Inflatable member for compression foot cuff

A foot cuff that is inflatable to apply compression to the foot to promote blood flow has a bladder formed of two layers of material secured together. An outer layer includes a foot-underlying portion that has a greater thickness and rigidity that an opposing inner layer. The outer layer directs expansion of the bladder upon inflation in the direction of the inner layer and toward the foot for increasing compressive force applied to the foot.

FIELD OF THE INVENTION

The present invention generally relates to an inflatable member for a compression foot cuff.

BACKGROUND

Compression devices for applying compressive forces to a selected area of a wearer's anatomy are generally employed to improve blood flow in the selected area. Compression devices that provide intermittent pulses of a compressed fluid (i.e., air) to inflate at least one inflatable chamber in a cuff or sleeve are particularly useful. This cyclic application of pressure provides a non-invasive prophylaxis to reduce the incidence of deep vein thrombosis (DVT), and the like. These compression devices find particular use during surgery or long periods of immobility on patients with high-risk conditions such as obesity, advanced age, malignancy, or prior thromboembolism. Patients who develop this condition often have swelling (edema) and tissue breakdown (venous stasis ulcer) in the lower leg. When a DVT occurs, the valves that are located within the veins of the leg can be damaged, which in turn can cause stasis and high pressure in the veins of the lower leg.

Generally, these compression devices are fluidly coupled to a source of pressurized fluid by one or more air tubes. Additionally, each compression device includes a flexible shell having one or more bladders disposed therein. The compression device is placed around the patient's foot or other selected portion whereupon a pressurized fluid is delivered into the bladder creating pressure at the part or parts of the body in contact with the bladder.

Compression cuffs adapted for use with a patient's foot may be used by themselves or combined with one or more additional compression cuffs or sleeves that are disposed on portions of a patient's leg for improving the treatment regimen. In general, each of the additional compression sleeves includes a plurality of separate inflatable chambers that are progressively arranged along a longitudinal axis of the sleeve from a lower portion to an upper portion of the limb. A pressure source, e.g. a controller, is provided for intermittently forming a pressure pulse within these inflatable chambers from a source of pressurized fluid during periodic compression cycles. The compression sleeves provide a pressure gradient along the patient's limbs during these compression cycles which progressively decreases from the lower portion to the upper portion of the limb (e.g. from the ankle to the thigh).

Compression cuffs that are adapted for use with a patient's foot generally include a heel strap with a tab portion that is adapted to fit around a portion of the patient's heel. This arrangement allows the compression cuff to be wrapped around and releasably attached to the patient's foot. The compression cuff may include a generally rigid sole to direct expansion of the inflatable chamber toward the wearer's foot. The rigid sole needs to be located under that portion of the inflatable member that is acting on the portion of the foot to produce blood flow out of the foot. Conventionally, the rigid sole is temporarily attached to the bladder by double stick tape. Final location and positioning of the rigid sole may be carried out by stitching. For example, the bladder is typically stitched to an outer wrap of the foot cuff. The stitching can be arranged so that it captures the rigid sole in position relative to the bladder, as well as the outer wrap. This requires care and precision in manufacturing the foot cuff.

SUMMARY

In one aspect of the present invention, an inflatable bladder for use in a compression foot cuff configured to be secured to a foot of a wearer generally comprises a fluid-impermeable inner bladder layer for being positioned adjacent to a foot of a wearer. A fluid-impermeable, integrally formed outer bladder layer is secured in opposing relation to the inner bladder layer to define an inflatable chamber. The inner and outer bladder layers define a foot-underlying portion of the bladder that is sized and shaped to underlie the wearer's foot and a wing portion extending laterally outwardly from the foot-underlying portion. A thickness of the outer bladder layer at the foot-underlying portion is greater than a thickness of the inner bladder layer to provide rigidity to the outer bladder layer so that the inflatable chamber expands more toward the wearer's foot than away from wearer's foot when the foot cuff is secured to the wearer's foot, and a thickness of the outer layer at the foot-underlying portion is greater than a thickness of the outer layer at the wing portion so that the wing portion of the bladder is more flexible than the foot-underlying portion of the outer layer to wrap around a superior portion of the wearer's foot.

Another aspect of the present invention is a method of making a compression foot cuff configured to be secured to a foot of a wearer, the compression foot cuff having a foot-underlying portion for underlying the wearer's foot. A fluid-impermeable inner bladder layer having a first thickness is provided. An integral outer bladder layer including a foot-underlying portion and a wing portion extending laterally outward from the foot-underlying portion of the cuff is molded as one piece. The foot-underlying portion has a second thickness that is greater than the first thickness of the inner layer, and the wing portion has a third thickness that is less than the second thickness. The inner bladder layer and the outer bladder layer are welded to one another along a line to define an inflatable chamber at the foot-underlying portion of the cuff.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, a compression foot cuff for applying compressive pressure to a wearer's foot is generally indicated at10. The foot cuff is adapted for use in a compression therapy system, which further includes a supply of pressurized air (not shown) and tubing40connecting the supply of pressurized air to the foot cuff.

As shown best inFIGS. 1A and 1B, the foot cuff10includes an envelope, generally indicated at12, substantially enveloping or enclosing a bladder (broadly, an inflatable member), generally indicated at14. The envelope12includes an inner liner16and an outer cover18secured to one another generally adjacent to corresponding perimeters of the layers to define an interior space for receiving and substantially enclosing the bladder14therein. The inner liner16and the outer cover18may be fixedly secured to one another at their peripheral edge margins, such as by heat welding, adhesives, sewing or other suitable ways. Alternatively, the inner liner16and the outer cover18may be releasably secured to one another by suitable releasable fasteners (not shown) known to those having ordinary skill in the art. In use the inner liner16is adjacent to the wearer's foot and the outer cover18is located farthest from the foot. As used herein, the terms “inner” and “outer” indicate relative positions of respective components and surfaces with respect to the skin of the wearer's body part when the compression device is secured to the body part, and as such, an “inner” component or surface is more adjacent to the skin of the body part than an “outer” component or surface.

Inner liner16and outer cover18of the envelope12include ankle strap portions19aand19brespectively. Ankle strap portions19a,19bhave a longitudinally projecting configuration for wrapping about a portion of the back of the foot adjacent to the ankle. The ankle strap portions19a,19bcan be sewn, RF welded, or sonic welded. However, in the illustrated embodiments, the ankle strap portions19a,19bare formed as one piece with the inner liner16and outer cover18, respectively. Respective fastening tabs20a,20bare secured to the strap portion19band a main portion of the cuff. The fastening tabs20a,20bcomprise releasable fastener components such as one of a hook component and a loop component for securing the cuff10in a wrapped configuration around a foot of a user. Other ways of releasably securing the cuff10around the foot of a user are within the scope of the present invention.

The inner liner16of the envelope12is adapted for contacting the foot. The inner liner16is in one embodiment fabricated from a chemically treated material, with wicking ability, for wicking away moisture from the skin. In one embodiment, the inner liner16includes a mesh-like fabric capable of wicking moisture away from the patient's skin. Furthermore, the inner liner16can be faced with a soft material toward the treatment surface of the patient. For example, the material can be a thin layer of open celled porous foam, napped cloth, or a layer of vapor permeable cloth. The inner liner16may be formed from other materials. It is to be understood that the cuff10may not include an inner liner within the scope of the present invention.

The outer cover18is configured for providing the attachment surface for hook and loop fastening tabs20a,20bof cuff10. For example, the outer cover18may comprise a loop-type fastening component and the tabs20a,20bmay be hook fastening components. Moreover, the outer layer18provides a soft material for cushioning effect against the top portion of the feet and may be fabricated from similar materials as the inner liner16and in similar dimensions therewith for corresponding geometry. Alternatively, outer cover18may be fabricated from a laminated material, such as, for example, Sontara® fabric, open cell urethane foam, or loop fabric. The inner liner16may be formed from other materials. It is to be understood that the cuff10may not include an outer cover within the scope of the present invention.

Referring to FIGS.1B and2-8, the bladder14includes inner and outer bladder layers22,24, respectively, of air impermeable material (e.g., PVC, rubber, etc.) joined together in a suitable manner along a line26generally adjacent to their peripheries to define a single inflatable chamber27(FIGS. 6 and 8). The inner and outer bladder layers22,24may be joined to one another in a suitable manner such as by radio frequency (RF) welding. Other ways of joining the inner and outer bladder layers22,24include sewing, adhesive, heat sealing, etc. The inner and outer bladder layers22,24are secured together so that an inner face of the outer layer faces an outer face of the inner layer, and an outer face of the outer layer faces away from an inner face of the inner layer. The inflatable chamber27of the bladder14is adapted for receiving and retaining a pressurized fluid (e.g. air) for exerting compressive pressure to the foot during successive pressure application cycles. Moreover, the inner layer has a thickness and material properties to allow it to be easily reformed by compressed air in the inflatable chamber27. It is understood that the bladder14can include more than one inflatable chamber27within the scope of the present invention. The bladder14includes a foot-underlying portion, generally indicated at30, that is sized and shaped to underlie the wearer's foot. The thickness and rigidity of the foot-underlying portion30are selected so that expansion of the inflatable chamber27in the area of the foot-underlying portion is concentrated in a direction away from the foot underlying portion and toward the foot for increasing foot compression in this area. Extending laterally outward from the foot-underlying portion30of the bladder14is a wing portion, generally indicated at34, that is sized and shaped to be wrapped partially around the foot to a superior portion of the wearer's foot. The material of the wing portion34is preferably of a low enough density to be folded over onto the top of the foot (for example and without limitation, a medium vinyl composite having a durometer of 30-40 Shore A). While bendable, the wing portion34provides sufficient rigidity to resist flexing out of plane under pressure during inflation of the inflatable chamber27. It is understood that the wing portion34may have other shapes and sizes. It is also understood that the bladder14may not include the wing portion34within the scope of the present invention.

Referring toFIG. 6, the outer bladder layer24has a thickness T1at the foot-underlying portion30that is greater than a generally uniform thickness T2of the inner bladder layer22at the foot-underlying portion. In general, because the outer bladder layer24at the foot-underlying portion30is thicker than the inner bladder layer22at the foot-underlying portion, the outer bladder layer is more rigid than the inner bladder layer at the foot-underlying portion of the bladder. It is believed that by making the outer bladder layer24more rigid than the inner layer22at the foot-underlying portion30, the outer bladder layer provides a counterforce that directs expansion of the inflatable chamber27toward the inner layer, the inner liner16and the user's foot. In this way, the inner bladder layer22expands inward, toward the user's foot more than the outer bladder layer24expands outward, away from the user's foot to direct compressive force toward the user's foot. Moreover, the thicker foot-underlying portion30can provide a surface on which the patient could walk so that it would be unnecessary to remove the cuff10. For example and without being limiting, the thickness T1of the outer bladder layer24at the foot-underlying portion30may be at least about three times as great as the thickness T2of the inner bladder layer22at the foot-underlying portion30, and more preferably, the thickness T1is at least about ten times greater than the thickness T2, and more preferably, the thickness T1is at least about twenty five times greater than the thickness T2. In one example and without being limiting, the thickness T1of the outer bladder layer24at the foot-underlying portion30may measure between about 0.100 and about 0.300 inches; and the thickness of T2the inner bladder layer22at the foot underlying portion30may measure between about 0.006 and about 0.030 inches, more preferably between about 0.006 and about 0.012 inches. The inner and outer bladder layers22,24at the foot-underlying portion30of the bladder14may have other dimensions and relative sizes without departing from the scope of the present invention.

Referring to FIGS.1B and2-8, to further rigidify the underlying portion30of the outer layer, a stiffening groove37ain the outer face of the outer bladder layer24and a corresponding stiffening rib37bon the inner face of the outer bladder layer extend generally adjacent to the perimeter of the underlying portion30of the outer layer. The stiffening rib37binhibits bending of the underlying portion30out of its plane. This allows thickness T1of the outer bladder layer24to be smaller than would be required without the rib.

Referring toFIG. 6, in the illustrated embodiment the thickness T1of the outer bladder layer24at the foot-underlying portion30is also greater than a thickness T3of the outer bladder layer at the wing portion34of the bladder14. As stated above, the greater thickness T1of the outer bladder layer24and the stiffening rib37bat the foot-underlying portion30provide rigidity to the outer bladder layer so that it acts as a counterforce. In one embodiment, the thickness T3of the outer bladder layer24at the wing portion34of the bladder14allows the wing portion to be generally flexible and pliable so that in use, the wing portion34can be folded along a side of the wearer's foot to a top of the foot. Accordingly, in one embodiment the thickness T3of the outer bladder layer24at the wing portion34of the bladder14is such that the wing portion of the bladder can be wrapped around the foot. For example and without being limiting, the thickness T3of the outer bladder layer24at the wing portion34may be at least about 1.5 times less than the thickness T1of the outer bladder layer at the foot-underlying portion30. In other words, the thickness T1of the outer bladder layer24at the foot-underlying portion30may be at least about two times greater than the thickness T3of outer bladder layer at the wing portion34. More preferably, in one example, the thickness T3of the outer bladder layer24at the wing portion34may be at least about between 5-15 times less than the thickness T1of outer bladder layer at the foot-underlying portion30. In one example given without being limiting, the thickness T3of the outer bladder layer24at the wing portion34may measure between about 0.020 and about 0.060 inches. The outer bladder layer24at the wing portion34and the foot-underlying portion30of the bladder14may have other dimensions and relative sizes without departing from the scope of the present invention.

A fluid inlet port38on the outer face of the outer bladder layer24fluidly connects tubing40(FIGS. 1A and 1B) from an air compressor controller (not shown) to the inflatable chamber27. The fluid inlet port38is positioned generally adjacent to a juncture of the foot-underlying portion30and the wing portion34. When the cuff10is assembled, the fluid inlet port38extends through a cut-out20in the outer cover18. An internal conduit42(FIG. 8) extends from a connecting opening44in the fluid inlet port38through the inner face of the outer bladder layer24. The connecting opening44is sized and shaped to receive the tubing40and to secure the tubing to the fluid inlet port38. Other ways of connecting tubing40to the fluid inlet port38are within the scope of the invention. The fluid inlet port38has a generally low-profile height projecting outward from the outer face of the outer bladder layer24so that the fluid inlet port has a cross-sectional shape that is generally oblong. It is understood that the fluid inlet port38may be of other shapes and configurations. For example, the fluid inlet port38may comprise a plastic component that is secured, such as by heat welding or other means, to the bladder14. It is understood that other ways of introducing air or fluid into the inflatable chamber27are within the scope of the invention, and the tubing40may be fluidly connected to the inflatable chamber in other ways without departing from the scope of the invention.

Referring toFIGS. 1A and 7, in the illustrated embodiment the bladder14is generally fixedly secured to the inner liner16and the outer cover18using securement openings46extending through the foot-underlying portion30of the inflatable member generally adjacent to the perimeter of the foot-underlying portion. In the illustrated embodiment, the securement openings46are located between the perimeter edge of the foot-underlying portion30and the line26where the outer bladder layer24and the inner bladder layer22are secured to one another. The inner liner16and the outer cover18are secured to one another through these securement openings46to thereby secure the bladder14in fixed position inside the envelope12. The inner liner16and the outer cover18may be secured to one another at securement points48by heat welding, adhesive bonding, mechanical fasteners or in other ways. In one example, where the outer cover18is of a relatively thick foam material, the inner liner16may be inserted through the securement openings46to the outer cover to secure the inner liner to the outer cover. Other ways of securing the bladder14to the envelope12to fix the relative position of the bladder with respect to the inner liner16and/or the outer cover18is within the scope of the invention. Alternatively, the bladder14may “float” inside the envelope12and not be generally fixed in a relative position with respect to the inner liner16and/or the outer cover18.

In one embodiment and without being limiting, the outer bladder layer24may be molded, such as by injection molding, as a one-piece, integral unit.