JP3023505B2 - Blood pressure monitoring device - Google Patents

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 propagation time exceeds the preset threshold value ΔTs of the variation of the pulse wave propagation time, 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 is a blood pressure measurement means for measuring blood pressure using a cuff.
And pulse wave transit time measurement unit for measuring pulse wave transit time
And the pulse wave propagation measured by the pulse wave propagation time measuring unit
Based on whether or not the time fluctuation exceeds a predetermined threshold
Controlling the blood pressure measuring means by means of
Control means for measurement and the relationship between blood pressure value and pulse wave transit time
Said predetermined based on the change of the subject-specific constant in
Threshold updating means for updating the threshold.
You. According to this configuration, the pulse wave transit time variation is measured.
The pulse wave transit time fluctuation is a pulse wave transit time fluctuation threshold.
The blood of the subject is determined by sequentially determining whether the
Can monitor pressure. Pulse wave transit time fluctuation exceeds threshold
Use the cuff to accurately measure the subject's blood pressure
By doing so, the burden on the subject can be minimized.
Further, according to this configuration, the blood pressure measurement by the cuff is performed.
Is updated, the threshold is updated with the subject-specific value.
The blood pressure of the subject can be monitored with higher accuracy.
Swell.

[0009] The threshold updating means may be configured to measure the blood pressure.
By the blood pressure value measured by the
At least two pairs of measured pulse transit times
Update the predetermined threshold based on the
Of the pulse wave propagation time from the two measured pulse wave propagation times
First calculating means for calculating inter-temporal variation, and the blood pressure measuring means
The difference between the two blood pressure values obtained by
Calculate subject-specific constant by dividing by propagation time difference Second
Before SL subjects and calculating means is calculating said predetermined threshold
A third act of updating the predetermined threshold by dividing by a unique constant;
And calculation means. The pulse wave propagation time
The measurement unit consists of a pulse wave sensor that detects aortic waves and peripheral blood
It has a pulse wave sensor that detects the pulse wave on the tube side, and the pulse wave
It was configured to measure the propagation time. In addition, the pulse wave transmission
The seeding time measurement unit detects the electrocardiogram R wave,
Means and a pulse wave sensor for detecting a pulse wave on the peripheral blood vessel side.
The time of the appearance of the R-wave of the electrocardiogram and the appearance of the pulse wave in the peripheral blood vessels
The difference was measured.

[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 16, the measured data BP of the blood pressure value
If there is 3, α, β, ΔTs are calculated in step 17 based on the following equation. The calculated patient-specific constants .alpha. And .beta. Are written into the memory 17 and are subsequently used to calculate the blood pressure from the pulse wave transit time T2. 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. That is, ΔT> ΔTs is satisfied.
Sudden change in the patient's blood pressure fluctuations
In step 17, α = (BP1-BP3) / (T1-T3) β = BP1-αT1 ΔTs = △ BPs / α to obtain a patient-specific constant α, thereby obtaining the pulse
The wave propagation time fluctuation threshold ΔTs is updated.

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. Further, the pulse wave transit 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 present invention, the pulse
The pulse wave transit time is measured successively, and the pulse wave transit time
Whether a sudden change in the patient's blood pressure fluctuations has occurred
To determine whether the patient has
To accurately measure the blood pressure of the elderly,
Blood pressure measurement using a cuff in such a short cycle,
Patients do not experience the pain of performing invasive blood pressure measurements
The burden on the user can be greatly reduced. In addition, the cuff
Blood pressure measurements, patient-specific constants are determined.
This updates the threshold so that the patient
Can monitor sudden changes in blood pressure fluctuations.

[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 Nishiochiai, Shinjuku-ku, Tokyo Inside Nihon Kohden Kogyo Co., Ltd. (56) References JP-A-4-367648 (JP, A) JP-A-4-200439 (JP, A) JP-A-3-505533 (JP, A) US Patent 490759 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 5/02 -5/0295 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A hand for measuring blood pressure using a cuff
Stage and the pulse wave propagation time measuring unit for measuring a pulse wave propagation time, pulse wave propagation time measured by the pulse wave propagation time measuring unit
Based on the determination of whether the fluctuation of
The blood pressure measuring means is controlled, and the blood pressure of the subject is measured by the cuff.
And a subject-specific determination of the relationship between the blood pressure value and the pulse wave transit time.
Updating the predetermined threshold based on a change in the number
Means for monitoring blood pressure. 2. The blood pressure measuring means according to claim 2, wherein said threshold value updating means is said blood pressure measuring means.
Blood pressure value measured by the pulse wave transit time measurement unit
Based on at least two pairs of measured pulse transit times
And updating the predetermined threshold value.
2. The blood pressure monitoring device according to 1. 3. The threshold value updating means calculates a pulse wave transit time variation from two measured pulse wave transit times.
And calculating the difference between the two blood pressure values obtained by the first calculating means and the blood pressure measuring means.
Divided by the difference between the two measured pulse wave transit times
A second calculating means for calculating the number, and dividing the predetermined threshold value by the calculated constant peculiar to the subject.
3. The blood pressure monitoring device according to claim 2 , further comprising: third operation means for updating the predetermined threshold value.
Place. 4. The pulse wave transit time measuring section detects an aortic wave.
Pulse wave sensor for detecting and pulse wave for peripheral blood vessels
Has a pulse wave sensor and measures the time it takes for the pulse wave to travel through the artery
4. The method according to claim 1, wherein
The blood pressure monitoring device according to any one of the preceding claims. 5. The pulse wave transit time measuring section comprises an electrocardiogram R wave.
R-wave detecting means for detecting a pulse and a pulse wave on the peripheral blood vessel side
With a pulse wave sensor to detect the appearance and peripheral
Measuring the time difference between appearance of pulse waves in blood vessels
A blood pressure monitoring device according to any one of claims 1 to 3.
Place.