WO1989005129A1

WO1989005129A1 - Apparatus for heating or cooling the body

Info

Publication number: WO1989005129A1
Application number: PCT/GB1988/001058
Authority: WO
Inventors: Barrie Blake-Coleman
Original assignee: Public Health Laboratory Service Board
Priority date: 1987-12-04
Filing date: 1988-12-05
Publication date: 1989-06-15
Also published as: GB8728360D0; EP0370073A1; AU2814589A

Abstract

Apparatus for heating or cooling body regions for therapeutic or diagnostic purposes includes one or more Peltier elements (10). With one surface of the Peltier element established in thermal contact with the body region either directly or via a heat exchanger, a controlled current is passed through the element. The opposite face of the Peltier element is connected with a heat sink which may comprise an air cooled fin array.

Description

APPARATUS FOR HEATING OR COOLING THE BODY

This invention relates to apparatus for heating or cooling defined regions of the human or animal body.

It is known that in certain medical conditions, such as auto-immune diseases of the joints and post-operative trauma, significant palliative or therapeutic benefit can be obtained from thermal cycling of the affected region. Thus, cooling of a joint affected by rheumatoid arthritis results in rapid vaso-constriction which reduces swelling and moderates pain. Since the recovery to full vase-dilation is relatively slow, a sustained benefit is achieved. In other conditions a periodic cooling and heating cycle is believed to be therapeutic. This is known as contrast therapy and its advantages are well documented.

In some circulatory disorders and neurological problems, the measured response of a body region to an applied hot or cold stimulus is a valuable diagnostic tool. For example, vascular response can be investigated by the controlled heating or cooling of the palm of the hand with blood temperature being monitored at the back of the hand by thermographic techniques.

Hitherto, controlled heating or cooling of regions of the human body has been carried out using techniques including ice-packs and hot wax. Difficulties have been encountered in maintaining precisely constant temperatures over a period of time. With diagnostic and other techniques requiring measurements to be made at a range of temperatures, the apparatus currently available is generally cumbersome and time consuming in operation. Often, accuracy of temperature control is not as good as would be desirable and in certain cases the techniques are painful.

It is an object of this invention to provide improved apparatus for heating or cooling a defined region of the human or animal body in which the above disadvantages are to a significant extent overcome. - -

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Accordingly, the present invention consists in apparatus for^* . heating or cooling a defined region of the human or animal body, comprising at least one Peltier effect thermo-electric element having first and second element surfaces; current supply means for supplying- a controlled current to said element; heat,sink means in thermal contact with said first element surface and means for establishing thermal contact between said second element surface and the body region.

Preferably, said second element surface is adapted for contact with the body region substantially directly.

Alternatively, heat exchanger means is provided to establish heat exchange between said second element surface and the body region.

This invention will now be described by way of example with reference to the accompanying drawings in which:-

FIGURE 1 is a diagrammatic representation of one apparatus according to this invention;

FIGURE 2 is a circuit diagram showing power and control circuitry for use with the apparatus shown in Figure 1,

FIGURE 3 s a diagram illustrating apparatus according to a further embodiment of this invention,

FIGURE 4 is a sectional view illustrating an alternative component for use in apparatus according to this invention,

FIGURE 5 is a somewhat diagrammatical section through apparatus according to a further embodiment of this invention, and

FIGURE 6 is a circuit diagram illustrating circuitry for use in the apparatus of FIGURE 5.

This invention utilises the Peltier thermo-electric effect whereby the flow of current through, for example, a bismuth telluride element can produce a relatively large temperature differential between hot and cold junction surfaces. The effect is reversible in that a flow of current in the opposite sense will reverse the direction of the temperature differential. Referring now to Figure 1, a planar array of Peltier effect elements 10 is arranged on the flat upper surface of a heat sink block 12. The Peltier elements are connected in known manner to receive DC through leads 1 and 16. The upper surfaces of the Peltier elements 10 are covered by a thin thermal contact plate 1 . The underside of the heat exchanger block 12 is cross-cut to produce a "pin-fin" array 18, to improve thermal transfer.

The described assembly is mounted within a plastics housing shown schematically at 20. This housing is connected through a conduit 22 with an external power supply unit, the conduit 22 providing not only electric cabling but also a cooling air feed. Within the housing 20 there is additionally mounted an auxiliary cooling fan 24, the function of which will be described hereinafter.

Referring now to Figure 2, a variable voltage is provided in generally conventional manner by means of a mains control 30. ~ transformer 32 and bridge rectifier circuit 34. Th mains control 30 receives a control input through switching relay 36 and temperature comparators 38 and 40 which receive in turn an input 42 from a temperature measuring circuit, (not shown)

A polarity relay 44 is provided to enable reversal of the DC applied from the bridge rectifier 3^ to terminals 14 and 16. This polarity relay, as well as the switching relay 36. ^are controlled by a timer 46 governed by a master timer 48.

In use of the described apparatus, the operator will pre-set hot and cold temperatures in comparators 38 and 40 and will enter parameters such as switching rate and length of dwell at each temperature in the timer 46. To take the example in which it is desired to subject the palm of the patient's hand to controlled cooling, the palm of the hand is placed upon the thermal contact plate 17 and the polarity relay operated so as to produce cooling at the upper surfaces (as shown in Figure 1) of the Peltier effect elements. Since human tissue has a relatively high heat capacity, it is necessary to remove relatively large amounts of heat if a significant temperature drop is to be achieved. Peltier effect elements are capable of establishing relatively high temperature differentials but ~ . require relatively high current flow. To dissipate the heat transferred -from the patient's hand and also the Joule heating in the Peltier element, an efficient heat exchanger is required and it is for this reason that the heat exchanger block is specially shaped. In this mode of operation, maximum airflow will be required and the cooling airflow through conduit 22 will be supplemented through use of. the auxiliary fan 24. In this way, cross flow turbulence is established and boundary layers are largely eliminated.

If it is desired to effect heating of the patient's hand, whether as part of a thermal cycling procedure or in a separate therapeutic or diagnostic technique, a reverse current flow will be applied to the Peltier elements. In this mode, it is clearly important that the upper surfaces of the Peltier elements should not become unbearably hot. With the Peltier elements operating as a heat pump it will be recognised that the heat exchanger block 12 operates as a heat source. With the mentioned practical restriction on temperature, a reduced airflow is desirable so that the auxiliary fan 24 may be dispensed with.

In a number of applications, it will not be convenient to bring the surface of the Peltier elements into direct (or substantially direct) contact with the body region to be treated. There is illustrated in Figure 3 an alternative embodiment for use in such circumstances.

As shown in Figure 3» two separate circuits are established with an appropriate heat exchanger fluid flow in each circuit. In one example that fluid would be a 70:30 mixture of ethyl glycol and water to which an appropriate bacteriacide and fungicide have been added. Alternative fluids would be glycerol or distilled water. The first, therapy circuit 50 comprises a hollow block 52 carrying a planar array of Peltier elements on both of two opposing faces. Under the action of a pump 6, fluid passes through the block 52 and is, in the manner described above, heated or cooled by the Peltier elements. A thermal contact pad 58 includes a coil 60 which is connected by means of a flexible coupling 62 so as to receive the circulating fluid. The flexible coupling 62 will be of an appropriate length to enable the contact pad 8 to be disposed upon the body region. The therapy circuit 0 is completed by a temperature sensor 64 providing a control output on terminal 66.

A second, radiator circuit 70 comprises two heat exchange blocks 72 arranged one each side of the block 52 such that each array of Peltier elements 5 contacts, on one face, the block 52 and, on the opposite face one of the heat exchange blocks 7 . Under the action of a pump 7 , a circulating flow is established through the heat exchange blocks 7 in series. In known manner, each heat exchange block 72 is provided with internal baffles or other elements providing for a serpentine fluid path, to improve the heat transfer. The radiator circuit 70 is completed by a coil 7 through which air may be blown from blower 78.

In a modification, it is possible to replace the circulating fluid in either or both of the therapy circuit 50 and radiator circuit 70 with a suitably connected heat pipe. Thus, referring to Figure 4, a planar array of Peltier elements 100 is sandwiched between a mounting surface 102, provided at one end of a heat pipe 104, and a mounting surface 106 of a heat exchange block 108. The heat pipe 104 is provided at its opposite end with a series of radiator fins 109- The block 108 is, as in the previous embodiment, connected for the passage of heat fluid in a circuit which includes a pump, a thermal contact pad and a temperature sensor.

The power and control circuitry shown in Figure 2 can be used with either of the embodiments shown in Figures 3 and 4.

It will be recognised that a wide variety of alternative arrangements exist in which one surface of a Peltier element (or array of elements) can be established in thermal contact with the human body region of interest, with an opposing surface of the Peltier element being established in thermal contact with appropriate heat sink means.

An alternative application for apparatus according to the present invention is a device for measuring the sensitivity of human skin regions to temperature. Referring now to Figure 5. there is illustrated such apparatus styled externally in the form of a gun. The - device shown generally at 200 has a thermally conducting tip 202 providing a mounting for a Peltier element 204. Thus, one face of the ^'. Peltier element 204 is established -in thermal contact with the tip 202 whilst the opposing surface of the "Peltier element, is 'exposed, for "^: contact with the skin. Appropriate electrical insulation is provided for the Peltier element 204 and electrical contact is established through leads 206 with control circuitry 208, to be described later in more detail. A heat pipe 210 extends from the tip 202 to a fin array 212 serving as a heat sink. The fin array communicates with the exterior of the device and a blower unit 214 is provided to enable air to be blown through the fin array.

The device includes a bank of rechargeable Ni-Cd battery cells connected with the circuitry 208 via an on-off switch 218 and a polarity reversing switch 220. The device also includes a temperature display 220.

Referring now to Figure 6, a power supply unit 250 is provided which is of generally conventional form and which is connected with the battery cells. The output of the power supply unit 250 is connected with leads 206 via a relay 25 controlled by a timer 254. The leads 206 are also connected with the input of a voltage to temperature converter 256 which provides a display drive for the temperature display means. The relay 22 operates to connect the leads 206 (and thus the Peltier element 204) to the power supply 20 for a heating cycle and, alternately, to the converter 256 in a measurement cycle. The heating cycle may comprise 30% to 10/». In the measurement cycle, use is made of the fact that the Peltier element has a thermo-voltaic effect, generating a voltage which is indicative of the instaneous temperature of the element.

It should be understood that this invention has been described by way of examples only and a variety of modifications are possible without departing from the scope of the invention. There are believed to be a wide variety of applications beyond the examples referred to, of apparatus for heating or cooling a body region. Whilst references have been made to human body regions, it is believed that the invention will also have vetinary applications.

Claims

1. Apparatus for heating or cooling a defined region of the human or animal body, comprising at least one Peltier effect thermo-electric element having first and second element surfaces; current supply means for supplying a controlled current to said element; heat sink means in thermal contact with said first element surface and means for establishing thermal contact between said second element surface and the body region.

2. Apparatus according to claim 1 in which said second element surface is adapted for substantially direct contact with the body region.

3- Apparatus according to claim 1 wherein heat exchanger means is provided to establish heat exchange between said second element surface and the body region.

4. Apparatus according to claim 3 wherein said heat exchanger means comprises a heat fluid flow path.

5. Apparatus according to claim 4 wherein said heat exchanger means includes a thermal contact pad for establishing thermal contact with the body region.

6. Apparatus according to claim 1 wherein said heat sink means comprises an air cooled fin array.

7. Apparatus according to claim 6 wherein said heat sink means comprises means for establishing a forced air current through said fin array.

8. Apparatus according to claim 1 wherein thermal contact between said heat sink means and said first element surface is established through a heat pipe.

9. Apparatus according to claim 1, further comprising control means enabling the pre-selection of temperatures for heating or cooling.

10. Apparatus according to claim 1, comprising voltage measuring means connectable with said element alternately with said current supply means to measure a thermo-voltaic effect of said element and thereby provide an indication of temperature.