WO2006091106A1

WO2006091106A1 - Clinical ear thermometer

Info

Publication number: WO2006091106A1
Application number: PCT/NO2006/000070
Authority: WO
Inventors: Randi Eidsmo Reinertsen; Jarl Reitan; Ingunn Marie Holmen Geving; Odd Kristen Østern PETTERSEN; Alain Ferber; Kristine HOLBØ
Original assignee: Sinvent As
Priority date: 2005-02-22
Filing date: 2006-02-21
Publication date: 2006-08-31
Also published as: NO20050940L; NO20050940D0

Abstract

The essential part of a new clinical thermometer for measuring temperature in a person's ear, is an ear plug (15) made of a compliant and skin-friendly material, e.g. silicon. The ear plug is shape-adapted to the concha (3, 8) and auditory canal (4) of the person, and the ear plug has thermal radiation detector equipment embedded therein. A pickup element (14, 24) for directing infrared radiation from the ear drum (10) toward a receiver element (19), is arranged at an inner end (18) of the ear plug (15), and the inner part (15a) of the ear plug has a shape and a length to ensure that its inner end (18) is located, in use, at a position between the ear drum (10) and the inner bend (2) of the auditory canal (4).

Description

CLINICAL EAR THERMOMETER

Introduction The present invention relates to a clinical thermometer for measuring temperature in a person's ear.

Background

Many diseases are accompanied by fever, i.e. a raise in body temperature. Several diseases have characteristic courses regarding changes in body temperature (for instance pneumonia). A measurement of body temperature is the remedy used most often for making a diagnosis. In order to have as good a basis as possible for making the diagnosis, the body temperature must be measured in a place that it provides the best possible measure of the thermal condition of the body.

Body temperatures vary according to where they are measured: provided that the ambient temperature is lower than about 28-34 ⁰C, the temperature in the central parts of the body will be higher than in peripheral areas. Nor is the temperature the same in all peripheral areas; the temperature of hands and feet are usually lower than chest and stomach temperatures. The temperature varies also in central body parts: in the oral cavity the temperature is lower than in the aesophagus and the rectum. The heat content, and hence the temperature, will also vary in dependence of e.g. physical activity: activity that entails use of thigh muscles, results in increased heat production in the active muscles, which leads to increased temperature in the thigh, in veinous blood from the thigh, and in the areas where the veinous and warm blood is transported on its way to the heart (for instance the rectal area that is often used for temperature measurement). The temperature is a measure of the heat content of the body. The heat content is regulated by means of a neural network that transfers signals from temperature sensors in the whole body, to the temperature control centre in the brain (hypothalamus) where information from all temperature receptors is integrated. As a result of the integration, signals are transferred to effector organs with the ability to start mechanisms that either increase the heat content of the body (for instance increased heat production through shivering, physical activity or behaviour to decrease heat loss) or increases heat dissipation (for example use of heat to evaporate perspiration, or behaviour that will increase heat loss). Not every part of the body is equally sensitive to temperature changes: the most sensitive places are the hypothalamus and the core area from hypothalamus and comprising the lungs and the heart. A rather small temperature change in these areas will bring about a rapid response and start of effector mechanisms that will bring the temperature back to its normal value.

In most humans, the normal body temperature is 37 ⁰C (range 36-37). An optimum function of the chemical and physical processes going on in the body, is quite dependent on maintaining the core temperature of the body at 37 ⁰C, without variation. However, it is not possible to measure temperature in the pulmonal artery. Nor would this be a method of practical use for routine temperature measurements.

In routine temperature measurements, rectal and oral measurements are the traditional methods in the medical community, while arm pit measurements have been used extensively on a non-professional basis.

During later years, a technology for making measurements in the auditory canal, has been developed. The basis for this method is that temperature measured on the ear drum has been documented to be in very good correspondence with temperature measured in the pulmonal artery. This is because the ear drum has its blood supply from a branch of the carotis artery that leads blood from the heart to the hypothalamus. Therefore, the ear drum temperature provides a good measure of the thermal condition of the body.

However, ear thermometers available in the market today, partly measure temperature in the auditory canal, and partly on the ear drum. It is a large problem that one cannot know if or when a measurement is actually made from the ear drum, and hence it is not possible to verify that the measured temperature is actually the ear drum temperature. The measurement is based on infrared radiation, and the receiving part of the thermometer must "see" the ear drum in order to make a correct measurement. When existing ear thermometers are used, it is not possible to know if this condition is fulfilled.

The reason that existing thermometers cannot always see the ear drum, is that there are large variations from person to person regarding the actual shape of the auditory canal. Many persons have an auditory canal with a shape that constitutes a hindrance for entering the thermometer to a position where the pickup element or lens can see the ear drum. Prior publications

US patent No. 5,333,622 discloses a custom-moulded ear plug that may incorporate temperature sensing elements, so as to provide an ear thermometer. The ear plug of the patent is formed in situ, by positioning a foaming material within the ear canal. Forming action is triggered by heat, humidity or water or chemical products, and an electronic device like a temperature sensing element may be embedded therein. The ear plug will consist of one part adapted to the concha and one part extending further into the auditory canal and adapted to the shape of the canal. For instance a thermocouple may be embedded in the ear plug, for allegedly making highly accurate readings of the "core temperature".

However, US 5,333,622 states clearly that it is important that the foam does not reach the ear drum. To that end, an "ear dam" may be optionally inserted ahead of the foam to ensure that the foam does not penetrate too deeply, or a protective flange is inserted so as to limit the forward expansion of the foam. Consequently, this ear plug thermometer will experience just the same problem as mentioned above, because no provision has been made to ensure that the pickup element for infrared radiation actually will see the ear drum.

Summary of the invention

It is therefore an object of the present invention to provide a clinical thermometer for ear measurement that will ensure that measurements will actually be ear drum temperature measurements.

It is another object of the present invention to provide a clinical thermometer that will easily and rapidly present correct measurements of body core temperature.

Further, it is an object of the present invention to provide a clinical thermometer that is comfortable in use.

Further, it is an object of the present invention to provide a clinical thermometer that can be used as well by medical personnel as by the person whose temperature shall be measured.

Additionally, it is an object of the present invention to provide a clinical thermometer that will ensure measurement in the same position every time it is used by the same person. In accordance with the present invention, there is provided a clinical thermometer for measuring temperature in a person's ear, which thermometer comprises an ear plug made of a compliant and skin-friendly material, e.g. silicone, which ear plug is shape-adapted to the concha and auditory canal of the person by means of an adapted concha part and an adapted auditory canal part. The ear plug has a thermal radiation detection equipment embedded in the auditory canal part, and the detection equipment is connected to a measurement circuit. The thermometer is characterized in that the detection equipment comprises an infrared radiation pickup element for directing infrared radiation to a receiver element, and the pickup element is arranged at an inner end of the auditory canal part so as to face the person's ear drum, and in that the auditory canal part has a shape and a length to ensure that its inner end is located, in use, at a position between the ear drum and the inner bend of the auditory canal.

The receiver element may be a detector element connected to provide an electrical signal to the measurement circuit. The pickup element may then be an optical lens, and the detector element may be a thermocouple with a junction placed one focal distance away from the optical lens.

Alternatively, the pickup element may be an inner end of an optical fibre that has an outer end arranged outside the earplug adjacent a detector element for receiving the infrared radiation via the optical fibre. In this case, the optical fibre outer end and the detector element may be arranged just at an outer surface of the earplug, or they may be located in a measuring apparatus at some distance from the ear or possibly mounted behind the ear, the optical fibre then being substantially longer than the length of the auditory canal.

In one embodiment of the invention, the detector element and the measurement circuit are operative to select one hottest segment in the total field of view of the pickup element, as a representative segment for measurement.

In another embodiment, the pickup element is constituted by a mosaic of Fresnel microlenses based on silicon or moulded glass material.

The pickup element may even be one single Fresnel microlens based on silicon or moulded glass material. Alternatively, the pickup element may be a collecting lens made of any of the materials moulded glass, silicon, germanium and zinc selenide.

The detector element may be a thermopile, combined with a stable reference thermistor in the measurement circuit.

In a further embodiment of the invention, an optical alignment fibre is arranged in a steady relation to the pickup element for making optical reflection measurements to ensure aligning of the pickup element toward the ear drum.

The ear plug may be a plug made individually by moulding from the ear of the person in question.

Alternatively, the ear plug may belong to a set of differently shaped ear plugs, and has been selected in accordance with a best fit for the person in question.

Preferably, the ear plug is made of materials that withstand a sterilizing process.

Brief description of the drawings

In the following, a detailed description will be given of various embodiments and aspects of the present invention, to provide a better understanding of the invention, and at the same time it will be referred to the appended drawings, of which:

Fig. 1 is a drawing showing a human ear, highlighting the anatomical details of interest in connection with the present invention,

Fig. 2 shows an ear plug constituting part of a thermometer in accordance with an embodiment of the present invention, inserted in the auditory canal, for explanation of the principle of the invention,

Figs. 3a, b, c show alternative shapes of ear plugs constituting part of thermometers in accordance with the invention,

Fig. 4 shows an example of a receiver housing to be embedded in an ear plug, in accordance with an embodiment of the invention, Figs 5, 6 and 7 show various embodiments of the invention based on the use of fibre optics, and

Fig. 8 shows a detector housing for a fibre optics embodiment of the present invention.

Detailed description of the preferred embodiments of the invention

Referring now to Fig. 1 , this is a drawing to explain an anatomical detail of the human ear, in the context necessary to explain the present invention. It appears that among the "outer parts" of the ear, the Concha Auriculae or ear concha, or rather the Cavum Concha 3 is the "cave" that surrounds the opening into the auditory canal (Meatus Custicus) 4. Below the Cavum Concha 3 we find the Antitragus 5 and Tragus 6 constituting lower and front delimitations of the Cavum 3, and above we find the Cms 7 of the Helix and the Cymba Concha 8. The Antihelix 9 constitutes a rear limitation of the Cavum 3.

Turning to "inner parts", it is first noted that the auditory canal 4 leads to the ear drum (Membrana Tympani) 10. At the outer part of the auditory canal 4, there is, at bridge between a cartilage part 11 and a bone part 12, a bend 1 that should be noted, and at the inner part of the auditory canal another bone part 13 provides a second bend 2, rather near the ear drum 10.

In principle, and referring to fig. 2, the thermometer of the present invention relies on detection of infrared radiation from the ear drum 10 by means of a front pickup element 14 that shall be located, in use, at a position that lies between the above mentioned second bend 2 of the auditory canal, and the ear drum 10. This pickup element 14 constitutes an element for focusing infrared radiation from the ear drum 10 toward a receiver element (not shown in fig. 2) embedded in a specially molded ear plug 15 that also carries the pickup element 14.

In the embodiment shown in fig. 2, the pickup element 14 is arranged in a receiver housing 16 that appears in closer detail in fig. 4, see below. Signal lines 17 carry optical or electrical signals out through the ear plug 15 to external equipment.

In the principle sketch in fig. 2, actually only the inner part of the ear plug 15 appears. It would seem clear that an ear plug such as indicated in this sketch, would be rather difficult to remove, once inserted. Therefore, a complete ear plug for use as part of the thermometer of the present invention must also include an outer part that can be 2006/000070

gripped readily for insertion and removal, and this outer part must be adapted to the above described outer parts of the ear. In the appended figs. 3a, 3b and 3c appear three individually molded ear plugs, in order to show the individual variations exhibited by human ears. Reference numeral 15a designates an inner part of the ear plug, i.e. an auditory canal part, and reference numeral 15b designates an outer part, i.e. a concha part. A dotted line 19 indicates an imaginary dividing interface between the two parts 15a and 15b, but the ear plug will preferably be molded as one piece without any material division. Reference numeral 18 designates the inner end of the auditory canal part 15 a.

In one embodiment of the invention, such ear plugs as shown in figs. 3a, b, c are molded individually for one person, i.e. after having made a cast of the ear in question. In another embodiment, a set of ear plugs 15 is molded so as to provide, by selection from the set, a best-fitting ear plug for a person. Such a set will be manufactured comprising a number of, and with a variety in, ear shapes so as to cover a large range of variations in shape among human ears.

Fig. 4 shows in more detail such a receiver housing 16 as appears in fig. 2. The housing 16 is shown to be located rather near the ear drum 10, as intended. The housing 16 is embedded in an inner ear plug part 15a as described above.

In the embodiment shown here, the pickup element is an optical lens 14 arranged at the inner end 18 of the ear plug part 15a. The optical lens 14 is intended to transmit and focus infrared radiation from the ear drum, and is made of a material with good transmission characteristics in the 7-14 μm wavelength range, for instance silicon, germanium or zinc selenide. Other materials with similar characteristics can be used also, like for instance moulded infrared transmitting glass.

The optical lens 14 may alternatively be a so-called Fresnel lens, or a mosaic of Fresnel microlenses for focusing the IR radiation coming from the ear drum. The Fresnel lens/microlenses are based preferably on moulded glass material, or possibly silicon material.

The lens 14 focuses IR radiation toward a receiver element that is, in the embodiment shown in fig. 4, a detector element 19 that converts received IR radiation into an electrical signal to be carried by signal lines 17 from the receiver housing 16 to a measurement circuit located either elsewhere in or on the ear plug, or externally. Inside the receiver housing 16, an insulation tube 20 of e.g. glass material provides insulation between the electrical wires. Another wire pair 21 is provided from a thermocouple or a thermistor 30 monitoring the temperature of the receiver housing 16, to the measurement circuit.

As regards the detector element 19, this may be constituted by a thermocouple having a junction placed just at the lens focus area, or preferably a thermopile placed in the same location. A preamplifier may even be embedded together with the detector. If a thermopile is used as a detector element, the thermocouple 30 for temperature monitoring may be mounted on or below the thermopile frame.

Comparing fig. 4 to fig. 2, it seems evident that the signal lines 17 pass out through the ear plug 15 and to a measuring circuit located externally (actually, out through a complete ear plug 15 such as shown in figs. 3a, b, c with an outer ear plug part 15b). However, it is possible to have such a measuring circuit (including battery) mounted in or on the outside face of the ear plug 15, and even with a display for reading the temperature, either directly by an operator, or as a storage value by the person himself after removal of the ear plug when a measurement has been made. In such a case, the outer part of the ear plug is prepared for such equipment in or after the molding process. With the electronic micro technology of today, it is even possible to add a short-range radio transmitter to the measuring circuit, and have a two-part thermometer that includes a hand-held radio receiver with a temperature display, in addition to the ear plug.

Another embodiment of the invention appears in fig. 5, namely a fibre-optics embodiment. Also in this figure a simplified ear plug 15 is shown inserted in the auditory canal. It must be kept in mind that the outer part (Concha part) 15b will be more prominent that what appears in this drawing.

An optical fibre 22 has an inner end that is centered in a front part 23 of the auditory canal part 15a of the ear plug. Innermost, a micro-lens 24 may be used to focuse the infrared radiation into the optical fibre 22. The micro-lens 24 may be simply a hemispherical fibre end, but other types of lenses can be used also. However, the most preferable solution is to use simply a flush fibre end 24 without a lens. This is possible because of the close relation to the ear drum 10.

It is noted here, that a configuration such as shown in figs. 2 and 4 is also possible in a fibre optics version, simply by replacing detector 19 and signal lines 17 by an optical fibre having an inner end located where the detector 19 was placed. In fig. 5 the optical fibre 22 is shown to pass out of the ear plug 15 and further to a (not shown) external detector element and measurement circuit, apparently placed behind the person's ear. In such an embodiment, the optical fibre 22 must be well insulated thermally, to protect it from ambient temperature influence.

In fig. 6, a similar solution appears as in fig. 5, however a detector element 19 has been placed at the outside surface of the ear plug 15. Preamplifier and signal conditioning circuitry is embedded in the detector (thermopile) housing 19. Signal lines 17 are indicated from the detector 19 to an external measurement circuit 25.

A thermistor must be embedded with the detector thermopile, in order to measure the temperature of the housing and the fibre itself. Further, the fibre must be thermally connected to the frame of the thermopile. If not, then both the thermopile frame temperature and the fibre temperature must be monitored separately.

In fig. 7, a compact solution is shown where also a measurement circuit 25 and a display unit 26, or possibly a radio transmitter 27, has been added, using micro electronic circuitry as mentioned above.

With reference to fig. 5, where an optical fibre 22 leads to an external detector 19, or for that matter figs. 6 and 7 where a shorter fibre leads to an ear plug-mounted detector 19, fig. 8 shows how the outer end of the optical fibre 22 is mounted relative to the detector. A rigid housing 29 holds a ferrule 28 that accommodates the fibre end at a well defined distance from the detector. Preferably, a 0,5 mm diameter fibre is used, having a numerical aperture in the range +/- 30 °. With a detector of area 1 ,2 x 1 ,2 mm², the distance between fibre end and detector is preferably about 0,5 mm. (It should be noted that the relative dimensions may be a little misleading in fig. 8. The fibre diameter should actually be approximately the same as the distance fibre-detector, and the detector diameter should be a little larger than twice the fibre diameter, to ensure that the detector picks up all radiation from the fibre.)

In one embodiment of the present invention, an adjustment option is included, wherein the detector element and the measurement circuit are operative to select that segment of the total field of view of the pickup element, which is the hottest one, as a representative segment for measurement. This can be done by arranging an array of detector segments, e.g. 4 segments, and having the measurement circuit select the one that gives the highest reading. In another embodiment, and in order to ensure alignment of the lens pickup element toward the ear drum, an additional optical fibre is arranged in a steady relation to the lens for making optical reflection measurements. This means that a special fibre is arranged next to the lens for shining light toward the ear drum and to receive reflected light therefrom. The reflection of light depends on the tissue and the blood flux therein, and the reflection from the ear drum is quite different from the reflection from other tissues in the auditory canal. Hence, if the reflection is not proper, one may adjust the position of the ear plug somewhat, manually, to obtain a proper reflection reading. This fibre should then conduct visible or near-infrared light.

As regards the aspect of preparing the ear plugs which are an important part of the present invention, the following procedure is followed to make such an individual ear plug:

First, liquid hot wax is poured into the ear of the person. "Hot wax" can be prepared at a temperature that is at about 40 ⁰C, so this temperature will not feel uncomfortable. The auditory canal and the concha will be filled by such wax. The wax will solidify when the temperature drops, at about 30-33 ⁰C, and a wax pre-form can then be pulled carefully out so that the shape of the pre-form is maintained.

This pre-form is used as a basis for a further casting process with "negatives" and "positives", and the process finishes with for instance a silicon ear plug with a perfect match to the person's ear.

However, the inner part of the plug shall not touch the ear drum of the person, so the plug is cut at a suitable position between the inner end (ear drum position) and the inner bend 2 of the auditory canal (apparent from the ear plug itself).

Thereafter, holes and openings are drilled/machined to insert the necessary equipment (lens, detector, wires, optical fibres, microelectronic circuitry).

In order to prepare a set of "general ear plugs" such as mentioned earlier, experiences from a high number of persons (at least 100) of various head/ear shapes are used to select, or even to manufacture specially, for instance 10 ear plugs as representative for 10 "ear types" that will generally cover all human ears. (The number 10 is by no means limitative. Such an ear plug set may comprise any reasonable number of ear plugs, from 3 to 50.)

Claims

1. A clinical thermometer for measuring temperature in a person's ear, said thermometer comprising an ear plug (15) made of a compliant and skin-friendly material, e.g. silicone, and shape-adapted to the concha (3, 8) and auditory canal (4) of the person by means of an adapted concha part (15b) and an adapted auditory canal part (15a), said ear plug (15) having thermal radiation detection equipment embedded in said auditory canal part (15a), said detection equipment being connected to a measurement circuit (25), characterized in that

- said detection equipment comprises an infrared radiation pickup element (14, 24) for directing infrared radiation to a receiver element (19), said pickup element (14, 24) being arranged at an inner end (18) of said auditory canal part (15a) so as to face the person's ear drum (10), and that

- said auditory canal part (15a) has a shape and a length to ensure that its inner end (18) is located, in use, at a position between the ear drum (10) and the inner bend (2) of the auditory canal (4).

2. The clinical thermometer of claim 1 , characterized in that said receiver element is a detector element (19) connected to provide an electrical signal to said measurement circuit (25).

3. The clinical thermometer of claim 2, characterized in that said pickup element is an optical lens (14), and said detector element (19) is a thermocouple with a junction placed one focal distance away from said optical lens (14).

4. The clinical thermometer of claim 1 , characterized in that said pickup element is the inner end (24) of an optical fibre (22) that has an outer end arranged outside said earplug (15) adjacent a detector element (19) for receiving said infrared radiation via the optical fibre (22).

5. The clinical thermometer of claim 4, characterized in that the optical fibre outer end and said detector element (19) are arranged just at an outer surface of said earplug (15).

6. The clinical thermometer of claim 4, characterized in that the optical fibre outer end and said detector element are located in a measuring apparatus at some distance from the ear or possibly mounted behind the ear, said optical fibre (22) being substantially longer than the length of the auditory canal.

7. The clinical thermometer of claim 2 or 4, characterized in that said detector element (19) and measurement circuit (25) are operative to select one hottest segment in the total field of view of the pickup element, as a representative segment for measurement.

8. The clinical thermometer of claim 1 , characterized in that said pickup element (14) is constituted by a mosaic of Fresnel microlenses based on silicon or moulded glass material.

9. The clinical thermometer of claim 1 , characterized in that said pickup element (14) is a Fresnel microlens based on silicon or moulded glass material.

10. The clinical thermometer of claim 1 , characterized in that said pickup element is a collecting lens (14) made of any of the materials moulded glass, silicon, germanium and zinc selenide.

11. The clinical thermometer of claim 2 or 4, characterized in that said detector element (19) is a thermopile, combined with a stable reference thermistor in the measurement circuit (15).

12. The clinical thermometer of claim 1 , characterized in that an optical alignment fibre is arranged in a steady relation to said pickup element for making optical reflection measurements to ensure aligning of said pickup element toward the ear drum.

13. The clinical thermometer of claim 1 , characterized in that said ear plug (15) is a plug made individually by moulding from the ear of the person in question.

14. The clinical thermometer of claim 1 , characterized in that said ear plug (15) belongs to a set of differently shaped ear plugs, and has been selected in accordance with a best fit for the person in question.

15. The clinical thermometer of claim 1 , characterized in that said ear plug (15) is made of materials that withstand a sterilizing process.