JP5239640B2 - Blood pressure information measuring device - Google Patents

Description

  The present invention relates to a blood pressure information measuring device, and more particularly, to a blood pressure information measuring device capable of measuring blood pressure information using a volume compensation method.

  Conventionally, blood pressure measurement using a volume compensation method has been developed as a technique that can easily and non-invasively measure blood pressure. The volume compensation method is as follows. That is, the artery is compressed from outside the living body with a cuff, and the pressure of the measurement site (cuff pressure) and the internal pressure of the artery at the measurement site, that is, the blood pressure, are maintained by constantly maintaining the volume of the artery that pulsates in synchronization with the heartbeat. In this method, the blood pressure value is continuously obtained by detecting the cuff pressure when the equilibrium state is maintained and the equilibrium state is maintained.

  Therefore, in the volume compensation method, there are two points: detection of a volume value when the artery is in an unloaded state, that is, a control target value (hereinafter also referred to as “V0”), and maintaining this unloaded state (servo control). Is important. In particular, the determination of V0 is very important because it directly affects the accuracy of blood pressure measurement.

  As a determination method of V0, for example, there is a method of determining V0 by gradually compressing an artery with a cuff and detecting the maximum point of an arterial volume change signal obtained at that time (Patent Document 1). .

  In addition, proposals for realizing a reduction in time required for determining V0 have been made. For example, in Patent Document 2, high-frequency micro-pressure vibration (for example, 20 Hz, 10 mmHg sinusoidal pressure vibration) is superimposed on the cuff pressure, and a point at which the arterial volume change due to the high-frequency micro-pressure vibration is maximized is detected. Determine V0.

Regarding the reduction of the blood pressure measurement time, although different from the volume compensation method, conventionally, the cuff pressure is rapidly increased or decreased within one heartbeat, and the pulse wave indicating the moment when the intraarterial pressure = cuff pressure is reached. There is a technique for detecting a feature point and determining a cuff pressure at that time as a blood pressure value (Patent Document 3).
Japanese Patent No. 1547959 (Japanese Patent Laid-Open No. 59-156325) JP 2008-36004 A US Pat. No. 6,802,816

  Although the method of Patent Document 1 can accurately detect V0, it takes time to determine V0, and therefore cannot continuously start continuous blood pressure measurement. In addition, during continuous blood pressure measurement, V0 may fluctuate due to blood pressure fluctuations, stress, environmental changes, etc., and it is necessary to redetect V0 each time. Therefore, the blood pressure value cannot be measured during the re-determination of V0.

  Further, according to the invention of Patent Document 2, although V0 can be determined in a short time, there is a problem that accuracy is deteriorated as compared with the method of Patent Document 1.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a volume compensation type blood pressure information measuring apparatus capable of determining a control target value accurately and in a short time. That is.

  A blood pressure information measurement device according to an aspect of the present invention is a blood pressure information measurement device for measuring blood pressure information by detecting the volume of an artery, and includes a cuff for wrapping around a predetermined measurement site, and a pressure in the cuff Adjusting means for adjusting pressure by pressurizing and depressurizing, pressure detecting means for detecting a cuff pressure representing the pressure in the cuff, and an arterial that is disposed at a predetermined position of the cuff and is compressed with the cuff. First volume detection means for detecting a first arterial volume signal representing a change in volume, and a second arterial volume arranged upstream of the cuff and representing a change in volume associated with arterial pulsation First volume detection means for detecting a signal and control means for performing control for measuring blood pressure information according to the volume compensation method. The control means includes servo control means for servo-controlling the adjustment means so that the arterial volume is constant based on the first arterial volume signal, and first and second arterial volume signals and cuff pressure. Based on the determination processing means for determining the control range of the cuff pressure when detecting the control target value by the servo control means, and by gradually changing the cuff pressure in the control range determined by the determination processing means Detection processing means for detecting a control target value based on the first arterial volume signal, and the servo control means includes a control target value in which the value of the first arterial volume signal is detected by the detection processing means. Servo control to match. The determination processing means controls the adjustment means to adjust the cuff pressure instantaneously, and the first and second arterial volume signals obtained in the instantaneous change period representing the control period by the adjustment control means. And calculating means for estimating the maximum blood pressure and the minimum blood pressure based on the cuff pressure and calculating the estimated maximum blood pressure and the minimum blood pressure as the upper limit value and the lower limit value of the control range, respectively.

  Preferably, the calculating means detects the blood pressure value by detecting a feature point in the first arterial volume signal indicating the occlusion end point of the artery based on the first arterial volume signal and the cuff pressure obtained during the instantaneous change period. The maximum blood pressure and the minimum blood pressure are calculated based on the calculated blood pressure value, the level of the second arterial volume signal at the time when the occlusion end point is detected, and the pulse pressure value indicating the pulse pressure of the measurement subject. presume.

  Preferably, the adjustment control means changes within one heartbeat from a predetermined pressure value until at least an occlusion end point is detected.

Preferably, the pulse pressure value is a predetermined value.
Preferably, the predetermined value is the maximum level of pulse pressure.

  Preferably, the adjustment control means executes adjustment of the cuff pressure within one heartbeat twice, and the calculation means calculates blood pressure values for two heartbeats, and estimates the pulse pressure values from the blood pressure values for two heartbeats.

  According to the present invention, since the control range of the cuff pressure at the time of detecting the control target value is determined instantaneously, the time required for detecting the control target value can be shortened. Further, since the detection of the control target value is executed in the process of gradually changing the cuff pressure as in the conventional case, the detection accuracy of the control target value can be kept high.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  The blood pressure information measurement device according to the embodiment of the present invention measures blood pressure information based on a volume compensation method. In the present embodiment, “blood pressure information” is information indicating the characteristics of the circulatory system, and includes at least a pulse wave. In addition to the pulse wave, an index that can be calculated from the pulse wave, for example, a maximum blood pressure, a minimum blood pressure , Mean blood pressure, pulse rate, AI (Augmentation Index) value, and the like.

  The pulse wave, which is one of the blood pressure information, includes a pressure pulse wave and a volume pulse wave due to the difference in the target to be captured. The pressure pulse wave is obtained by converting the fluctuation of the intravascular volume accompanying the heartbeat into the volume change of the cuff, and capturing the pulse wave as the fluctuation of the cuff pressure accompanying the volume change of the cuff. Can be obtained based on the output. The volume pulse wave is obtained by capturing the pulse wave as a change in the intravascular volume accompanying the pulsation of the heart, and can be obtained based on the output from the arterial volume sensor. It should be noted that the change in the intravascular volume can be regarded as a change in the amount of blood tissue in the blood vessel.

  The term blood pressure information measuring device used in the present specification refers to all devices having at least a function of acquiring a pulse wave, and more specifically, blood tissue by an optical technique in order to follow the volume compensation method. It refers to a device that detects volume fluctuations and acquires volume pulse waves. In that sense, it is not limited to outputting the acquired volume pulse wave as it is as a measurement result, but only the specific index as described above calculated or measured based on the acquired volume pulse wave is output as the measurement result. And those that output both plethysmograms and specific indices as measurement results.

  In a conventional typical volume compensation method type blood pressure information measuring apparatus, V0 (control target value) is detected by a method as described in Japanese Patent No. 1547959 (Patent Document 1). Specifically, the cuff is gradually pressurized from a pressure sufficiently lower than the minimum blood pressure to a pressure sufficiently higher than the maximum blood pressure (pressurization speed: 3 to 5 mmHg / sec). Within that period, the maximum value of the arterial volume change signal (AC component of volume pulse wave) is detected, and the arterial volume signal (DC component of volume pulse wave) at that time is set to V0. This utilizes the property that when the cuff pressure matches the subject's intra-arterial pressure (blood pressure), the arterial wall becomes unloaded (external pressure and intra-arterial pressure are balanced), and the arterial volume change is greatest. It is the method.

  In general, since the blood pressure value of the subject is not known in advance, the pressure range for pressurizing the cuff for V0 detection needs to be applicable to a wide range of subjects such as 40 mmHg to 280 mmHg. For this reason, it takes about 1 minute to detect V0 (for example, 60 seconds is required when 240 mmHg is pressurized at 4 mmHg / sec). If the blood pressure values (maximum blood pressure and minimum blood pressure) are known in advance, the pressure range for pressurizing the cuff can be limited, so the time required for V0 detection can be shortened.

  Therefore, it is conceivable to estimate the systolic blood pressure and the diastolic blood pressure of the measurement subject before the V0 detection control. When the conventional oscillometric method is used, the blood pressure measurement requires at least about 30 seconds, so that the overall time cannot be reduced. On the other hand, as a method for shortening the measurement time, as described above, the cuff pressure that compresses the artery is rapidly increased and decreased, and the feature point on the pulse wave (arterial pressure) indicating the moment when the arterial pressure = cuff pressure is reached. There is a method in which the cuff pressure at that time is measured as a blood pressure value (US Pat. No. 6,802,816 (Patent Document 3)).

  The principle is as follows. The artery compressed by the cuff undergoes a volume change depending on the magnitude of the external pressure, that is, the cuff pressure and the blood pressure. Since the blood pressure changes between the highest blood pressure and the lowest blood pressure within one heart cycle, the arterial volume changes accordingly.

  FIG. 1 is a diagram showing the relationship between the arterial volume signal characteristic and the systolic blood pressure when the cuff pressure is instantaneously increased. In FIG. 1A, a volume pulse wave (reference pulse wave) indicating a volume change accompanying pulsation is shown along the time axis. In FIG. 1B, the relationship between the change in cuff pressure and the virtual intra-arterial pressure is shown along the same time axis as in FIG. FIG. 1C shows a typical example of a change in arterial volume signal (measurement pulse wave) accompanying a change in cuff pressure along the same time axis as in FIG.

  As shown in FIG. 1B, when the cuff pressure is larger than the intra-arterial pressure, the artery is temporarily crushed by the cuff pressure. Then, as shown in FIG. 1C, the waveform of the detected arterial volume becomes flat. This section is referred to as the “occlusion section” of the artery.

  Referring to FIGS. 1B and 1C, the occlusion end point Ps when the cuff pressure is reduced from a value higher than the maximum blood pressure (SYS) (in contrast, when the cuff pressure is increased from a value lower than the minimum blood pressure). Is called the “occlusion start point”) is the moment when the cuff pressure coincides with the blood pressure at a certain time within one heartbeat. Therefore, by detecting the feature point Ps, the blood pressure value BPx at that time can be measured. Hereinafter, the blood pressure value thus measured is also referred to as “instantaneous blood pressure value”.

  Further, by simultaneously recording an arterial volume signal detected on the upstream side of the cuff (air bag) as a reference pulse wave as shown in FIG. 1 (A), the relationship between the blood pressure value and the arterial volume at the occlusion end point Ps can be obtained. It is possible to determine the point at which the end point Ps of the occlusion occurs at one point in one heart cycle (that is, the point in time at which the obtained instantaneous blood pressure value BPx is in one heart cycle). . Accordingly, the systolic blood pressure can be measured by appropriately controlling the cuff pressure so that the closing end point Ps is generated at the systolic blood pressure Pb.

  Similarly, the minimum blood pressure can also be measured if the cuff pressure is appropriately controlled so that the occlusion end point Ps occurs at the time point Pa of the minimum blood pressure (DIA). FIG. 2 shows the relationship between the arterial volume signal characteristic and the minimum blood pressure when the cuff pressure is instantaneously increased. 2A to 2C are the same as FIGS. 1A to 1C, respectively.

  However, since the blood pressure value and the pulse interval constantly fluctuate, it is very difficult to control the cuff pressure so as to coincide with the blood pressure at the time points Pa and Pb of the maximum blood pressure and the minimum blood pressure. For this reason, even when such a technique is used, it takes time to adjust the cuff pressure increasing / decreasing timing, and therefore the measurement time becomes long.

  Therefore, in the present invention, instead of measuring the systolic blood pressure and the diastolic blood pressure by adjusting the timing of pressure increase / decrease, the obtained instantaneous blood pressure value and the information on the end point of occlusion are used to detect V0. Determine the cuff pressure control range (pressure range).

  Hereinafter, embodiments of the present invention will be described in detail. In this specification, the closure start point and the closure end point are also collectively referred to as a “closure end point”.

<Appearance and configuration>
(About appearance)
FIG. 3 is an external perspective view of the blood pressure information measuring device 1 according to the embodiment of the present invention. The appearance of the blood pressure information measuring device 1 is the same as that of a general blood pressure monitor.

  With reference to FIG. 3, the blood pressure information measurement device 1 includes a main body 10 and a cuff 20 that can be wound around the wrist of the measurement subject. The main body 10 is attached to the cuff 20. On the surface of the main body unit 10, a display unit 40 made of, for example, liquid crystal and an operation unit 41 for receiving instructions from a user (a person to be measured) are arranged. The operation unit 41 includes a plurality of switches.

  In the present embodiment, the cuff 20 is described as being attached to the wrist of the measurement subject. However, the site where the cuff 20 is worn (measurement site) is not limited to the wrist, and may be, for example, the upper arm.

  Moreover, the blood pressure information measurement device 1 according to the present embodiment will be described with an example in which the main body 10 is attached to the cuff 20 as shown in FIG. However, the main body part 10 and the cuff 20 may be connected by an air tube (the air tube 31 in FIG. 5) as used in the upper arm blood pressure information measuring device.

(About hardware configuration)
FIG. 4 is a block diagram showing a hardware configuration of blood pressure information measuring apparatus 1 according to the embodiment of the present invention.

  Referring to FIG. 4, the cuff 20 of the blood pressure information measurement device 1 includes an air bag 21 and two arterial volume sensors 70A and 70B. The arterial volume sensor 70A is provided to detect a change in the arterial volume accompanying the compression of the cuff 20, and includes a light emitting element 71A and a light receiving element 72A. The arterial volume sensor 70B is provided to detect a change in the arterial volume accompanying the pulsation of the artery without being affected by the compression of the cuff 20, and includes a light emitting element 71B and a light receiving element 72B.

  Each light emitting element 71A, 71B irradiates light to the artery, and each light receiving element 72A, 72B receives the transmitted light or reflected light of the artery irradiated by the light emitting elements 71A, 71B, respectively.

  FIG. 5 is a diagram illustrating an arrangement example of the arterial volume sensor 70A and the arterial volume sensor 70B. Referring to FIG. 5, light emitting element 71 </ b> A and light receiving element 72 </ b> A constituting arterial volume sensor 70 </ b> A are arranged, for example, at a predetermined interval inside air bag 21. If the light emitting element 71B and the light receiving element 72B constituting the arterial volume sensor 70B are arranged on the upstream side of the cuff 20, that is, on the outside of the portion compressed by the cuff 20 and near the heart on the surface of the measurement site. Good. In the present embodiment, it is assumed that at least a part of the arterial volume sensor 70B is adhered to the cuff 20 at a predetermined interval. However, the present invention is not limited to this configuration, and the arterial volume sensor 70B is separated from the cuff 20. It may be provided and arranged by the user.

  The arterial volume sensor 70 may be any sensor that can detect the volume of the artery, and may detect the volume of the artery using an impedance sensor (impedance plethysmograph). In that case, instead of each light emitting element 71A, B and each light receiving element 72A, B, a plurality of electrodes (an electrode pair for current application and an electrode pair for voltage detection) for detecting the impedance of a site including an artery ) Is included.

The air bag 21 is connected to the air system 30 via the air tube 31.
In addition to the display unit 40 and the operation unit 41 described above, the main body unit 10 controls the air system 30, a CPU (Central Processing Unit) 100 for centrally controlling each unit and performing various arithmetic processes, A memory unit 42 for storing programs and various data for operation, a non-volatile memory (for example, a flash memory) 43 for storing measured blood pressure information, a power source 44 for supplying power to the CPU 100, It includes a timekeeping unit 45 that performs a timekeeping operation, and an interface unit 46 for reading and writing programs and data from the removable recording medium 132.

  The operation unit 41 includes a power switch 41A that receives an input of an instruction for turning on or off the power supply, a measurement switch 41B that receives an instruction to start measurement, a stop switch 41C that receives an instruction to stop measurement, and a flash And a memory switch 41D for receiving an instruction to read information such as blood pressure recorded in the memory 43.

  The air system 30 includes a pressure sensor 32 for detecting the pressure (cuff pressure) in the air bag 21, a pump 51 for supplying air to the air bag 21 to pressurize the cuff pressure, and the air bag 21. And a valve 52 that is opened and closed to exhaust or enclose the air.

  The main body 10 further includes light emitting element drive circuits 73A and 73B, arterial volume detection circuits 74A and 74B, an oscillation circuit 33, a pump drive circuit 53, and a valve drive circuit 54 in relation to the air system 30. Including.

  The light emitting element drive circuit 73A causes the light emitting element 71A to emit light at a predetermined timing in response to a command signal from the CPU 100. Similarly, the light emitting element driving circuit 73B causes the light emitting element 71B to emit light at a predetermined timing in response to a command signal from the CPU 100.

  The arterial volume detection circuit 74A detects the arterial volume by converting the output from the light receiving element 72A into a voltage value. Similarly, the arterial volume detection circuit 74B detects the arterial volume by converting the output from the light receiving element 72B into a voltage value.

  In the present embodiment, two light emitting element drive circuits 73A and 73B are provided for the two light emitting elements 71A and 71B, respectively. However, each light emitting element drive circuit drives each of the issuing elements 71A and 71B. It is good as well. Similarly, one arterial volume detection circuit may receive signals from the two light receiving elements 72A and 72B, and each may be distinguished and output to the CPU 100.

  The pressure sensor 32 is a capacitance-type pressure sensor, and the capacitance value changes depending on the cuff pressure. The oscillation circuit 33 outputs an oscillation frequency signal corresponding to the capacitance value of the pressure sensor 32 to the CPU 100. The CPU 100 detects a pressure by converting a signal obtained from the oscillation circuit 33 into a pressure. The pump drive circuit 53 controls the drive of the pump 51 based on a control signal given from the CPU 100. The valve drive circuit 54 performs opening / closing control of the valve 52 based on a control signal given from the CPU 100.

  The pump 51, the valve 52, the pump drive circuit 53, and the valve drive circuit 54 constitute an adjustment mechanism 50 for adjusting the pressure in the cuff 20 by pressurization and pressure reduction. In addition, the apparatus which comprises the adjustment mechanism 50 is not limited above. For example, in addition to the above, the adjustment mechanism 50 may include an air cylinder and an actuator for driving the air cylinder.

  In addition, although the cuff 20 includes the air bag 21, the fluid supplied to the cuff 20 is not limited to air, and may be a liquid or a gel, for example. Or it is not limited to fluid, Uniform microparticles, such as a microbead, may be sufficient.

(About functional configuration)
FIG. 6 is a functional block diagram showing a functional configuration of the blood pressure information measurement device 1 according to the embodiment of the present invention.

  Referring to FIG. 6, CPU 100 includes a cuff pressure acquisition unit 102, a range determination processing unit 103, a detection processing unit 104, a servo control unit 106, and a blood pressure determination unit 108. For the sake of simplicity, FIG. 6 shows only peripheral hardware that directly exchanges signals and data with these functional blocks.

  The cuff pressure acquisition unit 102 acquires the cuff pressure based on the signal from the oscillation circuit 33. More specifically, the cuff pressure is acquired by converting the signal of the oscillation frequency detected by the oscillation circuit 33 into a pressure. The acquired cuff pressure is output to the range determination processing unit 103, the detection processing unit 104, the servo control unit 106, and the blood pressure determination unit 108.

  The range determination processing unit 103 determines the control range of the cuff pressure in the detection processing unit 104 described later by estimating the maximum blood pressure and the minimum blood pressure of the measurement subject. The range determination processing unit 103 includes an adjustment control unit 112 and a calculation unit 114.

  The adjustment control unit 112 changes the cuff pressure instantaneously by controlling the pump drive circuit 53 and the valve drive circuit 54 of the adjustment mechanism 50. Specifically, the adjustment control unit 112 changes the predetermined pressure value until at least the closed end point is detected within one heartbeat. Note that “changing the cuff pressure” means either increasing the cuff pressure or decreasing the cuff pressure, and in the present embodiment, it is assumed to be the former. The pressurization speed may be a speed that can pressurize the section within one heartbeat of the person to be measured, and may be a predetermined speed.

  The calculation unit 114 detects the cuff pressure obtained from the cuff pressure acquisition unit 102 and the arterial volume signal obtained from the arterial volume detection circuit 74A (referred to as “pulse wave for measurement”) during the instantaneous change period representing the control period by the adjustment control unit 112. ) And an arterial volume signal (hereinafter referred to as “reference pulse wave”) obtained from the arterial volume detection circuit 74B. Then, based on these pieces of input information, the subject's systolic blood pressure and diastolic blood pressure are estimated, and the estimated systolic blood pressure and diastolic blood pressure are respectively calculated as the upper limit value and the lower limit value of the control range.

  In the present embodiment, the calculation unit 114 detects the feature point of the measurement pulse wave that indicates the occlusion end point of the artery (the occlusion start point in the case of pressurization) based on the reference pulse wave and the cuff pressure. Thus, the blood pressure value (instantaneous blood pressure value) in the instantaneous change period is calculated. Then, the maximum blood pressure and the minimum blood pressure are estimated based on the calculated instantaneous blood pressure value, the level of the reference pulse wave at the time when the closed end point is detected, and the pulse pressure value indicating the pulse pressure of the measurement subject.

  The detection processing unit 104 pressurizes the cuff 20 from the lower limit value to the upper limit value determined by the range determination processing unit 103, and acquires an arterial volume signal (measurement pulse wave) from the arterial volume detection circuit 74A in the process. Also, an arterial volume change signal (AC component of the arterial volume signal) representing a change (amplitude) of the arterial volume signal for each beat is detected. The arterial volume change signal can be obtained, for example, by filtering the arterial volume signal.

  As described above, the measurement pulse wave is used to detect a feature point indicating the occlusion end point, and the reference pulse wave is used to detect at which point in the heartbeat cycle the occlusion end point is generated. .

  A method for determining V0 and PC0 by the detection processing unit 104 may be the same as that of the above-mentioned Japanese Patent No. 1547959 (Patent Document 1). In the present embodiment, for example, the value (preferably the average value for one beat) of the arterial volume signal at the time when the maximum value of the arterial volume change signal is detected is determined as V0, and the cuff pressure at that time is PC0. Determine as.

  The servo control unit 106 is connected to the adjustment mechanism 50 and performs servo control so that the value of the arterial volume signal (arterial volume value) obtained from the arterial volume detection circuit 74A matches V0. That is, the pressure in the cuff 20 is feedback-controlled so that the value of the arterial volume change signal becomes almost zero. This control is called arterial volume constant control.

  The blood pressure determination unit 108 continuously determines (measures) blood pressure during the servo control period. Specifically, the arterial volume detection circuit 74A acquires the arterial volume signal and the cuff pressure signal from the cuff pressure acquisition unit 102 in time series, and the cuff at the time when the difference between the arterial volume value and V0 is equal to or less than a predetermined threshold value. The pressure is determined as blood pressure.

  Note that, during a series of blood pressure measurement periods, the CPU 100 transmits a command signal to the light emitting element driving circuit 73A to cause the light emitting elements 71A to emit light at regular intervals. Further, it is assumed that the CPU 100 causes the light emitting element 71B to emit light at regular intervals by transmitting a command signal to the light emitting element driving circuit 73B at least during the processing period by the range determination processing unit 103.

  The operation of each functional block included in the CPU 100 may be realized by executing software stored in the memory unit 42, and at least one of these functional blocks is realized by hardware. May be.

<About operation>
FIG. 7 is a flowchart showing blood pressure measurement processing in the embodiment of the present invention. The processing shown in the flowchart of FIG. 7 is stored in advance in the memory unit 42 as a program, and the blood pressure measurement processing function is realized by the CPU 100 reading and executing this program.

  Referring to FIG. 7, CPU 100 determines whether or not power switch 41A has been pressed (step S2). If it is determined that power switch 41A has been pressed (YES in step S2), the process proceeds to step S4.

  In step S4, the CPU 100 performs an initialization process. Specifically, for example, a predetermined area of the memory unit 42 is initialized, the air in the air bladder 21 is exhausted, and 0 mmHg correction of the pressure sensor 32 is performed.

  When the initialization is completed, the CPU 100 determines whether or not the measurement switch 41B has been pressed (step S6). Wait until the measurement switch 41B is pressed. If it is determined that measurement switch 41B has been pressed (YES in step S6), the process proceeds to step S7.

  In step S <b> 7, the range determination processing unit 103 executes a control range determination process. The control range determination process will be described later with reference to the flowchart of FIG. 8 and FIG.

  When the control range is determined, the detection processing unit 104 executes a control target value detection process. That is, V0 and PC0 are determined. The control target value detection process will be described later with reference to the flowchart of FIG.

  When V0 and PC0 are determined, the servo control unit 106 sets the cuff pressure to PC0 (step S10). Thereby, the cuff pressure is adjusted so that the arterial volume signal and V0 coincide.

  Next, the servo control unit 106 performs arterial volume constant control so that the arterial volume signal coincides with V0 (step S12). That is, by controlling the adjusting mechanism 50, the cuff pressure is feedback-controlled so that the value of the arterial volume change signal becomes almost zero. The arterial volume change signal can be obtained, for example, by filtering the arterial volume signal.

  In parallel with the constant arterial volume control, the blood pressure determination unit 108 determines whether or not the difference between the arterial volume (value indicated by the arterial volume signal) and V0 is equal to or less than a predetermined threshold (step S14). . That is, it is determined whether or not the value of the volume change signal is close to zero (whether it is equal to or less than a predetermined threshold).

  When it is determined that the difference between the arterial volume and V0 is equal to or less than the threshold value (YES in step S14), the blood pressure determination unit 108 determines the cuff pressure at that time as the blood pressure and stores it in the flash memory 43 (step S16). . When the process of step S16 ends, the process proceeds to step S18.

  On the other hand, when it is determined that the difference between the arterial volume and V0 exceeds a predetermined threshold (NO in step S14), the process proceeds to step S18. That is, when it cannot be said that the arterial volume and V0 are substantially equal, the cuff pressure at that time is not determined as the blood pressure value.

  In step S18, the servo control unit 106 determines whether or not the stop switch 41C is pressed. If it is determined that stop switch 41C has not been pressed (NO in step S18), the process returns to step S12. If it is determined that stop switch 41C has been pressed (YES in step S18), the series of blood pressure measurement processes is terminated. In the present embodiment, the blood pressure measurement process is terminated when the pressing of the stop switch 41C is detected. However, when the predetermined time has elapsed since the start of the arterial volume constant control, the blood pressure measurement process is terminated. It is good.

Hereinafter, the control range determination process and the control target value detection process will be described in detail.
(About control range determination processing)
The process will be described with reference to FIGS.

  FIG. 8 is a flowchart showing a control range determination process in the embodiment of the present invention. FIG. 9 is a diagram showing the volume level at each feature point of the reference pulse wave.

  Referring to FIG. 8, first, adjustment control unit 112 of range determination processing unit 103 sets the cuff pressure to the initial cuff pressure value (step ST21). When instantaneous blood pressure is measured by rapid pressurization, the initial cuff pressure is sufficiently lower than the lowest blood pressure of the person to be measured, and may be, for example, 0 mmHg.

  Next, the range determination process part 103 performs the detection process of the rise of a pulse from a reference pulse wave (step ST22). The rising point of the pulse (point Pa11 in FIG. 9) can be detected by various methods, but in general, the amplitude of the signal in which the rising is emphasized is extracted by applying a high-pass filter or differentiation processing to the pulse wave signal. A point where the extracted amplitude value exceeds a predetermined threshold can be detected as a rising point.

  The process of step ST22 is executed until the rising edge of the pulse is detected (NO in step ST23).

  When range determination processing section 103 determines that the rise of the pulse has been detected (YES in step ST23), it starts pressurization (step ST24). The pressurization speed is set to a value set in advance so as to be approximately equal to the rising speed of the pulse wave. For example, a standard case is assumed in which the pulse pressure (difference between the maximum blood pressure and the minimum blood pressure) is 50 mmHg and the rise time of the pulse is 0.1 seconds. In that case, the pressurization speed may be 500 mmHg / s. The pressurization speed is not limited to such a value, and is preferably set to a speed in consideration of a general adult pulse pressure and heart rate, for example, between 300 and 800 mmHg / s.

  The cuff pressurization is continued until it is determined that the closing start point (same as the point Ps in FIGS. 1 and 2) has been detected (step ST30).

  Subsequent to the cuff pressurizing process, the calculation unit 114 of the range determination processing unit 103 detects the maximum value and the minimum value within one heartbeat of the reference pulse wave. The calculation unit 114 determines whether or not the current reference pulse wave is the maximum value, and if it is determined to be the maximum value (YES in step ST25), stores (updates) the value in the memory unit 42 (step ST26). ). Similarly, it is determined whether or not the current reference pulse wave is the minimum value. If it is determined to be the minimum value (YES in step ST27), the value is stored (updated) in the memory unit 42 (step ST28).

  Subsequently, the calculation unit 114 detects an occlusion start point from the measurement pulse wave (step ST29). The occlusion start point can be detected by various methods. For example, the rise of the pulse wave for measurement may be detected by a method equivalent to the detection of the pulse rise from the reference pulse wave described above. If it is determined that an occlusion start point has been detected (YES in step ST30), the cuff pressure at that time is detected as an instantaneous blood pressure value (represented as “BP_inst”), and at the same time, a reference pulse wave at that time (time tPs in FIG. 9). Level (represented as “Lp_inst”) is detected (step ST31). These detected values are stored in the memory unit 42.

  After the occlusion start point is detected, the cuff pressure is maintained at a value equal to the value at the time of the occlusion start point detection (that is, the instantaneous blood pressure value (Bp_inst)) until the process proceeds to the control target value detection process (step ST32). Thereby, the adjustment time of the cuff pressure after shifting to the control target value detection process can be shortened.

  When it is determined that the next rising edge (point Pa12 in FIG. 9) has been detected from the reference pulse wave after starting cuff pressurization (NO in step ST33), the reference pulse stored in the memory unit 42 The maximum value of the wave is determined as the pulse wave level at the time of the highest blood pressure (represented as “Lp_sys”), and similarly the minimum value of the reference pulse wave is determined as the pulse wave level at the time of the lowest blood pressure (represented as “Lp_dia”) ( Step ST34).

  Thereafter, the maximum cuff pressure control value (represented as “Pc_max”) and the minimum cuff pressure control value (represented as “Pc_min”) are calculated by the following equations (1) and (2) (step ST35). These values Pc_max and Pc_min are the upper limit value and the lower limit value of the cuff pressure control range in the control target value detection process.

  In the above formula (1), “PP” represents a pulse pressure value. Since the actual pulse pressure of the subject cannot be determined from one point of instantaneous blood pressure, the pulse pressure value PP is assumed to be a predetermined value in the present embodiment.

  That is, in the present embodiment, the pulse pressure value PP is multiplied by the ratio of the difference (Δv) between the maximum value of the reference pulse wave and the value at the time when the instantaneous blood pressure is detected to the amplitude value ΔV of the reference pulse wave. The maximum blood pressure of the measurement subject is estimated by adding the value to the instantaneous blood pressure value. Then, the estimated systolic blood pressure is determined as the upper limit value of the control range.

  Therefore, the value of the pulse pressure value PP is preferably the maximum value of the assumed pulse pressure. Here, 150 mmHg which is the maximum value of the pulse pressure in many samples is used. As a result, from Equation (1), the maximum value Pc_max of the control range is the maximum blood pressure when the pulse pressure of the subject is assumed to be 150 mmHg. The minimum value Pc_min of the control range is the minimum blood pressure when the subject's pulse pressure is assumed to be 150 mmHg. However, the upper limit of the maximum value Pc_max is set to 300 mmHg, and when this value is exceeded, the maximum value Pc_max is preferably set to 300 mmHg. Similarly, the lower limit of the minimum value Pc_min is set to 40 mmHg, and when it is less than this value, Pc_min is preferably set to 40 mmHg.

  As described above, by determining the predetermined pulse pressure value PP as the maximum value of the assumed pulse pressure, an appropriate control range can be determined even for a measurement subject having a high pulse pressure.

  In the present embodiment, the instantaneous blood pressure value is obtained by rapidly pressurizing the cuff 20, but may be obtained by rapidly depressurizing.

(About control target value detection processing)
Here, a case where the control target value is detected while the cuff pressure is being reduced will be described. It may be detected during pressurization.

  FIG. 10 is a flowchart showing a control target value detection process in the embodiment of the present invention.

  Referring to FIG. 10, detection processing unit 104 initializes an area in memory unit 42 that stores the maximum value of arterial volume change signal (PGac) and the arterial volume signal (PGdc) and cuff pressure at that time. (Step ST41). In the following processing, the maximum value of the arterial volume change signal is updated at any time. Therefore, the value until the final value is finally determined is referred to as “volume change temporary maximum value”.

  Next, the detection processing unit 104 sets the cuff pressure to the maximum value Pc_max of the control range (step ST42), and starts the pressure reduction at the slow speed of the cuff 20 (step ST43).

  At the stage where the cuff 20 is decompressed, the detection processing unit 104 detects the arterial volume signal and the arterial volume change signal based on the volume pulse wave signal input from the arterial volume detection circuit 74A (step ST44).

  The detection processing unit 104 determines whether or not the value of the arterial volume change signal is greater than or equal to the volume change temporary maximum value stored in the memory unit 42 (step ST45). When it is determined that the value of the arterial volume change signal is greater than or equal to the volume change temporary maximum value (“≧ volume change temporary maximum value” in step ST45), the process proceeds to step ST46. On the other hand, when it is determined that the arterial volume change signal is smaller than the volume change temporary maximum value (“<volume change temporary maximum value” in step ST45), the process proceeds to step ST47.

  In step ST46, the detection processing unit 104 updates the volume change temporary maximum value, and overwrite-records the cuff pressure and the value of the arterial volume signal at that time. When this process ends, the process moves to a step ST47.

  In step ST47, the detection processing unit 104 determines whether or not the detected cuff pressure has reached the lower limit value Pc_min of the control range. When it is determined that the cuff pressure has not reached the lower limit value Pc_min (“> Pc_min” in step ST47), the process returns to step ST43, and the above processing is repeated. On the other hand, when it is determined that the cuff pressure has reached the lower limit value Pc_min (“≦ Pc_min” in step ST47), the process proceeds to step ST48.

  In step ST48, the detection processing unit 104 determines the volume change temporary maximum value finally recorded in step ST46 as the volume change maximum value, and detects the arterial volume signal detected when the volume change maximum value is detected. Is determined as the control target value V0, and the cuff pressure detected at that time is determined as the control initial cuff pressure PC0. That is, the arterial volume value and the cuff pressure recorded in step ST46 are determined as V0 and PC0, respectively.

The control target value detection process is thus completed.
FIG. 11 is a graph showing the state of cuff pressure control from the determination of the control range to the determination of V0 in the embodiment of the present invention. In FIG. 11, the cuff pressure and the virtual blood pressure of the measurement subject are shown along the time axis. When the measurement is started, the cuff pressure is instantly controlled to increase until the occlusion start point is detected from 0 mmHg within one heartbeat (cuff pressure = Bp_inst). When the control range is determined, the cuff pressure is set to the upper limit value Pc_max of the control range and gradually reduced to the lower limit value Pc_min. In the figure, the time required to determine the control range is indicated by time TA, and the time required for V0 detection is indicated by time TB. According to the present embodiment, the time TA is about 0.4 to 0.6 seconds. Thus, since the control range can be determined instantaneously, the control range can be made narrower than before. As a result, it is possible to shorten the time (TA + TB) required to start continuous blood pressure measurement while maintaining the V0 detection accuracy.

<About data structure>
Next, the data structure of each measurement data stored in the flash memory 43 by the above blood pressure measurement process will be described.

FIG. 12 is a diagram showing a data structure of each measurement data in the embodiment of the present invention.
Referring to FIG. 12A, each of measurement data 80 stored in flash memory 43 includes three fields 81 to 83 of “ID information”, “recording date / time”, and “blood pressure information” as an example. The contents of each field are outlined. The “ID information” field 81 stores an identification number for specifying each measurement data, and the “recording date” field 82 is each measurement data timed by the time measuring unit 45. Stores information such as the measurement start date and time and the measurement period. The “blood pressure information” field 83 stores time-series blood pressure data, that is, pulse wave waveform data.

  FIG. 12B is a diagram illustrating a data structure of the blood pressure information field 83 included in the measurement data. Referring to FIG. 12B, the blood pressure information field 83 has a region 831 for storing “time data” and a region 832 for storing “blood pressure data”.

  In a region 831, a plurality of time data 1, 2, 3,..., N corresponding to the sampling period are stored. The region 832 stores blood pressure data BD (1), BD (2),..., BD (n) in association with each time data of the region 831. In the region 832, a region indicated by “−” indicates that the difference between the arterial volume value and the target value at that time exceeds a predetermined value and is not recorded as blood pressure.

  In addition, a storage form is not limited to such an example, Time (time) and blood pressure should just be matched and memorize | stored.

  As described above, the blood pressure information is stored in the flash memory 43. The blood pressure information may include an index that can be calculated from the pulse wave, such as the pulse rate and AI, in addition to the blood pressure values such as the maximum blood pressure, the minimum blood pressure, and the average blood pressure.

<Modification>
Subsequently, another example of calculating the upper limit value Pc_max and the lower limit value Pc_min of the control range will be described as a modification of the embodiment of the present invention.

  The above-described calculation method assumes that the subject's pulse pressure (pulse pressure value PP) is 150 mmHg, and therefore is an unnecessarily high upper limit for subjects whose pulse pressure is lower than 150. In order to solve this problem, in this modification, the cuff 20 is pressurized twice to detect two instantaneous blood pressure values (BP_inst1 and BP_inst2), and at the same time, the level of the reference pulse wave (Lp_inst1 and Lp_inst2) at that time ) Is detected. Then, the pulse pressure (pulse pressure value PP) of the subject is estimated according to the following formula 3, and the estimated pulse pressure value PP is substituted into the above formulas 1 and 2, so that the upper limit value Pc_max and the lower limit of the control range are calculated. A value Pc_min is calculated.

  By this processing, it is possible to set the cuff pressure control range according to the pulse pressure of the subject. The reason why the pulse pressure of the subject can be estimated from Equation 3 will be described with reference to FIG. FIG. 13 is a diagram showing the relationship between the arterial volume waveform (reference pulse wave) and the blood pressure waveform. FIG. 13A shows the arterial volume waveform, and FIG. 13B shows the blood pressure waveform.

  As shown in FIG. 13, the blood pressure waveform and the arterial volume waveform are in a similar relationship. Therefore, the ratio of the difference between the instantaneous blood pressure values at two points (BP_inst1-BP_inst2) and the difference between the systolic blood pressure and the systolic blood pressure (SYS-DIA, ie, pulse pressure (PP)) is the pulse at the two occlusion start points. The fact that the difference between the wave level difference (Lp_inst1−Lp_inst2) and the difference in pulse wave level at the time of systolic blood pressure / minimum blood pressure (Lp_sys−Lp_dia) is used is used.

  FIG. 14 is a flowchart showing control range determination processing in a modification of the embodiment of the present invention. In addition, the same step number is attached | subjected about the process similar to the flowchart of FIG. Therefore, description thereof will not be repeated here.

  Referring to FIG. 14, when the instantaneous blood pressure value (BP_inst) and the level of the reference pulse wave (Lp_inst) at that time are detected in step ST31, calculation unit 114 has detected two occlusion start points. It is determined whether or not (step ST62). If the condition is not satisfied (NO in step ST62), the process returns to step ST21, and the process for detecting the second closing start point is executed again.

  On the other hand, when the condition is satisfied, that is, when it is determined that two occlusion start points have been detected (YES in step ST62), the processes of steps ST32 to ST34 described above are executed. When the pulse wave level at the maximum blood pressure (Lp_sys) and the pulse wave level at the minimum blood pressure (Lp_dia) are determined in step ST34, the calculation unit 114 estimates the pulse pressure of the measurement subject according to the above equation (3). (Step ST65). When the pulse pressure is estimated, the upper limit value Pc_max and the lower limit value Pc_min of the control range are calculated by substituting the estimated pulse pressure value into “PP” in the above formulas (1) and (2) (step ST66). .

  As described above, according to the present modification, the pulse pressure of the measurement subject is estimated using the similarity between the arterial volume waveform and the blood pressure waveform. Thereby, if it is a to-be-measured person with a small pulse pressure, the time which V0 detection requires can further be shortened. In this modification, the control range determination process takes more time than in the above embodiment because two occlusion start points are detected, but it still takes about 1 second, and as a result (the pulse pressure must be high). For example, it is possible to shorten the time required to start continuous blood pressure measurement compared to the above embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the relationship between the characteristic of an arterial volume signal and the systolic blood pressure when cuff pressure is pressurized instantaneously. It is a figure which shows the relationship between the characteristic of an arterial volume signal when the cuff pressure is pressurized instantaneously, and the minimum blood pressure. 1 is an external perspective view of a blood pressure information measurement device according to an embodiment of the present invention. It is a block diagram showing the hardware constitutions of the blood-pressure information measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the example of arrangement | positioning of each arterial volume sensor in embodiment of this invention. It is a functional block diagram which shows the function structure of the blood-pressure information measuring apparatus 1 which concerns on embodiment of this invention. It is a flowchart which shows the blood-pressure measurement process in embodiment of this invention. It is a flowchart which shows the control range determination process in embodiment of this invention. It is a figure which shows the volume level in each feature point of a reference pulse wave. It is a flowchart which shows the control target value detection process in embodiment of this invention. It is a graph which shows an example of cuff pressure control from determination of a control range to determination of V0 in an embodiment of the invention. It is a figure which shows the data structure of each measurement data in embodiment of this invention. It is a figure which shows the relationship between an arterial volume waveform (reference pulse wave) and a blood pressure waveform. It is a flowchart which shows the control range determination process in the modification of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Blood pressure information measuring device 10 Main body part, 20 cuff, 21 Air bag, 30 Air system, 31 Air tube, 32 Pressure sensor, 33 Oscillation circuit, 40 Display part, 41 Operation part, 41A Power switch, 41B Measurement switch, 41C Stop switch, 41D memory switch, 42 memory section, 43 flash memory, 44 power supply, 45 timing section, 46 interface section, 50 adjustment mechanism, 51 pump, 52 valve, 53 pump drive circuit, 54 valve drive circuit, 70A, 70B artery Volume sensor, 71A, 71B light emitting element, 72A, 72B light receiving element, 73A, 73B light emitting element drive circuit, 74A, 74B arterial volume detection circuit, 100 CPU, 102 cuff pressure acquisition unit, 103 range determination processing unit, 104 detection processing unit , 106 Servo control unit, 108 Blood pressure determination Fixed unit, 112 adjustment control unit, 114 calculation unit, 132 recording medium.

Claims (6)

A blood pressure information measuring device for measuring blood pressure information by detecting the volume of an artery,
A cuff for wrapping around a predetermined measurement site;
Adjusting means for adjusting the pressure in the cuff by pressurization and decompression;
Pressure detecting means for detecting a cuff pressure representing the pressure in the cuff;
First volume detection means for detecting a first arterial volume signal that is disposed at a predetermined position of the cuff and represents a change in the volume of the artery due to compression of the cuff;
Second volume detection means disposed upstream of the cuff and for detecting a second arterial volume signal representing a change in volume accompanying the pulsation of the artery;
Control means for performing control for measuring the blood pressure information according to a volume compensation method,
The control means includes
Servo control means for servo-controlling the adjustment means so that the volume of the artery is constant based on the first arterial volume signal;
Determination processing means for determining a control range of the cuff pressure when detecting a control target value by the servo control means based on the first and second arterial volume signals and the cuff pressure;
The determination processing means includes:
An adjustment control means for instantaneously changing the cuff pressure by controlling the adjustment means;
Based on the first and second arterial volume signals and the cuff pressure obtained in the instantaneous change period representing the control period by the adjustment control means, the systolic blood pressure and the diastolic blood pressure are estimated, the estimated systolic blood pressure and Calculating means for calculating each minimum blood pressure as an upper limit value and a lower limit value of the control range,
The control means is a detection processing means for detecting the control target value based on the first arterial volume signal by gradually changing the cuff pressure in the control range determined by the determination processing means. Further including
The blood pressure information measuring device, wherein the servo control means performs servo control so that a value of the first arterial volume signal coincides with the control target value detected by the detection processing means.   The calculating means detects blood pressure by detecting a feature point in the first arterial volume signal indicating an obstruction end point of the artery based on the first arterial volume signal and cuff pressure obtained during the instantaneous change period. A value is calculated, based on the calculated blood pressure value, the level of the second arterial volume signal at the time when the occlusion end point is detected, and a pulse pressure value representing the measured patient's pulse pressure, The blood pressure information measurement device according to claim 1, wherein the blood pressure information measuring apparatus estimates the maximum blood pressure and the minimum blood pressure.   The blood pressure information measurement device according to claim 2, wherein the adjustment control means changes within a heartbeat from a predetermined pressure value until at least the blockage end point is detected.   The blood pressure information measurement device according to claim 3, wherein the pulse pressure value is a predetermined value.   The blood pressure information measurement device according to claim 4, wherein the predetermined value is a maximum level of pulse pressure. The adjustment control means executes the cuff pressure adjustment within one heartbeat twice,
The blood pressure information measuring device according to claim 3, wherein the calculating means calculates blood pressure values for two heartbeats and estimates the pulse pressure values from the blood pressure values for the two heartbeats.

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