of a garment is indicated by the unit108, valves3and4open, and valve1opens. Air rapidly fills the garment102, primarily through valve3206. When a predetermined therapeutic pressure in the garment102is reached (conveniently termed the “fast fill” of the garment bladders), the pressure sensor212indicates that valve3should close. The garment102leaks air and the pressure is maintained at the therapeutic pressure for a therapeutic time by airflow through the orifice210placed after valve4. The deliberate leakage of air from the garment while in use allows for improved maintenance of pressure in the garments. The orifice210placed after valve4208is designed so the air flow rate through the orifice is approximately that of the air leak rate of the garments under the predetermined therapeutic pressure. Therefore, when valve3is closed, valve4still feeds air lost by the garment to keep the garment at the therapeutic pressure through the secondary pathway with a small orifice. Additionally this form of hysteresis of fill, leak, fill, around a set pressure tends to provide additional therapeutic benefits by moving volumes of blood towards the heart.

The pressure sensor212directs valve4to close if the upper pressure set-point is reached, or to open if the lower pressure set-point is reached, thereby providing a dynamic response to the pressure within the garment. When the pressure has been applied for the designated time, valve1and valve4close. The above scenario is repeated on the other limb through valve2204and garment104.

FIG. 3is a block diagram of the operation of the four-valve air delivery manifold. Beginning at Limb1at block302, both valves3(206ofFIG. 2) and4(208ofFIG. 2) are energized and opened to allow air to flow. At block304, the circuitry energizes valve1(202ofFIG. 2) to open it. Valve2(204ofFIG. 2) remains closed. At block306, the garment on the first limb (102ofFIG. 2) fills to a first predetermined pressure, such as 40 mmHg for prevention of DVT, primarily through valve3. This is because the air flow from valve4is throttled by the orifice.

When the pressure in the garment (102ofFIG. 2) reaches the first predetermined pressure as desired therapeutic level, the pressure sensor (212ofFIG. 2) signals the controlling circuitry (216ofFIG. 2) to close valve3at block308so that air flow to the garment is solely through the orifice (210ofFIG. 2) throttling air flow from valve4. At block310, air leaks from micro holes (not shown) in the garment (102ofFIG. 2) on the first limb at about the same rate as air is supplied via the orifice (210ofFIG. 2). At block312, the sensor (212ofFIG. 2) detects air pressure of the air flow fed to the garment, and if the pressure exceeds a programmed upper set-point, valve4closes. If the pressure drops below a programmed lower set-point, it causes valve4to open and increase the pressure in the garment to the desired level, providing dynamic control of the pressure within the garment. Once at the upper set-point, valve4closes in what approximates a hysteresis loop of controlling pressure and at the same time having a safety system built in.

At block314, a timer (not shown) causes valve1(202ofFIG. 2) to close after pressure has been applied for a predetermined amount of time. ‘The timer closes valve1, the garment vents air and pressure through the 3 way valve and continues to leak air through micro-holes that may be present. Air continues to leak from the garment through the micro holes until the pressure reaches 0 mmHg. The process next controls the inflation of the garment on limb2(104ofFIG. 2)

Now the inflation of the garment on limb2is described. At block316, the controlling circuitry energizes and opens valves3and4. At block318, valve2(204ofFIG. 2) opens and at block320, the garment (204ofFIG. 2) on limb2fills quickly to a second predetermined pressure. In one example, the first predetermined pressure is the same as the second predetermined pressure. In another example, the first predetermined pressure is different from the second predetermined pressure. Valve3(206ofFIG. 2) closes at block322. At block324, as before, air leakage through the micro holes in the garment is supplemented by air flowing through the orifice from valve4(208ofFIG. 2). At block326, valve4(208ofFIG. 2) is closed if the pressure reaches the upper set-point, opens valve4if the pressure drops to the lower set-point, and valve4opens and closes to maintain the pressure in the garment at the appropriate therapeutic level. The upper set-point and lower set-point for the garment102on limb1may be the same as or different from the upper set-point and lower set-point for the garment104on limb2. At block328, the valve2(204ofFIG. 2) is closed after the predetermined amount of time and the garment on limb2(104ofFIG. 2) continues to leak air through the micro holes in the garment until the pressure drops to 0 mm Hg. Here the timer closes valve2, the garment vents air and pressure through the 3 way valve and continues to leak air through micro-holes. Regarding the description above valve1and2are normally closed 3 way valves. This means that any shutoff by the system or emergency failure of power for any reason to the system, safety is maintained as these valves are closed and vent anything ‘forward’ of them (the tubing and the garments) to zero pressure for the sake of safety out large venting holes in the valves. So in general the timer closes valve (1or2), garment vents air and pressure through the 3 way valve and continues to leak air through micro-holes’. At block302, the controlling circuitry begins the treatment cycle again. The cycles and pressures described above have been found to be useful in the prevention of clots. The absolute pressures and times of application may be determined and adjusted as needed for a given application. However the following graphs show a graphical indication of the pressures traduced in each garment over time.

FIG. 4is a graph showing the pressure of the air flow fed into each of the garments as a function of time, as caused by the operation of the 4 valve manifold. The graphs of the pressure of the air flow fed into the garments on limb1402and limb2404are shown offset for clarity. At point406, inflation in the garment on limb1begins. At this point, valves3and4are open and the garment is rapidly filling, primarily through valve3. At point408, the pressure of the air flow fed into the garment is approaching the first predetermined pressure, valve3closes and air continues to flow to the garment from valve4through the orifice. At the plateau on the graph410, valve4opens and closes to maintain the therapeutic pressure between the upper set-point and lower set-point. At point412, all valves are closed and air leaks from the garment through the micro holes. As the pressure in the garment on limb1decays to zero, the timer begins the pressurization of the garment on limb2, which follows the same process as described above for limb1.

FIG. 5shows a plan view of an exemplary 4-valve manifold system200. The 4-valve manifold system comprises a mounting block502to which the 4 valves (202,204,206,208) are mounted. The pump201is mounted to the mounting block502adjacent to the valves. In equivalent examples the valve arrangement shown may be maintained on a smaller mounting block having the compressor201mounted elsewhere. The mounting block502has multiple penetrations506for mounting, as well as a sensor port504for placing the pressure sensor212.

The valves202,204,206,208are of typical construction and operate as previously described, and are electromechanical devices having control signals supplied via external wiring (not shown). The pump201is also of conventional construction to provide a desired air flow and is controlled by external wiring (not shown). The mounting block502is mad of any suitable rigid material such as metal, molded plastic or the like. The mounting block includes passageways for air flow between the valves as previously described, and outlets to couple air flow to the pressure garments.

FIG. 6shows an isometric view of an exemplary 4-valve manifold system, also showing the 4-valve manifold system with a mounting block502, the 4 valves (202,204,206,208), and the pump201.

FIG. 7is the opposite isometric view of the exemplary 4-valve manifold system. In addition to providing a mounting structure for the pump201and valves202,204,206,208, two air outlet ports702and703are present in the bottom of the mounting block502. These air outlet ports are the site where the pneumatic connector tubing106may be coupled for air delivery to inflate the garments (102and104ofFIG. 2).

Since a variety of garments may be coupled to the pressure supply and control unit (108ofFIG. 2), it may be desirable to provide circuitry or another method that allows for identification of the garment attached, so that proper pressures appropriate to the garment may be applied.

FIG. 8shows the infrared detectors and colored connectors on the pneumatic connector tubing. The infrared (IR) detection system utilizes optical sensing to determine the particular type garment, such as a foot garment, that is coupled to it so the differing air pressure and/or flow requirements of various garments may be provided automatically. Some other available systems employ a magnetic switch, or use radio frequency or microprocessors that attempt to detect which garment is attached by its fill. These may be inaccurate due to the variability of the patient flesh density and the tightness of the wrapping on the limb.

This detection system uses an IR optical sensor802and804attached to the case of the pressure supply and control unit108adjacent to where the pneumatic connector tubing106connector couples to the air outlets702and704. The IR sensor detects the color of the connector806and connector808attached to the tubing106and then signals the controlling circuitry to choose corresponding operating pressure parameters accordingly. In one example, an irregular shaped core810may be disposed at the center of the pneumatic tubing106. Such a structure tends to allow air flow if the tubing106is crushed, pinched or kinked.

The use of colored connectors and IR detection improves upon the currently used microprocessors that evaluate the time to fill a garment as the trigger to turn on a higher pressure to the garment, over that of RF with a typically a hidden toroidal inductor or equivalent in the connector. The use of colored connectors with IR detection tends to eliminate side effects such as electromagnetic interference from a microprocessor or the generation of a radio frequency bubble (generally a volume of space in which radio frequency interference may be present) that might adversely affect other equipment in a hospital setting.

FIG. 9is a representation of an exemplary garment for use with the present invention. The garment900has a symmetrical shape that that allows the nesting of garments together when they are cut out so there is no linear waste in their manufacturing, effectively eliminating all waste that is associated with cutting a conventional asymmetrical garment.

A unique feature of the design is that the tab hook closure904may be placed on one side as drawn but the tab loop closure area906can be made anywhere on the surface of the garment since the entire exterior (or portions thereof) may be made from loop material, thereby accommodating every possible limb circumference variation as long as it connects to the garment shape, also allowing the garment to fit variable sized calves that have variable circumferences at the different tab attachment points.

For example uniform spacing of the fingers (exemplary singer shown at910), and equal sized fingers910allow a high yield of usable material with a minimum of waste. This garment is suitable for both right and left limbs, eliminating the need for different garments for the opposite limb. The garment may be made of any suitable material such as cloth or the like. The product may be die cut, thereby having essentially a no manufacturing waste.

The garment may include individually applied tabs904of hook and loop tape to match with the matching tabs of hook906and loop tape (individual tab not shown) for attachment when in use. However in the preferred example and as previously described the entire outside surface of the garment may be loop material that allows increased flexibility in fitting the garment. Alternatively other types of equivalent fasteners may be used.

The garment typically includes an internal bladder (not shown) that inflates and deflates through action of the pressure supply and control unit (108ofFIG. 1). The garment may include a single chamber. Or in alternative examples meandered chambers or multiple chambers may be utilized. The bladder may be mad of any suitable material that may hold air, such as plastic, vinyl, rubber, or the like. The bladder may be bonded to the fabric, sewn between fabric layers or otherwise secured so that it will not shift while in use.

Garments may typically be produced for the foot, thigh, calf, and the like. In one example, the garment is an inflatable garment with an internal bladder or chamber enclosed by material or has a connector with micro holes (not shown) such that pressurized air within the chamber may be leaked with desired leakage rate.

The garment includes a tube fitting908coupled to the chamber for receiving air flow via the pneumatic connector tubing106. Inflatable garment is well known to one of ordinary skill in the art. Alternatively the tubing may be integral to the garment, instead of being removable so that there is a single connection to the pump unit.

FIG. 10is a block diagram of the pressure supply and control unit according to various examples of the invention showing further details of the controller circuitry. The pressure supply and control unit108comprises the air pump201, the valves202,204,206and208, the pressure sensor212, the IR sensors802and804, the controlling circuitry216, a power source1004. The controlling circuitry216receives input from the pressure sensor108, the IR sensors802and804, and generates output to switch ON/OFF one or more of the plurality of the valves202,204,206and208. The power source1004may be a battery or a power input from a wall plug. In alternative examples, the pressure supply and control unit10may include a memory (not shown) loaded with non-volatile controlling logic accessible and executable by the controlling circuitry216for implementation of desired operation procedures for generating air flow and control air pressure. The optional memory (not shown) may be an external memory module or integrated within the controlling circuitry216as an on-chip memory. The controlling circuitry216may be a microprocessor, a microcontroller, a programmable logic controller, or the like.

In some examples, the pressure supply and control unit108includes at least one I/O interface, such as a touch screen, a keyboard, a PIN pad, coupled to the controlling circuitry216. A patient or user may manually edit the operation parameters, such as the upper pressure set-point and lower pressure set-point, via the I/O interface.

Those skilled in the art will realize that various configurations may be used for air movement control and pressure regulation. The foregoing description of the invention has been described for purposes of clarity and understanding. It is not intended to limit the invention to the precise form disclosed. Various modifications may be possible within the scope and equivalence of the appended claims.