WO2010128852A2

WO2010128852A2 - Ear sensor system for noninvasive measurement of quantities

Info

Publication number: WO2010128852A2
Application number: PCT/NL2010/050256
Authority: WO
Inventors: Gerard Marie Griffioen
Original assignee: Agis Harmelen Holding B.V.
Priority date: 2009-05-07
Filing date: 2010-05-03
Publication date: 2010-11-11
Also published as: WO2010128852A3; NL2002852C2

Abstract

There is disclosed an ear sensor system comprising means that emit and receive electromagnetic (EM) radiation and a unit for processing signals from said means. Said means are designed to be provided each on one side of an ear crease present near the ear canal of a living being, through which blood passes. The processing unit is designed to determine absorption spectra of medical quantities being of relevance to said living being in a non-invasive manner on the basis of said signals. By carrying out optical measurements which are not objectionable to human and animal beings and utilising the results of absorption spectra of frequencies of radiation, relevant information about the aforesaid quantities will be available, continuously if desired.

Description

EAR SENSOR SYSTEM FOR NONINVASIVE MEASUREMENT OF QUANTITIES

The present invention relates to an ear sensor system.

Such ear sensor systems are generally known, they are generally used for measuring medical quantities, such as the temperature, for example, in the ear.

The object of the present invention is to extend the possibilities which the ear, and in particular the ear canal, offers for measuring medical quantities that are relevant for living beings in a reliable, non-invasive manner .

In order to accomplish that object, this system according to the invention comprises the features defined in claim 1.

The advantage of the system according to the invention is that by carrying out in vivo absorption measurements or, put differently, transmission measurements, using electromagnetic radiation, on blood which flows to a sufficient extent through an ear crease or ear canal, it is possible to obtain or derive information which is indicative of a number of medical quantities which are vital for living beings. Practical examples of such quantities are: heart rhythm, heartbeat, oxygen concentration, glucose content and/or (de) hydration. In particular the oxygen content, the glucose concentration, the cholesterol concentration and the moisture content in the blood previously needed to be determined in a manner which was objectionable both to humans and to animals, for example by damaging the skin or by drawing and examining blood, in some cases in a laboratory, with the results generally not being available until after some time. In some cases it was necessary to carry out indirect, and less reliable, measurements, such as flow, tension and impedance measurements, followed by complex calculations. In the case of diabetes patients, for example, the patients had to draw a little blood themselves and examine it, using an apparatus, and only then did the blood sugar concentration in the blood become available.

By carrying out optical measurements, which are not objectionable to humans and animals, according to the present method, and utilising the results of radiation absorption spectrum measurements carried out at several frequencies, if desired, which radiation is sufficiently absorbed by the substances to be measured in the blood through the ear crease, relevant information not obtained by using an invasive method about each of the aforesaid quantities will be available, continuously if desired.

Possible applications are further in the fields of patients in hospitals, nursing homes or old people's homes, geriatric care, mentally handicapped persons, home care, babies, cardiac patients, the aforesaid diabetics, military personnel and fire fighters, people with dangerous jobs and the like. The limited amount of equipment that is needed can be carried along without difficulty.

One embodiment of the system according to the invention is characterised in that the control unit by means of which the radiation power of the laser (diode) is influenced is designed for continuous operation or for discontinuous (pulsed) operation in an energy-saving manner. Control by means of variable laser control currents advantageously makes it possible to have one and the same laser deliver electromagnetic radiation at varying frequencies. Via the sensor means, which receive EM radiation that has passed through the blood in the ear crease, data become available, from which, after comparison of the absorption spectra at said varying frequencies, sufficiently reliable medical information can be derived. Further possible embodiments, which are defined in the other claims, and the associated advantages are described in detail in the description below.

The ear sensor system according to the present invention will now be explained in more detail with reference to the figures below, in which like parts are indicated by identical numerals. In the drawing: Figure 1 shows a human ear, which is provided around an ear crease with means according to the invention that emit and receive electromagnetic radiation; and

Figure 2 shows a possible embodiment of an ear sensor system which is provided with a processing unit for processing signals from the means in figure 1.

Figure 1 shows the ear of a living being, in this case a human being, in which part of an ear sensor system 1 is present, viz. means 2 and 3 emitting and receiving electromagnetic radiation, hereinafter called EM radiation, provided on either side of one or more ear lobes, skin or ear creases, hereinafter generally indicated at 4. Said means 2 and 3 may be combined, for example into a clip - a kind of clothes-peg - to be clamped to the ear crease, either above (4-1) or below (4-2) the mouth of the ear canal. In the former case, when measuring takes place at the upper crease 4-1, very reliable results are obtained, because said crease 4-1, unlike the crease 4-2, does not move along with the jaw but is fixed to the skull. In the latter case, slightly more optical power to be transferred via a suitable fibre line may be required in order to ensure that a detectable quantity remains at the other side of the lower ear crease 4-2. Measuring in particular takes place between concha and antihelix, generally resulting in a stable and regular measuring pattern.

The transmitting element 2, which comprises one or more lasers or laser diodes (Light Emitting Diodes, LEDs) on one side of the ear crease 4, sends the EM radiation through blood flowing in the ear lobe 4 to the other side, where the receiving (sensor) means 3 is provided. Lasers are, by nature, better capable of bundling light emitted by lasers, so that, unlike the situation in which LEDs are used, fewer if any measures are required for converging the EM light rays. The emitted radiation is absorbed by the blood and in particular by the components in the blood. It has been determined that said absorptions by the various components, such as moisture, glucose or oxygen, differ to such an extend that it becomes possible to carry out concentration measurements for said components.

The system 1 to that end comprises a processing unit 5 (schematically shown in figure 2) connected to the aforesaid means. The processing unit 5 is designed to determine, advantageously in a non-invasive manner, on the basis of said signals absorption spectra of medical quantities being of relevance to the aforesaid living being. Using known low-energy transmission and receiving means (not shown) , the signals received by the receiving means 3 are transmitted to the unit 5, where they will be used for determining, in a manner yet to be explained, the absorption spectra at different frequencies of the EM radiation. The system 1 comprises a control unit 6 connected to the EM radiation emitting means 2 for influencing the optical radiation power of said one or more lasers or laser diodes 2. The EM radiation may have a wide frequency spectrum, or be temporarily emitted at different, successive frequencies. In some cases one and the same laser 2 can be used for that purpose for producing radiation having different frequencies by emitting at different current levels or wave modes. At specified frequencies, absolute absorption values tell something about the absorptions effected by the specific substances in the blood, but in most cases the respective absorption at a certain frequency is determined by several substances simultaneously. It is advisable in those cases to compare absorption values at several different frequencies with each other so as to arrive at a reliable measure of the absorption of the relevant medical quantity.

The processing unit 5 of figure 2 comprises a programmable, processor-controlled CPU 7 connected to the control unit 6, which in this case digitally controls one or more amplifiers for the lasers 2. In said CPU 7, the signals received from the receiving means 3 are further processed. In practice the means 3 comprise several sensors, if necessary, which are each sensitive to radiation at (a) specific relevant frequency (frequencies) . In the illustrated case, received signals carrying information about oxygen content {SPO₂) _/ glucose concentration and moisture content (hydration), respectively, are supplied to a multiplexer 8-1, so that processing can take place practically simultaneously. After being supplied to a sensor amplifier 9-1, the signals are filtered by a filter, a digital filter 10-1 in this case, and made separately available, initially for possible analysis, to the CPU 7.

The processing unit 5 in this case also has a separate multiplexer 8-2, and connected thereto a sensor amplifier 9-2 and a filter 10-2 for measuring the temperature, in particular the difference temperature, at different depths in the ear canal by means of temperature sensors 2 and transmitting said temperature to the CPU 7. Preferably, several infrared sensors are used for carrying out the temperature measurements.

Using a motion sensor or G-sensor 2, information regarding the movements or accelerations or decelerations of the human or animal being is supplied to the CPU 7. If said movements are considered to be objectionable and exceed a specified level, the quantities determined during said period can be regarded as - temporarily - unreliable. It has been found that at frequencies around 1550 nm the difference in absorption between haemoglobin and water is significant enough for carrying out reliable hydration measurements at optical power levels which, for safety reasons, are acceptable and which, for energy reasons, are as low as possible. Accuracy levels of tenths of percents have been found to be achievable in practice. Measuring through tissue without impediment was found to be possible at 1200 nm, whilst the absorption by haemoglobin is very low and the absorption by water is rather high at that wavelength. Eventually, it was decided to use combined hydration measurements both at 810 nm and at 1200 nm in one possible variant, because the respective courses of the absorptions by water at said wavelengths, given different optical power levels, as a function of the water concentration are comparable. Reliable information concerning the moisture balance are important for example for older people, (endurance) sports people, and more generally in situations where heavy physical labour is carried out or in which a great deal of moisture is evaporated. Relevant information can be directly transmitted to a central location or to a satellite, possibly together with other information.

Measurement of the oxygen content (SPO2} in the blood appears to be readily possible at frequencies which alternate between 650 nm and 810 nm. Colour changes connected to the oxygen concentration in the blood can thus be determined more accurately, whilst said measurements appear not to be adversely affected by absorption of water in the blood. Measurement at 1200 nm, however, is also quite suitable for said oxygen measurements.

The heart rhythm and the heartbeat can be recognized in the increase and decrease of the blood volume passing through the crease 4, resulting in an absorption which regularly varies in height. Similarly, the breathing pattern is recognizable. The viscosity of the passing blood can be determined by sending the radiation to the passing blood at a certain angle. Based on the Doppler effect, it is possible to derive from the radiation that returns, or is optically broken, or passes through the blood, the current decelerations and accelerations of the blood. From said current information the viscosity of the blood can subsequently be derived.

The substances glucose and cholesterol in the blood also have their characteristic absorption and transmission properties at certain frequency values. It has been found to be advantageous to have the laser frequency "sweep" through a specific frequency range for determining the concentrations of said substances. Insofar as the relevant blood absorption or transmission data are included in and/or are only weakly contained in the measured signals, static averaging techniques can be used for digging up the aforesaid data so as to subsequently be able to correctly interpret said data as reliable parameters for the desired medical quantities to be measured. Preferably, 3500 nm is used for glucose measurements.

Similarly, Cortisol, ketone and lactate concentrations are determined at the aforesaid frequencies, so that data regarding stress, overtraining and performance level, respectively, will be continuously available.

Examples of ketone bodies are: beta hydroxybutyrate, L. acetoacetate and L. acetone. Information of this kind is very important to know for sports people, for example, or in the case of prolonged physical exertion. It is furthermore possible to optically determine the average blood pressure value from the extent to which the absorption level jumps back and forth with the blood pressure.

Claims

1. An ear sensor system comprising means that emit and receive electromagnetic (EM) radiation and a unit for processing signals from said means, said means being designed to be provided each on one side of an ear crease present near the ear canal of a living being, through which blood passes, and said processing unit being designed to determine absorption spectra of medical quantities being of relevance to said living being in a non-invasive manner on the basis of said signals.

2. A system according to claim 1, characterised in that said medical quantities include heart rhythm, heartbeat, respiration, and concentrations in the blood of oxygen, glucose, Cortisol, ketones, lactate, cholesterol, moisture and/or viscosity values.

3. A system according to claim 1 or 2, characterised in that said EM radiation emitting means comprise at least one laser or laser diode (LED) .

4. A system according to any one of claims 1-3, characterised in that the system comprises a control unit connected to the EM radiation emitting means, which control unit functions to influence the optical radiation power.

5. A system according to claims 3 and 4, characterised in that said control unit is designed to have said at least one laser or laser diode operate continuously or discontinuously, or at one or more different frequencies.

6. A system according to claim 5, characterised in that the wavelength of the EM radiation ranges between 600 nm and 3500 nm.

7. A system according to claim 6, characterised in that EM radiation having a wavelength of 650 nm, 810 ran, 1200 nm, 1550 nm, 3500 nm is used.

8. A system according to any one of claims 1-7, characterised in that the system comprises a motion sensor for determining movements of the living being which interfere with an accurate determination of said quantities .

9. A system according to any one of claims 1-8, characterised in that the processing unit comprises a multiplexer connected to the means that receive EM radiation for simultaneous processing of the signals received from the receiving means.

10. A system according to claim 9, characterised in that the processing unit comprises filter means connected to the multiplexer for filtering out respective frequencies of the signals on the basis of which the absorption spectra for the medical quantities are determined.

11. A system according to any one of claims 1-10, characterised in that the system comprises one or more temperature sensors for determining the temperature or the changes in the temperature of the living being.

12. A system according to claim 11, characterised in that said temperature sensors measure the temperature or the difference temperature at different depths in the ear canal.

13. A system according to any one of claims 1-12, characterised in that the system comprises transmission and receiving means wirelessly or non-wirelessly coupled to a central transceiver, which transmission and receiving means are connected to the processing unit.

14. Means emitting and receiving electromagnetic (EM) radiation, which are to be provided in the ear, each on one side of an ear crease in the ear canal, through which blood flows, and a transmitter connected thereto for transmitting obtained information to a central receiver which is designed for determining absorption spectra of medical quantities being of relevance to said living being in a non-invasive manner on the basis of said information.

15. Use of the obtained information and the signals, respectively, from one of the preceding claims for noninvasive determination of medical quantities in the blood, such as: oxygen content and glucose, Cortisol, ketone and lactate concentrations, viscosity and/or (de) hydration, whether or not on the basis of the relation between absorption values at several different frequencies.