An arrangement for determining physiological parameters indicative of cardiovascular status

Abstract

An arrangement (100a-b) for determining one or more physiological parameters indicative of the cardiovascular status of a user (200). The arrangement (100a-b) comprises: a detection arrangement (102) for detecting one or more first signals (202) associated with one or more blood flows of one or more blood vessels (204) of biological tissue (205) of the user (200); a blood flow index determination arrangement (104) for determining and generating blood flow index signals (206a, 206b, 206c) based on the one or more detected first signals (202); and a physiological parameter determination arrangement (106) for determining one or more physiological parameters indicative of the cardiovascular status of the user (200) based on the blood flow index signals (206a, 206b, 206c). By way of the step of determining one or more physiological parameters indicative of the cardiovascular status of the user (200) based on the blood flow index signals (206a, 206b, 206c), an improved determination or monitoring of physiological parameters indicative of the cardiovascular status of a user (200) is provided.

Description

[0001] AN ARRANGEMENT FOR DETERMINING PHYSIOLOGICAL PARAMETERS INDICATIVE OF

[0002] CARDIOVASCULAR STATUS

[0003] TECHNICAL FIELD

[0004] The invention relates to an arrangement for determining one or more physiological parameters indicative of the cardiovascular status of a user. Further, the invention relates to a method for determining one or more physiological parameters indicative of the cardiovascular status of a user.

[0005] BACKGROUND

[0006] In general, cardiovascular diseases (CVDs) are the world’s top cause of death. The cardiovascular complications, including coronary heart disease and cerebrovascular disease, have driven the need for onset and early-stage detection, continuous monitoring of vital signals, and precise multi-parameter diagnosis. Accurate assessment of cardiovascular changes and risk factors is crucial to the reduction of cardiovascular disease morbidity and mortality. Early detection using physiological parameters, or biomarkers, is key.

[0007] SUMMARY

[0008] The inventors have found drawbacks in conventional solutions for determining and / or monitoring physiological parameters, or biomarkers, indicative of the cardiovascular status of a user so as to evaluate the cardiovascular status of the user. For example, some conventional solutions are insufficient or not efficient enough and can be further improved.

[0009] An object of embodiments of the invention is to provide a solution which mitigates or solves drawbacks and problems of conventional solutions.

[0010] The above-mentioned and further objects are solved by the subject matter of the independent claims. Further advantageous embodiments of the invention can be found in the dependent claims.

[0011] According to a first aspect of the invention, the above-mentioned and other objects are achieved with an arrangement for determining one or more physiological parameters indicative of the cardiovascular status of a user, wherein the arrangement comprises a detection arrangement for detecting one or more first signals associated with one or more blood flows of one or more blood vessels of biological tissue of the user, wherein the arrangement comprises a blood flow index determination arrangement for determining and generating two or more blood flow index signals based on the one or more detected first signals, and wherein the arrangement comprises a physiological parameter determination arrangement for determining one or more physiological parameters indicative of the cardiovascular status of the user based on the two or more determined and generated blood flow index signals.

[0012] By way of the step of determining one or more physiological parameters indicative of the cardiovascular status of the user based on two or more determined and generated blood flow index (BFi) signals, an advantage of the arrangement according to the first aspect is an improved determination, collection, and / or monitoring, of physiological parameters, or biomarkers, indicative of the cardiovascular status of a user. Based on the improved determination of the physiological parameters, an advantage of the arrangement according to the first aspect is a facilitated or improved evaluation of the cardiovascular status of a user. Based on the improved determination of the physiological parameters and / or the improved evaluation of the cardiovascular status of a user, an advantage of the arrangement according to the first aspect is a facilitated or improved detection of cardiovascular diseases. An advantage of the arrangement according to the first aspect is that the determined physiological parameters can be used to efficiently evaluate the effect of local interventions and treatments, as well as to efficiently assess local vascular function and pathology. An advantage of the arrangement according to the first aspect is a reduced electric power consumption of the arrangement in relation to conventional solutions. An advantage of the arrangement according to the first aspect is that the arrangement, or at least the detection arrangement, can be provided as a wearable and / or portable device, which is non-expensive, compact in size and lightweight, which makes embodiments of the arrangement suitable for long-term

[0013] In an implementation form of an arrangement according to the first aspect, based on the two or more determined and generated blood flow index signals, the physiological parameter determination arrangement is configured to determine one or more of the group of:

[0014] • a pulse transit time (PTT); and

[0015] • a pulse wave velocity (PWV).

[0016] An advantage with this implementation form is a further improved determination and / or monitoring of physiological parameters indicative of the cardiovascular status of a user. By usage of the determined and generated blood flow index signals, an improved and more efficient manner to determine pulse transit time (PTT) or pulse wave velocity (PWV) in relation to conventional solutions is provided. Pulse transit time (PTT) and pulse wave velocity (PWV) are advantageous physiological parameters, or biomarkers, for the evaluation of the cardiovascular status of a user, which is disclosed in further detail in the detailed description hereinbelow.

[0017] In an implementation form of an arrangement according to the first aspect, the detection arrangement is configured to detect one or more first signals originating from two or more different depths of biological tissue of the user. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user.

[0018] In an implementation form of an arrangement according to the first aspect, the arrangement comprises a wearable and / or portable device configured to be carried by the user, wherein the wearable and / or portable device comprises at least the detection arrangement. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user. For some embodiments, the wearable and / or portable device may further comprise the blood flow index determination arrangement. For some embodiments, the wearable and / or portable device may further comprise the physiological parameter determination arrangement.

[0019] In an implementation form of an arrangement according to the first aspect, the arrangement is in the form of a wearable and / or portable device configured to be carried by the user. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user.

[0020] In an implementation form of an arrangement according to the first aspect, the blood flow index determination arrangement is configured to determine and generate two or more blood flow index signals based on one or more first signals detected by a single sensor of the detection arrangement. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user. An advantage with this implementation form is that the need for time synchronization used in conventional multi-sensory solutions is eliminated.

[0021] In an implementation form of an arrangement according to the first aspect, the sensor of the detection arrangement comprises one or more photodetectors. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user. In an implementation form of an arrangement according to the first aspect, the detection arrangement comprises one or more of the group of:

[0022] • a laser speckle-based sensor comprising one or more photodetectors; and

[0023] • a Doppler shift-based sensor comprising one or more photodetectors.

[0024] An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user.

[0025] In an implementation form of an arrangement according to the first aspect, the blood flow index determination arrangement is configured to determine and generate two or more blood flow index signals based on one or more first signals comprising one or more of the group of:

[0026] • a laser speckle signal; and

[0027] • a Doppler signal.

[0028] An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user.

[0029] In an implementation form of an arrangement according to the first aspect, the blood flow index determination arrangement is configured to determine and generate two or more blood flow index signals at two or more frequency windows different from one another. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user.

[0030] In an implementation form of an arrangement according to the first aspect, the blood flow index determination arrangement is configured to perform a depth- and velocity-resolved frequency window selection in different layers of biological tissue of the user, wherein the blood flow index determination arrangement is configured to determine and generate blood flow index signals corresponding to different depths and velocities of the different layers of biological tissue of the user based on the selected frequency windows so as to improve the quality of the two or more determined and generated blood flow index signals. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user.

[0031] In an implementation form of an arrangement according to the first aspect, the blood flow index determination arrangement is configured to determine and generate two or more blood flow index signals based on the one or more detected first signals by usage of Doppler power spectrum analysis. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user.

[0032] In an implementation form of an arrangement according to the first aspect, the blood flow index determination arrangement is configured to determine and generate two or more blood flow index signals based on the one or more detected first signals by usage of autocorrelation analysis. An advantage with this implementation form is a further improved determination, collection and / or monitoring of physiological parameters indicative of the cardiovascular status of a user.

[0033] According to a second aspect of the invention, the above-mentioned and other objects are achieved with a method for determining one or more physiological parameters indicative of the cardiovascular status of a user, wherein the method comprises: based on one or more detected first signals associated with one or more blood flows of one or more blood vessels of biological tissue of the user, determining and generating two or more blood flow index signals; and based on the two or more determined blood flow index signals, determining one or more physiological parameters indicative of the cardiovascular status of the user.

[0034] Advantages of the method according to the second aspect correspond to advantages of the arrangement according to the first aspect and its embodiments mentioned above or below.

[0035] In an implementation form of the method according to the second aspect, the method further comprises: detecting one or more first signals associated with one or more blood flows of one or more blood vessels of biological tissue of the user by usage of a detection arrangement.

[0036] According to a third aspect of the invention, the above-mentioned and other objects are achieved with a computer program or a computer-readable medium comprising instructions which, when the program or the instructions is / are executed by a computer, cause the computer to carry out the method according to any one of the embodiments disclosed above or below.

[0037] Advantages of the computer program or the computer-readable medium according to the third aspect correspond to advantages of the arrangement according to the first aspect and its embodiments mentioned above or below. According to an aspect of the present disclosure, the above-mentioned computer program or the computer-readable medium is configured to implement the method and its embodiments described herein.

[0038] Further applications and advantages of the implementation forms or embodiments of the invention will be apparent from the following detailed description.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The appended drawings are intended to clarify and explain different embodiments of the invention, in which:

[0041] Figure 1 is a schematic diagram of an embodiment of the arrangement according to the first aspect of the invention, applied to a user;

[0042] Figure 2 is another schematic diagram of the user of figure 1 ;

[0043] Figure 3 shows two diagrams, (a) and (b), schematically illustrating a first signal associated with one or more blood flows of one or more blood vessels of biological tissue of a user;

[0044] Figure 4 shows three diagrams, (a), (b) and (c), each schematically illustrating three different blood flow index signals for three different frequency ranges but determined from three different locations, namely (a): the dorsal wrist of a left hand of a user; (b): the ring finger of a right hand of the user; and (c): the index finger tip of a right hand of the user, wherein the determined blood flow index signals are normalized for fair comparison;

[0045] Figure 5 shows four diagrams, (a), (b), (c) and (d), for schematically illustrating the determination of a physiological parameter in the form of a pulse transit time (PTT), wherein each one of the diagrams (a)-(c) schematically illustrates two blood flow index signals for two different frequency ranges from diagram (a) of figure 4 over a selected shorter time period, while diagram (d) schematically illustrates a first derivative of the normalized blood flow index signals;

[0046] Figure 6 is a schematic diagram of an embodiment of a detection arrangement or of a sensor of the detection arrangement of an embodiment of the arrangement according to the first aspect of the invention, applied to a user;

[0047] Figure 7A is a schematic diagram of another embodiment of a detection arrangement or of a sensor of the detection arrangement of an embodiment of the arrangement according to the first aspect of the invention, applied to a user; Figure 7B is a schematic diagram of yet another embodiment of a detection arrangement or of a sensor of the detection arrangement of an embodiment of the arrangement according to the first aspect of the invention, applied to a user;

[0048] Figure 8 shows two diagrams, (a) and (b), for schematically illustrating the determination of blood flow index signals at different frequency windows, wherein diagram (b) shows magnified segments limited by solid borders from diagram (a) of two blood flow index signals at two different frequency ranges for better comparison;

[0049] Figure 9 is a schematic flow chart illustrating aspects of embodiments of the method according to the second aspect of the invention;

[0050] Figure 10 is another schematic flow chart illustrating aspects of embodiments of the method according to the second aspect of the invention;

[0051] Figure 11 is a schematic diagram of another embodiment of the arrangement according to the first aspect of the invention applied to a user;

[0052] Figure 12 is a schematic flow chart illustrating aspects of embodiments of the arrangement according to the first aspect of the invention and of the method according to the second aspect of the invention;

[0053] Figure 13 is another schematic flow chart illustrating further aspects of embodiments of the arrangement according to the first aspect of the invention and of the method according to the second aspect of the invention; and

[0054] Figure 14 is yet another schematic flow chart illustrating further aspects of embodiments of the arrangement according to the first aspect of the invention and of the method according to the second aspect of the invention.

[0055] DETAILED DESCRIPTION

[0056] With reference to figures 1 to 8, aspects of embodiments of the arrangement 100a for determining one or more physiological parameters indicative of the cardiovascular status of a user 200, or a patient, according to the first aspect of the invention are schematically illustrated. For some embodiments, the physiological parameter may be referred to as a biological parameter. For some embodiments, the physiological parameter may be referred to as a physiological quantity, a physiological indicator, or a biomarker. For some embodiments, the one or more physiological parameters may comprise one or more of the group of: a pulse transit time (PTT); and a pulse wave velocity (PWV). For some embodiments, the cardiovascular status may be referred to as cardiovascular condition, or cardiovascular health.

[0057] With reference to figure 1, the arrangement 100a comprises a detection arrangement 102 for detecting one or more first signals 202 (see figure 3) associated with one or more blood flows of one or more blood vessels 204 (see figure 2) of biological tissue 205 of the user 200. For some embodiments, the biological tissue 205 may be referred to as a human body tissue. The arrangement 100a comprises a blood flow index (BFi) determination arrangement 104 for determining and generating (or producing) two or more blood flow index (BFi) signals 206a, 206b, 206c (see figures 4, 5 and 8), such as blood flow index (BFi) waveforms, based on the one or more detected first signals 202 (see figure 3), such as three or more blood flow index signals 206a, 206b, 206c based on the one or more detected first signals 202. The arrangement 100a comprises a physiological parameter determination arrangement 106 for determining one or more physiological parameters (see figure 5) indicative of the cardiovascular status of the user 200 based on the two or more determined and generated blood flow index signals 206a, 206b, 206c.

[0058] For some embodiments, the detection arrangement 102, the blood flow index (BFi) determination arrangement 104 and the physiological parameter determination arrangement 106 may be located in the same physical entity or unit, or may be located in two or more different and physically separated physical entities or units. For some embodiments, the arrangement 100a may be in the form of, or referred to as, a system, or an apparatus. Blood flow index (BFi) may be described as a relative measure of microvascular blood flow, typically defined as the product of the concentration of moving red blood cells (RBCs) and their mean velocity. In diffuse correlation spectroscopy, blood flow index (BFi) may also be derived from the decay rate of the autocorrelation function of scattered light intensity fluctuations, related to dynamic behavior of RBCs.

[0059] Blood flow index (BFi) may be described, or defined, as a relative measure of tissue blood flow over time, calculated from Doppler measurements (for example, using first moment of Doppler power spectrum, or using autocorrelation technique), reflecting the average flow of moving red blood cells.

[0060] With reference to figures 1 and 5, for some embodiments, based on the two or more determined and generated blood flow index signals 206a, 206b, 206c, the physiological parameter determination arrangement 106 may be configured to determine one or more of the group of: a pulse transit time (PTT); and a pulse wave velocity (PWV). Pulse transit time (PTT) may be defined or described as the time difference of the blood pulsation at different sites, or locations. Pulse wave velocity (PWV) may be defined or described as the speed of forward pressure between two different sites, or locations. Pulse transit time (PTT) and a pulse wave velocity (PWV) are inversely related to each other, i.e., PWV oc pTT-someapplications and methodologies, the exact relationship or exact values may not be crucial. However, given the length of the underlying blood vessel segment, pulse wave velocity (PWV) can be determined, or computed, as the ratio of said length to the pulse transit time (PTT), i.e., PWV = / pTf, where L may be the distance between measurement locations.

[0061] Cardiovascular diseases (CVDs) may be seen as the world’s top cause of death. The cardiovascular complications, including coronary heart disease and cerebrovascular disease, have driven the need for onset and early-stage detection, continuous monitoring of vital signals, and precise multi-parameter diagnosis. Accurate assessment of cardiovascular changes and risk factors is crucial to the reduction of morbidity and mortality from cardiovascular diseases. Early detection using multiple parameters may be considered key. The inventors of the present invention have found that conventional evaluations based on conventional vital signals, such as heart rate, heart rate variability, are insufficient. Better diagnosis can be achieved by managing classic risk factors, such as age, gender, smoking, hypertension, and body mass index, conducting biological analyses, and using physiological parameters, or biomarkers, such as pulse wave velocity (PWV), which is considered as a measure of arterial stiffness.

[0062] The stiffening (i.e., process of hardening) of the arteries has been shown to start from around the first or second decades of life in healthy subjects, and it can be accelerated by medical conditions including renal disease and diabetes mellitus. Objective assessment of arterial elastic properties and vascular ageing are important, since arterial stiffness is associated with hypertension, which is a risk factor for stroke and coronary heart disease. As the arteries become stiffer due to natural aging and cardiovascular conditioning, the vessels lose their distensibility and compliance, causing the blood pressure pulse wave to travel faster through the vessels. This results in faster pulse wave velocity (PWV) and thus shorter pulse transit time (PTT), i.e., the pulse time delay between two arterial places, or locations. Another application of the determination or measurement of pulse transit time (PTT), or pulse wave velocity (PWV), is the indirect estimation of blood pressure (BP). It has been demonstrated that pulse transit time (PTT) has a direct relationship with blood pressure (BP), while pulse wave velocity (PWV) has an indirect relationship with blood pressure (BP).

[0063] The inventors of the present invention have identified that blood flow velocity decreases as the blood flow, or blood, travels from large deep arteries through arterioles to capillaries. The inventors of the present invention have found that laser specklebased techniques provide a mean to gauge blood flow within cutaneous vasculature by estimating a parameter called blood flow index (BFi). The blood flow index (BFi) can be derived from the Doppler shifts and intensity of the detected light, which enables a quantification of blood flow information through frequency-based analysis. The hemodynamics of vasculature suggest that higher frequency blood flow index (BFi) waveforms correspond to swifter blood flow velocities in deeper tissues and vessels, where more Doppler shifts occur. Conversely, lower frequency blood flow index (BFi) waveforms correspond to slower blood flow velocities in superficial areas, resulting in fewer Doppler shifts. Leveraging this property, the inventors of the present invention have found that it is possible to calculate the discrepancy in the arrival times of blood flow pulsations across different layers of skin (transcutaneous vasculature), serving as a measure of local pulse transit time (PTT).

[0064] With reference to figures 1 and 7A, for some embodiments, the detection arrangement 102 may be configured to detect one or more first signals 202 originating from two or more different depths 207a, 207b of biological tissue 205 of the user 200, such as two or more different depths 207a, 207b of biological tissue 205 from the skin 214, or from the outer surface of the skin 214, of the user 200.

[0065] With reference to figures 1, 7B and 11, for some embodiments, the arrangement 100a; 100b may comprise a wearable and / or portable device 108a; 108b; 108c configured to be carried by the user 200, wherein the wearable and / or portable device 108a; 108b; 108c comprises at least the detection arrangement 102. For some embodiments, the wearable and / or portable device 108a; 108b; 108c may further comprise the blood flow index determination arrangement 104. For some embodiments, the wearable and / or portable device 108a; 108b; 108c may further comprise the physiological parameter determination arrangement 106. For some embodiments, the arrangement 100a; 100b may be in the form of a wearable and / or portable device 108a; 108b, 108c configured to be carried by the user 200. For example, as a watch around the wrist, a device around the upper arm, a ring around a finger, a neckless around the neck, or an earring in the ear of the user. However, other types of devises and locations of the devise are possible.

[0066] With reference to figures 1, 6 and 7A, for some embodiments, the blood flow index determination arrangement 104 may be configured to determine and generate two or more blood flow index signals 206a, 206b, 206c based on one or more first signals 202 detected by (or from) a single sensor 110a; 100b of the detection arrangement 102. For some embodiments, the sensor 110a, 110b of the detection arrangement 102 may include one or more photodetectors 112a; 112b, for example two or more photodetectors 112a; 112b.

[0067] With reference to figures 1, 6 and 7A, for some embodiments, the detection arrangement 102 may include one or more of the group of: a laser speckle-based sensor 114 comprising one or more photodetectors 112a, 112b; and a Doppler shift-based sensor 116 comprising one or more photodetectors 112a, 112b. For some embodiments, the blood flow index determination arrangement 104 may be configured to determine and generate two or more blood flow index signals 206a, 206b, 206c based on one or more first signals 202 comprising one or more of the group of: a laser speckle signal; and a Doppler signal. With reference to figures 6 and 7A, for some embodiments, the sensor 110a, 110b of the detection arrangement 102 may include a laser light-emitting source, or a laser light emitter 118a, 118b. Thus, for some embodiments, the first signal 202 may be referred to as a Doppler signal or a laser speckle signal.

[0068] Figure 8 shows two diagrams, (a) and (b), for schematically illustrating the determination of blood flow index signals 206a, 206b at different frequency windows 210a, 210b. Diagram (a) shows five blood flow index signals at five different frequency ranges, whereas diagram (b) shows magnified segments limited by solid borders in diagram (a) of only two blood flow index signals 206a, 206b of the five blood flow index signals of diagram (a) at two different frequency ranges for better comparison. A first frequency window 210a of the two different frequency windows 210a, 210b ranges from 30 kHz to 40 kHz. A second frequency window 210b of the two different frequency windows 210a, 210b ranges from 0.5 kHz to 10 kHz. With reference to figures 1 and 8, for some embodiments, the blood flow index determination arrangement 104 may be configured to determine and generate two or more blood flow index signals 206a, 206b at (or in) two or more frequency windows 210a, 210b, or ranges, different from one another.

[0069] With reference to figures 1, 7A and 8, for some embodiments, the blood flow index determination arrangement 104 may be configured to perform a depth- and velocity-resolved frequency window selection (or perform a selection of depth- and velocity-resolved frequency windows) in different layers 212a, 212b of biological tissue 205 of the user 200. The blood flow index determination arrangement 104 may be configured to determine and generate blood flow index signals 206a, 206b corresponding to different depths 207a, 207b and velocities of the different layers 212a, 212b of biological tissue 205 of the user 200 based on the selected frequency windows 210a, 210b so as to improve the quality of the two or more determined and generated blood flow index signals 206a, 206b. For some embodiments, it may be described that the selected frequency windows 210a, 210b are adaptively selected to extract blood flow information, or data, based on the velocity of the red blood cells (RBCs) flowing within a specific layer 212a, 212b or vasculature. For some embodiments, the time delay (phase incoherence) between the determined blood flow index signals 206a, 206b, or blood flow index waveforms, of different different layers 212a, 212b of biological tissue 205 may be determined, or computed.

[0070] Figure 3 shows two diagrams, (a) and (b), schematically illustrating a first signal 202 associated with one or more blood flows of one or more blood vessels 204 of biological tissue 205 of a user 200. Diagram (a) of figure 3 shows the in vivo example of a differential Doppler (AC) signal acquired with a sampling frequency of fs= 100 kHz and by usage of a sensor 110a including two photodetectors 112a, 112b equally spaced from a laser light emitter 118a , such as the sensor 110a of the of the detection arrangement 102 schematically illustrated in figure 6 and disclosed in further detail hereinbelow. In diagram (a) of figure 3, and for some embodiments, the first signal 202 may comprise, or may be in the form of, a reference blood flow velocity measured by the sensor 110a of figure 6, or by any other kind of blood flow meter. For other embodiments, the first signal 202 may be another signal associated with one or more blood flows of one or more blood vessels 204 of biological tissue 205. Diagram (b) of figure 3 shows a magnified 0.1 second segment, highlighted within a rectangle with a solid border in diagram (a) of figure 3. The Blood flow index (BFi) waveforms presented in diagram (a) of figure 8 are derived from the Doppler signal shown in diagram (a) of figure 3.

[0071] Figure 6 schematically illustrates an embodiment of the detection arrangement 102 and / or an embodiment of the sensor 110a of the of the detection arrangement 102. View (a) is a top view of the sensor 110a applied to the skin 214 of a user 200, and view (b) is a diagram illustrating in more detail the circuit and components, or modules, of the sensor 110a. For some embodiments, the laser speckle-based sensor 114 may have two photodetectors 112a, 112b substantially equally spaced from the laser light emitter 118a, which is positioned between the two photodetectors 112a, 112b, for the measurement of blood flow in biological tissue 205. For other embodiments, the two photodetectors 112a, 112b may be spaced from the laser light emitter 118a by different distances d, i.e., the distances d may differ from one another. For some embodiments, the sensor 110a may comprise an analog-to-digital converter (ADC) 120. The sensor 110a may comprise an amplifier 122, wherein the two photodetectors 112a, 112 may be connected to the analog-to-digital converter 120 via the amplifier 122. The sensor 110a may comprise a microcontroller unit (MCU) 124, wherein the two photodetectors 112a, 112 may be connected to the microcontroller unit 124 via the analog-to-digital converter 120. The sensor 110a may comprise a power source 126 providing electric power to the different modules or components of the sensor 110a. The sensor 110a may comprise a laser driver 128 operating the laser light emitter 118a. However, it is to be understood that the sensor 110a may be designed in another manner and may include additional components or units. For some embodiments, the analog-to-digital converter 120 and the microcontroller unit 124 may be replaced by an analog signal processor unit (ASPU). For some embodiments, the analog signal processor unit (ASPU) may directly determine or compute power spectrums of blood flow index signals or waveforms evaluated at different frequency bands directly from analog Doppler signals. For some embodiments, the sensor 110a may comprise three or more photodetectors, for example three photodetectors in a triadic pattern where the photodetectors may have the same distance to the laser light emitter. For some embodiment with three or more photodetectors, the photodetectors may have different distances to the laser light emitter. For some embodiments, it may be defined that the sensor 110a is configured to be applied to the skin 214 of the user 200.

[0072] Figure 7A schematically illustrates another embodiment of the detection arrangement 102 and / or another embodiment of the sensor 110b of the of the detection arrangement 102. View (a) is a side view of the sensor 110b when applied to the skin 214 of the user 200, and view (b) is a top view of the sensor 110b applied to the skin 214 of the user 200. The embodiment of the sensor 110b of figure 7A differs from the embodiment of the sensor 110a of figure 6, inter alia, in that the laser light emitter 118b is not located between the two photodetectors 112a, 112b but one 112b of the photodetectors 112a, 112b is located between the laser light emitter 118b and the other one 112a of the photodetectors 112a, 112b. In figure 7A, the distances di, d: between the laser light emitter 118b and the respective photodetector 112a, 112b are different form one another. The distances di, d2 may vary and may be adapted to different applications.

[0073] The embodiments of figures 6 and 7A may be described to be illustrated for reflectance geometry, or mode. However, the data collection may be done in transmittance geometry, or mode, as well, as in the embodiment schematically illustrated in figure 7B and discussed in further detail hereinbelow. The light transmission paths originating from the laser light emitter 118b-c are schematically illustrated in figures 7A and 7B as dotted fields 113a, 113b, 113c. In figure 7A, the photodetector 112a with the longer distance to the laser light emitter 118b reaches to a deeper part of the biological tissue 205, as illustrated by the dotted field 113a.

[0074] Figure 7B schematically illustrates yet another embodiment of the detection arrangement 102 and / or another embodiment of the sensor 110c of the of the detection arrangement 102. The embodiment of the sensor 110c of figure 7B differs from the embodiment of the sensor 110a of figure 6, inter alia, in that the laser light emitter 118c and one or more photodetectors 112a are configured to be positioned on opposing sides of a body part of a user 200, such on opposing sides of a finger 216 of the user 200. The laser light emitter 118c and photodetector 112a may be incorporated in a wearable and / or portable device 108c in the form a ring 109. The sensor 110c may be a laser speckle sensor working in a transmittance mode, with one photodetector 112a and one laser light emitter 118c. Blood flow index (BFi) waveforms associated with different blood flow velocities can be determined using the Doppler power spectrum analysis or the light intensity autocorrelation analysis. This transmission mode can be applied to the finger 216 using a ring 109, or to the earlobe of the user 200 by usage of an earring. One or more laser light emitters 118c can be used, which also applies to the embodiments of figures 6 and 7A. It is to be understood that other sensors of the detection arrangement 102 are possible.

[0075] Figure 4 shows three diagrams, (a), (b) and (c), each schematically illustrating three different blood flow index signals 206a, 206b, 206c for three different frequency ranges, or windows, namely 6 to 12 kHz, 16 to 30 and 30 to 50 kHz (or 40 to 80 kHz), respectively, but determined from three different locations, namely (a): the dorsal wrist of a left hand of a user; (b): the ring finger of a right hand of the user; and (c): the index finger tip of a right hand of the user. The determined blood flow index signals 206a, 206b, 206c, or waveforms, are normalized for better comparison. More specifically, figure 4 illustrates three examples of in vivo (normalized) blood flow index (BFi) signals 206a, 206b, 206c, or waveforms, computed from the above- mentioned three locations (a), (b) and (c), respectively. The raw Doppler signals were acquired by a laser speckle-based sensor, such as the sensor 110a illustrated in figure 6. Factors influencing penetration depth and the selected frequency windows enable depth- and velocity-resolved detection of blood pulsation across different tissue layers. For example, in diagram (a), the blood flow index (BFi) signals 206a, 206b, 206c, or waveforms, computed at frequency windows [6.0-12.0] kHz, [16.0-30.0] kHz, and [30.0-50.0] kHz may correspond to blood pulsations in the deeper part of the subepidermal plexus, dermal plexus, and shallower part of the subdermal plexus, respectively. Said frequency ranges are approximate. Thus, implementations with different frequency windows are also possible. As shown by the peaks of the waveforms of the different diagrams (a), (b) and (c) of figure 4, there is a clear delay between the peaks of diagrams (a), (b) and (c), indicating that blood pulsation arrives first in the deeper tissue layers and then travels to the superficial layers.

[0076] Figure 5 shows four diagrams, (a), (b), (c) and (d), for schematically illustrating the determination of a physiological parameter in the form of pulse transit time (PTT), wherein each one of the diagrams (a)-(c) schematically illustrates two blood flow index (BFi) signals 206a, 206b, or waveforms, for two different frequency ranges, namely the windows of 6 to 12 kHz and 30 to 50 kHz, respectively, from diagram (a) of figure 4 over a selected shorter time period, or segment. Diagram (d) of figure 5 schematically illustrates a first derivative of the normalized blood flow index (BFi) signals 206a, 206b, or waveforms. Figure 5 may also be considered as an illustration of some fiducial points for computing the transcutaneous pulse transit time (PTT), using a segment of the waveforms shown in diagram (a) of figure 4 as an example. The time delay between the two waveforms is denoted by At;.

[0077] Pulse transit time (PTT), or transcutaneous pulse transit time (PTT), can be determined or computed in different ways from blood flow index (BFi) signals 206a, 206b, such as from fiducial points within blood flow index (BFi) waveforms of different frequencies. Some examples of these fiducial points include:

[0078] • the peaks in the forward pulses (see diagram (a) of figure 5);

[0079] • the mid-point of rising slopes in the forward pulses (see diagram (b) of figure 5:

[0080] • the intersection of average slope and peak (see diagram (c) of figure 5: and

[0081] • the maximum of gradients in the forward pulses (see diagram (d) of figure 5.

[0082] Further, transcutaneous pulse transit time (PTT) may be determined or calculated as the time delay between the rising edges of the (depth- and velocity-resolved) blood flow index (BFi) waveforms derived from different frequency windows. These are just a few examples, and the determination or computation is not limited to these points.

[0083] For some embodiments, the proposed local pulse transit time (PTT) may be determined or calculated as the average of time delays derived from depth- and velocity-resolved blood flow index (BFi) or speckle flow index (SFi) signals, or waveforms, which represent blood flow pulsation at various skin layers. For some embodiments, the blood flow index (BFi) signal may be determined using the first moment of the Doppler power spectrum. Alternatively, depth- and velocity-resolved time delays can be computed from other moments of the Doppler power spectrum, such as the zero411or second moments. For some embodiments, laser speckle-based waveforms for calculating local pulse transit time (PTT) (or local pulse wave velocity, PWV) may be determined or computed at different frequency windows (or at distinct exposure-time intervals in dynamic light scattering or laser speckle contrast imaging) corresponding to different depths of biological tissue and velocities. For some embodiments, instead of averaging, one may use the median or other statistical operations to determined or compute the local pulse transit time (PTT) from the obtained depth- and velocity-resolved time delays. As already mentioned above, pulse transit time (PTT) and a pulse wave velocity (PWV) are inversely related to one another. Given the length of the underlying blood vessel segment, pulse wave velocity (PWV) may be determined, or computed, as the ratio of said length to the pulse transit time (PTT).

[0084] With reference to figure 1, for some embodiments, the arrangement 100b may be configured to communicate with an external or remote computer 130 or computer system, which in turn may be include, or be connected, to a data base. The arrangement 100b may be configured to directly or indirectly communicate with the computer 130, for example wirelessly. For some embodiments, the arrangement 100b may comprise devices for receiving and transmitting input and output signals. These input and output signals may contain waveforms, impulses, or other attributes which, by means of the devices for the reception of input signals, can be detected as information and can be converted into signals which can be processed. The devices for the transmission of output signals may be arranged to convert signals in order to create output signals by, for example, modulating the signals, which, for example, can be transmitted to the external or remote computer 130 or computer system. The detection arrangement 102, the blood flow index determination arrangement 104 and the physiological parameter determination arrangement 106 may be configured to directly or indirectly communicate with one another, for example wirelessly, or via wire, or in other ways.

[0085] With reference to figures 9 and 10, embodiments of the method 400 for determining one or more physiological parameters indicative of the cardiovascular status of a user 200 according to the second aspect of the invention are schematically illustrated in flow charts.

[0086] With reference to figure 9, embodiments of the method 400 for determining one or more physiological parameters indicative of the cardiovascular status of a user 200 according to the second aspect include the steps of:

[0087] • based on one or more detected first signals 202 associated with one or more blood flows of one or more blood vessels 204 of biological tissue 205 of the user 200, determining and generating 402 two or more blood flow index signals 206a, 206b, 206c; and

[0088] • based on the two or more determined blood flow index signals 206a, 206b, 206c, determining 403 one or more physiological parameters indicative of the cardiovascular status of the user 200.

[0089] With reference to figure 10, some embodiments of the method 400 may include the additional step of:

[0090] • detecting 401 one or more first signals 202 associated with one or more blood flows of one or more blood vessels 204 of biological tissue 205 of the user 200 by usage of a detection arrangement 102.

[0091] With reference to figure 11, according to the third aspect of the invention, there is provided a computer program 703 or a computer-readable medium comprising instructions which, when the program or the instructions is / are executed by a computer, cause the computer to carry out the method 400 according to any one of the embodiments disclosed above. The arrangement 100a; 100b may include one or more central processing units (CPUs). The arrangement 100a; 100b may include a memory or data storage.

[0092] Figure 12 shows a schematic flow chart illustrating aspects of embodiments of the arrangement 100a; 100b according to the first aspect of the invention and / or of the method 400 according to the second aspect of the invention. More specifically, the simplified flow chart of figure 12 illustrates a pipeline for computing local pulse transit time (PTT) and pulse wave velocity (PWV) from laser speckle dynamics. The biological tissue is illuminated by a coherent laser light emitter, and the backscattered light is collected by a single or multiple light-receiving unit, such as one or more photodetectors. In the following, fluctuating photocurrents or signal components outputted by the light-receiving unit are interchangeably referred to as the Doppler signal or laser speckle signal. The Doppler signal can be acquired by a laser speckle-based sensor, such as LDF, DLS, DSC, LSI, LSF, LDPI, SPG, SCOS, and DSCA, among others, in unit / step 501. The blood flow index (BFi) waveform is then computed from the acquired Doppler signals at certain depth- and velocity-resolved frequency window, in unit / step 502, followed by a blood flow index (BFi) waveform quality assessment to determine and discard bad quality signals from ensuing analysis steps, in unit / step 503. The blood flow index (BFi) may also be referred to as “flux”, “blood flow rate”, “blood flow”, “tissue perfusion”, “perfusion index”, or “perfusion” in other relevant literature. However, in the following, the term BFi denotes this waveform. In some passages of the disclosure, the terms blood flow index (BFi) waveform and blood flow index (BFi) signal may be used interchangeably. The local pulse transit time (PTT) is then determined or computed from fiducial points within blood flow index (BFi) waveforms of different frequencies, in unit / step 504. Subsequently, local pulse wave velocity (PWV) is determined or computed using the computed transcutaneous pulse transit time (PTT), in unit / step 505. Finally, the determined or computed physiological parameters, i.e., in figure 12 the pulse transit time (PTT) and / or the pulse wave velocity (PWV), are, in unit / step 506, either displayed or passed into further analysis / processing steps. In some passages of the disclosure, or for some embodiments, locally computed PTT and PWV, respectively, may be referred to as transcutaneous PTT and PWV, since these physiological parameters or quantities may be derived from a single site / location, utilizing phase incoherence of blood flow across different tissue layers.

[0093] With reference to figures 1 and 13, for some embodiments, the blood flow index determination arrangement 104 may be configured to determine and generate two or more blood flow index (BFi) signals 206a, 206b, 206c, or waveforms, based on the one or more detected first signals 202 by usage of Doppler power spectrum analysis.

[0094] Figure 13 shows a schematic flow chart illustrating further aspects of embodiments of the arrangement 100a; 100b according to the first aspect of the invention and / or of the method 400 according to the second aspect of the invention. More specifically, figure 13 schematically illustrates a simplified and overall schematic diagram of the blood flow index (BFi) waveform determination or calculation from acquired Doppler signals using Doppler power spectrum analysis. The disclosure of figure 13 proceeds by data acquisition as disclosed in connection with figure 12, followed by amplification and digitization of the acquired analog Doppler signals (using the sampling frequency fs. The digitized Doppler signals are then used to compute blood flow index (BFi) waveforms. If the light-receiving units, such as photodetectors, are equidistant from the laser light emitter, as described above, the difference between the Doppler signals detected by the light-receiving units, referred to as the difference Doppler signal, is used to compute the Doppler power spectrum. Difference Doppler signal in some literature may also be referred to as differential signal. This approach helps to reduce common-mode noise. The same methodology may be applied in a multi-distance configuration with pairs of light-receiving units, such as photodetectors, equally spaced from the laser light emitter. If no such pairs exist, the power spectrum of each Doppler signal is computed and analyzed individually, and common-mode noise can be effectively canceled in a subsequent step at a relatively low cost. For the simplicity and without loss of generality, a multi-distant configuration with a single coherent light-emitting source and without pair of equally spaced installed light receiving units is shown in Figure 7A.

[0095] With reference to figure 13, every T seconds (where 0 < — « T), the power spectral density (PSD) of each acquired digitized

[0096] Doppler signal is computed for the signal of length aT-second where a > 1. Thus, T determines the sampling rate of blood flow index (BFi). For example, for laser Doppler flowmetry (LDF) with sampling frequency of fs=100 kHz, with T=0.01 second and a = 4, the power spectral density (PSD) is computed from the neighbouring 0.04 second data (of length 4000 samples) every 0.01 seconds. Fast Fourier Transform (FFT) is employed to compute the power spectral density (PSD). For the Doppler signal acquired by the j-th light-receiving unit with distance dj to the laser light emitter, the continuous-time representation of its Doppler power spectral density (PSD) computed at time t and evaluated at frequency co by 'Pj(oj; t) is denoted. Then, the blood flow index (BFi) of the j-th light-receiving unit is proportional to the first moment of the noise calibrated (also referred to noise correlated, noise compensated, or denoised) Doppler power spectral density (PSD): where uminand ojmaxare respectively the lower and upper cut-off frequencies of the bandpass filter, and 'Pn()isc,j(oj; t) is the noise power spectral density (PSD) of the detector. For the simplicity of notation, the subscript j in *Pnoisej is omitted in this disclosure when context allows. This noise is typically modelled as combination of thermal noise and shot noise (i.e. , a variation in the photoelectron emission rate of the detector which is linearly dependent on the total DC current idcof the detector). Typically, the detector noise is time-invariant and it features a flat power spectral density (PSD) (i.e., constant across frequencies), indicating that the noise is white. This aligns with the theoretical shot noise model as white Gaussian noise (according to central limit theorem) and the common assumption of thermal noise as additive white gaussian noise (AWGN), where the sum of two independent white random processes remains white. Thus, the noise power spectral density (PSD) is typically formulated as,Pnoise(co;t) =,Pnoise(co) = T'shotidc+ T'thermal, where the parameters 'Pshotand T'thermalare related to, respectively, shot noise and thermal noise. The first moment of 'Pnoise(oj) may also be called offset signal. The offset signal is characterized using a phantom system.

[0097] With reference to figure 13, with a slight notational adjustment, the discrete-time representation of the blood flow index (BFi) calculation is given as:

[0098] Eq. (3)

[0099] The computed blood flow index (BFi) waveforms undergo low-pass filtering to remove perturbations and ensure smoothness, followed by baseline removal. This process aids in identifying fiducial points within blood flow index (BFi) waveforms at different frequencies, facilitating the computation of local pulse transit time (PTT) and pulse wave velocity (PWV).

[0100] With reference to figures 1 and 14, for some embodiments, the blood flow index determination arrangement 104 may be configured to determine and generate two or more blood flow index (BFi) signals 206a, 206b, 206c, or waveforms, based on the one or more detected first signals 202 by usage of autocorrelation analysis.

[0101] Figure 14 shows a schematic flow chart illustrating further aspects of embodiments of the arrangement 100a: 100b according to the first aspect of the invention and / or of the method 400 according to the second aspect of the invention. More specifically, figure 14 is a schematic flow chart illustrating a blood flow index (BFi) waveform calculation, or determination, from the autocorrelation analysis of acquired Doppler signals. According to the Wiener-Khinchine theorem, the power spectral density (PSD) can be equivalently represented in time domain by an autocorrelation function (ACF). In the considered case, this can be represented by the temporal autocorrelation function (ACF) of fluctuating speckles, i.e., light intensity fluctuations on the surface of the light-receiving unit(s), such as photodetectors. The following computation of blood flow index (BFi) can also be done by using autocovariance function modulo slight adjustment.

[0102] With reference to figure 14, in the temporal autocorrelation function-(ACF)-based approach, every T seconds (where 0 < — « fs

[0103] T), the autocorrelation function (ACF) of intensity for each acquired digitized Doppler signal is computed for the signal of length aT -second where a > 1. Thus, T is the sampling interval of the autocorrelation function (ACF), or the integration time of the detector. The computed temporal autocorrelation function (ACF) of intensity is denoted by g2. The time-domain representation of bandpass filtering for PSD in frequency domain of range a> E [min, a)max] is denote as h(r). h(r) represents the time-domain bandpass filter for the power spectral density (PSD) in the frequency domain with range co E [Mmin’MmaX]- The exact for of the filtering kernel h(r) depends on the selected bandpass filter. The bandpass filtering

[0104] By way of embodiments of the invention, the locally measured PTT and PWV quantities by the proposed innovation can be used to efficiently evaluate the effect of local interventions and treatments, as well as the assessment of local vascular function and pathology. By way of embodiments of the invention, the need for time synchronization commonly required in conventional multi-sensory methods can be avoided. By way of embodiments of the invention, a simpler hardware configuration (basically, requiring only a coherent light source and one or more light-receiving units) compared to conventional multimodal sensory techniques for measuring PTT and PWV is attained. Embodiments of the invention can be used in wearable technologies and portable devices due to relatively low-cost, compact size and lightweight hardware, making it suitable for long-term monitoring. By way of embodiments of the invention, power consumption can be lower in relation to conventional multimodal sensory techniques performing corresponding tasks. By way of embodiments of the invention, the locally measured transcutaneous PPT and PWV at a specific site / location offer depth- and velocity-resolved insights, enhancing the reliability of assessing local microcirculation. By way of embodiments of the invention, the locally measured pulse transit time (PTT) and pulse wave velocity (PWV) can be utilized alongside features extracted from laser speckle-based blood flow index (BFi) or speckle flow index (SFi) waveforms. These waveforms, computed at various frequency windows (e.g., as in laser Doppler flowmetery) or distinct exposure-time intervals (e.g., as in dynamic light scattering and laser speckle contrast imaging), correspond to blood flow velocities at different depths of tissue. By combining these features with those derived from the same or different modalities, it is possible to monitor blood pressure and assess various aspects of hemodynamic and cardiovascular health, such as arterial stiffness, heart rate variability, physiological states, sleep apnea detection, and blood glucose monitoring.

[0105] Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

CLAIMS1. An arrangement (lOOa-b) for determining one or more physiological parameters indicative of the cardiovascular status of a user (200), wherein the arrangement (lOOa-b) comprises a detection arrangement (102) for detecting one or more first signals (202) associated with one or more blood flows of one or more blood vessels (204) of biological tissue (205) of the user (200), wherein the arrangement (lOOa-b) comprises a blood flow index determination arrangement (104) for determining and generating two or more blood flow index signals (206a, 206b, 206c) based on the one or more detected first signals (202), and wherein the arrangement (lOOa-b) comprises a physiological parameter determination arrangement (106) for determining one or more physiological parameters indicative of the cardiovascular status of the user (200) based on the two or more determined and generated blood flow index signals (206a, 206b, 206c).

2. An arrangement (lOOa-b) according to claim 1, wherein, based on the two or more determined and generated blood flow index signals (206a, 206b, 206c), the physiological parameter determination arrangement (106) is configured to determine one or more of the group of:• a pulse transit time; and• a pulse wave velocity.

3. An arrangement (lOOa-b) according to claim 1 or 2, wherein the detection arrangement (102) is configured to detect one or more first signals (202) originating from two or more different depths (207a, 207b) of biological tissue (205) of the user (200).

4. An arrangement (lOOa-b) according to any one of the claims 1 to 3, wherein the arrangement (lOOa-b) comprises a wearable and / or portable device (108a; 108b; 108c) configured to be carried by the user (200), and wherein the wearable and / or portable device (108a; 108b; 108c) comprises at least the detection arrangement (102).

5. An arrangement (lOOa-b) according to any one of the claims 1 to 4, wherein the blood flow index determination arrangement (104) is configured to determine and generate two or more blood flow index signals (206a, 206b, 206c) based on one or more first signals (202) detected by a single sensor (110a, 110b) of the detection arrangement (102).

6. An arrangement (lOOa-b) according to claim 5, wherein the sensor (110a, 110b) of the detection arrangement (102) comprises one or more photodetectors (112a; 112b).

7. An arrangement (lOOa-b) according to any one of the claims 1 to 6, wherein the detection arrangement (102) comprises one or more of the group of:• a laser speckle-based sensor (114) comprising one or more photodetectors (112a, 112b); and• a Doppler shift-based sensor (116) comprising one or more photodetectors (112a, 112b).

8. An arrangement (lOOa-b) according to any one of the claims 1 to 7, wherein the blood flow index determination arrangement (104) is configured to determine and generate two or more blood flow index signals (206a, 206b, 206c) based on one or more first signals (202) comprising one or more of the group of:• a laser speckle signal; and• a Doppler signal.

9. An arrangement (lOOa-b) according to any one of the claims 1 to 8, wherein the blood flow index determination arrangement (104) is configured to determine and generate two or more blood flow index signals (206a, 206b, 206c) at two or more frequency windows (210a, 210b) different from one another.

10. An arrangement (lOOa-b) according to claim 9, wherein the blood flow index determination arrangement (104) is configured to perform a depth- and velocity-resolved frequency window selection in different layers (212a, 212b) of biological tissue (205) of the user (200), and wherein the blood flow index determination arrangement (104) is configured to determine and generate blood flow index signals (206a, 206b, 206c) corresponding to different depths (207a, 207b) and velocities of the different layers (212a, 212b) of biological tissue (205) of the user (200) based on the selected frequency windows (210a, 210b) so as to improve the quality of the two or more determined and generated blood flow index signals (206a, 206b, 206c).

11. An arrangement (lOOa-b) according to any one of the claims 1 to 10, wherein the blood flow index determination arrangement (104) is configured to determine and generate two or more blood flow index signals (206a, 206b, 206c) based on the one or more detected first signals (202) by usage of Doppler power spectrum analysis.

12. An arrangement (lOOa-b) according to any one of the claims 1 to 10, wherein the blood flow index determination arrangement (104) is configured to determine and generate two or more blood flow index signals (206a, 206b, 206c) based on the one or more detected first signals (202) by usage of autocorrelation analysis.

13. A method (400) for determining one or more physiological parameters indicative of the cardiovascular status of a user (200), wherein the method (400) comprises: based on one or more detected first signals (202) associated with one or more blood flows of one or more blood vessels (204) of biological tissue (205) of the user (200), determining and generating (402) two or more blood flow index signals (206a, 206b, 206c); and based on the two or more determined blood flow index signals (206a, 206b, 206c), determining (403) one or more physiological parameters indicative of the cardiovascular status of the user (200).

14. A method (400) according to claim 13, wherein the method (400) further comprises: detecting (401) one or more first signals (202) associated with one or more blood flows of one or more blood vessels (204) of biological tissue (205) of the user (200) by usage of a detection arrangement (102).

15. A computer program (703) or a computer-readable medium comprising instructions which, when the program or the instructions is / are executed by a computer, cause the computer to carry out the method (400) according to any one of the claims 13 to 14.

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