GB2285749A

GB2285749A - Apparatus for applying limb compression

Info

Publication number: GB2285749A
Application number: GB9401247A
Authority: GB
Inventors: Rolf Schild; Denis Graham Melrose
Original assignee: Huntleigh Technology Ltd
Current assignee: Huntleigh Technology Ltd
Priority date: 1994-01-24
Filing date: 1994-01-24
Publication date: 1995-07-26
Anticipated expiration: 2014-01-24
Also published as: GB9401247D0; GB2285749B

Abstract

The apparatus comprises separate inflatable cuffs for the thigh and calf portions of the limb, inflation being cyclically controlled by means of a valve so that the thigh cuff 2 is inflated for a brief period first to promote filling of the lower leg with blood and is then deflated and the calf cuff 1 is inflated to promote movement of blood towards the heart. After a period, the thigh cuff is also inflated before both cuffs are deflated together at the end of the cycle. <IMAGE>

Description

LIMB COMPRESSION The present invention relates to an apparatus and a method for applying compression to the limb of a patient.

Intermittent pneumatic compression of the limbs has been used in the treatment of venous and lymphatic diseases of the extremities. A particular problem for which intermittent compress ion is recommended is to prevent venous stasis occurring during surgery and in other conditions. Venous stasis is known to cause deep venous thrombosis and pulmonary embolism; complications which can be serious, even lethal.

US-A-5,117,812 (Mcwhorter) discloses a compression device having a plurality of individual segments separated from each other. Each segment has a compression chamber for applying pressure to selected positions of the foot and leg of a patient, such as the foot, ankle, calf and thigh.

The foot segment is inflated first in order to facilitate or enhance movement of blood from the foot into the patient's leg and prevent trapping of fluid in the patient's limb during operation of the device. The other segments may then be sequentially inflated to compress the patient's leg from a distal location to a proximal location of the patient's limb relative to the heart. Such a sequence is intended to minimise the trapping of blood in the patient's limb while maximising the movement of blood through the limb.

It is an object of the present invention to provide an improved apparatus and method for promoting venous blood flow in the limb of a patient.

According to the present invention there is provided an apparatus for applying compression to the limb of a patient, the apparatus comprising: a first inflatable means to envelop an upper region of a limb, a second inflatable means to envelop a lower region of a limb; means for separately inflating said first and second inflatable means, the inflating means including control means for controlling the respective pressures in said first and second inflatable means such that said first inflatable means is inflated to a pressure to promote filling of the venous system in the limb distal of said first inflatable means while said second inflatable means is at a relatively lower pressure, and then said first inflatable means is deflated and said second inflatable means is inflated to a pressure to promote movement of fluid from the lower region of the limb to the upper region of the limb.

The present invention makes use of the appreciation that prior art techniques have concentrated on emptying the veins and have largely ignored the state of venous filling at the start of the inflation cycle, allowing only that there should be adequate time between inflationary periods to allow the veins to fill. In contrast, the present invention promotes filling as well as emptying of the veins, thereby providing a most effective defence against venous stasis.

The present invention seeks to establish in a recumbent patient some of the conditions that apply to that patient when standing. The volume of blood in the standing leg at rest is much larger than when that leg is recumbent. The vessels are filled, competent venous valves are closed, and normal conditions are set for the muscle pumps in the calf and thigh to work at an optimum. It is such conditions that the present invention seeks to provide when artificial means are used to promote normal function of the venous system in circumstances when this function may be disturbed, and particularly when the limbs are recumbent.

Normally, the first inflatable means is adapted to envelop the thigh of the patient's leg and the second inflatable means is adapted to envelop the calf. In such circumstances, the apparatus may include a component which ensures that the veins of the foot share in the process of filling and emptying.

According to a further aspect of the present invention there is provided a method of applying compression to the limb of a patient, the method comprising the steps of: a) locating a first inflatable means on the upper region of a limb and a second inflatable means on the lower region of a limb; and b) inflating said first and second inflatable means in a plurality of cycles, each cycle comprising the sequential steps of: i) inflating said first inflatable means to a pressure to promote filling of the venous system in the limb distal of said first inflatable means while said second inflatable means is at a relatively lower pressure; ii) deflating said first inflatable means and inflating said second inflatable means to a pressure to promote movement of fluid from the lower region of the limb to the upper region of the limb.

Preferred embodiments of the present invention will be described in detail, by way of example only, and with reference to the accompanying drawings of which: Figure 1 depicts a schematic representation of an apparatus according to an embodiment of the present invention; Figure 2 shows a side elevation of a leg to which the apparatus of Figure 1 is applied; and Figure 3 shows pressure graphs showing an inflation and deflation sequence of a preferred embodiment of the method of the present invention.

Figure 1 depicts schematically an embodiment of the present invention. A lower inflatable garment 1 and an upper inflatable garment 2 are provided for enveloping the lower and upper regions of a limb respectively. As shown in Figure 2, the lower and upper regions of the limb may comprise the calf and thigh of a leg. There is a controller 3 for sequentially inflating the garments 1 and 2.

Pressure supply lines 4a and 4b are located between garment 1 and the controller 3 and garment 2 and the controller 3 respectively. The controller 3 comprises a compressor 5, a regulator 6 and a timer 7 for controlling the inflation and deflation periods of the individual garments 1 and 2. The compressor 6 is a source of pressurized air and the regulator 6 is adjustable to provide a desired maximum pressure to lines 4a and 4b.

The garments 1 and 2 are connected to pressure supply lines 4a and 4b through valves 8a and 8b respectively. The valves 8a, 8b are controlled by the timer 7. A non-return valve 9 is located in pressure line 4a.

The inflation cycle which is applied to the apparatus of Figure 1 involves a first inflation cycle for promoting filling of the venous system in the limb and a second inflation cycle for promoting movement of fluid from the lower region of the limb to the upper region of the limb.

During the first inflation cycle, the timer 7 controls valve 8b to apply a pressure pulse from the controller 3 to the upper thigh by opening valve 8b to allow flow to garment 2. The valve 8b allows inflation via inflation port llb with the deflation port 12b closed. The pressure to which garment 2 is inflated is sufficient for the garment 2 to be effective as a tourniquet to temporarily constrict the veins and prevent or slow down flow of venous blood towards the heart. As the garment 1 is at a relatively lower pressure than the pressure to which garment 2 is inflated, venous blood from the extremities of the limb continues to flow into the region of the venous system distal of garment 2.Venous blood thereby collects in the region of the venous system distal of garment 1 and so the volume of blood in that region is increased. After approximately 5 seconds, valve 8b is closed to the supply line 4b and thigh garment 2 is deflated to atmosphere through exhaust port 12b.

The second inflation cycle is then initiated.

Approximately 2 to 3 seconds later, the timer 7 controls valve 8a to apply a second pressure pulse to the calf garment 1. Inflation of the calf garment occurs via inflation port ila with the deflation port 12a closed.

After approximately 5 to 7 seconds, a third pressure pulse is applied to the upper thigh garment 2 by closing valve 8b. The third pressure pulse lasts for approximately 7 to 8 seconds and inflation occurs by inflation port lib with the deflation 12b closed. Because the volume of blood distal of garment 1 has been increased by the first inflation cycle, the effect of the second inflation cycle in emptying the veins of blood is thereby increased. The increased movement of venous blood effected reduces the risk of complications due to venous stasis.

During the second part of the inflation cycle of approximately 12 seconds, the pressure in the lower calf garment 1 is maintained through the non-return valve 9.

This non-return valve ensures that inflation of the upper thigh garment 2 can only occur when air flows through the compressor 5 and not by reflux of air from garment 1. At the end of the second part of the inflation cycle, the timer 7 controls valves 8a and 8b to deflate the garments 1 and 2 simultaneously, exhausting to atmosphere via deflation ports 12a and 12b. The inflation and deflation of the total cycle is depicted graphically in Figure 3.

As shown in Figure 3, the cycle commences with compression of the thigh by inflation of the garment 2 to promote filling of the venous system in the limb.

Deflation occurs immediately after peak pressure is obtained in approximately 4 to 5 seconds. After approximately 2 seconds, the inflation of the calf garment compresses the calf of the leg for the remainder of the cycle to promote movement of fluid back towards the heart.

Thigh compression occurs approximately 6 seconds after the commencement of calf compression and lasts for approximately 7 seconds after which thigh and calf decompression commences. After approximately 70 seconds, the total cycle recommences.

Claims

1. An apparatus for applying compression to the limb of a patient, the apparatus comprising: a first inflatable means to envelop an upper region of a limb, a second inflatable means to envelop a lower region of a limb; means for separately inflating said first and second inflatable means, the inflating means including control means for controlling the respective pressures in said first and second inflatable means such that said first inflatable means is inflated to a pressure to promote filling of the venous system in the limb distal of said first inflatable means while said second inflatable means is at a relatively lower pressure, and then said first inflatable means is deflated and said second inflatable means is inflated to a pressure to promote movement of fluid from the lower region of the limb to the upper region of the limb.

2. An apparatus according to claim 1, wherein said control means additionally re-inflates said first inflatable means after inflating said second inflatable means.

3. An apparatus according to claim 2, wherein said first and second inflatable means are coupled to be inflated directly from a common source, the apparatus further including non-return valve means to prevent any deflation of said second inflatable means when inflating said first inflatable means.

4. An apparatus according to claim 3 including a respective pressure supply line feeding from said source to each of said first and second inflatable means, the non-return valve means being located in the pressure supply line to said second inflatable means.

5. An apparatus according to any one of claims 1 to 4, wherein said first inflatable means is adapted to envelop the thigh of the patient's leg and said second inflatable means is adapted to envelop the calf of the patient's leg.

6. An apparatus according to any one of claims 1 to 5, wherein said inflating means includes a compressor and a pressure regulator.

7. An apparatus according to any one of claims 1 to 6 wherein said control means includes timer means for controlling the timing of inflation of said first and second inflatable means

8. An apparatus according to any one of claims 1 to 7, wherein said control means is arranged to cause repetition of a series of operations by which said control means controls the respective inflation pressures in said first and second inflation means.

9. A method of applying compression to the limb of a patient, the method comprising the steps of: a) locating a first inflatable means on the upper region of a limb and a second inflatable means on the lower region of a limb; and b) inflating said first and second inflatable means in a plurality of cycles, each cycle comprising the sequential steps of: i) inflating said first inflatable means to a pressure to promote filling of the venous system in the limb distal of said first inflatable means while said second inflatable means is at a relatively lower pressure; ii) deflating said first inflatable means and inflating said second inflatable means to a pressure to promote movement of fluid from the lower region of the limb to the upper region of the limb.

10. A method according to claim 9 including the step of re-inflating said first inflatable means after inflating said second inflatable means.

11. A method according to claims 9 or 10 including the step of allowing said first and second inflatable means simultaneously to deflate after said step of re-inflating said first inflatable means.