Patent Application
20150201847
This application is based on Japanese Patent Applications No. 2014-008465 filed on Jan. 21, 2014, the contents of which are incorporated herein by reference.
The presently disclosed subject matter relates to an apparatus for evaluating a vascular endothelial function in which avascularization is performed by using a cuff, a pulse wave is detected before and after the avascularization is detected, and a vascular endothelial function is evaluate based on the detected pulse waves.
The assignees of the present application have filed patent applications on apparatuses for evaluating a vascular endothelial function which, similarly with the above, use cuffs, and in which accurate evaluation similar to that obtained in a measurement using an ultrasonic echo system is enabled without using an ultrasonic echo system or the like (see JP-A-2009-273870 and JP-A-2011-056200). In the apparatuses disclosed in the literatures, a vascular endothelial function is evaluated by comparing pulse waves before and after avascularization in place of a measurement in which the change of the vessel diameter before and after avascularization is measured by using an ultrasonic echo system.
According to the apparatuses for evaluating a vascular endothelial function disclosed in JP-A-2009-273870 and JP-A-2011-056200, accurate evaluation of a vascular endothelial function is enabled, but there may be a risk that the amplitude of a pulse wave is varied by influence of respiration and autonomic nerves in addition to an expansion of the vessel diameter caused by avascularization.
The presently disclosed subject matter has been conducted in view of the present status of an apparatus for evaluating a vascular endothelial function which uses cuffs. It is an object of the presently disclosed subject matter to provide an apparatus for evaluating a vascular endothelial in which accurate evaluation of a vascular endothelial function is enabled without being influenced by respiration and autonomic nerves.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the apparatus includes: a first cuff which is to be wrapped around one of right and left upper or lower limbs of a subject; a second cuff which is to be wrapped around one of the right and left upper or lower limbs, the one limb being to be wrapped by the first cuff; a third cuff which is to be wrapped around another one of the right and left upper or lower limbs, the other one limb being opposite to the one limb around which the first cuff and the second cuff are to be wrapped; a cuff pressure controller which controls pressures that are applied to the cuffs, respectively; a cuff pressure detector which, from an output of a pressure sensor connected to the second cuff, and an output of a pressure sensor connected to the third cuff, detects cuff pressures in the respective cuffs; a pulse wave detector which detects respective pulse waves from outputs of the pressure sensors; and an analyzer which analyzes the detected pulse waves to evaluate a vascular endothelial function, the cuff pressure controller controls the cuff pressure of the first cuff to avascularize the upper or lower limb around which the first cuff is wrapped, for a predetermined time period, the pulse wave detector detects a pulse wave corresponding to the second cuff, and a pulse wave corresponding to the third cuff, before and after the avascularization in a state where the cuff pressures of the second and third cuffs are controlled to respective predetermined pressure by the cuff pressure controller, and the analyzer corrects the pulse waves corresponding to the second cuff and detected before and after the avascularization, by the pulse waves corresponding to the third cuff and detected before and after the avascularization, and evaluates the endothelial function based on the corrected pulse waves corresponding to the second cuff.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the apparatus includes: a second cuff which is to be wrapped around one of right and left upper or lower limbs of a subject; a third cuff which is to be wrapped around another one of the right and left upper or lower limbs, the other one limb being opposite to the one limb around which the second cuff is to be wrapped; a cuff pressure controller which controls pressures that are applied to the cuffs, respectively; a cuff pressure detector which, from an output of a pressure sensor connected to the second cuff, and an output of a pressure sensor connected to the third cuff, detects cuff pressures in the respective cuffs; a pulse wave detector which detects respective pulse waves from outputs of the pressure sensors; and an analyzer which analyzes the detected pulse waves to evaluate a vascular endothelial function, the cuff pressure controller controls the cuff pressure of the second cuff to avascularize the upper or lower limb around which the second cuff is wrapped, for a predetermined time period, the pulse wave detector detects a pulse wave corresponding to the second cuff, and a pulse wave corresponding to the third cuff, before and after the avascularization in a state where the cuff pressures of the second and third cuffs are controlled to respective predetermined pressures by the cuff pressure controller, and the analyzer corrects the pulse waves corresponding to the second cuff and detected before and after the avascularization, by the pulse waves corresponding to the third cuff and detected before and after the avascularization, and evaluates the vascular endothelial function based on the corrected pulse waves corresponding to the second cuff.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the pulse waves handled in the analyzer are pulse wave indexes, and the pulse wave indexes are a parameter indicating a feature of a pulse wave.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the correction corrects a result of a comparison between the pulse wave indexes corresponding to the second cuff and detected before and after the avascularization.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the comparison result is ratios of the pulse wave indexes of the second cuff and the third cuff before and after the avascularization, and the correction corrects the ratio of the pulse wave indexes corresponding to the second cuff by using the ratio of the pulse wave indexes corresponding to the third cuff.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the comparison and the correction are performed by using values of the pulse wave indexes corresponding to the second cuff or the third cuff, the values being obtained at a required timing, and values of the pulse wave indexes corresponding to the third cuff or the second cuff, the values being obtained at the required timing.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the comparison and the correction are performed by using values of the pulse wave indexes corresponding to the third cuff, and values of the pulse wave indexes corresponding to the second cuff and equal to the values of the pulse wave indexes corresponding to the third cuff.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the pulse wave indexes are a maximum value of a pulse wave amplitude, or a mean value in the vicinity of the maximum value.
The apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter is characterized in that the analyzer further performs a process of obtaining a systolic blood pressure and a diastolic blood pressure, and dividing an amplitude of the detected pulse wave by a difference between the systolic blood pressure and the diastolic blood pressure, thereby obtaining a compliance of a blood vessel.
According to the apparatus for evaluating a vascular endothelial function of the presently disclosed subject matter, the pulse waves corresponding to the second cuff and detected before and after the avascularization are corrected by those corresponding to the third cuff and detected before and after the avascularization, and the vascular endothelial function is evaluated based on the corrected pulse waves corresponding to the second cuff. Therefore, the vascular endothelial function can be accurately evaluated.
Namely, the pulse waves corresponding to the second cuff are presumed to contain an influence caused by an expansion of the vessel diameter due to the avascularization, and influences of respiration and autonomic nerves, and by contrast those corresponding to the third cuff are presumed to contain influences of respiration and autonomic nerves. When the pulse waves corresponding to the second cuff and containing an influence caused by an expansion of the vessel diameter due to the avascularization, and influences of respiration and autonomic nerves are corrected by those corresponding to the third cuff and containing influences of respiration and autonomic nerves, therefore, it is possible to take out only information relating to the expansion of the vessel diameter due to the avascularization. Therefore, it is expected to accurately evaluate a vascular endothelial function without being influenced by respiration and autonomic nerves.
The first cuff 11 is to be wrapped around a first portion such as an upper or lower limb of the body of the subject, and used for applying a pressure for avascularization on the portion around which the cuff is wrapped. The second cuff 51 is to be wrapped around a second portion such as the upper or lower limb of the body of the subject on the side where the first cuff 11 is wrapped, and used for applying a pressure for detecting a pulse wave of the portion around which the cuff is wrapped. In a measurement, as shown in
The first pump 12 feeds the air into the first cuff 11 under the control of the controller 20. The first valve 13 switches non-discharging/discharging of the air in the first cuff 11 under the control of the controller 20. The second pump 52 feeds the air into the second cuff 51 under the control of the controller 20. The second valve 53 switches non-discharging/discharging of the air in the second cuff 51 under the control of the controller 20. The third pump 72 feeds the air into the third cuff 71 under the control of the controller 20. The third valve 73 switches non-discharging/discharging of the air in the third cuff 71 under the control of the controller 20. The controller 20 constitutes the cuff pressure controller which controls pressurization and depressurization of the first cuff 11, the second cuff 51, and the third cuff 71.
The first pressure sensor 14 outputs a signal corresponding to the pressure in the first cuff 11, the second pressure sensor 54 outputs a signal corresponding to the pressure in the second cuff 51, and the third pressure sensor 74 outputs a signal corresponding to the pressure in the third cuff 71. The analyzer/processor 30 controls the whole apparatus, is configured by, for example, a computer, and includes a cuff pressure detector 31, a pulse wave detector 32, and an analyzer 33. In the embodiment, for the sake of convenience, the controller 20 which controls the first cuff 11, the second cuff 51, and the third cuff 71, and the analyzer/processor 30 which performs analysis and processing are commonly used for the cuffs. Alternatively, they may be disposed for each of the cuffs.
The cuff pressure detector 31 detects the respective cuff pressures of the first, second, and third cuffs 11, 51, 71 from outputs of the first, second, and third pressure sensors 14, 54, 74. The pulse wave detector 32 detects pulse waves from the outputs of the second pressure sensor 54 and the third pressure sensor 74. The analyzer 33 calculates a systolic blood pressure and a diastolic blood pressure based on the detected pulse waves, and, as described later, analyzes pulse waves before and after the avascularization to evaluate a vascular endothelial function. The displaying unit 40 displays a result of the evaluation of the vascular endothelial function, the blood pressure value, and the like.
The controller 20 drives the first, second, and third pumps, and the first, second, and third valves to control the cuff pressures of the first, second, and third cuffs to a predetermined value. For example, the cuff pressures of the first cuff 11, the second cuff 51, and the third cuff 71 are changed as shown in
The apparatus for evaluating a vascular endothelial function can perform processing shown in, for example, the flowchart of
When the cuff pressures reaches a predetermined value, the air supplies from the second pump 52 and the third pump 72 are stopped, and the second valve 53 and the third valve 73 are controlled, whereby the cuff pressures are gradually lowered (S12).
During the process of lowering the cuff pressures, the cuff pressure detector 31 detects the cuff pressures from the outputs of the second pressure sensor 54 and the third pressure sensor 74, and the pulse wave detector 32 detects the pulse waves for each beat. Based on the cuff pressures and the pulse waves, the analyzer 33 obtains the values of the respective pulse wave indexes (S13). In the embodiment, the respective maximal pulse wave amplitudes are set as the pulse wave indexes. The maximal pulse wave amplitudes are obtained by statistically processing the pulse waves which are obtained in the measurement period Tp. The pulse wave in the measurement period Tp obtained by the second pressure sensor 54 is as shown in
The blood pressure at the timing when the pulse wave shows the maximal amplitude in the measurement period Tp is the mean blood pressure. In the case where the mean blood pressure is previously known, therefore, pressurization to a pressure which is equal to or higher than the mean blood pressure is not necessary in order to obtain the maximal pulse wave, and the burden on the subject is reduced.
Similarly, the pulse wave in the measurement period Tp obtained by the third pressure sensor 74 is as shown in
Next, the pressurization period T for avascularization when, in a state where the first valve 13 is closed under the control of the controller 20, the air is sent from the first pump 12 to the first cuff 11 to raise the cuff pressure, and avascularization is performed at a pressure which is a sum of the systolic blood pressure and the predetermined pressure (for example, 50 mmHg) is realized (S14). After five minutes, the first valve 13 is opened to release the cuff pressure, whereby the cuff pressure is lowered to a pressure which is equal to or lower than the systolic blood pressure (S15).
Thereafter, a state where the second valve 53 and the third valve 73 are closed is promptly set, the air is sent from the second pump 52 to the second cuff 51, and the air is sent from the third pump 72 to the third cuff 71, so that to the pressures of the cuffs are raised (S16). When the cuff pressures reach a predetermined value, the pressures of the second cuff 51 and the third cuff 71 are gradually lowered in a similar manner as described above (S17).
During the process of lowering the cuff pressures, the cuff pressures and the pulse waves for each beat are detected in a similar manner as step S13, and the analyzer 33 obtains the maximal pulse wave amplitudes Bc and Bo as the values of the pulse wave indexes from the cuff pressures and the pulse waves (S18).
Then, a result of comparison of the maximal pulse wave amplitudes Ac and Bc of the avascularization side is corrected by using that of comparison of the maximal pulse wave amplitudes Ao and Bo of the non-avascularization side (S19). Each of the comparisons can be performed by obtaining a result of a division of the maximal pulse wave amplitude Bc (Bo) by the maximal pulse wave amplitude Ac (Ao). Therefore, the comparison result of the avascularization side is (Bc/Ac), and that of the non-avascularization side is (Bo/Ao). The correction may be performed by dividing (Bc/Ac) of the comparison result of the avascularization side by (Bo/Ao) of the comparison result of the non-avascularization side, or by subtracting (Bo/Ao) of the comparison result of the non-avascularization side from (Bc/Ac) of the comparison result of the avascularization side.
The corrected maximal pulse wave amplitude ratio of the avascularization side is displayed together with the systolic blood pressure and the diastolic blood pressure, on the displaying unit 40 (S20). The vascular endothelial function is evaluated by the corrected maximal pulse wave amplitude values of the avascularization side which are displayed.
In the above, the comparison results are obtained in first. Alternatively, the correction may be performed in first. For example, the representative pulse wave amplitude Ac (Bc) of the avascularization side may be divided or subtracted by the representative pulse wave amplitude Ao (Bo) of the non-avascularization side to obtain the corrected pulse wave amplitude (for example, Ab) before avascularization and the corrected pulse wave amplitude (for example, Ba) after avascularization, and (Ba/Ab) may be obtained by comparison.
The relationship between the pulse wave amplitude and the cuff pressure is not constant.
In
In the above, during the measurement periods Tp and Ta, the maximum value of the pulse wave amplitude corresponding to the second cuff 51 (hereinafter, the amplitude is referred to as the pulse wave amplitude of the second cuff 51) is obtained, also the maximum value of the pulse wave amplitude corresponding to the third cuff 71 (hereinafter, the amplitude is referred to as the pulse wave amplitude of the third cuff 71) is similarly obtained, and the values are used in the correction. In the measurement periods Tp and Ta, however, the time when the pulse wave amplitude of the second cuff 51 is maximum is not always identical with that when the pulse wave amplitude of the third cuff 71 is maximum. Therefore, the correction may be performed by obtaining the pulse wave amplitude of the third cuff 71 at the time when the pulse wave amplitude of the second cuff 51 is maximum (the times when Ac and Bc are attained in
Before avascularization, the pulse wave amplitudes of the second cuff 51 and the third cuff 71 may be obtained at the same timing, and, after avascularization, the timing when the pulse wave amplitude of the third cuff 71 of the non-avascularization side after avascularization is equal to that of the third cuff 71 before avascularization may be obtained. Then, the pulse wave amplitude of the second cuff 51 of the avascularization side at this timing may be obtained, and used as a value (hereinafter, referred to as the representative value) to be used in the comparison.
As shown in
In the embodiment, the pulse wave amplitude is measured during the process of depressurizing the cuff pressure. Alternatively, the measurement may be performed during the process of pressurizing the cuff pressure.
Furthermore, the pulse wave amplitude for each beat may be measured in a state where the cuff pressure is kept constant (at a constant pressure). For example, the constant pressure may be about 20 mmHg.
The embodiment is configured so that avascularization is performed by the first cuff 11, and the pulse wave for each beat is measured by the second cuff 51. Alternatively, the first cuff 11 and the second cuff 51 may be configured as a single cuff. In the alternative, the configuration of
The operation of performing avascularization on the subject for a predetermined time as described above means the followings. Normal vascular endothelial cells are caused to produce vasodepressor materials such as nitric monoxide (NO) by stimulation due to a blood flow or medication. When the vascular endothelial function is lowered, the ability of producing the vasodepressor materials is lowered. With a measurement of the degree of vessel expansion due to avascularization, it is possible to evaluate the vascular endothelial function.
The relationships among the inner vascular pressure, the cuff pressure, and the pulse wave amplitude contained in the cuff pressure signal can be described as follows. First, it is known that, when the inner vascular pressure and the cuff pressure are equal to each other, the vascular compliance is maximum. When the cuff pressure is equal to the mean blood pressure, the difference between the maximal and minimal blood pressures in a vessel, i.e., the vessel volumetric change due to the pulse pressure is maximum. In the measurement periods Tp and Ta before and after avascularization, therefore, the maximal pulse wave amplitudes Ac and Bc are measured by using the second cuff 51, and set as representative pulse wave amplitudes of the avascularization side, and the maximal pulse wave amplitudes Ao and Bo are measured by using the third cuff 71, and set as representative pulse wave amplitudes of the non-avascularization side.
Alternatively, the mean blood pressure may be previously measured, and the pulse wave amplitude at the application of the cuff pressure corresponding to the mean blood pressure may be set as the representative value. In any case, the representative value is obtained by applying statistical processing on the pulse wave amplitudes in the measurement periods Tp and Ta in which the second cuff 51 and the third cuff 71 are used.
In the above description, the measurement of the pulse wave amplitude by using the second cuff 51 and the third cuff 71 is performed one time respectively before and after the pressurization period T for avascularization. Alternatively, a plurality of measurements may be performed. In the alternative, the numbers of measurements before and after avascularization may be different from each other.
Similarly, during the measurement period Tp, two measurements are performed by using the third cuff 71, and the pulse wave detector 32 obtains measured-value groups Xo1 and Xo2. The analyzer 33 performs statistical processing on the measured-value groups Xo1 and Xo2 to obtain representative values. In this example, maximal pulse wave amplitudes Ao1 and Ao2 are obtained as representative values as shown in
Also during the measurement period Ta shown in
Similarly, during the measurement period Ta shown in
The analyzer 33 performs statistical processing for obtaining the respective mean values on the maximum pulse wave amplitudes Ac1 and Ac2 and maximum pulse wave amplitudes Bc1 and Bc2, and the maximum pulse wave amplitudes Ao1 and Ao2 and maximum pulse wave amplitudes Bo1 and Bo2 which are obtained in the above-described processes, to obtain final representative values. By using the obtained representative values, the representative values of the avascularization side before and after avascularization are compared with each other, and a result of the comparison can be corrected by the representative values of the non-avascularization side before and after avascularization. As a result of the above-described measurements and processing, errors can be leveled, and accurate evaluation is enabled.
Other measurement technique and statistical processing will be described. The vessel expansion due to avascularization by the first cuff 11 and its release, i.e., the increase of the vessel diameter is gradually increased after the release of the avascularization to reach the peak after several tens of seconds, and thereafter is reduced for several minutes. Based on the peak, it is possible to evaluate the degree of vessel expansion. After avascularization using the first cuff 11, the maximum value of the pulse wave amplitude is measured several times by using the second cuff 51 and the third cuff 71, and a maximum one of the maximum values is set as the pulse wave amplitude in the vessel expansion, thereby obtaining the peak of the vessel expansion.
As shown in
The analyzer 33 compares the levels of the maximal pulse wave amplitudes Bc1, Bc2, Bc3, and Bc4 with one another, and selects the maximal pulse wave amplitude Bc2 as the representative value.
Similarly, in accordance with four measurements using the third cuff 71, measured-value groups Yo1, Yo2, Yo3, and Yo4 are obtained. The analyzer 33 performs statistical processing on the measured-value groups Yo1, Yo2, Yo3, and Yo4, and, as shown in
The analyzer 33 compares the levels of the maximal pulse wave amplitudes Bo1, Bo2, Bo3, and Bo4 with one another, and selects the maximal pulse wave amplitude Bo2 as the representative value. The maximal pulse wave amplitude Bc2 which is maximum in the avascularization side is corrected by the maximal pulse wave amplitude Bo2 which is maximum in the non-avascularization side, and also the maximal pulse wave amplitude which is obtained by the measurement before the pressurization period T is corrected as described above. The analyzer 33 performs comparison by using the corrected results, and calculates a ratio of the correction results before and after the pressurization period T. The calculated result is displayed together with the obtained blood pressure value on the displaying unit 40. As described above, the ratio may be obtained in first, and then the comparison may be performed.
The analyzer 33 performs processing in which the vascular compliance is obtained, in addition to the processings in which a result of comparison of pulse waves, and blood pressures are obtained. The analyzer 33 divides the detected pulse wave amplitude by the difference (pulse pressure) between the systolic blood pressure and the diastolic blood pressure, to obtain the vascular compliance C. Although the phenomenon in which, when the inner vascular pressure and the cuff pressure are equal to each other, the vascular compliance is maximum is already known, the compliance which is to be obtained in this case is not restricted to a value obtained when the inner vascular pressure and the cuff pressure are equal to each other. During the measurement periods Tp and Ta for measuring the pulse wave amplitude which are set before and after the pressurization period T, compliances based on the amplitudes of corrected representative values which are respectively obtained in the periods may be obtained. The obtained compliances are displayed on the displaying unit 40, independently or together with the ratio of the pulse wave amplitudes which have been described, and obtained blood pressure values. In this case, data of the measured compliances may be caused to remain as history information, the information may be formed as a table or a graph, and the trend may be displayed on the displaying unit 40.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-008465 | Jan 2014 | JP | national |
