JP2007135678A - Hemodynamics measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hemodynamics measurement apparatus capable of obtaining a sufficient precision in spite of fluctuations in a pulse pressure if vascular stiffness is measured on a same subject under same conditions. <P>SOLUTION: When the amount of characteristics corresponding to the hemodynamics is computed based on a first maximum cuff pressure, a first lowest cuff pressure, a second maximum cuff pressure, and a second lowest cuff pressure in an envelop curve where the maximum value for every heartbeat in temporal differentiation signals is plotted, the hemodynamics measurement apparatus corrects the amount of characteristics according to the pulse pressure (a systolic blood pressure-a diastolic blood pressure). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a hemodynamic measurement device.

  When measuring hemodynamics, the signal with the pulse wave amplitude component superimposed on the cuff pressure is time-differentiated, the cuff pressure is taken on one axis of the XY coordinates, and the differentiating means is taken on the other axis of the XY coordinate axes. Is taken, the maximum value for each heartbeat is plotted among the time differential signals, an envelope connecting the plotted maximum values is calculated, and the first existing on the envelope It is known to measure hemodynamics based on the highest cuff pressure, the first lowest cuff pressure, the second highest cuff pressure and the second lowest cuff pressure.

That is, a first value that is smaller than the peak value of the envelope is set, and among the plurality of cuff pressures corresponding to the position on the envelope that is the first value, the highest cuff pressure is used. A plurality of first highest cuff pressures and first lowest cuff pressures that are the lowest cuff pressures are calculated, and a plurality of positions corresponding to positions on the envelope that are second values different from the first values. The second highest cuff pressure that is the highest cuff pressure and the second lowest cuff pressure that is the lowest cuff pressure are calculated, and the calculated first highest cuff pressure and the first cuff pressure are calculated. A ratio between the difference between the lowest cuff pressure and the difference between the second highest cuff pressure and the second lowest cuff pressure is calculated as a feature value, and hemodynamics is measured based on the calculated feature value. It is known (for example, refer to Patent Document 1).
Patent Publication 2001-104258

  FIG. 5 is a diagram for explaining the operation of the conventional example.

  FIG. 5 (1) is a diagram showing an envelope when the pulse pressure is small, FIG. 5 (2) is a diagram showing an envelope when the pulse pressure is large, and FIG. It is the figure which normalized notation of both envelopes and made the comparison notation by making the level of a leading value into 100%.

  As is apparent from FIG. 5, even if the blood vessel characteristics are the same, if the pulse pressure is different, the shape of the envelope (the envelope in which the maximum value for each heartbeat in the time differential signal is plotted) changes. As the pulse pressure increases, the width near the maximum value increases.

  Therefore, when calculated by the conventional method, even if the blood vessel characteristics are the same, the value of the feature amount is measured to be larger as the pulse pressure at the time of measurement is larger.

  That is, in the conventional example, even if the subject is the same under the same measurement conditions, if the pulse pressure varies, the shape of the envelope itself changes, and the feature amount is varied. Therefore, the conventional example has a problem that it is difficult to obtain an accuracy higher than a predetermined accuracy in measuring the degree of vascular hardening.

In the present invention, if the subject is the same measurement condition, even if the pulse pressure varies, the shape of the envelope plotting the maximum value for each heartbeat in the time differential signal does not change, and the feature amount varies. Therefore, it is an object of the present invention to provide a hemodynamic measurement device capable of obtaining sufficient accuracy when measuring the degree of vascular sclerosis.

The present invention provides blood circulation based on the first highest cuff pressure, the first lowest cuff pressure, the second highest cuff pressure, and the second lowest cuff pressure in the envelope obtained by plotting the maximum value for each heartbeat among time differential signals. When calculating a feature amount corresponding to a dynamic state, the hemodynamic measurement device corrects the feature amount according to a pulse pressure (maximum blood pressure−minimum blood pressure).

In the present invention, when calculating a feature value corresponding to hemodynamics, the feature value is corrected according to the pulse pressure (maximum blood pressure−minimum blood pressure). Therefore, the larger the pulse pressure, the smaller the feature value. Therefore, there is an effect that sufficient accuracy can be obtained when measuring the degree of sclerosis of blood vessels.

  The best mode for carrying out the invention is the following embodiment.

  FIG. 1 is a block diagram showing a hemodynamic measurement apparatus 100 according to an embodiment of the present invention.

  The hemodynamic measurement device 100 includes a cuff 11 that is wound around the arm of a measurement subject, a pressurizing unit 12 that pressurizes the cuff 11 to a predetermined pressure necessary for blood pressure measurement, and a cuff 11 that is pressurized by the pressurizing unit 12. The pressure detection means 14 includes a slow speed exhaust means 13 for gradually exhausting the internal pressure, a pressure transducer for detecting the pressure of the cuff 11, and converts the pressure into an electric signal (pulse) and outputs the electric signal (pulse). The sampling means 15 that counts the electrical signal (pulse) from the signal within a certain time, periodically repeats the above counting by the sampling signal, and A / D converts the sampling value, the CPU 20, the ROM 21, the RAM 22, and the operation Means 23, a display device 61, a printer 62, and an external terminal 63 are provided.

  The cuff 11, the pressurizing means 12, the slow exhaust means 13, and the pressure detecting means 14 are connected by a flexible tube.

  The CPU 20 controls the entire hemodynamic measurement device 100 and functionally cooperates with a program stored in the ROM 21 to functionally differentiate the time differentiating means 16, the envelope calculating means 30, the first 1 setting means 31, second setting means 32, first highest cuff pressure calculating means 41, first lowest cuff pressure calculating means 42, second highest cuff pressure calculating means 43, and second lowest cuff pressure. The calculation means 44, the feature quantity calculation means 51, and the feature quantity correction means 52 are realized.

  The ROM 21 is a memory that stores a program of the flowchart shown in FIG. 4 to be described later. The RAM 22 is a memory that stores a calculation result of the CPU 20, and the operation means 23 has predetermined function keys and the like. is there.

  Further, the pressurizing means 12, the forced exhaust means 13, the pressure detecting means 14, and the sampling means 15 are controlled by the CPU 20.

  The envelope calculation means 30 takes the cuff pressure on one axis of the XY coordinate, takes the time differential signal differentiated by the differentiation means on the other axis of the XY coordinate axis, and outputs the heart rate signal among the time differential signals. This is a means for plotting the maximum value for each and calculating the envelope connecting the plotted maximum values.

  The first value setting means 31 is a means for setting a first value V1, which is a value smaller than the peak value of the envelope.

  The second value setting means 32 is a means for setting a second value V2 that is a value smaller than the peak value of the envelope and is different from the first value V1.

  The first highest cuff pressure calculating means 41 is the highest cuff pressure among the plurality of cuff pressures corresponding to the position on the envelope whose value of the time differential signal is the first value on the XY coordinates. A means for calculating a certain first maximum cuff pressure.

  The first lowest cuff pressure calculating means 42 is the lowest cuff pressure among the plurality of cuff pressures corresponding to the position on the envelope whose value of the time differential signal is the first value on the XY coordinates. Means for calculating the first minimum cuff pressure.

  The second highest cuff pressure calculating means 43 is the highest cuff pressure among the plurality of cuff pressures corresponding to the position on the envelope whose value of the time differential signal is the second value on the XY coordinates. This is means for calculating the second highest cuff pressure.

  The second lowest cuff pressure calculating means 44 is the lowest cuff pressure among the plurality of cuff pressures corresponding to the position on the envelope whose value of the time differential signal is the second value on the XY coordinates. Means for calculating the second lowest cuff pressure.

  The feature amount calculating means 51 calculates a ratio between the calculated difference between the first highest cuff pressure and the first lowest cuff pressure and the difference between the second highest cuff pressure and the second lowest cuff pressure. It is means for calculating as a feature value.

The feature amount correcting unit 52 is a unit that corrects the calculated feature amount according to the pulse pressure. In other words, the feature amount correcting unit 52 compares the calculated difference between the first highest cuff pressure and the first lowest cuff pressure and the difference between the second highest cuff pressure and the second lowest cuff pressure. This is a means for multiplying the feature quantity by a pulse pressure correction term (k3 / PP) ^α to correct it. The k3 and α are arbitrary constants, and the PP is a pulse pressure (maximum blood pressure−minimum blood pressure).

  Next, the operation of the hemodynamic measurement device 100 will be described.

  FIG. 2 is a diagram showing a change in cuff pressure in the above embodiment.

  The cuff 11 is wrapped around the arm, wrist, finger, etc., and the pressure inside the cuff 11 is increased to a predetermined pressure by the pressurizing means 12, and then the linear exhausting means 13 at a rate of 3-5 mmHg / sec. The pulse wave amplitude component is superimposed on the cuff pressure in the process of this pressure reduction.

  FIG. 3 is a diagram showing an example of the relationship between the cuff pressure and the envelope of the time differential signal of the cuff pressure when the cuff pressure is increased and then reduced at a slow speed in the above embodiment.

  First, the cuff pressure is taken on the horizontal axis in FIG. In this case, since the slow exhaust means 13 exhausts at a constant speed, the cuff pressure decreases with the passage of time. Further, the time differential signal (dP / dt) of the cuff pressure is taken on the vertical axis of FIG. A time differential signal is generated at regular intervals, and an envelope E is obtained by connecting the peak values of the time differential signal. Further, interpolation is performed between one time differential signal and the adjacent time differential signal by a predetermined method.

Next, a first value V1 and a second value V2 are set in advance. Here, the first value V1 is 0.7 times the peak value Sdp of the envelope E (K1 times).
Value (k1 · Sdp) is adopted. Further, a value (k2 · Sdp) that is 0.5 times (K2 times) the peak value Sdp of the envelope E is adopted as the second value V2.

  Next, a specific operation of the above embodiment will be described.

  When measuring hemodynamics with the hemodynamic measuring device 100, specifically, when the cuff 11 is wound around the arm of the person to be measured and the measurement start switch provided in the operation means 23 is turned on, it is necessary for blood pressure measurement. The pressurizing means 12 pressurizes the cuff 11 until reaching a certain pressure, and after this pressurization is stopped, the air in the cuff 11 is gradually exhausted by the slow exhaust means 13, and accordingly, the pressure displacement due to the pulse wave component Begins to be transmitted to the cuff.

  The pressure detection means 14 converts the cuff pressure into an electrical signal as a change in frequency, the sampling means 15 samples every certain time (for example, every 50 ms), and outputs a pulse in accordance with the sampled cuff pressure. .

  FIG. 4 is a flowchart showing the operation of the hemodynamic measurement device 100.

  In the hemodynamic measurement device 100, when the cuff 11 is wound around the upper arm of the measurement subject and the power is turned on, the contents of the RAM 22 are initialized, and then the cuff 11 is applied to a pressure required for blood pressure measurement (upper limit pressure). After that, the cuff 11 is gradually exhausted, and in the exhausting process, the pulse pressure changes the cuff pressure, and the pulse wave component is superimposed on the cuff pressure. A pulse wave component is extracted from the cuff pressure (S4 to S7, S11).

  That is, the cuff pressure sampling value is stored in the RAM 22 (S4). When the cuff pressure reaches a predetermined lower limit pressure (S5), the cuff pressure sampling and the sampling value storage are terminated (S6), and the pulse wave The components are extracted, the exhaust rate is corrected, and the value is stored in the RAM 22 (S7).

  And based on the value memorize | stored in RAM22, the time differential signal of a sampling value is calculated, the generation | occurrence | production time of the peak of a time differential signal is calculated, and the value is memorize | stored in RAM22 (S11).

  That is, the pulse wave component is extracted by the difference (time differential value) of the cuff pressure in a minute time. That is, only when the extracted difference is positive and continuous, the difference is added and the maximum value of the added value is obtained to detect the maximum value of the pulse wave component in one cycle.

  Next, an envelope E of the time differential signal is obtained (S12).

  Then, the maximum value Sdp of the envelope E is obtained (S13), and the maximum cuff pressure corresponding to k1 times (70%) of the maximum value Sdp of the envelope E is set as the first maximum cuff pressure P1max (S14). . That is, in the graph shown in FIG. 3, among the envelope E, the point where the time differential signal (dP / dt) is k1 times (70%) the maximum value Sdp of the envelope E is two points E11 and E12. The cuff pressure corresponding to the point E11 having the higher cuff pressure is defined as the first highest cuff pressure P1max.

  The minimum cuff pressure corresponding to k1 times (70%) of the maximum value Sdp of the envelope E is set as the first minimum cuff pressure P1min (S14). That is, in the graph shown in FIG. 3, among the envelope E, the point where the time differential signal (dP / dt) is k1 times (70%) the maximum value Sdp of the envelope E is two points E11 and E12. The cuff pressure corresponding to the point E12 with the lower cuff pressure is defined as the first minimum cuff pressure P1min.

  Note that k1 times (70%) of the maximum value Sdp of the envelope E is an example of the first value V1.

  Further, the maximum cuff pressure corresponding to k2 times (50%) of the maximum value Sdp of the envelope E is set as the second maximum cuff pressure P2max (S15). That is, in the graph shown in FIG. 3, in the envelope E, the point where the time differential signal (dP / dt) is k2 times (50%) the maximum value Sdp of the envelope E is two points E21 and E22. The cuff pressure corresponding to the point E21 having the higher cuff pressure is set as the second highest cuff pressure P2max.

  The minimum cuff pressure corresponding to k2 times (50%) of the maximum value Sdp of the envelope E is set as the second minimum cuff pressure P2min (S15). That is, in the graph shown in FIG. 3, in the envelope E, the point where the time differential signal (dP / dt) is k2 times (50%) the maximum value Sdp of the envelope E is two points E21 and E22. The cuff pressure corresponding to the point E22 having the lower cuff pressure is defined as the second minimum cuff pressure P2min.

  Note that k2 times (50%) of the maximum value Sdp of the envelope E is an example of the second value V2.

  However, 1> k1> k2> 0. k1 and k2 are arbitrary constants. In the above embodiment, k1 = 0.7 and k2 = 0.5, but are not necessarily limited to these values, and may be changed based on clinical data. Can do.

Next, based on the first highest cuff pressure P1max, the first lowest cuff pressure P1min, the second highest cuff pressure P2max, and the second lowest cuff pressure P2min, a feature amount (sharpness of the envelope E) G is calculated (S21). ). That means
Feature amount G = (P1max−P1min) / (P2max−P2min)} · (k2 / k1) (1)
Can be requested.

Then, by correcting the characteristic amount G by multiplying {(P1max−P1min) / (P2max−P2min)} · (k2 / k1) by the pulse pressure correction term (k3 / PP) ^α , A feature amount Ga is obtained (S22). The k3 and α are arbitrary constants, and the PP is a pulse pressure (maximum blood pressure−minimum blood pressure).

  Note that k3 is, for example, 40 to 50, and α is, for example, 0 <α <1.

That means
Feature amount Ga = (P1max−P1min) / (P2max−P2min)} · (k2 / k1) · (k3 / PP) ^α (2)
In other words, the feature amount calculating means for realizing the above equation (1) includes the difference between the first highest cuff pressure and the first lowest cuff pressure, and the difference between the second highest cuff pressure and the second lowest cuff. This is a means for obtaining the feature amount G by calculating the ratio of.

The feature amount correcting means for realizing the above equation (2) includes a difference between the first highest cuff pressure and the first lowest cuff pressure, and a difference between the second highest cuff pressure and the second lowest cuff. Is calculated, and the corrected feature quantity Ga is obtained by multiplying the calculated ratio by (k2 / k1) · (k3 / PP) ^α .

  This feature amount Ga has a correlation with the degree of arteriosclerosis. Further, according to the above-described embodiment, when the feature amount corresponding to the hemodynamics is calculated, the feature amount is corrected according to the pulse pressure (maximum blood pressure−minimum blood pressure). Correction is applied in the direction of decreasing, and therefore sufficient accuracy can be obtained when measuring the degree of vascular stiffness.

  Then, the calculated feature amount Ga after correction is displayed on the display device 61 (S23).

  Further, instead of displaying the corrected feature quantity Ga on the display device 61, the corrected feature quantity Ga may be printed on the printer 52, and data corresponding to the corrected feature quantity Ga is externally stored. You may make it output via the terminal 63. FIG.

In the above embodiment, the cuff pressure is sampled while reducing the cuff pressure slightly, but conversely, the cuff pressure may be sampled while increasing the cuff pressure slightly.

1 is a block diagram showing a hemodynamic measurement device 100 according to an embodiment of the present invention. It is a figure which shows the change of the cuff pressure in the said Example. In the said Example, it is a figure which shows an example of the relationship between the cuff pressure at the time of carrying out slow pressure reduction after increasing cuff pressure, and the envelope of the time differential signal of cuff pressure. 3 is a flowchart showing the operation of the hemodynamic measurement device 100. It is a figure explaining operation | movement of a prior art example.

Explanation of symbols

100 ... hemodynamic measuring device,
11 ... cuff,
15: Sampling means,
20 ... CPU,
21 ... ROM,
16. Time differential means,
30: Envelope calculation means,
31. First setting means,
32. Second setting means,
41. First highest cuff pressure calculating means,
42. First minimum cuff pressure calculating means,
43. Second highest cuff pressure calculating means,
44. Second lowest cuff pressure calculating means,
51. Feature quantity calculation means,
52... Feature amount correcting means,
61. Display device,
62 ... Printer,
63: External terminal.

Claims (4)

Differential means for differentiating in time the signal in which the pulse wave amplitude component is superimposed on the cuff pressure;
The cuff pressure is taken on one axis of the XY coordinates, the time differential signal differentiated by the differentiating means is taken on the other axis of the XY coordinate axes, and the maximum value for each heartbeat is plotted among the time differential signals. Envelope calculating means for calculating an envelope connecting the plotted maximum values;
First value setting means for setting a first value that is smaller than the peak value of the envelope;
On the XY coordinates, a first highest cuff pressure that is the highest cuff pressure among a plurality of cuff pressures corresponding to positions on the envelope whose value of the time differential signal is the first value is calculated. A first highest cuff pressure calculating means;
On the XY coordinates, a first lowest cuff pressure that is the lowest cuff pressure among a plurality of cuff pressures corresponding to positions on the envelope whose value of the time differential signal is the first value is calculated. A first minimum cuff pressure calculating means;
Second value setting means for setting a second value that is smaller than the peak value of the envelope and is different from the first value;
On the XY coordinates, a second highest cuff pressure that is the highest cuff pressure among a plurality of cuff pressures corresponding to positions on the envelope whose value of the time differential signal is the second value is calculated. A second highest cuff pressure calculating means;
On the XY coordinates, a second lowest cuff pressure that is the lowest cuff pressure is calculated among a plurality of cuff pressures corresponding to positions on the envelope whose value of the time differential signal is the second value. A second minimum cuff pressure calculating means;
A feature amount calculated as a feature amount by calculating a ratio between the calculated difference between the first highest cuff pressure and the first lowest cuff pressure and the difference between the second highest cuff pressure and the second lowest cuff pressure. Computing means;
Feature amount correcting means for correcting the calculated feature amount according to the pulse pressure;
A hemodynamic measurement device characterized by comprising: In claim 1,
The feature amount correcting means is a means for correcting the feature amount by multiplying {(P1max−P1min) / (P2max−P2min)} · (k2 / k1) by a pulse pressure correction term (k3 / PP) ^α. (P1max is the first highest cuff pressure, P1min is the lowest cuff pressure, P2max is the second highest cuff pressure, and P2min is the second lowest cuff pressure. The k1, k2, k3, α are arbitrary constants, and the PP is a pulse pressure (maximum blood pressure−minimum blood pressure). In claim 1 or claim 2,
A hemodynamic measurement apparatus comprising: display means for displaying the corrected feature value itself; or display means for displaying the corrected feature quantity in an analog graph. In claim 1 or claim 2,
A hemodynamic measurement apparatus comprising: a printer that prints the corrected feature value; or an external terminal that outputs data of the corrected feature value.

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