WO2003063960A2

WO2003063960A2 - Improvements relating to medical devices

Info

Publication number: WO2003063960A2
Application number: PCT/GB2003/000398
Authority: WO
Inventors: John William Mckee; K. Michael Sloane; Paul Michael Diamond
Original assignee: Amtec Medical Limited
Priority date: 2002-02-01
Filing date: 2003-01-31
Publication date: 2003-08-07
Also published as: AU2003207010A1; WO2003063960A3

Abstract

An integral unit for use in the electrical stimulation of a human or animal body, particularly for preventing circulatory conditions is described. It comprises one or more electrodes integrated with a bandage housing, the housing being adapted to locate and secure the unit on a selected portion of the human or animal body. Also described is a detachable electrode strip for use with an electrical stimulation unit. It comprises a sheet having at least one electrode pad, at least one terminal point and at least one connecting conductor which connects the at least one electrode pad to the at least one terminal point. The unit and strip are preferably disposable, which therefore provides advantages with regard to sterility, as well as ease of use. The present invention provides a clean and efficient system for DVT and similar apparatus.

Description

Improvements Relating to Medical Devices

This invention relates to an electronic nerve and muscle stimulator.

The most significant complication arising from deep vein thrombosis (DVT) is pulmonary embolism. Pulmonary emboli are recognised as most common fatal complication following surgery or trauma involving the lower extremities. Pulmonary emboli are the principal or major contributory factor in approximately fifteen to thirty percent of deaths of hospitalised patients.

Deep vein thrombi predominantly form in the deep veins of the legs which are surrounded by the gastrocnemius and the soleus muscle groups . The thrombi initially form distally in the deep veins and grow proximally prior to their potential release as emboli. Contraction of the gastrocnemius and the soleus muscle groups activate the body's skeletal muscle pump by compressing the deep veins and mechanically pushing blood back toward the heart .

During surgery, the body's skeletal muscle pump can be compromised due to the effects of general anaesthesia and paralytic agents administered to facilitate, for example, intubation. This compromise of the skeletal muscle pump can lead to stasis of blood in the deep veins, formation of deep vein thrombi, and ultimately the formation of emboli. This situation is further aggravated as surgical patients tend to be non-ambulatory for a significant period of time after surgery. Without moving the skeletal muscle pump is only marginally effective. Accordingly, prevention of the blood stasis in the deep veins during surgery and subsequent augmentation of blood flow in the post- surgical period represents a good opportunity for preventing the formation of DV s .

Such lack of efficient or effective venous flow from the legs can result in other problems which, while they may not be life threatening, are associated with significant discomfort and are aesthetically unappealing, e.g. ankle edema and edema associated with venostatis and varicose veins. Effective muscle pumping can significantly reduce the morbidity associated with these conditions also.

The problem of deep vein thrombosis (DVT) and other similar embolisms are well known and described in the art, such as in WO 99/53996A, US 5358513, US 5566422, US 5782893 and US 6002965.

Electrical stimulation of muscle groups of the lower extremities has been shown to be effective for preventing DVT. A number of electrical stimulation devices exist and have been used to cause muscle contractions. Included in this class of electrical stimulating devices are the transcutaneous electrical nerve stimulators commonly known as TENS units. TENS units have been primarily utilised in post-surgical or non-surgical situations for the reduction or minimisation of pain. The TENS units are designed to block pain at the level of the nerve endings .

Present apparatus for this requires a number of different units and devices to be brought together for fitting, etc. This can be cumbersome and require unnecessary dexterity where medical advisors are concentrating on other matters. The present apparatus can often have loose leads and pipes, which restrict the necessary movement of the patient. They can also cause a trip hazard in the operating theatre and can be obstructive for the personnel using the equipment.

US 3472233 describes an electrical muscle stimulating system having an integrated body contact electrode and electrical pulse generator circuit. However, it also involves sponge contacts and wires, which are no longer clinically suitable. In one aspect of the present invention there is provided an integral unit for use in the electrical stimulation of a human or animal body, particularly for preventing circulatory conditions, comprising one or more electrodes integrated with a bandage housing, the housing being adapted to locate and secure the unit on a selected portion of the human or animal body.

The integral unit of the present invention may be disposable. The detachable unit of the present invention therefore provides advantages with regard to sterility, as well as ease of use. A disposable- unit also prevents any cross contamination from one patient to another, and eliminates cleaning of the device between each use. The unit can be disposed of using standard known techniques such as incineration etc.

The or each electrode can be integrated with the bandage housing by various known methods such as printing, screen printing, weaving, stitching, etc. Conducting (usually metallic) 'inks' able to provide the electrical connection are well known in the art e.g. silver silver chloride. Other metals include copper PCB tracks, aluminium and bronze, etc.

The bandage housing can be formed of any suitable bandage material, such as that well known in the art and available off the shelf . The bandage housing preferably includes integral fastening means to secure it to the relevant portion of a human or animal, although separate means such as pins, adhesive tape, etc. could also or alternatively be used. Integral fastening means conjoinable with the bandage housing, such as Velcro^® fasteners or adhesive strips, are all well known in the art.

The integral unit can further comprise a backing sheet which covers the at least one electrode pad. This backing sheet may be peeled off before use and may be used to protect the electrode pad, and keep it clean.

The integral unit is therefore immediately ready for use and application to a patient or user, with the minimum of additional preparation for use.

The present invention is suitable for use with a stimulating power source having external electrical terminals. Preferably, the power source is in a housing being elongate in shape. The housing could provide additional physical support for the electrode (s) . The housing may support one, two or more electrodes or electrode contact points .

In one embodiment of the present invention, the power source is integral with the at least one electrode and the bandage housing.

According to a second aspect of the present invention, where the power source is not integrated, the power source may also be usable with a detachable electrode strip, being preferably flexible, and which comprises a sheet having at least one electrode pad, at least one terminal point and at least one connecting conductor which connects the at least one electrode pad to the at least one terminal point .

Preferably, the or each electrode pad, terminal point and connecting conductor are all provided on the same side of the sheet. This provides advantages in simplicity of construction because all of the electrically conducting components are provided on the same side of a sheet.

Also preferably, there are one or more cuts in the sheet to allow a portion of the sheet bearing said at least one terminal point to be folded relative to the remainder of the sheet so forming a terminal tab which can then be placed in contact with a terminal of the power source. The terminal tab can therefore stand at an angle to the plane of the sheet and preferably extends from the side of the sheet which is not provided with the at least one electrode pad.

The detachable electrode strip can further comprise a backing sheet which covers the side of the flexible sheet provided with the at least one electrode pad, at least one terminal point and at least one connecting conductor. This backing sheet is removable prior to use of the strip. The detachable electrode strip may comprise two electrode pads, each connected to a- separate terminal point by a separate connecting conductor. In one embodiment, the detachable electrode strip may be elongate in shape comprising an elongate flexible sheet having a top edge, a bottom edge and two side edges. The two electrode pads may be positioned towards opposite side edges of the elongate flexible sheet . Preferably the terminal points are positioned closer to the respective side edges of the flexible sheet than their associated electrode pads. Preferably, the cuts in the flexible sheet are such that the two terminal tabs formed extend from the plane of the flexible sheet so that the terminal points face towards each other. The distance between the electrode pads may be varied. This will depend on, e.g., the size of the muscle to be electrically stimulated. The size of the muscle will depend, inter alia, on the type of muscle and the age of the patient. Thus the present invention also provides a kit of detachable electrode strips having a variety of electrode pad- electrode pad distances.

In the preferred embodiment of the electrode strip, the housing of the power source is elongate in shape and has two sides; and the detachable electrode strip has two electrode pads and has two terminal tabs which extend from the plane of the detachable electrode strip so that the terminal points face towards each other. In use one side of the housing is placed against the side of the detachable electrode strip not provided with the electrode pads. The housing is positioned in between the extended terminal tabs so that electrical contact is made between these terminal tabs and the corresponding terminals on the housing. The corresponding terminals on the housing may be positioned on the side of the housing opposite to that placed against the detachable electrode strip.

The terminal points may be manually pressed against the terminals on the power supply to ensure electrical contact . The terminal points may be coated in a non-permanent conductive adhesive to ensure constant electrical contact between the electrode pads and the terminals of the power supply. This adhesive may also help to hold the electrode strip in place. The adhesive is such that the electrode strip may be easily removed from the housing containing the power supply by hand.

Therefore the present invention also provides a power source unit and electrode strip combination wherein the power source unit comprises a housing containing a power source and having two external terminals, and a detachable electrode strip as described above.

The detachable electrode strip may be disposable. The detachable electrode strip of the present invention therefore provides advantages with regard to sterility. The electrode components of the detachable electrode strip may be recycled once the strip has been used.

For all aspects of the invention, the power source is preferably a battery, more preferably a rechargeable battery. A charger unit could be used. The charger unit could have lights which indicate the degree to which the source is charged, and be convenient for storage in a theatre prep room, intensive care unit, other departments of a medical facility, or at home or whilst travelling etc., and can be placed in a corner or mounted on a wall . The lights help the user to decide if the source will last throughout the surgical procedure.

The electrode active material of the electrode or electrode pad may be any suitable material such as - Ag/AgCl . This can be disposed onto the substrate using known methods such as screen printing, e.g. as shown in US 5337748. The connecting conductor and the terminal point on the backing sheet may be made of the same material as the electrode or else they may be made of other suitable conducting materials.

Thus, another aspect of the present invention is a method of preventing deep vein thrombosis and similar conditions comprising attaching at least one power source and electrode strip as hereinbefore described to the leg of a patient and applying pulsed electric current through the or each electrode strip to the relevant muscle. The at least one electrode preferably comprises a conductive material to form a layer of electrode and a layer of conductive gel. The electrode pad may also include a current distributive layer, such as carbon as described in WOO0/27467A. The layer of electrode active material can be positioned on, within and/or under the bandage, with the layer of carbon positioned on top of the layer of electrode active material and the layer of conductive gel placed on top of the layer of carbon. In use, the layer of conductive gel is placed in contact with the skin of the patient. Suitable conductive gels are well known.

Preferably, a predetermined amount of gel is used per electrode or electrode pad. This ensures that an accurate amount of gel is used, i.e. no gel is wasted and there is sufficient gel for conduction purposes. This also simplifies the process for treating the patient as gel need not be applied to " the patient's skin as a separate action.

In an embodiment of the present invention the integral unit or electrode strip is provided with an additional electrode terminal point which, when not connected to the power source, is electrically independent of the at least one other electrode. This terminal point is provided as a safety measure. Unless this terminal point comes into electrical contact with a corresponding terminal on the power source, the power source will not provide power to the electrodes or electrode pads. This helps to ensure that electrical current is not supplied to the muscles accidentally.

The bandage housing is preferably provided with a pocket arrangement so-shaped that it can permanently or separably hold the power source. In use, the power source, if not integral, is placed into the bandage and against the at least one electrode or electrode pad, and the electrodes or electrode pads can be manually pressed against the terminals on the housing. With the power source in place the bandage is applied to the patient's leg (pulled up, if in the form of a sock or wrapped round the leg if in the form of a standard bandage or cuff) so that the electrodes or electrode pads are positioned along the muscle to which the electrical pulses are to be applied. If there is a safety terminal point on the unit or power source, a pulse current will not be applied to the muscle until the contact has been made between the safety terminal point and a corresponding terminal on the power source.

The present invention can be used on patients when conscious or under anaesthetic.

For application to the leg, the invention works by directly stimulating the posterior muscles of the calf, gastrocnemius and soleus. It causes the gastrocnemius muscle to contract at a pulse of for example twelve per minute and contracts the venous sinuses, particularly the popliteal vein, thus allowing sufficient calf filling between pulses. This action causes brisk plantar flexion at the ankle, which provides a physical sign to the surgeon ^■ that the invention is working.

Thus, according to another aspect of the present invention, there is provided a method of preventing deep vein thrombosis and similar conditions comprising attaching the integral unit as hereinbefore described, and any separate power source, to the leg of a patient and applying pulsed electric current to the calf muscle.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a first integral electrode-bandage unit according to one embodiment of the present invention;

Figure 2 is a perspective view of a power source of stimulation for use with the unit of Figure 1;

Figure 3 is a cross-sectional view of the unit of Figure 1 along line AA, and the handset of Figure 2;

Figure 4 is an enlarged diagrammatic view of the central portion of the unit in Figure 3;

Figure 5 is a side view of the bandage of Figure 1 and handset of Figure 2 in use around a leg; Figure 6 is a perspective view of a second integral electrode-bandage of the present invention;

Figure 7 is a plan view of an electrode strip according to another embodiment of the present invention;

Figure 8 is a perspective view of a power source housing for the electrode strip of Figure 7;

Figure 9 is a diagrammatic side view of the housing with the strip thereon;

Figure 10 is a side cross-sectional view of the housing and electrode strip in a bandage housing; and Figure 11 is a diagrammatic side view of the combination of elements shown in Figure 10 in use on a leg.

Referring to the drawings, Figure 1 shows an integral unit 2 for use in the electrical stimulation of a human or animal body. The unit 2 includes two electrodes 4 integrated with a bandage housing 6. The housing 6 is adapted to locate and secure the unit 2 around a selected portion of the human or animal body.

The electrode active material of the electrodes 4 is a conductive weave within the standard bandage material of the bandage housing 6. Thus the electrodes 4 present an upper face (as seen) and an obverse face 8 (shown in Figure 3) , which allows for electrical conductance through the housing material 6.

The electrode active material is formed of a conductive material . Over the electrode material carbon pads 10 are added. The carbon pads 10 are then coated in an adhesive conductive hydrogel 12 (Figure 4) . This gel 12 is the patient contact element and is provided with a biocompatability certification.

Over the electrodes 4 is located a sterile sheet 14, which is outlined in Figure 1 and also shown in Figure . The sheet 14 is removable when the unit 2 is required. It preserves the sterility of the gel 12 and electrodes 4 prior to use.

Figure 2 shows a power source housing 20. It comprises a re-chargeable internal battery pack as the power source, two printed circuit boards (PCB) , a resin vacuum casting case, a user selectable rotary switch 24, a state of operation LED, charging unit interface contacts, and two metallic interface contacts 22.

The battery pack could consist of rechargeable or disposable battery units of sufficient capacity. This battery pack provides the power for the two PCBs . One PCB provides battery pack charge indication. This charge indication, or battery level capacity, is displayed by lights located on a separate charging unit (not shown) . Interfacing between the two modules is provided for by "mating" interfacing contacts, located on both the housing 20 and the charging unit .

This housing 20 is powered solely from the internally housed battery pack during operation, eliminating any risk of the patient co ing into contact with the live supply. The housing cannot be attached to the patient while connected to the mains supply charging unit, and as such, is considered a battery operated device.

The bandage housing 6 can be manufactured from "off the shelf" bandage material and use any form of fastenings or couplings such as Velcro^® hook and loop strips 26 stitched into it.

The bandage housing 6 includes a sleeve portion 30 into which the power source housing 20 is insertable (as shown by arrow B in Figure 1) . Preferably the sleeve 30 is formed from stretchable and/or elasticated material, and/or provides a friction fitting, to secure the housing 20 with the bandage housing 6 during use.

In use, a charged power source housing 20 is located in the bandage sleeve 30. A covering strip 14, which may or may not be sterile, is removed from electrodes 2, and the electrodes 2 are matched to the electrode terminals 22 of the power source housing 20 to interface the terminals as shown in Figure 3. The complete unit is then strapped to the patient's lower leg 34 (Figure 5) utilising the Velcro^" strips 26 as fasteners to provide patient skin contact with the gel 12 on the electrodes 4.

The user and/or medical advisor can then operate the rotary switch 24 to provide the desired electrical impulse to the leg muscles. The impulse is generated through the rotation of the rotary switch 24 leading to a power supply from the battery pack to the PCB. In the rotation of the switch 24 a series of load inputs is also activated determining the output of the apparatus. This output is sent towards the electrode contact points in which they are relayed through the electrodes 4 to the patient. Once finished, the unit 2 can be disposed of and the housing 20 recharged.

Figure 6 shows a first alternative unit 40 of the present invention having two electrodes 42 integrated with a bandage housing 44, wherein conductive tracks 46 extend from each electrode 42 to power source contact points 48 which can interface with contact points on a different power source housing arrangement. Indeed, the electrodes can be tracked to any suitable contact points on the bandage housing.

Figure 7 shows an electrode strip 52 for use with an electronic nerve and muscle stimulator, the strip being flexible and comprising sheet 56 having two electrode pads 58, two terminal points 60 and two connecting conductors 62 which connect the two electrode pads 58 to two terminal points 60.

The sheet 56 is manufactured from a polyester substrate designed to closely mimic the contours of the housing referred to below. On to this substrate 56 are screen printed the conductive pads 58, terminal points 60, and tracks 62, one at each end of the electrode strip 52, and which interface between the housing output signal and the patient contact element. Over the electrode pads 58 an adhesive conductive hydrogel is added. This gel .is the patient contact element and is provided with a biocompatability certification.

The electrode strip 52 also has thereon a separate conductive pad 68 as a safety switch. This separate pad 68 is also manufactured from screen printed silver silver chloride.

Over the strip 52 is located a sterile sheet (not shown) which is removable when the strip 52 is required. It preserves the sterility of the gel and pads 58 prior to use.

A power source housing 80, or stimulating unit, for use with the strip 52, is shown in Figure 8. It comprises a rechargeable internal battery pack as the power source, printed circuit boards (PCB) , a resin vacuum casting case, a user selectable rotary switch 86, a state of operation LED, metallic charging unit interface contacts, metallic patient interface contacts 82, and a metallic, normally open, safety switch 84. In operation, the power source is similar to that as hereinbefore described.

The bandage harness 90 shown in Figures 10 and 11 can be manufactured from "off the shelf" hospital bandage material with Velcro hook and loop strips 92 stitched into it. This harness 90 locates and maintains the housing's 80 position on the patient's calf 94 during normal- operation.

Both ends of the housing 80 protrude from the bandage 90 to facilitate the electrode strip 52 contact requirements, along with the externally mounted rotary switch 86 to allow stimulation level selection.

In use a charged housing 80 is located in the bandage 90. A sterile covering strip is removed from a sterile electrode strip 52, and the strip 52 is applied to the housing 80 to interface the terminals as shown in Figure 9. The complete unit is then strapped to the patient's lower leg 94 utilising the Velcro^" strips 92 as fasteners to provide patient skin contact with the gel 16 on the electrode pads 58 of the strip 52.

The user and/or medical advisor can then operate the housing 80 as hereinbefore described.

The present invention provides a clean and efficient system for DVT and similar apparatus.

Claims

1 Claims 2

3 1. An integral unit for use in the electrical

4 stimulation of a human or animal body,

5 particularly for preventing circulatory

6 conditions, comprising one or more electrodes

7 integrated with a bandage housing, the housing

8 being adapted to locate and secure the unit on

9 a selected portion of the human or animal body. 10

11 2. A unit as claimed in Claim 1 wherein the unit

12 is disposable. 13

14 3. A unit as claimed in Claim 1 or Claim 2 wherein

15 the bandage housing includes integral fastening

16 means to secure it to the relevant portion of a

17 human or animal 18

1.9 4. A unit as claimed in any one of the preceding

20 Claims further comprising a stimulating power 21 source having external electrical terminals. 22

23 5. A unit as claimed in Claim 4 wherein the power

24 source is on an elongate housing. 25 6 6. A unit as claimed in Claim 4 or Claim 5 wherein 7 the power source is integral with the at least 8 one electrode and the bandage housing. 9 0 7. A unit as claimed in any one of Claims 4 to 6 1 wherein the power source is a rechargeable 2 battery.

8. A unit as claimed in any one of the preceding Claims wherein the at least one electrode comprises a conductive material to form a layer of electrode and a layer of conductive gel.

9. A unit as claimed in Claim 8 wherein the electrode pad includes a current distributive layer.

10. A unit as claimed in Claim 8 or Claim 9 wherein a predetermined amount of gel is used per electrode.

11. A unit as claimed in any one of the preceding Claims wherein the unit further comprises a backing sheet which covers the at least one electrode pad prior to use.

12. A unit as claimed in any one of Claims 4 to 11 wherein the bandage housing is provided with a pocket arrangement so-shaped that it can permanently or separably hold the power source.

13. A flexible electrode strip for use with a human or animal electronic nerve and/or muscle stimulation unit, which strip comprises a sheet having at least one electrode pad, at least one terminal point and at least one connecting conductor which connects the at least one electrode pad to the at least one terminal point.

14. An electrode strip as claimed in Claim 13 wherein the or each electrode pad, terminal point and connecting conductor are all provided on the same side of the sheet.

15. An electrode strip as claimed in Claim 13 or Claim 14 wherein there are one or more cuts in the sheet allow a portion of the sheet bearing said terminal point to be folded relative to the remainder of the sheet.

16. An electrode strip as claimed in any one of Claims 13 to 15 wherein the strip further comprises a backing sheet which covers the side of the flexible sheet provided with the at least one electrode pad, at least one terminal point and at least one connecting conductor.

17. An electrode strip as claimed in any one of Claims 14 to 16 wherein the strip comprises two electrode pads, each connected to a separate terminal point by a separate connecting conductor.

18. An electrode strip as claimed in any one of Claims 14 to 17 wherein the strip is for use with a power source.

19. An electrode strip as claimed in any one of Claims 18 wherein the power source is in a housing .

20. An electrode strip as claimed in any one of Claims 13 to 19 wherein the housing is elongate in shape and has two sides; and the electrode strip has two electrode pads and has two terminal tabs which extend from the plane of the detachable electrode strip so that the terminal points face towards each other.

21. An electrode strip as claimed in any one of Claims 13 to 20 wherein the terminal points are coated in a non-permanent conductive adhesive.

22. An electrode strip as claimed in any one of Claims 13 to 21 wherein the strip is disposable.

23. A power source unit and electrode strip combination for electrical stimulation of the human or animal body, wherein the power source unit comprises a housing containing a power source and having two external terminals, and the electrode strip is described in any one of Claims 13 to 22.

24. A method of preventing deep vein thrombosis and similar conditions comprising attaching the integral unit as described in any one of Claims 1 to 12 to the leg of a patient and applying pulsed electric current through the or each electronic pad to the relevant muscle.

5. A method of preventing deep vein thrombosis and similar conditions comprising attaching at least one power source and electrode strip as described in any one of Claims 13 to 22 to the leg of a patient and applying pulsed electric current through the or each electrode strip to the relevant muscle .