JPH1066681A - Blood pressure monitoring device - Google Patents

Abstract

(57) [Summary] [Purpose] To enable continuous and accurate blood pressure monitoring without imposing a burden on the patient. A CPU obtains a pulse wave transit time from a pulse wave obtained from a photoelectric pulse wave sensor and a reference point obtained from a time interval detecting reference point detector, and a fluctuation of the pulse wave transit time is larger than a threshold value. At times, the pressure pump 4 and the exhaust valve 3 are controlled to measure the blood pressure using the cuff 2. CPU1
When blood pressure measurement using the cuff 2 was performed, a constant unique to the patient was first obtained, and the threshold was changed according to the constant. Also, when the key 14 is input, the CPU 1
Performed the blood pressure measurement using the cuff 2 and further changed the threshold value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blood pressure monitoring device in a field where continuous blood pressure monitoring of a patient is required in an operating room, an intensive care unit, an emergency room, an artificial dialysis room, and the like.
In particular, the present invention relates to an apparatus for monitoring blood pressure using a pulse wave transit time.

[0002]

2. Description of the Related Art Conventionally, in order to continuously monitor the blood pressure of a patient and monitor the blood pressure, a method of measuring a non-invasive blood pressure by an oscillometric method by wrapping a cuff around a patient's upper arm or the like, There is a method of performing invasive blood pressure measurement by puncturing an artery of the subject.

[0003]

In non-invasive blood pressure measurement using a cuff, a sudden change in blood pressure due to a shock may be overlooked when the measurement cycle is long (for example, at intervals of 5 minutes or more) in regular measurement. As a countermeasure, if the measurement cycle is shortened to, for example, one minute, a load is applied to the blood vessel in the portion where the cuff is wound, and problems such as occurrence of internal bleeding occur. Further, in the case of the regular measurement, the patient is burdened by the excessively frequent tightening of the cuff, which causes a sleep disorder or the like. On the other hand, the invasive measurement has a problem that the invasion causes a mental burden to the patient and causes a problem such as infection, and also requires more labor than the non-invasive blood pressure measurement, and thus burdens the staff.

The present invention has been proposed to solve such problems of the conventional technology, and provides a blood pressure monitoring device capable of continuously and safely monitoring blood pressure without imposing a burden on a patient. The purpose is to:

[0005]

The basic concept of the present invention will be described below. As one of non-invasive sphygmomanometers, there is known a sphygmomanometer that measures a blood pressure using a pulse wave propagation velocity (a pulse wave propagation time at a certain distance). The principle by which the blood pressure can be measured from the pulse wave propagation velocity is as follows. First, the pulse wave transit time will be described. As shown in FIG. 3, a singular point of a pulse wave appears on the peripheral blood vessel side such as a finger or an ear later in time than a singular point of an aortic wave. This delay time is the pulse wave propagation time.
The pulse wave velocity corresponding to the pulse wave propagation time at a certain distance is expressed as a function of the bulk modulus of the blood vessel. As the blood pressure increases, the bulk modulus of the blood vessels increases, the blood vessel walls become harder and the propagation speed increases. Therefore, the blood pressure fluctuation can be obtained from the pulse wave propagation velocity.

A sphygmomanometer using the pulse wave transit time needs to measure the blood pressure by another method such as using a cuff, and to perform calibration by referring to the measurement result. In this calibration, for example, the blood pressure and the pulse wave transit time at rest and during exercise load are measured. Here, assuming that the resting blood pressure and pulse wave transit time are P1 and T1, respectively, the blood pressure and pulse wave transit time under exercise load are P2 and T2, respectively, and unique constants that differ depending on the subject are α and β. , P2
Is represented by P1 = αT1 + β P2 = αT2 + β. Therefore, by measuring P1, T1, P2, and T2, α and β can be calculated from these two equations. Once α and β have been obtained, only the pulse wave propagation time is measured thereafter. Then, the blood pressure of the subject can be measured. In measuring two different blood pressure values, the two blood pressure values need not be measured at rest and during exercise load, but may be measured when different blood pressure values appear.

On the other hand, even if the pulse wave transit time is simply measured successively, the blood pressure fluctuation of the subject can be monitored. In this case, when the variation ΔT of the pulse wave transit time exceeds a preset threshold value ΔTs of the pulse transit time variation, it is determined that a sudden change has occurred in the blood pressure variation of the subject, and the cuff is used at that time. The non-invasive blood pressure measurement may be accurately performed. By doing so, the burden on the subject can be greatly reduced without imposing a burden on the subject as in the case where the blood pressure measurement is continuously performed by the cuff at a constant cycle.

A blood pressure monitoring device according to the present invention based on this measurement principle comprises: a blood pressure measuring means for measuring blood pressure using a cuff; an instruction means for instructing the blood pressure measuring means to start measurement in response to an external operation; A memory that stores a pulse wave propagation time variation threshold and a blood pressure variation threshold that are input from the outside, a time interval detection reference point detection unit that detects a time interval detection reference point on a pulse wave on the aorta side of a living body, Pulse wave propagation based on the respective detection outputs of the pulse wave detection means for detecting a pulse wave on the peripheral blood vessel side appearing later than the pulse wave on the aorta side, and the time interval detection reference point detection means and the pulse wave detection means A pulse wave transit time measuring unit for measuring time, first calculating means for calculating a pulse wave transit time variation from the measured two pulse wave transit times, and a difference between the two blood pressure values obtained by the blood pressure measuring means. Was measured A second calculating means for calculating a subject-specific constant by dividing by a difference between two pulse wave transit times, and a blood pressure variation threshold read out from the memory, and dividing the calculated subject-specific constant by a calculated subject-specific constant. Third calculating means for updating the pulse wave transit time variation threshold value, first control means for controlling updating of the pulse wave transit time variation threshold value, and the calculated pulse wave transit time variation amount is read from the memory. Determining means for determining whether or not a pulse wave transit time variation threshold has been exceeded; and controlling the blood pressure measuring means based on either the output of the determining means or the instruction of the instruction means, and measuring the blood pressure of the subject by the cuff. And a second control means for performing the following.

According to the above configuration, the pulse wave transit time fluctuation is measured, and it is sequentially determined whether or not the pulse wave transit time fluctuation exceeds the pulse wave transit time fluctuation threshold.
Monitor the blood pressure of the subject. When the pulse wave transit time variation exceeds the pulse wave transit time variation threshold, if the blood pressure of the subject is accurately measured using the cuff, the burden on the subject can be reduced as much as possible. Furthermore, according to this configuration, when the blood pressure measurement is performed by the cuff, the pulse wave transit time variation threshold value is updated, and the threshold value becomes a value unique to the subject, so that the blood pressure of the subject can be monitored with higher accuracy. Become like The blood pressure measurement by the cuff is started when the pulse wave transit time fluctuation exceeds the pulse wave transit time fluctuation threshold or when an instruction is given from the instruction means.

[0010]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a blood pressure monitoring device according to the present invention. In this figure,
The cuff 2 is configured to be worn on a patient's upper arm or finger, and the inside thereof is opened or closed by the exhaust valve 3 to the atmosphere. Air is supplied to the cuff 2 by a pressure pump 4. A pressure sensor 5 is attached to the cuff main body, and a sensor output is detected by a cuff pressure detector 6. The output of the cuff pressure detector 6 is converted into a digital signal by an A / D converter 7 and is taken into a CPU (Central Processing Unit) 1.

The time interval detection reference point detector 8 detects the point in time when the aortic pressure reaches the bottom value almost simultaneously with the generation of the R wave of the electrocardiogram. The output of this detector is A / A
The signal is converted into a digital signal by the D
It is taken into 1. This time interval detection reference point detector 8
Can be composed of an electrode mounted on the chest of a patient and an electrocardiogram R-wave detector to which the electrode is connected.
Further, the time interval detection reference point detecting unit 8 can be constituted by a photoelectric pulse wave sensor for detecting a pulse wave of the aorta, or a pressure pulse wave sensor and a pulse wave detecting unit to which this sensor is connected.

On the other hand, the photoelectric pulse wave sensor 10 is attached to, for example, a finger of a patient, and measures a pulse wave on a peripheral blood vessel side. The output of the sensor 10 is sent to the pulse wave detecting unit 11 so that the pulse wave at the patient's wearing site is detected. Pulse wave detector 1
1 is converted into a digital signal by the A / D converter 12 and taken into the CPU 1.

The key 14 is depressed when performing blood pressure measurement using the cuff 2 by manual operation or when updating the pulse wave propagation time fluctuation threshold value ΔTs. From the input means 13, an initial pulse wave transit time variation threshold △ Ts and a blood pressure variation threshold △ BPs are input.

The CPU 1 includes A / D converters 7, 9, 12,
The processing program is executed based on the signal given from the key 14, and necessary control signals are output to the exhaust valve 3, the pressurizing pump 4, etc., and the processing result is output to the display 15. A memory (ROM) 16 connected to the CPU 1 stores a processing program, and a memory (RAM) 17 stores data of a processing process. The CPU 1 constitutes the pulse wave transit time measuring unit, the calculating means, the determining means, the control means, the first to third calculating means, and the first and second control means in claim 1. The key 14 is an instruction means.

Next, the operation of the present apparatus will be described with reference to the flowchart of FIG. First, the initial pulse wave transit time variation threshold △ Ts and the blood pressure variation threshold △ BPs are input from the input means 13 and written into the memory 17 in step S11. Subsequently, in step S12, the presence or absence of the input of the key 14 is determined. If there is the key input, the exhaust valve 3 and the pressurizing pump 4 are controlled by the CPU 1 in step S13, and the measurement of the blood pressure of the patient using the cuff 2 is performed. Done. At this time,
The data fetched from the A / D converter 7 is processed inside the CPU 1, and the blood pressure value BP1 measured by the oscillometric method is written to the memory 17. Subsequently, based on the data taken into the CPU 1 from the A / D converters 9 and 12 in step S14, a pulse wave is generated on the peripheral blood vessel side from the time when the aortic pressure reaches the bottom value almost simultaneously with the generation of the R wave of the electrocardiogram. Pulse wave transit time T1 corresponding to the time to reach the value
Is measured and written to the memory 17. Next, at step S15, the blood pressure value BP1 is displayed. Subsequently, in step S16, it is determined whether or not there is blood pressure value measurement data BP3. If there is no data, in step S19, blood pressure value BP3 is determined.
After writing 1 in the memory 17 as BP3 and writing the pulse wave propagation time T1 in the memory 17 as T3, the process returns to step S12.

In step S16, measured data B of the blood pressure value
If P3 is present, α, β, ΔTs are calculated based on the following equation. α = (BP1−BP3) / (T1−T3) β = BP1−αT1 ΔTs = ΔBPs / α The calculated patient-specific constants α and β are written into the memory 17 and then the pulse wave propagation time T2 Is used to calculate blood pressure from Further, the pulse wave transit time variation threshold ΔTs is updated to the calculated value in step S 18 and written to the memory 17. Subsequently, in step S19, the blood pressure value BP1 is written to the memory 17 as BP3, and the pulse wave propagation time T1 is written to the memory 17 as T3, and the process returns to step S12.

In step S12, the presence or absence of a key input is determined again. If there is no key input, the pulse wave propagation time T2 is measured based on the data from the A / D converters 9 and 12 in step S20. The value is written to the memory 17. Subsequently, in step S21, the blood pressure value P is calculated by the following equation using the measured pulse wave propagation time T2 and the constants α and β obtained in step S17, and is written into the memory 17. P = αT2 + β In step S22, the measured blood pressure value P is displayed on the display 15. Subsequently, in step S23, it is determined whether or not there is data on the previously measured pulse wave propagation time T3. If there is no data, the process returns to step S12. If there is data, T2 and T3 are used in step S24. The pulse wave transit time variation ΔT is calculated based on the following equation. ΔT = T2−T3 Subsequently, in step S25, the pulse wave transit time fluctuation amount obtained in step S24 ΔT is the pulse wave transit time fluctuation threshold value Δ
It is determined whether or not Ts is exceeded, that is, whether or not the equation of △ T> △ Ts is satisfied. If △ T> △ Ts is not satisfied, the process returns to step S12 and the series of processing is repeated again.

On the other hand, in step S25, ΔT> ΔT
If it is determined that s is satisfied, it is considered that there is a sudden change in the blood pressure fluctuation of the patient due to shock or the like, and step S1 is performed.
The process shifts to 3. In step S13, the blood pressure is measured using the cuff 2 to cope with a sudden change in the blood pressure of the patient, and the measured value BP1 is written into the memory 17. Subsequently, in step S14, the pulse wave propagation time T1 is measured again based on the data from the A / D converters 9 and 12, and written into the memory 17. In step S15, the blood pressure value BP1 accurately measured in step S13 is displayed on the display 15, and thereafter, the process proceeds to step S16 and the same processing is repeated.

Thus, the pulse wave transit time is always measured,
The pulse wave transit time variation ΔT is the pulse wave transit time variation threshold ΔT
By judging whether or not s has been exceeded, a sudden change in the blood pressure fluctuation of the patient is monitored, and the blood pressure measurement using the cuff 2 is accurately performed when the blood pressure fluctuation suddenly changes. Can greatly reduce the burden on

Further, in this embodiment, the pulse wave transit time variation threshold ΔTs can be updated, so that a sudden change in the blood pressure variation of the patient can be monitored more accurately. Furthermore, the electroencephalogram propagation time measurement processing may be performed for each beat, or may be performed for a fixed time or a fixed number of beats to obtain an average value. By obtaining the average value, the influence of irregularly generated noise can be eliminated and accurate measurement can be performed.

[0021]

As described above, according to the first aspect of the present invention, the pulse wave transit time is sequentially measured to determine whether the pulse wave transit time variation exceeds the pulse wave transit time variation threshold. By determining whether or not a sudden change has occurred in the patient's blood pressure fluctuation, and at the time of sudden change in blood pressure, so as to accurately measure the patient's blood pressure using a cuff, using the cuff in a short cycle as in the past As in the case of performing blood pressure measurement or invasive blood pressure measurement, pain does not occur, and the burden on the patient can be significantly reduced. Further, when the blood pressure is measured by the cuff, a constant unique to the patient is obtained, and the threshold value for the pulse wave transit time fluctuation is updated, so that a sudden change in the blood pressure fluctuation of the patient can be monitored more accurately. Furthermore, according to the present invention, the blood pressure measurement means has an instruction means for instructing the blood pressure measurement means to start measurement in response to an external operation. By instructing the start of the measurement by the cuff via, the constant unique to the patient is obtained, and the threshold value for the pulse wave transit time variation can be changed accordingly. Since the threshold is a value corresponding to the patient, a sudden change in blood pressure fluctuation can be accurately detected from the beginning of patient monitoring. In addition, the measurer can instruct the cuff measurement not only before the monitoring is started but also at a desired time. Therefore, the measurer can calibrate the pulse wave transit time fluctuation threshold value when desired.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a blood pressure monitoring device according to the present invention.

FIG. 2 is an operation flowchart for explaining the operation of the blood pressure monitoring device of FIG. 1;

FIG. 3 is a waveform diagram for explaining a pulse wave transit time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 Cuff 3 Exhaust valve 4 Pressure pump 5 Pressure sensor 6 Cuff pressure detector 7, 9, 12 A / D converter 8 Time interval detection reference point detector 10 Photoelectric pulse wave sensor 11 Pulse wave detector 13 Input means 14 key 15 display 16 memory (ROM) 17 memory (RAM)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Eihiro Hosaka 1-31-4 Nishi-Ochiai, Shinjuku-ku, Tokyo Japan Photovoltaic Industry Co., Ltd.

Claims (1)

[Claims] 1. A blood pressure measuring means for measuring a blood pressure using a cuff; an instruction means for instructing the blood pressure measuring means to start measurement in response to an external operation; A memory for storing a threshold value and a blood pressure variation threshold value; a time interval detection reference point detecting means for detecting a time interval detection reference point on a pulse wave on the aorta side of a living body; a peripheral appearing later than the aortic pulse wave A pulse wave detecting means for detecting a pulse wave on the blood vessel side, a pulse wave transit time measuring unit for measuring a pulse wave transit time based on respective detection outputs of the time interval detection reference point detecting means and the pulse wave detecting means. A first calculating means for calculating a pulse wave transit time variation from the measured two pulse wave transit times; and a difference between the two blood pressure values obtained by the blood pressure measuring means, the difference between the two measured pulse wave transit times. Divided by the difference A second calculating means for calculating the number, and a third calculation for updating the pulse wave transit time variation threshold in the memory by dividing the blood pressure variation threshold read from the memory by the calculated subject-specific constant. Means, first control means for controlling updating of the pulse wave transit time variation threshold, and determining whether the calculated pulse wave transit time variation exceeds the pulse wave transit time variation threshold read from the memory. Determining means for controlling the blood pressure measuring means based on one of the output of the determining means and the instruction of the instruction means, and a second control means for measuring the blood pressure of the subject by the cuff. Blood pressure monitoring device.