JP3602875B2 - Blood pressure monitoring device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a blood pressure monitoring device that monitors a blood pressure value of a living body based on a pulse wave detected by a pulse wave sensor.
[0002]
[Prior art]
When monitoring the blood pressure value of the living body, a blood pressure value measuring unit that has a cuff wound around a part of the living body and measures the blood pressure value of the living body by changing a compression pressure by the cuff is provided. In many cases, an automatic blood pressure measurement device is used, and the blood pressure value is measured by repeatedly starting compression by a cuff at a predetermined cycle. However, in the case of such an automatic blood pressure measurement device, if the measurement interval is shortened in order to increase the accuracy of blood pressure monitoring, the frequency of pressing the cuff against the living body increases, so that there is a disadvantage that a heavy burden is imposed on the living body and congestion is reduced. As a result, an accurate blood pressure value cannot be obtained.
[0003]
[Problems to be solved by the invention]
Therefore, based on the fact that the diastolic blood pressure value also changes if an abnormality occurs in the blood pressure value, the diastolic blood pressure value is measured without increasing the compression pressure by the cuff, thereby replacing blood pressure monitoring and thereby burdening the living body. It is thought to reduce. In this way, when no change is found in the diastolic blood pressure value, it can be determined that no abnormality has occurred in the blood pressure value, so that subsequent boosting is unnecessary, and the burden on the living body is reduced.
[0004]
For example, in the so-called K sound method for determining a blood pressure value based on a Korotkoff sound that is generated and disappears according to the cuff compression pressure, the above-mentioned minimum blood pressure value is determined by a microphone sound generated in the process of increasing the cuff pressure. And the cuff pressure when the first K sound is generated is determined as the diastolic blood pressure value. However, in this technique, since a microphone is used to detect the K sound, noise generated in the vicinity may be erroneously determined to be the K sound, and when the pulse of the living body is weak due to a shock state or the like, the K sound is detected. This makes it difficult to obtain high reliability of the diastolic blood pressure value.
[0005]
On the other hand, for example, in an oscillometric method that determines a blood pressure value based on a change state of a magnitude of a pressure pulse wave that changes according to a compression pressure of a cuff, an inflection that occurs in a pressure pulse wave in a process in which the cuff pressure is increased. By detecting the point, the cuff pressure when the inflection point occurs is determined as the diastolic blood pressure value. According to this technique, even when the pulse of the living body is weak, the diastolic blood pressure value can be reliably measured. However, in order to determine the inflection point, it is necessary to increase the cuff pressure to about the average blood pressure value. However, there is a problem that the measurement pressure of the diastolic blood pressure cannot be obtained with a relatively high burden.
[0006]
The present inventors have conducted research based on the above circumstances and found that the cuff is detected at a site downstream of the cuff mounting site. Downstream Pulse wave is constant with cuff pulse wave detected in cuff Noseki There is a clerk, Noseki The clerk found that the cuff pressure changed abruptly after reaching the minimum blood pressure value.
[0007]
The present invention has been made based on such knowledge, and an object of the present invention is to provide a blood pressure monitoring device capable of reducing a burden on a living body and measuring an accurate minimum blood pressure value. .
[0008]
[Means for Solving the Problems]
In order to achieve such an object, the gist of the present invention is to provide a blood pressure measuring device that has a cuff attached to a part of a living body and measures a blood pressure value of the living body by changing a compression pressure by the cuff. Generated from the artery at a site downstream of the artery from the site where the cuff of the living body is attached Downstream A blood pressure monitoring device of a type including a pulse wave sensor for detecting a pulse wave, wherein (a) a cuff pressure increasing means for increasing a compression pressure of the cuff at a predetermined speed, and (b) a pressure cuff generated in the cuff. Cuff pulse wave detecting means for detecting a cuff pulse wave that is a pressure oscillation, and (c) in the process in which the cuff pressure is increased at a predetermined speed by the cuff pressure increasing means, Downstream First peak interval calculating means for calculating a first peak interval which is an interval between an upper peak of the pulse wave and a lower peak following the upper peak, and (d) the first peak interval is calculated. Downstream (E) second peak interval calculation means for calculating a second peak interval which is an interval between an upper peak of the cuff pulse wave generated in synchronization with the pulse wave and a lower peak following the upper peak; A peak interval difference calculating means for calculating a difference between the interval and the second peak interval; and (f) the cuff corresponding to a point at which the rate of change of the peak interval difference calculated by the peak interval difference calculating means changes abruptly. A minimum blood pressure value determining means for determining the pressure as the minimum blood pressure value.
[0009]
[Action]
With this configuration, in the process in which the compression pressure of the cuff is increased at a predetermined speed by the cuff pressure increasing unit, the first peak interval calculation unit performs the operation. Downstream The first peak interval between the upper peak of the pulse wave and the subsequent lower peak was calculated, and the first peak interval was calculated by the second peak interval calculating means. Downstream A second peak interval between the upper peak of the cuff pulse wave generated in synchronization with the pulse wave and the subsequent lower peak is calculated, and the peak interval difference calculating means calculates the difference between the first peak interval and the second peak interval. The difference is calculated. Then, the cuff pressure corresponding to the point at which the rate of change of the peak interval difference calculated by the peak interval difference calculating unit rapidly changes is determined as the diastolic blood pressure value by the diastolic blood pressure value determining means. In other words, the cuff pulse wave changes in synchronization only with the pulse regardless of the change in the cuff compression pressure, Downstream The pulse wave is detected downstream of the cuff artery and is changed in response to changes in both pulse and cuff pressure. For this reason, the rate of change of the peak interval difference suddenly changes when it reaches the diastolic blood pressure value under the influence of the change in the cuff pressure. Downstream With pulse wave Change rate of difference between upper and lower peak intervals The diastolic blood pressure value can be determined based on the
[0010]
【The invention's effect】
As described above, since the minimum blood pressure value is determined when the compression pressure is relatively low in the process of increasing the cuff pressure, the burden on the living body when monitoring the blood pressure is reduced. Moreover, since the peak interval difference is calculated based on the cuff pulse wave, for example, even when a physiological change such as arrhythmia occurs, the difference between the cuff pulse wave and the cuff pulse wave is obtained. Downstream The pulse wave is similarly varied without affecting the peak interval difference, and the diastolic blood pressure value is measured more accurately. Also, the above Downstream For the pulse wave, a pulse wave detected for measurement by a pulse wave sensor attached to the living body for another purpose different from blood pressure monitoring can be used, so that the minimum blood pressure value can be obtained without imposing a particular burden on the living body. Can be measured. Although the pulse wave sensor is attached to a part of the artery downstream of the part where the cuff of the living body is attached, in a normal blood pressure monitoring state, the compression pressure of the cuff is increased only to about the minimum blood pressure value and almost blood pressure is not increased. Since the flow is not obstructed, the measurement by the pulse wave sensor is hardly interrupted.
[0011]
Here, preferably, the blood pressure monitoring device has a cuff attached to a part of a living body, and a blood pressure value measuring unit that measures a blood pressure value of the living body by changing a compression pressure by the cuff, A pressure pulse wave sensor for detecting a pressure pulse wave generated from an artery at a site downstream of the artery by being pressed to a site downstream of the artery from a site where the cuff of the living body is mounted, and the pressure pulse wave sensor Determination means for determining in advance the correspondence between the magnitude of the pressure pulse wave detected by the blood pressure value and the blood pressure value measured by the blood pressure value measurement means, and the pressure detected by the pressure pulse wave sensor from the correspondence. A continuous blood pressure value determining means for continuously determining the blood pressure value of the living body based on the magnitude of the pulse wave; (a) a cuff pressure increasing means for increasing the compression pressure of the cuff at a predetermined speed; b) pressure generated in the cuff Cuff pulse wave detecting means for detecting a cuff pulse wave which is a vibration; and (c) in the process in which the cuff pressure increasing means increases the compression pressure of the cuff at a predetermined speed, the upper peak of the pressure pulse wave and its First peak interval calculating means for calculating a first peak interval which is an interval between a lower peak and an upper peak, and (d) the cuff pulse generated in synchronization with the pressure pulse wave whose first peak interval is calculated. Second peak interval calculating means for calculating a second peak interval which is an interval between an upper peak of the wave and a lower peak following the upper peak, and (e) calculating a difference between the first peak interval and the second peak interval. (F) the pressure of the cuff corresponding to the point at which the rate of change of the peak interval difference calculated by the peak interval difference calculating means changes abruptly, and the continuous blood pressure value determining means. Low blood pressure Zui by, and determining relationship determining means for appropriateness of the determined correspondence relationship by the relationship determining means, is intended to include.
[0012]
According to this configuration, in the process in which the cuff pressure is increased at a predetermined speed by the cuff pressure increasing unit, the first peak interval calculating unit sets the interval between the upper peak of the pressure pulse wave and the lower peak following it. The first peak interval is calculated, and the second peak interval calculating means calculates the interval between the upper peak of the cuff pulse wave generated in synchronization with the pressure pulse wave whose first peak interval is calculated and the lower peak following it. A second peak interval is calculated, and a difference between the first peak interval and the second peak interval is calculated by a peak interval difference calculating unit. Then, based on the pressure of the cuff corresponding to the point at which the rate of change of the peak interval difference calculated by the peak interval difference calculating means sharply changes and the diastolic blood pressure value determined by the continuous blood pressure value determining means, Suitability of the correspondence determined by the relationship determining means is determined by the relationship determining means.
[0013]
As described above, when the correspondence determined by the relationship determining unit is determined to be appropriate by the relationship determining unit, it is not necessary to execute the calibration at that time. Therefore, the burden on the living body due to the compression of the cuff for calibration is eliminated, and the continuous blood pressure is applied even when the pressure pulse wave sensor is attached to a part of the living body downstream of the part where the cuff is attached. The blood pressure monitoring by the value determining means is not interrupted. In addition, when the appropriateness of the correspondence is judged by the relation judging means, the compression pressure is not increased above the minimum blood pressure value, so that the burden on the living body due to the compression of the cuff at that time hardly occurs.
[0014]
Incidentally, as an alternative to blood pressure monitoring by compression of the cuff, for example, as described in Japanese Patent Application Laid-Open No. 1-214338, etc. A pressure pulse wave sensor that detects a pressure pulse wave generated from an artery at the site by being pressed by a wrist or the like of a living body, and a pressure pulse wave between the magnitude of the pressure pulse wave and the blood pressure value measured by the blood pressure measurement unit. A relationship determining means for determining a correspondence in advance, and a continuous blood pressure value determining means for continuously determining a blood pressure value of a living body based on the magnitude of the pressure pulse wave from the correspondence, a blood pressure of the type described above. Measurement devices are known. According to this technique, once the correspondence is determined, the blood pressure value is continuously determined based on the pressure pulse wave, so that the burden on the living body when monitoring the blood pressure is reduced.
[0015]
However, since it is inevitable that the pressure state of the pressure pulse wave sensor with respect to the artery changes due to body movements and the like of the living body in the above technique, in order to increase the accuracy of the blood pressure value determined by the continuous blood pressure value determining means, Calibration for updating the correspondence is performed periodically. In this calibration, the blood pressure value is measured in a process in which the compression pressure of the cuff is changed in a predetermined procedure by the blood pressure value measurement means, and the blood pressure value obtained by the measurement and the pressure value are measured when the measurement is performed. The correspondence with the magnitude of the pressure pulse wave detected by the pulse wave sensor is newly determined by the relation determining means. Therefore, even if the above-described technique periodically applies a burden to the living body due to compression of the cuff, and when the pressure pulse wave sensor is attached to a portion downstream of the portion where the cuff of the living body is attached, However, there is a disadvantage that the blood pressure monitoring by the continuous blood pressure value determining means is interrupted during the execution period of the calibration, and this becomes more remarkable as the calibration execution cycle is shortened in order to increase the accuracy of the blood pressure monitoring. is there.
[0016]
Also, preferably, the said Downstream The pulse wave is a photoelectric pulse wave detected based on a change in transmitted light amount or reflected light amount of light applied to the surface of the living body. In this way, for example, by utilizing the photoplethysmogram detected at the time of measurement of peripheral circulatory dynamics and blood oxygen saturation, the diastolic blood pressure value is measured without imposing a burden on the living body due to the cuff compression. It is possible.
[0017]
Incidentally, when blood pressure monitoring is required, other functions of the circulatory system, such as peripheral circulatory dynamics and blood oxygen saturation, are often measured at the same time. Measurement of peripheral circulatory dynamics can be performed, for example, by measuring arterial pulsation occurring in synchronization with a respiratory cycle by artificial respiration, as described in Japanese Patent Application Laid-Open No. HEI 5-115445 filed by the present applicant. Is performed by detecting a temporary change in the time, and detecting a delay time of the occurrence of the temporary change with respect to a predetermined reference time in one cycle of the artificial respiration. The pulsation is performed as a photoelectric pulse wave. It is possible to detect. Further, the measurement of blood oxygen saturation is carried out, for example, as described in Japanese Patent Application Laid-Open No. 50-128387, by utilizing the fact that the absorbance changes due to the pulsation of the artery, to measure oxyhemoglobin and reduced hemoglobin. For each of the two wavelengths having different absorbances, the ratio of the extinction coefficient at each wavelength is determined, and the calculation is performed based on the proportional relationship between the extinction coefficient ratio and the blood oxygen saturation. Will be detected. Therefore, by detecting the photoplethysmogram for these measurements on the downstream side of the artery at the site where the cuff of the living body is wound, this is used to determine the diastolic blood pressure value. Downstream It can be used as a pulse wave.
[0018]
【Example】
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0019]
(First embodiment)
FIG. 1 is a diagram showing an example of the configuration of a blood pressure monitoring device according to the present invention, and is used, for example, to monitor the condition of a patient during or after an operation. In the drawing, reference numeral 10 denotes a cuff having a rubber bag in a cloth band-shaped bag, which is attached, for example, in a state of being wound around the upper arm 12 of a patient. A pressure sensor 14, a switching valve 16, and an air pump 18 are connected to the cuff 10 via a pipe 20, respectively. The switching valve 16 has three pressure supply states: a pressure supply state that allows the supply of pressure into the cuff 10, a slow discharge state that gradually discharges the cuff 10, and a rapid discharge state that rapidly discharges the cuff 10. It is configured to be able to switch to the state.
[0020]
The pressure sensor 14 detects the pressure in the cuff 10 and supplies a pressure signal SP representing the pressure to the static pressure discrimination circuit 22 and the pulse wave discrimination circuit 24, respectively. The static pressure discriminating circuit 22 includes a low-pass filter, discriminates a cuff pressure signal SK representing a steady pressure included in the pressure signal SP, and converts the cuff pressure signal SK through an A / D converter 26 to a control device 28. Supply to The pulse wave discrimination circuit 24 includes a band-pass filter, and a pulse wave signal SM which is a vibration component of the pressure signal SP. ₁ Pulse wave signal SM ₁ Is supplied to the control device 28 via the A / D converter 30. This pulse wave signal SM ₁ Is a pressure vibration wave generated from an unshown brachial artery and transmitted to the cuff 10 in synchronization with the heartbeat of the patient, and the pulse wave discrimination circuit 24 functions as a cuff pulse wave detecting means. I have.
[0021]
The control device 28 includes a so-called microcomputer including a CPU 29, a ROM 31, a RAM 33, and an I / O port (not shown). The CPU 29 uses a storage function of the RAM 33 in accordance with a program stored in the ROM 31 in advance. While executing the signal processing, a drive signal is output from the I / O port to control the switching valve 16 and the air pump 18 via a drive circuit (not shown). In measuring blood pressure using the cuff 10 for calibration, for example, the pressure in the cuff 10 is rapidly increased to a predetermined target pressure, and then gradually reduced at a speed of about 3 mmHg / sec. Pulse wave signal SM sequentially sampled ₁ The blood pressure values such as the systolic blood pressure value and the diastolic blood pressure value are determined by the oscillometric method on the basis of the change of the pulse wave represented by.
[0022]
The pressure pulse wave detection probe 34 is attached to the upper arm 12 of the patient on the downstream side of the artery to which the cuff 10 is attached, by the wearing band 40 with the open end of the housing 36 having a container shape facing the body surface 38. It is configured to be detachably attached to the wrist 42. Inside the housing 36, a pressure pulse wave sensor 46 is provided via a diaphragm 44 so as to be relatively movable and protrudable from an open end of the housing 36, and a pressure chamber 48 is formed by the housing 36, the diaphragm 44, and the like. Have been. The pressure chamber 48 is supplied with pressurized air from an air pump 50 via a pressure regulating valve 52, whereby the pressure pulse wave sensor 46 applies a pressing force P corresponding to the pressure in the pressure chamber 48. _HD Is pressed against the body surface 38.
[0023]
The pressure pulse wave sensor 46 is configured by arranging a large number of semiconductor pressure-sensitive elements (not shown) on a pressing surface 54 of a semiconductor chip made of, for example, single crystal silicon. By being pressed onto the radial artery 56, a pressure vibration wave, ie, a pressure pulse wave generated from the radial artery 56 and transmitted to the body surface 38 is detected, and a pressure pulse wave signal SM representing the pressure pulse wave is detected. ₂ Is supplied to the control device 28 via the A / D converter 58. The upper waveform in FIG. 2 shows an example of the pressure pulse wave detected by the pressure pulse wave sensor 46.
[0024]
The CPU 29 of the control device 28 executes signal processing using the storage function of the RAM 33 according to a program stored in the ROM 31 in advance, and outputs a drive signal to the air pump 50 and the pressure regulating valve 52 via a drive circuit (not shown). The pressure in the pressure chamber 48 is adjusted. When monitoring the blood pressure, the optimum pressing force P of the pressure pulse wave sensor 46 is determined based on the pressure pulse waves sequentially obtained in the process of slowly changing the pressure in the pressure chamber 48. _HDO Is determined, and the pressure regulating valve 52 is set to the optimum pressing force P of the pressure pulse wave sensor 46. _HDO And the systolic blood pressure value BP measured using the cuff 10 is controlled. _SYS And diastolic blood pressure BP _DIA And the optimal pressing force P _HDO Is maintained, the maximum value P of the pressure pulse wave detected by the pressure pulse wave sensor 46 is maintained. _M2max And the lowest value P _M2min Value BP measured on the basis of the pressure and the magnitude P of the pressure pulse wave _M (Absolute value), and from this correspondence, the magnitude P of the pressure pulse wave sequentially detected by the pressure pulse wave sensor 46 is obtained. _M That is, the highest value (upper peak value) P _M2max And the lowest value (lower peak value) P _M2min Blood pressure value MBP based on _SYS And diastolic blood pressure MBP _DIA (Monitor blood pressure value) is sequentially determined, and the determined monitor blood pressure value MBP is displayed on the display 32.
[0025]
The above correspondence is, for example, as shown in FIG. _M It is represented by + B. Here, A is a constant indicating the slope, and B is a constant indicating the intercept.
[0026]
FIG. 4 is a functional block diagram illustrating a main part of the control function of the control device 28 in the blood pressure monitoring device configured as described above. In the figure, the pressure of the cuff 10 is detected by a pressure sensor 14. The blood pressure value measuring means 72 measures the blood pressure value of the patient by changing the pressure applied by the cuff 10. The pressure pulse wave sensor 46 detects a pressure pulse wave generated from an artery at a site downstream of the artery by being pressed to a site downstream of the artery from a site where the cuff 10 of the patient is mounted. The relationship determining means 74 previously determines the correspondence between the magnitude of the pressure pulse wave detected by the pressure pulse wave sensor 46 and the blood pressure value measured by the blood pressure value measuring means 72. The continuous blood pressure value determining means 76 continuously determines the patient's blood pressure value based on the magnitude of the pressure pulse wave detected by the pressure pulse wave sensor 46 from the correspondence.
[0027]
On the other hand, the cuff pressure increasing means 78 increases the compression pressure of the cuff 10 continuously or stepwise at a predetermined speed. The first peak interval calculating means 80 and the second peak interval calculating means 82 determine the pressure pulse detected by the pressure pulse wave sensor 46 during the process of increasing the compression pressure of the cuff 10 at a predetermined speed by the cuff pressure increasing means 78. The interval between the upper peak of the wave and the subsequent lower peak (first peak interval), and the difference between the upper peak of the cuff pulse wave detected by the cuff pulse wave detecting means (pulse wave discrimination circuit 24) and the lower peak following the cuff pulse wave The intervals (second peak intervals) are calculated respectively. The peak interval difference calculating means 84 calculates the difference (peak interval difference) between the first peak interval and the second peak interval calculated by the first peak interval calculating means 80 and the second peak interval calculating means 82, respectively. The relationship determining means 86 determines the pressure of the cuff 10 corresponding to the point K at which the calculated change rate of the peak interval difference has changed abruptly, and the latest diastolic blood pressure value determined by the continuous blood pressure value determining means 76. Then, the appropriateness of the correspondence determined by the relationship determining means 74 is determined.
[0028]
FIG. 5 is a flowchart illustrating a main part of the control operation of the control device 28. In step S1 in the figure (hereinafter, the steps are omitted), the pressure in the pressure chamber 48 is gradually increased, and the pressure pulse wave sequentially detected by the pressure pulse wave sensor 46 in the process of gradually increasing the pressure in the pressure chamber 48. In the pressure chamber 48 at which the amplitude of the pressure becomes maximum, that is, the optimum pressing force P of the pressure pulse wave sensor 46. _HDO Is determined, and the pressure in the pressure chamber 48 is adjusted to its optimum pressing force P. _HDO , The pressing force of the pressure pulse wave sensor 46 is held at an optimal constant value. In the present embodiment, the air pump 50, the pressure regulating valve 52, and the step S1 (more precisely, the portion of the CPU 29, the ROM 31, and the RAM 33 used to execute the step S1) correspond to the pressing force adjusting means. I do.
[0029]
In subsequent S2, it is determined whether or not the correspondence shown in FIG. 3 has already been determined for the patient wearing the cuff 10. If the determination in S2 is affirmed, the correspondence suitability determination routine for determining the suitability of the correspondence is executed in S3 to S8. However, the determination in S2 is initially denied, so the blood pressure measurement by the cuff 10 Is performed, and S9 and subsequent steps are performed. First, in S9 corresponding to the blood pressure value measuring means 72, the switching valve 16 is switched to the pressure supply state and the air pump 18 is operated to increase the pressure in the cuff 10 to a target pressure higher than the expected maximum blood pressure value of the patient. (E.g., 180 mmHg), the air pump 18 is stopped, and the switching valve 16 is switched to a slow exhaust pressure state to lower the pressure in the cuff 10 at a predetermined gentle speed. Pulse wave signal SM obtained successively in the step-down process ₁ Based on the change in the amplitude of the pulse wave represented by the blood pressure value BP according to the well-known oscillometric blood pressure value determination algorithm. _SYS , Mean blood pressure BP _Mean , And diastolic blood pressure BP _DIA Is measured, and the pulse rate and the like are determined based on the pulse wave interval. Then, the measured blood pressure value, the pulse rate, and the like are displayed on the display 32, and the switching valve 16 is switched to the rapid exhaust pressure state, so that the pressure in the cuff 10 is quickly exhausted.
[0030]
Next, in S10 corresponding to the relation determining means 74, the magnitude of the pressure pulse wave from the pressure pulse wave sensor 46 (absolute value, that is, the pulse wave signal SM ₂ Size) and the blood pressure value BP by the cuff 10 measured in the above S9 _SYS , BP _DIA Is required. That is, one pulse of the pressure pulse wave from the pressure pulse wave sensor 46 is read and the maximum value P of the pressure pulse wave is read. _M2max And the lowest value P _M2min Is determined, and the maximum value P of the pressure pulse waves is determined. _M2max And the lowest value P _M2min And BP measured by cuff 10 in S9 _SYS And diastolic blood pressure BP _DIA Thus, the correspondence between the magnitude of the pressure pulse wave and the blood pressure value shown in FIG. 3 is determined.
[0031]
When the correspondence is determined as described above, the blood pressure monitoring routine is executed in S11 and subsequent steps. First, it is determined in S11 whether one pulse wave has been input. If the determination in S11 is denied, the process waits until one pulse wave is input. However, if the determination in S11 is affirmed, in S12 corresponding to the continuous blood pressure value determination unit 76, Optimal pressing force P _HDO The maximum value P of the pressure pulse wave from the pressure pulse wave sensor 46 at _M2max And the lowest value P _M2min Is determined. Next, at S13, the maximum value P of the pressure pulse wave determined at S12 is obtained from the correspondence obtained at S10. _M2max And the lowest value P _M2min Blood pressure value MBP based on _SYS And diastolic blood pressure MBP _DIA (Monitor blood pressure value) is determined, and the determined monitor blood pressure value is displayed on the display 32 together with the continuous waveform of the pressure pulse wave.
[0032]
Next, in S14, it is determined whether or not the elapsed time since the blood pressure measurement by the cuff 10 in the above-described step S9 has passed a preset set period of about 10 to 20 minutes. If the determination in S14 is negative, the blood pressure monitoring routine in S11 and subsequent steps is repeatedly executed, and the systolic blood pressure value MBP _SYS And diastolic blood pressure MBP _DIA Is determined and displayed continuously for each beat. However, if the determination in S14 is affirmed, the above-described S2 and subsequent steps are executed again.
[0033]
In the control cycle after the correspondence is once determined as described above, the determination in S2 is affirmative, and the cuff 10 is set to a predetermined pressure of about 5 to 20 mmHg / sec by S3 corresponding to the cuff pressure increasing means 78. Pressure rises from atmospheric pressure at a speed. Next, in S4 corresponding to the first peak interval calculating means 80 and the second peak interval calculating means 82, the pressure pulse waves and the cuff pulse waves shown in the upper and lower parts of FIG. Upper peak P _M2max And lower peak P _M2min Distance D _i (Where i = 1, 2,...) Is calculated and the interval D _i Is the upper peak P of the cuff pulse wave generated in synchronization with the calculated pressure pulse wave _M1max And lower peak P _M1min Distance d _i Is calculated. Then, in step S5 corresponding to the peak interval difference calculating means 84, two peak intervals D _i , D _i Difference t _i (= D _i -D _i ) (Msec) is calculated, and in step S6, the peak interval difference t that changes with the pressure increase of the cuff 10 as shown in FIG. _i It is determined whether or not a change point K at which the change rate of changes abruptly occurs, by comparing with the change rate immediately before.
[0034]
The peak interval difference t _i Is caused when the low pressure side of the pressure wave propagating from the cuff 10 to the downstream side is cut off by the compression of the cuff 10, and the change point K occurs in accordance with the diastolic blood pressure value. Initially, the determination of S6 is denied, so that S3 and subsequent steps are executed. If the determination of S6 is affirmed during the execution of those steps, the peak interval difference t is determined in S7. _i Pressure P at the time of detecting a change point K at which the rate of change of the temperature has rapidly changed _CD1 Is stored. This cuff pressure P _CD1 Is equivalent to the actual diastolic blood pressure value. In the present embodiment, S7 corresponds to diastolic blood pressure value determining means.
[0035]
Then, in S8 corresponding to the relation determining means 82, the latest diastolic blood pressure value MBP calculated in S13 is obtained. _DIA And the cuff pressure P at the time of detection of the change point K stored in S7 _CD1 (That is, the diastolic blood pressure BP _DIA ), The suitability of the correspondence determined in S10 is determined. That is, the minimum blood pressure value MBP _DIA And the cuff pressure P when the change point K is detected _CD1 Difference with MBP _DIA -P _CD1 | Is a preset judgment reference value ΔP ₁ It is determined whether or not: This determination reference value ΔP ₁ Is the continuously determined diastolic blood pressure value MBP _DIA Blood pressure value BP measured by cuff 10 _DIA And is set to, for example, about 5 mmHg. However, the diastolic blood pressure value BP measured by the cuff 10 _DIA And the cuff pressure P when the change point K is detected _CD1 When the difference is recognized, the judgment reference value ΔP is determined by the difference. ₁ Is corrected in advance.
[0036]
If the determination in S8 is affirmative, the blood pressure measurement by the cuff 10 and the update of the correspondence are unnecessary, so that the blood pressure monitoring routine of S11 and subsequent steps is directly performed without executing S9 and S10. Be executed. However, if the determination in S8 is denied, the correspondence is inappropriate, so that S9 and S10 are executed to update the correspondence, and then the blood pressure monitoring routine of S11 and subsequent steps is executed.
[0037]
As described above, according to the present embodiment, the first peak interval calculating unit 80 and the second peak interval are used in the process of increasing the compression pressure of the cuff 10 at a predetermined speed by S3 corresponding to the cuff pressure increasing unit 78. By S4 corresponding to the calculating means 82, the upper peak P of the pressure pulse wave is obtained. _M2max Followed by the lower peak P _M2min The first peak interval D between _i , And the upper peak P of the cuff pulse wave _M1max Followed by the lower peak P _M1min The second peak interval d between _i Are calculated, and the first peak interval D is calculated by S5 corresponding to the peak interval difference calculating means 84. _i And the second peak interval d _i And the difference t _i Is calculated. Then, the peak interval difference t calculated in S5 _i Of the cuff 10 when a change point K at which the rate of change of the temperature changes rapidly is detected. _CD1 Is the diastolic blood pressure BP _DIA And the pressure P _CD1 And the latest diastolic blood pressure value MBP determined in S13 corresponding to the continuous blood pressure value determining means 76 _DIA Based on the above, the appropriateness of the correspondence determined in S13 corresponding to the relationship determining means 74 is determined by S8 corresponding to the relationship determining means 86.
[0038]
Accordingly, when the correspondence determined in S10 is determined to be appropriate in S8, the execution of the calibration at that time becomes unnecessary, and the patient presses the cuff 10 for calibration. And the blood pressure monitoring by the continuous blood pressure value determining means 76 is interrupted even when the pressure pulse wave sensor 46 is mounted on a portion of the patient downstream of the cuff 10. Never.
[0039]
The cuff pulse wave changes in synchronization with only the pulse and is not affected by the change in the compression pressure of the cuff 10. On the other hand, since the pressure pulse wave is detected downstream of the cuff 10, the pulse and the compression Is changed in response to both changes. Therefore, the peak interval difference t _i Of the cuff 10 corresponding to the point K at which the rate of change rapidly changes is the minimum blood pressure value MBP. _DIA Is equivalent to Therefore, when it is determined in S8 that the correspondence is appropriate, the compression pressure is increased to about the minimum blood pressure value, and the pressure on the cuff 10 at this time hardly burdens the patient. Moreover, the peak interval difference t _i Is calculated on the basis of the cuff pulse wave. Therefore, even when a physiological change such as arrhythmia occurs, the cuff pulse wave and the pressure pulse wave are similarly changed, and the peak interval difference t _i Does not have that effect. Therefore, the determination of the appropriateness of the correspondence is made more accurately.
[0040]
Further, according to the present embodiment, in S8, the latest diastolic blood pressure value MBP determined in S13. _DIA And peak interval difference t _i Of the cuff 10 when a change point K at which the rate of change of the temperature changes rapidly is detected. _CD1 Is determined based on the minimum blood pressure value MBP _DIA Alternatively, the diastolic blood pressure value BP measured in S9 _DIA There is an advantage that the determination accuracy can be further enhanced as compared with the case where is used.
[0041]
Next, another embodiment of the present invention will be described. In the following embodiments, portions common to the above-described embodiments are denoted by the same reference numerals, and detailed description will be omitted.
[0042]
(Second embodiment)
FIG. 7 shows a photoelectric pulse wave detection probe 88 (hereinafter simply referred to) instead of the pressure pulse wave detection probe 34 of the above-described embodiment for performing blood pressure measurement and measuring blood oxygen saturation using a pulse oximeter. FIG. 3 is a diagram illustrating an apparatus configuration when a probe is used. The probe 88 is attached, for example, in close contact with the body surface 38 of the upper arm 12 on the downstream side of the artery on which the cuff 10 of the patient is attached, using an attachment band (not shown). The probe 88 is provided in a container-like housing 92 that opens in one direction, and a plurality of first light-emitting elements 94a and second light-emitting elements 94b that are provided on a portion located on the outer peripheral side of the bottom inner surface of the housing 92. (Hereinafter, simply referred to as a light emitting element 94 unless otherwise specified), a light receiving element 96 formed of a photodiode, a phototransistor, or the like provided at the center of the bottom inner surface of the housing 92, and integrally provided in the housing 92. And a transparent resin 98 covering the light emitting element 94 and the light receiving element 96, and provided between the light emitting element 94 and the light receiving element 96 in the housing 92, for transmitting light emitted from the light emitting element 94 toward the body surface 38. An annular shielding member 100 for shielding the reflected light from the body surface 38 toward the light receiving element 96 is provided.
[0043]
The first light emitting element 94a emits red light having a wavelength of, for example, about 660 nm, and the second light emitting element 94b emits infrared light having a wavelength of, for example, about 800 nm. The first light emitting element 94a and the second light emitting element 94b emit light at a predetermined frequency in order for a predetermined time, and thin blood vessels in the body of light emitted from the light emitting element 94 toward the body surface 38 are densely packed. The reflected light from the part where the light is reflected is received by the common light receiving element 96. Note that the wavelengths of the light-emitting elements 94a and 94b are not limited to the above values. Any material that emits light may be used.
[0044]
The light receiving element 96 has a photoelectric pulse wave signal SM having a magnitude corresponding to the amount of received light. ₃ Is output through the low-pass filter 102. An amplifier and the like are appropriately provided between the light receiving element 96 and the low-pass filter 102. The low-pass filter 102 receives the input electric signal SM ₃ , A noise having a frequency higher than the frequency of the pulse wave is removed from the signal SM. ₃ Is output to the demultiplexer 104. The demultiplexer 104 is switched in synchronization with the light emission of the first light emitting element 94a and the second light emitting element 94b according to a signal from the control device 28, so that the electric signal SM of red light _R Via the sample-and-hold circuit 106 and the A / D converter 58, the electric signal SM by infrared light _IR Are sequentially supplied to an I / O port (not shown) of the control device 28 via the sample hold circuit 108 and the A / D converter 110. The sample and hold circuits 106 and 106 receive the input electric signal SM _R , SM _IR Are sequentially output to the A / D converters 58 and 110, the previously output electric signal SM _R , SM _IR Until the conversion operation in the A / D converters 58 and 110 is completed. _R , SM _IR Are respectively held. In the present embodiment, the probe 88 corresponds to a pulse wave sensor.
[0045]
The control device 28 is connected to the A / D converter 26, the display 32, and the like on the cuff 10 side as in the above-described embodiment, but the air pump 50 and the pressure regulating valve 52 are unnecessary. Not provided.
[0046]
The CPU 29 of the control device 28 executes the measurement operation according to the program stored in the ROM 31 in advance while utilizing the storage function of the RAM 33, and controls the switching valve 16 and the air pump 18 in the same manner as in the above-described embodiment, while performing the cuff operation. Cuff pressure signal SK and pulse wave signal SM detected from ₁ And causes the display 32 to display the blood pressure value. Further, the control circuit 28 outputs a control signal SLV to the drive circuit 112 to cause the light emitting elements 94a and 94b to sequentially emit light at a predetermined frequency for a certain period of time, while synchronizing with the light emission of the light emitting elements 94a and 94b. By outputting SC and switching the demultiplexer 104, the electric signal SM _R Is supplied to the sample and hold circuit 106 by the electric signal SM. _IR To the sample and hold circuit 108.
[0047]
Further, the CPU 29 executes the electric signal SM according to a program stored in advance. _R , SM _IR The oxygen saturation in blood is determined based on the photoplethysmographic waveforms represented by. The method for determining the oxygen saturation is the same as the method described in, for example, Japanese Patent Application Laid-Open No. 3-15440 filed by the present applicant. _dR -V _SR ) / (V _dR + V _SR )｝ / ｛(V _dIR -V _SIR ) / (V _dIR + V _SIR The oxygen saturation is determined based on the actual ratio from the previously determined relationship between the ratio indicated by｝ and the oxygen saturation. In the above equation, V _dR , V _SR Are the upper peak value and the lower peak value of the photoelectric pulse waveform due to red light, respectively. _dIR , V _SIR Are the upper peak value and the lower peak value of the photoelectric pulse waveform due to the infrared light, respectively. Also, V _dR -V _SR And V _dIR -V _SIR Represents the amplitude of the AC component of each photoplethysmographic waveform. _dR + V _SR And V _dIR + V _SIR Represents the doubled DC component of each photoplethysmographic waveform. The photoplethysmogram draws a curve similar to the pressure pulse wave shown in the upper part of FIG.
[0048]
FIG. 8 is a functional block diagram illustrating a main part of the control function of the control device 28 in the blood pressure monitoring device configured as described above, and is a diagram corresponding to FIG. 4 in the above-described embodiment. In the figure, the oxygen saturation determining means 114 determines the blood oxygen saturation based on the photoplethysmogram detected by the probe 88. On the other hand, in the process of increasing the cuff pressure at a predetermined speed by the cuff pressure increasing means 78 in the same manner as in the above-described embodiment, the first peak interval calculating means 80 calculates the first peak from the photoelectric pulse wave detected by the probe 88. The second peak interval is calculated by the second peak interval calculating means 82 from the cuff pulse wave detected by the cuff pulse wave detecting means (pulse wave discriminating circuit 24), and the peak interval is calculated by the peak interval difference calculating means 84. An interval difference t is calculated. Then, the cuff pressure P corresponding to the point K at which the rate of change of the peak interval difference t shown in FIG. _CD1 Is the diastolic blood pressure BP _DIA Is determined as
[0049]
FIG. 9 shows the control operation of the control device 28 according to the present embodiment. _DIA 5 is a flowchart for explaining a main part related to the determination of FIG. In S15, the photoelectric pulse wave detected by the probe 88 is sequentially input. This photoplethysmogram is detected for measurement of blood oxygen saturation. When read by the CPU, the blood oxygen saturation is determined as described above (not shown in the flowchart). The processing is performed according to the flowchart of FIG. In S16, it is determined whether or not a preset measurement cycle of the diastolic blood pressure value has elapsed. This measurement cycle is appropriately set according to the cycle at which blood pressure monitoring is desired. If this determination is denied, the process returns to S15 and the photoelectric pulse wave is input again. However, if it is determined that the set period has elapsed, S3 to S6 similar to those in the above-described embodiment are executed. Steps S3 to S6 are the same as those described above except that a photoelectric pulse wave is used instead of a pressure pulse wave, and a description thereof will be omitted.
[0050]
If the change point K is detected and the determination in S6 is affirmed, the process proceeds to S17 and the cuff pressure P at the time when the change point K is detected. _CD1 Is the diastolic blood pressure BP _DIA And the minimum blood pressure value BP is determined in S18. _DIA Is displayed on the display 32. Then, in S19 corresponding to the blood pressure value abnormality determination means, the minimum blood pressure value BP _DIA If it is determined that the change with respect to the previous measurement value is larger than a predetermined criterion value centered on, for example, the moving average value, the display 32 continuously displays an abnormal blood pressure value in S20, and In S21, it is determined whether or not a blood pressure measurement shortest period set separately from the above-described minimum blood pressure measurement period has elapsed. The shortest period of the blood pressure measurement is set to a value equal to or longer than the shortest period of the blood pressure measurement (for example, 2 minutes and 30 seconds) defined by WHO. If the determination in S21 is denied, the process returns to S16 and the measurement of the diastolic blood pressure value is continued in a state where the abnormal blood pressure value is displayed. However, if the determination is affirmative, the process proceeds to S9 to continue increasing the cuff pressure. By doing so, the systolic blood pressure value BP is _SYS Are determined and displayed. Then, the process returns to S16, and the monitoring of the diastolic blood pressure value is continued.
[0051]
Also in this embodiment, the first peak interval D in S5 is the same as in the above-described embodiment except that a photoelectric pulse wave is used instead of the pressure pulse wave. _i And the second peak interval d _i And the difference t _i Is calculated, and the peak interval difference t is calculated in S6. _i A change point K at which the rate of change of the change of the abruptly changes is detected. Then, the cuff pressure P when this change point K is detected in S17. _CD1 Is the diastolic blood pressure BP _DIA Is determined and displayed, and the diastolic blood pressure value BP is determined in S19. _DIA Is determined based on the amount of change in the blood pressure value.
[0052]
Accordingly, when it is determined that the blood pressure value is not abnormal, the cuff pressure is increased thereafter, and the systolic blood pressure value BP is increased. _SYS Thus, the blood pressure monitoring is performed without imposing a burden on the patient due to the pressure of the cuff 10 for measuring the blood pressure. That is, according to the present embodiment, the pulse detected for the measurement by the photoelectric pulse wave detection probe 88 attached to the patient for another purpose different from the blood pressure monitoring, that is, the measurement of the oxygen saturation. By using waves, the diastolic blood pressure can be measured without imposing a particular burden on the patient.
[0053]
In addition, the probe 88 is attached to a portion of the artery downstream of the portion where the cuff 10 of the patient is attached, but in a normal blood pressure monitoring state, the compression pressure of the cuff 10 is increased only to about the minimum blood pressure value and almost not. The measurement of oxygen saturation by the probe 88 is hardly interrupted so as not to obstruct the blood flow.
[0054]
In addition, when it is determined that the blood pressure value is abnormal, the display is displayed on the display 32, and the blood pressure value is determined according to the normal blood pressure measurement procedure. It is possible to take action by knowing the blood pressure value. Further, in this case, it is determined whether or not the shortest period of the blood pressure measurement has elapsed in S21 prior to the blood pressure measurement. Therefore, when the blood pressure value is abnormal, the blood pressure measurement is frequently performed and the patient is excessively measured. It does not impose the burden of.
[0055]
As mentioned above, although one Example of this invention was described based on drawing, this invention is applied also to another aspect.
[0056]
For example, the above-described blood pressure value measuring means 72 is configured to determine the blood pressure value based on a change state of the magnitude of the pressure pulse wave that changes according to the compression pressure of the cuff 10 according to a so-called oscillometric method. However, according to the so-called Korotkoff sound method, the blood pressure value may be determined based on the Korotkoff sound that is generated and disappears with the compression pressure of the cuff 10.
[0057]
Further, in the relation determining means 86 of the first embodiment, the latest diastolic blood pressure value MBP determined by the continuous blood pressure _DIA Or MBP _Mean Was used, but the diastolic blood pressure value MBP determined by the latest few beats _DIA Or MBP _Mean May be used. In this way, the influence of an abnormal value due to body movement or the like can be reduced.
[0058]
In the blood pressure monitoring device of the first embodiment, the calibration is performed when the elapsed time from the execution of the blood pressure measurement in step S9 elapses a preset cycle. A determination step is provided for determining whether or not the blood pressure value MBP determined by the means 76 has changed abnormally. If the determination step determines that the blood pressure value MBP has changed abnormally, S9 and subsequent steps are executed. May be configured.
[0059]
Further, in the above-described embodiment, the case where the cuff 10 is attached to the upper arm 12 of the patient has been described, but a cuff 10 attached to, for example, a wrist may be used.
[0060]
In the second embodiment, when it is determined in step S19 that the change in the diastolic blood pressure value is larger than a predetermined reference value centered on the moving average value, the occurrence of an abnormality is displayed in S20. At the same time, the normal blood pressure measurement is configured to be performed in S9. However, the configuration may be such that S9 is omitted and the presence or absence of an abnormality is simply displayed, and conversely, S20 is omitted and an abnormality occurs. It may be configured that only the execution of the blood pressure measurement is performed without displaying in such a case. In addition, the above-mentioned criterion value is determined centering on the moving average value and is also determined as appropriate.
[0061]
In the second embodiment, if the set cycle of step S16 is longer than the shortest cycle (for example, 2 minutes and 30 seconds) required to maintain the blood pressure measurement accuracy, the elapse of the shortest cycle of blood pressure measurement in S21 is performed. Is unnecessary, and S9 may be executed whenever an abnormal blood pressure value occurs.
[0062]
Further, in the second embodiment, the reflection-type photoelectric pulse wave detecting probe 88 for detecting the reflected light reflected on the body surface 38 of the living body is used, but the transmitted light transmitted through the body tissue of the living body is detected. A transmission type photoelectric pulse wave detection probe may be used.
[0063]
As the pulse wave sensor, in addition to the pressure pulse wave sensor 46 and the photoelectric pulse wave detection probe 88 shown in the embodiment, a so-called impedance plethysmo method detects a change in the impedance of a living body due to blood pulsation. An impedance sensor or the like can also be used. In addition, the pulse wave sensor may be used for simply detecting a pulse wave or measuring peripheral circulatory dynamics in addition to the one used for measuring oxygen saturation as shown in the embodiment. .
[0064]
In addition, the present invention can be variously modified without departing from the gist thereof.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a blood pressure monitoring device according to one embodiment of the present invention.
FIG. 2 is a diagram exemplifying a pressure pulse wave detected by a pressure pulse wave sensor and a cuff pulse wave detected by a pulse wave discriminating unit in the embodiment of FIG. 1;
FIG. 3 is a diagram illustrating a correspondence relationship used in the embodiment of FIG. 1;
FIG. 4 is a functional block diagram illustrating a control function of the control device of the embodiment of FIG. 1;
FIG. 5 is a flowchart illustrating a control operation of the control device of the embodiment of FIG. 1;
FIG. 6 is a diagram showing a relationship between a peak interval difference and a cuff pressure.
FIG. 7 is a block diagram showing a main part configuration of a blood pressure monitoring device according to another embodiment of the present invention, and is a diagram corresponding to a part of FIG. 1;
FIG. 8 is a functional block diagram illustrating functions of a control device in the embodiment of FIG. 7;
FIG. 9 is a flowchart illustrating a control operation of the control device of the embodiment of FIG. 7;
[Description of sign]
10: Cuff
46: pressure pulse wave sensor (pulse wave sensor)
72: blood pressure value measuring means
74: relation determining means
76: continuous blood pressure value determining means
78: Cuff pressure increasing means
80: first peak interval calculating means
82: Second peak interval calculating means
84: peak interval difference calculating means
86: Relationship determination means
88: Photoelectric pulse wave detection probe (pulse wave sensor)
116: diastolic blood pressure value determining means

Claims (3)

A blood pressure value measuring means for measuring a blood pressure value of the living body by changing a compression pressure by the cuff, the blood pressure value measuring means having a cuff attached to a part of the living body; A blood pressure monitoring device of a type including a pulse wave sensor that detects a downstream pulse wave generated from an artery at a downstream site,
Cuff pressure increasing means for increasing the compression pressure of the cuff at a predetermined speed,
Cuff pulse wave detecting means for detecting a cuff pulse wave that is a pressure vibration generated in the cuff,
In the process in which the compression pressure of the cuff is increased at a predetermined speed by the cuff pressure increasing means, a first peak interval which is an interval between an upper peak of the downstream pulse wave and a lower peak following the upper peak is calculated. First peak interval calculating means;
A second peak interval for calculating a second peak interval which is an interval between an upper peak of the cuff pulse wave generated in synchronization with the downstream pulse wave for which the first peak interval is calculated and a lower peak following the upper peak; Calculating means;
Peak interval difference calculating means for calculating a difference between the first peak interval and the second peak interval;
Diastolic blood pressure value determining means for determining a pressure of the cuff corresponding to a point at which the rate of change of the peak interval difference calculated by the peak interval difference calculating means changes abruptly as a diastolic blood pressure value. Blood pressure monitoring device. A blood pressure value measuring means for measuring a blood pressure value of the living body by changing a compression pressure by the cuff, the blood pressure value measuring means having a cuff attached to a part of the living body; A pressure pulse wave sensor for detecting a pressure pulse wave generated from the artery at the downstream portion of the artery by being pressed by the downstream portion; and a magnitude of the pressure pulse wave detected by the pressure pulse wave sensor and the blood pressure. Relationship determining means for determining in advance the correspondence between the blood pressure value measured by the value measuring means and the blood pressure of the living body based on the magnitude of the pressure pulse wave detected by the pressure pulse wave sensor from the correspondence. Blood pressure monitoring device of a type comprising continuous blood pressure value determining means for continuously determining the value,
Cuff pressure increasing means for increasing the compression pressure of the cuff at a predetermined speed,
Cuff pulse wave detecting means for detecting a cuff pulse wave that is a pressure vibration generated in the cuff,
Calculating a first peak interval, which is an interval between an upper peak of the pressure pulse wave and a lower peak following the upper peak, in a process in which the compression pressure of the cuff is increased at a predetermined speed by the cuff pressure increasing means. One peak interval calculating means;
A second peak interval calculation for calculating a second peak interval which is an interval between an upper peak of the cuff pulse wave generated in synchronization with the pressure pulse wave for which the first peak interval is calculated and a lower peak following the upper peak; Means,
Peak interval difference calculating means for calculating a difference between the first peak interval and the second peak interval;
The relationship is determined based on the pressure of the cuff corresponding to a point at which the rate of change of the peak interval difference calculated by the peak interval difference calculating means changes abruptly and the diastolic blood pressure value determined by the continuous blood pressure value determining means. A blood pressure monitoring device comprising: a determination unit that determines whether the correspondence determined by the determination unit is appropriate. The blood pressure monitoring device according to claim 1, wherein the downstream pulse wave is a photoelectric pulse wave detected based on a change in a transmitted light amount or a reflected light amount of light emitted toward the surface of the living body.

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