JP4713245B2 - Blood pressure monitoring device - Google Patents

Description

  The present invention relates to a blood pressure monitoring apparatus for continuously monitoring blood pressure values in a non-invasive manner.

In operating rooms, intensive care units, etc., continuous blood pressure monitoring of the patient may be necessary. Conventionally, blood pressure estimation based on pulse wave propagation time is known as a technique for monitoring blood pressure non-invasively and continuously.
This is the time required for the pulse wave to propagate between two points of the living body (pulse wave propagation time) or the pulse wave velocity obtained by dividing the blood vessel length between these two points by the pulse wave propagation time, This is based on the fact that there is a correlation with the blood pressure value. Then, for example, the pulse wave propagation time is continuously measured, and an estimated blood pressure value is continuously calculated by applying the pulse wave propagation time to a calculation formula having a previously calibrated coefficient, and the value is monitored (see, for example, Patent Document 1).

  However, in order to measure the pulse wave propagation time, it is necessary to measure the pulse wave at different sites, which takes time. In addition, it may be difficult to attach sensors or cuffs for measuring pulse waves at two locations. Therefore, as described in Patent Document 1, the pulse wave propagation time is calculated using an electrocardiogram (ECG) that is normally measured by the biological information monitor device and a pulse wave measured at one predetermined part (for example, fingertip) of the living body. It is common to calculate.

JP 10-66681 A (paragraphs 0005 to 0007)

  However, there is a problem that the measurement accuracy is lowered as a demerit of using ECG for calculating the pulse wave propagation time. That is, ECG is not a pulse wave but a signal representing a change in the electrical state of the heart. Then, since there is a time difference (pre-ejection period) from when the electrical state change occurs until the heart actually contracts and a pulse wave is generated, the time when ECG feature points were observed was calculated as the starting point. The pulse wave propagation time includes an error attributable to the previous ejection period.

  This error can be easily corrected if the pre-ejection period is constant, but there are individual differences in the pre-ejection period, and even the same person can change depending on the situation at that time. Therefore, there is a limit to the accuracy improvement by correction.

  In the blood pressure monitoring device, when the blood pressure value continuously calculated based on the pulse wave propagation time is abnormal, the blood pressure value is measured more accurately by using a cuff, for example, and the abnormal blood pressure value is detected there. When a value is detected, control is performed such that an alarm is output.

  Blood pressure measurement using a cuff has been established as a non-invasive method for measuring blood pressure, and is effective for automatically obtaining a reliable blood pressure value. However, since it involves blood pumping, frequent implementation leads to an increase in the burden on the patient and is not desirable. Therefore, it is important to accurately calculate the estimated blood pressure value based on the pulse wave propagation time calculated from the ECG and the pulse wave observed at one point.

  The present invention has been made in view of the above-described problems of the prior art, and enables blood pressure values to be accurately estimated in a blood pressure monitoring apparatus that continuously estimates blood pressure values based on pulse wave propagation time. For the purpose.

  That is, the gist of the present invention is that a blood pressure measurement unit that measures blood pressure by a predetermined method, a pulse wave acquisition unit that acquires a pulse wave at a predetermined part of a living body, and the pulse wave and a part different from an electrocardiogram or a predetermined part A pulse wave propagation time calculating means for calculating a pulse wave propagation time from the pulse wave acquired in step, an estimated blood pressure value calculating means for calculating an estimated blood pressure value by applying the pulse wave propagation time to a predetermined calculation formula, Acceleration pulse wave calculating means for calculating an acceleration pulse wave from a pulse wave, waveform parameter calculating means for calculating a predetermined waveform parameter from a waveform included in the acceleration pulse wave, and calibration of a calculation formula using a measurement value by a blood pressure measurement unit A blood pressure monitoring apparatus, wherein the calibration means performs calibration after correcting the calibration amount applied when the fluctuation amount of the waveform parameter exceeds a predetermined amount, and when the waveform parameter fluctuation amount exceeds the predetermined amount. Exist.

  With such a configuration, according to the present invention, the calculation formula is calculated by taking into account the fluctuation amount of the waveform parameter obtained from the acceleration pulse wave, which reflects the functional state of the blood vessel, in the calibration of the calculation formula of the estimated blood pressure value. As a result, the accuracy of the estimated blood pressure value can be improved.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings.
FIG. 1 is a block diagram illustrating a functional configuration example of a biological information monitoring apparatus as a blood pressure monitoring apparatus according to an embodiment of the present invention.
In the figure, the cuff 10 has a belt-like form and incorporates a rubber sac that expands and contracts by air supply and exhaust by a pump 14. The cuff 10 is usually attached to one of the patient's limbs, typically the upper arm. The pressure sensor 12 detects a change in pressure applied to the gas filled in the rubber sac in the cuff 10, converts the pressure signal into an electric signal, and outputs it to the control unit 100.

  The electrocardiogram electrode 20 is composed of a plurality of electrodes, is attached to a predetermined position on the chest of the patient, and outputs an induced waveform to the control unit 100 as an electrocardiogram signal (ECG). The finger sensor 30 is a so-called pulse oximeter that optically detects the oxygen saturation (SPO2) and the fingertip volume pulse wave and outputs them to the control unit 100. Utilizing the fact that the light absorbance of hemoglobin differs depending on whether it is associated with oxygen, and the light absorbance also varies depending on the wavelength of light, in general, oxygen saturation is determined using two wavelengths of red light and infrared light. taking measurement. In addition, since the AC component of the transmitted light or reflected light changes according to the blood flow, this AC component is detected as an optical fingertip volume pulse wave (PTG: photoplethysmograph).

  The other sensors 40 are sensors for detecting other biological information such as patient breathing and body temperature, and one or more sensors 40 are connected to the control unit 100 as necessary. Since the other sensors 40 are not directly related to the blood pressure monitoring operation in the present embodiment, no further explanation will be given.

  The operation unit 50 is a man-machine interface for a user (measurement person) to input various settings, information about the subject, and give instructions to the biological information monitoring apparatus. Generally, the operation unit 50 is configured by appropriately combining a keyboard, a mouse, a button, a switch, a dial, a touch panel, and the like.

  The printer 60 and the display unit 70 are typical output devices, and visually output the device status, measurement results, and the like. The external interface (I / F) 80 is typically a network interface, a serial interface (USB, IEEE 1394, etc.), a modem, and the like, and is provided to communicate with an external device connected via the network or directly. It is done.

  The storage unit 90 is typically a hard disk drive, and records programs and various data for controlling the operation of the biological information monitoring apparatus, measurement results, patient personal information, and the like. The storage unit 90 may include at least one type of other storage device, for example, a device that reads from and writes to a writable removable medium such as a memory card or an optical disk.

  The control unit 100 controls the operation of the entire biological information monitor apparatus. The control unit 100 includes, for example, a CPU and a RAM, and loads a control program stored in the storage unit 90 into the RAM and executes it by the CPU, thereby controlling each unit and including a blood pressure monitoring operation described later. Realize the process. Note that it is not necessary to execute all processing by software by the CPU. For example, signal processing such as A / D conversion and filtering of signals input from various sensors is shared by a DSP or dedicated hardware. It is possible to use the configuration of

Hereinafter, the blood pressure monitoring operation in the biological information monitoring apparatus of the present embodiment will be described.
The biological information monitoring apparatus according to the present embodiment continuously calculates the pulse wave velocity using the ECG and the fingertip volume pulse wave, and continuously calculates the estimated blood pressure value by applying a calculation formula having a coefficient in advance. It is common with the prior art in the point of calculating and determining the necessity of blood pressure measurement by the cuff using the estimated blood pressure value.

  However, in this embodiment, the abnormality detection accuracy in continuous blood pressure monitoring is improved by determining that blood pressure measurement with a cuff is necessary only when other conditions are satisfied in addition to the estimated blood pressure value. As another condition, the present embodiment uses a parameter value obtained from the acceleration pulse wave.

  The acceleration pulse wave is obtained by differentiating the pulse wave twice in time, and has characteristic a wave to e wave as shown in FIG. The a wave and the b wave represent the systolic anterior component, the c wave and the d wave represent the posterior systolic component, and the e wave represents the diastolic component, respectively. Finger plethysmogram (acceleration pulse wave), blood pressure, vol. 10, no. 6, 2003, pp. 54-60)).

  According to Iketani et al., The systolic anterior component reflects the driving pressure wave generated by the ejection of blood due to the contraction of the heart, and the posterior systolic component propagates the driving pressure wave to the periphery and returns as a reflected wave. This is a re-rising pressure wave that overlaps with the driving pressure wave. Therefore, it can be considered that the anterior systolic component represents the state on the heart (central) side, and the posterior systolic component represents the distal side state.

  Therefore, in this embodiment, at least one of the systolic anterior component or the posterior systolic component fluctuated beyond a predetermined amount from the value of the anterior systolic component or the posterior systolic component when the blood pressure was measured last time using the cuff. This was adopted as another condition described above. In other words, when changes in the central or peripheral side are shown in addition to changes in the estimated blood pressure value, only the estimated blood pressure value fluctuates, or only changes in the central or peripheral side are shown It can be determined that there is a high possibility that the blood pressure actually fluctuates.

  In the present embodiment, the wave height ratio b / a with respect to the a wave is used as a parameter indicating the state on the central side, and the wave height ratio d / a with respect to the a wave is used as a parameter indicating the state on the distal side. Here, the reason for the ratio to the wave height of the a-wave is to perform a comparison between parameters obtained from acceleration pulse waves for which no strict calibration exists, and corresponds to a kind of normalization.

Based on the above, the blood pressure monitoring operation of the biological information monitoring apparatus according to the present embodiment will be described with reference to the flowchart of FIG.
First, in step S101, acquisition of ECG and pulse wave is started. In addition, as an initialization process, initial measurement of blood pressure using a cuff, initial values of acceleration pulse wave parameters and initial values of estimated blood pressure values are calculated in the same manner as described below, and stored in the storage unit 90. Keep it. Thereafter, the acceleration pulse wave process (steps S111 to S115) and the blood pressure estimation process based on the pulse wave velocity (steps S121 to S125) are processed in parallel.

  In step S <b> 111, the control unit 100 calculates an acceleration pulse wave from the fingertip photoelectric volume pulse wave from the finger sensor 30. In step S113, parameters relating to the systolic anterior component and the posterior systolic component, in this embodiment, the crest ratios b / a and d / a are obtained based on the a to d waves included in one beat of the acceleration pulse wave. .

In step S115, the control unit 100 calculates a fluctuation amount from the obtained parameter value and the value measured at the time of the previous cuff blood pressure measurement, and checks whether it is abnormal. For example,
D1 (%) = 1− {b / a (current)} / {b / a (ref)} × 100
D2 (%) = 1− {d / a (current)} / {d / a (ref)} × 100
age,
| D1 |> Thb (1a)
| D2 |> Thd (1b)
Whether one or both of the above or one of the predetermined ones is satisfied can be examined. However, since b / a is a parameter representing the state on the central side, it is desirable to consider at least the value of b / a. In step S115, the parameter to be determined for abnormality, the equation for determining abnormality, and the threshold value to be used are determined in advance, but need not be fixed, and may be changed at any time.

  In the above equation, (current) indicates the current calculated value, and (ref) indicates the calculated value at the time of the latest cuff blood pressure measurement as a reference. Further, the threshold values Thb and Thd as values indicating the normal range may be equal or may be determined individually. Further, the change amount may not be an absolute value, and the increase-side threshold value (upper limit value) and the decrease-side threshold value (lower limit value) may be individually determined. The specific value of the threshold can be determined as appropriate. For example, in the formulas (1a) and (1b), Thb = Thd = 20 (%) can be set.

In addition, this threshold value can be dynamically changed according to a blood pressure measurement result by a periodic cuff. For example, if the blood pressure measurement result by cuff is lower than the predetermined value, it is possible to monitor the blood pressure decrease more strictly by setting the threshold on the decrease side to be stricter (easy to exceed the threshold) than otherwise. It is. Specifically, when the normal range is defined by the upper limit value and the lower limit value, by setting the lower limit value higher, it becomes easier to fall below the lower limit value, and the decrease in blood pressure can be strictly monitored. Conversely, when the cuff measurement result is high, the increase-side threshold value can be set more severely (lower the upper limit value of the normal range).
Further, the fluctuation amount need not be a ratio (percentage) but may be a difference.

  If it is determined in step S115 that the fluctuation amount is abnormal, the process proceeds to step S130. If it is determined that the fluctuation amount is normal, the process returns to step S111 to continue processing for the next heartbeat.

On the other hand, in steps S121 to S125, a blood pressure value estimation process similar to the conventional one is executed.
In step S121, the pulse wave propagation time is calculated based on the ECG detected by the electrocardiogram electrode 20 and the fingertip volume pulse wave detected by the finger sensor 30. More specifically, the control unit 100 performs signal processing such as noise removal and waveform shaping normally performed on the ECG and the fingertip volume pulse wave, and then calculates a time difference between the feature points in each heartbeat. Calculated as the pulse wave velocity. In this case, for example, the feature point of the ECG can be the peak position of the R wave, and the feature point of the finger plethysmogram can be the rising position of the waveform, for example. Further, as described above, since there is a time difference (pre-ejection period) from the appearance of the R wave to the actual pulse wave generation, it corresponds to the previous ejection period statistically obtained in advance from the time difference between the feature points. Correction can also be performed by reducing the time.

In step S123, an estimated blood pressure value is obtained from the obtained pulse wave propagation time.
That is, the pulse wave propagation time, for example, as shown in Patent Document 1,
Estimated blood pressure value = α × (pulse wave propagation time [msec]) + β (2)
(Α and β are coefficients, α <0, β> 0)
The estimated blood pressure value is obtained by applying to the equation.

  The coefficients α and β may be obtained in advance. That is, since this calculation formula is a binary linear equation, the values of the coefficients α and β can be determined by using at least two different measured blood pressure values and the corresponding pulse wave propagation times.

  In addition, this coefficient does not need to be fixed, and it is an optimal value each time using the actual measurement value obtained by other methods (measurement by cuff or open blood measurement) and the pulse wave propagation time at the corresponding time point. It can also be configured to be updated so that

In step S125, it is determined whether the estimated blood pressure value is an abnormal value. This determination may be made by determining whether the estimated blood pressure value exceeds the upper limit value or the lower limit value of the predetermined normal range, or a predetermined amount (variation ratio) with respect to the blood pressure measurement value by the latest cuff. Alternatively, it may be a difference) by determining whether or not the above fluctuation is observed.
These upper limit value, lower limit value, or fluctuation amount may be fixedly set for the blood pressure measurement value by the cuff as well as the threshold value in the waveform parameter, or may be dynamically changed according to the specific value of the measurement value. You may comprise.

If it is determined in step S125 that the estimated blood pressure value is abnormal, the process proceeds to step S130. If it is determined that the estimated blood pressure value is normal, the process returns to step S121 to continue processing for the next heartbeat.
In step S130, it is determined whether or not a condition for performing blood pressure measurement by the cuff is satisfied. That is,
(1) Continued for a predetermined period, it was determined that both the pulse wave parameter and the estimated blood pressure value were abnormal. (2) Whether any of the predetermined time passed from the blood pressure measurement by the latest cuff? Determine if.

When any one of these conditions is satisfied, the control unit 100 controls the pump 14 to increase the pressure of the cuff 10 and monitor the input signal from the pressure sensor 12 while gradually exhausting after blood pumping. Based on the metric method, the maximum blood pressure value, the average blood pressure value, and the minimum blood pressure value are obtained. In addition, the waveform parameter immediately before blood pressure measurement using the cuff 10 and the estimated blood pressure value are stored in the storage unit 90 and used for calibration of the coefficients α and β included in the calculation formula of the estimated blood pressure value and subsequent processing. During the blood pressure value measurement by the cuff, the waveform parameter calculation and determination process in steps S111 to S115 and the estimated blood pressure value calculation process in steps S121 to S125 are interrupted or the result is ignored.
Thereafter, the above process is repeated until the end of monitoring is instructed.

FIG. 4 is a diagram showing the relationship between the estimated blood pressure value continuously calculated by the blood pressure measurement device of the present embodiment, the blood pressure value measured invasively, and the waveform parameters.
In FIG. 4, the estimated blood pressure value calculated based on the pulse wave propagation time by ESYS and the blood pressure value measured by ISYS are shown. The straight lines drawn above and below these blood pressure values indicate values of + 20% and −20% from the cuff measurement values when the cuff measurement is performed at times t0, t1, and t2. ing.

That is, FIG. 4 shows the blood pressure value measured invasively to show the relationship between the estimated blood pressure value and the actual blood pressure value, but the actual blood pressure monitoring device does not perform invasive measurement (observation). If bloody measurements are taken, there is no point in estimating the blood pressure itself). Actually, the measurement by the cuff is performed periodically, and during the period when the blood pressure measurement by the cuff is not performed, monitoring by the estimated blood pressure value based on the pulse wave propagation time is performed. FIG. 4 shows a case where the blood pressure measurement value ± 20% by the latest cuff is used as a threshold for determining whether or not the estimated blood pressure value can be regarded as a normal value.
FIG. 4 shows whether the waveform parameters b / a and d / a exceed the threshold as BPA_OVER and DPA_OVER, respectively.

In FIG. 4, the waveform parameter (b / a) partially shows an abnormal value from time t0 to t1, but the cuff activation is not performed because the estimated blood pressure value is within the normal range, and a predetermined time from t0. The blood pressure is regularly measured with a cuff at t1 after elapse.
After the time t1, there is a period in which the estimated blood pressure value is outside the lower limit value and the upper limit value, but since the waveform parameters are both normal values, cuff activation is not performed. However, after that, both the estimated blood pressure value and the waveform parameter (b / a) show abnormal values, and the blood pressure measurement by the cuff is performed at time t2. Here, (t1-t0)> (t2-t1), and the cuff activation at time t2 is shorter than the regular interval.
After that, after time t2, the waveform parameter shows an abnormal value for a while, but the cuff activation is not performed because the estimated blood pressure value is within the normal range.

  As can be seen from FIG. 4, according to the blood pressure monitoring apparatus of the present embodiment, the blood vessel obtained from the acceleration pulse wave in addition to the estimated blood pressure value calculated based on the pulse wave propagation time obtained from the ECG and the pulse wave. Since the presence or absence of true fluctuation of the blood pressure value is determined using the value of the parameter representing the state of the blood pressure, it is possible to determine the necessity of blood pressure measurement with the cuff with higher accuracy than the conventional method.

(Calculation processing of calculation formula)
Next, the calibration process of the estimated blood pressure value calculation formula in the blood pressure monitoring apparatus of the present embodiment will be described.
As described above, when the result of the blood pressure measurement by the cuff is obtained at least periodically, the calculation formula for correcting the estimated blood pressure value based on the measurement result (calibration of the coefficients α and β) is performed. Thus, it is possible to improve the accuracy of the estimated blood pressure value in the section until the next cuff measurement. In the present embodiment, the calculation formula is calibrated based on the blood pressure measurement result by the cuff, and the estimation accuracy can be improved by performing the calibration considering the fluctuation amount of the waveform parameter of the acceleration pulse wave described above. it can.

As already explained, the calculation formula for obtaining the estimated blood pressure value from the pulse wave propagation time is:
Estimated blood pressure value = α × (pulse wave propagation time [msec]) + β (2)
(Α and β are coefficients, α <0, β> 0)
However, by calibrating these coefficients according to the difference (error) between the actual measurement value and the estimated value, or the difference between the previous actual measurement value and the current actual measurement value, more accurate processing can be performed in the subsequent processing. It is possible to calculate a high estimated blood pressure value.

In this embodiment, the expression (2) is
Estimated blood pressure value = (α + γ) × (pulse wave propagation time [msec]) + β (2 ′)
(Α, β, γ are coefficients, α <0, β> 0)
And a new coefficient γ is introduced. The coefficient γ is a correction term for the coefficient α, and has a value corresponding to the fluctuation amount of the waveform parameter obtained from the acceleration pulse wave. In other words, when the fluctuation of the waveform parameter of the acceleration parameter is large, there is a possibility that a functional change of the blood vessel has occurred. Therefore, it is considered preferable to increase the degree of correction than when the fluctuation of the waveform parameter is small. Because.

In the present embodiment, the coefficient α is calibrated as shown in Table 1, for example.
<Table 1>
d α Correction amount
30 <d recalculation 20 <d ≦ 30 +10
10 <d ≦ 20 + 5
−10 ≦ d ≦ 100 (no correction)
−20 ≦ d <−10 −5
−30 ≦ d <−20 −10
d <−30 Recalculation where d is (estimated blood pressure value−actual value) or (actual value (t−1) −actual value (t)) [mmHg].

In the case of d ≧ 30 or d ≦ −30, it cannot be handled by simple correction, and the coefficient is calculated again using the current measured value and the latest measured value.
Further, the coefficient β is also calibrated using the calibrated coefficient α and the actually measured value.

  The correction term γ is introduced when the amount of fluctuation (the absolute difference or fluctuation ratio of the parameter value) of the waveform parameter from the value at the time of blood pressure measurement by the latest cuff exceeds a predetermined value. When the amounts are D1 (%) and D2 (%) described above, values shown in Table 2 below are assumed.

<Table 2>
D (D1 and / or D2) γ
30 <D + 3
20 <D ≦ 30 + 2
10 <D ≦ 20 + 1
−10 ≦ D ≦ 100
−20 ≦ D <−10 −1
−30 ≦ D <−20 −2
D <-30 -3

  Note that when there are a plurality of waveform parameters (b / a, d / a) as in the present embodiment, it is possible to appropriately set which waveform parameter variation amount to introduce γ, for example, Γ is introduced when any fluctuation amount of the parameter exceeds the threshold value.

  Although Table 2 shows a case where the value of the correction amount γ changes according to the value of the waveform parameter fluctuation amount D, the value of the correction amount γ may be changed according to the value of d. For example, the value of γ may be set to increase as the value of d increases. Also, these conditions can be combined, for example, by adding and applying the value of γ by D and the value of γ by d. Alternatively, when the waveform parameter fluctuation amount D or d satisfies the condition for introducing the correction amount, the absolute value of γ may be constant regardless of the value of D or d. Specifically, for example, in Table 2, a uniform +2 γ is introduced if 10 <D, and a uniform γ is introduced if D <−10.

  FIG. 5 is a flowchart for explaining a calculation formula calibration operation in the biological information monitoring apparatus of this embodiment. The following processing is realized by the control unit 100 executing the control program, similarly to the above-described blood pressure monitoring processing. Further, it may be performed after step S140 in the flowchart of FIG. 3 ends and before returning to step S121.

  First, in step S201, a blood pressure value (measured value) measured using a cuff is acquired. In step S203, the measured value is compared with the estimated blood pressure value immediately before starting the cuff blood pressure measurement or the measured value immediately before. In step S205, it is determined whether or not the estimated blood pressure value calculation formula needs to be calibrated based on the magnitude of these differences and the magnitude of the fluctuation rate.

Specifically, as described above,
(When judging by difference)
｜ Estimated blood pressure value−Measured value |> Th1
| Measured Value (t-1) -Measured Value (t) |> Th2
(When judging by variation ratio)
| (Estimated blood pressure value / actual measurement value) -1 |> Th3
| (Actual value (t-1) / actual value (t))-1 |> Th4
Based on the above conditions, it is determined that calibration is necessary when the amount of variation is large.
If it is determined that calibration is not necessary (the accuracy of the estimated blood pressure value is sufficient), the process ends.

  On the other hand, if it is determined that calibration is necessary, the coefficient is calibrated in step S207. As described above, the coefficient is first calibrated according to the value of d which is (estimated blood pressure value−actual value) or (actual value (t−1) −actual value (t)).

  Next, in step S209, it is necessary to perform correction in consideration of the fluctuation amount of the waveform parameter, specifically, whether the fluctuation amount of the waveform parameter is large, for example, the equation (1a) described in the first embodiment ) And (1b). Here, it is determined that the amount of variation is large when any of the parameters satisfies the expressions (1a) and (1b).

  If it is determined that the fluctuation of the waveform parameter is large, the coefficient α is corrected by γ described above in step S211. In step S213, the coefficient β is calibrated using the coefficient α after calibration (when the fluctuation of the waveform parameter is not large) or the coefficient α after calibration and correction (when the fluctuation of the waveform parameter is large) and the actually measured blood pressure value. . Then, the coefficient after calibration or the calculation formula including the coefficient after calibration is stored in the storage unit 90.

  As described above, according to the present embodiment, in the blood pressure monitoring apparatus that calibrates the calculation formula for obtaining the estimated blood pressure value from the pulse wave propagation speed during blood pressure measurement using the cuff, the fluctuation amount of the waveform parameter obtained from the acceleration pulse wave Is large, correction of the coefficient calibration amount enables accurate calibration even when there is a change in blood vessel functionality such as rapid dilatation or contraction of the blood vessel. A good estimated blood pressure value can be obtained.

  In the above-described embodiment, the case where the pulse wave propagation velocity is measured using the ECG and the fingertip volume pulse wave has been described from the viewpoint of diverting a normal biological information monitor device. However, the present invention can also be applied to a blood pressure monitoring device that calculates the pulse wave velocity by another method. For example, a device that measures pulse wave propagation time from a pulse wave measured with a cuff pressurized below diastolic blood pressure and a fingertip volume pulse wave, a pulse wave detected with a pulse wave sensor, and a pulse wave detected with a cuff Therefore, the present invention can also be applied to a device that measures pulse wave propagation time.

  Furthermore, in the above-described embodiment, the case where the blood pressure measurement value using the oscillometric method by the cuff is adopted as the method for measuring the blood pressure value used for coefficient calibration has been described. However, the blood pressure value used when calibrating the coefficient of the calculation formula for the estimated blood pressure value should be the blood pressure value measured using any other blood pressure measurement method as long as the accuracy of the calibration standard is satisfied. Is possible.

It is a block diagram showing an example of composition of a living body information monitor device as a blood pressure monitoring device concerning an embodiment of the present invention. It is a figure which shows the example of an original waveform and its acceleration pulse wave. It is a flowchart explaining the blood-pressure monitoring operation | movement of the biometric information monitor apparatus which concerns on embodiment of this invention. It is a figure which shows the actual example of the blood pressure value calculated with the biological information monitor apparatus which concerns on embodiment, the blood pressure value measured invasively, and a waveform parameter. It is a flowchart explaining the calibration operation | movement of the estimated blood pressure value calculation formula in the biological information monitor apparatus which concerns on embodiment of this invention.

Claims (13)

A blood pressure measurement unit for measuring blood pressure by a predetermined method;
Pulse wave acquisition means for acquiring a pulse wave at a predetermined site of a living body;
A pulse wave propagation time calculating means for calculating a pulse wave propagation time from the pulse wave and a pulse wave acquired at a part different from the electrocardiogram or the predetermined part;
An estimated blood pressure value calculating means for calculating an estimated blood pressure value by applying the pulse wave propagation time to a predetermined calculation formula;
Acceleration pulse wave calculating means for calculating an acceleration pulse wave from the pulse wave;
Waveform parameter calculating means for calculating a predetermined waveform parameter from a waveform included in the acceleration pulse wave;
Calibration means for calibrating the calculation formula using a measurement value by the blood pressure measurement unit,
The blood pressure monitoring apparatus according to claim 1, wherein, when the fluctuation amount of the waveform parameter exceeds a predetermined amount, the calibration means performs the calibration after correcting the calibration amount applied in other cases.   2. The blood pressure monitoring apparatus according to claim 1, wherein the correction is such that a calibration amount larger than a calibration amount applied when the fluctuation amount of the waveform parameter does not exceed a predetermined amount. .   The calibration means determines whether the calibration is necessary based on a comparison between the current measurement value by the blood pressure measurement unit and the previous measurement value, or a comparison between the current measurement value by the blood pressure measurement unit and the estimated blood pressure value. The blood pressure monitoring apparatus according to claim 1, wherein the calibration is performed only when it is determined and determined to be necessary.   The blood pressure monitoring apparatus according to any one of claims 1 to 3, wherein the magnitude of the correction is constant.   The magnitude of the correction is the amount of fluctuation of the waveform parameter, the comparison between the current measurement value by the blood pressure measurement unit and the previous measurement value, or the current measurement value by the blood pressure measurement unit and the estimated blood pressure value. The blood pressure monitoring apparatus according to any one of claims 1 to 3, wherein the blood pressure monitoring apparatus changes according to a comparison result. The calculation formula is estimated blood pressure value = α × (pulse wave propagation time [msec]) + β
(Α and β are coefficients, α <0, β> 0)
The calibration means applies the calibration amount to α and then calibrates the coefficient β by applying a measurement value obtained by the blood pressure measurement unit as the estimated blood pressure value. 6. The blood pressure monitoring device according to claim 1, wherein calibration is performed.   The blood pressure monitoring apparatus according to claim 6, wherein the calibration unit corrects the calibration amount with respect to the coefficient α when the fluctuation amount of the waveform parameter exceeds a predetermined amount.   The blood pressure monitoring apparatus according to any one of claims 1 to 7, wherein the predetermined waveform parameter includes at least one of a parameter related to a systolic front component and a parameter related to a post systolic component.   The blood pressure monitoring apparatus according to claim 8, wherein the predetermined waveform parameter is a crest ratio of a characteristic waveform included in the acceleration pulse wave.   The blood pressure monitoring apparatus according to claim 9, wherein the predetermined waveform parameter is a wave height ratio of b wave to a wave included in the acceleration pulse wave and a wave height ratio of d wave to a wave.   The blood pressure monitoring apparatus according to any one of claims 1 to 10, wherein the blood pressure measurement unit performs blood pressure measurement by a method in which measurement cannot be performed continuously.   The blood pressure monitoring device according to any one of claims 1 to 10, wherein the blood pressure measurement unit performs blood pressure measurement by an oscillometric method using a cuff.   The blood pressure monitoring apparatus according to any one of claims 1 to 12, wherein the pulse wave acquisition unit acquires a fingertip volume pulse wave.

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