WO2025256856A1

WO2025256856A1 - Apparatus for blood pressure estimation

Info

Publication number: WO2025256856A1
Application number: PCT/EP2025/063345
Authority: WO
Inventors: Tiago DE FREITAS PEREIRA; Johannes Haase
Original assignee: Ams Osram AG
Current assignee: Ams Osram AG
Priority date: 2024-06-10
Filing date: 2025-05-15
Publication date: 2025-12-18
Anticipated expiration: 2026-12-10

Abstract

An apparatus (1) for blood pressure estimation comprises at least one emitter device (10) for emitting light into the skin (2) of a body, at least two receiver devices (20a, 20b, 20c) being arranged for receiving light reflected from different depths of the body, and a controller device (30). A first one and a second one of the at least two receiver devices (20a, 20b) are configured to provide a first and a second receiver output signal (S1, S2) in response to received light portions (L1, L2) reflected from tissue layers (2a, 2b) in different depth of the body. The controller device (30) is configured to provide an output signal (OS) representing an estimation of the blood pressure in the body by evaluating a phase delay between the first and second receiver output signals (S1, S2).

Description

APPARATUS FOR BLOOD PRESSURE ESTIMATION

Technical Field

The disclosure relates to an apparatus for blood pressure estimation by analyzing a pulse wave generated by the blood flow in the body .

Background

Blood pressure measurement is essential for recogni zing cardiovascular diseases . In the classic method of measuring blood pressure , a cuf f is placed around the upper arm of a patient and inflated with air to block the blood flow so that blood no longer flows in the upper arm artery . The air in the cuf f is then released and the blood pressure is measured using a pressure gauge , which measures the current air pressure in the cuf f , and a stethoscope/microphone to listen to the sound of the blood flowing in the brachial artery to detect the heart rate . However, the measurement equipment is bulky and only allows for point measurements . Furthermore , continuous measurements are not easily possible .

Digital blood pressure monitors use non-invasive pulse wave analysis to determine the central blood pressure in the aorta . With every heartbeat , a complex pulse wave is generated that spreads from the heart to the extremities with a particular pulse wave velocity ( PWV) . Analyzing the pulse wave velocity is a well-known method for cuf fless blood pressure estimation . Current cuf fless blood pressure estimations rely on the synchroni zation of pulse waves measured on di f ferent positions of the body of a patient . Cuf fless blood pressure estimations thus use the pulse wave velocity by synchroni zing pulse arrivals at di f ferent positions on the body . The pulse wave can be measured via electrocardiography (ECG) or photoplethysmography ( PPG) .

It would be welcome in the art to provide an apparatus for blood pressure estimation which is very compact and yet enables a reliable estimation of the blood pressure .

Summary

An apparatus for blood pressure estimation that has a small package and can be attached to the body of a patient in one place , and yet allows the blood pressure to be measured with high accuracy is speci fied in claim 1 .

The apparatus for blood pressure estimation comprises at least one emitter device for emitting light into the skin of the body . The apparatus further comprises at least two receiver devices being arranged for receiving light reflected from di f ferent depths of the body . The apparatus further comprises a controller device .

A first one of the at least two receiver devices is configured to provide a first receiver output signal in response to a received first light portion of the light reflected from a first tissue layer in a first depth of the body in relation to the surface of the skin . A second one of the at least two receiver devices is configured to provide a second receiver output signal in response to a received second light portion of the light reflected from a second tissue layer in a second depth of the body in relation to the surface of the skin . The second depth of the body is di f ferent from the first depth of the body . The controller device is configured to provide an output signal representing an estimation of the blood pressure in the body by evaluating a phase delay between the first receiver output signal and the second receiver output signal .

With every heartbeat , the heart pumps blood to the periphery of the body . The resulting pulse wave distends the arteries and veins . The change in volume of the blood flowing in the blood vessels which is caused by the pulsating blood flow can be seen in a photoplethysmogramm ( PPG) by small peaks . The blood volume changes due to the pulsating blood flow are detected by illuminating the skin of the body with light from the at least one light emitter device , for example a lightemitting diode , and then measuring the amount of light scattered back and reflected from the blood volume to the at least two receiver devices . Depending on the back scattering blood volume , the respective receiver output signal of the at least two receiver devices increases or decreases , and therefore depicts the pulse wave .

The receiver output signals generated by the at least two receiver devices from light reflected at capillary blood vessels in shallow tissue/ skin layers show a phase delay in relation to the receiver output signals which are generated by the at least two receiver devices from light reflected at a pulse wave generated for each cardiac cycle in deeper tissue/ skin layers . The proposed approach of the apparatus for blood pressure estimation is based on optical depth sensing . The phase delay between the receiver output signals provided by the at least two receiver devices by detecting light reflected at di f ferent layers in the depth profile of the skin of a patient from deep to shallow tissue/ skin layers is evaluated by the controller device to estimate the blood pressure .

The phase delay between the first receiver output signal and the second receiver output signal represents a time delay between the reflection of light at a pulse wave in the first tissue layer, i . e . a shallow tissue layer, and the reflection of light at the pulse wave in the second tissue layer, i . e . a deep tissue layer that is further away from the surface of the skin than the first tissue layer .

The pulse wave generated by a cardiac cycle first reaches the arteries/veins in the deeper tissue layers and then spreads via the finer arteries/veins to the capillaries in the tissue or skin layers closer to the surface of the skin . This results in a time delay between the pulse wave in the deeper tissue or skin layers and the occurrence of the pulse wave in the upper tissue or skin layers .

I f the first receiver device detects the pulse wave in the first , for example the upper, skin or tissue layer, and the second receiver detects the pulse wave in the second, for example the deeper, skin or tissue layer, a phase of fset occurs between the first receiver output signal ( first PPG signal ) and the second receiver output signal ( second PPG signal ) . The higher the blood pressure , the faster the pulse wave reaches the upper tissue or skin layers .

By analyzing the time of fset between the pulse wave traveling in the deeper skin or tissue layer and the pulse wave traveling in the capillaries closer to the surface of the skin, and thus by analyzing the phase of fset between the first receiver output signal provided by the first receiver device and the second receiver output signal provided by the second receiver device , the controller can determine or estimate the blood pressure that correlates with the phase of fset between the receiver output signals of the at least two receiver devices .

As explained above , the proposed approach uses the phase delay of a pulse wave from deep to shallow skin/tissue layers for blood pressure estimation . According to a further embodiment , the apparatus for blood pressure estimation may use additional information, for example from electrocardiography and/or from a pulse form analysis , to evaluate the blood pressure with more reliability .

According to a possible embodiment of the apparatus for blood pressure estimation, the first receiver device and the second receiver device are arranged at di f ferent distances from the at least one emitter device . Depending on the di f ferent distance of the first and second receiver device from the at least one emitter device , optical signals can be received by the first and second receiver devices that have been reflected by tissue or skin layers at di f ferent depths of the skin profile .

According to a possible embodiment of the apparatus for blood pressure estimation, the first receiver device is arranged closer to the at least one emitter device than the second receiver device . With this configuration, it is possible to detect optical signals reflected from blood vessels/capillaries in regions closer to the surface of the skin by the first receiver device , which is positioned closer to the at least one emitter device than the second receiver device . The second receiver device , which is positioned further away from the at least one emitter device , receives optical signals reflected from the blood flow in blood vessels/veins/arteries in deeper tissue or skin layers .

High blood pressure leads to high pulse wave velocity and therefore a small phase delay of the pulse wave from deeper to shallow tissue regions . Low blood pressure leads to low pulse wave velocity and therefore a large phase delay of the pulse wave from deeper to shallow tissue layers . A measurement of optical signals by the first receiver device located at a short distance to the at least one emitter device shows a time delay in the first receiver output signal compared to a measurement of optical signals by the second receiver device located at a greater distance to the at least one emitter device . The time delay between the pulse waves at deep and shallow measurement points , and thus the phase delay between the first and second receiver output signals is dependent on the pulse wave velocity and therefore on the blood pressure .

A plurality of configurations of the at least one emitter device and the at least two receiver devices is basically possible .

According to an exemplary embodiment of the apparatus for blood pressure estimation, the first receiver device and the second receiver device are arranged on one side or on opposite sides of the at least one emitter device at di f ferent distances from the at least one emitter device . For example , the receiver devices can be arranged in stripes at di f ferent distances on one side or on two opposite sides of the at least one emitter device . According to another exemplary embodiment of the apparatus for blood pressure estimation, the first receiver device can be arranged in a first region circumferentially around the at least one emitter device , and the second receiver device can be arranged in a second region circumferentially around the at least one emitter device . The second region is further away from the at least one emitter device than the first region . The first region, in which the first receiver device is arranged, may form a first frame around the at least one emitter device at a first distance from the at least one emitter device . The second region, in which the second receiver device is arranged, may form a second frame around the at least one emitter device at a second distance from the at least one emitter device , which is further away than the first distance .

According to a possible embodiment of the apparatus for blood pressure estimation, the controller device is configured to change the distance between the at least one emitter device and the first and second receiver device . By changing the emitter-to-sensor distance , the depth of the tissue/ skin layers at which the emitted optical signals are reflected may be adj usted . It is thus possible to receive optical signals reflected in di f ferent depths of the skin so that the time delay of pulse waves from deeper to shallow tissue/ skin regions can be analyzed .

According to a possible embodiment of the apparatus for blood pressure estimation, the at least one emitter device is configured as a light emitter device to emit light , for example , in the visible or infrared range . The at least one emitter device may be configured to emit the light , for example , as green light or in any other wavelength of the visible or infrared range .

The at least one emitter device may comprise at least one light emitting diode ( LED) , for example , a micro light emitting diode (micro LED) .

As a broad definition, a micro LED could be seen as any light emitting diode ( abbreviated to "LED" ) - generally not a laser - with a particularly small si ze .

As a rule - and this is a very important criterion in addition to si ze - micro LEDs have a growth substrate removed, so that typical heights of such micro LEDs are in the range of 1 . 5 pm to 10 pm, for example .

In principle , a micro LED does not necessarily has a rectangular radiation emitting surface . In general , for example , an LED with a radiation emitting surface in which each lateral extension of the radiation emitting surface is less than or equal to 100 pm or less than or equal to 70 pm when viewed from above on the layers of the layer stack could be used .

For example , an edge length of less than or equal to 70 pm or less than or equal to 50 pm is often mentioned as a criterion for rectangular micro-LEDs , especially when viewed from above onto the layers of the layer stack .

In most cases , such micro-LEDs are provided on wafers with non-destructively detachable holding structures for the pLED . Micro-LEDs are currently primarily used in displays . The micro-LEDs form pixels or sub-pixels and emit light of a defined colour . Due to the small pixel si ze and high density with a small distance , micro LEDs are suitable for small monolithic displays for AR applications , in particular data glasses . Other applications are also being worked on, in particular in data communication or pixelated lighting applications .

Various spellings for micro LEDs can be found in the literature , e . g . pLED, p-LED, uLED, u-LED or Micro Light Emitting Diode .

According to a possible embodiment of the apparatus for blood pressure estimation, the at least one emitter device is configured to emit the light with di f ferent emission wavelengths . The at least one emitter device may be configured to generate the light with emission wavelengths so that the light has di f ferent penetration depths into the body or the human tissue . For example , the reflected optical signals from red light originates from deep skin layers , and the reflected optical signals from blue light originates from shallow skin layers .

According to another possible embodiment of the apparatus for blood pressure estimation, the at least one emitter device is configured to change the emission wavelength of the emitted light . Changing the emission wavelength enables to adj ust the penetration depth into the tissue/ skin layers . Moreover, changing the emission wavelength and the emitter- receiver/detector distance allows signal strength and depth sensing accuracy to be optimi zed at the same time . According to a possible embodiment of the apparatus for blood pressure estimation, the at least one emitter device and the at least two receiver devices may be arranged in an array comprising a plurality of light emission areas and light receiving areas with di f ferent distances to the emission areas . The array of emitter and receiver devices can be configured, for example as a smart display . A display with full or partial area in-display fingerprint sensing can for instance be used to monitor PPG heartrate (HR) and blood pressure . The principle can be converted to discrete measurement units that have emitter and receiver/detector units with di f ferent distances .

The apparatus for blood pressure estimation can be integrated into a display of an all-day use device , like , for example , a smartphone or a smartwatch or even be integrated into a wearable wristband . Particular advantages are the absence of a cuf f , the easy integrability into a display or wristband, and the miniaturi ze ability .

Additional features and advantages of the proposed apparatus for blood pressure estimation are set forth in the detailed description that follows . It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework for understanding the nature and character of the claims .

Brief Description of the Drawings

The accompanying drawings are included to provide further understanding, and are incorporated in, and constitute a part of , the speci fication . As such, the disclosure will be more fully understood from the following detailed description, taken in conj unction with the accompanying figures in which :

Figure 1 shows an embodiment of an apparatus for blood pressure estimation by evaluating a phase delay of optical signals reflected at pulse waves from deep to shallow skin/tissue layers ;

Figure 2 illustrates the relationship between a time delay of pulse waves from tissue/ skin layers of di f ferent depths of the body and the value of the blood pressure ;

Figure 3A illustrates an arrangement of at least one emitter device of an apparatus for blood pressure estimation in an emission area and at least two receiver devices of the apparatus for blood pressure estimation in detection areas at di f ferent distances from the emission area ;

Figure 3B shows a first and second receiver output signal of a first and second receiver device of an apparatus for blood pressure estimation having a phase delay used for blood pressure estimation;

Figure 4 shows possible configurations of an emitter device and receiver devices arranged at di f ferent distances from the emitter device ; and

Figure 5 shows an embodiment of an apparatus for blood pressure estimation with generation of optical signals of di f ferent wavelengths and reception of optical signals reflected at tissue layers located in di f ferent depths of a skin profile to estimate the blood pressure .

Detailed Description of the Drawings

Figure 1 shows an embodiment of an apparatus 1 for blood pressure estimation which comprises at least one emitter device 10 for emitting light into the skin 2 of a body . The apparatus 1 further comprises at least two receiver devices , which are shown in Figure 1 as receiver devices 20a, 20b, and 20c . The receiver devices are arranged for receiving light reflected from tissue layers 2a, 2b, 2c in di f ferent depths of a skin profile . The apparatus 1 further comprises a controller device 30 to evaluate output signals from at least two of the receiver devices 20a, 20b, 20c to estimate the blood pressure in the body .

Referring to Figure 1 , the at least one emitter device 10 emits light in the skin profile 2 which is scattered back from the blood volume in tissue/ skin layers 2a, 2b, 2c of di f ferent depths of the skin profile towards the receiver devices . As shown in Figure 1 , a light portion LI of the light emitted by the at least one emitter device 10 is reflected by the blood volume in capillaries 4 of a shallow tissue/ skin layer 2a, and light portions L2 , L3 of the light emitted by the at least one emitter device 10 are reflected by the blood volume in blood vessels/veins/arteries 5 of a deeper tissue/ skin layers 2b, 2c .

Receiver device 20a is configured to provide a first receiver output signal S I in response to the received light portion LI of the light reflected from tissue layer 2a in a first depth of the body in relation to the surface 3 of the skin 2 . Receiver device 20b is configured to provide a second receiver output signal S2 in response to the received light portion L2 of the light reflected from tissue/ skin layer 2b in a second depth of the body in relation to the surface 3 of the skin 2 , and receiver device 20c is configured to provide a third receiver output signal S3 in response to the received light portion L3 of the light reflected from tissue/ skin layer 2c in a third depth of the body in relation to the surface 3 of the skin 2 . As shown in Figure 1 , the second depth of tissue/ skin layer 2b is di f ferent from the first depth of tissue/ skin layer 2a, and the third depth of tissue/ skin layer 2c is di f ferent from the first and second depths of tissue/ skin layers 2a and 2b with respect to the surface 3 of the skin 2 .

As a result of a heartbeat , a pulse wave is generated in the blood vessels 5 , which propagates away from the heart into the periphery of the body on the one hand, and from a blood vessel 5 in a deeper tissue/ skin layers 2b or 2c into the capillaries 4 in a shallow tissue/ skin layer 2a that is closer to the skin surface 3 on the other hand . A pulse wave in the capillary 4 in shallow tissue/ skin layer 2a shows a time delay with respect to the pulse wave flowing in blood vessel 5 in deeper tissue/ skin layers 2b or 2c and generated by the same cardiac cycle .

Figure 2 illustrates the time delay of pulse waves generated by the same cardiac cycle in blood vessels/capillaries of tissue/ skin layers in di f ferent depths of a skin profile . The blood pressure has an influence on the pulse wave velocity . As illustrated in Figure 2 , a high blood pressure leads to high pulse wave velocity and therefore a small time delay of the pulse wave from deeper to shallow tissue/ skin regions of the skin profile . A low blood pressure leads in turn to low pulse wave velocity and therefore a large time delay of the pulse wave from deeper to shallow tissue/ skin regions in the skin profile .

As shown in Figure 1 , the receiver devices 20a, 20b and 20c are arranged in relation to the at least one emitter device 10 in such a way that they receive light portions of the emitted light or optical signals that are reflected by the pulse waves at di f ferent depths of the skin profile . The receiver devices 20a, 20b and 20c generate output signals S I , S2 and S3 as a function of the received light portions or optical signals .

The light receiver devices 20a, 20b and 20c may be configured to generate the receiver output signals S I , S2 and S3 as PPG signals which show blood volume changes due to the pulsating blood flow . As a result of the time of fset/time delay between the pulse waves that propagates from the deeper tissue/ skin layers to the shallow tissue/ skin layers , and thus the time delay between the reflected light portions from tissue/ skin layers in di f ferent depths of the skin profile , the receiver output signals S I , S2 and S3 of the receiver devices 20a, 20b and 20c are generated with a phase of fset/phase delay to each other .

The controller device 30 is configured to evaluate the phase delay between at least two of the receiver output signals S I , S2 and S3 , and to provide an output signal OS in dependence on the evaluation of the phase delay . The output signal OS represents an estimation of the blood pressure in the body . The phase delay between at least two of the receiver output signals S I , S2 and S3 of the light receiver devices 20a, 20b and 20c represents the time delay between the reflection of light at a pulse wave in a shallow tissue/ skin layer, for example tissue/ skin layer 2a, and the reflection of light at the pulse wave in a deeper tissue/ skin layer, for example tissue/ skin layer 2b or 2c, with respect to the surface 3 of the skin 2 .

The phase delay between at least two of the output signals S I , S2 and S3 is dependent on the pulse wave velocity and therefore on the blood pressure . In particular, the phase delay from shallow to deep tissue/ skin layers correlates to the systolic blood pressure and can therefore be used by the controller device 30 to estimate the blood pressure and to generate the controller output signal OS with a value representing the determined blood pressure level .

According to the proposed approach, the apparatus 1 for blood pressure estimation provides a blood pressure estimation via depth sensing . The controller device 30 is configured to determine the blood pressure from the measured phase of fset/phase delay between at least two of the receiver output signals S I , S2 and S3 of the light receiver devices 20a, 20b and 20c .

Nevertheless , output signals from other sensors or information from other measurements , for example from an electrocardiography measurement and/or from pulse form analysis , can also be taken into account by the controller device 30 for determining the blood pressure value in order to increase the accuracy of the estimate . For example , the controller device 30 may be configured to provide the output signal OS by evaluating sensor signals received from an electrocardiography measurement and/or by performing a pulse form analysis from received PPG signals , for example from the receiver output signals .

The di f ferent depths for measuring the reflected light portions LI , L2 and L3 can be resolved by measuring the reflected light portions at di f ferent emitter-receiver distances . To get a reading of the phase delay, a minimum of two di f ferent measurement point distances to the at least one emitter device 10 is needed .

Figure 3A shows receiver device 20a and receiver device 20b being arranged at di f ferent distances from the at least one emitter device 10 . The at least one emitter device 10 is arranged in an emission area E . Receiver device 20a is arranged in a detection area DI being closer to the emission area E of the at least one emitter device 10 than receiver device 20b which is arranged in a detection area D2 . A short distance between the at least one emitter device 10 and one of the receiver devices 20a, 20b and 20c corresponds to a reflected light signal originating from shallow tissue/ skin layers . A long distance between the at least one emitter device 10 and one of the receiver devices 20a, 20b and 20c corresponds to a signal originating from deep tissue/ skin layers .

The measuring depth can be tuned by increasing or decreasing the distance of the light receiver devices from the at least one light emitter device . For this purpose , according to a possible embodiment of the apparatus for blood pressure estimation, the controller device 30 may be configured to change the distance between the at least one emitter device and the light receiver devices . Figure 3B illustrates the phase delay between the receiver output signal/PPG signal S I of the receiver device 20a and the receiver output signal/PPG signal S2 of the receiver device 20b that may be used by the controller device 30 to provide the output signal OS with a value representing the estimation of the blood pressure . The phase delay between receiver output signal S I generated, for example , from the reflection of light portion LI at a pulse wave measured in shallow tissue/ skin layer 2a and receiver output signal S2 generated, for example , from the reflection of light at a pulse wave measured in deep tissue/ skin layer 2b is proportional to the pulse wave velocity and therefore the blood pressure .

Figure 4 shows examples of possible arrangements of an emitter device 10 to receiver devices 20a, 20b and 20c at di f ferent distances from the emitter device 10 .

According to a possible configuration shown on the left side of Figure 4 , the receiver devices 20a, 20b and 20c are arranged on one side or on opposite sides of the at least one emitter device 10 at di f ferent distances from the at least one emitter device 10 . The receiver devices 20a, 20b and 20c can be arranged in strip-shaped areas at di f ferent distances from the at least one emitter device 10 .

Referring to the right side of Figure 4 , the receiver devices 20a, 20b and 20c are arranged circumferentially around the at least one emitter device 10 . Receiver device 20a is , for example , arranged in a region R1 circumferentially around emitter device 10 . Receiver device 20b is arranged in a region R2 circumferentially around emitter device 10 , and receiver device 20c is arranged in a region R3 circumferentially around emitter device 10 . Region R2 is further away from the at least one emitter device 10 than region Rl , and region R3 is further away from the at least one emitter device 10 than region R2 .

The embodiments shown in Figure 4 are only exemplary arrangements of an emitter device with receiver devices that are arranged at a respective distance from the receiver and at a respective distance from each other . In principle , lots of arrangements in which a plurality of N receivers is arranged at N di f ferent distances from each other and from the emitter device are possible . According to an embodiment , a periodical arrangement of receiver devices being located spaced apart from the emitter device is possible . For example , an arrangement in which the pitch between adj acent receiver devices is equal enables to double the distance between the emitter device and the adj acent receiver devices , and thus to double the penetration depth detected by the adj acent receiver devices .

Figure 5 shows an embodiment of the apparatus 1 for a blood pressure estimation which advantageously utili zes the fact that light of di f ferent wavelengths penetrates the tissue layers to di f ferent depths and is therefore reflected by tissue/ skin layers of di f ferent depths . Reflected light signals from red/blue light , for example , originate from deep/ shallow tissue or skin layers .

According to the proposed approach of the apparatus for blood pressure estimation shown in Figure 5 , the at least one emitter device 10 is configured to emit the light with di f ferent emission wavelengths XI , X2 , A3 . The at least one light emitter device may comprise a first light emitter device 10a for emitting light with a first wavelength XI , a second light emitter device 10b for emitting light with a second wavelength X2 and a third light emitter device 10c for emitting light with a third wavelength X3 . As illustrated in Figure 5 , the various wavelengths of the light are selected to enable a di f ferent penetration depth of the emitted light into the tissue of a body or into the skin layers of the skin profile .

According to an advantageous embodiment , the at least one emitter device 10 may be configured to change the emission wavelength of the emitted light . The light receiver devices 20a, 20b, 20c located at di f ferent distances from the at least one emitter device 10 detect the light portions LI , L2 and L3 of di f ferent wavelengths XI , X2 , A3 from di f ferent penetration depths . Changing the emission wavelengths and the emitter-receiver distance allows to optimi ze signal strength and depth sensing accuracy at the same time .

The embodiments of the proposed apparatus for blood pressure estimation disclosed herein have been discussed for the purpose of familiari zing the reader with novel aspects of the blood pressure estimation apparatus . Although preferred embodiments have been shown and described, many changes , modi fications , equivalents and substitutions of the disclosed concepts may be made by one having skill in the art without unnecessarily departing from the scope of the claims .

In particular, the design of the proposed apparatus for blood pressure estimation is not limited to the disclosed embodiments , and gives examples of many alternatives as possible for the features included in the embodiments discussed . However, it is intended that any modi fications , equivalents and substitutions of the disclosed concepts be included within the scope of the claims which are appended hereto . Features recited in separate dependent claims may be advantageously combined . Moreover, reference signs used in the claims are not limited to be construed as limiting the scope of the claims . Furthermore , as used herein, the term "comprising" does not exclude other elements . In addition, as used herein, the article "a" is intended to include one or more than one component or element , and is not limited to be construed as meaning only one .

This patent application claims the priority of German patent application with application No . 102024116128 . 0 , the disclosure content of which is hereby incorporated by reference .

References

1 apparatus for blood pressure estimation

2 skin

3 surface of the skin

4 capillary

5 blood vessel

10 emitter device

20a, 20b, 20c receiver device

30 controller device

2a, 2b, 2c tissue/ skin layer

S I , S2 , S3 receiver output signal

OS output signal from controller device

LI , L2 , L3 reflected light portion

Claims

1. An apparatus for blood pressure estimation, comprising:

- at least one emitter device (10) for emitting light into the skin (2) of a body,

- at least two receiver devices (20a, 20b, 20c) being arranged for receiving light reflected from different depths of the body,

- a controller device (30) ,

- wherein a first one of the at least two receiver devices (20a) is configured to provide a first receiver output signal (SI) in response to a received first light portion (LI) of the light reflected from a first tissue layer (2a) in a first depth of the body in relation to the surface (3) of the skin (2) ,

- wherein a second one of the at least two receiver devices (20b) is configured to provide a second receiver output signal (S2) in response to a received second light portion (L2) of the light reflected from a second tissue layer (2b) in a second depth of the body in relation to the surface (3) of the skin (2) , the second depth being different from the first depth,

- wherein the controller device (30) is configured to provide an output signal (OS) representing an estimation of the blood pressure in the body by evaluating a phase delay between the first receiver output signal (SI) and the second receiver output signal (S2) .

2. The apparatus of claim 1, wherein the controller device (30) is configured to evaluate the phase delay between the first receiver output signal (SI) and the second receiver output signal (S2) representing a time delay between the reflection of light at a pulse wave in the first tissue layer (2a) and the reflection of light at the pulse wave in the second tissue layer (2b) with respect to the surface (3) of the skin (2) .

3. The apparatus of claim 1 or 2, wherein the second tissue layer (2b) is further away from the surface (3) of the skin (2) than the first tissue layer (2a) .

4. The apparatus of any of the claims 1 to 3, wherein the controller device (30) is configured to provide the output signal (OS) by evaluating signals received from an electro cardiography measurement and/or by analyzing a pulse form of the first and second receiver output signals (SI, S2) .

5. The apparatus of any of the claims 1 to 4, wherein the first receiver device (20a) and the second receiver device (20b) are arranged at different distances from the at least one emitter device (10) .

6. The apparatus of any of the claims 1 to 5, wherein the first receiver device (20a) is arranged closer to the at least one emitter device (10) than the second receiver device (20b) .

7. The apparatus of any of the claims 1 to 6, wherein the controller device (30) is configured to change the distance between the at least one emitter device (10) and the first and second receiver device (20a, 20b) .

8. The apparatus of any of the claims 1 to 7, wherein the first receiver device (20a) and the second receiver device (20b) are arranged on one side or on opposite sides of the at least one emitter device (10) at different distances from the at least one emitter device (30) .

9. The apparatus of any of the claims 1 to 8,

- wherein the first receiver device (20a) is arranged in a first region (Rl) circumferentially around the at least one emitter device (10) ,

- wherein the second receiver device (20b) is arranged in a second region (R2) circumferentially around the at least one emitter device (10) , wherein the second region (R2) is further away from the at least one emitter device (10) than the first region (Rl) .

10. The apparatus of any of the claims 1 to 9, wherein the at least one emitter device (10) is configured to emit the light in the visible or infrared range.

11. The apparatus of any of the claims 1 to 10, wherein the at least one emitter device (10) comprises at least one micro light emitting diode.

12. The apparatus of any of the claims 1 to 11,

- wherein the at least one emitter device (10) is configured to emit the light with different emission wavelengths (XI, X2, X3) ,

- wherein the emission wavelengths (XI, X2, X3) of the light have different penetration depth into the body.

13. The apparatus of any of the claims 1 to 12, wherein the at least one emitter device (30) is configured to change the emission wavelengths (XI, X2, X3) of the emitted light .

14. The apparatus of any of the claims 1 to 13, wherein the at least one emitter device (30) and the at least two receiver devices (20a, 20b) are arranged in an array comprising a plurality of light emission areas and light receiving areas with different distances to the emission areas .

15. The apparatus of claim 14, wherein the array is configured as a smart display.