GB2403418A - Medical device for reducing body temperature - Google Patents

Abstract

Tissue cooling apparatus comprises a member conformable to an external part of the human body 10, location means to place the member at the desired located 15, and a hand portable coldness generator for rendering the apparatus cold on demand (37, Fig 4). One use of the apparatus is to apply immediate cooling after a heart attack.

Description

240341 8 P709SS9GB Medical Device This invention relates to a device for

reducing the temperature of human body tissue, and particularly to a device for directly or indirectly reducing the temperature of the heart in the event of acute coronary syndrome (ACS) or acute myocardial infarction (AMI).

ACS and AMI are common occurrences in the developed world. AMI is usually due to occlusion by thrombus of a coronary artery. If treated promptly by medical or surgical intervention, any damage to heart tissue due to ischaemia can be minimized, and the patient can be expected to recover notwithstanding that some tissue damage may be permanent. In order to restrict myocardial damage to a minimum, it is desirable for the blood supply to the heart muscle to be restored as soon as possible, and this is typically done by either thrombolytic drugs ('clotbusters') or by cardiac catheterization in a hospital (angioplasty). The risk of permanent myocardial damage will increase until effective treatment (thrombolysis or angioplasty) is applied to the patient.

During conventional heart surgery it is known to stop the heart, whilst preserving heart muscle using a suitable cardioplegia solution. The risk of organ damage can be reduced by cooling the body, but suitable cooling equipment is relatively massive, expensive and requires the heart to be stopped. Such facilities are available only at specialist cardiac surgery units.

What is required is a means of preventing or restricting damage to the heart in the event of AMI and possibly ACS, until the patient can be treated at a suitably equipped medical unit.

According to the invention there is provided tissue cooling apparatus comprising a member conforming or conformable to an external portion of the human body, means to place said member at a desired location on the human body, and a hand-portable coldness generator for rendering said member cold on demand.

Such apparatus may be used to apply cooling to a region of the human body in order to restrict tissue damage resulting from AMI. Cooling may be applied directly to the heart by cooling the chest and thorax. Indirect cooling of the heart may also be achieved by cooling an area of high venous blood flow, for example in the thigh region.

In one embodiment, the member is in the form of a pad or jacket which can be placed over and/or around the chest and heart so as to provide local cooling in the event of prolonged myocardial ischaemia. The means to locate the member may be inherent in the shape thereof, or may for example be provided by printed material on the member.

The coldness generator can be any suitable device adapted to generate cold on demand, for example a combination of suitably reactive materials, discharge of a pressurized volatile substance, or an electrically powered refrigeration unit.

The member may typically comprise a sealed enclosure containing a material having a high conductivity. The material is preferably in liquid form in order to aid conformability, but particulates are also suitable. Rigid materials may also be appropriate if in the form of a flexible net or mesh.

Preferably the apparatus is self-contained, the coldness generator being an integral component which can be activated on demand, for example by operating a trigger mechanism.

In a preferred embodiment the apparatus further includes retention means to hold the member in a desired position and/or orientation. Such retention means may for example comprise straps to encircle the body and/or adhesive components. Preferably such retention means are in use fixed to the member, and most preferably the retention means are integrally affixed to the member during manufacture of the device.

The apparatus may be insulated on the external side so as to ensure that the tissue cooling effect is maximized. A layer of insulating material may be directly applied to the external side of the member, or alternatively an insulating jacket may be provided, which simultaneously serves to locate and/or to retain the apparatus in place.

Means may be provided whereby the effect of such insulation may be varied in use to achieve a desirable cooling effect. The insulation may for example have removable layers or panels so as to adapt a 'standard' apparatus to humans of different body mass.

It will be apparent that a self-contained apparatus according to the invention could be made relatively inexpensively, and widely provided in the community. Such an ] O apparatus could for example be carried on an ambulance or by doctors or could be used in a hospital, and activated on demand. The apparatus would also be suitable for use by unskilled persons, with e.g. appropriate instructions printed on the exterior thereof. Use of the device is not dependent on exact knowledge of the location of the heart.

The device may include an external visual indicator of body temperature, for example a thermometer or a temperature sensitive patch adapted to indicate the normal and cooled state by colour change. Such an indicator may also indicate excessive coolness The apparatus may further include other devices, such as integral defibrillator pads connectable to compatible defibrillator apparatus. Such an adaptation permits rapid defibrillation without disturbing the apparatus. The apparatus may also be adapted to provide non-invasive indications of patient condition by the incorporation of suitable sensors; these include, but are not limited to, measurement of blood pressure, cardiac output, arterial oxygen saturation, electrocardiogram, pulse rate, respiratory rate and body temperature.

The coldness generator may be a 'one-shot' device adapted to rapidly reduce the temperature of the member, or may be controllable by the user to give partial exhaustion thereof. The generator may be adapted for repeated actuation until exhausted, so as to permit the member to remain cold for the maximum sustainable period. Furthermore the generator may be attachable to the member, and thus removable and replaceable. The member may include an integral coldness generator, and, optionally a top-up port to permit coldness to be maintained when the integral generator has been exhausted.

The coldness generator may be automatically controlled after operation of the trigger, for example by a temperature sensitive device adapted to increase or re-start output according to pre-set maximum and minimum temperatures. Such control is desirable in order to reduce and maintain temperature to a predetermined stable level.

The inner or underside of the member may have a layer or coating adapted to improve l0 heat transfer. For example a semi-liquid gel coat may be provided to help overcome the insulating effect of human body hair.

The skilled man will determine the volume and/or area of the member according to the intended use. It may for example be desirable to have different sizes of apparatus because of the variations in human body mass. In particular it may be desirable to extend a cooling jacket over the lower chest and abdomen in order to maintain a desired temperature.

Furthermore the skilled man will determine the constituents of the coldness generator in order to achieve a desirable drop in body temperature in the affected region. A stable reduction in the range 4-6 C is desirable.

The skilled man will also take into account other necessary factors, such as the need to permit adequate medical monitoring of the patient whilst the apparatus is in place, and the need to permit the patient to breath freely.

Other features of the invention will be apparent from the following description of a preferred embodiment shown by way of example only in the accompanying drawings, in which: Figure I is a plan view of a first embodiment of the invention; Figure 2 is a side elevation of the embodiment of Figure 1; Figure 3 is a partial section through the thickness of the device of Figure 1; Figure 4 is an alternative embodiment of the invention.

With reference to Figures 1-3 a half-vest 10 is provided for application to the chest of a human. The half-vest includes cut-outs 11,12 for neck and arms, which are useful in positioning, and for preventing movement in use.

Side straps 13,14 include suitable fasteners 15 at the ends, for example hook/loop material, to permit the half-vest to be secured around a patient's torso.

Elastic portions 16 are included in the straps to permit a patient to breath normally.

Preferably rise and fall of the chest should be substantially unrestricted, and accordingly the elastic material preferably has a rather small increase in load per unit extension.

The half-vest is in the form of a pouch containing a material adapted to be made cold, and having a suitable capability of retaining and transmitting coldness introduced via a port 17. The material is for example a liquid or a solid particulate adapted to allow at least the underside of the half-vest to conform to the patient's body.

As illustrated in Figure 3 the pouch comprises a relatively thin walled member 21, for example of a suitable plastics material, an outer covering layer of insulating material 22. A conformable particulate 23 is enclosed.

The half-vest illustrated in Figures 1-3 is reusable in conjunction with a fresh supply of coldness. It has a simple construction, and can be adapted to a conventional freezing spray via the self-sealing port 17, which may at least partially inflate the pouch.

Plainly the construction of the pouch can be adapted to suitable heat transmission characteristics, and the thin wall on the underside may not extend over the entire surface area.

A second, disposable, embodiment is illustrated in Figure 4. A welded plastic pouch 31 includes a partial neck cut-out 32 and self adhesive tabs 33. A target 34 is included to aid correct positioning. An arrow 35 indicates orientation, and instructions for use 36 are provided on the exterior.

l O An integral aerosol coldness generator 37 is attached to the pouch, and is activated by a trigger 38.

In the event of a heart attack, the pouch 31 is simple to apply and operate. It may be contained prior to use in a seated package which typically may have a shelf-life of several years. Such an embodiment is inexpensive to manufacture, and could be made widely available in public places.

It may also be beneficial to apply cooling to the back of a patient, in which case the half-vest of Figure I could plainly be made as a full vest. Cold capacity by way of a volume of material can be provided throughout the vest, or alternatively the rear side may comprise a cold member adapted to transfer heat to a cold sink at the front side.

Such a full vest is particularly effective in cooling the lungs, and thus all blood passing to the heart. Cooling of the neck and upper arms may also be desirable.

A device comprising a heat conductive jacket or pouch, and a separate hand portable cold sink is also within the scope of the present invention.

Claims (10)

1. Claims 1. Tissue cooling apparatus comprising a member conforming or

   conformable to an external portion of the human body, location means to place the member at a desired location on the human body, and a hand-portable coldness generator for rendering said member cold on demand.
2. 2. Apparatus according to claim I wherein said coldness generator is integral with said member.
3. 3. Apparatus according to claim 2 and further including a top-up port for attachment of a secondary source of coldness.
4. 4. Apparatus according to any preceding claim wherein said coldness generator is selfpowered, and includes a trigger for activation thereof.
5. 5. Apparatus according to any preceding claim and further including a thermostat to control the output of said coldness generator.
6. 6. Apparatus according to any preceding claim and further including retention means to hold said member in a desired position on the body.
7. 7. Apparatus according to any preceding claim and further including insulation on at least a portion of the exterior side thereof.
8. 8. Apparatus according to any preceding claim wherein said location means comprise the peripheral shape of said member.
9. 9. Apparatus according to any preceding claim and further including integral defibrillator means adapted to be powered by an external source.
10. 10. Apparatus according to any preceding claim and further including sensors adapted to provide an indication of one or more of blood pressure, cardiac output, arterial oxygen saturation, pulse rate, respiratory rate and body temperature.