A finger-wearable device for blood pressure measurement

Abstract

A finger-wearable device for determining blood pressure of a user is disclosed. The device may comprise: a ring-shaped body comprising a plurality of gear teeth, a shape memory alloy wire arranged at least partially on an inner surface of the body and in at least one loop, two pinions arranged on an outer surface of the body and attached to the shape memory alloy wire, a pre-tension actuation mechanism, a pre-tension detection mechanism, means for heating the shape memory alloy wire for actuating a pressure, and a force sensor mechanism for determining the blood pressure of the user based on the detected pre-tension and the actuated pressure.

Description

[0001] example embodiments relate to a finger-wearable device for determining blood pressure of a user.

[0002] BACKGROUND

[0003] Measuring blood pressure regularly may be recommended, especially for persons diagnosed with high blood pressure. It may be important to measure blood pressure daily more than once during a day, as blood pressure fluctuates over the day. Also, various factors such as, e.g., physical activity, stress, or pain may affect blood pressure.

[0004] There are a wide range of devices for measuring or determining blood pressure. Blood pressure monitors with inflatable cuffs may be large to carry along in daily activities, which may lead to neglecting regular measurements. Thus, a finger-wearable device configured to determine blood pressure may be beneficial.

[0005] SUMMARY

[0006] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0007] Example embodiments of the present disclosure enable determining blood pressure of a user using a finger-wearable device. This benefit may be achieved by the features of the independent claims. Further example embodiments are provided in the dependent claims, the detailed description, and the drawings. According to a first aspect, a finger-wearable device for determining blood pressure of a user is disclosed. The device may comprise: A ring-shaped body comprising a plurality of gear teeth. A shape memory alloy wire arranged at least partially on an inner surface of the body and in at least one loop. Two pinions arranged on an outer surface of the body and attached to the shape memory alloy wire. A pre-tension actuation mechanism. A pre-tension detection mechanism. Means for heating the shape memory alloy wire for actuating a pressure. A force sensor mechanism for determining the blood pressure of the user based on the detected pre-tension and the actuated pressure.

[0008] With such a device, blood pressure of the user may be determined with an adjustable and easily portable device.

[0009] According to an example embodiment of the first aspect, the shape memory alloy wire may be a nitinol wire.

[0010] According to an example embodiment of the first aspect, an actuation temperature of the nitinol wire may be at least 42°C and at most 120°C.

[0011] According to an example embodiment of the first aspect, the device may further comprise: An elastic element arranged on the inner surface of the body. The elastic element may comprise a plurality of spreader elements.

[0012] According to an example embodiment of the first aspect, the force sensor mechanism may comprise a force sensor and a pusher.

[0013] According to an example embodiment of the first aspect, the pre-tension actuation mechanism may comprise a knob arranged to actuate movement of the two pinions for tightening the shape memory alloy wire.

[0014] According to an example embodiment of the first aspect, the shape memory alloy wire may be attached to the two pinions with at least two crimps.

[0015] According to an example embodiment of the first aspect, the device may further comprise: A heat insulating tube enclosing the shape memory alloy wire.

[0016] According to an example embodiment of the first aspect, the heat insulating tube may comprise polytetrafluoroethylene.

[0017] According to an example embodiment of the first aspect, the body may comprise a low-friction material. According to an example embodiment of the first aspect, the low-friction material may be polyoxymethylene.

[0018] According to an example embodiment of the first aspect, the pre-tension detection mechanism may comprise at least one of the following: A magnetometer and at least one magnet. A rotary encoder. A capacitive sensor. An inductive sensor. An optical sensor.

[0019] According to an example embodiment of the first aspect, the means for heating the shape memory alloy wire may comprise means for running an electric current through the shape memory alloy wire.

[0020] According to a second aspect, a method measuring blood pressure of a user is disclosed. The method may comprise: Actuating, on a finger- wearable device, a pre-tension. Monitoring the actuated pre-tension for a suitable pretension value. Actuating, in response to detecting the suitable pre-tension value, on the finger-wearable device, a pressure by heating a shape memory alloy wire comprised in the finger-wearable device. Measuring decrease of the actuated pressure and oscillometric pulsations in a finger of the user. Calculating, based on the decrease of the pressure and the oscillometric pulsations, a blood pressure value of the user.

[0021] According to an example embodiment of the second aspect, the actuating the pressure may comprise heating the shape memory alloy wire to a temperature of at least 42°C and at most 120°C.

[0022] Any example embodiment may be combined with one or more other example embodiments. Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings.

[0023] DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and together with the description help to understand the example embodiments. In the drawings: FIG. 1 illustrates a simplified architecture of a system determining blood pressure of a user;

[0025] FIG. 2 illustrates a schematic block diagram of a device according to an example embodiment;

[0026] FIG. 3 illustrates a schematic block diagram of an elastic element in a device according to an example embodiment;

[0027] FIG. 4 illustrates schematic block diagrams of force sensor mechanism positions in devices according to example embodiments;

[0028] FIG. 5 illustrates a schematic block diagram of a force sensor mechanism in a device according to an example embodiment;

[0029] FIG. 6 illustrates a schematic block diagram of a device according to an example embodiment;

[0030] FIG. 7 illustrates schematic block diagrams of functionalities of pre-tension detection mechanisms in devices according to example embodiments;

[0031] FIG. 8 illustrates a schematic flow chart of a method according to an example embodiment; and

[0032] FIG. 9 illustrates a schematic block diagram of an apparatus configured to practice one or more example embodiments.

[0033] DETAILED DESCRIPTION

[0034] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0035] Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature may not apply to other embodiments. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words “comprising” and “including” should be understood as not limiting the described embodiments / example, and the embodiments / examples may contain also features / structures that have not been specifically mentioned.

[0036] According to an example embodiment, a finger-wearable device for determining blood pressure of a user is disclosed. The finger-wearable device may be wearable on a finger of the user. The device comprises a pre-tensioning mechanism and a shape memory alloy wire for actuating a pressure on the finger. Blood pressure may be determined by measuring decreasing pressure values by a force sensor mechanism.

[0037] According to the example embodiment, the pre-tensioning mechanism allows the device to be adjusted on different finger sizes. Heating the shape memory alloy wire allows the device to constrict arteries in the finger of the user. While the device gradually releases the constriction, arterial blood pressure pulses may be detected by the force sensor mechanism.

[0038] FIG. 1 illustrates a general exemplary architecture of a system determining blood pressure of a user. FIG. 1 is a simplified system architecture showing only some devices, apparatuses, and functional entities, all being logical units whose implementation and / or number may differ from what is shown. The connections shown in FIG. 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system comprises any number of shown elements, other equipment, other functions, and other structures that are not illustrated. They, as well as the protocols used, are well known by persons skilled in the art and are irrelevant to the actual invention. Therefore, they need not to be discussed in more detail here.

[0039] Referring to FIG. 1, the system 100 comprises at least a processing circuitry configured to analyze measurement data 106 measured from a user 102 by, e.g., carrying out functionalities described in more detail below. The processing circuitry may be realized in a finger- wearable device 104 worn by the user, such as a finger-wearable tracker device. The processing circuitry may be realized in a user device 108 such as a smart phone or a tablet computer. The processing circuitry may be realized in a server computer such as a cloud server. The measurement data 106 may be provided by at least one sensor comprised in the finger-wearable device 104. The finger-wearable device 104, the user device 108, and / or the server computer may be connectable over one or more networks, over a short-range wireless connection such as Bluetooth, or over a Universal Serial Bus connection.

[0040] The user device 108 refers to a computing device (equipment, apparatus) and it may also be referred to as a user terminal, a user apparatus, a mobile device, or a mobile terminal. Portable computer devices (apparatuses) include wireless communication devices operating with or without a subscriber identification module (SIM) in hardware or in software, including, but not limited to, the following types of devices: a mobile phone, a smartphone, a personal digital assistant (PDA), a handset, a laptop and / or touch screen computer, a tablet (tablet computer), a multimedia device, a wearable computer such as a smartwatch, and other types of wearable devices, such as clothing and accessories incorporating computer and advanced electronic technologies. The user device 108 may comprise one or more user interfaces. The one or more user interfaces may be any kind of a user interface, e.g., a screen, a keypad, a loudspeaker, a microphone, a touch user interface, an integrated display device, and / or external display device.

[0041] FIG. 2 illustrates a cross-sectional view of an example embodiment of a finger- wearable device 104 configured for determining blood pressure of a user 102.

[0042] Referring to FIG. 2, the device 104 comprises a ring-shaped body 202 comprising gear teeth (not shown in FIG. 2). In an example embodiment, the body 202 comprises a low-friction material. In an example embodiment, the low-friction material is polyoxymethylene. The device further comprises a shape memory alloy wire 204 arranged at least partially on an inner surface of the body 202. Shape memory alloy may be understood as a material that has been trained to contract when heated and to return to an original length when cooled. Shape memory alloy wires may be lightweight and durable and may withstand hundreds of thousands of cycles of heating and cooling. When the shape memory alloy wire is heated to a temperature exceeding an actuation temperature of the shape memory alloy wire, a length of the wire decreases by, e.g., 3-5%. The actuation temperature depends on the shape memory alloy wire used and may be, e.g., 70°C or 90°C. The contraction may occur in a short time, such as, e.g., one second. The shape memory alloy wire 204 is further arranged in at least one loop. In an example embodiment, the shape memory alloy wire 204 is further arranged in at least one further loop on an outer surface of the body 202. In an example embodiment, the shape memory alloy wire is arranged in a plurality of loops. In an example embodiment, the shape memory alloy wire 204 is a nitinol wire. In this context, nitinol may be understood as a shape memory alloy material made from nickel and titanium. For most commercially available nitinol wires an actuation temperature range is within 70-90°C. In an example embodiment, an actuation temperature of the nitinol wire may be at least 42°C and at most 120°C. In an example embodiment, the shape memory alloy wire 204 is enclosed inside a heat insulating tube. In an example embodiment, the heat insulating tube comprises polytetrafluoroethylene. The tube may minimize friction between the shape memory alloy wire 204 and the body 202.

[0043] Referring to FIG. 2, the finger- wearable device 104 further comprises two pinions 206 (only one shown in FIG. 2). A pinion may be understood as a round gear such as, e.g., a smaller gear of two meshed gears. The two pinions 206 are arranged on the outer surface of the body 202. The two pinions 206 are attached to the shape memory alloy wire 204. In an example embodiment, ends of the shape memory alloy wire are attached to the two pinions, one end per one pinion. In an example embodiment, the shape memory alloy wire 204 is attached to the two pinions 206 with two crimps. The device 104 further comprises a pretension actuation mechanism 208 for actuating a pre-tension to the device 104 and the shape memory alloy wire 204. In an example embodiment, the pretension actuation mechanism 208 comprises a knob. The user of the device may actuate the pre-tension by, e.g. rotating or pressing the knob. The user of the device may also lessen or remove the pre-tension by, e.g., rotating or lifting the knob. In an example embodiment, the knob is rotatable. When the user rotates the knob, e.g., clockwise or counterclockwise, the two pinions 206 rotate in opposite directions and thereby tighten the shape memory alloy wire 204. When the user rotates the knob, e.g., counterclockwise or clockwise, the two pinions 206 rotate backwards and thereby loosen the shape memory alloy wire 204.

[0044] Referring to FIG. 2, the device 104 further comprises a pre-tension detection mechanism 210. The actuated pre-tension is monitored to detect whether the pre-tension is appropriate for measuring blood pressure of the user. The actuated pre-tension is detected to enable calculating the blood pressure. In an example embodiment, the pre-tension detection mechanism 210 comprises a magnetometer and at least one magnet. In an example embodiment, the at least one magnet is attached or integrated to a moving element such as, e.g., a pinion 206 within the two pinions and the magnetometer is a linear magnetometer configured to detect linear movement of the at least one magnet. In an example embodiment, the at least one magnet is attached or integrated to a rotating element such as, e.g., the knob, and the magnetometer is an angular magnetometer configured to detect rotating movement of the at least one magnet. The functionalities of the pre-tension detection mechanism 210 according to an example embodiment comprising the at least one magnet and the magnetometer are described in more detail below with reference to FIG. 7.

[0045] In an example embodiment, the pre-tension detection mechanism 210 comprises a rotary encoder configured to detect or measure movement of, e.g., the two pinions 206, or the gear teeth comprised in the body 202. The rotary encoder may be, e.g., an optical rotary encoder, a mechanical rotary encoder, an electromagnetic rotary encoder, or a magnetic rotary encoder. In an example embodiment, the pre-tension detection mechanism 210 comprises a capacitive sensor, an inductive sensor, or an optical sensor configured to detect movement of, e.g., the two pinions 206.

[0046] Referring to FIG. 2, the device 104 further comprises means for heating 212 the shape memory alloy wire 204 for contracting the wire and thereby actuating a pressure. In an example embodiment, the means for heating 212 comprises means for running an electric current through the shape memory alloy wire 204. In an example embodiment, the means for running the electric current comprises a metal-oxide-semiconductor field-effect transistor (MOSFET) and a processor configured to control pulse width modulation (PWM). In an example embodiment, a control algorithm such as, e.g., a proportional-integral-derivate (PID) algorithm may be used. The actuated pressure should be higher than systolic pressure in arteries of the user 102, thus occluding the arteries.

[0047] Referring to FIG. 2, the device 104 further comprises a force sensor mechanism 214 for determining the blood pressure of the user. The blood pressure is determined based on the detected pre-tension and the actuated pressure. When the shape memory alloy wire 204 cools, the pressure decreases enabling blood pressure pulses to be measured with the force sensor mechanism 214. The functionalities of the force sensor mechanism are described in more detail below with reference to FIG. 5.

[0048] FIG. 3 illustrates a schematic block diagram of an elastic element 300 comprised in an example embodiment of a device 104 configured to determine blood pressure of a user. The elastic element 300 is arranged on the inner surface of the body 202. In an example embodiment, the elastic element 300 comprises fabric or some other elastic material. The elastic element further comprises a plurality of spreader elements 302 spreading the actuated pressure along the inner surface of the body 202 to cause a uniform pressure towards the user. When the shape memory alloy wire is contracted by heating, the plurality of spreader elements moves closer to each other thereby spreading the actuated pressure more uniformly.

[0049] FIG. 4 illustrates exemplary force sensor mechanism positions in various example embodiments of devices 104.

[0050] Referring to FIG. 4, in illustration “A” the force sensor mechanism 214 is arranged on the inner surface of the body 202. In illustration “B” the force sensor mechanism 214 is arranged between the body 202 (on the outer surface of the body 202) and the shape memory alloy wire 204. In illustration “C” the force sensor mechanism 214 is attached to the shape memory alloy wire 204 on such part of the wire that is arranged on the inner surface of the body 202. In illustration “D” the force sensor mechanism 214 is attached to a crimp attaching the shape memory alloy wire 204 to the pinion 206.

[0051] FIG. 5 illustrates a schematic block diagram of a force sensor mechanism 214 comprised in an example embodiment of the device 104.

[0052] Referring to FIG. 5, the force sensor mechanism 214 comprises a printed circuit board (PCB) 502. The PCB 502 is arranged between metal plates 506a, 506b and a metal support 510. The force sensor mechanism 214 further comprises an elastic pusher 504 arranged to be in contact with the user 102 when the device 104 is in use. The elastic pusher 504 enables a sensitive contact between the force sensor mechanism 214 and the user 102 to enable detecting blood pressure pulses of the user 102. In an example embodiment, the elastic pusher 504 comprises elastomer. The force sensor mechanism 214 further comprises a force sensor component 508 between the PCB 502 and the metal plate 506a. The force sensor component 508 is configured to measure the pressing force produced by the shape memory alloy wire 204. In an example embodiment, the force sensor mechanism may detect an oscillometric waveform envelope (OMWE) of the blood pressure pulses, wherefrom a mean arterial pressure (MAP) value, a systolic blood pressure (SBP) value, and / or a diastolic blood pressure (DBP) value may be calculated. In an example embodiment, the force sensor mechanism 214 is configured to measure pressing force in millivolts (mV). Pressing force values in millivolts may be converted to Newtons (N) and converted to pressure values by, e.g., calibrating the device 104 with a known pressure or through mechanical simulation. A resulting calibration curve may be used to indicating blood pressure in millimetres of mercury (mmHg) scale.

[0053] FIG. 6 illustrates an exploded view of an example embodiment of a finger- wearable device 104 configured for determining blood pressure of a user 102.

[0054] Referring to FIG. 6, the finger- wearable device 104 comprises a ringshaped body 202 comprising gear teeth and two pinions 206a, 206b. The device 104 further comprises a pre-tension actuation mechanism 208 comprising a knob 602 to enable the user 102 of the device 104 to actuate a pre-tension to the device 104 by, e.g. rotating the knob 602. The device 104 further comprises an elastic element 300 and a force sensor mechanism 214 that may comprise a printed circuit board 502, an elastic pusher 504, metal plates 506a, 506b, a metal support 510, and a force sensor element 508. The device 104 may further comprise one or more covers 604a, 604b.

[0055] FIG. 7 illustrates a functionality of the finger- wearable device 104 according to an example embodiment for detecting the pre-tension.

[0056] Referring to FIG. 7, the pre-tension detection mechanism 210 comprises at least one magnet 702 and a magnetometer 704. The at least one magnet is attached or integrated in an element within the device 104, wherein the element, e.g., moves, slides, or rotates when the pre-tension is actuated. In an example embodiment, the at least one magnet 702 is attached to a pinion within the two pinions and the magnetometer 704 is a linear magnetometer configured to detect linear movement of the at least one magnet 702. In the illustration “A”, the at least one magnet 702 is in a starting position of no actuated pre-tension. In the illustration “B”, the at least one magnet 702 is displaced from the starting position to a position of the actuated pre-tension. In an example embodiment, the magnetometer is a rotary magnetometer. In the illustration “C”, the at least one magnet 702 is attached or integrated in a rotating element. The rotary magnetometer (not shown in illustration “C”) may be arranged, e.g., under the rotating element. When the two pinions are moved to actuate the pre-tension within the device, the rotating element and simultaneously the at least one magnet 702 rotates. The rotation of the at least one magnet 702 is detectable by the rotary magnetometer.

[0057] FIG. 8 illustrates a flow chart according to an example embodiment of a method for determining blood pressure of a user. The device 200 illustrated with FIG. 2 is configured to perform functionalities of the method with the system 100 illustrated with FIG. 1, as explained above with reference to FIG. 3 to 7.

[0058] Referring to FIG. 8, a pre-tension is actuated in operation 801 on a fingerwearable device. The pre-tension may be actuated, e.g., as described in more detail above with reference to FIG. 2. The actuated pre-tension is monitored in operation 802 for a suitable pre-tension value. The pre-tension value may be monitored, e.g., as described in more detail above with reference to FIG. 2 and FIG 7. It is determined in operation 803 whether the actuated pre-tension value is suitable for determining the blood pressure. If the pre-tension value is suitable (operation 803: yes), a pressure is actuated in operation 804 on the device. In an example embodiment, the pre-tension value is suitable if it is at least 5 mmHg and at most 40 mmHg. The pressure is actuated by heating a shape memory alloy wire such as, e.g., a nitinol wire comprised in the finger-wearable device, as explained in more detail above with reference to FIG. 2. In an example embodiment, the actuating the pressure comprises heating the shape memory alloy wire to a temperature of at least 42°C and at most 120°C. The actuated pressure is higher than systolic blood pressure (SBP) value of the user, which may be monitored by its ability to occlude brachial artery. If the actuated pretension value is not suitable (operation 803: no), the monitoring the actuated pre-tension is continued in operation 802. Decrease of the actuated pressure and oscillometric pulsations of the user are measured in operation 805. The pressure and the oscillometric pulsations may be measured by a force sensor mechanism as explained in more detail above with reference to FIG. 2 and FIG. 5. When the heating the shape memory alloy wire is terminated, the shape memory alloy wire gradually returns to its original un— heated length thereby decreasing the actuated pressure. A blood pressure of the user is calculated in operation 806 based on the measured decrease of the pressure and the measured oscillometric pulsations. In an example embodiment, the oscillometric pulsations are measured by extracting an oscillometric pulsations signal from the decreasing pressure curve by one or more filtering and / or detrending methods. An oscillometric waveform may be understood as the extracted oscillometric pulsations signal. An oscillometric waveform envelope (OMWE) comprising information on an amplitude of the oscillometric pulsations may be analyzed to gain blood pressure values. The OMWE may be formed by, e.g., calculating peak-to-peak voltage of the OMW, calculating base-lie-to-peak voltage of the OMW, calculating a maximum slope of the OMW, or calculating an area of the oscillometric pulsations by integration. Various algorithms known to a person skilled in the art exist for analyzing the OMWE to approximate a mean arterial pressure (MAP), diastolic blood pressure (DBP), and systolic blood pressure (SBP). One of such algorithms is maximum amplitude algorithm (MAA), which is based on an assumption that arterial compliance is at maximum when a device pressure and an arterial pressure are equal, that is, when an arterial wall is minimally distended. Thus, the device pressure at a maximum amplitude of the OMWE may approximate the MAP. The SBP and the DBP may be approximated to originate at specific fractions of the maximum amplitude of the OMWE. These fractions have been reported in empirical studies to be in a range of 0.45-0.73 for the SBP, and in a range of 0.69-0.83 for the DBP. The fractions may vary based on, e.g., age and various cardiovascular conditions due to them affecting shape of the OMWE.

[0059] FIG. 9 illustrates an example embodiment of an apparatus 900 configured to perform operations of one or more example embodiments described above for determining blood pressure, e.g., by means of FIG. 2 to 8 and any combination thereof. The apparatus 900 may be applicable to or comprised in the user device 108. In other embodiment, the apparatus may be applicable to or comprised in a wearable device or a server computer. The apparatus 900 may comprise at least one processor 902. The at least one processor 902 may comprise, for example, one or more of various processing devices or processor circuitry, such as for example a co-processor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like.

[0060] The apparatus 900 may further comprise at least one memory 904. The at least one memory 904 may be configured to store, for example, computer program code or the like, for example operating system software and application software. The at least one memory 904 may comprise one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination thereof. For example, the at least one memory 904 may be embodied as magnetic storage devices (such as hard disk drives, floppy disks, magnetic tapes, etc.), optical magnetic storage devices, or semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

[0061] The apparatus 900 may further comprise a communication interface 908 configured to enable apparatus 900 to transmit and / or receive information to / ffom other devices, functions, or entities. The apparatus 900 may further comprise a user interface 910, for example for providing user output by the apparatus, such as for example visual and / or audible signal(s), for example by speaker(s), display(s), light(s), or the like. User interface 910 may be used for example for outputting indication(s) of determined blood pressure values to a human user.

[0062] When the apparatus 900 is configured to implement some functionality, some component and / or components of the apparatus 900, such as for example the at least one processor 902 and / or the at least one memory 904, may be configured to implement this functionality. Furthermore, when the at least one processor 902 is configured to implement some functionality, this functionality may be implemented using program code 906 comprised, for example, in the at least one memory 904.

[0063] The functionality described herein may be performed, at least in part, by one or more computer program product components such as for example software components. According to an example embodiment, the apparatus 900 comprises a processor or processor circuitry, such as for example a microcontroller, configured by the program code when executed to execute the embodiments of the operations and functionality described. A computer program or a computer program product may therefore comprise instructions for causing, when executed, the apparatus 900 to perform the method(s) described herein. Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), application-specific Integrated Circuits (ASICs), application-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), Graphics Processing Units (GPUs).

[0064] The apparatus 900 comprises means for performing at least one method described herein. In one example, the means comprises the at least one processor 902, the at least one memory 904 including the program code 906 configured to, when executed by the at least one processor, cause the apparatus 900 to perform the method.

[0065] Although the apparatus 800 is illustrated as a single device it is appreciated that, wherever applicable, functions of the apparatus 900 may be distributed to a plurality of devices, for example to implement example embodiments as a cloud computing service.

[0066] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example embodiments of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0067] It will be understood that the benefits and advantages described above may relate to one example embodiment or may relate to several example embodiments. The example embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

[0068] The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual operations may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the example embodiments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought.

[0069] It will be understood that the above description is given by way of example embodiments only and that various modifications may be made by those skilled in the art. The above specification, example embodiments and data provide a complete description of the structure and use of exemplary embodiments. Although various example embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed example embodiments without departing from scope of this specification.

Claims

CLAIMS1. A finger-wearable device for determining blood pressure of a user, comprising: a ring-shaped body comprising a plurality of gear teeth; a shape memory alloy wire arranged at least partially on an inner surface of the body and in at least one loop; two pinions arranged on an outer surface of the body and attached to the shape memory alloy wire; a pre-tension actuation mechanism; a pre-tension detection mechanism; means for heating the shape memory alloy wire for actuating a pressure; and a force sensor mechanism for determining the blood pressure of the user based on the detected pre-tension and the actuated pressure.

2. A device according to claim 1, wherein the shape memory alloy wire is a nitinol wire.

3. A device according to claim 2, wherein an actuation temperature of the nitinol wire is at least 42°C and at most 120°C.

4. A device according to any of the preceding claims, further comprising: an elastic element arranged on the inner surface of the body, wherein the elastic element comprises a plurality of spreader elements.

5. A device according to any of the preceding claims, wherein the force sensor mechanism comprises a force sensor and a pusher.

6. A device according to any of the preceding claims, wherein the pretension actuation mechanism comprises a knob arranged to actuate movement of the two pinions for tightening the shape memory alloy wire.

7. A device according to any of the preceding claims, wherein the shape memory alloy wire is attached to the two pinions with at least two crimps.

8. A device according to any of the preceding claims, further comprising: a heat insulating tube enclosing the shape memory alloy wire.

9. A device according to claim 8, wherein the heat insulating tube comprises polytetrafluoroethylene.

10. A device according to any of the preceding claims, wherein the body comprises a low-friction material.

11. A device according to claim 10, wherein the low-friction material is polyoxymethylene.

12. A device according to any of the preceding claims, wherein the pretension detection mechanism comprises at least one of the following: a magnetometer and at least one magnet; a rotary encoder; a capacitive sensor; an inductive sensor; or an optical sensor.

13. A device according to any of the preceding claims, wherein the means for heating the shape memory alloy wire comprises means for running an electric current through the shape memory alloy wire.

14. A method for measuring blood pressure of a user, comprising: actuating, on a finger-wearable device, a pre-tension; monitoring the actuated pre-tension for a suitable pre-tension value; actuating, in response to detecting the suitable pre-tension value, on the finger-wearable device, a pressure by heating a shape memory alloy wire comprised in the finger-wearable device;measuring decrease of the actuated pressure and oscillometric pulsations in a finger of the user; and calculating, based on the decrease of the pressure and the oscillometric pulsations, a blood pressure value of the user.

15. A method according to claim 14, wherein the actuating the pressure comprises heating the shape memory alloy wire to a temperature of at least 42°C and at most 120°C.

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