Pulse oximeter for determining oxygen saturation considering melanin concentration of the skin

Abstract

A pulse oximeter (1) for determining oxygen saturation considering melanin concentration of the skin comprises a light emitter device (10), a light receiver device (20), and an evaluation circuit (30). The light emitter device (10) is configured to emit light (2) for entering the skin (3) with at least three different wavelengths (λ1, λ2, λ3). The light receiver device (10) is configured to detect the light after it emerges from the skin (3). The evaluation circuit (30) is configured to determine the oxygen saturation in the blood (4) in dependence on the detected light (2) of at least one first wavelength (λ1) and at least one second wavelength (λ2) and in dependence on a determined concentration of melanin (5) in the skin (3), wherein the concentration of melanin (5) in the skin (3) is determined in dependence on the detected light (2) of at least one third wavelength (λ3).

Description

[0001] 2022PF01801 May 17, 2024 P2022,2172 WO N - 1 - Description PULSE OXIMETER FOR DETERMINING OXYGEN SATURATION CONSIDERING MELANIN CONCENTRATION OF THE SKIN Technical field The disclosure relates to a pulse oximeter for determining an oxygen saturation in the blood, whereby the influence of the melanin concentration on the result is taken into account or the result is corrected for it. Background Pulse oximetry is a non-invasive method for monitoring a patient’s blood oxygen saturation. The oxygen saturation is measured with the use of a pulse oximeter, which is a particular spectrophotometer designed for this application. The pulse oximeter indirectly monitors the oxygen saturation of a patient’s blood by measuring the light absorption when the skin is illuminated by a light source. The optical measurement principle is based on the fact that haemoglobin loaded with oxygen, so-called oxyhaemoglobin (HbO2), shows a significantly different absorption curve at optical wavelengths than deoxygenated haemoglobin, so called deoxyhaemoglobin (Hb), i.e. haemoglobin whose transport sides of oxygen are still free of oxygen. Figure 1 retrieved and adapted from Mantri et al., Biomed. Opt. Express 13(11) 5683-5694 (2022) shows the absorption spectra of oxygenated haemoglobin (HbO2) and deoxygenated haemoglobin (Hb) in dependence on different wavelengths of light that passes through arterial blood of a body or is 2022PF01801 May 17, 2024 P2022,2172 WO N - 2 - reflected at the arterial blood of the body. When considering the course of the absorption for oxyhaemoglobin and deoxyhaemoglobin, it can be seen that deoxyhaemoglobin has a significantly higher absorption than oxyhaemoglobin at wavelengths of approximately 660 nm which corresponds to visible red light. On the other hand, at longer wavelengths from about 800 nm upwards, this ratio reverses. At approximately 900 nm, the absorption of oxyhaemoglobin is higher and that of deoxyhaemoglobin is lower. Wavelengths above 700 nm are referred to as (near) infrared radiation. A pulse oximeter uses a pair of light-emitting diodes and respective photodiodes which are arranged adjacent or opposite to each other on a target object, for example a finger of a person. In the first case, the photodiodes are used to measure the intensity of the light reflected from the red blood cells. In the second case, the intensity of the light is measured after the light has passed through the body and has been absorbed to a greater or lesser extent by the red blood cells. A conventional pulse oximeter uses a first light-emitting diode which radiates red light with a first wavelength ^1 of, for example about 660 nm, and a second light-emitting diode which emits infrared light with a second wavelength ^2 of, for example about 900 nm. As illustrated in Figure 1, absorption of light at these wavelengths differs significantly between blood loaded with oxygen (oxyhaemoglobin) and oxygen-depleted blood (deoxyhaemoglobin). Oxyhaemoglobin absorbs more infrared light and allows more red light to pass through. Deoxyhaemoglobin allows more infrared light to pass through and absorbs more red light. 2022PF01801 May 17, 2024 P2022,2172 WO N - 3 - The light-emitting diodes are switched on and off cyclically and the amount of the red light and infrared light that is transmitted through the body or reflected within the body, i.e. that is not absorbed by the red blood cells, is measured. For each first and second wavelength, for example ^1 = 660 nm and ^2 = 900 nm, ratios of AC-components and DC- components (baselines) of the detected light AC ^1 / DC ^1and AC ^2 / DC ^2are calculated. Figure 1 illustrates the AC- and DC-components for detected light of the first and second wavelength, for example ^1 = 660 nm and ^2 = 900 nm, for low and high SaO2(actual, arterial blood oxygen saturation) retrieved from Mannheimer, P.: The Light-Tissue Interaction of Pulse Oximetry, Anesthesia & Analgesia 105(6), p S10-S17 (2007). A ratio R of those ratios is then calculated by a processor correlated to the relative concentration of oxyhaemoglobin and deoxyhaemoglobin: The oxygen saturation SpO2(PPG-based, measured blood oxygen saturation)is proportional to R: ^^^2 = ^ + ^^ where the factors α and β are fitting calibration parameters for different SpO2concentrations and depend on the sensor construction. The described technique for measuring oxygen saturation in the blood is influenced by some disturbance variables. An important disturbance that distorts the measurement result 2022PF01801 May 17, 2024 P2022,2172 WO N - 4 - for the oxygen saturation is the concentration of melanin in the skin. In particular, melanin influences the R factor that is part of the calculation of the oxygen saturation in the blood. Conventional pulse oximeters using red light and infrared light for determining the absorption spectra of haemoglobin do not account for the reflection spectra of melanin. The darker the skin and thus the higher the melanin concentration, the more the calculation of the oxygen saturation is influenced and falsified by the melanin concentration. This is why conventional pulse oximeters often indicate incorrect results, especially for dark skinned people. It would be welcome in the art to provide a pulse oximeter for determining oxygen saturation considering melanin concentration of the skin so that the pulse oximeter can reliably provide oxygen saturation with high accuracy. Summary A pulse oximeter for determining the oxygen saturation in a patient’s blood with high accuracy considering melanin concentration is specified in claim 1. The proposed pulse oximeter for determining oxygen saturation comprises a light emitter device and a light receiver device. The light emitter device is configured to emit light for entering the skin, wherein the light is emitted by the light emitter device with at least three different wavelengths including at least a first wavelength, at least a second wavelength and at least a third wavelength. The light receiver device is configured to detect the light after it emerges from the skin. 2022PF01801 May 17, 2024 P2022,2172 WO N - 5 - The pulse oximeter comprises an evaluation circuit to evaluate the detected light for determining the oxygen saturation in the blood. The evaluation circuit is configured to determine the oxygen saturation in the blood in dependence on the detected light of the at least one first wavelength and the at least one second wavelength, and in dependence on a determined concentration of melanin in the skin. The evaluation circuit is configured to determine the concentration of melanin in the skin in dependence on the detected light of the at least one third wavelength. The fact that spectra, and therefore melanin, vary greatly among people and even within a single person, reinforces the necessity for point-of-contact calibration for skin tone and the importance of using a multi-wavelength approach of a pulse oximeter beyond the conventional two wavelengths approach. According to the proposed approach of a pulse oximeter, in addition to light of the at least first and second wavelengths, light of at least one third wavelength is used for irradiating and entering the skin for calculating the oxygen saturation in the blood, taking into account the melanin concentration in the skin. The at least one third additional wavelength is used to correct the melanin influence of the absorption spectra to estimate the oxygen saturation in the blood with high accuracy. In particular, the additional one third wavelength of the light is used by the evaluation circuit to estimate a melanin absorption coefficient and to apply a correction algorithm to estimate an improved and more accurate value for the oxygen saturation in the blood. Regarding the above equation for determining oxygen saturation SpO2, a correction 2022PF01801 May 17, 2024 P2022,2172 WO N - 6 - factor may be added that is dependent on the determined melanin concentration in the skin. According to a possible embodiment of the pulse oximeter, the light emitter device is configured to emit the light including the visible region and the near infrared region. The light emitter device may be configured, for example, for emitting the light having the at least one first wavelength in the visible region and to emit the light having the at least one second wavelength in the near infrared region. In particular, the light emitter device may be configured to emit the light having the at least one first wavelength in the visible region of between 600 and 750 nm. The light emitter device may be further configured to emit the light having the at least one second wavelength in the region of between 840 to 950 nm. The ratio of the light measurement in the region between 600 nm to 750 nm to the light measurement in the region between 840 nm and 950 nm is converted by the evaluation circuit to the oxygen saturation based on the Beer-Lambert law. The at least one third wavelength of the light to estimate the melanin concentration or the melanin absorption coefficient is selected in a range where the absorption spectra of oxygenated and deoxygenated haemoglobin almost overlap. The measured absorption spectra at the at least one third wavelength is thus largely independent from the oxygen saturation of the red blood cells. According to a possible embodiment of the pulse oximeter, the light emitter device is configured to emit the light having the at least one third wavelength in the region between 400 nm to 600 nm. 2022PF01801 May 17, 2024 P2022,2172 WO N - 7 - According to another possible embodiment of the pulse oximeter, the light emitter device may be configured to emit light having the at least one third wavelength in a region between 780 nm to 820 nm. Light having the at least one third wavelength in the region between 780 nm to 820 nm can also be used for determining the absorption coefficient of melanin or the concentration of melanin in the skin because oxygenated haemoglobin and deoxygenated haemoglobin show nearly the same absorption coefficient when the red blood cells are illuminated with light having a wavelength in the region between 780 nm to 820 nm, particularly at 800 nm. According to a possible embodiment of the pulse oximeter, first optical barriers may be arranged between the light emitter device for emitting light with at least three wavelengths, and the light receiver device for detecting the light, after the light has passed through the body or after the light has been reflected in the body. The first optical barriers should extend from a plane in which the light emitter device or the light receiver device are arranged until the surface of the skin so that the first optical barriers touch the skin. The first optical barriers thus prevent light emitted by the light emitter device from being reflected at the outer surface of the skin before the light enters the skin. According to a possible embodiment of the pulse oximeter, the light emitter device comprises at least one first light- emitting element for emitting light with the at least one first wavelength, for example light with a wavelength in the range of between 600 nm to 750 nm. The light emitter device may further comprise at least one second light-emitting element for emitting light with the at least one second 2022PF01801 May 17, 2024 P2022,2172 WO N - 8 - wavelength, for example light with a wavelength in the range of between 840 nm to 950 nm. The light emitter device may further comprise at least one third light-emitting element for emitting light with the at least one third wavelength, for example light with a wavelength in the range of between 400 nm to 600 nm, or light in the range of between 780 nm to 820 nm. The at least one first, second and third light- emitting element may be respectively configured as light- emitting diodes emitting light with different wavelengths in the above-specified visible to near infrared range. According to a possible embodiment, second optical barriers may be arranged between each of the light-emitting elements. The second optical barriers may extend from a plane in which the light-emitting elements are arranged until the surface of the skin so that the second optical barriers touch the skin. According to a possible embodiment of the pulse oximeter, the light receiver device comprises at least one first light- receiving element for receiving the light with the at least one first wavelength. The light receiver device may comprise at least one second light-receiving element for receiving the light with the at least one second wavelength. The light receiver device may comprise at least one third light- receiving element for receiving the light with the at least one third wavelength. The proposed setup thus comprises one light-receiving element per light-emitting element. According to the proposed approach, at the same time, each light- receiving element, for example a respective photodiode, detects a light signal emitted by a specified respective light-emitting element. 2022PF01801 May 17, 2024 P2022,2172 WO N - 9 - According to a possible embodiment of the pulse oximeter, third optical barriers may be arranged between each of the light-receiving elements. The third optical barriers may extend from a plane in which the light-receiving elements are arranged until the surface of the skin so that the second optical barriers touch the skin. According to a possible embodiment of the pulse oximeter, the at least one first, second and third light-emitting element are operated in a time-multiplexed operation state. The light receiver device may comprise a single light-receiving element. By operating the light-emitting elements in a time- multiplex mode, a sequential detection of the light signals emitted from different light-emitting elements can be performed by using only one single light-receiving element, for example a single photodiode, after the light passed through the body or is reflected within the body. According to another possible embodiment of the pulse oximeter, the light receiver device may comprise a multi- spectral light-receiving element. This configuration of the pulse oximeter allows light of different wavelengths to be emitted and detected at the same time. According to a possible embodiment of the pulse oximeter, the light emitter device may comprise at least one first light- emitting element for emitting white light, i.e. light in the range of between 400 nm to 780 nm. The light emitter device may further comprise at least one second light-emitting element for emitting light in the near infrared range, for example in the range between 840 nm to 950 nm. According to this embodiment, the light receiver device may comprise a 2022PF01801 May 17, 2024 P2022,2172 WO N - 10 - multi-spectral light-receiving element. This setup allows light to be emitted and detected at the same time. According to a possible embodiment of the pulse oximeter, the light emitter device and the light receiver device are arranged so that the light receiver device receives a portion of the emitted light being reflected in the body. In this case, the pulse oximeter determines the oxygen saturation in the blood by reflectance pulse oximetry. According to another possible embodiment of the pulse oximeter, the light emitter device and the light receiver device are arranged so that the light receiver device receives a portion of the emitted light after it is passed through the body without being reflected in the body. According to this approach, the pulse oximeter determines the oxygen saturation in the blood by transmissive pulse oximetry. Additional features and advantages of the proposed pulse oximeter 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 specification. As such, the disclosure will be more 2022PF01801 May 17, 2024 P2022,2172 WO N - 11 - fully understood from the following detailed description, taken in conjunction with the accompanying figures in which: Figure 1 illustrates the calculation of the ratio / absorption correlation between oxyhaemoglobin and deoxyhaemoglobin at different wavelengths in the visible and near infrared region; Figure 2 shows the course of the absorption coefficient of melanin, oxyhaemoglobin and deoxyhaemoglobin as a function of the wavelength of the light irradiated into a body; Figure 3 illustrates an operation of a pulse oximeter in a reflection mode for determining oxygen saturation; Figure 4 illustrates the operation of a pulse oximeter in a transmission mode for determining oxygen saturation; Figure 5 shows an embodiment of a pulse oximeter comprising a plurality of light-emitting elements and light- receiving elements for determining oxygen saturation by skin tone invariant pulse oximetry; Figure 6 shows an embodiment of a pulse oximeter comprising a plurality of light-emitting elements operated in a time-multiplex mode and a single light-emitting element for determining oxygen saturation by skin tone invariant pulse oximetry; Figure 7 shows an embodiment of a pulse oximeter comprising a light-emitting element for emitting white light and a light-emitting element for emitting light in the 2022PF01801 May 17, 2024 P2022,2172 WO N - 12 - near infrared range and a multi-spectral light- receiving element for determining oxygen saturation by skin tone invariant pulse oximetry; Figure 8 shows an embodiment of a pulse oximeter comprising a plurality of light-emitting elements and a multi- spectral light-receiving element for determining oxygen saturation by skin tone invariant pulse oximetry; and Figure 9 shows an embodiment of a pulse oximeter comprising optical barriers between a light emitter device and a light receiver device. Detailed Description of the Drawings Figure 2 retrieved and adapted from Mantri et al., Biomed. Opt. Express 13(11) 5683-5694 (2022) shows the absorption spectra of oxygenated haemoglobin / oxyhaemoglobin and deoxygenated haemoglobin / deoxyhaemoglobin and melanin for different wavelengths of light irradiated in the skin of a body to explain the measurement principle of the proposed pulse oximeter for determining oxygen saturation considering the melanin concentration of the skin. As shown in Figure 2, absorption of light at wavelengths in the visible region, for example the visible red region, between 600 nm and 750 nm, for example between 650 nm and 690 nm, and at wavelengths in the near infrared region between 840 nm and 950 nm, for example between 900 nm an 950 nm, differs significantly between blood loaded with oxygen and oxygen-depleted blood. When the body of a person is irradiated with light in the red or near infrared region, oxygenated haemoglobin absorbs more infrared light and allows more red light to pass through. 2022PF01801 May 17, 2024 P2022,2172 WO N - 13 - Deoxygenated haemoglobin allows more infrared light to pass through and absorbs more red light. The ratio of the red light measurement to the infrared light measurement may be calculated and converted to the oxygen saturation SpO2based on the formula: ^^^2 = ^ + ^^ with The absorption coefficient R is calculated by irradiating light in the body with two wavelengths ^1 and ^2 in the red visible region and the near infrared region. As illustrated in Figure 2, the body may be irradiated with light having a first wavelength ^1 of, for example, 660 nm, and a second wavelength ^2 of, for example, 940 nm. As explained above and illustrated in Figure 1, the absorption coefficient R is calculated by the ratio of a PPG (Photoplethysmography)-AC value divided by its baseline value (DC value) at the first wavelength ^1 and a PPG-AC value divided by its baseline value (DC value) at the second wavelength ^2. The PPG-AC value divided by its baseline value / DC value is related to absorption by the pulsatile arterial components (haemoglobin). The relationship between the absorption correlation R and the oxygen saturation SpO2is determined for each type of pulse oximeter by calibration. Referring to Figure 2, the absorption coefficient of melanin also varies depending on the wavelength of the light that is 2022PF01801 May 17, 2024 P2022,2172 WO N - 14 - irradiated into the skin of the body of a person. For the above example of a first wavelength ^1 = 660 nm of the irradiated light and a second wavelength ^2 = 940 nm of the irradiated light, the absorption coefficient of melanin is different. Consequently, the melanin concentration in the skin influences the optical path length of light irradiated into the body. The change in the optical path length between red and infrared light can change the relationship between the absorption coefficient factor R and the oxygen saturation SpO2. This is particularly fact with high melanin concentration in the skin. According to the proposed approach of a pulse oximeter for determining the oxygen saturation in the blood of a patient’s body being invariant of the skin-tone and thus the melanin concentration in the skin, light of at least a third wavelength ^3 is used to calculate the melanin influence and correct the oxygen saturation SpO2estimate with a melanin concentration coefficient. The additional at least one third wavelength ^3 of the light irradiated into the body will help to quantify the melanin concentration in the skin through a reflectivity measurement or transmissivity measurement and a semi-empirical model fit. Figures 3 and 4 show possible embodiments of a pulse oximeter 1 for determining the oxygen saturation SpO2considering the melanin concentration of the skin. The used measurement principle is based on the measurement of the absorption of light at different wavelengths ^1 and ^2 in the red visible range and the near infrared range by haemoglobin to determine the ratio / absorption correlation between oxyhaemoglobin and deoxyhaemoglobin, and the use of at least one third 2022PF01801 May 17, 2024 P2022,2172 WO N - 15 - wavelength ^3 to measure the impact of melanin on the ratio / absorption correlation between oxyhaemoglobin and deoxyhaemoglobin. Referring to Figures 3 and 4, the pulse oximeter 1 which allows the oxygen saturation in the blood of a body to be determined, taking into account the melanin concentration in the skin of the body, comprises a light emitter device 10, a light receiver device 20 and an evaluation circuit 30. The light emitter device 10, the light receiver device 20 and the evaluation circuit 30 may be disposed on a supporting board 70, for example a printed circuit board. The light emitter device 10 is configured to emit light 2 entering the skin 3 of a body 6. According to the proposed approach of the pulse oximeter 1, the light emitter device 10 is configured to emit the light 2 with at least three different wavelengths, including at least a first wavelength ^1, at least a second wavelength ^2 and at least a third wavelength ^3. The light receiver device 20 is configured to detect the light after it emerges from the skin 3. The evaluation circuit 30 is configured to evaluate the detected light 2 for determining the oxygen saturation of the blood 4 in vessels 7 or capillaries 8 of the body 6 in dependence on the detected light of the at least one first wavelength ^1 and the at least one second wavelength ^2, and in dependence on a determined concentration of melanin 5 in the skin 3. According to the proposed approach of the pulse oximeter 1, the evaluation circuit 30 is configured to determine the concentration of melanin 5 in the skin 3 in dependence on the detected light of the at least one third wavelength ^3. 2022PF01801 May 17, 2024 P2022,2172 WO N - 16 - The light emitter device 10 is configured to emit the light 2 in the visible region, for example the visible red region, and the near infrared region. In particular, the emitter device 10 may be configured to emit the light 2 having the at least one first wavelength ^1 in the visible range, for example the visible red range. For example, the light emitter device 10 may be configured to emit the light 2 with the at least one first wavelength ^1 in the visible region between 600 nm to 750 nm, for example at 660 nm, as shown in Figure 2. The light emitter device 10 may be further configured to emit the light with the at least one second wavelength ^2 in the near infrared region. In particular, the light emitter device 10 may be configured to emit the light 2 with the second wavelength ^2 between 840 nm and 950 nm, for example at ^2 = 940 nm, as shown in Figure 2. The light emitter device 10 is further configured to emit the light 2 with the at least one third wavelength ^3, where the absorption spectra of oxygenated haemoglobin and deoxygenated oxyhaemoglobin nearly overlap in the skin. In this region of wavelength, the absorption spectra is almost independent from the amount of oxygenated haemoglobin or deoxygenated haemoglobin in the blood so that the measurement of the absorption in this region of wavelengths allow the melanin absorption coefficient to be determined and thus the melanin concentration in the skin independently from the amount of oxygenated or deoxygenated haemoglobin of the red blood cells. Referring to Figure 2, the light emitter device 10 may be configured to emit the light 2 having the at least one third 2022PF01801 May 17, 2024 P2022,2172 WO N - 17 - wavelength ^3 in the region between 400 nm to 600 nm, or in a region between 780 nm to 820 nm. In these regions of wavelengths, oxygenated haemoglobin and deoxygenated haemoglobin have nearly the same absorption coefficient so that the measured absorption or absorption coefficient mainly depends on the melanin concentration in the skin. The pulse oximeter 1 may be embodied to be operated in a reflection mode, as illustrated in Figure 3, or in a transmission mode, as illustrated in Figure 4. Referring to Figure 3, the light emitted by the light emitter device 10 with at least three wavelengths ^1, ^2 and ^3 enters the epidermis 3a and dermis 3b of the skin 3 and is partially reflected. The light emitter device 10 and the light receiver device 20 are arranged so that the light receiver device 20 receives a portion of the emitted light being reflected in the body 6 towards the light receiver device 20. Referring to Figure 4, the light emitter device 10 and the light receiver device 20 are arranged so that the light receiver device 20 receives a portion of the emitted light after the light passed through the body 6 without being reflected in the body. Figures 5 to 9 show different setups for the light emitter device 10 and the light receiver device 20. Referring to the embodiment of the pulse oximeter 1 shown in Figure 5, the light emitter device 10 comprises a plurality of light-emitting elements, for example light-emitting diodes, 10a, …, 10n,. The light emitter device 10 may comprise at least one first light-emitting element 10a for emitting the light with the at least one first wavelength ^1, for example light with a wavelength ^1 between 600 nm and 750 2022PF01801 May 17, 2024 P2022,2172 WO N - 18 - nm. The light emitter device 10 further comprises at least one second light-emitting element 10b for emitting the light with the at least one second wavelength ^2, for example in the range between 840 nm to 950 nm. The light emitter device 10 further comprises at least one third light-emitting element 10c, …, 10n for emitting the light with the at least one third wavelength ^3, for example in the region between 400 to 600 nm, or in the region between 780 nm and 820 nm. Regarding the embodiment of the pulse oximeter 1 shown in Figure 5, the light receiver device 20 comprises a plurality of light-receiving elements, for example photodiodes, 20a, …, 20n. In particular, the light receiver device 20 comprises at least one first light-receiving element 20a for receiving the light with the at least one first wavelength ^1, at least one second light-receiving element 20b for receiving the light with the at least one second wavelength ^2, and at least one third light-receiving element 20c, …, 20n for receiving the light with the at least one third wavelength ^3. Regarding the embodiment of the pulse oximeter shown in Figure 5, a respective one of the light-receiving elements is provided for a respective one of the light-emitting elements. Thus, each light-receiving element 20a, …, 20n detects a light signal of a respective light-emitting element 10a, … 10n at the same time. Regarding the embodiment of the pulse oximeter shown in Figure 6, the light emitter device 10 comprises a plurality of light-emitting elements 10a, …, 10n. The light emitter device 10 may comprise at least one first light-emitting element 10a for emitting the light with the at least one 2022PF01801 May 17, 2024 P2022,2172 WO N - 19 - first wavelength ^1, for example light with a wavelength ^1 between 600 nm and 750 nm. The light emitter device 10 further comprises at least one second light-emitting element 10b for emitting the light with the at least one second wavelength ^2, for example a wavelength in the range between 840 nm to 950 nm. The light emitter device 10 further comprises at least one third light-emitting element 10c, …, 10n for emitting the light with the at least one third wavelength ^3, for example a wavelength in the region between 400 nm to 600 nm, or in the region between 780 nm and 820 nm. The light receiver device 20 comprises a single light- receiving element 21, for example a single photodiode. According to the proposed approach of Figure 6, the light- emitting elements 10a, …, 10n may be operated in a time- multiplexed operation mode. The embodiment of the pulse oximeter 1 thus uses a sequential detection of light signals by one light-receiving element 21, for example one photodiode, from different light-emitting elements 10a, …, 10n. According to the proposed embodiment of the pulse oximeter 1 shown in Figure 7, the light emitter device 10 comprises at least one first light-emitting element 10a for emitting white light and at least one second light-emitting element 10b for emitting light in the near infrared range. The light receiver device 20 comprises a multi-spectral light-receiving element 22 having sensor elements being respectively sensitive for the light emitted by the at least one first and second light- emitting element 10a and 10b. The pulse oximeter 1 of Figure 7 is operated by emitting light from the at least one first light-emitting element 10a and the at least one second light- 2022PF01801 May 17, 2024 P2022,2172 WO N - 20 - emitting element 10b, and by detecting the light with the multi-spectral light-receiving element 22 at the same time. Figure 8 shows a further embodiment of the pulse oximeter 1, wherein the light emitter device 10 comprises a plurality of light-emitting elements 10a, …, 10n. The light emitter device 10 may comprise at least one first light-emitting element 10a for emitting the light with the at least one first wavelength ^1, for example light with a wavelength ^1 between 600 nm and 750 nm. The light emitter device 10 further comprises at least one second light-emitting element 10b for emitting the light with the at least one second wavelength ^2, for example in the range between 840 nm to 950 nm. The light emitter device 10 further comprises at least one third light-emitting element 10c, …, 10n for emitting the light with the at least one third wavelength ^3, for example in the region between 400 to 600 nm, or in the region between 780 nm and 820 nm. The light receiver device 20 may comprise a multi-spectral light-receiving element 22. The multi-spectral light- receiving element 22 may comprise sensor elements, wherein each sensor element is respectively sensitive for light of one of the wavelengths ^1, ^2 and ^3 so that the proposed configuration allows light to be emitted and detected at the same time. In order to prevent light emitted from the light emitter device 10 and reflected at the surface of the skin without entering the skin or the body from being received at the light-receiving device 20, optical barriers 40 may be arranged between the light emitter device 10 and the light receiver device 20, as shown in Figure 9. The optical barriers 40 extend from the light emitter device 10 and the 2022PF01801 May 17, 2024 P2022,2172 WO N - 21 - light receiver device 20 until the surface of the skin 3 so that the optical barriers touch the skin. As illustrated in Figures 5 to 8, second optical barriers 50 may be arranged between each of the light-emitting elements 10, …, 10n. Moreover, as illustrated for the embodiment of Figure 5, third optical barriers 60 may be arranged between each of the light-receiving elements 20a, …, 20n. The embodiments of the proposed pulse oximeter disclosed herein have been discussed for the purpose of familiarizing the reader with novel aspects of the pulse oximeter. Although preferred embodiments have been shown and described, many changes, modifications, 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 pulse oximeter 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 modifications, 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 2022PF01801 May 17, 2024 P2022,2172 WO N - 22 - 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. 102023 115 507.5, the disclosure content of which is hereby incorporated by reference.

[0002] 2022PF01801 May 17, 2024 P2022,2172 WO N - 23 - References 1 pulse oximeter 2 light 3 skin 3a epidermis 3b dermis 4 blood 5 melanin 6 body 7 vessel capillary 10 light emitter device 10, …, 10n light-emitting element 20 light receiver device 20a, …, 20n light-receiving element 30 evaluation circuit 40, 50, 60 optical barrier 70 supporting board ^1, ^2, ^3 wavelength

Claims

2022PF01801 May 17, 2024 P2022,2172 WO N - 24 - Claims 1. A pulse oximeter for determining oxygen saturation considering melanin concentration of the skin, comprising: - a light emitter device (10), - a light receiver device (20), - wherein the light emitter device (10) is configured to emit light (2) for entering the skin (3), the light being emitted with at least three different wavelengths ( ^1, ^2, ^3) including at least a first wavelength ( ^1), at least a second wavelength ( ^2) and at least a third wavelength ( ^3), - wherein the light receiver device (10) is configured to detect the light after it emerges from the skin (3), - an evaluation circuit (30) to evaluate the detected light (2) for determining the oxygen saturation in the blood (4), - wherein the evaluation circuit (30) is configured to determine the oxygen saturation in the blood (4) in dependence on the detected light (2) of the at least one first wavelength ( ^1) and the at least one second wavelength ( ^2) and in dependence on a determined concentration of melanin (5) in the skin (3), - wherein the evaluation circuit (30) is configured to determine the concentration of melanin (5) in the skin (3) in dependence on the detected light (2) of the at least one third wavelength ( ^3).

2. The pulse oximeter of claim 1, wherein the light emitter device (10) is configured for emitting the light (2) in the visible region and the near infrared region.

3. The pulse oximeter of claim 1 or 2,2022PF01801 May 17, 2024 P2022,2172 WO N - 25 - wherein the light emitter device (10) is configured for emitting the light (2) having the at least one first wavelength ( ^1) in the visible region and the light (2) having the at least one second wavelength ( ^2) in the near infrared region.

4. The pulse oximeter of any of the claims 1-3, wherein the light emitter device (10) is configured for emitting the light (2) having the at least one third wavelength ( ^3) in a region between 400 nm to 600 nm.

5. The pulse oximeter of any of the claims 1-4, wherein the light emitter device (10) is configured for emitting the light (2) having the at least one third wavelength ( ^3) in a region between 780 nm to 820 nm.

6. The pulse oximeter of any of the claims 1-5, comprising: first optical barriers (40) being arranged between the light emitter device (10) and the light receiver device (20).

7. The pulse oximeter of any of the claims 1-6, - wherein the light emitter device (10) comprises at least one first light-emitting element (10a) for emitting the light (2) with the at least one first wavelength ( ^1), - wherein the light emitter device (10) comprises at least one second light-emitting element (10b) for emitting the light (2) with the at least one second wavelength ( ^2), - wherein the light emitter device (10) comprises at least one third light-emitting element (10c, …, 10n) for emitting the light (2) with the at least one third wavelength ( ^3).

8. The pulse oximeter of any of the claims 1-6,2022PF01801 May 17, 2024 P2022,2172 WO N - 26 - - wherein the light emitter device (10) comprises at least one first light-emitting element (10a) for emitting white light, - wherein the light emitter device (10) comprises at least one second light-emitting element (10b) for emitting light in the near infrared range.

9. The pulse oximeter of claim 7 or 8, comprising: second optical barriers (50) being arranged between each of the light-emitting elements (10a, …, 10n).

10. The pulse oximeter of claim 7 or 9, - wherein the light receiver device (20) comprises at least one first light-receiving element (20a) for receiving the light (2) with the at least one first wavelength ( ^1), - wherein the light receiver device (20) comprises at least one second light-receiving element (20b) for receiving the light (2) with the at least one second wavelength ( ^2), - wherein the light receiver device (20) comprises at least one third light-receiving element (20c, …, 20n) for receiving the light (2) with the at least one third wavelength ( ^3).

11. The pulse oximeter of claim 10, comprising: third optical barriers (60) being arranged between each of the light-receiving elements (20a, …, 20n).

12. The pulse oximeter of claim 7 or 9, wherein the at least one first, second and third light- emitting element (10a, …, 10n) are operated in a time- multiplexed operation mode, - wherein the light receiver device (20) comprises a single light-receiving element (21).2022PF01801 May 17, 2024 P2022,2172 WO N - 27 - 13. The pulse oximeter of any of the claims 7 to 9, wherein the light receiver device (20) comprises a multispectral light-receiving element (22).

14. The pulse oximeter of any of the claims 1-13, wherein the light emitter device (10) and the light receiver device (20) are arranged so that the light receiver device (20) receives a portion of the emitted light being reflected in a body (6).

15. The pulse oximeter of any of the claims 1-13, wherein the light emitter device (10) and the light receiver device (20) are arranged so that the light receiver device (20) receives a portion of the emitted light after being passed through a body (6) without being reflected in the body.

Images