Device and method for determining human core body temperature

Abstract

The invention relates to a device (1) for determining human deep body temperature (CBT), intended to be placed on a limb segment of the body and characterized in that it comprises a module (2) for estimating blood perfusion flowing throughout the limb segment of the body; a module (3) for measuring skin surface temperature and heat flux; a central unit (5) connected to the module (2) for estimating blood perfusion flowing throughout the entire limb segment and to the module (3) for measuring skin surface temperature and heat flux, designed to determine human deep body temperature (CBT) based on at least signals from the connected modules (2, 3); and a support element for the components (2, 3, 5) of the device (1) mounted on said limb segment of the body. The invention also relates to a method of determining human deep body temperature, CBT, characterized in that estimates of the value over time of blood perfusion (Wb(t)) flowing throughout the entire limb segment are determined (S1); the temperature values Temp(t) and heat flux (HF(t)) on the skin of the tested limb segment are recorded (S2); the obtained temperature values Temp(t), heat flux HF(t) and estimates of the value over time of blood perfusion Wb(t) are pre-processed (S3); and the CBT temperature is determined (S4) based on at least the pre- processed values Temp(t), HF(t), Wb(t) using an estimator.

Description

[0001] Device and method for determining human core body temperature

[0002] The invention relates to a device and a method for determining human physiological parameters, and in particular core body temperature. The invention uses a dedicated electronic measuring device comprising a number of sensors and a procedure for determining core body temperature using measurements provided by said sensors. The above features place the subject of this invention in the areas of biomedical engineering, electronics and computer science.

[0003] The results of a number of published studies indicate that the measurement of shell body temperature (SBT) provides valuable information about health. SBT is a derivative of human core body temperature (CBT) (carrying the exact information about health or physiological processes) and environmental conditions. Therefore, the ability to directly measure CBT results in increased accuracy of diagnostic methods. The development of a new, reliable and adapted to applications in everyday use, such as e.g. a band or watch fastening, a tool for non-invasive estimation of CBT will constitute a significant technological and market advantage of the proposed solution in relation to those available on the market.

[0004] Numerous confirmations of these assumptions can be found in the scientific literature, e.g. in the review paper Chen, W., 2019. Thermometry and interpretation of body temperature. Biomed. Eng. Lett. 9, 3-17. https: / / doi.org / 10.1007 / sl3534-019-00102-2 or in the paper Mendt et al., 2017. Circadian rhythms in bed rest: Monitoring core body temperature via heat-flux approach is superior to skin surface temperature. Chronobiol. Int. 34, 666-676. https: / / doi.org / 10.1080 / 07420528.2016.1224241, in which CBT is defined as the temperature of deep-seated organs (brain, heart, liver, etc.), which reflects the temperature "operating point" of the body much better than the temperature of tissues located close to the body surface. Compared to the measurement of skin surface temperature (SBT), the usefulness of CBT measurement is much higher, especially in the case of monitoring the body's thermal load during work or exertion.

[0005] Applications of non-invasive continuous core body temperature measurement include many different areas, such as e.g. control of the body's load with exertion and climatic conditions, medical diagnostics or assessment of thermal comfort.

[0006] The first area includes applications related to the protection of health and life against the dangers resulting from working conditions and intensity. Significant strain on the body with exertion and thermal conditions can be dangerous to health and life.

[0007] The second area includes medical applications. Continuous monitoring of core body temperature is useful not only for detecting and monitoring fever in infectious diseases, but is also an important parameter in the assessment of serious medical conditions.

[0008] Another area of potential application of continuous CBT measurement is the assessment and prediction of thermal comfort. Available research shows that measurements of skin temperature, CBT and heat flow between the body and the environment allow for the assessment of thermal sensations and comfort.

[0009] The conducted literature studies indicate a large utility and commercial potential of the wrist- worn CBT meter. Information about the current CBT value and its change history allows for the detection of fever and subfebrile conditions, heat strokes and for the measurement of thermal load, and together with other parameters also the physiological load of the body. In addition to the current CBT control, long-term measurement also provide useful information about the health or physiological condition of a given person.

[0010] CBT measurement methods known in the prior art can be divided into invasive, minimally invasive and non-invasive methods.

[0011] Exemplary invasive methods of CBT measurement use transducers inserted in the form of a needle, in which a temperature sensor (usually a thermistor) is mounted. This is a measurement that violates the continuity of tissues, but at the same time provides the most direct measurement.

[0012] Exemplary minimally invasive methods of CBT measurement include, for example, pill thermometers, which are intended to be swallowed and allow for temperature measurement in the gastrointestinal tract, and devices inserted into body cavities, e.g. in the form of a catheter.

[0013] Non-invasive methods of CBT measurement, on the other hand, can be divided into contactless methods and methods requiring contact of the device with the tested body.

[0014] Contactless measuring devices allow for the estimation of skin temperature (SBT) (most often on the forehead) or the eardrum by measuring infrared radiation emitted by the observed area of the body. Then, the CBT temperature is estimated based on the SBT value. The accuracy of CBT estimation based on SBT is subject to significant error and high sensitivity to external factors.

[0015] Contact, non-invasive methods of CBT measurement can be divided into two groups:

[0016] 1. methods using devices that only measure SBT (most often skin) and methods using

[0017] 2. devices that measure SBT and heat flux (HF) flowing between the body and the environment (air).

[0018] In the first of the aforementioned groups of measurement methods, the temperature of the outer layers (SBT) is measured using devices applied to the skin of the tested person. A typical measurement location is the forehead or armpit. There are also solutions not recommended for medical applications that measure skin temperature on the wrist - these are most often wearable devices in the form of a watch. As in the case of non-contact SBT measurement methods, the CBT temperature is estimated based on the SBT value. The accuracy of CBT estimation based on SBT is subject to a large error and high sensitivity to external factors.

[0019] The second of the aforementioned groups of measurement methods using SBT temperature measurement and heat flux flowing between the body and the environment is a relatively new group of CBT measurement methods. These methods can be divided into active and passive methods.

[0020] An example of an active measurement is the Zero Heat Flux (ZHF) method, which assumes that no heat flows through the external surface of the body if the CBT and ambient temperatures are equal. Such devices include a temperature sensor, a heat flux sensor and a heating element. The heating element on the outside (not directly adjacent to the body) increases its temperature until the heat flux sensor reads zero. Due to the high energy consumption and the size of the sensor, it is difficult to miniaturize and implement it in wearable devices.

[0021] Devices that perform passive measurement are a collection of solutions closest to the solution described in this patent application. Devices of this type contain one (Single Heat Flux - SHF) or two (Dual Heat Flux - DHF) thermal measuring tracks.

[0022] The main principle of CBT measurement using the SHF method is that the CBT estimate (CBTe) can be expressed as a function of heat flux, the heat transfer coefficient of the sensor and the skin surface temperature.

[0023] The heat flux can be measured directly with a heat flux sensor placed between the skin and the sensor material, or indirectly with two temperature sensors measuring the temperature difference between both sides of the sensor's heat-conducting layer.

[0024] The DHF method uses two SHF sensors with different thermal resistances placed close to each other. A detailed description of the SHF and DHF methods is available in numerous prior art publications.

[0025] SHF and / or DHF methods are used in sensors available on the market, such as Bair Hugger™ (3M, Germany), Tcore™ (Dragerwerk, Germany), Temple Touch Pro™, or CORE™ (GreenTeg, Switzerland).

[0026] Solutions are also known from the patent literature in which the accuracy of estimating or determining the CBT temperature is additionally increased by using blood perfusion parameters. They are indicated below.

[0027] US2022338811A1 "Method, System and Device for Noninvasive Core Body Temperature Monitoring" discloses a device and method for measuring human core temperature (CBT). The device shown in Figures 1A and IB is designed to be placed on the skin and includes first and second temperature sensors separated by an insulating layer to measure heat flux. In the solution, a sensor configured to detect physical changes of various kinds can be used, including local (in the skin) blood perfusion measurement. Examples of measurement include optical, interference and acoustic measurement.

[0028] WO2018033799A1 "METHOD AND SYSTEM FOR DETERMINATION OF CORE BODY TEMPERATURE" discloses a method and system for determining human core temperature. The method of determining human core temperature described in claim 1 includes determining the first and second thermal resistance for, respectively, the first and second thermally insulating material connected to the first and second sets of temperature sensors for two heat flux channels; collecting temperature data from the first and second sets of sensors; extracting the perfusion parameter for the time interval based on the temperature data. And determining the CBT measurement associated with the time interval based on the perfusion parameter.

[0029] W02020171701A1 "CORE BODY TEMPERATURE SENSOR AND METHOD FOR THE MANUFACTURING THEREOF" discloses a method and a sensor for measuring human core temperature. The human core temperature sensor is used on the body surface and includes two pairs of thermistors, and is also equipped with means for measuring blood perfusion in the skin under the sensor (claim 1, claim 8, description fragments).

[0030] W02011012386A1 "SENSOR AND METHOD FOR DETERMINING A CORE BODY TEMPERATURE" discloses a sensor and method for determining human core temperature. The user's core body temperature sensor described in claim 1 includes first and second temperature probes separated by a thermal insulator, and - according to claim 4 - may include a probe for measuring the perfusion parameter in the skin. Analogously, the method according to claim 13 may include the step of measuring the perfusion parameter and using it in the formula for calculating the core temperature. A photoplethysmographic (PPG) sensor is indicated as an example of a probe for measuring the perfusion parameter in the solution description.

[0031] US2022395185A1 "APPARATUS AND METHOD FOR ESTIMATING BODY TEMPERATURE" discloses a device and method for estimating body temperature. The body temperature estimation device described in claim 1 includes multiple sensors for receiving data from the object and a processor that receives the surface temperature, heat flux, intensity and rate of blood flow in the skin based on data from multiple sensors and estimates the core body temperature based on this. According to claim 4, one of the sensors may be a PPG sensor.

[0032] U.S. provisional application 61 / 912,201 "NON-INVASIVE THERMOMETER WITH PERSONALIZED CORRECTION TO CORE AND FAST PREDICTION ALGORITHM FOR THERMOMETER" relates to a non-invasive thermometer with personalized core temperature correction and a fast core temperature prediction algorithm. Sections A3 and B3 describe the use of a PPG sensor. Section B2 describes the use of bio-impedance (measured using two electrodes applied to tissues) to correct temperature determination. B3 refers to section Bl, which describes an overlay placed on the skin (Fig. 5) with two layers containing temperature sensors, separated by insulation, to allow measurement of heat flux in an unsteady state (after applying the thermometer to the body). The relationship between the measured skin temperature and the heat flux value allows to infer the core temperature value.

[0033] The purpose of the present invention is to develop a method and device for determining human core temperature using an integrated system of sensors, intended for use on limb segments, which ensure accurate and reliable measurement.

[0034] The above-mentioned purpose is achieved by the method and device described in the independent claims. Advantageous variants of the invention are indicated in the dependent claims.

[0035] According to the invention, a device for determining human core body temperature, intended to be placed on a limb segment of the body, is provided, characterized in that it comprises a module for estimating perfusion of blood flowing throughout the entire limb segment; a module for measuring skin surface temperature and heat flux; a central unit connected to the module for estimating blood perfusion flowing throughout the entire limb segment and to the module for measuring skin surface temperature and heat flux density, designed to determine human core body temperature based on at least signals from the connected modules; and a support element for the device components mounted on said limb segment.

[0036] In one advantageous embodiment of the device, the module for estimating blood perfusion flowing throughout the limb segment is implemented as an impedance rheograph comprising at least one pair of electrodes applied to the limb segment, wherein the measurement signal of the electrical impedance of the entire limb segment constitutes the basis for determining the estimate of blood perfusion flowing throughout the limb segment.

[0037] In another advantageous embodiment of the device, the module for estimating blood perfusion flowing throughout the limb segment of the body comprises two or more pairs of electrodes, each pair comprising an application electrode and a measuring electrode, and a multiplexer for switching between successive pairs of electrodes.

[0038] In another advantageous embodiment of the device, the module for estimating blood perfusion flowing throughout the entire limb segment of the body is implemented as a plethysmographic module or an ultrasonic measuring device.

[0039] In another advantageous embodiment of the device, the module for measuring skin surface temperature and heat flux is a single-channel SHF (Single Heat Flux) module or a two-channel DHF (Dual Heat Flux) module or a multi-channel MHF (Multi Heat Flux) module.

[0040] In another advantageous embodiment of the device, each channel of the SHF or DHF or MHF module comprises one temperature sensor and one heat flux sensor or two temperature sensors separated by an element made of a heat-conducting material.

[0041] In another advantageous embodiment, the device further comprises a communication circuit, in particular a Bluetooth wireless communication circuit, connected to or integrated with the central unit, designed to transmit measurement data and / or the determined CBT temperature to an external device.

[0042] In another advantageous embodiment, the device further comprises a pre-processing and / or analog-to-digital conversion (A / D) circuit, the input of which is connected to the output of the module for measuring skin surface temperature and heat flux, and a pre-processing and / or analog- to-digital conversion (A / D) circuit, the input of which is connected to the output of the blood perfusion estimation module, wherein the outputs of the circuits are connected to the central unit.

[0043] In another advantageous embodiment of the device, one or more of: the module for estimating blood perfusion flowing throughout the entire limb segment, the module for measuring skin surface temperature and heat flux, the pre-processing and / or analog-to-digital conversion circuits, the central unit and the communication circuit are integrated into one electronic module.

[0044] In another advantageous embodiment, the device further comprises one or more additional sensors connected to the central unit, wherein one or more of the sensors include inertial sensors, in particular an accelerometer and / or a gyroscope, an ECG sensor, a PPG sensor or skin blood perfusion sensors at the measurement site, wherein the signals from one or more additional sensors are taken into account by the central unit when determining the CBT temperature.

[0045] In another advantageous embodiment of the device, the support element for the device components is a fastening, in particular a butterfly clasp, of a band, in particular a watch band, worn on the wrist, wherein the measuring electrodes are integrated into rigid brackets protruding from the sides of the butterfly clasp or the measuring electrodes are mounted on an inner part of the band.

[0046] In another advantageous embodiment of the device, the support element for the device components is a band worn on the wrist, in particular a watch band, wherein the measuring electrodes) are mounted on an inner part of the band.

[0047] In another advantageous embodiment of the device, the support element for the device components is a watch worn on the wrist, wherein the measuring electrodes are mounted on an inner part of the watch band.

[0048] According to the invention, there is also provided a method of determining human core body temperature, characterized by determining estimates of the value over time of blood perfusion flowing throughout the entire limb segment; recording values of temperature and heat flux on the skin of the tested limb segment; pre-processing the obtained values of temperature, heat flux and the estimates of the value over time of blood perfusion; determining the CBT temperature based on at least the pre-processed values using an estimator.

[0049] In one advantageous embodiment of the method, the estimates of the value over time of blood perfusion flowing throughout the entire limb segment are determined by the rheography method by recording the values of changes in impedance of tissues forming the tested body segment using at least one pair of electrodes applied to the tested limb segment of the body and processing the recorded values of changes in impedance into estimates of the value over time of blood perfusion flowing throughout the entire limb segment. In another advantageous embodiment of the method, the estimates of the value over time of blood perfusion flowing throughout the entire limb segment of the body are determined by a plethysmography method or an ultrasonic flow measurement method.

[0050] In another advantageous embodiment of the method, when determining the CBT temperature using an estimator, the size of the limb on which the measurement is taken is taken into account, in particular the radius of the limb cross-section at the measurement site.

[0051] In another advantageous embodiment of the method, the recorded values of impedance changes are further processed into estimates of heart rate and / or changes in skin conductivity or / and tissue composition, in particular the proportion of water, fat, muscles in the total mass of the body segment, in the processing step, pre-processed in step together with other parameters and taken into account in the estimator in step of determining the CBT temperature.

[0052] In another advantageous embodiment of the method, when determining the CBT temperature, biometric data is taken into account, in particular the user's gender, weight, limb lengths, and / or optional data and signals are taken into account, in particular ambient temperature, wind speed, type and intensity of physical activity performed by the user.

[0053] In another advantageous embodiment of the method, the estimator implementing the stage of determining the CBT temperature has the form of an analytical or statistical model or a mixture of both approaches, and in particular a regression model obtained by applying machine learning or deep machine learning methods.

[0054] The essence of the invention is to combine in one device sensors of skin surface temperature and heat flux flowing between tissues and air, and sensors enabling estimation of blood perfusion in the entire cross-section of the limb segment on which the device is placed, and optionally sensors for measuring local perfusion, e.g. in the skin at the measurement site, together with methods of processing recorded signals in order to increase the accuracy of CBT measurement. In contrast to the solutions disclosed in the patent literature, the perfusion measurement in the present invention is not local in nature, but relates to the entire body segment (e.g. forearm or wrist) or represents (correlates) with the value measured in this way (the local measurement may be complementary). Moreover, the measurement of temperature, heat flux and blood perfusion takes place continuously, unlike the CBT measurement method, which is based on measuring the temperature on the surface or dynamic estimation of this temperature in a steady state. A significant distinguishing feature is also the possibility of taking into account in the measurement the size of the limb on which the measurement is taken in the form of the radius of the limb cross-section at the measurement site estimated on the basis of, for example, the limb circumference at the measurement site or the cross-sectional area estimate. The device is dedicated to be placed on peripheral body segments such as limbs, and in particular on wrists. The device can be made in the form of a dedicated wearable device such as a watch or (after miniaturization) be an element of other wearable devices by integrating with a band or in a clasp (fastening) for a watch or jewelry. In addition to CBT measurement, the device can provide information about other vital parameters such as heart rate, degree of body hydration, tissue composition, blood oxygen saturation, blood perfusion, tissue impedance or skin-galvanic reaction. This set of data can be used to assess the well-being or burden on the body by various factors, including stress, physical activity, climatic conditions.

[0055] The invention will become better understood after reading the detailed description of its exemplary embodiments. The subject of the invention in the examples of implementation is shown in the drawing, in which:

[0056] Fig. 1 shows the general structure and principle of operation of the device according to the invention;

[0057] Fig. 2 shows a module for measuring skin surface temperature and heat flux in a single-channel (SHF) variant with a temperature sensor and a heat flux sensor.

[0058] Fig. 3 shows a module for measuring skin surface temperature and heat flux in a single-channel (SHF) variant with two temperature sensors;

[0059] Fig. 4 shows a module for measuring skin surface temperature and heat flux in a two-channel (DHF) variant with two pairs of temperature and heat flux sensors;

[0060] Fig. 5 shows a module for measuring skin surface temperature and heat flux in a two-channel (DHF) variant with four temperature sensors;

[0061] Fig. 6 shows a diagram of the method of signal processing and temperature value estimation;

[0062] Fig. 7 shows a diagram of the device according to the invention integrated with a watch clasp;

[0063] Fig. 8 shows a diagram of connections of the electronic system elements of the device according to the invention in a wireless charging variant;

[0064] Fig. 9 shows a diagram of the device according to the invention integrated with a watch clasp with flexible electrodes;

[0065] Fig. 10 shows a diagram of the device according to the invention integrated with a watch clasp with many flexible electrodes;

[0066] Fig. 11 shows a diagram of the device according to the invention integrated with a wristwatch with flexible electrodes;

[0067] Fig. 12 shows another diagram of the device according to the invention integrated with a wristwatch with flexible electrodes;

[0068] Fig. 13 shows a diagram of connections of the electronic system elements of the device according to the invention in a wired (contact) charging variant;

[0069] Fig. 14 shows a diagram of the device according to the invention integrated with a watch strap with flexible electrodes.

[0070] The general structure and principle of operation of the device according to the invention is shown in Fig. 1. The device for determining deep temperature according to the invention is generally indicated by the reference numeral 1 and in Figure 1 has the form of a composite measuring module containing a number of components surrounded by a dashed line. Said components include a module 3 for measuring skin surface temperature and heat flux, which can be made as a module enabling single-channel (SHF - Single Heat Flux) or two-channel (DHF - Dual Heat Flux) or multi-channel (MHF - Multi Heat Flux) measurement of skin surface temperature and heat flux flowing between tissues and the environment; a module 2 for estimating blood perfusion enabling estimation of blood perfusion flowing throughout the limb segment on which the measurement is carried out, consisting e.g. in measuring changes over time in the electrical impedance of the body segment being the object of the measurement and determining perfusion on this basis, or using another measurement method, including direct measurement of blood perfusion flowing throughout the entire limb segment. In the further part of the description, the module 2 for estimating blood perfusion in the entire limb segment will also be referred to in short as the measuring module 2. The device according to the invention further comprises a circuit 4a for pre-processing and / or analog-to-digital conversion (A / D) of signals recorded by the module 3 for measuring skin surface temperature and heat flux (hereinafter also referred to in short as the measuring module 3); a circuit 4b for pre-processing and / or analog-to-digital conversion (A / D) of signals recorded by the module 2 for estimating blood perfusion in the entire limb segment; and a central unit 5 constituting a microcontroller or microprocessor system (uC) together with electronic auxiliary systems necessary for its proper operation (e.g. power supply systems, external memory, clocking systems, etc.). The device 1 further comprises a communication circuit 6 connected to the central unit 5, enabling communication and data transmission, e.g. wired or wireless, between the central unit 5 and the external device 8. The central unit 5 is responsible for recording digital signals generated by the aforementioned modules 4a and 4b. One or more electronic components constituting the implementation of the above-mentioned elements 2, 3, 4a, 4b, 5 and 6 may be integrated into one electronic module (e.g. assembled on one printed circuit board) or one integrated circuit, the functionality of which will be equivalent to the functionality of one or more elements 2, 3, 4a, 4b, 5 and 6. Such an integrated electronic module of elements 4a, 4b, 5 and 6 is marked in Fig. 1 with the reference numeral 20. The central unit 5 can be used in one of two intermediate variants. In the first variant, the central unit 5 transmits unprocessed or partially processed data to the external device 8 connected to it (e.g. a mobile device such as a smartphone) in order to determine the values of intermediate parameters such as e.g. blood perfusion estimate in the body segment and determine the CBT temperature. In the second variant, the entire process of signal processing and determination of CBT temperature takes place in the central unit 5, and only the CBT measurement result is sent to the external device 8 upon request. In the intermediate variants, part of the data analysis is carried out in the central unit 5, and part on the cooperating external device 8. The central unit 5 is also responsible for collecting and storing the values of intermediate measurements (unprocessed data from circuits 4a and 4b) or the final CBT measurement value in the event of loss of communication with the external device 8. However, it should be noted that the external device 8 is not absolutely necessary for the functioning of the device 1 according to the invention, i.e. the central unit 5 is capable of independent operation in order to determine the CBT temperature based on the signals read from the modules 2, 3, however, the external device 8 may be helpful for reading the determined CBT values and / or further data processing.

[0071] The device 1 is intended for use with any device or jewelry element worn on the limbs, and in particular on the wrist (in particular, these may be watches, smartwatches, smart bands, straps, bands, bracelets, clasps, strap fasteners and other similar elements). All such carriers that enable the device elements to be maintained (e.g. by embedding, gluing, screwing, attaching, etc. to the carriers) (in particular modules 2, 3 and other electronic elements) on or within the limb and their proper functioning, are also referred to in this application and claims as the "support element" of the device. The support element is not limited to the examples presented above and may have an equivalent form, provided that it fulfills the above-mentioned function. Moreover, the support element may consist of more than one part, for example, some device elements may be placed, for example, in a watch strap, and others in a clasp or the body of a watch worn on the wrist - in this case, the strap, watch and clasp constitute a multi-part support element of the device. The support element may also be referred to as a carrier component, carrier, etc.

[0072] The device 1 automatically performs measurements. Communication with an external device 8, such as a portable device (e.g. a smartphone) or any other device capable of communicating with the device 1 and processing data (tablet, laptop, PC, etc.), can be carried out using wireless or wired communication.

[0073] Although this is not shown in Fig. 1 , the device 1 according to the invention may optionally be equipped with additional sensors, such as e.g. inertial sensors (accelerometer and / or gyroscope) enabling assessment of physical activity; sensors enabling measurement of heart rate, including e.g. ECG, PPG sensors, or sensors enabling measurement of blood perfusion in the skin located at the measurement site, e.g. using PPG sensors. In such variants, additional sensors would be placed in the support element in accordance with their intended use and connected to the central unit 5, so that it is possible to take into account the measurements provided by them when determining the CBT temperature or other important parameters. However, the aforementioned additional sensors are not necessary to ensure the basic functionality of the invention, i.e. determining the CBT temperature.

[0074] The measuring modules 2 and 3 containing sensors enabling, respectively, determining blood perfusion in the limb segment and measuring the temperature of the surface of this limb segment and measuring the density of heat fluxes flowing between the limb segment of the body and the environment are key to obtaining the assumed functionality of the device 1.

[0075] The measuring module 2 may be implemented in the form of, for example, an impedance rheograph, i.e. a device measuring changes over time in the electrical impedance of tissues constituting a selected segment of the body limb (e.g. wrist) constituting the measurement site. Measurement using this method requires the application of electrodes (two in the bipolar variant or four in the tetrapolar variant) to the body limb segment. In such an implementation, the aforementioned electrodes are components of the measuring module 2 and are placed so that the tested body limb segment is located between them, e.g. at its opposite ends. Then, an alternating current with a known amplitude and time course (e.g. frequency in the case of sinusoidal excitation) is forced through the application electrodes, and changes in voltage between the measuring electrodes are measured. In the case of using the bipolar method, the measuring and application electrodes are the same electrodes. In the case of the impedance method, the module 2 consists of an electronic system containing control and measuring elements, which system may constitute an integrated circuit (e.g. MAX30002 from Analog Devices or AFE4500 from Texas Instruments or similar) together with systems enabling the determination of the blood perfusion estimate based on changes in the electrical impedance of the body segment (the method of determining this value is described in detail in further part of the description) and two or four electrodes. The electrodes may be permanently connected to the module 2 or may be attached to it via wires. The electrodes may also be mounted in rigid structural elements of the support element, e.g. in the housing of a watch worn on the wrist or a clasp of a strap fastener, or constitute flexible elements located outside these elements. The above variants are described in more detail in the implementation examples presented in further part of the description. The impedance measurement can also be multi-electrode, i.e. the impedance is measured using different pairs or fours of electrodes, and the final result of perfusion estimation is a previously determined combination of individual measurements, e.g. a weighted average. This will be explained in more detail with reference to Fig. 6 in further part below.

[0076] It should be noted that the essence of the present invention is to include information about the value of blood perfusion in the body limb segment where the measurement is taken (e.g. wrist). The method of measuring this parameter is not limited to one specific method, e.g. impedance rheography, and can be implemented in many other ways. In another exemplary implementation, the measuring module 2 may be implemented in the form of a plethysmographic module measuring changes in the volume of the body segment as a result of heart activity by recording changes in pressure or volume of liquid or gas filling the cuff surrounding the tested body limb segment. For this purpose, the plethysmographic module acting as the measuring module 2 includes an inextensible cuff filled with gas and a pressure sensor in the cuff. At the beginning of the measurement, the cuff (simultaneously performing the function of a support element) is filled with gas so that it tightly adheres to the body segment constituting the measurement site. Then, changes in the volume of the body segment resulting from an increase in the volume of blood in the body segment as a result of heart activity are estimated by measuring changes in pressure in the cuff. In the next step, an estimate of the perfusion value is determined based on the recorded pressure changes. This can be implemented, for example, by a dedicated electronic system integrated with the pressure sensor placed in the cuff or connected to the pressure sensor placed in the cuff and embedded within the cuff. Alternatively, the recorded pressure changes can be transmitted from the pressure sensor (directly or via circuit 4b) to the central unit 5, which determines the perfusion values in the entire limb segment based on them. Appropriate processing can also be carried out by an external device 8 connected by communication with the central unit 5. The cuff may constitute a support element of the entire device according to the invention or be a component thereof.

[0077] In yet another exemplary implementation, the measuring module 2 may be implemented in the form of a module for measuring the flow velocity of blood flowing through the tested body limb segment using an ultrasonic measuring device enabling perfusion measurement using the dynamic tissue perfusion measurement method (DTP - Dynamic Tissue Perfusion Measurement). For this purpose, an ultrasonic probe (e.g. embedded in a support element attached to the limb) connected to a miniaturized ultrasound machine enabling imaging of the cross-section of the body segment being the object of the measurement in color Doppler mode is placed at the measurement site. Then, the average flow velocity in the cross-section and the value of the cross-sectional area are determined. The value of the average blood flow rate (expressed, for example, in ml / s) can be determined as the quotient of both values. Ultimately, the perfusion value (expressed, for example, in ml / (s * m3)) can be determined as the quotient of the average blood flow rate and the measurement volume determined as, for example, the product of the cross-sectional area of the imaged segment and its length (cylinder approximation). This can be implemented, for example, by a dedicated electronic system integrated with a matrix of piezoelectric transducers (constituting the ultrasonic probe) placed in the support structure of the device in a manner enabling the probe to adhere to the skin. Then, the determined perfusion values are transmitted directly or via the circuit 4b to the central unit 5 in order to determine the CBT value. Alternatively, unprocessed signals recorded by the ultrasonic probe may be transmitted after analog-to-digital conversion carried out in the circuit 4b to the central unit 5 in order to transmit them using the communication circuit 6 to the external device 8 for their analysis and determination of perfusion values.

[0078] It will be obvious to a person skilled in the art that the alternative implementations of the measuring module 2 described above can be used interchangeably, and for this purpose it is only necessary to make appropriate adaptations in the device according to the invention. In other words, as the measuring module 2, it is possible to use a measuring module of any suitable design that enables the measurement of parameters allowing for estimation of blood perfusion flowing throughout the body limb segment.

[0079] An exemplary structure of the module 3 for measuring skin surface temperature and heat flux in a single-channel and two-channel version is shown in Figures 2 to 5. The single-channel module shown in Fig. 2 includes a housing 3f filled with a thermal insulator 3e (in a particular case, it may be air or styrofoam or an aerogel) and temperature 3 a and heat flux 3b sensors placed on a PCB located at the housing wall 3f of the module, which will have direct contact with the skin (in the presented case, it is the bottom wall). Above the sensors 3a and 3b there is an element 3i (e.g. in the form of a disc made of aluminum or copper) of known thermal conductivity, through which heat flux flows, transferring energy between the body and the environment. Depending on the temperature or heat flux sensor used, the output signals of the module 3 may take the form of voltage values (analog sensors) or signals encoded in digital form (integrated digital sensor). Moreover, the reference numeral 3g in Figure 2 (and analogously in the following figures 3 - 5 described below) denotes a printed circuit board (PCB) constituting a mechanical and electrical element of the structure enabling mechanical connection of temperature and heat flux sensors with the remaining structural elements and ensuring electrical connection with the remaining electronic systems.

[0080] Another variant of the single-channel module, shown in Fig. 3, differs from the module shown in Fig. 2 in that the heat flux sensor 3b from Fig. 2 is replaced by a second temperature sensor 3 a, with both sensors 3 a being separated by an element made of a thermally conductive material 3i. In this variant, the heat flux can be estimated by determining the temperature difference between the two temperature sensors 3a used and taking into account the thermal conductivity of the element 3i.

[0081] Fig. 4 shows the module 3 in a two-channel version. In this variant, the module 3 consists of two channels with a structure according to the structure of the single-channel sensor shown in Fig. 2, with the difference that the elements 3c and 3d used in each of the channels have different thermal conductivity. For example, the thermal conductivity of element 3c is lower than the thermal conductivity of element 3d. Additionally, such a module may optionally includean element 3h constituting a thermal bridge made of a material with high thermal conductivity (in the form of, for example, a metal sheet, such as a copper sheet, aluminum, etc.) equalizing the boundary temperatures in both channels. The use of a two-channel version, known in the literature as Dual Heat Flux (DHF), allows to limit the influence of the thermal properties of tissues on the result of CBT estimation. The influence of this factor is the main limitation of CBT measuring devices with one channel, forcing the use of these sensors in places where the variability of this parameter in the population is small, e.g. the forehead.

[0082] Fig. 5 shows the module 3 in a two-channel version. In this variant, the module 3 includes two channels with a structure according to the structure of the single -channel sensor shown in Fig. 3, with the difference that the thermal resistance elements 3c and 3d used in each of the channels have different thermal resistance. For example, the thermal resistance of element 3c is greater than the thermal resistance of element 3d. Additionally, such a module may optionally include an element 3h constituting a thermal short made of a material with high thermal conductivity (in the form of, for example, a metal sheet, such as a copper sheet, aluminum, etc.) equalizing the boundary temperatures in both channels. It should also be pointed out that, depending on the context, the terms "thermal conductivity" and "thermal resistance" are used interchangeably in this description, and it will be understood by a person skilled in the art that thermal conductivity is the inverse of thermal resistance. Moreover, although this is not shown in a separate illustration, combinations of systems with double temperature sensors and with a temperature and heat flux sensor are also possible, creating measuring modules with two or more channels, such as, for example, modules containing in one housing one or more sensors shown in Fig. 2 and one or more sensors shown in Fig. 3.

[0083] Referring again to Fig. 1, the diagram shows a circuit 4a for pre-processing and / or A / D conversion of signals recorded by the module 3 for measuring skin surface temperature and heat flux, and a circuit 4b for pre-processing and / or A / D conversion of signals recorded by the module 2 for estimating blood perfusion, which are connected between, respectively, modules 3, 2 and the central unit 5. The task of circuits 4a and 4b is to appropriately prepare the signals provided by modules 3 and 2 so that they can be used to determine the CBT temperature in the central unit 5 and / or the connected external device 8. The term pre-processing should be understood as, for example, filtering and amplification, while the term analog-to-digital conversion should be understood as the conversion of analog signals into digital signals with the required time and amplitude resolution. The output of circuits 4a and 4b provides, for example, sequences of digital values representing changes over time in the measured values, i.e. temperatures, heat flux, and electrical impedance or perfusion values in the entire limb segment. Depending on the specific configuration, circuits 4a, 4b may only perform pre-processing or only analog-to-digital conversion, or both of the aforementioned functions simultaneously.

[0084] In an exemplary implementation, circuits 4a, 4b have the form of integrated electronic systems containing amplifier systems, analog and digital filters, and analog-to-digital converters.

[0085] Moreover, although the pre-processing and / or A / D conversion circuits 4a and 4b are shown in Fig. 1 as separate elements, the functionality of the circuit 4a and / or the circuit 4b may be included directly in the central unit 5 (e.g. by integration in the central unit 5), i.e. in this case, the outputs of the measuring modules 2 and 3 are fed directly to the inputs of the central unit 5, which independently performs the relevant pre-processing and conversion to digital form. It is also possible to include the functionality of the circuit 4a directly in the module 3 and / or include the functionality of the circuit 4b directly in the measuring module 2, for example, by integrating them into one system (e.g. MAX30002 from Analog Devices or AFE4500 from Texas Instruments), i.e. in this case, digital values are fed directly from the outputs of the measuring modules 2 and 3 to the inputs of the central unit 5. Other combinations enabling the implementation of measuring paths in order to provide measurement values prepared for further processing, i.e. determining the CBT temperature based on them, will also be obvious to a person skilled in the art. It is also conceivable for a person skilled in the art to implement the invention entirely based on analog systems and elements, in which case the A / D conversion stage and the system elements necessary for this purpose are omitted.

[0086] Fig. 6 shows a diagram of the steps of the method for determining CBT temperature according to the invention. The method of determining CBT temperature includes successive steps SI - S6 aimed at recording and processing measurement signals and additional information in order to obtain an estimate of the CBT temperature value. In step SI, estimates of the value of blood perfusion flowing throughout the limb segment are determined. For this purpose, in the implementation example shown in Fig. 6, step SI includes two sub-steps Sla and Sib. In this variant, in step Sla, the values of changes in electrical impedance as a function of time Z(t) of tissues forming the limb segment (e.g. wrist) are recorded. The measurement of changes in impedance Z(t) of the body segment can be carried out continuously or intermittently on demand or in another manner resulting from the method of estimating the blood perfusion value used in further steps. Step Sla can be implemented by the measuring module 2 equipped with a previously determined number of electrodes, e.g. 2 or 4, applied to the skin of the limb segment, as described earlier in reference to Figure 1 and in the implementation examples discussed in further part of the description, or a module of a different configuration allowing to measure the electrical impedance of the entire limb segment. The values of changes in impedance Z(t) of tissues forming the body limb segment on which the measurement is taken (e.g. wrist), recorded by the measuring module 2 in step S la, are then processed in step Sib into estimates of changes over time in blood perfusion (Wb(t)) flowing throughout the entire limb segment, and optionally into estimates of other physiological parameters such as e.g. heart rate (HR) or changes in skin conductivity (skin- galvanic reaction). The estimate of the HR value can be determined, for example, by analyzing the periodicity of changes in Z(t), and the assessment of the skin-galvanic reaction can be determined by measuring resistance. In the case of using the impedance rheography method, the estimate of the average blood perfusion value flowing through the body segment in a given time interval can be determined as the quotient of the average blood flow rate and the volume of the body segment being the object of the measurement. The average flow rate value is determined as the ratio of the peak-to-peak value of impedance changes to the square of its average value multiplied by the average HR value in the analyzed time interval and the value of the calibration coefficient. The value of the calibration coefficient depends, among other things, on the measurement location, anatomical conditions, resistivity values of individual tissues, and the distance between the electrodes. Typically, it is assumed that the value of the calibration coefficient can be estimated as the quotient of blood resistivity and the square of the distance between the electrodes. The value of this coefficient can also be determined analytically, including using numerical methods or statistical methods, including machine learning methods. In turn, the volume of the body segment can be determined as the quotient of the cross-sectional area (determined, for example, based on the circumference of this segment) and the length of the segment (determined, for example, based on the width of the measuring electrodes). However, in the device 1, the method of determining the estimate of the blood perfusion value is not limited only to this approach.

[0087] Although this is not shown in Fig. 6, other variants of determining blood perfusion (Wb(t)) flowing throughout the body limb segment in step SI are also possible. For this purpose, any suitable method can be used, such as the previously mentioned plethysmographic method or the ultrasonic flow measurement method, e.g. by using an appropriately adapted measuring module 2. In other words, in each of the variants, the result of carrying out step SI is the determined (e.g. directly measured or determined indirectly based on the processing of recorded values, e.g. electrical impedance values) blood perfusion flowing throughout the entire limb segment. Therefore, the invention is not limited to the exemplary implementation shown in Fig. 6.

[0088] In step S2, which is carried out simultaneously with step S 1 , the temperature values Temp(t) and heat flux HF(t) are recorded. For this purpose, a module 3 made according to any of the previously described variants, e.g. the variants shown in one of Figures 2 - 5, can be used. Then, in step S3 of the method, the signals Wb(t) and optionally HR(t) from step SI are pre-processed together with the temperature Temp(t) and heat flux HF(t) signals recorded in step S2. Preprocessing consists in particular in filtering the signals and, if necessary, their synchronization in time and resampling in order to obtain synchronous records with the same sampling frequency. Additional signals may be subjected to other processing methods or processes such as noise reduction, scaling, normalization, or anomaly detection. Then, all signals from step S3, i.e. in the basic variant, the temperature Temp(t), heat flux HF(t) signals, the value of blood perfusion Wb(t) in the body limb segment, as well as the optional biometric data provided simultaneously in step S5, containing in particular information about the radius R of the cross-section of the body limb segment on which the measurement is taken (and optionally also other user biometric data, such as the diameter or circumference of the body segment at the measurement site, age, gender, weight, lengths of individual body segments, etc.), and the optional data and signals provided simultaneously in step S6 (for example, blood perfusion in the skin at the measurement site, information about the currently performed activities, clothing worn, time of day, season, place of stay, e.g. room or open space, etc.) are transmitted to the CBT estimator implemented as step S4, which consists in determining the CBT value based on the signals and data described above. The estimator implementing step S4 of the method may have the form of an analytical (e.g. based on the Pennes model), statistical model or a mixture of both approaches. In particular, it may be a regression model obtained by applying machine learning methods (e.g. linear regression, support vector machine, random forest methods) or deep machine learning methods (e.g. deep neural networks) or similar methods, in particular methods based on aggregation or composition of estimation from many estimators (e.g. ensemble learning methods). Steps Sib, S3, S4, S5 and S6 can be implemented in the central unit 5 of the device 1 and / or in the external (e.g. mobile) device 8 cooperating with the device 1 or in the form of a server service, access to which is possible via a telecommunications network (e.g. the Internet).

[0089] As shown in Fig. 6, in step S4 of the method, the CBT estimator may also have access to additional sources (steps S5 and S6) of information, which may come from additional sensors integrated with the device 1 (described above) or constituting separate measuring devices. Additional data and / or information may also be prepared in advance, e.g. entered by the user or obtained via external services, e.g. Internet services, and for this purpose, for example, a mobile device having connectivity with the Internet service may be used. In particular, the aforementioned information may relate to:

[0090] 1. Anatomical or physiological characteristics of the user, such as e.g. height, weight, length of the limb on which the measurement is taken, age, gender, etc.

[0091] 2. Conditions in which the measurement is taken, e.g. ambient temperature, wind speed, weather conditions (rain, snow).

[0092] 3. Type and intensity of physical activity that the user is currently performing, e.g. walking, running, standing, sitting, lying down, sleeping, etc.

[0093] Advantageous forms of the device 1 according to the invention are presented in the following implementation examples described and explained in more detail in further part of this application.

[0094] First implementation example - device integrated with a watch strap clasp

[0095] Fig. 7 shows a diagram of an implementation example of the device according to the invention integrated with a support element in the form of a clasp lb of a watch strap 9. As shown in Figure 7, a watch 10 is placed on the user's wrist 7a (shown in cross-section in the figure), attached with a strap 9 equipped with a clasp lb, which in the presented example has the form of a butterfly clasp. The device according to the invention is built into the clasp lb and includes measuring electrodes 2c, a measuring module 3, and an integrated electronic module 21 containing, in the presented implementation, a measuring module 2, circuits 4a and 4b for pre-processing of measurement signals, central unit 5, battery 13, power supply system 12, wireless communication circuit 6, which for the sake of clarity are not shown separately in Figure 7 and will be described in further part of the description in reference to Fig. 8. In this implementation example, a two- channel measuring module 3 containing two temperature sensors and two heat flux density sensors (according to Fig. 4) is used, which is placed on the underside of the butterfly clasp facing the wrist 7a and has a shape adapted in such a way that after putting on the watch 10 and fastening the strap 9 on the user's wrist 7a with the butterfly clasp lb, said module 3 adheres with its entire working surface (the wall facing the wrist in the presented example) to the skin of the wrist 7a on the inside (palm side). The measuring electrodes 2c are built into rigid brackets protruding from the sides of the butterfly clasp lb and are connected to the measuring module contained in the integrated electronic module. The shape of the brackets is selected to obtain the adhesion of the electrodes 2c to the skin of the wrist, ensuring the greatest possible distance between the opposite electrodes 2c, while not limiting the comfort of use. In the discussed implementation variant, a configuration using tetrapolar current measurement (two application electrodes and two measuring electrodes) is used. For this reason, two electrodes, i.e. one application electrode and one measuring electrode on each side, are placed on both sides of the clasp lb, with the measuring electrodes being placed closer to the center of the clasp, and the application electrodes further from it.

[0096] The internal space of the clasp body lb, in which the aforementioned electronic module 21 of the device according to the invention is built-in, is tightly closed to protect the electronic components from the effects of moisture or the ingress of contaminants such as dust. Alternatively or additionally, the electronic module 21 of the device according to the invention itself may be watertight. The butterfly clasp lb can be freely opened and closed without affecting the structure of the electronic module 21 built into its body. After putting the watch 10 on the hand and fastening the butterfly clasp lb connected to the strap 9, the module 3 covering the surface of the butterfly clasp lb facing the user's body and the measuring electrodes 2c adhere with their entire surface to the palm side of the user's wrist 7a, thus enabling the recording of changes in the impedance values of tissues within the wrist 7a, temperature values and heat flux values flowing through the module 3.

[0097] In connection with Figures 1, 7, Fig. 8 shows a diagram of the connections of the individual elements of the electronic module 21 and the module 3 of the device according to the invention, corresponding to the configuration shown in Fig. 7. The diagram shows the previously mentioned elements of the device according to the invention: measuring module 2 connected to rigid measuring electrodes 2c (not shown in the diagram), circuits 4a and 4b for pre-processing of measurement signals or / and A / D conversion connected respectively to measuring modules 2 and 3, central unit 5 (in the form of an appropriately selected microcontroller equipped with memory) connected to circuits 4a and 4b and to communication circuit 6 (in this example, it is a wireless communication circuit in the Bluetooth standard), as well as power supply system 12, battery 13, inductive charging system 14, which are also included in the electronic module 21 of the device according to the invention. The power supply system 12 is connected to the battery 13, stabilizes the power supply and provides electrical power to the individual elements 2, 4a, 4b, 5 of the system. The inductive charging system 14 enables contactless charging of the battery 13 located in the device 1 from an external power source. The battery 13 is connected to the inductive charging system via a power supply stabilizing system 12, which controls the charging.

[0098] Referring to Figures 1 and 8, the measurement signals from the measuring modules 2 and 3 (two temperature signals, two heat flux signals and electrical impedance values), converted into digital values by means of circuits 4a, 4b and recorded by the central unit 5 (microcontroller), are then transmitted from the central unit 5, via the wireless communication circuit 6 (Bluetooth) connected to the central unit (microcontroller) 5 via the SPI interface, to the connected external portable device 8, e.g. a smartphone, in which the aforementioned measurement signals are used to estimate CBT (as explained, for example, in the description of Fig. 6). In the event of no connection with the external device 8, the data is saved in the memory of the central unit 5, and after the connection is re-established, it is transmitted to the external device 8. Alternatively, the CBT estimation takes place directly in the central unit 5, and the estimation result can be sent to the external device 8.

[0099] The advantage of this implementation example is that the clasps of watch straps and bracelets are the most universal parts in such products as watches or jewelry. With an extremely wide range of watches, straps and bracelet designs, clasps are offered in a small number of variants, differing primarily in color and the width of supported straps. For this reason, implementing the solution in this part gives the greatest possibilities of combining it with other, individually selected elements.

[0100] Second implementation example - device integrated with a watch strap clasp with flexible electrodes led out from the clasp

[0101] Figures 9 and 10 show a diagram of the device according to the invention integrated with a support element in the form of a clasp la of a watch strap 9. As shown in Figures 9 and 10, a watch 10 is placed on the user's wrist 7a (shown in cross-section in the figure), attached with a strap 9 equipped with a clasp la, which in the presented example has the form of a butterfly clasp. The device according to the invention is built into the clasp la and includes a measuring module 3, and an integrated electronic module 21 containing a measuring module 2, circuits 4a and 4b for preprocessing of measurement signals, central unit 5, battery 13, power supply system 12, wireless communication circuit 6, which for the sake of clarity are not shown in Figures 9 and 10. The measuring electrodes 2a are mounted on the inner part of the strap 9 acting as a support element and connected to the electronic module 21 (i.e. to the measuring module 2 integrated in the electronic module 21). In these implementation examples, a two-channel measuring module 3 containing two temperature sensors and two heat flux sensors (according to Fig. 4) is used, which is placed on the underside of the butterfly clasp facing the wrist 7a and has a shape adapted in such a way that after putting on the watch 10 and fastening the strap 9 on the user's wrist 7a with the butterfly clasp 1 a, said module 3 adheres with its entire working surface (the wall facing the wrist in the presented example) to the skin of the wrist 7a on the inside (palm side).

[0102] The main difference between this solution example shown in Figures 9 and 10 and the first solution example shown in Fig. 7 is the lack of embedding the electrodes 2a in the rigid body of the butterfly clasp la. Instead, the measuring electrodes 2a are implemented in the form of flexible strips made in the form of flexible printed circuits (FPC), which can be permanently or detachably connected to the electronic module 21 of the device (using FPC connectors). The electrodes 2a are led under the watch strap 9, which, when fastened, presses the electrodes 2a to the skin. The electrodes 2a can be implemented in a tetrapolar variant with two pairs of electrodes (Fig. 9) - similar to the implementation example from Fig. 7, or in a multi -electrode variant, in which there are many pairs of electrodes (4 pairs in Fig. 10) placed around the entire circumference of the wrist (Fig. 10). In the multi-electrode variant, the measuring module 2 is expanded by a multiplexer (not shown in the figures) enabling switching of the current generator outputs between different application electrodes and analogous switching of measuring electrodes. This approach enables many alternating measurements of wrist impedance 7a, and further estimation of many blood perfusion values in this limb segment. The final perfusion value can be determined, for example, as a weighted average. The advantage of this solution is less sensitivity to anatomical differences between individual users.

[0103] The internal space of the clasp body 1 a, in which the aforementioned electronic module 21 of the device according to the invention is built-in, is tightly closed to protect the electronic components from the effects of moisture or the ingress of contaminants such as dust. Alternatively or additionally, the electronic module 21 of the device according to the invention itself may be watertight. The butterfly clasp la can be freely opened and closed without affecting the structure of the electronic module built into its body. After putting the watch 10 on the hand and fastening the butterfly clasp la connected to the strap 9, the module 3 covering the surface of the butterfly clasp la facing the user's body and the electrodes 2a adhere with their entire surface to the user's wrist 7a, thus enabling the recording of changes in the impedance values of tissues within the wrist 7a, temperature values and values of heat fluxes flowing through the module 3.

[0104] In the case of the implementation examples shown in Figures 10 and 11, the connection diagram is analogous to that shown in Fig. 8. For the sake of clarity, the description of Figure 8 is not repeated here, and in this respect reference should be made to the explanations presented earlier.

[0105] The advantage of this implementation example is that the clasps of watch straps and bracelets are the most universal parts in such products as watches or jewelry. With an extremely wide range of watches, straps and bracelet designs, clasps are offered in a small number of variants, differing primarily in color and the width of supported straps. For this reason, implementing the solution in this part gives the greatest possibilities of combining it with other, individually selected elements. Replacing the electrodes rigidly mounted in the clasp body with flexible electrodes does not require increasing the size of the clasp, and therefore improves its usability and aesthetic features.

[0106] Third implementation example - device built into a wristwatch

[0107] Figures 11 and 12 show a diagram of the device according to the invention integrated with a support element in the form of a wristwatch 10a. As shown in Figures 11 and 12, a watch 10a is placed on the user's wrist 7a, attached with a strap 9 equipped with a clasp 11. The device according to the invention is built into the watch 10a and includes a measuring module 3 and an integrated electronic module 21 containing a measuring module 2, circuits 4a and 4b for pre-processing of measurement signals, central unit 5, battery 13, power supply system 12, wireless communication circuit 6, which for the sake of clarity are not shown in Figures 11 and 12. The measuring electrodes 2a are mounted on the inner part of the strap 9 acting as a support element and connected to the electronic module 21 (i.e. to the measuring module 2 integrated in the electronic module 21). In these implementation examples, a two-channel measuring module 3 containing two temperature sensors and two heat flux density sensors (according to Fig. 4) is used, which is placed on the underside of the watch 10a facing the wrist 7a and has a shape adapted in such a way that after putting on the watch 10a and fastening the strap 9 on the user's wrist 7a with the clasp 11, said module 3 adheres with its entire surface to the skin of the wrist 7a on the back side.

[0108] The measuring electrodes 2a are implemented in the form of flexible strips made in the form of flexible printed circuits (FPC), which can be permanently or detachably connected to the electronic module 21 of the device. The electrodes are led under the strap 9 from the watch 10a, which, when fastened, presses the electrodes 2a to the skin. The electrodes 2a can be implemented in a tetrapolar variant with two pairs of electrodes (Fig. 11 ) or in a multi-electrode variant, in which there are many pairs of electrodes (4 pairs in Fig. 12) placed around the entire circumference of the wrist 7a (Fig. 12). In the multi-electrode variant, the measuring module 2 is expanded by a multiplexer (not shown in the figures) enabling switching of the current generator outputs between different application electrodes and analogous switching of measuring electrodes. This approach enables many alternating measurements of wrist impedance 7a, and further estimation of blood perfusion values in this body limb segment. The final perfusion value can be determined, for example, as a weighted average. The advantage of this solution is less sensitivity to anatomical differences between individual users.

[0109] The internal space of the watch body 10a, in which the aforementioned electronic module 21 of the device according to the invention is built-in, is tightly closed to protect the electronic components from the effects of moisture or the ingress of contaminants such as dust. Alternatively or additionally, the electronic module 21 of the device according to the invention itself may be watertight. After putting the watch 10a on the hand and fastening the butterfly clasp 11 connected to the strap 9, the module 3 covering the surface of the watch body 10a facing the user's body adheres with its entire surface to the palm side of the user's wrist 7a, thus enabling the recording of changes in the impedance values of tissues within the wrist 7a, temperature values and values of heat fluxes flowing through the module 3.

[0110] Fig. 13 shows a diagram of the connections of the individual elements of the device according to the invention corresponding to the configurations shown in Figures 11 and 12. The diagram shown in Fig. 13 largely corresponds to the diagram from Fig. 8, therefore, reference should be made here to the relevant explanations presented earlier in reference to Fig. 8. For the sake of clarity, only the differences will be described. In contrast to Fig. 8, in the system in Fig. 13, instead of an inductive system, a charging system 15 is used, which enables charging the battery 13 (via the power supply system 12) through contacts located in the housing of the watch 10a.

[0111] Referring to Figures 1 and 13, the measurement signals from the measuring modules 2 and 3 (two temperature signals, two heat flux signals and electrical impedance values), converted into digital values by means of circuits 4a, 4b and recorded by the central unit 5 (microcontroller), are then transmitted from the central unit 5, via the wireless communication circuit 6 (Bluetooth) connected to the central unit (microcontroller) 5 via the SPI interface, to the connected external portable device 8, e.g. a smartphone, in which the aforementioned measurement signals are used to estimate CBT (as explained, for example, in the description of Fig. 6). In the event of no connection with the external device 8, the data is saved in the memory of the central unit 5, and after the connection is re-established, it is transmitted to the external device 8. Alternatively, the CBT estimation takes place directly in the central unit 5, and the estimation result can be sent to the external device 8.

[0112] The watch 10a indicated above may be, for example, an electronic watch of smartwatch type. These types of watches usually contain their own electronic components, such as a processing unit, memory, battery, or signal processing systems from built-in sensors. Therefore, configurations are possible in which the device according to the invention shares one or more components with such a watch (in other words, it uses the existing components without the need to add individual components). This type of integration can simplify the implementation of the device according to the invention in the discussed implementation example.

[0113] The advantage of this implementation example is that the system is built into an existing device that also performs other functions. Where such integration is possible, a significant reduction in the cost of implementing the system and method can be achieved. Sharing electronic resources and the battery further reduces the cost of implementing the solution.

[0114] Fourth implementation example - device built into a watch strap Fig. 14 shows a diagram of the device according to the invention integrated with a support element in the form of a strap 9a for a watch 10. As shown in Fig. 14, a watch 10 is placed on the user's wrist 7a, attached with a strap 9a equipped with a clasp 11. The device according to the invention is built into the strap 9a and includes measuring electrodes 2a, a measuring module 3, and an integrated electronic module 21 containing a measuring module 2, circuits 4a and 4b for pre-processing of measurement signals, central unit 5, battery 13, power supply system 12, wireless communication circuit 6, which for the sake of clarity are not shown in Fig. 14. In this implementation example, a two-channel measuring module 3 containing two temperature sensors and two heat flux sensors is used, which is sewn inside the strap 9a and has the form of a flexible or partially flexible electronic module (narrow rigid segments connected by flexible printed circuits) so that after putting on the watch 10 and fastening the strap 9a on the user's wrist 7a with the butterfly clasp 11 , said module 3 adheres with its entire working surface (facing the wrist in the presented example) to the skin of the wrist 7a.

[0115] The measuring electrodes 2a are implemented in the form of flexible strips made in the form of flexible printed circuits (FPC), which can be permanently or detachably connected to the electronic module 21 of the device. The electrodes are led under the strap 9a from the watch 10, which, when fastened, presses the electrodes 2a to the skin. The electrodes 2a can be implemented in a tetrapolar variant with two pairs of electrodes.

[0116] In the case of the implementation example shown in Fig. 14, the connection diagram is analogous to that shown in Fig. 8 or in Fig. 13. For the sake of clarity, the description of Figures 8 and 13 is not repeated here, and in this respect reference should be made to the explanations presented earlier.

[0117] The main benefit of simultaneously measuring blood perfusion in the body segment to which the sensor is applied and the size of this segment is to increase the accuracy of CBT measurement. An additional benefit may be the ability to simultaneously record a number of physiological parameters of the examined person, such as heart rate, degree of body hydration, tissue composition, blood oxygen saturation, blood perfusion, tissue impedance or skin-galvanic reaction. This set of data can be used to assess the well-being or burden on the body by various factors, including stress, physical activity, climatic conditions.

[0118] The increase in CBT measurement accuracy by using the structural solution described in this application has been verified analytically and by conducting an experiment using a DHF type CBT sensor prototype and a material model of the forearm.

[0119] The results of studies on temperature distribution in the human forearm published by Pennes in 1948 showed that this distribution depends on such factors as arterial blood temperature (Ta), blood perfusion (Wb), specific heat of blood (cb), heat flux generated in the metabolic processes of forearm tissues (Qmet), forearm diameter (R), thermal conductivity of tissues (kt), air temperature (Tamb) and heat transfer coefficient between the forearm and the environment (ha) (Pennes, 1948). The relationship between the distance from the center of the forearm (r) and the measured temperature can be expressed by the following formula (Pennes, 1948; Yue et al., 2004):

[0120] Where: Io, Ii are modified Bessel functions of the first kind of order 0 and 1, respectively.

[0121] Since arterial blood temperature measurement is one of the reference methods for CBT measurement, it can be assumed that estimating the temperature of blood flowing in the forearm will be the best estimate of CBT. Formula 8 can be transformed to allow Tato be determined as a function of the remaining parameters, i.e.: T(r), Tamb, Wb, Cb, R, kt, Qmet. In the case of measurement using SHF or DHF methods, the tissue temperature is measured on the surface, so for r=R. Cb can be considered as slightly changing in the population, and ktcan be partially estimated using the DHF method. The radius of the forearm can be obtained through a simple and one-time measurement. Ambient temperature Tamb and ha can also be estimated using the DHF method. Thus, two variables remain unknown: Wb (blood perfusion) and Qmet (tissue metabolism rate). In limb locations that are not very muscular or when the muscles are not active, the heat generated in metabolic processes is small compared to the heat supplied by the flowing blood, and therefore the lack of information about Wb is the main source of measurement error.

[0122] In order to confirm the above thesis, a material model of the forearm and a method of controlling the heat distribution inside it were developed, which allowed to reproduce the distribution and flow of heat in the model in accordance with the model developed by Pennes. A functional model of a DHF type CBT meter was also developed. Then, the daily changes in signals from CBT sensors were recorded for simulated 10 different people (the model parameters were drawn from distributions corresponding to the distributions measured in the healthy human population) at different ambient temperatures (Tamb changed linearly from 18°C to 25°C). Then, using the recorded signals (two temperature sensors and two heat flux density sensors) and additionally information about the radius of the model and the simulated perfusion value, the Ta value was estimated. Then, the estimated values were compared to the value assumed in the material model control algorithm. To estimate Ta, two regression models were developed:

[0123] 1. LR - linear regression,

[0124] 2. ANN - artificial neural network.

[0125] The following error measures were used:

[0126] 1. MAE - mean absolute error,

[0127] 2. STD - standard deviation of errors.

[0128] In the case of the LR model, the following error measure values were obtained:

[0129] 1. Using DHF measurement: MAE = 0.285°C and STD = 0.331°C

[0130] 2. Using DHF measurement extended by information about Wb and R: MAE = 0.06°C and STD = 0.091°C

[0131] In the case of the ANN model, the following error measure values were obtained:

[0132] 1. Using DHF measurement: MAE = 0.285°C and STD = 0.331°C

[0133] 2. Using DHF measurement extended by information about Wb and R: MAE = 0.054°C and STD = 0.059°C

[0134] The above results indicate that:

[0135] 1. The developed functional model of the DHF type CBT sensor shows a similar measurement accuracy to currently available commercial solutions.

[0136] 2. Blood perfusion measurement allows for an approximately 5 -fold reduction in CBT measurement error compared to the DHF method.

[0137] Although the examples presented in this application describe specific forms of implementation of the device and method according to the invention, it will be obvious to those skilled in the art that the invention is not limited to the details presented. For example, the communication between the central unit and the external device is not limited to the described Bluetooth communication and may take place using another wireless standard or by wire. Moreover, the variants of inductive and contact charging described in relation to specific configurations of the device according to the invention are not limited to the indicated configurations and can be used interchangeably as needed.

[0138] Moreover, depending on the requirements, the processing of data recorded by the sensor modules may take place in the central unit, in the connected external device, or partially in the central unit and partially in the connected external device. In other words, in the most basic configuration, it is possible to resign from communication with the external device and related systems and limit oneself to connecting the sensors directly to the central unit (e.g. in the form of an appropriately programmed microcontroller or other suitable dedicated system). This also applies to the aforementioned systems for pre-processing of measurement signals or / and A / D conversion, whose functions in the most basic configuration may also be taken over by the central unit.

Claims

Claims1. A device (1) for determining human core body temperature (CBT), intended to be placed on a limb segment of the body, characterized in that it comprises a. a module (2) for estimating perfusion of blood flowing throughout the entire limb segment; b. a module (3) for measuring skin surface temperature and heat flux; c. a central unit (5) connected to the module (2) for estimating blood perfusion flowing throughout the entire limb segment and to the module (3) for measuring skin surface temperature and heat flux, designed to determine human core body temperature (CBT) based on at least signals from the connected modules (2, 3); d. a support element for the components (2, 3, 5) of the device (1) mounted on said limb segment.

2. The device (1) according to claim 1, characterized in that the module (2) for estimating blood perfusion flowing throughout the entire limb segment is implemented as an impedance rheograph comprising at least one pair of electrodes (2a, 2c) applied to the limb segment, wherein the measurement signal of the electrical impedance of the entire limb segment provided by the impedance rheograph constitutes the basis for determining the estimate of blood perfusion flowing throughout the entire limb segment.

3. The device (1) according to claim 2, characterized in that the module (2) for estimating blood perfusion flowing throughout the limb segment of the body comprises two or more pairs of electrodes (2a, 2c), each pair comprising an application electrode and a measuring electrode, and a multiplexer for switching between successive pairs of electrodes (2a, 2c).

4. The device (1) according to claim 1, characterized in that the module (2) for estimating blood perfusion flowing throughout the entire limb segment is implemented as a plethysmographic module or an ultrasonic measuring device.

5. The device (1) according to claim 1, characterized in that the module (3) for measuring skin surface temperature and heat flux is a single-channel SHF (Single Heat Flux) module or a two-channel DHF (Dual Heat Flux) module or a multi-channel MHF (Multi Heat Flux) module.

6. The device (1) according to claim 5, characterized in that each channel of the SHF or DHF or MHF module comprises one temperature sensor (3 a) and one heat flux density sensor (3b) or two temperature sensors (3a) separated by an element (3i, 3c, 3d) made of a heat-conducting material.

7. The device (1) according to any of the preceding claims, characterized in that it further comprises a communication circuit (6), in particular a Bluetooth wireless communicationcircuit, connected to or integrated with the central unit (5), designed to transmit measurement data and / or the determined CBT temperature to an external device (8).

8. The device (1) according to any of the preceding claims, characterized in that it further comprises a circuit (4a) for pre-processing and / or analog-to-digital conversion (A / D), the input of which is connected to the output of the module (3) for measuring skin surface temperature and heat flux, and a circuit (4b) for pre-processing and / or analog-to-digital conversion (A / D), the input of which is connected to the output of the module (2) for estimating blood perfusion, wherein the outputs of the circuits (4a, 4b) are connected to the central unit (5).

9. The device (1) according to any of the preceding claims, characterized in that one or more of: the module (2) for estimating blood perfusion flowing throughout the limb segment, the module (3) for measuring skin surface temperature and heat flux, the circuits (4a, 4b) for pre-processing and / or analog-to-digital conversion, the central unit (5) and the communication circuit (6) are integrated into one electronic module (20, 21).

10. The device (1) according to any of the preceding claims, characterized in that it further comprises one or more additional sensors connected to the central unit (5), wherein one or more of the sensors include inertial sensors, in particular an accelerometer and / or a gyroscope, an ECG sensor, a PPG sensor or sensors for measuring blood perfusion in the skin at the measurement site, wherein the signals from one or more additional sensors are taken into account by the central unit (5) when determining the CBT temperature.

11. The device (1) according to any of claims 2 - 3 or 7 - 10, characterized in that the support element for the components (2, 3, 4a, 4b, 5, 6, 20, 21) of the device (1) is a clasp (la, lb), in particular a butterfly clasp, of a band (9), in particular a watch band, worn on the wrist (7a), wherein the measuring electrodes (2c) are built into rigid brackets protruding from the sides of the butterfly clasp (lb) or the measuring electrodes (2a) are mounted on an inner part of the band (9).

12. The device (1) according to any of claims 2 - 3 or 7 - 10, characterized in that the support element for the components (2, 3, 4a, 4b, 5, 6, 20, 21) of the device (1) is a band (9a) worn on the wrist (7a), in particular a watch band, wherein the measuring electrodes (2a) are mounted on an inner part of the band (9a).

13. The device (1) according to any of claims 2 - 3 or 7 - 10, characterized in that the support element for the components (2, 3, 4a, 4b, 5, 6, 20, 21) of the device (1) is a watch (10) worn on the wrist (7a), wherein the measuring electrodes (2a) are mounted on an inner part of the band (9) of the watch (10).

14. A method of determining human core body temperature, CBT, characterized by: a. determining (SI) estimates of the value over time of blood perfusion Wb(t) flowing throughout the entire limb segment;b. recording (S2) values of temperature Temp(t) and heat flux HF(t) on the skin of the tested limb segment; c. pre-processing (S3) the obtained values of temperature Temp(t), heat flux HF(t) and the estimates of the value over time of blood perfusion Wb(t); d. determining (S4) the CBT temperature based on at least the pre-processed values Temp(t), HF(t), Wb(t) using an estimator.

15. The method according to claim 14, characterized in that the estimates of the value over time of blood perfusion Wb(t) flowing throughout the limb segment of the body are determined (SI) by the rheography method by recording (SI a) the values of changes in impedance Z(t) of tissues forming the tested body segment using at least one pair of electrodes (2a, 2c) applied to the tested body segment of the body and processing (Sib) the recorded values of changes in impedance Z(t) into estimates of the value over time of blood perfusion Wb(t) flowing throughout the limb segment.

16. The method according to claim 14, characterized in that the estimates of the value over time of blood perfusion Wb(t) flowing throughout the limb segment are determined (SI) by a plethysmography method or an ultrasonic flow measurement method.

17. The method according to one of claims 14 - 16, characterized in that when determining (S5) the CBT temperature using an estimator, the size of the limb on which the measurement is taken is taken into account, in particular the radius of the limb cross-section at the measurement site.

18. The method according to claim 15, characterized in that the recorded values of impedance changes Z(t) are further processed into estimates of heart rate (HR) and / or changes in skin conductivity or / and tissue composition, in particular the proportion of water, fat, muscles in the total mass of the body segment, in the processing step (Sib), pre- processed in step (S3) together with other parameters and taken into account in the estimator in step (S4) of determining the CBT temperature.

19. The method according to one of claims 14 - 18, characterized in that when determining (S4) the CBT temperature, biometric data (S5) is taken into account, in particular the user's gender, weight, limb lengths, and / or optional data and signals (S6) are taken into account, in particular ambient temperature, wind speed, type and intensity of physical activity performed by the user.

20. The method according to one of claims 14 - 19, characterized in that the estimator implementing the step of determining (S4) the CBT temperature has the form of an analytical or statistical model or a mixture of both approaches, and in particular a regression model obtained by applying machine learning or deep machine learning methods.

Images