WO2006089763A1

WO2006089763A1 - Measuring device

Info

Publication number: WO2006089763A1
Application number: PCT/EP2006/001703
Authority: WO
Inventors: Johannes P. Buschmann
Original assignee: Buschmann Johannes P
Priority date: 2005-02-25
Filing date: 2006-02-24
Publication date: 2006-08-31
Also published as: EP1855583A1

Abstract

The invention relates to a method and a device for transmission pulsoximetry through the wrist or forearm, which can even be used on adults.

Description

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I. Field of application

The invention relates to a method and a measuring device in order to measure the absorption of light by living, irradiated by the light, tissue in humans or animals.

II. Technical background

For the purposes of the present application, "light" is understood as meaning electromagnetic radiation in the range from 400 nm to 2000 nm, in particular in the range between 600 nm and 1000 nm.

Furthermore, for the purpose of the present application, "absorption" is understood to mean the light intensity which can be measured after passing through the tissue on the sensor, irrespective of whether the incident light intensity or electrical power was known or not and regardless of whether the layer thickness of the irradiated one was irradiated Tissue b was known or not.

In tissue photometry, as is known, the absorption of certain frequency components (eg 0 to 0.3 Hz and 0.5 to 10 Hz) is determined, which is related to the pulse rate or respiratory rate of the organism to be examined. The light flux in the tissue is due in particular to various optical effects such as scattering, absorption, diffraction, inter alia, at interfaces between the different constituents of the living tissue, the "transmission" and "reflection" being simplifying terms referring to a behavior of the Relate light relative to transmitter and receiver.

Thus, in optical plethysmography, the absorption in the frequency range of the arterial pulsation, ie from about 30 to 240 bpm, corresponding to 0.5 to 4 Hz is considered in relation to non-pulsatile absorption, ie absorption in the frequency range below 0.4 Hz This can be used to determine pulse rate and respiratory rate.

If an optical plethysmography is performed in two or more spectral ranges and their depths of migra- tion (pulsatile part AC to non-pulsatile part DC) z. B. at 730 nm and 990 nm in relation to each other, it follows from the respective modulation depths a variable

which is in many areas independent of influencing factors such as layer thickness of the irradiated tissue, etc., and with whose help the arterial oxygen saturation can be determined, possibly also the venous oxygen saturation.

With the help of this so-called pulse oximetry, the heart rate and lung function can thus be monitored in a wide range.

In the recent past, pulsoximetry, especially in the form of transmission pulse oximetry, has been very successful in medicine, in living tissue up to a layer thickness of about 20 mm with light from 400 nm to 4000 was irradiated nm length and the light absorbed by the tissue light component was measured.

Due to the limited thickness of the tissue to be irradiated, the application sites were severely restricted: in adult humans, for example, on single fingers or earlobes, in premature births or newborns just a hand or a foot.

The intracutaneous transmission pulse oximetry in fetuses, especially for monitoring the oxygen supply during childbirth, is already known (DE 38 10 008).

In the course of mobile diagnostics, it has also been attempted to carry out the transmission pulse oximetry with the help of specially designed sensor units so that the non-hospitalized user is not hindered in his everyday activities or professional activities and reliable evaluation results are obtained in spite of movement and attractive design of the sensor. in order to monitor people in the performance of activities or at their performance limits, but also in the REHA, wellness and fitness area.

Although it was clear that this requires adjustments both in designing the sensor unit and in the evaluation of the signals, it has not been possible in practice to produce sensors which can be used satisfactorily for monitoring mobile patients, in spite of attempts to connect the sensors, for example , B. to integrate in a ring and transmit the data to an evaluation unit on the wrist or the like.

In order to overcome the disadvantageous limitation with respect to the layer thickness, the reflex pulse oximetry was used in which, in contrast to the transmission pulse oximetry light emitter and light receiver were not arranged on opposite sides of the tissue to be irradiated, but on the same side and side by side, usually in a distance of only a few mm. The serious disadvantage of this method, however, is the so-called shunt light, which is understood to mean those portions of light that can pass from the emitter to the sensor, without radiating the desired tissue, in particular the part of the tissue penetrated by arterioles.

These include, for example, those light components which are only influenced by the superficial, less perfused skin layers and in this way reach from the light emitter to the light sensor.

This shunt light component has such a negative impact on the overall result that the responsible application of this method is generally called into question today.

Hl. Presentation of the invention

a) Technical task

It is therefore the object of the invention to provide a method and a device for the absorption of light by living tissue, which provides satisfactory results even when used by a mobile, non-hospitalized user without the user in his activities hinder.

b) Solution of the task

This object is solved by the features of claims 1 and 35. Advantageous embodiments emerge from the subclaims.

Contrary to the opinion that has existed for many years, according to which the irradiation of living tissue with light only up to tissue thicknesses of 15 or 20 mm is possible, it has been found according to the invention that the penetration of substantially thicker body parts such as the forearm or wrist is possible:

The maximum permissible heating of the user's fabric at the point at which the light emitter produces heat to at most 43 ^° C. and only for a very short time, in connection with this, is the power loss and thus the efficiency of the light emitter the other hand, a still sufficiently large distance of the useful signal from the noise, which is getting smaller with the size of the sensor surface.

This compromise search has shown that useful results are achieved if the photocurrent achieved at the light sensor, caused by the radiation from the light emitter and thus through the tissue, is at least 0.01 μA to 0.1 μA and / or or the light output is at least 60 nW.

This satisfactory measurement results are achieved, for. B. with a pulse duration of 15 microseconds and a pause between the individual irradiation pulses of 485 microseconds, without causing the heating of the tissue around the light emitter or around is too strong. However, the heating of the fabric can be additionally kept low by forming those parts which are in thermal contact with the light emitters and lie on the side facing away from the user side of the light emitter, as a heat sink, ie as components that have a large heat capacity and on which transfers the heat faster than the user's skin.

This can be further minimized by causing a thermal insulation between the skin of the user and the light emitters in the form of a transparent plastic plate, a transparent gel pad or similar poor heat conductive components. In another design, not a single, but a field of light emitting diodes are used for each of the two light emitters, all of which have the same spectral range, but the individual power is much lower, usually between 30 and 50 mA. This results in a lower ballast resistance and, consequently, a lower power loss per emitter, but also with a reduced irradiated intensity per unit area. Nevertheless, it has been found that in this case, and despite the already considerable dimensions of the sensor of about 10 × 10 mm and the LED array, which likewise has similar surfaces per emitter, a satisfactory result can still be achieved, although this is the prevailing one Doctrine that the two light paths should be as close as possible, contradicts, since with such large surface expansions, the paths from one corner of the sensor to the diagonally opposite corner of the emitter are already significantly longer than the shortest possible connection.

By arranging the light emitter and the light sensor on the bracelet (according to claim 1), that they are on opposite sides of the arm cross section when the bracelet is applied and the emitter couples the light into the arm cross section, while the light sensor is active with its active surface the surface of the arm or wrist rests, the bracelet can be fixed to the user's arm so that the emitted light from the emitter penetrates the cross section of the user's forearm and reaches the sensor in this way.

The preferred beam path is between the ulna and the spine, at a location close to the wrist, ie in the lower third of the forearm. In this length range remains even with rotation of the hand and thus of Elle and spoke against each other a free passage between these two bones.

The bracelet must be such that it not only allows this positioning, but also promotes as possible: The bracelet therefore preferably comprises a fixing device in order to be able to fix the emitter and sensor at predetermined points of the forearm or wrist. There are two fundamentally different possibilities for this:

In the first case, the positioning of emitter and sensor is done individually and preferably independently of the bracelet on the skin of the user in the right places.

Such a fixing device may be, for example, a skin-compatible Klebebe- layering on the arm-facing contact surface of the emitter and sensor.

Accordingly, light emitter and light sensor, preferably two or more light emitter are carried out together in a structural unit, not fixed, but on its back to be releasably connected to the bracelet, in particular by means of a hook and loop fastener to first the correct positioning of E- center and sensor on To be able to undertake a forearm, and then to fix it by placing the bracelet around it with the help of the bracelet in its current position.

To increase the contact pressure of the emitter and sensor can be present between or on the bracelet each Anpresseinrichtung by bias, be it generated by spring force, air pressure or the arterial pressure of the user, the right contact pressure of these two components against the arm of the patient causes and prevents in this way that after lying around the bracelet and thus effected pressing of emitter and sensor against the skin surface still a shift of emitter or sensor are possible.

The second case is to determine the position of light sensor and light emitter or the two light emitters with respect to the bracelet, preferably individually for each user. Once this is done, the user himself is able to position the wristband with the correct positioning of the wristband. tive elements, especially if the evaluation unit includes a test mode, with the help of which it is possible after applying ^{1 of} the bracelet to determine whether the achievable signals are sufficiently good and so that the positioning was sufficiently accurate. In all cases, the bracelet must be tight against the skin surface of the user with some bias so that the light emitter and light sensor are also pressed against the skin surface with the necessary bias necessary to provide good coupling and decoupling of the light from the tissue to achieve.

Preferably, a contact pressure of 2.5 to 20 mm Hg should be present. In order to be able to optically control even when the bracelet is attached, whether the bracelet and thus emitter and sensor are still in the correct position, a marking is preferably arranged on the outside of the bracelet, indicating the position of these two components.

In addition to detail problems such as wearing surface of the bracelet, sweat permeability, etc., a more important detail is the question of the extensibility of the bracelet in the circumferential direction:

Because the cross-section of an arm of a user is a variable size, which can vary greatly depending on physical activity, outside temperature, etc., even in relatively short periods. If the bracelet is extensible in the circumferential direction at least in the area between the sensors, on both opposite sides, preferably over the entire circumference, the circumferential length of the bracelet can automatically adapt to the changing circumferential length of the lower arm, and emitter and Sensors remain relative to the forearm at the same, opposite positions.

A firm, unchangeable and stretchable bracelet length would be useful if the radial distance between emitter and sensor on the one hand and the bracelet on the other hand pressure elements are housed, the radial extent may change. A change in the cross section of the forearm would then change by changing the radial extent of these pressure elements and thus only in the degree of bias, so that in these cases with a non-stretchable bracelet, in which the positioning of the active elements is less flawed, can be done.

From the technical interpretation, it should be noted that the light sensor detects the amount of light incident on it and for this purpose can receive the light of both emitters emitting light of different wavelengths, but usually not simultaneously, but with a time lag to each other, so that Light sensor, which is connected to the evaluation, knows at any time, from which of the two emitters the just received amount of light comes.

As a tissue thickness of significantly more than 1.5 cm to be irradiated by the transmission of the forearm m _. uss and additionally reflections and thus weakening of the surfaces of the bones are probable, much higher powers than in the conventional transmission pulse oximetry are necessary to produce even a usable amount of light at the sensor.

From a purely technical point of view, increasing the light emitter's performance is not a problem, but the light penetrating the tissue must not damage the tissue, in particular by the power loss of the light emitter and the associated heat generation and by the absorption of part of the amount of light energy in the tissue can happen.

Any warming of the fabric to 43 ° C or more will result in tissue damage, provided that the temperature can be applied to the tissue long enough, with the required exposure time decreasing with increasing temperature. The duration of exposure also depends in particular on the material, size of the contact surface and heat capacity of the adjacent materials, because the better the thermal decoupling of the tissue from the emitters, the lower the proportion of the power loss of the emitter is registered in the tissue and must be the upper limit be taken into account. Here is the pulsed introduction Of light has proven to be the best solution, as this can be kept short on the one hand, the duration of uninterrupted exposure to light on the fabric and on the other hand, the rest periods available between the individual exposures, in which heat in the body away facing individual parts of the meter or also the air of the environment can be delivered as high as possible.

In this case, the pulse-to-break ratio has proven to be practicable according to the solution example presented at the outset, wherein the ratio of pulse to pause as well as the pulse length and also the pause lengths in absolute time periods are preferably fixed. However, it makes sense to not let the measurements, that is to say the sequence of light pulse and pulse pause, run permanently, but rather to combine a packet of pulses into a measurement block from which a single measured value is averaged, for example from 3-5. zelmessungen.

On the other hand, the time interval between such packets or measuring blocks can be chosen to be significantly larger and, on the other hand, can be set very variably:

The principle is that the measuring blocks should take place at such a maximum time that no surprisingly strong changes in the measured value can occur during this time.

However, the user's oxygen saturation underlying the measurement may behave very differently depending on his current activity and medical history: for example, the interval between measurement gaps may be made larger, for example in the range between 2min and 5min if the user is not physically operated or Physically performs little strenuous activities, and his medical history can not be expected to strong fluctuations in the oxygen saturation content. In case of strenuous exercise or bad medical history, however, the time between the measuring blocks should be shorter, sometimes less than 1 minute, for example 15-30 seconds.

The adjustment can either be done manually by the user himself or his doctor or supervisor, or automatically self-adjusting, depending on the dedicted instantaneous measured values and / or the operating state of the user:

Thus, if the currently measured values approach the tendency rather to critical ranges of values, the time between the measurement blocks must be reduced and vice versa, the time period between the measurement blocks can be increased up to a predetermined upper limit, if for example by means of an acceleration and / or or movement sensors can be determined that the user does not move or only slightly.

The light emitters preferably emit light of the wavelengths 730 nm and 880 nm, and light emitters (LEDs), preferably lasers, are preferably used as the light emitter.

Furthermore, too much heating or faster cooling of the skin areas near the emitter can be promoted by having a cooling surface formed around the emitter of a good thermal conductivity material, such as metal, with its highly conductive front surface on the skin around the emitter rests around and there dissipate the induced heating faster than by the blood in the near-surface skin layers alone.

Preferably, the wristband also includes a temperature sensor that measures the temperature of the skin at or near the light emitter, and preferably changes the duration of the light pulses and / or the duration of the pauses therebetween as a function thereof, for example. In addition, if there is a thickness measuring device in the bracelet, with the aid of the thickness of the forearm at or near the irradiated point can be measured, in addition to the determinable by pulse oximetry values such as oxygen saturation and pulse rate and respiratory rate also absolute concentrations of certain substances in the blood of the user be determined. For the thickness measuring device, any suitable measuring method is considered, which leads to a result without active intervention of the patient, for example a measurement by magnetism, in which from one side a magnet radiates an inhomogeneous electric field in the cross section of the forearm and on the opposite side a receiver measures the intensity of the magnetic field and determines the thickness of the arm.

The absolute measurement of the received light quantity or light intensity in the absorption can also be used for this purpose, provided that a calibration of the measuring device was previously carried out for this purpose. The measurement of the tissue layer thickness can also be carried out by optical means.

With the knowledge of the layer thickness conclusions can be drawn on the absorption in the tissue by the received light intensity I is related to - then additionally to be determined - coupled light intensity I ₀ and the tissue layer thickness in between.

In order to further improve the range of use of the measuring device, depending on the degree of miniaturization, a part or the entire evaluation unit, which also contains the control for the light emitter, can be accommodated in the bracelet or on the bracelet, and optionally the energy cells, so that the bracelet forms a total self-sufficient unit in which the bracelet either has a display device to display the user himself the determined values, or wirelessly z. B. sends by mobile phone to an alarm center, which performs the monitoring of the mobile patient.

If the control panel detects any critical values, it must be able to warn the user, so in this case the meter, the mobile phone or the bracelet must have its own receiving unit for receiving warning signals.

The mobile phone could be, for example, a detachable ^'part of the bracelet. If not all parts such as power and evaluation are to be housed directly in the bracelet, they can also elsewhere, close to the body of the user, for. B. housed in a bag of the garment, and be coupled with the bracelet wirelessly over the then short distance easily.

In the simple case, the measuring device thus comprises, in addition to the power supply, at least one emitter and one sensor, an evaluation unit which merely evaluates and, if necessary, displays the light absorption. Medical conclusions are not drawn from this, but this is left to the attending physician or caregiver in the alarm center or the user on site.

The bracelet may also comprise, in an expanded embodiment, a warning device for the user, by means of which the evaluation unit or the alarm center automatically informs the user, e.g. B. by means of an acoustic and / or optical signal, indicating that measured values are in the critical range or that a specific behavior of the user is recommended.

For this purpose, the evaluation unit must be able to analyze critical ranges of values as a function of the medical history and current situation of the user.

In the event that such a warning comes too late and the user is powerless, preferably in the bracelet a tracking unit should be accommodated in order to locate the user without active assistance by means of GPS or radio cell location for mobile use and to be able to provide assistance. In order for the bracelet to be sufficiently comfortable to wear and not to be uncomfortable even when exercising or sweating, it must have a skin-friendly, non-slip coating on the one side - on the contact side towards the body - so that it can move away from the once defined position in which it also fixes emitter and sensor in your position, can not move away on its own.

Since the circumference of the forearm can change relatively strongly depending on the outside temperature, the extent of physical activity, etc., the arm band can consist of a stretchable material, especially in the area between emitter and sensor, in order to expand correspondingly to the extent of the forearm can be changed without affecting the emitter and sensor in their position on the skin surface.

In addition, the bracelet should be permeable to perspiration in as large a proportion as possible and preferably consist of a textile, washable material from which all other moisture-sensitive components can be removed.

If emitter and / or sensor unintentionally change their position on the surface of the forearm, this must be recognizable automatically, for example by the bracelet or the evaluation includes a plausibility control device that automatically detects whether the currently measured values are realistic or from misalignment of emitter or sensor, a loose wristband or other errors.

This plausibility check device can be expanded to a positioning mode, which offers the evaluation unit to determine the optimal positioning of emitter and sensor to each other or on the arm.

During the positioning, test signals can be sent from the emitter to the sensor and then checked by the evaluation unit in a special mode to see whether the result has changed from the last preceding one I

Positioning has improved or worsened and with sufficient signal intensity, an ok signal can be emitted from this unit.

Also for the real sensor itself, a certain size has proven to be predominantly optimal, namely at a diameter of between 5 mm ² and 20 mm ² , since in this range a changing power density of the received light is still easily detectable, while on the other hand the evaluation effort is not yet gets too high.

c) embodiments

Embodiments according to the invention are described in more detail below by way of example. Show it:

1 is a cross-sectional view of a finger sensor,

2 is a cross-sectional view of a forearm sensor,

3 shows the forearm in skeleton representation in the rotated and non-rotated state,

Fig. 4: occurring in the absorption of light in living tissue

Factors,

5 shows the schematic diagram of a thickness measuring device, and

Fig. 6: schematic representations of the measuring device according to the invention.

Fig. 1 shows in cross-section the situation with the known finger sensor:

In this case, on one side of the cross section of the finger 23, the two light emitters 2a and 2b, which enter the tissue with different spectral ranges, are seated. irradiate be of the finger. The light beams can not pass through the finger bones 24 lying inside the finger, since the light beams are emitted from the light emitters 2a, 2b not only in exactly one direction, but fan-shaped in several directions into the tissue Tissue deflected or broken so that they reach the sensor 3, as shown by an exemplary light path line for both sides of the bone 24.

This amount of light arriving at the sensor 3 through the tissue and around the bone 24 provides a measure of the light absorbed by the tissue portions of the light, and in turn can be used as a conclusion to the arterial oxygen saturation of the user by the modulation depths of the two spectral ranges in which the emitters 2a, 2b operate as described above in relation to each other.

Fig. 2 shows the situation in the forearm sensor according to the invention.

Although the size ratios are not even true to scale, it is clear that the layer thickness to be irradiated is substantially greater, in particular a multiple compared to the finger sensor. Furthermore, Fig. 2 shows the difficulty that in this case two bones (Elle 27 and spoke 28) are adjacent to each other in the forearm 25 and - as the representations of the skeleton of Fig. 3a and 3b show - when twisting the forearm around the elbow strongly against each other to be crossed.

It can be seen that, in the non-entangled state according to FIG. 3a, a sufficiently large, lenticular gap remains between the ulna and the spoke, but this gap in the entangled state according to FIG. 3b, on the one hand, becomes very narrow and, on the other hand, only in the distal, the wrist adjacent area.

For this reason alone, in practice, in addition to the large layer thickness to be irradiated, it has been thought impossible to penetrate the forearm. unless the ability to move the forearm is restricted.

In practice, however, has proven that a radiation is possible, either according to the schematic diagram of Fig. 2a, in the majority of the light arriving at the sensor 3 amount of light has moved through the gap between Elle 27 and spoke 28, which is the ideal Positioning of the two emitters 2a, 2b and the sensor 3 represents, which are then located exactly on the center line of this space opposite each other.

The two emitters 2a, 2b can also be combined to form a single emitter element, which is then handled as a structural unit.

Fig. 2b at not quite correct positioning with respect to the cross section, as emitter 2 and sensor 3 with respect to the cross section by only about 120-150 ° offset from each other can be, with the result that then arrive at the sensor 3 lights, the only z. T. in the space between Elle 27 and spoke 28 have been blasted through, but were partially also passed to Elle and spoke passing through the tissue.

Surprisingly, a radiation of the wrist, so through the carpal bones through, possible and still delivers usable results, so that it must be assumed that always a portion of the incident light actually multiple refraction and distraction a path through all existing spaces through the Bone through to the opposite sensor finds.

5 further shows, in a schematic representation, the mode of operation of a thickness measuring device 20 using the example of a device functioning by means of magnetism:

In this case, on one side of the cross section of the lower arm 25, a magnet 20a is arranged, which is thus one of the contact surface of the magnet on the skin from fan-shaped radiating, and thus inhomogeneous magnetic field in the forearm 25 radiates into it.

If a magnetic field sensor 20b is arranged at any point in relation to the magnet, then due to the weakening of the magnetic field it will determine a field strength with increasing distance from the magnet - visible on the basis of the increasing distance of the magnetic field lines - which measures the distance of the magnetic field sensor 20b from the magnet 20a and thus for the irradiated thickness of the forearm 25 is.

Magnet 20a and magnetic sensor 20b are preferably also arranged on the bracelet, in particular as close as possible to light emitter and light sensor in order to capture as accurately as possible the layer thickness there.

Of course, the layer thickness does not play the sole role in which portions or amounts of incident light are absorbed by the tissue:

Thus, FIG. 4 graphically shows which factors cause a reduction of the incident output intensity of the light and its decreasing effect in this order:

It is clear that the tissue components and in particular the non-perfused outer skin layers greatly impair the light intensity, in particular due to unfavorable scattering conditions.

The next stronger factors are the bypass paths due to the non-radiopaque bones, which cause only a correspondingly small amount of radiation to find the path around the bone to the sensor, while much of the radiation is reflected or absorbed by the bones and the sensor not reached.

Further influencing factors are then veins, capillaries and arterioles, whereby in the case of the arterioles the constantantii is to be distinguished from the pulsatile part: Since the arterioles regularly expand and contract due to the pulse, the influencing of the light passed or passed therethrough is acted upon by this pulsatile behavior, for which reason the light path concretely to be traced depends also on the instantaneous diameter of the corresponding arteriole and therefore the boundary line which the Lichtwegsliήie represents, is not a straight line.

This, in turn, also influences the light intensity to be measured at the sensor, in that it likewise changes in a pulsating manner, as can be seen from the non-straight line of the light intensity.

Fig. 6 shows a schematic representation of the worn on the wrist of the user cuff in not twisted (Fig. 6a) and twisted forearm (Fig. 6b).

It can be seen that in the region of the lower, ie distal end of the forearm, possibly already in the area of the wrist, around the circumference of the forearm around a bracelet 6 is arranged, which fits closely to the arm circumference, ie the skin 33, and on the inside on mutually opposite sides of the bracelet 6 on the one hand a light sensor 3 and on the other hand a surface with one or better two different light emitters 2a, 2b are arranged, which emit light in different spectral ranges, so that the transmission direction 34 transverse to the longitudinal direction 10th of the forearm 25 passes.

As the figures show, the emitter 2 and sensor 3 are arranged with respect to the circumference of the arm so that their imaginary connecting line (transmission direction 34) extends between the ulna and the spoke, both in the unentangled state of the ulna and the spoke, as shown in FIG 6a, in which this the remaining space between them is larger, as well as in the entangled state of these two bones according to FIG. 6b. It should be noted that an evaluable measurement result can usually still be achieved even if no straight-through radiation from the emitter to the sensor is available between the ulna and the spoke, but the light rays are nevertheless deflected in such a way that they also randomly multiply angled light paths from the light source Find emitter towards the receiver.

The bracelet 6 rests so tightly on the wrist that slipping of the bracelet 6 is very unlikely both in the longitudinal direction 10 of the forearm 25 and in the circumferential direction or in the normal operations of the user for whom the bracelet is designed , does not occur.

Fig. 6c also shows the bracelet in an applied state in a cross-sectional view. In this case, two light emitters 2a, b are attached to one side of the cross section of the forearm 25 by means of a fixing device 9 and glued on the opposite side also by means of a fixing device 9, such as an adhesive layer, a light sensor 3 on the skin of the forearm.

On the back of the light emitter 2b is a through both continuous plate as a heat sink 18 ', which thus consists of a material of high heat capacity.

Both the two light emitters 2a, b and the light sensor 3 are acted upon radially from the inside of the bracelet 6 from their rear side facing away from the lower arm 25 by means of a pressure device 11, for example a spring. For this purpose, the bracelet 6 is located at least in partial areas of the circumference of the forearm 25 preferably on this.

FIG. 6c further shows an energy cell 5, which can likewise be arranged on the bracelet 6, or an acceleration sensor 22 'and / or motion sensor 22. Likewise, a display unit 7 can be mounted on the outside of the bracelet in the field of vision of the user Arranged bracelet and / or a transmitter 8. The bracelet 6 is preferably not endless, but can be fastened by means of its against each other to be joined ends, for example by means of a hook and loop fastener 13, also close fitting to the forearm.

The fixing device 9 between the light emitters 2a, b and the lower arm may additionally be designed as a temperature sensor.

LIST OF REFERENCE NUMBERS

1 measuring device

2a, b light emitter

3 light sensor

4 evaluation unit

5 energy cell

6 bracelet

7 display unit

8 stations

9 fixing device

10 longitudinal forearm

11 pressing device

12 glue

13 Kiettverschluss

14 mark

15 alarm center

16 locating unit

17 warning device

18 cooling surface

18 'heat sink

19 temperature sensor

20 thickness gauge

20a magnet

20b magnetic sensor

21 Plausibility check device

22 motion sensor

22 'acceleration sensor

23 fingers

24 finger bones 25 forearm

26 layer thickness

27 cubits

28 spoke

33 skin

34 transmission direction

Claims

1. measuring device (1) for the absorption of light by living tissue with at least one light emitter (2), at least one light sensor (3), at least one evaluation unit (4), and - an energy cell (5), characterized in that the measuring device (1) comprises a bracelet (6) on which at least the light emitter (2) and the light sensor (3) are arranged so that the light from the light emitter (2) at the light sensor (3) the distal forearm or the wrist has gone through.

2. Measuring device according to claim 1, characterized in that the light sensor (3) incoming light has passed through the forearm to ulna or spoke around, in particular has passed through between ulna and spoke.

3. Measuring device according to one of the preceding claims, characterized in that the emitter (2) and sensor (3) under optically constant coupling and decoupling conditions, in particular stationary, are arranged on the forearm or wrist.

4. Measuring device according to one of the preceding claims, characterized in that the measuring device (1) comprises two different light emitter (2) for light of different wavelengths or spectral ranges.

5. Measuring device according to one of the preceding claims, characterized in that the light sensor (3) detects the received light quantity.

6. Measuring device according to one of the preceding claims, characterized in that the measuring device (1) is designed so that at the light sensor (3) a photocurrent of at least 0.01 uA to 0.1 uA by the reception of the light emitter (2) emitted light is obtained.

7. Measuring device according to one of the preceding claims, characterized in that the measuring device (1) is designed so that the light sensor (3) has a light output of 60 nW on the entire sensor surface 'and in particular the sensor surface between 0.5 and 100 mm ² .

8. Measuring device according to one of the preceding claims, characterized in that in the case of two individual LEDs as light emitters they have a current intensity of at least 100 mA each.

9. Measuring device according to one of the preceding claims, characterized in that when using several parallel-connected LEDs as a light emitter, the current intensity of the individual LEDs is preferably below 50 mA.

10. Measuring device according to one of the preceding claims, characterized in that the measuring device, in particular the bracelet (6), a fixing device (9) for fixing the emitter (2) and sensor (3) at predetermined locations of the forearm or wrist comprises.

11. Meter, d 'according to one of the preceding claims, characterized in ^that: ass the meter (1), in particular the bracelet (6), a pressing device (11) for pressing the light emitter (2) and / or light sensor (3) against the Forearm or wrist includes.

12. Measuring device according to one of the preceding claims, characterized in that the two light emitters (2a, b) are arranged in fixed relation to each other.

13. Measuring device according to one of the preceding claims, characterized in that the light emitter (2a, b) emit light of wavelength 730 nm and 880 nm.

14. Measuring device according to one of the preceding claims, characterized in that at least two light-emitting diodes (LEDs) of different spectral ranges are used as the light emitter.

15. Measuring device according to one of the preceding claims, characterized in that a white light emitting diode is used as the light emitter, are extracted from the two different spectral ranges of light by means of filters.

16. Measuring device according to one of the preceding claims, characterized in that the contact pressure of emitter and sensor against the forearm between 2.5 and 50 mm Hg-column, in particular between 3.0 and 15.0 mm Hg-column.

17. Measuring device according to one of the preceding claims, characterized in that

Emitter and / or sensor are releasably attached to the bracelet (6) and in particular on their forearm facing contact surface a skin-friendly Kei- Over (12), and on its back the ¹ fixing device (9) for fixing on the bracelet (6) is arranged, in particular a hook-and-loop fastener (13).

18. Measuring device according to one of the preceding claims, characterized in that ¹ on the outside of the bracelet (6) has a mark (14) for the position of the emitter (2) and / or sensor (3) is present.

19. Measuring device according to one of the preceding claims, characterized in that the bracelet (6) comprises a transmitter (8) for wireless transmission of the signals of the sensor (3), in particular by means of mobile radio.

20. Measuring device according to one of the preceding claims, characterized in that 'the bracelet (6) at least parts of the evaluation unit (4), in particular the entire evaluation unit (4), carries and the transmitter transmits the evaluation results to an alarm center (15) if one of the determined values lies in the critical range.

21. Measuring device according to one of the preceding claims, characterized in that the bracelet (6) comprises a locating unit (16).

22. Measuring device according to one of the preceding claims, characterized in that the bracelet (6) comprises a display unit (7) and in particular a warning device (17).

23. Meter according to one of the preceding claims, characterized in that the or the light emitter (2) are in thermal communication with parts of the measuring device, which have a high heat capacity and in particular thermal see insulating devices between the emitter (2) and the skin surface of the user are arranged, in particular in the form of an intermediate layer of poor thermal conductivity material such. As plastic or a gel pad.

24. Measuring device according to one of the preceding claims, characterized in that the bracelet (6) comprises a temperature sensor (19), in particular in the vicinity of the light emitter (2).

25. Measuring device according to one of the preceding claims, characterized in that the bracelet (6) comprises a thickness measuring device (20) for measuring the distance between emitter (2) and sensor (3), in particular the thickness measuring device by means of magnetism works, in which the receiver measures the strength of the magnetic field emitted by the transmitter or works visually on the loss of light.

26. A meter according to claim 25, characterized in that the thickness measuring device (20) through the tissue measures the distance between a transmitter and a receiver and transmitter and receiver are arranged directly adjacent to the emitter (2) and the sensor (3) or with these are identical.

27. Measuring device according to one of the preceding claims, characterized in that the bracelet (6) comprises a measured value plausibility control device (21).

28. Measuring device according to one of the preceding claims, characterized in that the evaluation unit is able to determine the oxygen saturation, the heart rate, the respiratory rate and / or the blood pressure from the data determined by the sensor.

29. Measuring device according to one of the preceding claims, characterized in that the evaluation unit (4) is able to determine absolute concentrations of components of the tissue or blood by utilizing the measured input light intensity (Io) at the transmission site.

30. Measuring device according to one of the preceding claims, characterized in that the evaluation unit (4) and / or warning device (17) or display unit (7) wirelessly over a short distance of a maximum of a few meters with the bracelet (6) are in communication.

31. Measuring device according to one of the preceding claims, characterized in that the evaluation unit (4) comprises a positioning mode in which the optimal relative positioning of emitter and sensor can be determined or tested to each other.

32. Measuring device according to one of the preceding claims, characterized in that the evaluation unit (4) can also evaluate the signals for other vital parameters and the measuring device has further sensors, for. B. an acceleration sensor (22 '), a position sensor or a motion sensor.

33. Measuring device according to one of the preceding claims, characterized in that the light emitters each emit pulsed light with a pulse to pause ratio of at least 1: 5, better at least 1:30.

34. Measuring device according to one of the preceding claims, characterized in that, the duration of each pulse is less than 1 ms.

35. A method for measuring the absorption of light by living tissue by means of a light emitter (2) and a light sensor (3) and an evaluation unit, characterized in that from the light sensor (3) from the opposite light emitter (2) incoming light amount, the distal Forearm or, has passed through the wrist, is measured.

36. The method according to claim 35, characterized in that the absorption is determined in at least two different spectral ranges.

37. The method according to any one of the preceding method claims, characterized in that the measuring device is connected via mobile communication with a service provider.

38. Method according to one of the preceding method claims, characterized in that the emitter (2) and sensor (3) are arranged under optically constant coupling and decoupling conditions, in particular stationary, on the forearm or wrist.

39. The method according to any one of the preceding method claims, characterized in that in the case of two individual LEDs as a light emitter, these have a current intensity of at least 100 mA each.

40. The method according to any one of the preceding method claims, characterized in that> when using a plurality of parallel-connected LEDs as a light emitter, the current intensity of the individual LEDs is preferably less than 50 mA.

41. Method according to one of the preceding method claims, characterized in that

Signals for other vital parameters can be evaluated, for. As acceleration, position or movement.

42. The method according to any one of the preceding method claims, characterized in that the light emitters each emit pulsed light ¹ with a pulse to pause ratio of at least 1: 5, better at least 1:30.

43. Method according to one of the preceding method claims, characterized in that the duration of a pulse is less than 1 ms in each case.

44. Method according to one of the preceding method claims, characterized in that the light emitters (2a, b) emit light of the wavelengths 400 nm to 2,000 nm, in particular 600-1,000 nm.

45. The method according to any one of the preceding method claims, characterized in that the measurements are carried out in the form of packets of individual measurements, the number of which is sufficient to form a reliable average value.

46. Method according to one of the preceding method claims, characterized in that the time interval between the execution of the individual packet measurements is substantially greater than the time interval between the individual pulses of a packet measurement, in particular in the range between 20 s and 5 min, and the time interval is manually selected by the user between packages, or fixed based on the history of the user, or determined based on the current informational situation.

47. Method according to one of the preceding method claims, characterized in that light-emitting diodes (LEDs) are used as the light emitter (2).

48. The method according to any one of the preceding method claims, characterized in that the contact pressure of emitter (2) and sensor (3) against the forearm is at least 2.5 mm Hg.

49. The method according to any one of the preceding method claims, characterized in that the emitter (2) and / or sensor (3) are glued to the skin surface.

50. The method according to any one of the preceding method claims, characterized in that the signals from the sensor (3) are transmitted to an evaluation and / or wireless from the evaluation to a display unit.

51. The method according to any one of the preceding method claims, characterized in that the overheating of the tissue of the user is prevented.

52. The method according to any one of the preceding method claims, characterized in that in the vicinity of the emitter (2), the temperature on the contact surface of the skin of the user, to which the emitter (2) is applied, is measured.

53. The method according to any one of the preceding method claims, characterized in that in addition the thickness of the irradiated tissue, ie forearm or wrist, is measured.