WO1996027325A1

WO1996027325A1 - Device for measuring oxygen saturation in the blood present in the body

Info

Publication number: WO1996027325A1
Application number: PCT/CH1996/000073
Authority: WO
Inventors: Albert W. Huch; Renate Chr. Huch; Volker König
Original assignee: Huch Albert W; Huch Renate Chr; Koenig Volker
Priority date: 1995-03-03
Filing date: 1996-03-04
Publication date: 1996-09-12

Abstract

The proposed device (1) has a sensor (2) with a rubber-elastic support (8). The latter has on the front face (4) of the sensor (2) an annular groove (8b) and two annular lips (8f, 8g), one of which is enclosed by the annular groove (8b) while the other encloses the annular groove (8b). The annular groove (8b) has an inner deeper section (8c) and an outer shallower section (8d). Light-emitting diodes (15) are provided in the region of the front face (4) enclosed by the annular ring (8b) and the inner lip (8f). Photo-semiconductors (20) are provided behind the outer section (8d) of the annular groove (8b). In order to carry out a measurement, the sensor (2) is placed on a living body (61) and the fluid pressure in the annular groove (8b) is lowered to below atmospheric pressure which presses the sensor against the body (61). This ensures a good blood supply to the region of the body (61) used for the measurement.

Description

DEVICE FOR MEASURING OXYGEN SATURATION OF BODY IN THE BODY

Technical field

The invention relates to a device for measuring at least one property of a living body, in particular for the non-invasive measurement of the oxygen saturation of blood present in the body.

The term "non-invasive" means that the measurement is carried out without an instrument penetrating the body and in particular a blood vessel.

Oxygen saturation means the degree of saturation of the blood with oxygen-containing hemoglobin, or more precisely, the ratio between the concentration of oxygen-containing hemoglobin, i.e. of oxyhemoglobin, and total hemoglobin concentration.

State of the art

Devices with a sensor for non-invasive measurement of oxygen saturation are known from DE-A 4 407 541 and EP-A 0 442 011. The two documents also disclose, among other things, sensors provided for attachment to a fetus, the light-emitting diodes and a photo semiconductor arranged between them in the center of the sensor, have two annular contact surfaces and an annular groove present between them. The ring groove and the two ring-shaped contact surfaces enclose the light-emitting diodes and the photo semiconductor. The parts of the sensors which delimit the annular groove and form the support surface obviously consist of dimensionally stable materials. One of the sensors known from DE-A 4 407 541 also has an electrode which consists of a tube which surrounds the photo semiconductor and separates it from the light-emitting diodes and is probably formed from a metallic material and is dimensionally stable.

For the attachment of one of these known sensors to a fetus, the sensor is arranged on the body of the fetus. A negative pressure is then generated in the ring groove of the sensor. The pressure of the air in the vicinity of the sensor then presses the sensor against the body of the fetus. As a result of the negative pressure in the ring groove, the skin is drawn into the ring groove. The skin therefore forms a bead protruding into the ring groove. This pressure and the pressure exerted on the skin at the two edges of the ring groove inhibit the inflow of blood to the measurement area of the skin located opposite the light-emitting diodes and the photo semiconductor and the outflow of blood from this measurement area. This obstruction of the blood flow to the area of the skin in front of the light-emitting diodes and the photo-semiconductor reduces the accuracy and the reliability of the measurement of the oxygen saturation. In the case of the sensor, which has a tube that acts as an electrode and presses on the skin, this additionally impedes the blood flow to the area of the skin located in front of the photo semiconductor.

The sensors are usually attached to a surface area of the head of the fetus. This surface area is normally slightly curved, the shape of the surface area depending on its position on the head and can also vary from fetus to fetus. Since the sections of the known sensors intended to rest on the body of the fetus are apparently dimensionally stable, there is also the danger in the known sensors that the annular groove of a fetus on the outer and / or the inner edge when the sensor is placed on a surface section of the body the ring groove is not sealed tightly. This can impair the attachment of the sensor and / or the blood flow to the measuring area.

Similar problems as when attaching a sensor used to measure the oxygen saturation of blood can also arise in devices for non-invasive, optical measurement of at least one other property of blood or a perfused tissue or other component of a living body, in which a sensor is temporary must be attached to the body.

Outline of the invention

The invention has for its object to provide a device which avoids disadvantages of the known devices and in particular enables the oxygen saturation of blood and / or possibly another property of blood and / or of a blood-circulating tissue to be measured precisely and reliably, although in a negative pressure is generated in the ring groove of the sensor.

This object is achieved according to the invention by a device with the features of claim 1.

Advantageous refinements of the device emerge from the dependent claims.

The device according to the invention has a sensor and light radiation means as well as light receiving means in order to at least one light emission point and at least one light receiving point on the front of the sensor to radiate light into the body to be examined or to receive light retroreflected therefrom. The sensor also has an annular groove on its front. According to the invention, the device furthermore has means for lowering the pressure of the air present in the annular groove and / or possibly fluid-containing fluid below the air pressure prevailing in the vicinity of the sensor. The sensor is then pressed against the body by the ambient air pressure or - more precisely - by the differential pressure between the environment and the annular groove and is held firmly on the body.

According to the invention, at least a section of the ring groove of the sensor - preferably at least the deepest section of the ring groove having the bottom thereof - is arranged in a plan view of the front side of the sensor between the or each light emitting point and the or each light receiving point. It is thereby achieved that an area of the living body that is traversed or irradiated during the measurement of light is located outside the mentioned section of the annular groove and is well supplied with blood. This good blood circulation enables an accurate and reliable measurement.

The ring groove is preferably located between two ring-shaped sections of the sensor, which are intended to rest on the body during measurement. Each of these annular sections is preferably elastically deformable and has, for example, an elastically deformable one

Lip or thin rib on. Furthermore, the sensor preferably has a one-piece, rubber-elastic support which delimits the annular groove and the two annular, elastically deformable sections of the sensor which are intended to lie on the body and have a lip or rib forms. This enables the sensor of the knife to »adapt well to the shape of the body surface and to lie tightly on the body inside and outside the ring groove. Furthermore, the elastic deformability of the lips or ribs and the support contributes to that from the sensor to the

Distribute body pressure forces evenly and keep them low, so that nowhere are excessive pressure forces exerted on the body. This in turn supports good blood circulation in the measuring area of the body that is passed through when measuring light.

Since, in particular, the inner, ring-shaped section of the sensor is elastically deformable and bears against the body everywhere during measurement, it ensures that no light can get from a light emitting point to a light receiving point without passing through a section of the body. This also contributes to an accurate and reliable measurement.

In a particularly advantageous embodiment of the device according to the invention, the or each light emission point is located in a plan view of the front of the sensor in the area enclosed by the annular groove. In this case, there are preferably a plurality of light receiving points distributed around said section of the annular groove. This enables a high light output.

In an advantageous embodiment of the device, each light emission point is formed by a light-emitting diode arranged in the sensor and each light receiving point is formed by a photo semiconductor arranged in the sensor.

Instead of light-emitting diodes arranged in the sensor, the light-emitting means can possibly be arranged outside the sensor in the measuring apparatus or other light-emitting diodes

Light generating means for generating light with different NEN wavelengths have. These light generating means can then be connected to the sensor via at least one flexible light guide. Instead of photo semiconductors arranged in the sensor, the light receiving means can have at least one photo semiconductor or other light sensor arranged outside the sensor in the measuring apparatus, which can be connected to the sensor via at least one flexible light guide. The light beams and light receiving points of the sensor can then be formed by the ends of the light guides and / or lenses or the like arranged at these ends.

When holding the sensor with the aid of the ambient air pressure or differential pressure between the surroundings and the recess, it is particularly advantageous that the sensor is reliably held on living bodies even if the latter has a moist surface and / or if the sensor comes into contact with a liquid during and / or after application to the body. The device is therefore particularly suitable for carrying out a measurement on the body of the fetus or child during the birth of a child.

Brief description of the drawings

The subject matter of the invention is explained below using an exemplary embodiment shown in the drawing and variants thereof. In the drawing shows

1 shows a simplified top view of the front of the sensor of a device for measuring the oxygen saturation of blood and the pulse frequency,

2 shows a simplified axial section through the sensor, the support of the latter being in the undeformed state in FIGS. 1 and 2, and 3 shows an axial section through the sensor arranged on a living body and having a deformed support, and a schematic representation of further parts of the device.

description of the preferred exemplary embodiments

A device designated as a whole by 1 in FIG. 3 for the non-invasive measurement of the oxygen saturation of

Blood and the pulse frequency have a sensor 2 that can be seen in FIGS. 1 to 3. This defines an axis 3 and has an outline shape that is essentially symmetrical to this. The sensor 2 has a front side 4, a rear side 5 facing away from it and a largely cylindrical outer surface surrounding the axis 3.

The sensor 2 has a housing 7. As the main component, this has an elastically deformable support 8, which consists of a rubber-elastic, electrically insulating material, for example silicone rubber. The support 8 is elastically deformed when the sensor 12 is used for a measurement in a manner described in more detail. The support 8 is shown in FIGS. 1 and 2 in a relaxed, undeformed state and in FIG. 3 in a deformed state, the shape of the latter resulting from the elastic deformation of the support being shown somewhat schematically and in a simplified manner.

The support 8 is rotationally symmetrical to the axis 3 and essentially disk-shaped. The axial dimension of the undeformed support 8 is significantly smaller than its maximum diameter and is preferably at most 50% of the latter. The maximum diameter of the support 8 forming the maximum diameter of the entire sensor is preferably at most 30 mm and more preferably at most 25 mm. The support 8 has a blind hole 8a coaxial to the axis 3 and opening into the central region of the front side 4. This is circular in the plan view of the front side 4 and has a cylindrical main section, at least in the case of undeformed support, which is located in the vicinity of the base of the

Blind holes is divided by a constriction. The blind hole 8a has at its end opening at the front side 4 of the sensor in its vicinity a short, with undeformed support cylindrical mouth section, the diameter of which is somewhat larger than that of the main section.

The support 8 also has an annular groove 8b which is arranged on the front side 4 and is open at this, coaxial to the axis 3. This is in axial section on the outer, i.e. stepped further away from the axis 3 and has a deeper inner section 8c and an outer, less deep outer section 8d. This forms an extension of the annular groove 8b in the mouth region 8b opening into the surroundings of the sensor. The depth of the outer section 8d of the annular groove 8b is at most

50% and for example at most or about 30% of the depth of the inner portion 8c of the annular groove. The inner section 8c has at the base of the annular groove 8b an undeformed support 8 which is flat and at right angles to the axis 3. The inner section 8c widens in axial section from its base and has side surfaces inclined away from one another towards the mouth of the annular groove 8b, which are conical when the support 8 is undeformed. The outer section 8d has a shoulder surface which adjoins the outer side surface of the inner section 8c further away from the axis 3 and, together with the last-mentioned side surface, forms a shoulder surface which is flat in the case of undeformed support and is perpendicular to the axis 3. The outer section 8d has on its outer side, which is further away from the axis 3, an outer side surface which inclines outwards in the direction away from the shoulder surface and away from the axis 3 and shaped support 8 is conical. The support 8 has several, preferably at least three and, for example, six blind holes 8e distributed uniformly around the axis 3, which open into the shoulder surface of the outer section 8d of the annular groove 8b and in the top view of the front side 4, for example at least at its mouth generally square, approximately rectangular.

The support 8 also has on the front side 4 two sections which protrude in a more or less axial direction from the rest of the support sections and are coaxial with the axis 3 and which are ring-shaped, namely circular, in a plan view of the front side 4. These are formed by a lip or narrow rib and are referred to below as inner lip 8f or outer lip 8g. The inner lip 8f is located between the mouth portion of the blind hole 8a and the annular groove 8b. The outer lip 8e encloses the outer section 8d of the annular groove 8b and forms the front edge of the support 8 and the entire sensor 2. Each lip 8f, 8g has at its free end an annular end or front surface which provides undeformed support 8 is flat and perpendicular to axis 3. Each lip 8f, 8g has an inner and an outer side surface. The inner side surface of the inner lip 8f is formed by the surface delimiting the mouth section of the central blind hole 8a and is accordingly cylindrical when the support is not deformed. The outer side surface of the inner lip 8f is identical to the inner side surface of the annular groove 8b and thus approaches the axis 3 with undeformed support towards the free end of the lip 8f. The inner side surface of the outer lip 8g is identical to the inclined, outer side surface of the Ring groove section 8d. The outer side surface of the outer lip 8g is inclined outwards from the axis 3 towards the free end of the lip and is conical in the case of an undeformed sensor and approximately or exactly parallel to the inner side surface of the lip 8g in axial section. The outer lip 8g is accordingly IC

speaking towards its free end inclined outwards from axis 3.

The support 8 has a hole-free extension which extends over the entire rear side 3 of the sensor 2 and forms its rear boundary on the entire rear side 4, i.e. compact chick section 8h, which connects the lips 8f, 8g and the remaining front sections of the support to one another and closes the blind hole 8a, the annular groove 8b and the sackcloths 8e gas-tight from the surroundings. The undersurface of the support is slightly convex, for example, when the support is not deformed. The undersurface of the support 8 is for the most part with undeformed support - d. H. apart from its part formed by the outer lip 8g - cylindrical.

The sensor 2 has a sleeve 11 which is seated in the blind hole 8a of the support 8 and which can possibly also be understood as part of the housing 7. The sleeve 11 is essentially dimensionally stable and consists, for example, of a

Plastic, the modulus of elasticity of which is considerably greater than the modulus of elasticity of the silicone rubber forming the support 8. The sleeve 11 has an outer circumferential surface, which is largely cylindrical, but has an annular groove near the end of the sleeve located at the bottom of the blind hole 8a. The support 8 has an annular section which forms the constriction of the blind hole 8a and engages in the annular groove and which firmly anchors the sleeve 11 in the support 8. The front end of the sleeve 11 facing away from the base of the blind hole 8a is located within the mouth section of the blind hole 8a. The sleeve 11 has a continuous, axial hole which has an extension at the front end of the sleeve.

The sensor 2 has only simplified and schematically drawn light radiation means 13. These have at Example, a plate-shaped or block-shaped carrier 14 and two light-emitting diodes 15 with electrical connections 16. The two light-emitting diodes 15 consist, for example, of sections of a chip or of separate, discrete components. The two light-emitting diodes 15 are designed to generate essentially monochromatic light with two different wavelengths - for example red or infrared light.

The carrier 14 is fastened with a casting compound 17 filling the free areas of the interior of the sleeve 11 and possibly with additional fastening means, for example in the sleeve 11 in such a way that its end face and the light radiation locations or surfaces of the light-emitting diodes 15 are approximately or exactly flush are with the front end of the sleeve 11.

The sensor 2 also has light receiving means 19. These have a plurality of, preferably at least three, and in particular six, photo-semiconductors 20 with connections 21, which are only shown in simplified form. Each photo semiconductor 20 consists of a photodiode, which is only shown in simplified form, and is fastened with a casting compound, not shown, and / or other fastening means behind the outer section 8d of the annular groove 8b in one of the blind holes 8e in such a way that its light receiving area or surface is approximately or exactly flush with the

Shoulder surface of the outer portion 8d of the annular groove 8b.

In the case of undeformed support 8, the two lips 8f, 8g protrude furthest from the remaining parts of the sensor 2 on the front side 4 of the sensor 2 in the direction running along the axis 3. The end or front surfaces of the two lips 8f, 8g lie in a common plane and, when the support 8 is relaxed and undeformed, define a flat lubricating surface 22 which clings to the front side 4 of the sensor 8

Support 8 with the end or front surfaces of the two lips 8f, 8g lie on a flat support and / or counter surface which coincides with the flat lubricating surface 22. The free ends of the two lips accordingly form at least one support 23 of the sensor 2 in the case of undeformed support 8. The region of the mouth section of the blind hole 8a which is free in the case of undeformed support 8 and when the sensor is not used, ie only air but no solid material, forms a depression 23 of the sensor 2. When the sensor is not used, the annular groove 8f contains only air, but no solid material, is therefore free and forms a recess 25 of the sensor. In the case of undeformed support 8, the light-emitting diodes 15 and the photo semiconductors 20 are at short distances from the flat sliding surface 22 and are separated from it by free interspaces.

An electrical, easily bendable cable 26 has several electrical, insulated conductors and an electrically isolating sheath. One end of the cable 26 is inserted at a point on the lateral surface of the support 8 and firmly connected to it. The connections 16 of the light-emitting diodes 15 are electrically conductively connected to conductors of the cable 26 through the interior of the sleeve 11 and through the insulating material of the support 8. The connections 21 of the photo semiconductors 20 are electrically connected to conductors of the cable 26 through the material of the support 8. The end of the cable 26 that is not attached to the sensor is provided, for example, with a plug 27.

The device has a flexible hose 28, for example made of rubber-elastic material. One of the ends of the hose 28 projects into the latter at a point on the lateral surface of the support 8 and is fastened on and / or in the support 8 such that the interior of the hose 28 is connected to the inner section 8c of the annular groove 8b. At the other end of the hose 28, a coupling piece 29 shown in FIG. 3 is attached. When manufacturing the sensor 2, for example, the carrier 14 with the light-emitting diodes 15 can first be inserted into the sleeve 11, the connections 16 of the light-emitting diodes 15 connected to the provided conductors of the cable 25 and the sleeve 11 poured out with the sealing compound 17. Furthermore, the sleeve 11 prepared in this way with the light-emitting diodes 15 and the photo semiconductors 20 can be inserted into a casting mold and held with holding means from the back of the sensor ht-r to be formed. Furthermore, one end of the cable 26 and this conductor connecting the light-emitting diodes 15 and photo semiconductors 20 and one end of the hose 28 can also be arranged in the casting mold. Then, for example, in a first casting process with the help of the casting mold, a first part of the part forming the front of the support with the lips 8f, 8g and the blind hole 8a and the annular groove 8b is delimited

Pour supports 8. The sleeve 11 with the light-emitting diodes 15 and the photo semiconductors 20 are then held in this part of the support 8. One can now replace part of the mold, remove the holding means and in a second casting process the second, the rest, for example the back of the

Pour the support forming part of the support. When the second part is cast, the holes formed in the previously cast, first part as a result of the holding means are filled and the two successively cast parts are connected to one another in such a way that the support 8 practically forms a one-piece body after completion.

However, it should be noted that the order of the steps of the manufacturing process can also be changed. Furthermore, parts of the support cast in succession can be connected to one another, if necessary, with the aid of an additional binder. The finished support 8 then again forms almost a one-piece body.

The device 1 also has a measuring apparatus 31 only shown in FIG. 3. This is schematic as Block drawn and consists, for example, of several devices with separate support structures and housings. The measuring apparatus 31 has, for example, several devices designed as inserts and held in a common frame and a commercially available, programmable computer. The plug 27 fastened to the cable 26 is detachably connected to a plug 33 fastened to a housing on the measuring apparatus 31. The measuring apparatus 31 has electronic circuit means 34 which are electrically connected to the plug 33. The electronic circuit means 34 are shown schematically as a block, but can be distributed over several devices and in part can be formed by the aforementioned computer. The electronic circuit means 34 have various electronic components, such as, for example, a clock generator with an oscillator and a pulse generator which can be controlled by this clock generator and which generates electrical voltage pulses during operation of the device and supplies it to the light-emitting diodes 15. The circuit means 34 also have an evaluation circuit that can be controlled by the clock generator, in order to process and evaluate the electrical voltages supplied by the photo semiconductors 20 during operation, which in analog form provide a measure of the strength of the light received by the photo semiconductors. Furthermore, there is at least one analog / digital converter in order to convert analog signals generated by the evaluation circuit into digital signals and convert them to one

Processor of the mentioned computer and / or another processor for processing digitally represented data. The electronic circuit means are connected to at least one display device 35 for digital display of the pulse frequency f and the oxygen saturation SA. The display device 35 or one of the display devices is formed, for example, by the screen of the aforementioned computer.

The device 1 also has suction means 37. These have, for example, in a device or slot housed pump 38 for sucking air and generating a vacuum with an electric motor 38a. The inlet of the pump 38 is connected to a fluid connection 41 via a line and two connections and a passage of a manually operable three-way valve 39. In the line connecting the pump 37 to the fluid connection 41 - for example between the pump 38 and the three-way valve

39 - a pressure sensor 40 is arranged. The outlet of the pump 38 is connected to an air outlet opening into the surroundings of the measuring device 31. The third connection of the three-way tap

40 is connected to an air inlet 42, which has a ventilation opening opening into the surroundings. The motor 38a and the pressure sensor 40 are electrically connected to control means of the electronic circuit means 34. The measuring apparatus 31 has not yet drawn, manually operable operating elements, such as push buttons, at least one rotary resistor and the like. Furthermore, the measuring apparatus 31 can additionally have signal lights (not shown), for example consisting of light-emitting diodes or lamps, an optical and / or acoustic alarm device and memory and / or registration means for storing and / or registering the measured values of the pulse frequency and oxygen saturation. The measuring apparatus naturally also has at least one voltage supply device with at least one battery and / or at least one power pack.

The suction means 37 also have a vacuum and separating container 45, which, for example, has an at least partially transparent wall by a removable, for example consisting of a stopper or lid, gas and vacuum tight closure. The closure element 46 or a wall section of the container 45 is provided with two fluid connections 47 and 48, which open into the interior of the container above the bottom of the container 45 and preferably near its upper end. The hose 28 is at least when using the device by the Coupling piece 29 releasably and tightly connected to the fluid connection 47. A hose 50 has a coupling piece 51 and 52 at its two ends and can be detached by this, at least when the device is used, and is tightly connected to the fluid connections 41 and 48, respectively. The fluid connections 41, 47, 48 and the associated coupling pieces 51, 29 and 52 can, for example, be provided with bayonet locking means or other quick locking means. The recess 25 of the sensor 2 can thus be detachably connected to the inlet of the pump 38, at least when the device 1 is used, by means of a fluid passage-limiting connection means, the connection means at least one flexible hose, namely the two arranged one after the other along the fluid passage Have tubes 28, 50.

A living body 61 has a skin 62, a section of which is shown schematically in FIG. 3. The dermis of the skin 62 contains blood vessels, of which an artery or arteriole 63, a vein or venole 64 and some capillary vessels 65 are shown schematically.

The use of the device 1 for the non-invasive measurement of the oxygen saturation of the blood flowing through the blood vessels of the body 61 or - more precisely - arterial blood - and the pulse frequency will now be explained. The drawn skin section can, for example, be a section of the scalp of a fetus or child, whose oxygen saturation and pulse rate are to be measured during and after birth. For the measurement of the oxygen saturation and the pulse frequency, the sensor 2 is connected via the cable 26 to the electronic circuit means 34 and via the hoses 28, 50 and via the container 45 to the pump 37. Furthermore, a doctor or other obstetrician presses the sensor 2 with its on the

Front 4 existing edition 23 manually and / or possibly with the help of an instrument to a surface area of the body 61. This surface area, which belongs to the head of the fetus or child, for example, is normally not flat, but is curved in at least one section through axis 3 and, for example, in all sections through axis 3, the curvature in different sections through axis 3 trending cuts can be different. The surface area covered by the sensor 2 can, for example, have a more or less smooth, convexly curved shape. When the sensor 2 is pressed against the body 61, the support 8 is deformed and, in particular, bent such that the lips 8f and 8g of the support 8 belonging to the support 23 rest on the body 61 along the entire circumference of the lip despite the curved surface of the body 51 .

The body 61 of a fetus or child is in a moist environment at birth and has a moist surface. If the sensor 2 is attached to the body 61 of a fetus or child during childbirth, a liquid containing blood and / or other components, for example, may therefore get into the annular groove 8b or recess 25. When the sensor 2 then rests with its support 23 on the body 61, the recess 25 delimited on the inside by the inner lip 8f and enclosed on the outside by the outer lip 8g forms a cavity which is closed to the environment to some extent or is completely gastight. This contains a fluid, namely air and / or possibly a liquid. A person can now bring the measuring apparatus 31 into an operating state by actuating an operating element, in which the pump 38, via a passage of the three-way valve 40, the container 45 and the hoses 28, 50, produces a fluid which normally consists of air and possibly a little liquid Sucks out recess 25. The pressure of the fluid present in the recess 25, in the hoses 28, 50 and in the container 45 is thereby reduced by a differential pressure below that in the Surrounding the sensor 2 prevailing air pressure lowered. The pressure sensor 40 is designed, for example, to measure the differential pressure between the ambient air pressure and the pressure in the fluid passage connecting the inlet of the pump 38 to the recess 25 of the sensor 2 and to generate an electrical signal that is a measure of gives this differential pressure. The control means belonging to the electronic circuit means 34 control the motor 38 of the pump 38 during said operating state on the basis of the differential pressure measured with the pressure sensor 40 by switching the motor 38a on and off and possibly by changing the speed of the latter such that the said differential pressure is regulated to a predetermined, constant setpoint or is at least within a predetermined setpoint range with constant limit values. This setpoint or setpoint range of the differential pressure can preferably be set manually with at least one control element belonging to the measuring apparatus 31 - for example a rotary resistor and / or at least one push button. The differential pressure between the ambient air pressure and the fluid pressure in the annular groove 8b or recess 25 is approximately with suction pump 38, ie, except for a small pressure drop, equal to the differential pressure measured by the pressure sensor 40 and - when the latter reaches the intended setpoint has - with the pump stopped, exactly the same as the differential pressure measured by the pressure sensor. The fluid pressure in the annular groove 8b or recess 25 is therefore at least approximately smaller than the air pressure in the vicinity of the sensor 2 by means of the differential pressure regulated with the aid of the regulating means. The regulating means can regulate the pressure, for example, in such a way that that of the pressure sensor 40 measured differential pressure and the differential pressure between the surroundings of the sensor 2 and the annular groove 8b or recess 25 is preferably at least 5 kPa, preferably at most 30 kPa and for example approximately 10 kPa to 20 kPa. If the pressure in the recess 25 is lower than the ambient air pressure by the intended differential pressure, the obstetrician can let go of the sensor 2. The air pressure present in the vicinity of the sensor or - more precisely - the mentioned differential pressure then generates a pressure force pressing the sensor 2 against the surface of the body 61, which detachably holds the sensor 2 on the body 61.

The pressure force exerted on the sensor 2 by the air pressure holds the pressure previously applied by the sensor

Elastic deformation of the support 8 produced more or less upright and can possibly also elastically deform the support 8. The two lips 8f, 8g are already spread apart from one another when the sensor 2 is pressed onto the body 51 manually and / or possibly with the aid of an instrument, or afterwards when air is sucked out and liquid is also occasionally spread out from the recess 23, as shown in FIG. 3 is drawn. The inner lip 8f is bent towards its free end against the axis 3, while the outer lip 8g is bent outwards towards the free end of the axis 3.

The result of the pressure force exerted on the sensor 2 by the ambient air pressure is that the sensor 2 in turn exerts a pressure force on the skin 62 of the body 61 on its surfaces resting on the body 61. As a result, the skin 62 is indented and compressed, in particular in the case of the lips 8f and 8g, against the interior of the body 61. The area of the skin 62 enclosed by the inner lip 8f then penetrates into the recess 24 of the sensor 2, so that it may also rest on the skin 62 with the front surfaces of the carrier 14 and the light-emitting diodes 15. Furthermore, the annular region of the skin 62 located between the two lips 8f, 8g is sucked into the annular groove 8b, so that the sensor, for example, also with the shoulder surface of the outer portion 8d delimiting the deepest point thereof Supports 8 and with the front surfaces of the photo semiconductor 20 rests on the skin 62. Furthermore, the sensor can possibly also rest on the skin 62 with the mutually facing side surfaces of the two lips 8f, 8g. However, the skin penetrates at most slightly into the inner section 8c of the annular groove 8b, so that the inner section 8c remains at least largely free (from skin). The support 23 of the sensor 2 is therefore significantly larger when the sensor 2 is pressed against the body 61 and has a deformed support 8 than the support with which the sensor 2 rests on a flat counter surface in the absence of a compressive force and accordingly when the support 8 is relaxed and not deformed. Furthermore, the volume of the free - ie no solid material, but only air-containing part of the annular groove 8b and the annular part formed by it

Recess 25 when the sensor is pressed against the skin is smaller than the volume of the annular groove 8b with undeformed support. Furthermore, the skin in the area of the annular groove does indeed form a bead protruding into it. However, this is relatively flat and hardly forms kinks or edges.

If the fluid sucked out of the annular groove 8b or recess 25 and the hose 26 contains a liquid in addition to air, this liquid is separated from the air in the container 45, so that liquid 69 collects in the originally empty container 45. Otherwise, a filter or the like, which is not shown, can be arranged between the container 45 and the pump 38 or between the latter and between the latter and the air outlet opening into the environment, in order to separate any liquid droplets present in the air sucked out of the container from the air and collect. The vacuum and separating container 45 therefore forms, together with the filter separating means which may still be present, in order to pump liquid together with air out of the annular groove 8b or recess 25 separate from the air so that the air flowing into the pump 38 and then into the environment is free of liquid.

The interior of the vacuum and separating container 45 preferably has a volume which is substantially larger than the volume of the annular groove 8b or recess 25. The container 45 therefore forms a "vacuum reservoir" to a certain extent and can, for example, be used in the event of a temporary leak the sensor 2 and the surface of the body 61 in the annular groove 8b or. Recess the recess 25 penetrating air temporarily, and thereby compensate for pressure fluctuations.

A pressure in the annular groove 8b or recess 25, for example 10 kPa to 20 kPa below the ambient air pressure, is normally sufficient, according to the tests carried out, so that the ambient air pressure or differential pressure keeps the sensor 2 firmly on the body 61 during a whole birth . If the sensor 2 exceptionally - for example because of a force acting on it from the outside and directed away from the surface of the body 61 - but from

Body 61 releases, the obstetrician can easily put the sensor 2 back on the surface of the body 61 and, if necessary, set a larger differential pressure between the surroundings and the annular groove 8b or recess 25.

The measuring apparatus 31 can, for example, be designed in such a way that after the sensor 2 has been attached to the body 61 and the pressure in the annular groove 8b or recess 25 has been reduced by actuating an operating element, the person can actually start the measuring process during which the pulse frequency and the oxygen saturation is measured. However, the measuring apparatus 31 can instead be designed in such a way that the device 1, in the operating state switched on to start the suction process, starts the measuring process automatically after the sensor 2 has been attached to the body 61, ie without actuating an operating element. During the hessing process, the electronic circuit means 34 of the measuring apparatus 31 lead the two light-emitting diodes 15 alternately via the cable 26 to electrical signals, i. H . Voltage pulses so that the two light-emitting diodes alternately generate light signals, ie light pulses, and radiate into the skin 62. The frequency of these light signal sequences should be substantially greater than the human heartbeat or pulse frequency and should be, for example, at least 50 Hz. The light radiated into the skin 62 is scattered and / or absorbed therein, in particular light being also absorbed by the hemoglobin of the blood. Part of the light is again radiated out of the body 61 and into the photo semiconductor 20. The area of the body that the light traverses or shines through forms its measuring area in which the oxygen saturation is measured.

The arterial, oxygen-rich blood flows pulsating through the blood vessels of the body 61, whereas the venous, oxygen-poor or oxygen-free blood flows almost uniformly through the blood vessels. Accordingly, the volume and the amount of arterial, oxygen-rich blood change periodically in time in the measuring range of the body 61, and in particular of the skin 61 thereof, measured by the sensor 2 during measurement, in contrast to the pulse frequency, whereas the volume and the amount of the venous, oxygen-poor or oxygen-free blood remain approximately constant over time in the area of the body 61 mentioned. The light radiated back from the body 61 into the photo semiconductors 20 is modulated with the pulse frequency of the blood flowing through the detected area of the body 61. The photo semiconductors 20 then generate electrical signals, namely voltage pulses or a pulsating DC voltage. These signals are conducted via cable 26 to electronic circuitry 34. The electronic circuit means 34 and the display device 35 are designed to remove from the photo semiconductor 20 in electrical signals converted light to determine and display the pulse frequency t and the oxygen saturation SA of the arterial blood virtually continuously. In order to achieve a high measurement accuracy, it is advantageous that at least the light with one of the two wavelengths and, for example, the light with both wavelengths, of the light entering the photo semiconductors 20 has as large a portion as possible that changes with the heartbeat or pulse frequency over time.

As already mentioned, the sensor 2 exerts a compressive force on the skin 62. The size and the distribution of this compressive force over the various surface areas of the sensor 2 which are in contact with the skin 62 depends on the shape and dimensions of the support 8, on the elastic modulus of the rubber-elastic material forming the support 8, and on the size of the surface of the sensor which is on the skin Sensor and from the pressure in the annular groove 8b or the recess 25. If the last-mentioned pressure is below the ambient air pressure by a differential pressure of at most 30 kPa and, for example, 10 kPa to 20 kPa, the pressure exerted on the skin by the sensor is at least in the case of those located outside the inner section 8c of the annular groove 8b sections of the support 23 of the sensor lying on the skin are smaller than the systolic and also the diastolic blood pressure. Possibly the pressure exerted by the sensor within the portion of the pad 23 enclosed by the inner lip 8f and perhaps even the pressure exerted on the skin by the inner lip 8f is less than the systolic and even less than the diastolic blood pressure. The blood therefore flows pulsating through the blood vessels present in the skin at least in the area of the skin 62 located opposite the photo semiconductors 20 and possibly even in the entire area of the skin 62 covered by the sensor. When the pressure in the annular groove 8b or recess 25 is, for example, about 10 kPa to 20 kPa below the ambient air pressure, is the proportion of the light changing in time with the heartbeat or pulse frequency of the total light entering the photo semiconductor 20 according to the performed examinations larger than if the sensor 2 lies more or less without pressure on the skin. This has a favorable effect on the measurement accuracy, so that the pressure force exerted on the skin by the air pressure via the deformable support therefore also results in an improvement in the measurement accuracy.

Oxygen saturation and pulse rate in a fetus or child during childbirth are usually in the range of approximately 50% to 60% and 100 / min, respectively. up to 150 / min. The electronic circuit means 34 are preferably designed and / or programmed to monitor the oxygen saturation and possibly also the pulse frequency during the measurement. The switching means 34 can then generate a visually recognizable and / or audible alarm signal via an optical and / or acoustic alarm device, for example if the oxygen saturation falls below a predetermined, preferably adjustable, lower limit value. Furthermore, an alarm signal can possibly also be generated if the pulse frequency falls below a lower limit value or exceeds an upper limit value. If a limit value is exceeded or fallen short of, an obstetrician can then take countermeasures to avoid damage.

If the measurement of the oxygen saturation and the pulse frequency is to be ended, an obstetrician or another person can end the measuring process by actuating at least one operating element of the measuring apparatus 31, switch off the motor 38a of the pump 38 and furthermore adjust the three-way valve 39 in this way, that the faucet has the air inlet 42 via a passage of the faucet with the container 45 and over this connects with the annular groove 8b or recess 25. The container 45 and the annular groove 8b or recess 25 are thereby aerated. Accordingly, the pressure force exerted on the sensor 2 by the ambient air pressure or the aforementioned differential pressure disappears. The sensor can now without any noteworthy

Exertion of force can be removed from the body 61 or - if appropriate - even falls off the body 61 as a result of gravity.

The device 1 can of course not only be used for a measurement on a fetus or child, but also for a measurement on an adult person.

The setup can also be changed in several ways. For example, the sensor can also be equipped with means to heat the measuring area of the living body, which is optically recorded when measuring the oxygen saturation, in order to promote blood circulation.

Furthermore, the light radiation means can have three or more

Have light emitting diodes and then possibly generate light with three or more different wavelengths during operation. Furthermore, the light receiving means can have more or less than six photo semiconductors.

In addition, the positions of the light-emitting diodes and photo semiconductors can be interchanged. H. Arrange at least one photo semiconductor in the center of the front of the sensor and provide a ring of light-emitting diodes distributed around the inner section 8c of the annular groove 8b.

The three-way valve 39 can be replaced by other shut-off and / or bypass means which have a passage which can be shut off or released and connects the air inlet 42 with the annular groove 8b or recess 25 of the sensor 2. The three-way year. 39 can be replaced, for example, by two taps connected to branches of a line, each having only one passage, or by at least one electrically controllable valve.

The pressure sensor 40 may possibly measure the value of the pressure in the fluid passage connecting the pump to the recess 25 instead of the differential pressure described. The regulating means can then regulate the pressure in the fluid passage instead of the differential pressure.

Furthermore, one could possibly still connect the inlet of the pump 38 to a chamber serving as a "vacuum reservoir" and provide an electrically controllable metering valve between it and the fluid connection 4. The control means belonging to the electronic circuit means could then control the metering valve in addition to or instead of the motor 38a to regulate the pressure.

Furthermore, the device can possibly be designed to measure, in addition to the oxygen saturation and the pulse frequency or possibly instead of these measurement variables, at least one other gas saturation or the concentration of a dye injected into the blood for diagnostic purposes or another property of a living body non-invasively.

Claims

PATENT CLAIMS

1. Device for measuring at least one property of a living body (61), in particular for the non-invasive measurement of the oxygen saturation of blood present in the body (61), with a front side (4), in this case for lying on the body (61 ) specific sensor (2), light radiation means (13) and light receiving means (19) being present in order to emit light into the body (61) at at least one light emission point and at least one light receiving point on the front side (4) of the sensor (2) to radiate or receive light reflected therefrom, the sensor (2) having an annular groove (8b) on the front side and suction means (37) being present in order to maintain the fluid pressure in the annular groove (25) on the body (61) to lower the sensor (2) lying under the air pressure prevailing in the vicinity of the latter, characterized in that at least a section (8c) of the annular groove (8b) is a top view of the front side (4th ) is arranged between the or each light emitting point and the or each light receiving point.

2. Device according to claim 1, characterized in that the sensor (2) an annular, to rest on the body (61) determined, elastically deformable, in a plan view of the front (4) between the or each light emission point and the or each section of the light receiving area and an annular, elastically deformable section intended for resting on the body (61) and enclosing the annular groove (8b) in the above view. - t

3. Device according to claim 2, characterized in that the sensor (2) has a rubber-elastic support (8) which is provided with the annular groove (8b) and the two annular, elastically deformable intended to rest on the body (61) Forms sections.

4. Device according to one of claims 1 to 3, characterized in that the or jeoe light emission point is enclosed in a plan view of the front (4) of the annular groove (8b) and that several are outside of the said section (8c) of the annular groove (8b) are located around the said section (8c) of the annular groove (8b) around the light receiving points.

5. Device according to one of claims 1 to 4, characterized in that said section (8c) of the annular groove (8b) forms the deepest section of this.

6. Device according to one of claims 1 to 5, characterized in that the light radiation means (13) in the support

(8) have light-emitting diodes (15) and that the light-receiving means (19) have at least one photo semiconductor (20) held in the support (8), that each light-radiation point is formed by a light-emitting diode (15) and that the or each light-receiving point through a photo semiconductor

(20) is formed.

7. Device according to claim 6, characterized in that the annular groove (8b) encloses an axis (3) and, in addition to said inner section (8c), also has an outer section (8d) which is further on from the axis (3rd ) remote side of the inner section (8c) together with this forms a shoulder that the photo semiconductors (20) on the side of the inner section (8c) further away from the axis (3) behind the outer section (8d) of the annular groove (8b ) arranged in the support (8) and by a free The space is separated from a flat, in the case of undeformed support (8) on the front side (4) of the sensor (2) which fits against the support (b).

8. Device according to one of claims 1 to 7, characterized in that the suction means (37) have a pump (38) which is arranged outside the sensor (2) and via at least one flexible hose (28, 50) having connecting means with the Ring groove (8b) is connected.

I C

9. The device and claim 8, characterized in that a pressure sensor (40) and control means connected to the latter are provided to determine the differential pressure between the surroundings of the sensor (2) and the annular groove (8b) or the pressure

15 in the latter to regulate to a value which is constant or lies within a range with constant limit values.

10. Device according to claim 8 or 9, characterized in that the pump (37) is gas-tight against the

The interior of a container (45), which is closed off from the outside, is connected to the annular groove (8b) and that the container (45) is designed to separate and collect liquid (69) pumped out of the annular groove (8b).

25

11. Device according to one of claims 1 to 10, characterized in that an air inlet (42) is present, which is connected via an optionally lockable or unlockable passage with the annular groove (8b) of the sensor (2).

30

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