Blood pressure monitor and control procedure for the same

Abstract

A blood pressure monitor configured to be used while attached to the wrist of a subject, wherein the blood pressure monitor features: a tilt angle measuring unit which is configured, to measure an angle of inclination, which is an angle formed by the forearm of the person being measured with respect to a reference plane; a rotation angle measuring unit configured to measure a rotation angle of the blood pressure monitor around an axis, using a forearm as the axis; a distance information acquisition unit configured to acquire distance information regarding the distance between the ulnar artery and the radial artery that run through the wrist; a determination unit configured to determine a relative positional relationship between the radial artery and the ulnar artery, using the inclination angle, rotation angle, and distance information; and a control unit which is configured to perform the control according to the relative position relationship.

Description

Technical area

[0001] The present invention relates to a wrist-type blood pressure monitor configured to be used while attached to the wrist, and a control method for the same. Background of the state of the art

[0002] To accurately measure blood pressure with a wrist-type blood pressure monitor, the measurement must be started when the height of the wrist, where the cuff is attached, and the height of the heart are approximately the same. For this reason, various methods for aligning the wrist and heart heights have been proposed in the past (e.g., see patent documents 1 to 4).

[0003] Patent document 1 discloses a blood pressure measuring device in which, provided that a user performs the attachment of a blood pressure measuring device to his or her wrist while his or her forearm is on a table and then raises the height of the wrist by raising the forearm from the elbow, the distance between the wrist and the heart of the user is measured by a sensor and the height of the wrist is determined based on the distance.

[0004] Patent document 2 discloses a blood pressure measuring device which uses the forearm roll angle and inclination angle to determine the height of the measuring point.

[0005] Patent document 3 discloses a blood pressure measuring device which, by starting the blood pressure measurement while the measuring point is in contact with the chest, allows the blood pressure measurement to be carried out in a state in which the heights of the measuring point and the heart coincide.

[0006] Patent document 4 discloses a blood pressure measuring device which determines the suitability of the blood pressure measurement based on the orientation of a user, which is detected by a biaxial accelerometer, and reports the determination result.

[0007] Patent document 5 discloses an electronic blood pressure measuring device with a function for determining the posture of a person.

[0008] Patent document 6 discloses a device and method for measuring blood pressure that can guide a person being examined to a correct blood pressure measurement posture. List of citations from patent literature Patent Document 1: JP 2001-178694 A Patent document 2: WP 2002 / 39893 A Patent Document 3: JP 2010-51364 A Patent Document 4: JP 2003-102693 A Patent document 5: DE 601 18 236 T2 Patent document 6: US 2010 / 0 049 059 A1 Summary of the invention: Technical problem

[0009] Two arteries run through the wrist: the ulnar artery, located along the ulna on the little finger side, and the radial artery, located along the radius on the thumb side. Therefore, when the pressure applied by a cuff is transmitted evenly and without loss to both the ulnar and radial arteries, a blood pressure reading is determined using an oscillometric method. This method utilizes a waveform generated by combining the pulse waves produced in the radial and ulnar arteries.

[0010] As long as the respective heights of the radial and ulnar arteries are the same as the height of the heart, the blood pressure reading determined using the compound wave will be accurate. However, if the height of the radial or ulnar artery differs from the height of the heart, the blood pressure reading determined using the compound wave will contain an error.

[0011] Patent documents 1 to 4 do not take into account the heights of the radial artery and the ulnar artery.

[0012] The present invention was carried out in view of the foregoing circumstances, and it is an object thereof to provide a wrist-type blood pressure measuring device and a control method for the same, according to which the blood pressure measurement accuracy can be increased. Solution to the problem

[0013] The blood pressure monitor according to the present invention is a blood pressure monitor configured to be used while attached to the wrist of a subject, comprising: an inclination angle measuring unit configured to measure an inclination angle formed by the subject's forearm with respect to a reference plane; a rotation angle measuring unit configured to measure a rotation angle about an axis of the blood pressure monitor using the forearm as an axis; and a distance information acquisition unit configured to acquire distance information regarding the distance between the ulnar artery and the radial artery running through the wrist.a determination unit configured to determine a relative positional relationship between the radial artery and the ulnar artery, using the inclination angle, rotation angle, and distance information; and a control unit configured to perform the control according to the relative positional relationship.

[0014] The control method for the blood pressure monitor according to the present invention is a control method for a blood pressure monitor configured to be used while attached to the wrist of a test subject, comprising: an inclination angle measurement step of measuring an inclination angle, which is an angle formed by a forearm of the test subject with respect to a reference plane; a rotation angle measurement step of measuring a rotation angle about an axis of the blood pressure monitor, wherein the forearm is used as the axis; a distance information acquisition step of acquiring distance information regarding the distance between the radial artery and the ulnar artery that pass through the wrist;a determination step of determining a relative positional relationship between the radial artery and the ulnar artery, using the angle of inclination, the angle of rotation, and the distance information; and a control step of performing a control action corresponding to the relative positional relationship. Advantageous effects of the invention

[0015] According to the present invention, it is possible to provide a wrist-type blood pressure measuring device and a control method for the same, according to which the blood pressure measurement accuracy can be increased. Brief description of the drawings Fig. Figure 1 is a drawing of the external appearance, showing an overall configuration of a wrist-type blood pressure monitor 1 to describe an embodiment of the present invention. Fig. Figure 2 is a diagram showing an internal configuration of the blood pressure monitor 1, which is located in Fig. 1 is shown. Fig. Figure 3 is a drawing showing an exemplary mode of use of the blood pressure monitor 1, which is located in Fig. 1 is shown. Fig. 4 is a view of the Fig. 3, from the head area of ​​a measuring person 40. Fig. Figure 5 is a drawing showing a cross-section of a person's wrist. Fig. 6 is a functional block diagram of a CPU 20, which is in Fig. 2 is shown. Fig. Figure 7 is a flowchart to describe the operation of the blood pressure monitor 1, which is located in Fig. 1 is shown. Fig. Figure 8 is a diagram showing a modified example of the function blocks in the CPU 20, which are in Fig. 6 is shown. Fig. Figure 9 is a diagram showing an example of a pulse wave amplitude envelope. Fig. 10 is a partially enlarged view of the Fig. 9. Fig. Figure 11 is a flowchart to describe a modified example of the operation of the blood pressure monitor 1. Description of the embodiments

[0016] An embodiment of the present invention is described below with reference to the drawings.

[0017] Fig. Figure 1 is a drawing of an external appearance of an overall configuration of a wrist-type blood pressure monitor 1 to describe an embodiment of the present invention.

[0018] The blood pressure monitor 1 includes: a main unit section 10 and a cuff 30, which can be wrapped around the wrist of a person being measured. The main unit section 10 is attached to the cuff 30. The cuff 30 contains an air bulb 31 (see Fig. 2), and an air hose 40 is connected to the air bellows 31.

[0019] A display unit 19, which is formed from a liquid crystal and the like, for example, and an operating unit 21 for receiving instructions from a user (the person performing the measurement), are arranged on the surface of the main device sub-area 10. The operating unit 21 includes many switches.

[0020] In this specification, "cuff" refers to a belt-shaped or tubular structure which has an inner cavity and which can be wrapped around a measuring point of a body part (wrist), and it indicates an object which is used to measure blood pressure by applying pressure to an artery of a subject, with the insertion of a fluid, such as air or a liquid, into the inner cavity.

[0021] An accelerometer 17, described later, is formed in the main device sub-area 10. The accelerometer 17 is a tri-axis gravitational accelerometer which detects weight or gravitational acceleration in three directions, namely an x-axis direction, a y-axis direction, and a z-axis direction, as described in Fig. Figure 1 is shown. Note that the display surface of display unit 19 is parallel to the xy-plane.

[0022] Fig. Figure 2 is a diagram showing an internal configuration of the blood pressure monitor 1, which is located in Fig. 1 is shown.

[0023] The main device sub-section 10 includes a pressure sensor 11, a pump 12 and an outlet valve (hereinafter referred to simply as "valve") 13, which are connected to the air hose 14, an oscillation circuit 14, a pump driver circuit 15, a valve driver circuit 16, an accelerometer 17, an artery detection unit 18, the display unit 19, a control unit (CPU) 20, which performs overall control of the main device sub-section 10 and executes various types of calculation processes, the operating unit 21, a memory 22 and a power supply unit 23, which supplies power to the units of the main device sub-section 10.

[0024] The pump 12 supplies air to the air bellows 31 to increase the pressure with which the cuff 30 builds up pressure at the measuring point (hereinafter also referred to as "cuff pressure").

[0025] Valve 13 is opened and closed to release air from or trap air in the air bellows 31.

[0026] The pump driver circuit 15 controls the driving of the pump 12, based on a control signal received from the CPU 20.

[0027] The valve driver circuit 16 controls the opening and closing of the valve 13 based on a control signal received from the CPU 20.

[0028] The pressure sensor 11 is a sensor that converts the air pressure in the air bellows 31 of the cuff 30 into an electrical signal (cuff pressure signal). An electrostatic capacitance pressure sensor, for example, is used as the pressure sensor 11. With an electrostatic capacitance pressure sensor, a capacitance value changes in accordance with a detected electrical signal.

[0029] The oscillation circuit 14 oscillates based on the capacitance value of the pressure sensor 11 and outputs a signal corresponding to the capacitance value of the CPU 20. The CPU 20 detects the pressure in the cuff 30 by sensing the cuff pressure signal output by the oscillation circuit 14.

[0030] The memory 22 includes a read-only memory (ROM) which stores programs, data, and so on to instruct the CPU 20 to perform predefined operations, an access memory (RAM) which is used as a working area, and a flash memory which holds the measured blood pressure data and similar information.

[0031] When the blood pressure monitor 1 is attached to the wrist of the person being measured, the artery detection unit 18 detects the positions of the radial artery and the ulnar artery, which are located in the wrist.

[0032] The artery detection unit 18 consists of a light-emitting element (e.g., an LED) that emits light (e.g., infrared) and a photoelectric converter element that receives light emitted by the light-emitting element and reflected from the wrist, and converts this light into an electrical signal. It is sufficient that the light emitted by the light-emitting element has a wavelength capable of penetrating the interior of the body part.

[0033] By arranging pairs, each consisting of a light-emitting element and a photoelectric transducer element, in a one-dimensional or two-dimensional form, it is possible to image the radial artery and the ulnar artery located in the wrist and to detect their positions.

[0034] The blood pressure monitor 1 can measure an inclination angle θ1, which is an angle formed by the forearm of the person being measured with respect to a reference plane, and a rotation angle θ2 of the blood pressure monitor 1 about an axis, where the forearm of the person being measured is used as the axis, according to the information detected by the accelerometer 17. The inclination angle θ1 and the rotation angle θ2 are described in detail below.

[0035] Fig. Figure 3 is a drawing which shows an example of a usage state of the blood pressure monitor 1. Fig. 4 is a drawing which shows a case in which the state of use, which is in Fig. Figure 3 is shown, viewed from above the head of a person measuring 40. In the Fig. 3 and Fig. 4. The xy-plane is a plane parallel to the ground, and the z-axis direction is the direction of gravity.

[0036] As in Fig. Figure 3 shows that the blood pressure monitor 1 is used in a state in which the person being measured is sitting in a chair CH and has placed his or her elbow E on a table T.

[0037] In Fig. 3 the reference letter S indicates the shoulder of the person being measured 40, the reference letter F indicates the upper arm of the person being measured 40, and the reference letter F indicates the forearm of the person being measured 40.

[0038] As in Fig. As shown in Figure 4, the blood pressure monitor 1 is used while attached to the wrist of the person being measured, so that the display surface of the display unit 19, which is provided on the main device sub-area 10, is parallel to the palm of the person being measured 40.

[0039] Because the person being measured 40 attaches the blood pressure monitor 1 to his or her wrist, the use of the blood pressure monitor 1 is also started in an orientation in which the elbow and wrist are on the table T (hereinafter referred to as the "assumed orientation").

[0040] As in Fig. As shown in Figure 3, the angle formed by the forearm F with respect to the upper surface of the table T, which is the reference plane, is the angle of inclination θ1. It is sufficient that the reference plane is a plane parallel to the xy-plane and below the elbow E, and for example, it can be the floor.

[0041] Fig. Figure 5 is a drawing showing a cross-section in a direction orthogonal to the direction in which the forearm of the wrist 50, to which the blood pressure monitor 1 is attached, extends. Reference digit 51 indicates the radial artery, and reference digit 52 indicates the ulnar artery.

[0042] In Fig. Figure 5 shows the section indicated by the dashed line as the position of the wrist 50 in the assumed orientation. A state in which the wrist 50 has been rotated about an axis, using the forearm as the axis, is indicated by the solid line from the assumed orientation, and the rotation angle θ2 can be measured at the same time based on the gravitational acceleration in the x-axis direction of the accelerometer 17.

[0043] It can also be in Fig. 5. A distance d between the radial artery and the ulnar artery can be obtained based on the image formed by the artery detection unit 18.

[0044] The difference in height from the reference plane of the radial artery and the ulnar artery in Fig. 5 is dsinθ2. Since the difference in heights also changes due to the inclination angle θ1, the difference in heights from the reference plane of the radial artery and the ulnar artery is also obtained by calculating dsinθ2×cosθ1.

[0045] Fig. 6 is a drawing showing functional blocks implemented by the CPU 20, which are in Fig. Figure 2 shows a program that is read from the ROM and executed.

[0046] The CPU 20 includes a blood pressure measurement unit 20a, an interartery distance information generation unit 20b, an artery relative position determination unit 20c, a wrist height detection unit 20d, a measurement alignment guidance unit 20e and an angle measurement unit 20h.

[0047] These functions are mainly implemented in the CPU 20 by the CPU 20, which reads programs stored in memory 22 and executes them; however, some or all of these functions can be implemented by using a hardware configuration.

[0048] The blood pressure measuring unit 20a extracts the pulse wave and cuff pressure from the cuff pressure signal input by the oscillation circuit 14. The blood pressure measuring unit 20a calculates the amplitude of the extracted pulse wave and generates pulse wave amplitude envelope data, which corresponds to the pulse wave amplitude and cuff pressure at the time of pulse wave generation. The blood pressure measuring unit 20a uses the pulse wave amplitude envelope data to determine the measured blood pressure values, namely the systolic blood pressure and the diastolic blood pressure.

[0049] The interartery distance information generation unit 20b uses the imaging signal output by the artery detection unit 18 to generate distance information regarding the distance (d in Fig. 5) to create between the radial artery and the ulnar artery, which are placed in the wrist of the person being measured.

[0050] The angle measuring unit 20h calculates the tilt angle θ1 and the rotation angle θ2 based on the output signal of the accelerometer 17.

[0051] The artery-relative position determination unit 20c uses the inclination angle θ1 and the rotation angle θ2, which are generated by the angle measurement unit 20h, and the distance information d, which is generated by the interartery distance information generation unit 20b, to determine the relative position relationship between the radial artery and the ulnar artery, which are placed in the wrist of the person being measured.

[0052] The relative position relationship determines the artery-relative-position determination unit 20c, which is placed at a higher position relative to the reference plane by the radial artery and the ulnar artery (a magnitude relationship between the heights of the radial artery and the ulnar artery), and determines how different the heights are in the case where one is higher than the other.

[0053] The artery-relative position determination unit 20c calculates the difference between the heights from the reference plane of the radial artery and the ulnar artery, which is ΔH, using equation (1) below, and determines the relative position ratio based on ΔH.

[0054] Note that in Fig. 5. The rotation angle θ2 has a negative sign when the wrist rotates to the left from the assumed orientation, and a positive sign when the wrist rotates to the right from the assumed orientation. Therefore, it is possible to determine, based on the sign of ΔH, which of the radial and ulnar arteries is in a higher position. ΔH=d×sinθ2×cosθ1

[0055] The wrist height detection unit 20d uses the inclination angle θ1, which is calculated by the angle measurement unit 20h, and various types of information relating to the subject, which are previously stored in the memory, to determine the height, relative to the heart, of the subject's wrist (height difference ΔD between the blood pressure monitor 1 and the subject's heart 40, which is in Fig. 3 is shown) to calculate.

[0056] Note that the wrist height detection unit 20d ΔD calculates on the assumption that the height from the reference plane of the blood pressure monitor 1 is the same as the height from the reference plane of the radial artery in the wrist to which the blood pressure monitor 1 is attached, or the same as the height from the reference plane of the ulnar artery in the wrist to which the blood pressure monitor 1 is attached.

[0057] The information previously stored in memory 22 is the upper arm length L1, the forearm length L2, the distance Ha from a shoulder S of the person being measured 30 to the seat surface of a chair CH, the seat surface height Hb of the chair CH, and the height Hc of the table T. L1, L2, and Ha can be values ​​that are automatically determined based on the height of the person being measured 40. Alternatively, it is sufficient to use a configuration in which Hb and Hc can be entered manually by the person being measured.

[0058] In Fig. 3, where the angle formed by the upper arm U of the measuring subject 40 and the direction of gravity is assumed to be θ3 and the distance from the shoulder S to the heart H is assumed to be H3, ΔD is obtained by using equation (2) below. ΔD=L2sinθ1−{L1cosθ3−(H3cosθ4)}

[0059] Here, the distance H3 can be substituted by a value that is approximately half the length L1 of the upper arm U. Also, based on the equation L1cosθ3=Hacosθ4-(Hc-Hb), cosθ4 is obtained by using equation (3) below. cosθ4={L1cosθ3+(Hc−Hb)} / Ha

[0060] Since the angle θ3 is a value already known from the experiment, it is also previously stored in memory 22. Accordingly, the wrist height detection unit 20d can calculate the height of the subject's wrist relative to the heart using an equation obtained by substituting equation (3) into equation (2), the angle of inclination θ1, and the information stored in memory 22.

[0061] Note that the method for calculating the height of the wrist is not limited to the above description, and a well-known method, such as that disclosed in patent document 1, 2 or similar, may be used.

[0062] The measurement alignment guidance unit 20e outputs information to guide the tilt angle θ1 so that ΔD, calculated by the wrist height detection unit 20d, is less than or equal to a permissible value. The permissible value is a value corresponding to which the required blood pressure measurement accuracy is maintained.

[0063] For example, by displaying a message such as “Please tilt your forearm slightly forward” or “Please tilt your forearm slightly backward” on the display unit 19, the measurement alignment guidance unit 20e guides the person being measured so that ΔD becomes less than or equal to the permissible value.

[0064] The measurement alignment control unit 20e also provides information to guide the rotation angle θ2 so that ΔH (absolute value without a sign), calculated by the artery-relative position determination unit 20c, is less than or equal to a permissible value. This permissible value is also the value corresponding to which the required blood pressure measurement accuracy is obtained.

[0065] For example, by displaying messages such as “Please turn your wrist slightly to the right” and “Please turn your wrist slightly to the left” on the display unit 19, the measurement alignment guidance unit 20e guides the person being measured so that ΔH (absolute value without a sign) becomes less than or equal to the permissible value.

[0066] Next, the operations of the blood pressure monitor 1 with the configuration described above will be described.

[0067] Fig. Figure 7 is a flowchart to describe the operation of the blood pressure monitor 1.

[0068] When the start of the blood pressure measurement is instructed by operating the control unit 21, the CPU 20 measures the tilt angle θ1 of the forearm based on the information detected by the accelerometer 17 (step S1), and measures the rotation angle θ2 based on the information detected by the accelerometer 17 (step S2).

[0069] The CPU 20 also uses the inclination angle θ1, which is measured in step S1, and the information regarding the upper arm length L1, the forearm length L2, the angle θ3, the distance Ha from the shoulder S of the measuring person 40 to the seat surface of the chair CH, the seat surface height Hb of the chair CH and the height Hb of the table T, to calculate ΔD according to equations (2) and (3) (step S3).

[0070] Next, the CPU 20 calculates the distance d between the radial artery and the ulnar artery based on the image formed by the artery detection unit 18 (step S4).

[0071] Then the CPU 20 uses the tilt angle θ1, which is measured in step S1, the rotation angle θ2, which is measured in step S2, and the distance d, which is calculated in step S4, to calculate ΔH according to the calculation of equation (1) (step S5).

[0072] Based on ΔD, which is calculated in step S3, and ΔH, which is calculated in step S5, the CPU 20 determines whether the orientation of the person being measured is one in which blood pressure measurement is possible (step S6).

[0073] If ΔD is less than or equal to the permissible value and ΔH is less than or equal to the permissible value, the CPU 20 determines that this is an orientation in which blood pressure measurement is possible. If either ΔD or ΔH exceeds the permissible value, the CPU 20 determines that this is an orientation in which blood pressure measurement is not possible.

[0074] If the result of the determination in step S6 is NO, the CPU 20 calculates the tilt angle θ1 and the rotation angle θ2, according to which ΔD and ΔH both become less than or equal to the permissible value, and causes the display unit 19 to display information regarding the guidance of the measuring person, so that the tilt angle θ1 and the rotation angle θ2 become the calculated angles (step S7). Then the CPU 20 returns to the processing of step S1.

[0075] Note that in step S7, guiding is not limited to being performed using the message display, and it is possible to guide the alignment using audio.

[0076] If the result of the determination in step S6 is YES, the CPU 20 starts inflating the cuff 30 and starts the blood pressure measurement using an oscillometric method (step S8).

[0077] Based on the determination of the measured blood pressure value, using the pulse wave amplitude envelope data, the CPU 20 causes the display unit 19 to display the determined blood pressure value (step S9) and terminates operation according to the blood pressure measurement instruction.

[0078] As described above, with blood pressure monitor 1, it is possible to start the blood pressure measurement in a state where the difference between the heights of the radial and ulnar arteries from the reference plane, i.e., ΔH, is less than or equal to the permissible value. Therefore, it is possible to obtain a blood pressure reading with a small error, thus increasing the reliability of the measured blood pressure value.

[0079] Note that, as long as it is assumed that the measurement is taken in a state where the height of the wrist and the height of the heart are the same, the processing of step S3 in Fig. Number 7 can be omitted.

[0080] In this case, in step S6 in Fig. 7 determines whether the height difference ΔH between the two arteries is less than or equal to the permissible value, and if ΔH exceeds the permissible value in step S7, it is sufficient to perform an alignment guide so that ΔH becomes less than or equal to the permissible value.

[0081] Although the artery detection unit 18 is provided in the blood pressure monitor 1, it can also be omitted.

[0082] If the artery detection unit 18 is omitted, it is sufficient that the distance information regarding the distance between the radial artery and the ulnar artery is previously stored in memory 22 and the CPU 20 performs step S4 instead of Fig. 7 the distance information from memory 22 is recorded.

[0083] The distance information regarding the distance between the radial artery and the ulnar artery can be stored in memory 22 by manual entry by the person being measured, and the manufacturer of the blood pressure measuring device 1 can store the average value of the distance between the radial artery and the ulnar artery in memory 22.

[0084] Although a description has been given in which the blood pressure measuring unit 20a measures blood pressure using an oscillometric method, it can measure blood pressure by using a different method, such as a method of measuring blood pressure by detecting a Korotkoff sound.

[0085] An example was described above in which the blood pressure measurement was carried out after guiding the alignment of the subject, so that the height difference ΔD between the wrist and the heart and the height difference ΔH between the radial artery and the ulnar artery are less than or equal to the permissible value.

[0086] The following is an example in which blood pressure measurement is possible even in a state where ΔH exceeds the permissible value, and the accuracy of the blood pressure measurement is increased by correcting the blood pressure measurement result.

[0087] Fig. Figure 8 is a diagram showing a modified example of the function blocks in the CPU 20, which are in Fig. 6 is shown.

[0088] Besides the fact that a measuring alignment guide unit 20e' is provided instead of the measuring alignment guide unit 20e and a blood pressure correction unit 20f has been added, the CPU 20, which is in Fig. As shown in 8, the same configuration as in Fig. 6.

[0089] The measurement alignment guidance unit 20e' provides information to guide the alignment of the person being measured so that the height difference ΔD between the wrist and the heart, calculated by the wrist height detection unit 20d, is less than or equal to the permissible value.

[0090] If ΔD, calculated by the wrist height detection unit 20d, is less than or equal to the permissible value, the blood pressure measurement unit 20a starts the blood pressure measurement according to an oscillometric procedure in this modified example and transmits the determined blood pressure value to the blood pressure correction unit 20f.

[0091] Based on the height difference ΔH between the radial artery and the ulnar artery, which was calculated by the artery-relative position determination unit 20c, the blood pressure correction unit 20f corrects the measured blood pressure value, which is calculated by the blood pressure measurement unit 20a, and causes the corrected blood pressure value to be displayed on the display unit 19.

[0092] Fig. Figure 9 is a diagram showing an example of a pulse wave amplitude envelope. Fig. 10 is a partially enlarged view of the Fig. 9. Fig. Figure 9 shows an envelope A, an envelope B, and an envelope C.

[0093] The envelope A is a pulse wave amplitude envelope generated by the blood pressure measuring unit 20a in the case where the entire pressure build-up pressure of the cuff 30 is transmitted to the radial artery without loss and the pressure build-up of the ulnar artery is insufficient.

[0094] The envelope B is a pulse wave amplitude envelope generated by the blood pressure measuring unit 20a in the case where the entire pressure build-up of the pressure of the cuff 30 is transmitted to the ulnar artery without loss and the pressure build-up of the radial artery is insufficient.

[0095] The envelope C is a pulse wave amplitude envelope generated by the blood pressure measuring unit 20a, in the case where the entire pressure build-up pressure of the cuff 30 is transmitted without loss to both the ulnar artery and the radial artery.

[0096] Note that Fig. 9. Data shows that if the height from the floor of the radial artery is 5 cm higher than the height from the floor of the ulnar artery (when ΔH=5 cm).

[0097] In the pulse wave amplitude envelope, which is in Fig. As shown in Figure 9, when the cuff pressure at which the pulse wave amplitude is 1 is determined, the systolic blood pressure is 98 [mmHg] corresponding to envelope A, the systolic blood pressure is 102 [mmHg] corresponding to envelope B, and the systolic blood pressure is 100 [mmHg] corresponding to envelope C.

[0098] In the present embodiment, it is assumed that the radial artery and the ulnar artery are pressurized uniformly by the cuff 30. In other words, the structure of the cuff 30 is designed such that the ratio of the transmission rate to the radial artery to the transmission rate to the ulnar artery of the pressure building-up pressure of the cuff 30 is: a:b=1:1.

[0099] Accordingly, if the heights of the radial artery and the ulnar artery do not coincide, and one of the radial and ulnar arteries coincides with the height of the heart, an error caused by the height difference (described above as ΔH) will occur in the measured blood pressure value determined by the blood pressure measuring unit 20a.

[0100] If there is a height difference ΔH (cm) between the two arteries, a pressure difference, which is obtained by multiplying ΔH by a hydraulic peak pressure per unit length (=0.8 mmHg / cm), will occur in the two arteries.

[0101] For example, in the case where the radial artery is in a higher position than the ulnar artery, the pressure difference between the radial and ulnar arteries corresponds to the difference between the systolic blood pressure determined by envelope A and the systolic blood pressure determined by envelope B, which is in Fig. 10 will be shown.

[0102] By determining the ratio of the radial artery transfer rate to the ulnar transfer rate of the cuff pressure build-up pressure 30 with a:b, the hydraulic pressure with β and the systolic blood pressure, which is determined by the envelope C, which in Fig. As shown in Figure 10, the systolic blood pressure P', which is determined by the envelope A, is determined using equation (4) below. Similarly, the systolic blood pressure P'', which is determined by the envelope B, is determined using equation (5) below. P'=P−[β×ΔH×{a / (a+b)}] P"=P+[β×ΔH×{b / (a+b)}]

[0103] The sign of ΔH is also taken into account in equations (4) and (5).

[0104] In equations (4) and (5), P is a value determined by the blood pressure measurement unit 20a. ΔH is also a value calculated by the artery-relative position determination unit 20c. Furthermore, a and b are values ​​determined by the structure of the cuff 30.

[0105] When the wrist height detection unit 20d calculates ΔD, assuming that the height from the reference plane of the blood pressure monitor 1 is the same as the height from the reference plane of the radial artery in the wrist to which the blood pressure monitor 1 is attached, or, in other words, when the blood pressure measurement is started in a state in which the height of the heart and the height of the radial artery are nearly the same, it is sufficient for the blood pressure correction unit 20f P' above to calculate as the final blood pressure value.

[0106] On the other hand, if the wrist height detection unit 20d calculates ΔD, assuming that the height from the reference plane of the blood pressure monitor 1 is the same as the height from the reference plane of the ulnar artery in the wrist to which the blood pressure monitor 1 is attached, or, in other words, if the blood pressure measurement is started in a state in which the height of the heart and the height of the ulnar artery are nearly the same, it is sufficient for the blood pressure correction unit 20f P'' above to calculate as the final blood pressure value.

[0107] The following describes the operation of CPU 20, which is in Fig. 8 is shown, described.

[0108] Fig. Figure 11 is a flowchart to describe a modified example of the operation of the blood pressure monitor 1.

[0109] When the start of the blood pressure measurement is instructed by the operation of the control unit 21, the CPU 20 measures the tilt angle θ1 of the forearm, based on the information detected by the accelerometer 17 (step S11).

[0110] Next, the CPU 20 uses the inclination angle θ1, which is measured in step S11, and the information regarding the upper arm length L1, the forearm length L2, the angle θ3, the distance Ha from the shoulder S of the measuring person 40 to the seat surface of the chair CH, the seat surface height Hb of the chair CH and the height Hb of the table T to calculate ΔT, using the calculation of equations (2) and (3) (step 12).

[0111] Based on ΔD, which is calculated in step S12, the CPU 20 determines whether the orientation of the person being measured is one in which blood pressure measurement is possible (step S13).

[0112] If ΔD is less than or equal to the permissible value, CPU 20 determines that this is an orientation in which blood pressure measurement is possible. If ΔD exceeds the permissible value, CPU 20 determines that this is an orientation in which blood pressure measurement is not possible.

[0113] If the result of the determination in step S13 is NO, the CPU 20 calculates the inclination angle θ1 at which ΔD is less than or equal to the permissible value and displays the information on the display unit 19 to guide the operator so that the inclination angle θ1 reaches the calculated angle (step S14). The CPU 20 then returns to processing step S11.

[0114] If the result of the determination of step S13 is YES, the CPU 20 starts the pressure build-up at the wrist using the cuff 30 and starts the blood pressure measurement using the oscillometric method (step S15).

[0115] The CPU 20 extracts a pulse wave from the cuff pressure signal (step S16) and generates the pulse wave amplitude envelope data (step S17). Then, the systolic and diastolic blood pressure values ​​are determined based on the pulse wave amplitude envelope data (step 18).

[0116] Next, the CPU 20 calculates the distance d between the radial artery and the ulnar artery based on the image generated by the artery detection unit 18 (step S19). The CPU 20 also measures the rotation angle θ2 based on the information detected by the accelerometer 7 (step S20).

[0117] Then the CPU 20 uses the tilt angle θ1, which is measured in step S11, the rotation angle θ2, which is measured in step S20, and the distance d, which is calculated in step S19, to calculate ΔH, using the calculation of equation (1) (step S21).

[0118] Next, the CPU 20 substitutes the systolic and diastolic blood pressures (each denoted as "P") determined in step S18 and calculates ΔH in step S21 in equations (4) and (5) to correct the systolic and diastolic blood pressures determined in step S18 (step S22).

[0119] Finally, the CPU 20 causes the value resulting from the correction step in step S22 to be displayed on the display unit 19 (step S23), and terminates operation in accordance with the blood pressure measurement instruction.

[0120] As described above, corresponding to the blood pressure monitor 1, in which the CPU 20, which is in Fig.As shown in Figure 8, even if the blood pressure is measured in a state where the height difference ΔH between the radial artery and the ulnar artery exceeds the permissible value, the blood pressure value determined by the blood pressure measuring unit 20a is corrected according to the height difference ΔH, and therefore an accurate blood pressure value can be measured without error.

[0121] It should be noted that the embodiment disclosed above is to be considered exemplary in all respects and in no way limiting. The scope of the present invention is not defined by the aforementioned descriptions, but by the scope of the appended claims, and any modifications which are in the same essential spirit as the scope of the claims are likewise to be included therein.

[0122] The present specification discloses the following elements.

[0123] The disclosed blood pressure measuring device is a blood pressure measuring device configured to be used while attached to the wrist of a subject and includes: a tilt angle measuring unit configured to measure a tilt angle, which is an angle formed by the subject's forearm with respect to a reference plane; a rotation angle measuring unit configured to measure a rotation angle about an axis, using the forearm as the axis, of the blood pressure measuring device; a distance information acquisition unit configured to acquire distance information regarding the distance between the ulnar artery and the radial artery running through the wrist; a determination unit configured to determine a relative positional relationship between the radial artery and the ulnar artery, using the tilt angle, the rotation angle, and the distance information;and a control unit which is configured to perform control according to the relative position relationship.

[0124] With the disclosed blood pressure measuring device, the control unit provides information, according to the relative positional relationship, for guiding the rotation angle to an angle at which the difference between the height from the reference plane of the radial artery and the height from the reference plane of the ulnar artery is less than or equal to a predetermined value, and the control unit includes a blood pressure measuring unit which is configured to start the measurement of the blood pressure when the determining unit has determined that the difference between the height from the reference plane of the radial artery and the height from the reference plane of the ulnar artery is less than or equal to the predetermined value.

[0125] The disclosed blood pressure measuring device includes an altitude detection unit configured to use the tilt angle to detect the height of the wrist relative to the heart of the person being measured, wherein, based on the height of the wrist and the relative positional relationship, the control unit outputs information for guiding the rotation angle and the tilt angle for angles at which the difference between the height from the reference plane of the radial artery and the height from the reference plane of the ulnar artery is less than or equal to a predetermined value and the height of the wrist relative to the heart of the person being measured is less than or equal to a predetermined value, and the control unit includes a blood pressure measurement unit configured to start the blood pressure measurement when determined by the determination unit.that the difference between the height from the reference plane of the radial artery and the height from the reference plane of the ulnar artery is less than or equal to a predetermined value, and that the height detected by the height detection unit is less than or equal to a predetermined value.

[0126] The disclosed blood pressure measuring device includes a blood pressure measuring unit configured to extract a pulse wave from the detected pressure in the cuff during a process of increasing or decreasing the pressure with which the cuff presses the wrist and measures the blood pressure based on an amplitude value of the pulse wave, wherein, according to the relative position relation, the control unit corrects the blood pressure value measured by the blood pressure measuring unit.

[0127] With the disclosed blood pressure measuring device, as the relative position relationship, the determining unit determines a difference ΔH between the height from the reference plane of the radial artery and the height from the reference plane of the ulnar artery, and the magnitude relationship between the heights from the reference plane of the radial artery and the ulnar artery, and a value which is obtained by multiplying the ΔH, a hydraulic peak pressure per unit length, and a coefficient which corresponds to a ratio between a transmission rate of the pressure with which the cuff pressurizes the radial artery and a transmission rate of the pressure with which the cuff pressurizes the ulnar artery, corresponding to the magnitude relationship which is added to or subtracted from the blood pressure value which is measured by the blood pressure measuring unit, and thereby the blood pressure value is corrected.

[0128] The disclosed blood pressure measuring device includes a sensor configured to emit light to the wrist, to receive light reflected from the wrist and to convert the light into an electrical signal, and a distance information generation unit configured to generate the distance information based on the sensor's output signal.

[0129] The disclosed control method for the blood pressure monitor is a control method for a blood pressure monitor configured to be used while attached to the wrist of a subject, comprising: an inclination angle measurement step for measuring an inclination angle, which is an angle formed by a forearm of the subject with respect to a reference plane; a rotation angle measurement step for measuring a rotation angle about an axis, the forearm being used as the axis, of the blood pressure monitor; a distance information acquisition step for acquiring distance information regarding the distance between the radial artery and the ulnar artery passing through the wrist; and a determination step for determining a relative positional relationship between the radial artery and the ulnar artery, using the inclination angle, the rotation angle, and the distance information.and a control step of carrying out the control, corresponding to the relative position relationship.; Industrial applicability

[0130] The present invention can, for example, be applied to a blood pressure monitor for home use and is useful for monitoring a user's health.

[0131] While the present invention has been described in detail with reference to a specific embodiment, it will be clear to a person skilled in the art that many variations and modifications can be made without departing from the essential spirit and scope of the present invention. This application claims priority from Japanese patent application No. 2012-211139, filed on September 25, 2012, which is incorporated herein in its entirety for reference. Reference symbol list 1 blood pressure monitor 10 Main Device Sub-area 30 cuff 11 Pressure sensor 17 Three-axis accelerometer 19 Display unit 20 CPU 20a Blood pressure measuring unit 20b Inter-artery distance information generation unit 20c Artery-relative position-determination unit 20d Wrist Height Detection Unit 20e, 20e' Measuring alignment guide unit 20f blood pressure correction unit 20h angle measuring unit 21 Control unit 40 measuring personnel 50 wrist 51 Radial Artery 52 Ulnar artery d Inter-artery distance F Forearm U upper arm θ1 Angle of inclination θ2 rotation angle ΔD Height difference between measuring point and heart H

Claims

[1] A blood pressure monitor configured to be used while attached to the wrist of a person being measured, wherein the blood pressure monitor comprises: a tilt angle measuring unit which is configured, to measure an angle of inclination, which is an angle formed by the forearm of the person being measured with respect to a reference plane; a rotation angle measuring unit configured to measure a rotation angle of the blood pressure monitor around an axis, using a forearm as the axis; a distance information acquisition unit configured to acquire distance information regarding the distance between the ulnar artery and the radial artery that run through the wrist; a determination unit configured to determine a relative positional relationship between the radial artery and the ulnar artery, using the inclination angle, rotation angle, and distance information; and a control unit which is configured to perform the control according to the relative position relationship. [2] Blood pressure measuring device according to claim 1, wherein the control unit outputs information according to the relative position relationship in order to guide the rotation angle to an angle at which the difference between a height from the reference plane of the radial artery and a height from the reference plane of the ulnar artery is less than or equal to a predetermined value, and the control unit includes a blood pressure measuring unit which is configured to start the measurement of the blood pressure when the determining unit determines that the difference between the height from the reference plane of the radial artery and the height from the reference plane of the ulnar artery is less than or equal to the predetermined value. [3] Blood pressure measuring device according to claim 1, which further comprises: a height detection unit, wherein the angle of inclination is used to detect the height of the wrist relative to the heart of the person being measured, wherein, Based on the height of the wrist and the relative position relationship, the control unit outputs information to guide the rotation angle and tilt angle to angles. where the difference between a height from the reference plane of the radial artery and a height from the reference plane of the ulnar artery is less than or equal to a predetermined value, and the height of the wrist relative to the heart of the subject is less than or equal to a predetermined value, and The control unit includes a blood pressure measurement unit which is configured to start measuring blood pressure when the determination unit determines that the difference between the height from the radial artery reference plane and the height from the ulnar artery reference plane is less than or equal to a predetermined value, and the height detected by the height detection unit is less than or equal to a predetermined value. [4] Blood pressure measuring device according to claim 1, which further comprises: a blood pressure measuring unit configured to extract a pulse wave from a detected pressure in the cuff during a process of increasing or decreasing the pressure with which the cuff presses against the wrist, and to measure the blood pressure based on an amplitude value of the pulse wave, wherein, According to the relative position relationship, the control unit corrects the blood pressure value measured by the blood pressure measuring unit. [5] Blood pressure measuring device according to claim 4, wherein, as the relative positional relationship, the unit of determination a difference ΔH, between the height from the reference plane of the radial artery and the height from the reference plane of the ulnar artery, as well as a size relationship, between the heights from the reference plane of the radial artery and the ulnar artery, where the size relationship indicates which of the radial artery and the ulnar artery is placed at a higher position with respect to the reference plane, and a value which is determined by multiplying ΔH, a hydraulic peak pressure per unit length, and a coefficient which is corresponding to a ratio between a transmission rate of the pressure with which the cuff pressure pressurizes the radial artery and a transmission rate of the pressure with which the cuff pressurizes the ulnar artery, corresponding to the magnitude relationship to which the blood pressure value measured by the blood pressure measuring unit is added or subtracted, thereby correcting the blood pressure value. [6] Blood pressure measuring device according to any one of claims 1 to 5, which further comprises: a sensor configured to emit light to the wrist, receive light reflected from the wrist, and convert the light into an electrical signal; and a distance information generation unit which is configured to generate distance information based on the sensor's output signal. [7] Control procedure for a blood pressure monitor configured to be used while attached to the wrist of a subject, the procedure comprising: an inclination angle measurement step of measuring an inclination angle, which is an angle formed by a forearm of the measuring person with respect to a reference plane; a rotation angle measurement step of measuring a rotation angle of the blood pressure monitor around an axis, using the forearm as the axis; a distance information acquisition step of acquiring distance information regarding the distance between the radial artery and the ulnar artery, which run through the wrist; a determination step of establishing a relative positional relationship between the radial artery and the ulnar artery, using the angle of inclination, the angle of rotation, and the distance information; and a control step of carrying out the control according to the relative position relationship.

Images