GB2144620A

GB2144620A - Apparatus to assist the return of venous blood from the lower limbs

Info

Publication number: GB2144620A
Application number: GB08321809A
Authority: GB
Inventors: Alex Bruce
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-08-12
Filing date: 1983-08-12
Publication date: 1985-03-13
Also published as: GB8321809D0

Abstract

Footwear to assist the venous return from the lower limbs comprises a foot portion 1 enclosing or partly enclosing the wearer's foot and including a pumping device 2 to pump fluid intermittently by virtue of compressive action of the foot, for example during walking, and a leg portion 5 having a distensible member 4 in its inner aspect into which fluid is pumped intermittently from said pumping device via conductive means 3 in the heel of the footwear by said compressive action so that fluid is pumped rapidly axially into the distensible member to provide, in effect, a fluid wedge driven into said leg portion to tighten the leg portion and produce a compressive force on the wearer's leg. <IMAGE>

Description

SPECIFICATION Apparatus to assist the return of venous blood from the lower limbs.

The present invention relates to apparatus to assist the return of venous blood from the lower limbs. More specifically, this invention relates to footwear, in particularto footwearwhich has a close-fitting portion extending substantially up the lower limbs.

It has long been known that stasis disorders ofthe venous system ofthe lower limbs can benefit from the use of compression hosiery and a summary of the state of the art is given in Drug and Therapeutics Bulletin 1982, October 15: 20 (21)81-4: Compression Hosiery for Stasis Disorders. Such hosiery gives a graduated compressive force which decreases upwards from the ankle and commonly exerts a pressure at the ankle oftwelveto thirty millimetres of mercury.

However, measurement offootvolume has suggested that an applied pressure of at leastthirty millimetres of mercury is needed to supplementcalf-muscle pump function in the ambulatory subject with symptomatic varicose veins, while in the postthrombotic limb a pressure of fortyto fifty millimetres of mercury improves expulsion of venous blood from thefoot and ankle.

A disadvantage of compression hosiery is that it exerts a continuous pressure which limits the maximum pressure which may be applied, particularly if there is arterial insufficiency.

It is an object ofthe present invention to use the pressure generated intermittently on the portion of footwear beneath the foot, in activity such as walking, to provide a correspondingly intermittent compression ofthe lower limb substantially in phase with calf-muscle contraction, to compress the superficial veins ofthe leg and prevent, or oppose back flow of blood which tends to occurfrom the deep veins to the superficial veins ofthe leg during calf-muscle concentration if there is insufficiency ofthe veins linking the deep end superficial veins of the leg.

According to the present invention, there is provided footwear with a foot portion enclosing, or partly enclosing, the foot, said foot portion containing a pump means serving to pump fluid intermittently from the foot portion, and a leg portion, said leg portion having a member distensible on its inner aspect into which said fluid is pumped from a conductive means in the heel of the footwear by the compressive action of the foot during activity such as walking, so thatfluid is pumped rapidly axially into the distensible member to provide, in effect, a fluid wedge driven into said leg portion to tighten it and produce a compressive force on the wearer's leg.

Preferably, pump means is sufficiently clear of the heel part of the foot portion to avoid it being compressed by the weight on the wearer's heel.

Preferably also the pump means is a flexible container whose elastic properties, wall thickness, and wall shape, are chosen to allow itto regain its uncompressed state and draw fluid backfrom the distensible member when weight is taken off the non-heel portion ofthe foot.

Preferably, the pump means has sufficient resistanceto compression to allow itto retain its uncompressed internal volume until the amount of weight transferred to the non-heel portion of the foot exceeds twenty-five per centof the wearer's bodyweight.

Preferably the conductive means is rigid and non-distensible.

Preferably the conductive means has as large a cross-sectional area and as short a length as is possible within the constraints ofthe aesthetic design ofthe heel portion of the footwear in which it is to be located so as to provide the best compromise between low impedanceto the flow of fluid and 'dead space' (that is, volume within the apparatus otherthan that containable bythe pump means and the distensible member).

Preferablythefluid is air.

Preferably the apparatus comprising pump means, conductive means, and distensible member, is provided with a means for pressurising itto above atmospheric pressure by a short length of tubing attached to a suitable location on the distensible member so that the distensible member may be partially distended in orderthatthe leg portion of the footwear may be tightened sufficiently to fit closely the leg ofthe wearer irrespective ofthe precise shape ofthe leg.

Preferably the pressurising tubing is fitted with a safety valve which opens when the pressure within the apparatus exceeds a chosen limit, for example, 65 millimetres of mercury. For manufacturing conveniencethis safety valve may be manufactured integral with the pressurising tubing and take the form of two orthreeoverlapping cusps attached to the innerwall ofthetubing at an annulus whose elastic properties and wall thickness are chosen so that it balloons outwards radially and renders the valve incompetent when the pressure within the apparatus exceeds 65 millimetres of mercury or other chosen limit, and regains its prior configuration when the pressure within the apparatus falls belowthe chosen limit.

Preferably, where additional pump volume is desired, an additional pump means is located in the heel portion of the footwear. The additional pump means may be independent of the non-heel pump means but conveniently may be an extension to the pump means in the non-heel portion ofthefootwear, said extension extending into the heel portion of the footwear to be compressed by the wearer's heel so that fluid is driven from it into the pump means in the non-heel portion of the footwear and cannot return to the extension until the pump means in the non-heel portion of the footwear substantially regains its non-compressed state.Such additional pump means can, for example, enable a slackerfitto be provided for the leg portion of thefootwearwhileenabling itto betightened sufficiently to obtain a close fit on the wearer's leg immediately priorto the main fluid wedge being driven in to produce its compressive force.

The present invention is also a compression appar atusforcompressing the superficial veins ofthe leg to prevent or oppose back flow of blood from the deep veins to the superficial veins ofthe leg during calf-muscle contraction, said apparatus comprising a pump means locatable in footwear to be operated, preferably by the non-heel portion ofthe foot, a member distensible on its inner aspect for positioning on the leg of the wearer and held in position either by the leg portion ofsuitablefootwear, or by a convenient fastening means or legging, and a conductive means connecting the distensible member and the pump means, sothatfluid can be pumped from the pump means into the distensible memberto exert a com pressive force on the leg ofthe wearer, when the pump means is compressed bythefoot, and can return to the pump means when the compressive force exerted bythe foot is removed.

Embodiments ofthe invention will now be described by way of example, with reference to the accompanying diagrammatic drawings in which: Fig. 1 (a) is a three-quarters oblique rearview of one embodiment of the present invention where the distensible member extends approximately 25% round the circumference of the leg portion of the footwear; Fig. 1 (b) is a sectional plan viewthrough section A-A in Fig. 1 (a); Fig. 2 (a) is a side view of an embodiment in which the distensible member substantially encloses the leg of the wearer; Fig. 2 (b) is a front view ofthe compression apparatus of the embodiment in Fig. 2 (a); Fig. 2 (c) shows a sectional plan viewthrough section A-A in Fig. 2 (b); Figs. 3 (a), (b) and (c) are corresponding views of Fig.

2 of an embodiment in which the distensible member encircles the leg ofthewearer; Fig. 4 (a) is a plan view of a two-cusp safety valve in the pressurising tubing 6 (Figs. 1,2 and 3).

Fig. (b) is a sectional side view ofthe cusps ofthe valve in Fig. 4 (a) and their attachmentto the balloonable annulus in the pressurising tubing 6 (Figs.

1,2and3).

Fig. 4 (c) is a sectional side view of the valve of Figs.

4 (a) and (b) when the pressure within the tubing exceeds the chosen limit and renders the valve incompetent as a consequence of ballooning of the annulus.

Fig. 5 (a} shows a sectional side view of a portion of the footwear in which the pump means has an extension into the heel portion of the footwear; Fig. 5 (b) is a similarview ofthe portion offootwear of Fig. 5 (a) in which the extension has been compressed bythewearer's heel.

Referring to Figs. 1,2, and 3, footwear to assist the return of venous blood from the lowerlimb has a foot portion 1 with a pump means2 in the form of a compressible fluid-filled container connected by a conductive means 3 to a distensible member 4 in leg portion 5, said distensible member having pressurising tubing 6 with a safety valve (Fig. 4). In the example of Fig. 1 (a) and (b),the distensible member 4 extends approximately 25% round the circumference ofthe inner aspectofthe leg portion 5 ofthefootwear and avows considerable latitudeforthe aesthetic design of the footwear.

The distensible member4 may be made of any suitable material such as natural or synthetic rubber; the pump means 2 and the conductive means 3 may be made of synthetic plastics material.

In the example of Fig. 2 (b), the distensible member 4 stops short of complete encirclement ofthe inner aspect of the leg portion 5 (Fig. 2 (awl so that a zip or other fastener means can be used without prejudice to the distensible member 4.

Inthe exarnple of Fig. 3 (b)the distensible member4 completely encircles the inner aspect of leg portion 5 in this case (Fig3(a)).

Referring to Fig. 4 tea) - 4 (c), the two cusp safety valve 10 includes transverse overlapping cusps 11 adjacent a thin walled annulus part 12.

As shown in Fig. 4 it) the valve 10 becomes incompetent when the pressure within the compression apparatus exceeds the chosen safety limit and causesthe annulus 12 to which the valve is attached to balloon radially outwards thereby moving the cusps 11 apart.

Referring to Fig. 5 (a) an additional pump means is provided which in this embodiment is an extension 7 of the pump 2. The extension 7 is located on the heel portion of the footwear and extension 7 communicates with the pump means 2 by aperture 8 in its front wall 9.

Referring to Fig. 5 (b), extension 7 is compressed by the wearer's heel so that aperture 8 (Fig . 5a) in front wall 9 is closed.

The above compression apparatus (Figs. 1 to 3) operates when there is intermittent pressure applied bythenon-heel portion ofthefoottothe pump means 2, such asfor example, when walking orsimply changing the weight sufficiently from one footto the other orfrom the heel to the forepart ofthe foot when standing. This results in fluid being expelled from the pump means2through the conductive means3tothe distensible member4where it acts in the manner of a fluid wedge driven from below into the leg portion of footwear, or into the leg portion ofthe compression apparatus fastened to the wearer's leg, to tighten it and thereby provide a compressive force on the wearer's leg.When the weight is substantially taken off the non-heel portion ofthefootthe pump means2 regains its non-compressed state whereby fluid is withdrawn into the pump means2throughthe conductive means3from the distensible member4 and the compressive force is removed from the wearer's leg as the fluid wedge is withdrawn. Since the compressiveforce is generated when theweight ofthe wearer istransferred from the heel portion to the forepart ofthe wearer's foot (which coincides with calf-muscle contraction) and the conductive means 2 has a low impedence to fluid flow, compression of the leg, and its release, occurs substantially in phase with calf-muscle activity and therefore occurs when physiologically required. Asthe compression is brief and achieved by an intermittently applied fluid wedge,the compression apparatus can be of a straightward design without requiring multiple sleeves, non-return valves or provision for compression of the wearer's foot, and need not encircle the wearer's leg. The apparatus may therefore be kept sufficiently compact to allow itto be readily locatable in existing footwear or incorporated into footwear whose precise dimensions are dictated by aesthetic considerations or by fashion.

In the alternative embodiment shown in Figs. 5 (a) and 5 (b) the pump extension 7 in the heel portion of footwear 1 gives additional pump volume which may be used to primethe distensible member4priortothe main fluid wedge being driven into it as described above, orto provide a greater and longer-duration compression ofthe wearer's leg, orto allow the volume contained bythe pump means in the non-heel portion of the footwearto be decreased if required by particular aesthetic considerations.

Claims

1. Apparatus to assist the return ofvenous blood from the lower limbs, said apparatus comprising footwear with a foot portion enclosing, or partly enclosing, the foot, said foot portion containing a pump means serving to pump fluid intermittently from the foot portion, and a leg portion, said leg portion having a member distensible on its inner aspect into which said fluid is pumped from a conductive means in the heel of the footwear by the compressive action of the foot during activity such as walking, so thatfluid is pumped rapidly axially into the distensible member to provide, in effect, a fluid wedge driven into said leg portion to tighten itan produce a compressive force on the wearer's leg.

2.sApparatus according to claim 1, wherein the pump means is sufficiently clear of the heel part of the foot portion to avoid it being compressed by the weight on the wearer's heel.

3. Apparatus according to claim 1 or2,whereinthe pump means is a flexible containerwhose elastic properties, wall thickness, and wall shape, are chosen to allow itto regain its uncompressed state and draw fluid back from the distensible memberwhen weight is taken off the non-heel portion of the foot.

4. Apparatus according to any one ofthe preceding claims, wherein the pump means has sufficient resistance to compression to allow it to retain its uncompressed internal volume until the amount of weight transferred to the non-heel portion of the foot exceeds twenty-five per cent of the wearer's body weight.

5. Apparatus according to any one ofthe preceding claims wherein the conductive means is rigid and non-distensible.

6. Apparatus according to any one ofthe preceding claims, wherein the fluid is air.

7. Apparatus according to any one ofthe preced ingclaimswhereintheapparatuscomprising pump means, conductive means, and distensible member, is provided with a means for pressurising itto above atmospheric pressure by a short length of tubing attached to a suitable location on the distensible member so thatthe distensible member may be partially distended in orderthatthe leg portion ofthe footwear may be tightened sufficiently to fit closely the leg of the wearer irrespective of the precise shape ofthe leg.

8. Apparatus according to any one ofthe preceding claims, wherein, the pressurising tubing is flitted with a safety valve which opens when the pressure within the apparatus exceeds a chosen limit.

9. Apparatus according to claim 8 wherein, safety valve is manufactured integral with the pressurising tubing and takes the form of two orthree overlapping cusps attached to the inner wall of the tubing at an annulus whose elastic properties and wall thickness are chosen so that it balloons outwards radially and renders the valve incompetent when the pressure within the apparatus exceeds the chosen limit, and regains its prior configuration when the pressure within the apparatus falls belowthe chosen limit.

10. Apparatus according to any one of the preceding claims, wherein an additional pump means is located in the heel portion of the footwear.

11. A compression apparatus for compressing the superficial veins of the leg to prevent or oppose back flow of blood from the deep veins to the superficial veins of the leg during calf-muscle contraction, said apparatus comprising a pump means locatable in footwear to be operated, preferably by the non-heel portion ofthe foot, a member distensible on its inner aspect for positioning on the leg of the wearer and held in position eitherbythe leg portion of suitable footwear, or by a convenient fastening means or legging, and a conductive means connecting the distensible memberandthe pump means,sothatfluid can be pumped from the pump means rapidly axially into the distensible memberto provide in effect a fluid wedge driven into said distensible member to exert a compressive force on the leg of the wearer, when the pump means is compressed bythefoot, and can return to the pump means when the compressive force exerted by the foot is removed.

12. Apparatus to assist the return of venous blood from the lower limbs substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2 or Fig. 3 orthese Figs. as modified by Fig. 4 or Fig. 5a and 5b ofthe accompanying drawings.