Compression system

Abstract: Compression system for stimulating venous and/or arterial blood flow in a leg by applying cyclic compressive pressures to a foot. A garment 10 having inflatable bladder(s) 14,18 which upon gradual inflation of the bladder(s) 14,18, slowly compresses substantially the sole of a foot and the upper dorsi-medial and dorsi-lateral areas of the foot and upon deflation rapidly releases the pressure. The muscle mass of the foot is thereby squeezed and upon sudden release, reactive hyperaemia results which increases arterial inflow thereby increasing venous flow, in to the leg. The compression system may be used alone or in conjunction with a calf and/or thigh garment for simultaneous or sequential stimulation of venous blood flow in the leg.

Description: This invention relates to a compression system to improve the circulation in a limb extremity, and more particularly, to a foot compression system. It is known to increase or stimulate blood flow by using a compression system to apply compressive pressures to a limb extremity, e.g. a hand, thigh, calf or foot. The compressive pressures may be cyclic and may vary from providing a massaging action to a sharp pulse action. It is generally believed that the foot is an effective site to apply compressive pressure. It has been shown that the arch of the foot houses a large venous plexus which normally is compressed by means of the foot extending and flattening the arch during walking or running thereby promoting circulation. US Re. 39420 shows a compression device which is said to use this phenomenon by providing a bladder only under the arch of the foot between the balls of the foot and the heel, which upon rapid inflation causes the arch to flatten to simulate the walking or running action. Other devices also exist which simply compress the arch of the foot by applying sharp pulsed, high pressures under the arch by means of an inflatable bag engaging the arch under the mid-foot in conjunction with or without similar devices on the calf and/or the thigh. Other typical devices are shown in documents US-A-4 696 289 and US-A- 5 307 791. However, the known devices suffer from the disadvantages that the use of an inflatable bag located only under the arch results in uncomfortable squeezing of the foot due to the constricting shape the foot has to adopt during inflation causing pain to the patient so that the patient's compliance over prolonged use is poor. In pressure or flattening of the arch, very high pressures are needed to be applied rapidly directly onto the curve of the arch under the midtarsal region of the foot. This region of the arch is without any cushioning and the application of such pumping forces is painful and uncomfortable to the patient further adding to patient compliance difficulties. We have discovered an effect on the circulation system that is dependent on compression of muscle, wherein release of the compression results in reactive hyperaemia which increases the arterial inflow thereby increasing venous outflow. We have found that this increase in venous flow is not dependent on venous priming. According to the present invention, there is provided a foot garment as claimed in claim 1. The foot garment of the invention provides compressive pressures applied to the muscle mass of a foot substantially to the whole of the sole and dorsum thereof, which application is very comfortable to the user. Due to the arrangement of the bladder(s) to cover the sole of the foot and the dorsum of the foot, the foot during inflation is not constricted sideways or stretched as with prior art devices but lays flat and during inflation is not constricted sideways or stretched as with prior art devices but lays flat and therefore avoids the pinching associated with the known devices. Moreover, in use, it is believed that the garment provides a complementary two-fold stimulation to the blood flow in the foot due to the dual application of compressive pressure on the muscle mass of the foot by the bladder under the sole as well as compressive pressure acting directly on the superficial veins underlying the dorsi-medial and lateral regions of the foot, the former enhancing arterial inflow due to hyperaemia and the latter serving to drive the blood from the veins of the foot. An important benefit is that lower pressures are necessary to stimulate comparable blood flow as achieved with prior art devices. The foot garment has been shown to have equivalent effect to the known sharp pulsed, high pressure devices in augmented blood velocity at the femoral vein. The biochemical effect is more complicated, the fibrinolytic activity is enhanced and other factors such as the effect of circulating plasminogen activator, tissue plasminogen and other parameters are seen to combine to reduce the risk of clot formation. Moreover, the lower pressures and slow inflation allow the use of a simpler pump to operate the foot garment. Preferably, the garment includes only one bladder. Preferably, the bladder or bladders are inflated over a period of 2 seconds or more, to provide a slow rise in pressure, thereby avoiding any possible damage to the blood cells which may occur with the rapid high pressure rises in the prior art devices. Preferably, the More preferably the inflation is held for a period less or equal to the period of inflation. Preferably, the bladder is made from vapour permeable material, and more preferably of material having greater elasticity than the garment material so that the bladder provides a more effective transmission of pressure during inflation for any given pressure. Preferably, the means for locating and securement of the foot garment include cushioning, for example, a foam backing. The cushioning, for example, foam prevents chafing and skin breakdown at the points of contact, which may be caused by the garment, when in use, by the garment pressing and rubbing against the skin surface during inflation and/or deflation of the bladder within, or by the garment being fitted tight around the foot. Preferably, the garment includes through holes or apertures through the garment and bladder to provide ventilation to the limb, during use. Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figs. 1a and 1b show plan views of garments according to the invention; Fig. 2 is a perspective view of a garment as worn on a foot; Fig. 3 is a schematic diagram of the bladder as shown in Fig. 1a as arranged around the foot when the garment is worn as in Fig. 2; Referring to Fig. 1a, a foot garment blank 10 is formed from two superposed sheets of plastics material 21 and 22, the inner material 21 preferably more elastic than the outer material 22. The sheets 21, 22 are high frequency welded together at their peripheries and internally in a pattern defining the bladder 14. The high frequency weld is located internally of the peripheries of the garment so that a hard edge consisting of the two material layers and weld join is avoided. This peripheral weld which is set back internally allows a soft edge to the garment 22 which has been shown to minimise the problems of chafing at the points of contact known to occur with the prior art garments. The outer less elastic material 21 is cut close to the peripheral weld line in order to provide only the softer more elastic material 22 edge in contact with the skin during use. Conveniently, the high frequency weld can be replaced by other available means of joining the materials, for example, ultrasonic welding, heat sealing or by adhesive bonding. An aperture 31 is provided on the outer material for connection to a pressure source. A heel section 30 is further attached to opposing sides of the blank 10 for location of a heel of a patient. To further add to the comfort of the user, the heel section includes a foam backing (not shown) to cushion the skin against chafing and skin breakdown at the heel sides during use of the garment. As shown in Fig. 2, the garment 10 is fitted to a foot by positioning the heel of the foot of a patient against the heel section 30 and then the garment is wrapped around the foot and held in place by suitable securing means, preferably cushioned as with the heel section. The securing means may have, for example, Velcro hook and pile material 20 on their respective edges or other similar securing means. The Velcro hook and pile material 20 is simply sewn or welded at its one edge to the garment edge. The bladder surface may have through apertures (not shown) for ventilation of the foot during use. In use, the bladder 14 within the garment is inflated slowly, typically for 2.5 seconds by a pressure source to apply compressive pressures, typically to a maximum of 130mmHg, over substantially the whole of the sole of the foot as well as the dorsi-medial and dorsi-lateral areas of the foot. The bladder, in use, is shown in Fig. 3. This gradual compression of the sole and dorsum regions of the foot is believed to stimulate a larger volume of blood than the known pulsed high pressure pumping devices which act locally only under the arch of the foot. Moreover, the gradual pressure application is very comfortable to the user since lower pressures are applied to a better effect. Additionally, the bladder may be held inflated for a period of time, typically 1 second to further enhance arterial flow. The bladder 14 is deflated by exhausting to atmosphere which is fairly rapid compared to the slow rate of inflation. The bladder is again inflated typically within a range of 30 to 60 seconds, as desired, in order to maximise the hyperaemic effect for increased arterial inflow and thereby venous outflow. The inflation/deflation cycle is carried out as long as treatment is required. A valve arrangement or similar, for example, solenoids may be used to control the inflation and deflation cycle and due to the requirement for slow pressure rise time and lower pressures a compressor alone is sufficient to provide the requisite pressurised air. The foot garment can be recommended for continual use to provide continual prophylaxis since it can be worn whilst sleeping due to its comfortable gradual compression action. The foot garment may be worn in conjunction with a calf or thigh garment for simultaneous stimulation of the venous blood flow or sequential stimulation i.e. starting from the foot, then calf, then thigh as appropriate or the foot garment may be used after actuation of a thigh or calf garment to "prime" the foot prior to its action.

Claims: A foot garment (10) comprising at least one bladder (14,18), and means to slowly inflate the bladder to provide gradual compressive pressure to the sole and to the dorsi-medial and dorsi-lateral areas (18) of a foot, followed by relatively rapid deflation of the bladder (14,18) characterised in that the bladder (14,18) is shaped to only engage the sole of a foot and the dorsi-medial and dorsi-lateral areas of the top of a foot. A foot garment (10) as claimed in claim 1, characterised in that the garment (10) includes only one bladder (14,18). A foot garment (10) as claimed in claim 1 or claim 2, characterised in that the bladder or bladders (14,18) are inflated over a period of 2 seconds or more, to provide a slow rise in pressure. A foot garment (10) as claimed in claims 1, 2 or 3 characterised in that inflation is held for a period of time before deflation, in the cycle. A foot garment (10) as claimed in claim 4 characterised in that the inflation is held for a period less or equal to the period of inflation. A foot garment (10) as claimed in any preceding claim, characterised in that the bladder (14,18) is made from vapour permeable material. A foot garment (10) as claimed in claim 6 characterised in that the bladder material is of greater elasticity than the garment material. A foot garment (10) as claimed in any preceding claim, characterised in that the means for locating and securing the garment include cushioning, for comfort. A foot garment (10) as claimed in any preceding claim, wherein the garment (10) includes through holes or apertures through the garment and bladder to provide ventilation to the foot.

Inventors: HAMPSON DAVID MARK, HUTFLESZ HEATHER ELIZABETH, SCHILD ROLF, HAMPSON, DAVID MARK, HUTFLESZ, HEATHER ELIZABETH, SCHILD, ROLF
Applicants: HUNTLEIGH TECHNOLOGY PLC
Application year: 1998
Main classification: A61H23
IPC codes: A61H23