WO2004027363A1

WO2004027363A1 - Temperature telemeter

Info

Publication number: WO2004027363A1
Application number: PCT/SG2003/000225
Authority: WO
Inventors: Chin Leong Lim
Original assignee: Dso National Laboratories
Priority date: 2002-09-20
Filing date: 2003-09-19
Publication date: 2004-04-01
Also published as: SG108873A1; AU2003273201A1

Abstract

A temperature telemetric sender and a temperature telemeter (50) using one or more of the senders with a single or common receiver (64) are provided. The temperature telemetric sender includes a sensor (52) to measure a temperature of a body cavity, preferably an ear canal, of a subject. A transmitter (60) coupled to the sensor is responsive to the sensor and transmits a signal indicative of the temperature of the body cavity. The receiver (64) receives the signal wirelessly from the transmitter. The temperature values received by the receiver may be compensated for changes in ambient temperature, measured at the sender or receiver, and may be converted into an estimation of a core body temperature. The temperatures may be displayed, preferably as a series of temperatures displayed graphically. An alarm (66) may be provided when the received signal, or a temperature value derived from it, is indicative of a temperature equaling a predetermined temperature or falling outside a predetermined temperature range. Intermediate transceivers, which relay temperature signals from respective senders to the common receiver, may be used to extend the operational range.

Description

TEMPERATURE TELEMETER

Background of the Invention

1. Field of the Invention

The present invention relates generally to the measurement of body temperature.

More particularly, the present invention relates to a system and method for measuring temperature from a body cavity and wirelessly transmitting the temperature reading to a receiver for monitoring.

2. Description of the Related Art

The measuring and monitoring of a person's core temperature (T_c), also known as deep body temperature, is important for a variety of health and safety reasons. This is because a person's T_c must be maintained within a very narrow range for the body to function normally. Any excursion outside of this prescribed range can result in a number of temperature-related disorders and other physiological problems.

At elevated core temperatures, a person can develop disorders such as heat stroke and other symptoms such as exhaustion, cramps, rashes, and fatigue that may develop as a result of overheating. An abnormally high T_c may even result in death. Persons engaged in activities involving high ambient temperatures, radiant heat sources, high humidity, direct physical contact with hot objects, or strenuous physical activities are highly susceptible to heat disorders. Such risks are inherent in many industries and professions, including fire fighting, athletics, active military combat positions, and construction work. This is particularly true for workers that are required to wear semi- permeable or impermeable protective clothing.

At the other end of the spectrum, if T_c is too low, hypothermia may occur. A person may develop hypothermia when T_c falls below 35°C. In addition, hypothermia is frequently fatal when T_c falls below 32°C. Infants, neonates and elderly persons are generally susceptible to hypothermia. Elderly persons usually have a more limited ability to detect cold while infants and neonates are prone to becoming hypothermic because of their lack of subcutaneous fat. In addition, mountain climbers, skiers, and other travelers to areas having chilly climates are also susceptible to hypothermia.

In many instances, temperature related disorders might be easily prevented by early detection of temperature excursions out of the acceptable range and administration of the appropriate preventive measures and treatments. After detection, prompt treatment will usually lead to a rapid and complete recovery. Therefore, it is best if persons at risk of developing temperature-related disorders, such as those involved in strenuous physical activity, have their core temperatures monitored.

For example, temperature monitoring is common in hospitals. During surgery, a patient's T_c is monitored and maintained at around 36°C to prevent the onset of mild hypothermia (except in cases of induced hypothermia). Another example of the use of temperature monitoring in hospitals is in an Intensive Care Unit (ICU). Because patients warded in an ICU are usually in serious condition, therefore in most cases, they must have their core temperatures monitored.

Because of the extensive applicability of core temperature measurements, a number of core temperature measuring devices have been developed. In hospitals, a patient's core temperature is usually monitored via a temperature probe inserted into a body cavity of the patient, such as the mouth, the axilla or the rectum. The temperature probe can also be inserted through the patient's nose, down to the esophagus. Unfortunately, the insertion of a temperature probe into a patient's rectum or esophagus usually causes significant discomfort to the patient. Hence, a less invasive core temperature measuring device is highly preferred.

An example of a core temperature measuring device is an ingestible transmitter disclosed in U.S. Patent No. 4,844,076 issued to Lesho et al. The ingestible transmitter is encapsulated in a pill and swallowed by a subject or patient. To ensure that the transmitter is in the proper location when T_c readings are taken, the subject must swallow the transmitter at least an hour before the temperature is measured.

To avoid interference between multiple transmitters, only one transmitter can be ingested at any one time. Therefore, the subject has to wait for the egression of the first transmitter before swallowing a second. This limits the flexibility of the use of such core temperature measuring devices because there is a time lag after ingestion of the transmitter before the core temperature measurements can be taken and utilized. Secondly, temperature measurements cannot be monitored for lengthy periods of time because the transmitter will not always be in the right position and will eventually be egressed. As such, the use of such core temperature measuring devices must be planned beforehand and timed accordingly.

Additionally, the temperature of foods and liquids consumed by the' subject as well as fluids generated by the body may influence the core temperature measurements obtained through the use of such transmitters. Hence, the accuracy and consistency ofthe readings taken may vary. A further drawback ofthe Lesho transmitter is that it cannot be reused due to hygienic considerations. Therefore, the use of such ingestible transmitters can be rather costly since each transmitter is only operable for a limited period of time.

Other prior art devices which transmit temperature information from internal body locations are described in the following patent documents.

European Patent Application EP 476,730 describes a system for ovulation detection and prediction using an embedded temperature sensor which emits temperature information.

United States Patent US 4,515,167 and United Kingdom Patent Application GB 2,285,134 describe intra- vaginal temperature sensing and transmitting devices.

United States Patent US 4,676,254 describes an intrauterine device for monitoring ovulation by taken and storing a succession of temperature readings which are subsequently downloaded to an external device.

United States Patent US 5,033,864 describes a baby pacifier which is used intra- orally to detect temperature and transmit a signal to an external device if the detected temperature is outside a predetermined range.

These prior art devices are not ingested and are not used invasively in the usual medical sense of surgical invasion, i.e. involving puncture or incision of the skin. However, the positioning of these or other measurement devices to measure vaginal, uterine, rectal or oral temperatures is intrusive, i.e. is invasive of the subject's privacy; and/or causes a degree of discomfort during insertion, use and/or retrieval; and/or is obstructive ofthe subject's normal functions and movements.

Core temperature measuring devices, such as ear temperature monitor 10 illustrated in Figure 1, are also commonly employed. Ear temperature monitor 10 comprises a monitor 12 coupled to an earpiece 14 via a flexible wire 16. Earpiece 14 further comprises a thermistor 18 encased in a foam earplug 20, and a speaker 22. Foam earplug 20 is first inserted into the ear canal of a subject. Thermistor 18 then measures the temperature within the ear canal. The measured temperature reading is sent through flexible wire 16 to monitor 12, where the temperature reading is stored and displayed on a screen 24. When a pre-set temperature threshold is reached, speaker 22 may be configured to sound a warning signal.

One limitation of this core temperature measuring device is that only the subject of ear temperature monitor 10 may conveniently monitor his own T_c. In the event of an emergency, for instance an acute case of hypothermia, devices such as ear temperature monitor 10 are unable to warn others of the subject's predicament. Even in less urgent circumstances, ear temperature monitor 10 is not well suited to provide the T_c of the subject to another monitoring entity.

Another problem with conventional core temperature measuring devices, such as ear temperature monitor 10, is that they are wired systems using thermistors or thermocouples. It is inconvenient and cumbersome to have a wire hanging out of a subject's ear, which is further connected to a monitor of considerable size. The wires may interfere with or hamper the mobility of the subject, while the monitor is an undesirable burden. This is particularly true when it is desirable to monitor the temperature of an active subject, such as a soldier or a construction worker. In such cases, the wires would become an occupational hazard.

In view ofthe foregoing, it is desirable to have a system and method to measure core temperature that is non-invasive and non-intrusive. It is also desirable to have an inexpensive system that can be used continually to generate consistent and accurate readings, and that can be reused. Additionally, it is desirable to have a system, which allows monitoring ofthe core temperatures of a number of persons from a main terminal.

Summary of the Invention

The present invention fills these needs by providing a temperature telemeter and a method and system to measure a body temperature. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device or a method. Several inventive embodiments of the present invention are described below.

In a first embodiment of the present invention, a temperature telemetric sender is provided. The temperature telemetric sender includes a sensor to measure a temperature of a body cavity, preferably an ear canal, of a subject. A transmitter coupled to the sensor is responsive to the sensor and transmits a signal indicative of the temperature of the body cavity of the subject.

In a second embodiment of the present invention, a temperature telemeter includes the telemetric sender of the first embodiment, and a receiver which receives the signal wirelessly from the transmitter.

The temperature telemetric sender preferably includes a housing to support the sensor and the transmitter.

Preferably, the housing secures the temperature telemeter to the ear canal. The housing is also preferably shaped to fit in the ear canal. Additionally, the temperature telemeter preferably includes a modulator, coupled between the sensor and the transmitter, to amplify the signal. Preferably, the temperature telemeter includes a battery housing for supporting a battery to provide power for the sensor and the transmitter.

The receiver preferably includes uses a conversion algorithm to convert the temperature indicative signal to an estimation of a core body temperature of the subject. Preferably, the core temperature is displayed on a monitor included at the receiver. In a preferred embodiment, the temperature telemeter includes an ambient temperature sensor to measure an ambient temperature. The ambient temperature sensor may be located at the receiver or telemetric sender. The receiver preferably uses a conversion algorithm to compensate the temperature indicative signal for changes in ambient temperature. The ambient compensated temperature may then be displayed on a monitor.

A preferred embodiment includes a store for storing values indicative of a plurality of temperatures of the subject. The stored temperature values may be displayed in a graphical form on a monitor. The receiver may include an alarm which provides an alarm indication when the signal received from the transmitter, or a temperature value derived from that signal, is indicative of a temperature which equals a predetermined temperature or falls outside a predetermined range.

In another embodiment of the invention, a method for measuring a body temperature of a subject is provided. The method includes the measuring of a temperature at a body cavity of the subject to generate a temperature measurement, which is provided to a transmitter and transmitted wirelessly for reception by a receiver, where it is optionally displayed. Preferably the body cavity is an ear canal of the subject. The temperature may be converted to an estimated core body temperature using a conversion algorithm. The estimation of a core body temperature may be displayed at the receiver. Preferably, an alarm is provided when the temperature equals a predetermined temperature or falls outside a predetermined temperature range. The method may include measuring an ambient temperature, preferably at the transmitter or receiver, and using the ambient temperature measurement in an algorithm to compensate the temperature measurement received by the receiver for changes in ambient temperature. The compensated temperature may be displayed at the receiver. A preferred embodiment includes the storing of values indicative of temperatures of the subject and the displaying of the stored values in graphical form. The method may also provide an alarm indication when the temperature measurement received from the transmitter, or a temperature value derived from that measurement, is indicative of a temperature which equals a predetermined temperature or falls outside a predetermined range.

In yet another embodiment of the invention, a temperature telemetric system is provided. The temperature telemetric system includes a plurality of temperature telemetric senders according to the first aspect noted above. Each of the plurality of temperature telemetric senders includes a sensor to measure a temperature of a body cavity, preferably an ear canal, of a subject, and a transmitter which is coupled to the sensor and is responsive to the sensor. The transmitter transmits a signal indicative of the temperature of the body cavity of the subject. A common receiver receives the signals wirelessly from the transmitters of each of the plurality of temperature telemetric senders. The common receiver may include a monitor to display one or more temperatures, preferably of the body cavities as measured by the sensors.

The common receiver may include a conversion algorithm to convert the signals received from the transmitters to estimations of core body temperatures of the subjects, and the common receiver may include a monitor to display the estimations of the core body temperatures.

The temperature telemeter system preferably includes at least one ambient temperature sensor for making a measurement of ambient temperature, and may have a correction algorithm which uses the ambient temperature measurement to compensate one or more of the transmitted signals indicative of temperatures of the subjects for changes in ambient temperature. The at least one ambient temperature sensor may be located at the common receiver or at one of the telemetric senders.

The temperature telemeter system preferably includes a store for storing values indicative of a plurality of temperatures of the subject and the common receiver may include a monitor for displaying the stored temperature values in graphical form. The common receiver preferably includes an alarm which provides an alarm indication when at least one of the signals received from the transmitters is indicative of a temperature which equals a predetermined temperature or falls outside a predetermined temperature range.

In yet a further embodiment of the invention, a temperature telemeter system includes: a plurality of temperature telemetric senders each according to the first embodiment; a corresponding plurality of respective relaying transceivers, wherein each transceiver is for wearing on the body of a respective subject, and each transceiver is for wirelessly receiving said signal from the respective one of the transmitters of the telemetric sender worn by the respective subject, and wirelessly transmitting a relay signal; and a common receiver to wirelessly receive said relay signals from each of said transceivers. Preferably the common receiver includes a monitor to display one or more temperatures which are preferably the temperatures of the body cavities as measured by the sensors.

The common receiver may include a conversion algorithm to convert the signals relayed from the transmitters to estimations of core body temperatures of the subjects which may be displayed on a monitor.

Preferably, the temperature telemeter system also includes at least one ambient temperature sensor for making a measurement of ambient temperature, and may include a correction algorithm which uses the ambient temperature measurement to compensate one or more of the signals relayed from the transmitters for changes in ambient temperature. The at least one ambient temperature sensor may be located at the common receiver or multiple ambient temperature sensors may be respectively located at each of the relaying transceivers.

Preferably, the temperature telemeter system includes a store for storing values indicative of a plurality of temperatures of the subjects. The stored temperature values may be displayed in a graphical form by a monitor.

The common receiver may include an alarm which provides an alarm indication when at least one of the signals relayed from the transmitters is indicative of a temperature which equals a predetermined temperature or falls outside a predetermined temperature range. Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. Brief Description of the Drawings

The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements.

Figure 1 illustrates a conventional ear temperature monitor.

Figure 2 illustrates a schematic of a temperature telemeter in accordance with a first embodiment of the present invention.

Figure 3 illustrates a perspective view of a temperature telemeter in accordance with a second embodiment of the present invention.

Figure 4 illustrates an anatomical view of an ear canal with a probe inserted therein in accordance with a second embodiment of the present invention.

Figure 5a illustrates a scatter diagram of T_ec as a function of T_re based on data obtained from a trial conducted on one embodiment of the present invention.

Figure 5b illustrates a scatter diagram of T_ec as a function of T_gi based on data obtained from a trial conducted on one embodiment of the present invention.

Figure 5c illustrates a scatter diagram of T_ec as a function of T_alt based on data obtained from a trial conducted on one embodiment of the present invention.

Figure 6 illustrates a perspective view of a subject wearing a temperature telemeter in accordance with a second embodiment of the present invention.

Figure 7 illustrates an anatomical view of an ear canal with a probe inserted therein in accordance with a third embodiment of the present invention.

Figure 8 illustrates a schematic of a temperature telemeter in accordance with a fourth embodiment of the present invention. Figure 9 illustrates an anatomical view of an ear canal with a probe inserted therein in accordance with a fourth embodiment of the present invention.

Figure 10 illustrates a schematic of temperature telemetric system in accordance with a fifth embodiment of the present invention.

Detailed Description of the Preferred Embodiments

A temperature telemeter and a method to measure a body temperature are provided. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be understood, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.

Figure 2 illustrates a schematic of a temperature telemeter 50 in accordance with a first embodiment of the present invention. Temperature telemeter 50 comprises telemetric sender with a sensor 52 enclosed in a probe 54 coupled to a housing 56, which supports a modulator 58, a transmitter 60 and a battery casing 62. A battery supported by battery casing 62 may be used to power sensor 52, modulator 58, and transmitter 60. Temperature telemeter 50 further comprises a monitor 64, which receives temperature signals wirelessly from transmitter 60.

Probe 54 is inserted into a body cavity, such as an ear canal, under an armpit, in a mouth, etc., so that sensor 52 can measure the temperature in the body cavity (T_bc) and generate a temperature signal. Sensor 52 is positioned near the surface of probe 54 so that sensor 52 will be in close proximity to the surface of the body cavity. This facilitates the attainment of a more accurate temperature measurement. The temperature signal generated by sensor 52 is relayed to modulator 58. Modulator 58 varies the amplitude, frequency, and/or phase of the temperature signal to an appropriate waveform for transmission by transmitter 60.

Monitor 64 receives the temperature signal wirelessly from transmitter 60 and displays T_bc in real-time. Additionally, the temperature signals received by monitor 64 may be stored and collated so that T_bc can be displayed in a graphical form when prompted by a subject. The option to display T_bc graphically allows the subject to keep track of the changes in T_bc more easily. To facilitate mobility, monitor 64 may be implemented in a form like a watch, to be worn on a wrist, or as a pager, which could be attached to a belt or kept in the subject's pocket.

An alarm 66 in monitor 64 alerts the subject when T_bc exceeds or falls below a pre-programmed temperature range. The warning given by alarm 66 can be auditory, such as a beep, a string of notes, etc., or vibratory. Alarm 66 can also be programmed to emit different types of signals depending on the severity of the incursion outside the preprogrammed temperature range. If information regarding an individual subject's physical conditions and abilities is available, alarm 66 can be tailored to suit a specific subject's requirements.

A battery to provide electrical energy to operate sensor 52, modulator 58 and transmitter 60 is inserted into battery casing 62. Battery casing 62 is designed such that the battery can be easily removed and replaced once the battery is flat so that temperature telemeter 50 can be reused. Many types of batteries may be implemented to provide power for the present invention. For example, two 1.55 Nolt silver oxide batteries have been successfully implemented.

Figure 3 illustrates a temperature telemeter 100 in accordance with a second embodiment of the present invention. Temperature telemeter 100 comprises a probe 102 coupled to a housing 104 by a flexible wire 106. Further, temperature telemeter 100 includes a monitor 108, which receives temperature signals wirelessly from a transmitter supported in housing 104.

A sensor 110, enclosed in probe 102, is inserted into an ear canal 150 as illustrated in Figure 4 to measure the temperature (T_ec) in ear canal 150. Sensor 110 is located close to the surface of probe 102 so that sensor 110 will be in close proximity of the surface of ear canal 150. This facilitates the attainment of a more accurate temperature measurement. The sensor is also placed as close as possible to the tympanic membrane 152. A housing (hidden from view in Figure 4 but shown in Figure 6, as will be explained further below) is placed behind an earlobe 154, and is coupled to flexible wire 106, which extends around the top of earlobe 154. Probe 102 may be molded according to the ear impression of a subject to obtain a better fit. As an alternative, sensor 110 may be embedded in a piece of foam or any other malleable material. With a better fit, probe 102 will be more securely positioned in ear canal 150 and will not be easily dislodged. The subject is then able to carry out vigorous activities without fears of dislodging probe 102.

In the process of measuring T_ec, a temperature signal is generated by sensor 110.

Referring back to Figure 3, a modulator, supported in housing 104, receives the temperature signal from sensor 110 and adjusts the amplitude, frequency, and/or phase of the temperature signal to an appropriate waveform before transmission by the transmitter to monitor 108.

The temperature signal, transmitted wirelessly by the transmitter, is received in monitor 108 and may be converted into a digital form. T_ec can then be displayed digitally on a display 112, such as a liquid crystal display (LCD). Alternatively, the display may be a bar graph where temperature is indicated by the number of bars being displayed. The colour of the bars may change when a predetermined temperature alarm condition is reached. As described in the previous illustration, the option of displaying T_ec graphically is also available. For example, a graphical display may take the form of a temperature- time graph with co-ordinate axes of time and temperature. Having a graphical display is advantageous to track the history of changes in the T_ec of a subject.

An indication of temperature may be provided as an aural signal, for example an artificial voice may provide a spoken indication of the temperature.

Monitor 108 preferably includes a processor to execute a compensation algorithm to perform calculations to compensate for changes in ambient temperature (T_lmb). A T_amb sensor may be coupled to monitor 108 to measure T_amb. With T_amb as an input, the compensation algorithm is able to perform the appropriate calculations to generate a good estimate of T_c. The T_amb sensor may be located at the monitor 108. As an alternative, the T_amb sensor can also be located in the external ear at the probe 102, or outside the ear canal, for example, behind the external ear, at the housing 104. Additionally, the present invention may include sensors to measure a variety of environmental conditions, such as dry bulb temperature, relative humidity, globe temperature, wet bulb temperature, and solar radiation. Additionally, the present invention may be integrated with other sensors to measure physiological conditions, such as heart rate, blood pressure, blood oxygen saturation, and electrocardiogram (ECG). In addition, the present invention may include a microphone to aid the subject's hearing.

At present, rectal (T_re) and esophageal (T_es) temperatures are the most commonly used indicators of T_c. Comparatively, T_ec is a less frequently used indicator of T_c. However, the present invention provides for a method of measuring T_ec to estimate T_c in occupational settings (or where the subject is active). In such environments, where temperature related disorders pose health and safety risks, T_ec is much more convenient and less intrusive to measure than T_re and T_es, or temperatures at other body orifices or cavities, such as the vagina or mouth, because it is less invasive and cumbersome and allows the subject to continue with minimal if any impediment to normal movements and functions. Although the use of a temperature telemeter in an ear canal may cause some impairment of normal binaural hearing, that impairment will be limited to one ear, and will not affect hearing in the other ear. A temperature telemetric device according to the current invention can be readily mounted in an ear canal with little or no invasion of the privacy of the subject, and with a reduced risk of infection when compared to the insertion and location of such devices in other body orifices which secrete greater quantities of mucus.

T_ec is seldomly used by thermal physiologists in research due to the difficulty in obtaining accurate measurements. Ideally, a temperature measurement should be measured as close as possible to the tympanic membrane. However, this poses a health and safety risk as there is a danger that the tympanic membrane may be pierced by accident, rendering a person deaf or partially deaf as a result. As such, the temperature T_ec is usually measured along the ear canal instead.

A study has been conducted to evaluate the validity of T_ec as a surrogate measure of T_c and to establish the relationship between T_re and T_ec. T_re was measured by a rectal probe (YSI, USA) inserted 10 centimeters (cm) into the rectum. Gastrointestinal temperature (T_gi) was measured through a temperature sensor pill (CorTemp, USA). A probe in accordance with one embodiment of the present invention was inserted by about 1.5 cm into one ear to monitor T_ec, whilst a conventional T_ec measurement device (Quest Technologies, USA) was inserted into the other ear to monitor the temperature in the other ear (T_alt).

A trial was conducted in a climatic chamber programmed at 35°C ambient temperature, 70% relative humidity and 800 Watts per square meter (W.m^~2) of simulated solar simulation, and the trial subjects were clothed in military uniforms made of 50% cotton and 50% polyester. During the trial, the trial subjects were asked to walk on a treadmill at a pace that corresponded with 70% to 80% of their heart rate reserve (HRR) and were allowed to consume water freely. T_ec, T_re, T_gi and T_all of each test subject were recorded at intervals of 15 seconds, 1 minute, 15 seconds, and 10 seconds, respectively. The trial ceased after a trial subject's T_re reached 39.5°C and remained at or above this temperature for at least 1 minute. The data collected was then analyzed. A statistical significance (p-value) of less than 0.05 was deemed an acceptable level of error.

The relationships between T_ec, T_re, T_gi and T_aU were analyzed with the Pearson Product Moment Correlation (r), which reflects the linear relationship between a pair of variables. Pearson's correlation (r) ranges from +1 to -1, with a value of +1 indicating a perfect positive linear relationship between the pair of variables. Similarly, high positive r-values indicate a strong positive linear relationship between the pair of variables. The data obtained from the trial was used to plot scatter diagrams of T_ec as a function of T_re, T_gi and T_a,„. The scatter diagrams are useful for evaluating the nature and degree of relationship between the variables.

Figure 5a illustrates a scatter diagram of T_ec as a function of T_re. The scatter diagram in Figure 5a indicates that there is a positive linear relationship between T_ec and T_re Figure 5b illustrates a scatter diagram of T_ec as a function of T_gi. The scatter diagram in Figure 5b indicates that there is a positive linear relationship between T_ec and T_gi. Figure 5c illustrates a scatter diagram of T_ec as a function of T_all. The scatter diagram in Figure 5c indicates that there is a positive linear relationship between T_ec and T_al. Pearson's correlation (r) between the different types of temperature measurements was then computed with the following formula:

where X = T_ec (°C)

Y = T_re, T_gi or T_alt (°C)

N = Number of data points

A summary of the computed r-values is displayed in Table 1.

Table 1 Pearson's correlation (r) between T_ec, and T_re, T_gi and T alt

^L alt

0.91 0.82 0.87

0.84 0.85

^L alt 0.95

As observed in Table 1, the r-values between T_ec, and T_re, T_gi and T_all are high. This implies that even though the absolute temperature readings were not the same, the changes in T_re, T_gi and T_alt are in tandem with changes in T_ec.

However, because Pearson's correlation measures the strength of a relation between a pair of variables, but not the agreement between the pair of variables, further calculations were conducted to verify the agreement between the pair of variables. Perfect agreement is only attained if a data point lies on the line of equality, that is, the line of best fit drawn through all the data points on a scatter diagram. The agreement between the variables can be measured by computing the coefficient of determination (r²), which indicates the percentage of data points, which lie on the line of equality. A summary of the r²- values calculated from the r-values in Table 1 is displayed in Table 2.

Table 2 Coefficient of determination (r²) between T_ec, and T_re, T_ύ and T alt

^l alt

0.83 0.67 0.76

0.71 0.73

T_aIt 0.91

The results in Table 2 indicate that 76%, 73% and 91% of the data points in Figures 5a, 5b and 5c, respectively, are in agreement. The significantly high r and r² values reported in the current study demonstrate that T_ec is indeed a valid indication of T_c, that is, that T_ec can be used as an indirect measure of T_c.

In a preferred embodiment of the present invention, a conversion algorithm having a regression equation is used to estimate T_c, T_re, or T_gi from T_ec measured by a sensor. The regression equation can be obtained by performing linear regression on the data points plotted in a scatter diagram. For example, a linear regression performed on the data plotted in Figures 5a and 5b gave rise to the following prediction models:

T_re = 0.795 (T_ec) + 8.507 (2)

T_gi = 0.808 (T_ec) + 8.095 (3)

Monitor 108 with equation (2) programmed therein would display a T_re of 38.7^CC when sensor 110 measures a T_ec of 38°C. Likewise, monitor 108 with equation (3) " programmed therein would display a T_gi of 38.8°C when sensor 110 measures a T_ec of 38°C. Alternatively, the conversion algorithm may be used to convert T_ec to T_re by adding the mean of the error (MOE) between T_ec and T_re to T_ec measured by sensor 110 to obtain T_re. To obtain T_gi, the MOE between T_ec and T_gi is added to T_ec measured by sensor 110. Using the value of the MOE between T_re and T_ec in Figure 5a, that is, 0.81°C, a T_ec of 38°C would correspond to a T_re of 38.81°C. The conversion algorithm can also be programmed to perform both types of conversion, that is, from T_ec to both T_re and T_gj. The methodology described above may be applied to obtain a conversion algorithm in respect of any body cavity, such as the armpit or the mouth.

With reference to Figure 3, housing 104 also supports a battery casing 114, in which a battery, such as a pair of 1.55 Volts silver oxide batteries, may be inserted. The battery is coupled to and provides power for sensor 110, the modulator, and the transmitter. Battery casing 114 includes a battery casing door 116 with a tab 118, which assists in the opening and closing of battery casing door 116.

Figure 6 illustrates a perspective view of a subject 160 wearing temperature telemeter 100, shown in Figure 3, in accordance with the second embodiment of the present invention. Housing 104, which is placed behind an earlobe 154, is coupled to flexible wire 106, which extends around the top of earlobe 154. This arrangement of housing 104 and flexible wire 106 secures housing 104 to subject 160 and allows temperature telemeter 100 to access the ear canal of subject 160.

Figure 7 illustrates an anatomical view of an ear canal 200 with a probe 202 inserted therein in accordance with a third embodiment of the present invention. Probe 202 is coupled to a housing 204 located in earlobe 206. Housing 204 preferably supports a modulator, a transmitter and a battery casing having a battery casing door 210. A sensor enclosed in probe 202 measures T_ec in ear canal 200 and generates a temperature signal, which is relayed to the modulator in housing 204. The modulator varies the amplitude, frequency, and/or phase of the temperature signal to an appropriate waveform before transmission by the transmitter in housing 204. The temperature signal, which is transmitted wirelessly by the transmitter, is received by a receiver and preferably displayed on a monitor. The sensor is located close to the surface of probe 202 so that the sensor will be as close as possible to the surface of ear canal 200. This facilitates the attainment of a more accurate temperature measurement. As discussed previously, the sensor is also placed as close as possible to a tympanic membrane 208. Probe 202 may be molded to an ear impression of a subject, or embedded in a piece of foam or any other malleable material to obtain a better fit.

Figure 8 illustrates a schematic of a temperature telemeter 250 in accordance with a fourth embodiment of the present invention. Temperature telemeter 250 comprises a probe 252 in which a sensor 254, a modulator 256, a transmitter 258 and a battery casing 260 are enclosed. Temperature telemeter 250 further comprises a monitor 262, which receives temperature signals wirelessly from transmitter 258.

Probe 252 is inserted into a body cavity so that sensor 254 can measure T_bc and generate a temperature signal. Sensor 254 is positioned close to the surface of probe 252 so that sensor 254 will be in close proximity to the surface of the body cavity. This facilitates the attainment of a more accurate temperature measurement. The temperature signal generated is relayed to modulator 256. Modulator 256 varies the amplitude, frequency, and phase of the temperature signal to an appropriate waveform for transmission by transmitter 258.

Monitor 262 receives the temperature signal wirelessly from transmitter 258 and preferably displays the temperature in real-time. The temperature signals received are preferably converted into a digital form for display, for example by a liquid crystal display (LCD). Alternatively, the display may be a bar graph where temperature is indicated by the number of bars being displayed. The colour of the bars may change when a predetermined temperature alarm condition is reached. Additionally, the temperature signals received by monitor 262 may be stored and collated so that T_bc can be displayed in a graphical form, for example when prompted by a subject, and may be in the form of a temperature-time graph with co-ordinate axes of time and temperature. The option to display T_bc graphically allows the subject to keep track of the changes in T_bc more readily. An indication of temperature may be provided as an aural signal, for example an artificial voice may provide a spoken indication of the temperature. To facilitate mobility, monitor 262 may be implemented in a form like a watch, to be worn on a wrist, or as a pager, which could be attached to a belt or kept in a subject's pocket.

An alarm 264 in monitor 262 may be used to alert the subject when T_bc exceeds or falls below a pre-programmed temperature range. The warning given by alarm 264 can be a visible alarm, such as a flashing light or a blinking display, or may be auditory, such as a beep, a string of notes, etc., or vibratory. Alarm 264 can also be programmed to emit different types of signals to indicate different temperatures. If a database of an individual subject's physical condition and ability is available, alarm 264 can be tailored to suit that subject's requirements.

A battery to provide electrical energy to operate sensor 254, modulator 256 and transmitter 258 may be inserted into battery casing 260. Battery casing 260 is designed such that the battery can be easily removed and replaced once the battery is flat so that temperature telemeter 250 can be reused. Probe 252 of temperature telemeter 250 can be inserted into an ear canal 300 as illustrated in Figure 9.

Figure 9 illustrates an anatomical view of ear canal 300 with probe 252 inserted therein in accordance with the fourth embodiment of the present invention. As described above, probe 252 comprises a sensor 254, a modulator, a transmitter and a battery casing. The sensor 254 is located close to the surface of probe 252 so that the sensor will be as close as possible to the surface of ear canal 300. This facilitates the attainment of a more accurate temperature measurement. As discussed previously, the sensor is also placed as close as possible to the tympanic membrane 302. Probe 252 further comprises a battery casing door 266 and a door pull 268. By using door pull 268, battery casing door 266 can be opened to insert a battery or to remove a flat battery. Although door pull 268 is depicted in this embodiment as a string with a knob on one end, it will be appreciated that door pull 268 can also be any device that assists in removing probe 252 from ear canal 300.

Figure 10 illustrates a schematic of temperature telemetric system 400 in accordance with a fifth embodiment of the present invention. Temperature telemetric system 400 comprises a central receiver or monitor 402, which receives temperature signals wirelessly from a plurality of temperature telemeters 404, which are used to monitor the temperature of multiple subjects. The system includes a plurality of warning devices 406. A warning device is respectively coupled to each telemeter 404. Central monitor 402 is preferably used to display T_bc in real-time on a screen 408. Central monitor 402 is also preferably equipped with an alarm 410 to alert a supervisor when T_bc of any subject exceeds or falls below a pre-programmed temperature range.

Temperature telemetric system 400 can be implemented in situations where T_c of a number of persons need monitoring, for instance, an ICU in a hospital, where T_c of a number of patients must be monitored at any one time. Temperature telemetric system

400 is also applicable for military purposes as it would allow a commander to monitor the state of each soldier deployed.

In another embodiment of the invention a telemetric sender, such as a combination of a temperature sensor and a wireless transmitter, is located in a body cavity, for example and ear canal, as discussed above. A temperature measurement is transmitted to a relay transceiver worn on the body. In a preferable arrangement, the relay transceiver is in a form like a watch and is worn on a wrist. The temperature measurement received by the relay transceiver is wirelessly re-transmitted, i.e. relayed, for reception by a remote receiver. The relay transceiver can also include any of the features incorporated in the receiver as already discussed above. For example, the relay transceiver can compensate for ambient temperature, and convert a cavity temperature to an estimation of a core temperature. The relay transceiver can also include a monitor that displays measured temperature values, ambient compensated temperature values, estimated temperatures derived by conversion of measured temperatures, and/or temperature values that are both compensated and converted. These functions are provided in addition to the relay functions by which any of these temperature values can be relayed on to a remotely located common receiver.

This relay arrangement can be extended to multiple sets of telemetric senders and relaying transceivers, with each set being worn by a respective user. The multiple relaying transceivers transmit their respective temperature measurement signals to a common receiver where the temperatures of all users can be monitored, with compensation for ambient temperature changes or conversion to a core body temperature if required. The ambient temperature can be measured at the common receiver, or preferably at each of the relay transceivers so that the temperature measurements of each subject can be compensated for the respective ambient temperature at each subject's location.

This multiple user relay arrangement has particular utility where the users need to be relatively unencumbered or are not confined to a relatively small location. This is in contrast to situations such as an ICU ward, where the embodiment discussed above in respect of Figure 10 may be more suitable. The use of the transceivers can extend the range between the users and the common receiver, without requiring a bulky battery or transmitter to be located at or closely adjacent the temperature measurement site. A very small in-ear device, located entirely within the ear canal, can provide a sufficiently strong signal for reception by the wrist-worn relay transceiver which provides a relatively strong signal for retransmission to the common receiver.

In one particularly advantageous arrangement of the temperature relaying embodiment, the in-ear telemetric sender components are a combination of a temperature sensor and a transponder. The transponder is a passive device which requires no battery. The passive transponder is responsive to the sensor temperature and emits a temperature indicative signal in response to reception of an interrogation signal transmitted by the wrist-worn relay transceiver. The temperature indication emitted by the transponder is received by the relay transceiver which, being larger than the in-ear transponder, can accommodate a battery and can therefore retransmit the temperature indication at a relatively high power level for reception by the common receiver.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention. Furthermore, certain terminology has been used for the purposes of descriptive clarity, and not to limit the present invention. The embodiments and preferred features described above should be considered exemplary, with the invention being defined by the appended claims.

Claims

1. A temperature telemetric sender, comprising:

5 a sensor (52) to measure a temperature of a body cavity of a subject, and a transmitter (60) coupled to said sensor; wherein said transmitter is responsive to said sensor, and wherein said transmitter transmits a signal indicative of the temperature of the body cavity of the subject.

L0 2. The temperature telemetric sender as claimed in claim 1, wherein said body cavity is an ear canal of the subject.

3. The temperature telemetric sender as claimed in claim 2, further comprising a housing to support the sensor and the transmitter, wherein said housing is to

15 secure the temperature telemetric sender to the ear canal.

4. The temperature telemetric sender as claimed in claim 3, wherein the housing is shaped to fit in the ear canal.

0 5. The temperature telemetric sender as claimed in any preceding claim, further comprising a modulator (58) coupled between the sensor and the transmitter, wherein said modulator is to amplify the signal.

6. The temperature telemetric sender as claimed in any preceding claim, 5 further comprising a battery housing (62) for supporting a battery, wherein said battery is to provide power for the sensor and the transmitter.

7. A temperature telemeter (50), comprising: the temperature telemetric sender as claimed in any preceding claim, and a receiver (64) to wirelessly receive said signal.

8. The temperature telemeter as claimed in claim 7, wherein the receiver includes a monitor to display a temperature.

9. The temperature telemeter as claimed in claim 8, wherein the monitor displays the temperature of the body cavity as measured by the sensor.

10. The temperature telemeter as claimed in any one of claims 7 to 9, wherein the receiver includes a conversion algorithm to convert the temperature indicative signal received from the transmitter to an estimation of a core body temperature of the subject.

11. The temperature telemeter as claimed in claim 10, wherein the receiver includes a monitor to display the estimation of a core body temperature of the subject.

12. The temperature telemeter as claimed in any one of claims 7 to 11, further comprising an ambient temperature sensor for making a measurement of ambient temperature.

13. The temperature telemeter as claimed in claim 12, further comprising a correction algorithm which uses the ambient temperature measurement to compensate the temperature indicative signal received from the transmitter for changes in ambient temperature.

14. The temperature telemeter as claimed in claim 12 or 13, wherein the ambient temperature sensor is located at the receiver.

15. The temperature telemeter as claimed in claim 12 or 13, wherein the ambient temperature sensor is located at the telemetric sender.

16. The temperature telemeter as claimed in any one of claims 7 to 15, further comprising a store for storing values indicative of a plurality of temperatures of the subject.

17. The temperature telemeter as claimed in claim 16, wherein the receiver includes a monitor for displaying the stored temperature values in graphical form.

18. The temperature telemeter (50) as claimed in any one of claims 7 to. 17, wherein the receiver (64) includes an alarm (66) which provides an alarm indication when the signal received from the transmitter (60), or a temperature value derived from the signal received from the transmitter, is indicative of a temperature which equals a predetermined temperature or falls outside a predetermined temperature range.

19. A method for measuring a body temperature of a subject, comprising the steps of: measuring a temperature at a body cavity of said subject to generate a temperature measurement, providing the temperature measurement to a transmitter, wirelessly transmitting the temperature measurement to a receiver, and receiving the transmitted temperature measurement by the receiver.

20. A method, for measuring a body temperature of a subject, as claimed in claim 19, wherein the body cavity is an ear canal of the subject.

21. A method, for measuring a body temperature of a subject, as claimed in claim 19 or 20, and further comprising the additional step of: displaying the received temperature measurement at the receiver.

22. A method, for measuring a body temperature of a subject, as claimed in claims 19, 20 or 21, further comprising the additional steps of: measuring an ambient temperature, and using the received temperature measurement and the ambient temperature measurement in an algorithm to compensate the received temperature measurement for changes in ambient temperature and thereby generate a compensated temperature value.

23. A method for measuring a body temperature of a subject as claimed in claim 22, wherein the ambient temperature is measured at the receiver.

24. A method for measuring a body temperature of a subject as claimed in claim 22, wherein the ambient temperature is measured at the transmitter.

25. A method, for measuring a body temperature of a subject, as claimed in claim 22, 23 or 24, and further comprising the additional step of: displaying the compensated temperature value at the receiver.

26. A method, for measuring a body temperature of a subject, as claimed in any one of claims 19 to 25, and further comprising the additional step of: using a conversion algorithm to convert the received temperature measurement to an estimation of a core body temperature of the subject.

27. A method, for measuring a body temperature of a subject, as claimed in claims 19, 20 or 21, further comprising the additional steps of: measuring an ambient temperature, and using the received temperature measurement and the ambient temperature measurement in an algorithm to compensate the received temperature measurement for changes in ambient temperature and to convert the compensated received temperature measurement to an estimation of a core body temperature ofthe subject.

28. A method, for measuring a body temperature of a subject, as claimed in claim 27, wherein the ambient temperature is measured at the receiver.

29. A method, for measuring a body temperature of a subject, as claimed in claim 27, wherein the ambient temperature is measured at the transmitter.

30. A method, for measuring a body temperature of a subject, as claimed in any one of claims 26 to 29, and further comprising the additional step of: displaying the estimation of a core body temperature at the receiver.

31. A method, for measuring a body temperature of a subject, as claimed in any one of claims 19 to 30, and further comprising the additional steps of: storing values indicative of temperatures of the subject, and displaying the temperature indicative values in graphical form.

32. A method, for measuring a body temperature of a subject, as claimed in any one of claims 26 to 30, and further comprising the additional steps of: storing a plurality of estimations of core body temperatures, and displaying the stored estimations of core body temperatures in graphical form.

33. A method, for measuring a body temperature of a subject, as claimed in any one of claims 19 to 32, and further comprising the additional step of: providing an alarm indication when the temperature measurement, or a temperature value derived from the temperature measurement, is indicative of a temperature which equals a predetermined temperature or falls outside a predetermined temperature range.

34. A temperature telemeter system comprising: a plurality of temperature telemetric senders each as claimed in any one of claims

1 to 6; and a common receiver to wirelessly receive said signals from each of the transmitter ofthe telemetric senders.

35. The temperature telemeter system as claimed in claim 34, wherein the common receiver includes a monitor to display one or more temperatures.

36. The temperature telemeter system as claimed in claim 35, wherein the monitor displays the temperatures of the body cavities as measured by the sensors.

37. The temperature telemeter system as claimed in claim 34, 35 or 36, wherein the common receiver includes a conversion algorithm to convert the signals received from the transmitters to estimations of core body temperatures of the subjects.

38. The temperature telemeter system as claimed in claim 37, wherein the common receiver includes a monitor to display the estimations of the core body temperatures.

39. The temperature telemeter system as claimed in any one of claims 34 to 38, further comprising at least one ambient temperature sensor for making a measurement of ambient temperature.

40. The temperature telemeter system as claimed in claim 39, further comprising a correction algorithm which uses the ambient temperature measurement to compensate one or more of the transmitted signals indicative of temperatures of the subjects for changes in ambient temperature.

41. The temperature telemeter system as claimed in claim 39 or 40, wherein the at least one ambient temperature sensor is located at the common receiver.

42. The temperature telemeter system as claimed in claim 39 or 40, wherein the at least one ambient temperature sensor is located at one of the telemetric senders.

43. The temperature telemeter system as claimed in any one of claims 34 to 42, further comprising a store for storing values indicative of a plurality of temperatures of the subjects.

44. The temperature telemeter system as claimed in claim 43, wherein the common receiver includes a monitor for displaying the stored temperature values in graphical form.

45. The temperature telemeter system as claimed in any one of claims 34 to

44, wherein the common receiver includes an alarm which provides an alarm indication when at least one of the signals received from the transmitters is indicative of a temperature which equals a predetermined temperature or falls outside a predetermined temperature range.

46. A temperature telemeter system comprising: a plurality of temperature telemetric senders each as claimed in any one of claims 1 to 6; a corresponding plurality of respective relaying transceivers, each transceiver for wearing on the body of a respective subject, each transceiver for wirelessly receiving said signal from the respective one of the transmitters of the telemetric sender worn by the respective subject, and wirelessly transmitting a relay signal; and a common receiver to wirelessly receive said relay signals from each of said transceivers.

47. The temperature telemeter system as claimed in claim 46, wherein the common receiver includes a monitor to display one or more temperatures.

48. The temperature telemeter system as claimed in claim 47, wherein the monitor displays the temperatures of the body cavities as measured by the sensors.

49. The temperature telemeter system as claimed in claim 46, 47 or 48, wherein the common receiver includes a conversion algorithm to convert the signals relayed from the transmitters to estimations of core body temperatures of the subjects.

50. The temperature telemeter system as claimed in claim 49, wherein the common receiver includes a monitor to display the estimations of the core body temperatures.

51. The temperature telemeter system as claimed in any one of claims 46 to 50, further comprising at least one ambient temperature sensor for making a measurement of ambient temperature.

52. The temperature telemeter system as claimed in claim 51, further comprising a correction algorithm which uses the ambient temperature measurement to compensate one or more of the signals relayed from the transmitters for changes in ambient temperature.

53. The temperature telemeter system as claimed in claim 51 or 52, wherein the at least one ambient temperature sensor is located at the common receiver.

54. The temperature telemeter system as claimed in claim 51 or 52, wherein multiple ambient temperature sensors are respectively located at each of the relaying transceivers.

55. The temperature telemeter system as claimed in any one of claims 46 to 54, further comprising a store for storing values indicative of a plurality of temperatures of the subjects.

56. The temperature telemeter system as claimed in claim 55, wherein the common receiver includes a monitor for displaying the stored temperature values in graphical form.

57. The temperature telemeter system as claimed in any one of claims 46 to

56, wherein the common receiver includes an alarm which provides an alarm indication when at least one of the signals relayed from the transmitters is indicative of a temperature which equals a predetermined temperature or falls outside a predetermined temperature range.