Non-invasive blood pressure measuring device

Abstract

A non-invasive blood pressure sensing device (101) comprising a control unit (102) that is secured to a strap (103) that comprises an inflatable bladder (104), a first sensor arrangement (408) arranged to sense a pressure within the inflatable bladder (104), and a second sensor arrangement (409) comprising textile electrodes (105, 106, 107, 108) arranged to contact the skin of the wrist (301) of the individual (300) around which the strap (103) is fastened. A pressure signal from the first sensor arrangement (408) and an impedance plethysmography signal from the second sensor arrangement (409) are acquired by a processor (401) of the control unit (102) and processed by the processor (401) to determine an extent of arterial blood flow occlusion and an oscillometric blood pressure measurement, whereby to check that the arterial blood flow was properly occluded during the blood pressure measurement.

Description

[0001] NON-INVASIVE BLOOD PRESSURE MEASURING DEVICE

[0002] FIELD OF THE INVENTION

[0003] The present application relates to measuring blood pressure and more particularly to a non- invasive blood pressure measuring device.

[0004] BACKGROUND OF THE INVENTION

[0005] A beating heart pumps blood through the body; as the heart contracts and relaxes, blood pressure, which is the force of the blood pushing against the artery walls, varies. A blood pressure measurement comprises two numbers, the first being for systolic pressure, which indicates maximum pressure when the heart is beating, and the second being for diastolic pressure, which indicates minimum pressure between heart beats. What would be a 'normal' blood pressure reading for a person will depend on their age and health. A blood pressure reading outside of 'normal' could indicate a potential health risk for which medication and / or changes in lifestyle may be recommended or a symptom of a disease for which prompt medical attention is advised. Thus, blood pressure monitoring is useful for the prevention and treatment of disorders and illness.

[0006] A blood pressure measurement may be obtained using an invasive (intra-arterial) technique, involving the use of a cannula needle in a peripheral artery, or a non-invasive technique, involving the use of an inflatable cuff around a limb (arm or leg) or digit (finger or toe).

[0007] The invasive technique offers continuous blood pressure monitoring and accurate readings at low blood pressures and is often used in medical environments when a sudden change in blood pressure may be anticipated, for example in a patient undergoing surgery or receiving intensive care.

[0008] The non-invasive technique of measuring blood pressure is more commonly used for routine assessments and self-monitoring, and includes auscultatory and oscillometric methods of obtaining readings. While the auscultatory method involves the use of a stethoscope to record sounds (Korotkoff sounds) as blood flow changes with cuff deflation from an initially inflated state, the oscillometric method utilises an electronic pressure sensor to record cuff pressure oscillations as the cuff deflates or inflates. The oscillometric method, which typically also utilises automatic inflation and deflation of the cuff and automatic interpretation of readings to output a blood pressure measurement, requires a lower level of skill than the auscultatory method, and so is perceived as more suitable for use by untrained individuals. However, like in the auscultatory method, with oscillometric method it is important to use a cuff of an appropriate size (bladder width and length compared to circumference of the cuff when in use on an individual) to avoid falsely high or low readings being obtained.

[0009] It is desirable to provide a non-invasive blood pressure measuring device that offers improvements over existing designs, in particular for self-monitoring.

[0010] SUMMARY OF THE INVENTION

[0011] According to a first aspect there is provided a non-invasive blood pressure sensing device comprising: a control unit secured to a strap, the strap configured to be fastened around a wrist of an individual and comprising an inflatable bladder, and the control unit comprising a processor, data storage, an input device, a display device, and an inflation control arrangement operable to control inflation and deflation of the inflatable bladder; a first sensor arrangement comprising at least one pressure sensor arranged to sense a pressure within the inflatable bladder; and a second sensor arrangement comprising at least first, second, third and fourth textile electrodes arranged to contact the skin of the wrist of the individual around which the strap is fastened; the processor operatively connected to the first sensor arrangement and to the second sensor arrangement and functional to: acquire a pressure signal from the first sensor arrangement; acquire an impedance plethysmography signal from the second sensor arrangement; process an acquired impedance plethysmography signal to determine an extent of arterial blood flow occlusion, and process an acquired pressure signal to determine an oscillometric blood pressure measurement.

[0012] The use of textile electrodes in the non-invasive blood pressure sensing device provide an improvement in respect of providing an appropriate length of the inflatable bladder. The flexible, textile electrodes can be positioned within the footprint of the inflatable bladder, unlike rigid, metal electrodes which need to be positioned in a different region to the inflatable bladder. The use of the textile electrodes in the non-invasive blood pressure sensing device hence overcomes a requirement to provide a region for the electrodes in which the inflatable bladder does not extend, with the effect that a longer inflatable bladder can be used and, in turn, a greater contact area between the inflatable bladder and the individual can be achieved.

[0013] In a preferred example, the processor is functional to process an impedance plethysmography signal to determine whether an acceptable extent of arterial blood flow occlusion is met. In an example, the processor is functional to process an impedance plethysmography signal acquired contemporaneously with an acquired pressure signal to determine whether an acceptable extent of arterial blood flow occlusion is met. In a specific example, the processor is functional to determine that an acceptable extent of arterial blood flow occlusion is met before processing an acquired pressure signal to determine the oscillometric blood pressure measurement.

[0014] The use of an impedance plethysmography measurement to determine whether the arterial blood flow has been properly occluded during the oscillometric blood pressure measurement is advantageous for preventing false readings being provided by the non-invasive blood pressure sensing device.

[0015] In an example, the processor is functional to process an acquired impedance plethysmography signal to determine heart rate.

[0016] An impedance plethysmography measurement may thus be used when a blood pressure measurement is being performed, to check that the arterial blood flow was properly occluded, and between blood pressure measurements are being performed, to monitor heart rate.

[0017] In an example, the non-invasive blood pressure sensing device further comprises a third sensor arrangement, the third sensor arrangement comprising a first and a second electrode arranged for being contacted by the fingers of the arm of the individual on which the non-invasive blood pressure sensing device is not being worn, the processor operatively connected to the third sensor arrangement and configured to acquire, from electrical connection between the second and the third sensor arrangements, at least one of an impedance plethysmography signal, an electrocardiogram signal, a bioelectrical impedance signal. Thus, the third sensor arrangement may be used to acquire one or more types of physiological signal. Whilst wearing the non-invasive blood pressure sensing device on the wrist of one arm, the individual can touch electrodes of the third sensor arrangement with fingers of their other arm and the processor of the non-invasive blood pressure sensing device can acquire a physiological signal from between the two arms of the individual. This allows other body metrics to be determined. Hence, the non-invasive blood pressure sensing device can advantageously provide further information that is useful for assessing the individual's health / fitness.

[0018] In an example, the processor is functional to process impedance plethysmography signals or, in combination, impedance plethysmography and electrocardiogram signals, to determine an evaluation of at least one of: pulse arrival time (PAT), pulse transit time (PTT).

[0019] In an example, the at least one evaluation of pulse arrival time comprises one or both of an evaluation of pulse arrival time (PAT wrist) from the wrist of the individual on which the blood pressure sensing device is being worn, an evaluation of pulse arrival time (PAThand-to-hand) from between the arms of the individual.

[0020] In an example, the processor is functional to process at least one evaluation of pulse arrival time to determine at least one evaluation of pulse wave velocity (PWV).

[0021] In an example, the at least one evaluation of pulse a wave velocity comprises one or both of: an evaluation of pulse wave velocity at the wrist of the individual on which the non-invasive blood pressure sensing device is being worn, an evaluation of pulse wave velocity between the arms of the individual.

[0022] It has been found that an ECG signal and an impedance plethysmography signal taken between the arms of the individual can be used to determine an evaluation of stiffening of the central arteries, and that an ECG signal and an impedance plethysmography signal taken from the arm of the individual on which the non-invasive blood pressure sensing device is being worn can be used to determine an evaluation of stiffening of the peripheral arteries.

[0023] In an example, the processor is functional to process an acquired bioelectrical impedance signal to determine an evaluation of upper body composition. In an example, the processor is functional to process an acquired bioelectrical impedance signal in combination with at least one user profile value to determine the evaluation of upper body composition, in which the at least one user profile value selected from: age; height; weight; gender.

[0024] Processing a physiological signal or physiological signals acquired for the individual in combination with at least one such user profile value beneficially serves to provide a tailored result for the individual.

[0025] In an example, the strap comprises an adjustment arrangement for varying a wearing circumference of the non-invasive blood pressure sensing device. The adjustment arrangement beneficially enables the non-invasive blood pressure sensing device to be usable properly on different wrist sizes.

[0026] In an example, the non-invasive blood pressure sensing device comprises a wearing circumference measuring arrangement for determining a magnitude of the wearing circumference. This information can be used to improve a blood pressure reading for the individual.

[0027] In an example, the processor is functional to process an acquired pressure signal in combination with a determined magnitude of the wearing circumference to determine the oscillometric blood pressure measurement.

[0028] In an example, the adjustment arrangement comprises a prong buckle and a plurality of apertures defined in the strap. Belts and wrist watches are known that feature such an arrangement for adjusting the length of a strap to fit a wearer, and hence the adjustment arrangement of the non-invasive blood pressure sensing device can advantageously have a familiar form.

[0029] In a specific example, the non-invasive blood pressure sensing device has the physical form of an electronic watch. In a specific example, the non-invasive blood pressure sensing device comprises an adjustment arrangement comprising a prong buckle and a plurality of apertures defined in the strap and further comprising a wearing circumference measuring arrangement for determining a magnitude of the wearing circumference, in which the wearing circumference measuring arrangement comprises: a first and a second conductive line extending along an outer side of the strap and a conductive region of the prong buckle, the conductive region of the prong buckle arranged for making electrical connection with the first and the second conductive lines, and the processor functional to acquire a resistance between the first and the second conductive lines when the conductive region of the prong buckle makes electrical connection therewith and to process the acquired resistance to determine a magnitude of the wearing circumference.

[0030] In an example, each textile electrode of the second sensor arrangement is embedded within a layer of material and exposed on an inner side of the strap. This feature allows the textile electrodes to be supported within the strap with an exposed surface of each textile electrodes flush with, or only marginally protruding from, the surrounding surface of the strap, which is beneficial for comfortable wearing.

[0031] In an example, the layer of material is a layer of a breathable fabric material. This feature is beneficial for comfortable wearing.

[0032] In an example, the input device and the display device are comprised by a touchscreen.

[0033] In a specific example, the non-invasive blood pressure sensing device incorporates the functionality of a smartwatch (or, in other words, is a smartwatch with the blood pressure sensing functionality disclosed herein).

[0034] In an example, the control unit comprises a wireless communication interface. This feature is beneficially usable to, for example, transfer data acquired by the processor to a remote device.

[0035] Further particular and preferred aspects of the invention are set out in the accompanying dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will now be more particularly described, with reference to the accompanying drawings, in which:

[0037] Figure l is a perspective view of a non-invasive blood pressure sensing device according to a first example;

[0038] Figure 2 is a side view of the blood pressure sensing device of Figure 1;

[0039] Figure 3 illustrates the pressure sensing device of Figure 1 being worn by an individual;

[0040] Figure 4 is a schematic of the blood pressure sensing device of Figure 1;

[0041] Figure 5 is a schematic of an arrangement for obtaining an impedance plethysmography (IPG) measurement using the blood pressure sensing device of Figure 1;

[0042] Figures 6 to 8 illustrates a wearing circumference measuring feature of the blood pressure sensing device of Figure 1;

[0043] Figure 9 is a flow chart illustrating a use of the blood pressure sensing device of Figure 1;

[0044] Figure 10 is a schematic of another arrangement for obtaining an impedance plethysmography measurement using the blood pressure sensing device of Figure 1;

[0045] Figure 11 is a schematic of an arrangement for obtaining an electrocardiogram (ECG) signal using the blood pressure sensing device of Figure 1;

[0046] Figure 12 is a schematic of an arrangement for obtaining a bioelectrical impedance (BIA) signal using the blood pressure sensing device of Figure 1;

[0047] Figures 13 & 14 show a feature of another example of blood pressure sensing device;

[0048] Figure 15 illustrates features of a control unit of the blood pressure sensing device of Figure 1; and

[0049] Figure 16 illustrates features of an example method of evaluating cardiovascular risk using the blood pressure sensing device of Figure 1.

[0050] DESCRIPTION

[0051] Examples are described below, with reference to the accompanying drawings, in sufficient detail to enable those of ordinary skill in the art to implement the apparatus, systems and / or processes described herein. However, it is to be understood that the invention is not limited to the precise examples described and / or shown and that various changes and modifications can be affected by one skilled in the art without departing from the scope of the invention as defined by the appended claims. In the following description, all orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting the scope of the invention as defined by the appended claims unless the context clearly indicates otherwise.

[0052] The drawings are not necessarily drawn to scale, and in some instances the drawings may have been exaggerated or simplified for illustrative purposes only.

[0053] Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. In addition, features referred to herein in the singular can number one or more, unless the context clearly indicates otherwise. Similarly, the terms “comprises”, “comprising”, “includes”, “including”, “has” and / or “having” when used herein, specify the presence of the stated feature or features and do not preclude the presence or addition of one or more other features, unless the context clearly indicates otherwise.

[0054] Disclosed herein is a system that comprises a non-invasive blood pressure sensing device. The blood pressure sensing device comprises a control unit secured to a strap. The strap is configured to be fastened around a wrist of an individual. The strap comprises an inflatable bladder. The control unit comprises a processor, data storage, an input device, a display device, and an inflation control arrangement that is operable to control inflation and deflation of the inflatable bladder. The blood pressure sensing device comprises a first sensor arrangement and a second sensor arrangement. The first sensor arrangement comprises at least one pressure sensor arranged to sense a pressure within the inflatable bladder. The second sensor arrangement comprises at least first, second, third and fourth textile electrodes arranged to contact the skin of the wrist of the individual around which the strap is fastened. The processor is operatively connected to the first sensor arrangement and to the second sensor arrangement and is functional to: acquire a pressure signal from the first sensor arrangement; acquire an impedance plethysmography signal from the second sensor arrangement; process an acquired impedance plethysmography signal to determine an extent of arterial blood flow occlusion, and process an acquired pressure signal to determine an oscillometric blood pressure measurement.

[0055] Determining the extent of arterial blood flow occlusion advantageously enables a check to be performed, before a determined oscillometric blood pressure measurement is displayed, that the arterial blood flow was properly occluded when the pressure signal was acquired. If the outcome of the check is that the arterial blood flow was not adequately occluded, a notification that the blood pressure measurement failed and that the blood pressure sensing device should be adjusted before restarting the measurement can be displayed. This checking function serves to prevent a false blood pressure reading being output.

[0056] Using textile electrodes advantageously enables an inflatable bladder to be used that has a length that is not restricted by a need to position the electrodes in a region of the wearing circumference of the blood pressure sensing device in which the inflatable bladder does not extend.

[0057] The non-invasive blood pressure sensing device preferably further comprises a third sensor arrangement that comprises a first and a second electrode arranged for being contacted by the fingers of the arm of the individual on which the non-invasive blood pressure sensing device is not being worn. The processor is operatively connected to the third sensor arrangement and configured to acquire, from electrical connection between the second and the third sensor arrangements, at least one of the following types of physiological signal: an impedance plethysmography signal, an electrocardiogram signal, a bioelectrical impedance signal.

[0058] The provision of the third sensor arrangement advantageously enables the blood pressure sensing device to determine other parameters / metrics.

[0059] Thus, when the strap of the blood pressure sensing device is fastened around the wrist of one arm of the individual, the processor is functional to acquire a signal from that arm, via the first and the second sensor arrangement, and when the individual is also touching the electrodes of the third sensor arrangement with the fingers of their other hand, the processor is functional to acquire a signal or signals from between the arms of the individual, via the second and the third sensor arrangement.

[0060] Preferably, the non-invasive blood pressure sensing device resembles a smartwatch.

[0061] There is disclosed herein a non-invasive blood pressure sensing device comprising a control unit that is secured to a strap that comprises an inflatable bladder, a first sensor arrangement arranged to sense a pressure within the inflatable bladder, and a second sensor arrangement comprising textile electrodes arranged to contact the skin of the wrist of the individual around which the strap is fastened. A pressure signal from the first sensor arrangement and an impedance plethysmography signal from the second sensor arrangement are acquired by a processor of the control unit and processed by the processor to determine an extent of arterial blood flow occlusion and an oscillometric blood pressure measurement, whereby to check that the arterial blood flow was properly occluded during the blood pressure measurement.

[0062] A blood pressure sensing device 101 according to a specific example will now be described. A perspective view of the blood pressure sensing device 101 is shown in Figure 1 and a side view is shown in Figure 2. The blood pressure sensing device 101 is a non-invasive blood pressure sensing device designed for an individual to wear on a wrist.

[0063] The blood pressure sensing device 101 comprises a control unit 102 secured to a strap 103, which is usable to secure the blood pressure sensing device 101 around a wrist. In Figure 3, the blood pressure sensing device 101 is shown being worn by individual 300 on the wrist 301 of their right arm 302. It is to be appreciated that the individual 300 may alternatively wear the blood pressure sensing device 101 on the wrist 303 of their left arm 304.

[0064] A schematic of the specific example of the blood pressure sensing device 101, which incorporates optional features as mentioned below, is shown in Figure 4.

[0065] The strap 103 comprises an inflatable bladder 104.

[0066] The control unit 102 comprises a processor 401, data storage 402, an input device 403, a display device 404 and an inflation control arrangement 405 that is operable to control inflation and deflation of the inflatable bladder 104. According to this specific example, the inflation control arrangement 405 comprising a pump 406, for supplying air to the inflatable bladder 104 to inflate the inflatable bladder 406, and a release valve 407, for allowing air to exit the inflatable bladder 104.

[0067] The blood pressure sensing device 101 comprises a first sensor arrangement 408 that comprises at least one pressure sensor arranged to sense a pressure within the inflatable bladder 104. In this specific example, the first sensor arrangement 408 is comprised by the inflation control arrangement 405 of the control unit 102.

[0068] The blood pressure sensing device 101 further comprises a second sensor arrangement 409 comprising at least first, second, third and fourth textile electrodes 105, 106, 107, 108 arranged to contact the skin of the individual 300, around whose wrist 301 the strap 103 is fastened.

[0069] As can be seen in Figure 2, the inflatable bladder 104 extends under the control unit 102. The control unit 102 may be secured to the strap 103 in any suitable way, using any suitable securing member or members.

[0070] As illustrated in Figure 2, the strap 103 has an inner side 201, an outer side 202, and a length direction, indicated by arrow 203. As shown, according to this specific example, the first to the fourth textile electrodes 105-108 are spaced apart in the length direction 203 of the strap 103.

[0071] According to this specific illustrated example, the first to the fourth textile electrodes 105-108 are each comprised by the strap 103 and exposed on the inner side 201 thereof. In this example, each textile electrode 105-108 of the second sensor arrangement 409 is embedded within a layer of material 204. In this example, the layer of material 204 is a layer of a breathable fabric material. This feature is beneficial for providing a comfortable wearing experience, as the strap 103 should be fitted on the individual 300 wearing the blood pressure sensing device 101 so that the textile electrodes 105-108 of the second sensor arrangement 409 are held in contact with the skin.

[0072] The use of textile electrodes is beneficial in respect of achieving a desired length of the inflatable bladder for applying a pressure to a wrist and for achieving a desired uniformity of the pressure applied to the wrist. More specifically, using flexible, textile electrodes advantageously allow the electrodes to be positioned within the footprint of the inflatable bladder, for example placed on the inflatable bladder. Being able to position the flexible, textile electrodes in the same region as the inflatable bladder avoids the requirement associated with rigid, metal electrodes for the electrodes to be positioned in a different region to the inflatable bladder, for example on a rigid surface of the control unit. As there is no need for the textile electrodes to be positioned in a region in which the inflatable bladder does not extend, the textile electrodes do not impose any limitation on the length of the inflatable bladder. This feature beneficially enables the length of the inflatable bladder and, in turn, the contact area between the inflatable bladder and the individual, to be increased.

[0073] According to the present example, the strap 103 comprises an adjustment arrangement, indicated at 205 for varying a wearing circumference of the blood pressure sensing device 101. This feature is beneficial for accommodating different wrist sizes.

[0074] According to this specific illustrated example, the strap 103 has a first end 206 and a second end 207, and the adjustment arrangement 205 comprises a prong buckle 208 and a plurality of apertures, such as apertures 209 and 210, defined in the strap 103. In the traditional manner of a belt or of a watch strap, the apertures are spaced apart in the length direction of the strap and the selection of one of the plurality of apertures to insert the prong of the prong buckle through is a selection of a particular wearing circumference. It is to be appreciated that the adjustment arrangement may have any suitable alternative form. It is to be understood also that in a different example, the strap may be configured as a closed loop instead of a broken loop having first and second ends.

[0075] As will be described in further detail hereinafter, the processor 401 is operatively connected to the first sensor arrangement and to the second sensor arrangement and is functional to acquire a pressure signal from the first sensor arrangement 408 and to acquire an impedance plethysmography (IPG) signal from the second sensor arrangement 409. The processor 401 is further functional to process an acquired impedance plethysmography signal to determine an extent of arterial blood flow occlusion, and to process an acquired pressure signal to determine an oscillometric blood pressure measurement.

[0076] In a specific example, the blood pressure sensing device 101 has the physical form of an electronic watch. Thus, the blood pressure sensing device 101 advantageously has a form factor that is familiar and convenient to use. In a preferred specific example, the blood pressure sensing device 101 incorporates the functionality of a smartwatch (or, in other words, is a smartwatch with the blood pressure sensing functionality disclosed herein). According to this specific example, the input device 403 and the display device 404 are comprised by a touchscreen 109. With reference to Figure 2, in this illustrated example, the inflation control arrangement 405 is positioned between the touchscreen 109 and the inflatable bladder 104.

[0077] To obtain an oscillometric blood pressure measurement, while the strap 103 of the blood pressure sensing device 101 is properly secured around the wrist 301 of an individual 300, the inflation control arrangement 405 is activated to inflate and then deflate the inflatable bladder 104 and a pressure signal is acquired from the at least one pressure sensor of the first sensing arrangement 408 during inflation and deflation of the inflatable bladder; the acquired pressure signal or signals is / are then processed by the processor 401 to determine systolic and diastolic blood pressure values for the individual 300.

[0078] It is important for the inflatable bladder to be an appropriate size for the individual (width and length compared to wearing circumference) so that a proper application of pressure is achieved to avoid falsely high or low readings being obtained (as the blood pressure measurement technique uses the hypothesis that the pressure inside the inflatable bladder is the pressure applied to the artery). While an appropriate size of inflatable bladder can be chosen for an individual's wrist prior to the blood pressure measurement being performed, it is possible for the arteries to be hidden behind bone so that pressure is not applied to the arteries, but this not being evident from the acquired pressure signal results in a false reading being obtained.

[0079] The blood pressure sensing device 101 of the present example is advantageously configured to detect whether the arterial blood flow has been properly occluded during the oscillometric blood pressure measurement.

[0080] Referring now to Figure 5, the textile electrodes 105-108 of the second sensing arrangement 409 are usable for impedance plethysmography (IPG) measurements. As illustrated, a current can be applied between two of the textile electrodes, in the shown arrangement between textile electrodes 105 and 108, and a voltage measured between a different two of the textile electrodes, in the shown arrangement between textile electrodes 106 and 107. The impedance plethysmography (IPG) measurement can be used to determine whether a proper application of pressure on the arteries has been achieved.

[0081] In a specific example, the impedance plethysmography (IPG) signal is measured as shown in Figure 5 (using the second sensing arrangement 409). If the impedance plethysmography (IPG) signal shows a clear decrease or disappearance of the signal amplitude, then this indicates that the arteries were properly occluded. This information can be used to classify a blood pressure measurement taken using the oscillometric signal as an adequate reading ("successful attempt") or as an inadequate reading ("failed attempt").

[0082] In an example, the processor 401 is functional to process an acquired impedance plethysmography signal to determine whether an acceptable extent of arterial blood flow occlusion is met.

[0083] An extent of a decrease of the signal amplitude in the impedance plethysmography (IPG) measurement can be predetermined as an indicator that the arteries were occluded to an acceptable extent for a blood pressure measurement not to be classified as an inadequate reading. In one example, a decrease of the signal amplitude in the impedance plethysmography (IPG) measurement to zero (disappearing signal) is used as the indicator of the arteries being occluded to an acceptable extent. In another example, a decrease of the signal amplitude in the impedance plethysmography (IPG) measurement by a predetermined percentage is used as the indicator that the arteries being occluded to an acceptable extent.

[0084] In an example, the processor 401 is functional to process an impedance plethysmography signal to determine whether an acceptable extent of arterial blood flow occlusion is met.

[0085] In an example, the processor 401 is functional to process an impedance plethysmography signal acquired contemporaneously with an acquired pressure signal to determine whether an acceptable extent of arterial blood flow occlusion is met. In an example, the processor 401 is functional to process an acquired pressure signal in combination with a determined extent of arterial blood flow occlusion to determine the oscillometric blood pressure measurement.

[0086] In a specific example, the processor 401 is functional to determine that an acceptable extent of arterial blood flow occlusion is met before processing an acquired pressure signal to determine the oscillometric blood pressure measurement.

[0087] In a specific example, if an impedance plethysmography (IPG) measurement taken at the start of the blood pressure measurement indicates that the arteries were properly occluded, then a blood pressure measurement using the oscillometric signal is output; however, if the impedance plethysmography (IPG) measurement alternatively indicates that the arteries were not properly occluded, a prompt for the individual to remove and replace the blood pressure sensing device 101 before taking the blood pressure measurement again is output.

[0088] In a specific example, the processor 401 is functional to process an acquired impedance plethysmography signal to determine heart rate. Thus, when the textile electrodes 105-108 of the second sensing arrangement 409 are not being used during a blood pressure measurement, they can be used to determine heart rate. Beneficially, a continuous heart rate reading can be determined using the textile electrodes 105-108 of the second sensing arrangement 409 instead of using, for example, a photoplethysmography (PPG) sensor.

[0089] The blood pressure sensing device 101 of the present example is advantageously configured to measure the wearing circumference of the blood pressure sensing device 101.

[0090] With reference to Figures 4 and 6 to 8, the blood pressure sensing device 101 comprises a wearing circumference measurement arrangement, indicated at 410, for determining a magnitude of the wearing circumference.

[0091] According to this specific illustrated example, the wearing circumference measurement arrangement 410 comprises a first and a second conductive line 601, 602 extending along the outer side 202 of the strap 103 and a conductive region, indicated at 701, of the prong buckle 208. The conductive region 701 of the prong buckle 208 is arranged for making electrical connection with the first and the second conductive lines 601, 602 when in use. As illustrated in Figure 8, the processor 401 is functional to acquire a resistance between the first and the second conductive lines 601, 602 when the conductive region 701 of the prong buckle 208 makes electrical connection therewith. The processor 401 is functional to process the acquired resistance to determine a magnitude of the wearing circumference. This information can be used to improve the blood pressure measurement. The determined magnitude of the wearing circumference represents an estimation of the wrist circumference of the individual, which parameter is useful to improve the blood pressure accuracy since the pressure effectively applied to the artery depends on the inflatable bladder length and width and the limb (wrist) circumference.

[0092] It is to be appreciated that the wearing circumference measurement arrangement may have any suitable alternative form, which may depend on the form of the strap and / or adjustment arrangement for varying the wearing circumference.

[0093] In an example, the processor 401 is functional to process an acquired pressure signal in combination with a determined magnitude of the wearing circumference to determine the oscillometric blood pressure measurement.

[0094] With reference now to Figure 9, in the present example, the processor 401 is functional to process an acquired signal from the first sensing arrangement 408 (pressure inside the inflatable bladder 104), the second sensing arrangement 409 (extent of extent of arterial blood flow occlusion) and the wearing circumference measurement arrangement 410 (magnitude of the wearing circumference).

[0095] According to the illustrated flow chart 901, an impedance plethysmography (IPG) measurement input is received at 902, a pressure measurement input is received at 903 and a wearing circumference measurement input is received at 904.

[0096] The impedance plethysmography (IPG) measurement received at 902 is taken at the same time as the pressure measurement received at 903. At 905 the amplitude of the impedance plethysmography (IPG) signal is analysed as a function of pressure in the inflatable bladder 104, and at 906 a question is asked as to whether pressure was properly applied to the arteries (whether an acceptance extent of arterial blood flow occlusion was met). If the answer to the question asked at 906 is answered in the negative, at 907 a classification is made that the blood pressure measurement attempt is inadequate ("failed attempt") and at 908 a notification is returned for the blood pressure sensing device 101 to be adjusted (for example, removed and replaced) for redoing the blood pressure measurement. If the answer to the question asked at 906 is answered in the affirmative, at step 910 a first blood pressure value is calculated from the pressure measurement received at 903 and at 911 any checking or improving of the blood pressure value is performed before a blood pressure reading is returned at 912.

[0097] With reference to Figures 1, 4 and 10, the blood pressure sensing device 101 of the present specific example comprises a third sensor arrangement 411 comprising a first and a second electrode 110, 111 arranged for being contacted by the fingers of the arm 304 of the individual 300 on which the blood pressure sensing device 101 is not being worn. In other words, if the individual is wearing the blood pressure sensing device 101 on their right wrist ("devicewearing arm"), the first and second electrodes 110, 111 of the third sensor arrangement 411 are contactable by the fingers of their left hand ("other arm"), and vice versa. According to the specific illustrated arrangement, the first and second electrodes 110, 111 are located on a side 112 of the touchscreen 109.

[0098] In an example, the processor 401 is operatively connected to the third sensor arrangement 411 and is configured to acquire from electrical connection between the second 409 and the third sensor arrangements 411 at least one of an impedance plethysmography (IPG) signal, an electrocardiogram (ECG) signal, a bioelectrical impedance (BIA) signal. Thus, the third sensor arrangement (in combination with the second sensor arrangement) is usable to acquire one or more types of physiological signal.

[0099] As described above, and as illustrated in Figure 5, the blood pressure sensing device 101 comprises an arrangement for obtaining an impedance plethysmography (IPG) signal from the wrist 301 of the arm 302 of the individual 300 on which the blood pressure sensing device 101 is being worn. As will now be described, and as illustrated in Figure 10, the blood pressure sensing device 101 of the present specific example comprises another arrangement for obtaining an impedance plethysmography (IPG) signal from between the arms 302, 304 of the individual 300 wearing the blood pressure sensing device 101. Figure 10 illustrates use of the second sensor arrangement 410 and the third sensor arrangement 411 to acquire, simultaneously, an impedance plethysmography (IPG) measurement from the device-wearing arm and from between the device-wearing arm and the other arm. As shown, a current can be applied between two of the textile electrodes of the second sensor arrangement 409 and a voltage measured between a different two of the textile electrodes, of the second sensor arrangement 409, as per the arrangement shown in Figure 5. At the same time, a current can be applied between one of the textile electrodes of the second sensor arrangement 409 and one of the first and second electrodes of the third sensor arrangement 411 and a voltage measured between a different one of the textile electrodes of the second sensor arrangement 409 and the other of the first and second electrodes of the third sensor arrangement 411.

[0100] Thus, an impedance plethysmography (IPG) measurement can be taken from the devicewearing arm using the second sensor arrangement, and an impedance plethysmography (IPG) measurement can be taken between the device-wearing arm and the other arm using the second and the third sensor arrangements.

[0101] Figure 11 illustrates use of the second sensor arrangement 409 and the third sensor arrangement 411 to acquire, simultaneously, from between the device-wearing arm and the other arm, an impedance plethysmography (IPG) measurement and an electrocardiogram (ECG) measurement.

[0102] As shown, electrocardiogram (ECG) signals can be obtained using two of the textile electrodes of the second sensor arrangement 409 and one of the electrodes of the third sensor arrangement 411. At the same time, an impedance plethysmography (IPG) measurement can be taken, as per the arrangement shown in Figure 5 or in Figure 10. It should be noted that while the electrocardiogram (ECG) signal is continuous, the impedance plethysmography (IPG) signal is alternative; and any suitable technique may be used to separate them.

[0103] In an example, the processor 401 is functional to process impedance plethysmography signals or, in combination, impedance plethysmography and electrocardiogram signals, to determine an evaluation of at least one of: pulse arrival time, pulse transit time. The at least one evaluation of pulse arrival time may comprise either or both of an evaluation of pulse arrival time from the wrist 301 of the individual 300 on which the blood pressure sensing device 101 is being worn and an evaluation of pulse arrival time from between the arms 302, 304 of the individual 300.

[0104] In an example, the processor 401 is functional to process at least one evaluation of pulse arrival time to determine at least one evaluation of pulse wave velocity.

[0105] The at least one evaluation of pulse a wave velocity may comprise either or both of an evaluation of pulse wave velocity at the wrist 301 of the individual 300 on which the blood pressure sensing device 101 is being worn, an evaluation of pulse wave velocity between the arms 302, 304 of the individual 300.

[0106] It has been found that a timing difference between the ECG signal and the between-the-arms IPG signal provides a hand-to-hand pulse arrival time (PAThand-to-hand) that is related to carotid pulse arrival time (PATcarotid) and that can be processed to determine a carotid pulse wave velocity (PWVcarotid). This parameter can be used to determine an evaluation of stiffening of the central arteries.

[0107] A timing difference between the ECG signal and the device-wearing arm IPG signal provides a wrist pulse arrival time (PAT wrist) that can be processed to determine a peripheral artery pulse wave velocity (PWVperipheai). This parameter can be used to determine an evaluation of stiffening of the peripheral arteries.

[0108] Thus, information both on central arterial stiffness and peripheral arterial stiffness can be obtained from the blood pressure sensing device 101.

[0109] Figure 12 illustrates use of the second sensor arrangement 409 and the third sensor arrangement 411 to acquire a bioelectrical impedance signal from between the arms 302, 304 of the individual 300. As shown, a bioimpedance measurement can be obtained using two of the textile electrodes of the second sensor arrangement 409 and both electrodes of the third sensor arrangement 411. In an example, the processor 401 is functional to process an acquired bioelectrical impedance signal to determine an evaluation of upper body composition.

[0110] Thus, information on fat, muscle and water content of the upper body can be obtained from the blood pressure sensing device 101.

[0111] Figures 13 & 14 show a blood pressure sensing device 1301 according to another specific example. The blood pressure sensing device 1301 is like blood pressure sensing device 101 but the second sensor arrangement 409 comprises additional textile electrodes, such as textile electrodes 1302 and 1303. The presence of additional textile electrodes increases the possible electrical configuration options using the textile electrodes of the second sensor arrangement 409 from which to obtain an impedance plethysmography (IPG) signal (see Figures 5, 8 and 10 and related description). In turn, this enables impedance plethysmography (IPG) signal to be obtained using different combinations of the textile electrodes of the second sensor arrangement 409 and then for a selection of one of the acquired impedance plethysmography (IPG) signal for using in a particular evaluation or for multiple of the acquired impedance plethysmography (IPG) signal to be combined / processed for using in a particular evaluation.

[0112] Referring now to Figures 4 & 15, the control unit 102 may run an application, a screen 1501 of which is shown in Figure 15 displayed on touchscreen 109. In this illustrated example, screen 1501 is a user profile screen.

[0113] In the specific illustrated example, the user profile screen 1501 shows the following user profile value fields: height 1502, weight 1503, age 1504, gender 1505. In an example, an individual can input and adjust user profile values within these user profile value fields using the touchscreen 109. User profile values may however be provided to the application, and to the control unit 102, in any other suitable way.

[0114] According to the present example, the control unit 102 comprises a wireless communication interface 412, by means of which the control device 102 is enabled for wireless communication with a remote device 1506. The remote device 1506 may be a mobile device, such as a smartphone, or, for example, a personal computer. In an example, the control device 102 is enabled for two-way communication with the remote device 1506. In a specific example, wireless communication between the control unit 102 and the remote device 1506 is by a personal area network protocol, such as Bluetooth TM. It is to be appreciated that the control device 102 may alternatively or additionally be configured for wired communication with the remote device 1506.

[0115] In an example, the control unit 102 comprising the touchscreen 109 is capable of gesture recognition. In a specific example, the control unit 102 is configured to initiate blood pressure sensing, or a different sensing routine, in response to detecting the performance of a particular gesture, such as a swipe, on the touchscreen 109.

[0116] In an example, the processor 401 is functional to process at least one acquired physiological signal in combination with at least one user profile value input to the evaluation unit 102, the at least one user profile value selected from, age, height, weight, gender.

[0117] In an example, the processor 401 is functional to process an acquired bioelectrical impedance signal in combination with at least one user profile value to determine the evaluation of upper body composition, in which the at least one user profile value selected from: age; height; weight; gender.

[0118] It is to be appreciated that one or more user profile values may be used by the processor 401 in a particular evaluation, which may be a determination of a parameter or of a risk.

[0119] The number and type of user profile values forming a user profile may vary between examples.

[0120] Figure 16 illustrates features of an example method 1601 of evaluating cardiovascular risk using the blood pressure sensing device 101 (or 1301).

[0121] The example method 1601 utilises user profile values 1602 and measured signals 1603, and returns a result 1604. The shown user profile values 1602 are the biometric parameters of age 1504, gender 1505 and height 1502. The shown measured signals 1603 are oscillometric blood pressure 1605, ECG 1606 and IPGarm-arm 1607. As indicated at 1608, an assessment is made as to whether the oscillometric blood pressure measurement is greater than 135 / 85 (under the current ESC (European Society of Cardiology) / ESH (European Society of Hypertension) guidelines for home blood pressure monitoring, an average value of >135 / 85 mmHg is defined as hypertension). A determination that the oscillometric blood pressure measurement is greater than this predetermined value indicates an increased cardiovascular risk, which is recorded at 1609.

[0122] As indicated at 1610, a determination is made as to whether the ECG signal 1606 indicates arrythmia. If the outcome is positive, this indicates an increased cardiovascular risk, which is recorded at 1609.

[0123] As indicated at 1611, heart rate 1612 is evaluated with reference to a predetermined value, indicating that the heart rate is deemed high. If the outcome is that the heart rate is high, this indicates an increased cardiovascular risk, which is recorded at 1609.

[0124] As indicated at 1613, an assessment is made as to whether pulse wave velocity is too high for the individual. If the outcome is that the pulse wave velocity is too high, this indicates an increased cardiovascular risk, which is recorded at 1609.

[0125] If any of the parameters checked indicate an increased cardiovascular risk, an indication to this effect is output at 1604.

[0126] It is to be appreciated that a physiological signal or signals may be acquired and processed by the blood pressure sensing device in ways not specifically described and / or illustrated. It is to be understood that the singular term "signal" may be interpreted to encompass the plural term "signals" and vice versa as appropriate in the context that the singular or the plural version of the term is used. As appropriate in the context, reference to a signal being acquired should be understood to encompass sampling of a signal and reference to a signal being processed should be understood to encompass processing of data obtained from the sampling the signal. Further, by the term "functional to" it is meant comprising suitable hardware and / or software configured to enable the stated associated functionality to be carried out. Although illustrative embodiments and examples of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment and examples shown and / or described and that various changes and modifications can be affected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A non-invasive blood pressure sensing device (101), comprising: a control unit (102) secured to a strap (103), the strap (103) configured to be fastened around a wrist (301) of an individual (300) and comprising an inflatable bladder (104), and the control unit (102) comprising a processor (401), data storage (402), an input device (403), a display device (404), and an inflation control arrangement (405) operable to control inflation and deflation of the inflatable bladder (104); a first sensor arrangement (408) comprising at least one pressure sensor arranged to sense a pressure within the inflatable bladder (104); and a second sensor arrangement (409) comprising at least first, second, third and fourth textile electrodes (105, 106, 107, 108) arranged to contact the skin of the wrist (301) of the individual (300) around which the strap (103) is fastened; the processor (401) operatively connected to the first sensor arrangement (408) and to the second sensor arrangement (409) and functional to: acquire a pressure signal from the first sensor arrangement (408); acquire an impedance plethysmography signal from the second sensor arrangement (409); process an acquired impedance plethysmography signal to determine an extent of arterial blood flow occlusion, and process an acquired pressure signal to determine an oscillometric blood pressure measurement.

2. The non-invasive blood pressure sensing device of claim 1, wherein the processor (401) is functional to process an impedance plethysmography signal to determine whether an acceptable extent of arterial blood flow occlusion is met.

3. The non-invasive blood pressure sensing device of claim 2, wherein the processor (401) is functional to process an impedance plethysmography signal acquired contemporaneously with an acquired pressure signal to determine whether an acceptable extent of arterial blood flow occlusion is met.

4. The non-invasive blood pressure sensing device of claim 2 or claim 3, wherein the processor (401) is functional to determine that an acceptable extent of arterial blood flow occlusion is met before processing an acquired pressure signal to determine the oscillometric blood pressure measurement.

5. The non-invasive blood pressure sensing device (101) of any one of the preceding claims, wherein the processor (401) is functional to process an acquired impedance plethysmography signal to determine heart rate.

6. The non-invasive blood pressure sensing device (101) of any one of the preceding claims, further comprising a third sensor arrangement (411) comprising a first and a second electrode (110, 111) arranged for being contacted by the fingers of the arm of the individual (300) on which the non-invasive blood pressure sensing device (101) is not being worn, the processor (401) operatively connected to the third sensor arrangement (411) and configured to acquire from electrical connection between the second and the third sensor arrangements (409, 411), at least one of: an impedance plethysmography signal, an electrocardiogram signal, a bioelectrical impedance signal.

7. The non-invasive blood pressure sensing device (101) of claim 6, wherein the processor (401) is functional to process impedance plethysmography signals or, in combination, impedance plethysmography and electrocardiogram signals, to determine an evaluation of at least one of: pulse arrival time, pulse transit time.

8. The non-invasive blood pressure sensing device (101) of claim 7, wherein the at least one evaluation of pulse arrival time comprises one or both of: an evaluation of pulse arrival time from the wrist (301) of the individual (300) on which the blood pressure sensing device (101) is being worn, an evaluation of pulse arrival time from between the arms (302, 304) of the individual (300).

9. The non-invasive blood pressure sensing device (101) of claim 8, wherein the processor (401) is functional to process at least one evaluation of pulse arrival time to determine at least one evaluation of pulse wave velocity.

10. The non-invasive blood pressure sensing device (101) of claim 8, wherein the at least one evaluation of pulse a wave velocity comprises one or both of: an evaluation of pulse wave velocity at the wrist (301) of the individual (300) on which the non-invasive blood pressure sensing device (101) is being worn, an evaluation of pulse wave velocity between the arms (302, 304) of the individual (300).

11. The non-invasive blood pressure sensing device of (101) of any one of claims 6 to 10, wherein the processor (401) is functional to process an acquired bioelectrical impedance signal to determine an evaluation of upper body composition.

12. The non-invasive blood pressure sensing device of (101) of claim 11, wherein the processor (401) is functional to process an acquired bioelectrical impedance signal in combination with at least one user profile value to determine the evaluation of upper body composition, in which the at least one user profile value selected from: age; height; weight; gender.

13. The non-invasive blood pressure sensing device (101) of any one of the preceding claims, wherein the strap comprises an adjustment arrangement (205) for varying a wearing circumference of the non-invasive blood pressure sensing device (101).

14. The non-invasive blood pressure sensing device (101) of claim 13, comprising a wearing circumference measuring arrangement (410) for determining a magnitude of the wearing circumference.

15. The non-invasive blood pressure sensing device of claim 14, wherein the processor (401) is functional to process an acquired pressure signal in combination with a determined magnitude of the wearing circumference to determine the oscillometric blood pressure measurement.

16. The non-invasive blood pressure sensing device (101) of claim 13, the adjustment arrangement (205) comprising a prong buckle (208) and a plurality of apertures (209, 210) defined in the strap (103).

17. The non-invasive blood pressure sensing device (101) of claim 14, comprising a wearing circumference measuring arrangement ( 10) for determining a magnitude of the wearing circumference, the wearing circumference measuring arrangement (410) comprising: a first and a second conductive line (601, 602) extending along an outer side (202) of the strap (103) and a conductive region (701) of the prong buckle (208), the conductive region (701) of the prong buckle (208) arranged for making electrical connection with the first and the second conductive lines (601, 602), and the processor (401) functional to acquire a resistance between the first and the second conductive lines (601, 602) when the conductive region (701) of the prong buckle (208) makes electrical connection therewith and to process the acquired resistance to determine a magnitude of the wearing circumference.

18. The non-invasive blood pressure sensing device (101) of any one of the preceding claims, wherein each textile electrode (105-108) of the second sensor arrangement (409) is embedded within a layer of material (204) and exposed on an inner side (201) of the strap (103).

19. The non-invasive blood pressure sensing device (101) of claim 16, wherein said layer of material (204) is a layer of a breathable fabric material.

20. The non-invasive blood pressure sensing device (101) of any one of the preceding claims, wherein the input device (403) and the display device (404) are comprised by a touchscreen (109).

21. The non-invasive blood pressure sensing device (101) of any one of the preceding claims, wherein the control unit (102) comprises a wireless communication interface (412).

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