JP5739291B2 - Impedance respiration measurement device and respiration state measurement system - Google Patents

Description

  The present invention relates to an impedance respiration measurement apparatus, and also relates to a respiration state measurement system configured using the impedance respiration measurement apparatus and the electrical impedance tomographic image measurement apparatus.

  In a conventional impedance respiration measurement device, a plurality of electrodes are arranged on the chest and the like, and two electrodes for supplying a current and two electrodes for detecting a potential difference are determined, and an electric impedance is obtained by measuring a potential difference. In such an impedance respiration measurement apparatus, the generation of body movement artifacts is a problem, and various methods for removing the artifacts have been developed.

  For example, in addition to the first channel for performing normal impedance respiration measurement, a second channel for observing body motion artifacts due to body motion is provided, and a signal obtained by the first channel and a signal obtained by the second channel There is known an apparatus configured to obtain pure respiration information based on comparison with (see Patent Document 1).

  Also, by measuring at multiple frequencies, calculating these difference signals, and normalizing the difference signal with respect to the signal representing the impedance measurement itself at one or more frequencies, the frequency can be reduced, such as motion artifacts. There is also known one that suppresses the influence of an impedance signal component whose dependent change is substantially proportional to the impedance signal value (see Patent Document 2).

  Another problem with the conventional impedance respiration measurement device is that it is possible to measure the ventilation volume by performing calibration with a flow sensor in advance, but calibration data for each body position (sitting position, standing position, supine position, etc.) However, both calibrations for each posture in advance and measurements each time the posture changes are time consuming and cumbersome.

  On the other hand, the electrical impedance tomographic image measuring apparatus can measure the ventilation volume without performing calibration with a flow sensor or the like, and according to this, the ventilation volume can be measured over time. However, this electrical impedance tomogram measuring device is easily affected by body movements, and during body movements, the accuracy of both the tomographic image and the ventilation volume displayed with the optimal electrical characteristic values of each pixel is significantly reduced. There was a problem.

Japanese Patent Publication No. 03-47095 Special Table 2000-517199

  The present invention has been made in view of the present state of respiration measurement as described above, and an object thereof is an impedance respiration measurement apparatus that is not easily affected by body movement and that can perform high-precision measurement even when there is body movement. A respiratory condition measurement system is provided. Furthermore, since the present invention can estimate the change in ventilation volume every moment by means of the electrical impedance tomography measuring device, when a change in body position is detected, the ventilation volume is immediately recalibrated without using a flow sensor or the like. A respiratory state measurement system capable of obtaining a highly accurate ventilation amount is provided.

The impedance respiration measurement device according to the present invention is a case where a plurality of electrodes attached so as to surround a predetermined position on the surface of a living body and a current are applied from a first input electrode pair selected from the plurality of electrodes In addition, a potential difference of a first output electrode pair different from the first input electrode pair selected from the plurality of electrodes is detected, and a current is applied from a second input electrode pair different from the first input electrode pair. Obtained from the first output electrode pair and the second output electrode pair, respectively, and a potential difference detecting means for detecting a potential difference between the second output electrode pair different from the first output electrode pair. Calculating means for calculating an average impedance based on the potential difference.

  In the impedance respiration measuring apparatus according to the present invention, the calculating means obtains respiratory state information of a living body based on the calculated average impedance.

The impedance respiration measurement apparatus according to the present invention further includes changing the first and second input electrode pairs and the first and second output electrode pairs selected from a plurality of electrodes, and calculating the average impedance calculated by the calculation means. And an electrode position determining unit that determines an optimal input electrode pair and an optimal output electrode pair.

  The impedance respiration measuring device according to the present invention further includes a ventilation volume measuring means capable of measuring the ventilation volume simultaneously with the calculation of the average impedance, and a calibration means for calculating and storing a plurality of calibration equations for converting the average impedance into the ventilation volume. And selecting an appropriate calibration formula from the calibration formulas provided by the calibration means, and estimating the ventilation volume from the average impedance calculated by the calculation means.

  In the impedance respiration measurement device according to the present invention, the impedance respiration measurement device includes a posture change detection means for detecting the presence or absence of a change in posture, and when the change in the posture is detected by the posture change detection means, the calibration means The calibration formula provided by is switched, or a new calibration formula is calculated, and the ventilation amount is estimated from the average impedance calculated by the calculation means.

In the respiratory state measurement system according to the present invention, when a current is applied from a plurality of electrodes attached so as to surround a predetermined position on the surface of a living body and a first input electrode pair selected from the plurality of electrodes In addition, a potential difference of a first output electrode pair different from the first input electrode pair selected from the plurality of electrodes is detected, and a current is applied from a second input electrode pair different from the first input electrode pair. Obtained from the first output electrode pair and the second output electrode pair, respectively, and a potential difference detecting means for detecting a potential difference between the second output electrode pair different from the first output electrode pair. An impedance respiration measuring device comprising: a calculating means for calculating an average impedance based on a potential difference; and a position of the organ and tissue of the living body and electrical characteristics thereof, and the biological cross section is divided into a number of meshes. , Create a mathematical model of three or more dimensions that can be calculated by changing the electrical property value of each mesh to a plurality (n), and use this mathematical model to change the electrical property value of any mesh to a plurality (n) When a constant current is applied to a third input electrode pair in which any two of the plurality of electrodes are selected, a third output electrode pair in which any two of the plurality of electrodes are selected And calculating a plurality of (n) first potential differences (Dmodel) generated in each of the first and second potential differences generated in the third output electrode pair when a constant current is applied to the third input electrode pair. A plurality (n) of (Dmean) are measured, and a plurality (n) of electrical characteristic values corresponding to each pixel are calculated using the first potential difference (Dmodel) and the second potential difference (Dmean). Characteristic value for each pixel Electrical impedance tomographic image measuring apparatus for obtaining a tomographic image by estimating the gas characteristic values, and a central control unit for obtaining a respiratory condition information of a living body from said electrical impedance tomographic image measuring device and the impedance respiratory measuring device It is characterized by comprising.

In the respiratory state measurement system according to the present invention, the impedance respiration measurement apparatus changes the first and second input electrode pairs and the first and second output electrode pairs selected from a plurality of electrodes, and uses the calculation means. An electrode position determining unit that performs calculation and determines an optimal input electrode pair and an output electrode pair is provided.

  In the respiratory condition measurement system according to the present invention, the electrical impedance tomographic image measuring apparatus includes a ventilation amount calculating means for obtaining a ventilation amount of a living body based on an optimal electrical characteristic value in each pixel.

  In the respiratory condition measurement system according to the present invention, the impedance respiratory measurement device further includes an average impedance calculated by the calculation unit and a ventilation amount provided from a ventilation amount calculation unit of the electrical impedance tomogram measurement device, Calibration means for calculating and storing a calibration formula for converting the average impedance into the ventilation volume is selected, an appropriate calibration formula is selected from the calibration formula provided by the calibration means, and the ventilation volume is calculated from the average impedance calculated by the calculation means. It is characterized by estimating.

  In the respiratory state measurement system according to the present invention, the impedance respiration measurement apparatus includes a posture change detection unit that detects the presence or absence of a change in posture, and when the change in the posture is detected by the posture change detection unit, the calibration unit The calibration equation provided by is switched or a new calibration equation is calculated, and the ventilation amount is estimated from the average impedance calculated by the calculating means.

  In the respiratory condition measurement system according to the present invention, the impedance respiration measurement device includes body movement detection means for detecting body movement, and the central control unit detects that the body movement is being detected by the body movement detection means. Is characterized in that only the ventilation volume information obtained from the impedance respiration measuring device is processed as valid.

  In the respiratory state measurement system according to the present invention, the impedance respiration measurement device includes body position change detection means for detecting the presence or absence of body position change, and the central control unit detects a change in body position by the body position change detection means. The respiration rate information obtained from the impedance respiration measuring device is recalibrated.

  In the respiratory condition measurement system according to the present invention, the central control unit adds and averages the optimum electrical characteristic value in each pixel obtained by the electrical impedance tomogram measurement device for a certain period.

  In the respiratory condition measurement system according to the present invention, the optimal electrical in each pixel obtained by the electrical impedance tomographic image measurement apparatus when the ventilation volume obtained from the impedance respiration measurement apparatus is within a predetermined range is obtained by addition averaging. The calculation is performed using the characteristic value.

  According to the impedance respiration measurement device according to the present invention, the first output electrode pair and the second output electrode pair, the impedance difference obtained by averaging the potential difference obtained from each to remove the influence of body movement, It is possible to detect the timing when the measurement of the tomographic image and the ventilation volume by the electrical impedance tomographic image measuring apparatus is effective by processing the difference in potential difference obtained from the above to identify the presence or absence of body movement.

  According to the impedance respiration measuring apparatus according to the present invention, the input electrode pair and the output electrode pair selected from a plurality of electrodes are changed, the calculation by the calculation means is performed, and the optimum input electrode pair and the output electrode pair are determined. Since the position determining unit is provided, impedance respiration measurement in which the influence of body movement is effectively canceled or reduced is possible.

  The impedance respiration measuring apparatus according to the present invention further includes a ventilation measuring means for measuring the ventilation volume of a living body, and measures the ventilation volume at the same time as calculating the average impedance in a certain posture, and measures the ventilation volume measured by the calibration means. Once the calibration formula for the average impedance is calculated once, it is possible to immediately estimate the ventilation volume from the average impedance for the body position, even when body movement occurs. .

  According to the respiratory condition measurement system of the present invention, since the central controller obtains the respiratory condition information of the living body from the impedance respiratory measurement device and the electrical impedance tomogram measurement device, the impedance respiratory measurement is performed when there is body movement. When only the information of the apparatus is used and there is no body movement, the information of both the impedance respiration measurement apparatus and the electrical impedance tomogram measurement apparatus can be used. For example, when body position change occurs, body movement occurs during the body position change, so only the breathing state information from the impedance respiration measurement device is used, and the body position change is completed. By obtaining a relational expression between the ventilation volume calculated from the impedance tomography measurement device and the average impedance of the impedance measurement device, it can be used as a conversion formula for calculating the ventilation volume in the same body posture, and body movement occurs. Even when it is, it is possible to immediately calculate the ventilation volume from the average impedance.

  In the respiratory state measurement system according to the present invention, the electrode, the constant current application means, and the measurement means are further advantageous in that those provided in the electrical impedance tomogram measurement apparatus can be shared by the impedance respiration measurement apparatus.

The block diagram which shows embodiment of the respiratory condition measuring system which concerns on this invention. FIG. 3 is an arrangement configuration diagram of electrodes and the like in the chest for explaining impedance measurement according to the first embodiment of the impedance respiration measurement device constituting the respiration state measurement system according to the present invention. FIG. 3 is an arrangement configuration diagram of electrodes and the like in the chest for explaining impedance measurement according to the first embodiment of the impedance respiration measurement device constituting the respiration state measurement system according to the present invention. The arrangement block diagram of the electrode etc. in the chest for demonstrating the impedance measurement by 2nd Embodiment of the impedance respiration measuring apparatus which comprises the respiratory condition measuring system which concerns on this invention. The arrangement block diagram of the electrode etc. in the chest for demonstrating the impedance measurement by 2nd Embodiment of the impedance respiration measuring apparatus which comprises the respiratory condition measuring system which concerns on this invention. The arrangement block diagram of the electrode etc. in the chest for demonstrating the impedance measurement by 2nd Embodiment of the impedance respiration measuring apparatus which comprises the respiratory condition measuring system which concerns on this invention. The figure which shows the example which produces | generates a representative EIT image by the addition average of the EIT image of the electrical impedance tomogram measuring apparatus which comprises the respiratory condition measuring system which concerns on this invention. The figure which shows the example which displays the typical EIT image of the electrical impedance tomogram measuring apparatus which comprises the respiratory condition measuring system which concerns on this invention. The figure explaining the method of extracting body movement information from the impedance waveform measured with the impedance respiration measuring apparatus which comprises the respiratory condition measuring system which concerns on this invention. The figure which shows an advantage when the electrode arrangement | positioning of the electrical impedance tomogram measuring apparatus which comprises the respiratory condition measuring system which concerns on this invention is shared with an impedance respiratory measuring apparatus.

  Embodiments of an impedance respiration measurement device and a respiration state measurement system according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference numerals and redundant description is omitted. The block diagram of the respiratory condition measuring system which concerns on FIG. 1 at embodiment is shown. In this system, a plurality of electrodes 11 (11-1, 11-2,..., 11-8, etc.) are attached to the living body 10 so as to surround the living body. In this example, 8 pieces are arranged at equal intervals in one cross section, but 16 pieces may be used, and different numbers may be arranged in different cross sections.

  The electrode 11 configured as described above is applied to the electrode controller 20, the impedance respiration measurement device having the computer system 50, and the electrical impedance tomography measurement device having the computer system 30 shown in FIG. 1. The electrode control unit 20 is connected to the computer systems 30 and 50.

  Each electrode including the electrodes 11-1 to 11-8 is connected to the electrode control unit 20 via a lead wire. The electrode control unit 20 may be disposed directly on each electrode without using a lead wire. The electrode control unit 20 includes a constant current applying unit 21 and a measuring unit 22, and the applied constant current is preferably a high frequency (for example, several MHz or more) that goes straight through the cell wall, but is about several tens kHz to several hundreds kHz. There may be. The constant current applying unit 21 and the measuring unit 22 operate in synchronization with the same clock.

  Hereinafter, an embodiment of an impedance respiration measuring device according to the present invention will be described. The embodiment of the impedance respiration measurement device according to the present invention constitutes a part of a respiration state measurement system. This apparatus has a configuration in which an electrode control unit 20 is connected to a computer system 50 as shown in FIG.

  A computer system 50 shown in FIG. 1 includes a main unit 51 including a CPU, a main storage unit, an external storage unit, and the like, a display unit 52 including LEDs connected to the main unit 51, a keyboard, a mouse, and the like. The input unit 53 is provided. The main body 51 includes a calculation unit 54 that calculates an average impedance based on a potential difference obtained from each of the first output electrode pair and the second output electrode pair, and a body position change detection unit 56 that detects the presence or absence of a body position change. , Body movement detecting means 56 for detecting the presence or absence of body movement based on the potential difference obtained from each of the first output electrode pair and the second output electrode pair, average impedance, presence or absence of body movement and presence or absence of body position change, Is provided as breathing information output means 55.

  In the following description, one electrode of the output electrode pair is fixed to one attached to the center of the chest. As a first embodiment, four electrodes (11-1 to 11-4) are arranged with the electrode 11-1 at the center of the chest and the electrode 11-3 at the center of the back side at the same height as the electrode 11-1. An example in which the electrode 11-2 is attached to the right side of the electrode 11-3 and the electrode 11-4 is attached to the left side of the electrode 11-3 with an interval of, for example, 4 to 5 cm is shown in FIGS. .

  In FIG. 2 and FIG. 3, reference numeral 22A denotes an amplifier in the measuring means 22. Moreover, the circle | round | yen of FIG. 2, FIG. 3 shows the thorax of a biological body, the line in a circle is an electric force line, and the space | interval of the adjacent electric force line shows 0.1V. Here, it is assumed that the electrical characteristics of the living body in FIG. 2 are bilaterally symmetric and the electrode arrangement is completely bilaterally symmetric.

  First, as shown in FIG. 2A, the connection switch is controlled to connect the electrodes 11-1 and 11-2 to the measuring means 22. Further, the computer system 50 controls the connection switch to connect the electrode 11-3 and the electrode 11-4 to the constant current applying means 21. In the state shown in FIG. 2A, measurement is performed by supplying a current of 1 mA from the constant current applying means 21 (A mode). At this time, assuming that a potential difference of 0.6 V is obtained from the output of the amplifier 22A, the impedance ZA is 600Ω by dividing 0.6V by 1 mA.

  Next, as shown in FIG. 2B, the connection switch is controlled to connect the electrodes 11-1 and 11-4 to the measuring means 22. Further, the connection switch is controlled so that the electrode 11-3 and the electrode 11-2 are connected to the constant current applying means 21. In this state, measurement is performed by supplying a current of 1 mA from the constant current applying means 21 (B mode). At this time, assuming that a potential difference of 0.6 V is obtained from the output of the amplifier 22A, the impedance ZB is 600Ω by dividing 0.6V by 1 mA. As described above, the measuring unit 22 detects the potential difference of the first output electrode pair and serves as a potential difference detection unit that detects the potential difference of the second output electrode pair when current is supplied from the second input electrode pair. Function.

  Here, one electrode 11-1 of the first output electrode pair (11-1 and 11-2) and one electrode 11-1 of the second output electrode pair (11-1 and 11-4) are fixed. The same electrode. Also, one electrode 11-3 of the first input electrode pair (11-3 and 11-4) and one electrode 11-3 of the second input electrode pair (11-3 and 11-2) are fixed. The same electrode.

  Assuming that the electrical characteristics of the living body shown in FIG. 2 are symmetrical, and the electrode arrangement is also completely symmetrical, from the first output electrode pair (11-1 and 11-2 in FIG. 2 (a)). Since ZA obtained and ZB obtained from the second output electrode pair (11-1 and 11-4 in FIG. 2B) are equal, it is not necessary to average them. However, in an actual living body, it is difficult to arrange the electrodes completely symmetrically, and since the electrical characteristics of the living body are not symmetrical, there is a slight difference between ZA and ZB. In order to reduce this difference, the computer system 50 calculates the impedance (610 + 590) ÷ 2 = 600Ω, which is an average of ZA and ZB, by the calculating means 54, and obtains the average impedance obtained in the first embodiment of the impedance respiration measuring apparatus. Treat as. The calculating means 54 calculates the average impedance based on the potential difference obtained from each of the first output electrode pair and the second output electrode pair.

  Next, when such measurement is performed, the electrode may move due to body movement that twists the body. In the example of FIG. 3, the electrode 11-2 that was at P <b> 1 at rest moves to P <b> 2 at a certain timing during body movement.

  Also in the above case, the measurement is performed as described in FIG. First, as shown in FIG. 3A, the connection switch is controlled to connect the electrodes 11-1 and 11-2 to the measuring means 22. Further, the connection switch is controlled so that the electrode 11-3 and the electrode 11-4 are connected to the constant current applying means 21. In the state shown in FIG. 3A, measurement is performed by supplying a current of 1 mA from the constant current applying means 21. At this time, if a potential difference of 0.5 V is obtained from the output of the amplifier 22A, the impedance ZA is 500Ω by dividing 0.5V by 1 mA.

  Next, as shown in FIG. 3B, the connection switch is controlled to connect the electrodes 11-1 and 11-4 to the measuring means 22. Further, the connection switch is controlled so that the electrode 11-3 and the electrode 11-2 are connected to the constant current applying means 21. In this state, measurement is performed by supplying a current of 1 mA from the constant current applying means 21. At this time, if a potential difference of 0.7V is obtained from the output of the amplifier 22A, the impedance ZB is 700Ω by dividing 0.7V by 1 mA.

  At this time, ZA obtained from the first output electrode pair (11-1 and 11-2 in FIG. 3A) and the second output electrode pair (11-1 and 11-4 in FIG. 3B) are obtained. 2), ZB obtained by the calculation means 54 calculates the average of ZA and ZB by means of the calculation means 54. By obtaining the impedance (500 + 700) ÷ 2 = 600Ω, it is possible to cancel or reduce the influence of the error in the impedance measurement value generated by the movement of the electrode due to body movement.

  Next, a procedure for calculating a ventilation amount as respiration information from the average impedance will be described. First, the impedance respiration measuring apparatus of the present embodiment measures the ventilation volume of the living body by the ventilation volume measuring means simultaneously with the calculation of the average impedance at the start of measurement, when the body position changes, and at any timing. Next, a calibration formula that associates the average impedance with the ventilation volume is calculated by the calibration means. The respiration information output means 55 can estimate the ventilation volume in real time from the average impedance that changes every moment using this relational expression. In addition, it is also possible to use the ventilation volume information provided from the electrical impedance tomogram measurement apparatus mentioned later as a ventilation volume measuring means of an impedance respiration measuring apparatus.

  By the way, the relationship between the average impedance calculated by the impedance respiration measuring apparatus and the ventilation volume varies greatly depending on the body position. In view of this, the impedance respiration measurement apparatus of this embodiment is provided with a body position change detection means 56 constituted by an acceleration sensor or the like, and notifies the respiration information output means 55 of the presence or absence of a body position change. The breathing information output means 55 switches the calibration formula according to the change in body position, remeasures the ventilation volume if necessary, newly calculates the calibration formula, and converts the average impedance into the ventilation volume. The calibration formula is switched at the start of measurement by the respiratory condition measurement system by measuring the relationship between the ventilation volume measured by the respiratory flow sensor and the average impedance in a different assumed posture and creating a database. After the start, when a change in body position is detected by the body position change detection means 56, a method of selecting a calibration expression of the body position closest to the detected body position is possible. Further, the calibration formula stored in the database may be a database in which data of a plurality of subjects are averaged instead of measuring and calculating the ventilation volume for the subject.

  The body part 51 of the impedance respiration measuring device is provided with body movement detecting means 57. The body movement detecting means 57 will be described with reference to the example of FIG. FIG. 9 shows a case in which the rolling action is performed a plurality of times during rest breathing on the bed (the part circled by a solid line) and the other body movements are carried out a plurality of times (a part circled by a broken line). The first stage shows the measurement in the A mode and the second stage shows the measurement in the B mode. On the other hand, the difference between the A mode and the B mode (third stage graph) is obtained by applying the high pass filter to remove the offset (fourth stage graph) and then performing the integration process. It is. The body motion detection means 57 for determining and outputting body motion information related to the presence or absence of body motion obtains the information shown in the fifth-stage graph, and when the information in this graph exceeds a preset threshold value, It is determined that movement has occurred. In this way, the body motion detection means 57 can accurately detect that the rollover operation or other body motion operations have been performed.

  The respiration information output means 55, for example, regarding the value obtained by converting the impedance calculated by the calculation means 54 as described above into a ventilation volume based on the calibration formula and the presence or absence of body movement detected by the body movement detection means 57, The data is output to the central control unit 60 and displayed on the display unit 61.

  By the way, when the body motion that twists the body increases and the electrode moves greatly, the influence may not be sufficiently canceled or reduced in the first embodiment. In order to cope with such a situation, in the second embodiment, as shown in FIG. 1, a plurality of electrodes (in FIG. 1) attached so as to surround a predetermined position on the surface of the chest of a living body. After determining the optimum input electrode pair and output electrode pair from the 8) of 11-1 to 11-8 by the computer system 50, the impedance measured at the input and output electrode pairs is averaged. The influence of body movement is canceled or reduced more powerfully than in the first embodiment.

  This will be described with reference to the case where eight electrodes are arranged as shown in FIGS. 4, 5, and 6, the electrode 11-1 is disposed at the center of the chest, and the electrode 11-5 is disposed at the center of the back side that is the same height as the electrode 11-1. Further, the electrodes 11-4, 11-3, and 11-2 are spaced from the electrode 11-5 clockwise by 4 to 5 cm, and the electrodes 11-5 are spaced from the electrode 11-5 by 4 to 5 cm counterclockwise. Electrodes 11-6, 11-7, and 11-8 are attached to each other. Here, three electrodes are provided on the left and right sides of the electrode 11-5, but one or more may be used. Moreover, you may move an electrode sticking position to a flank direction.

  In FIG. 4A, a fixed electrode of the output electrode pair is an electrode 11-1, and the other electrode of the first output electrode pair is an electrode 11-3. If the fixed electrode of the input electrode pair is the electrode 11-5, the other electrode of the first input electrode pair is symmetrical with the electrode that is not the fixed electrode of the first output electrode pair around the electrode 11-5. It becomes the electrode 11-7 in position. At this time, first, the connection switch is controlled as shown in FIG. 4A, and the electrodes 11-1 and 11-3 are connected to the measuring means 22. Further, the connection switch is controlled, and the electrodes 11-5 and 11-7 are connected to the constant current applying means 21. In this state, measurement is performed by flowing a current of 1 mA from the constant current applying means 21 (A mode). At this time, assuming that a potential difference of 0.9 V is obtained from the output of the amplifier 22A, the impedance ZA is 900Ω by dividing 0.9V by 1 mA.

  Next, as shown in FIG. 4B, the electrodes other than the fixed electrodes of the first output and input electrode pairs are reversed, that is, the second output electrode pair is replaced with the electrodes 11-1 and 11-7, The second input electrode pair is an electrode 11-5 and an electrode 11-3. At this time, the connection switch is controlled, and the electrodes 11-1 and 11-7 are connected to the measuring means 22. Further, the connection switch is controlled, and the electrodes 11-5 and 11-3 are connected to the constant current applying means 21. In this state, measurement is performed by supplying a current of 1 mA from the constant current applying means 21 (B mode). At this time, assuming that a potential difference of 0.6 V is obtained from the output of the amplifier 22A, the impedance ZB is 600Ω by dividing 0.6V by 1 mA. From the above, the difference in impedance between the A mode and the B mode is ΔZ1 = ZA−ZB = 900−600 = 300Ω.

  One example in which the first output electrode pair and the second output electrode pair to be selected, and the first input electrode pair and the second input electrode pair to be selected are changed will be described with reference to FIG. Also at this time, first, the connection switch is controlled as shown in FIG. 5A, and the electrodes 11-1 and 11-4 are connected to the measuring means 22. Further, the connection switch is controlled, and the electrodes 11-6 and 11-8 are connected to the constant current applying means 21. In this state, measurement is performed by flowing a current of 1 mA from the constant current applying means 21 (A mode). At this time, assuming that a potential difference of 1.1 V is obtained from the output of the amplifier 22A, the impedance ZA is 1100Ω by dividing 1.1V by 1 mA.

  Next, as shown in FIG. 5 (b), the electrodes other than the fixed electrodes of the first output and input electrode pairs are reversed, that is, the second output electrode pair is replaced with the electrodes 11-1 and 11-8, The two input electrode pairs are referred to as an electrode 11-6 and an electrode 11-4. At this time, the connection switch is controlled, and the electrodes 11-1 and 11-8 are connected to the measuring means 22. Further, the connection switch is controlled, and the electrodes 11-6 and 11-4 are connected to the constant current applying means 21. In this state, measurement is performed by supplying a current of 1 mA from the constant current applying means 21 (B mode). At this time, if a potential difference of 0.5V is obtained from the output of the amplifier 22A, the impedance ZB is 500Ω by dividing 0.5V by 1 mA. From the above, the difference in impedance between the A mode and the B mode is ΔZ2 = ZA−ZB = 1100−500 = 600Ω.

  Another example in which the first output electrode pair and the second output electrode pair to be selected, and the first input electrode pair and the second input electrode pair to be selected are changed will be described with reference to FIG. Also at this time, first, the connection switch is controlled as shown in FIG. 6A, and the electrodes 11-1 and 11-2 are connected to the measuring means 22. Further, the connection switch is controlled so that the electrodes 11-4 and 11-6 are connected to the constant current applying means 21. In this state, measurement is performed by flowing a current of 1 mA from the constant current applying means 21 (A mode). At this time, assuming that a potential difference of 0.8V is obtained from the output of the amplifier 22A, the impedance ZA is 800Ω by dividing 0.8V by 1 mA.

  Next, as shown in FIG. 6B, the electrodes other than the fixed electrodes of the first output and input electrode pairs are reversed, that is, the second output electrode pair is changed to the electrodes 11-1 and 11-6, The two input electrode pairs are referred to as an electrode 11-4 and an electrode 11-2. At this time, the connection switch is controlled, and the electrodes 11-1 and 11-6 are connected to the measuring means 22. Further, the connection switch is controlled so that the electrodes 11-4 and 11-2 are connected to the constant current applying means 21. In this state, measurement is performed by supplying a current of 1 mA from the constant current applying means 21 (B mode). At this time, assuming that a potential difference of 0.8V is obtained from the output of the amplifier 22A, the impedance ZB is 800Ω by dividing 0.8V by 1 mA. From the above, the difference in impedance between the A mode and the B mode is ΔZ3 = ZA−ZB = 800−800 = 0Ω.

  Comparing the difference between the A mode and the B mode for the input and output electrode pairs selected in FIGS. 4, 5, and 6, respectively, ΔZ1 = 300Ω (in the case of FIG. 4), ΔZ2 = 600Ω (in the case of FIG. 5), ΔZ3 = 0Ω (in the case of FIG. 6). In the present embodiment, the measured value by the input and output electrode pairs in FIG. 6 in which the difference between the A mode and the B mode is the smallest is adopted, and the average impedance (800 + 800) / 2 that is obtained by averaging ZA and ZB by the calculating means 54. By finding = 800Ω, the influence of the error of the impedance measurement value generated by the movement of the electrode due to body movement is canceled or reduced.

  Further, the body motion detecting means 57 performs the same procedure as the procedure already described with reference to FIG. 9 with respect to the measured values by the input and output electrode pairs in FIG. The difference between the mode and the B mode is taken, the offset is removed by applying a high-pass filter, integration processing is performed, and it is determined that body movement is occurring when the difference is equal to or greater than a preset threshold value.

  The respiration information output unit 55 outputs, for example, the value obtained by converting the impedance calculated by the calculation unit 54 to the ventilation amount and the presence or absence of body movement to the central control unit 60 and displays the same on the display unit 61. .

  In the above example, the optimal combination was selected from the three combinations of input and output electrode pairs. However, in practice, measurement was performed on all other electrode pairs in the same manner, and optimal input and output electrode pairs were selected. Calculate the average impedance. In addition, the impedance respiration measuring apparatus selects an optimum input and output electrode pair and calculates an average impedance for each sampling.

  According to the present embodiment, even when the number of electrodes to be used increases and the torsion due to body motion increases, the input and output electrode pairs used for measurement are appropriately changed to effectively improve the body The effects of dynamic artifacts can be removed. Further, the electrodes used in the impedance respiration measurement device can be arranged at equal intervals so as to surround the chest, and in this case, the electrode can be shared with the electrical impedance tomography measurement device according to the present invention. There is.

  Next, an embodiment of an electrical impedance tomographic image measurement apparatus according to the present invention will be described. The electrical impedance tomographic image measurement apparatus constitutes a part of a respiratory condition measurement system. This apparatus has a configuration in which an electrode control unit 20 is connected to a computer system 30 as shown in FIG.

For example, the constant current applying unit 21 may be any one of the input electrode pairs (for example, 11) of the electrodes 11-1 to 11-8, taking the slice plane including the electrodes 11-1 to 11-8 shown in the example of FIG. -1 & 11-2).

At this time, the measuring means 22 sequentially captures and digitizes the potential difference output from any one of the output electrode pairs (a combination of the electrodes 11-1 to 11-8) of each of the electrodes 11-1 to 11-8, and computerizes the computer system 30. Send to. At this time, there are eight output electrode pairs , but detection by the output electrode pairs (11-1 & 11-2, 11-1 & 11-8, 11-2 & 11-3) including one or both of the input electrode pairs is inaccurate. Therefore, it is not adopted in the electrical impedance tomography apparatus.

Next, the input electrode pair is changed to a different pair (for example, 11-2 & 11-3), and the potential difference is similarly obtained. Similarly, among the electrodes 11-1 to 11-8, a preset pair is set as an input electrode pair, and the potential difference of the output electrode pair is measured by the above-described procedure. The actually measured potential difference matrix thus obtained is defined as Dmean. The potential difference measurement is similarly performed on slices measured by electrodes other than the electrodes 11-1 to 11-8.

  By the way, as an advantage of sharing electrodes with the impedance respiration measurement device and the electrical impedance tomography measurement device, in addition to being able to reduce the number of electrodes, from the potential difference measured with the electrical impedance tomography measurement device, the impedance respiration measurement device The potential difference (and impedance) measured as A mode and B mode can be calculated. As an example, in order to measure an electrical impedance tomogram, as shown in FIG. 10 (a), among eight electrodes attached at equal intervals so as to surround the chest as shown in FIG. 10 (a), it is shown in FIG. 10 (b). A case where four electrodes are shared by the impedance respiration measuring apparatus will be described. When the A mode input electrode pair is the electrode 5-6, the output electrode pair is the electrode 1-4, the B mode input electrode pair is the electrode 4-5, and the output electrode pair is the electrode 1-6, the A mode In the measurement, the three types of output electrode pairs A1 (electrode 1-2), A2 (electrode 2-3), and A3 (electrode 3-4) measured using the electrode 5-6 as an input electrode pair in FIG. ), And the B mode is measured in three output electrode pairs B1 (electrode 8-1), B2 (measured with the electrode 4-5 as an input electrode pair in FIG. It is equal to the sum of electrodes 7-8) and B3 (electrodes 6-7). In other words, by sharing the electrodes, it is possible to obtain the necessary measurement results simply by processing the measurement results of the electrical impedance tomography measurement device without carrying out the measurement of the impedance respiration measurement device. It is possible to shorten the measurement time in the entire measurement system.

  The computer system 30 includes a main unit 31 including a CPU, a main storage unit, an external storage unit, and the like, a display unit 32 configured by LEDs connected to the main unit 31, an input unit 33 configured by a keyboard, a mouse, and the like. And. The main body 31 is provided with software as mathematical model creation means 34 for creating a mathematical model of three or more dimensions such as FEM (finite element method). The mathematical model creation means 34 performs the same processing operation as the mathematical model creation means 34 described in Japanese Patent Application No. 2010-205988 (referred to as a premise invention) invented and filed by the present inventors. 3D or higher mathematical model that can be calculated by dividing the cross-section of a living body into a large number of meshes based on the positions of the organs and tissues and their electrical characteristics, and changing the electrical characteristic values of each mesh into multiple (n) Create Here, any one of resistivity, electrical conductivity, dielectric constant, and magnetic permeability can be adopted as the electrical characteristic value.

  In addition to the mathematical model creation means 34, the main body 31 includes a first calculation means 35, a second calculation means 37, a determination means 38, a tomographic image display control means 39, and a database 36. The first calculation means 35, the database 36, the second calculation means 37, the determination means 38, and the tomographic image display control means 39 are the first calculation means 35, the database 36, the second calculation means 37, and the determination in the base invention. The configuration is the same as that of the means 38 and the tomographic image display control means 39.

That is, the first calculation means 35 changes the electrical characteristic value of an arbitrary mesh to a plurality (n) using the mathematical model obtained by the mathematical model creation means 34 and applies a constant current to the input electrode pair. In this case, a plurality of (n) first potential differences (Dmodel) respectively generated in any two output electrode pairs in the electrode are calculated. The database 36 calculates the resistivity matrix between the electrodes shown in the base invention for each resistivity (eight levels in the example), and the resistivity and output electrode pair set for the target tissue by the first calculation means 35. Can be configured as a database 36 of the correspondence relationship with the potential difference detected from.

  The second calculation means 37 calculates a plurality (n) of electrical characteristic values corresponding to each pixel using the plurality (n) of first potential differences and the second potential difference. Specifically, the second calculating means 37 calculates Dmean from the measured potential difference, a potential difference matrix Dmodel (n) for a plurality of (n) resistivities stored in the database 36, and sensitivity theory. A plurality of (n) electrical characteristic values such as resistivity for each pixel are calculated using a weighting correction coefficient known as a sensitivity matrix or Jacobian matrix. Here, the correction coefficient such as the sensitivity matrix can be calculated by a known method and stored as the database 36. Further, n is the number of the set lung resistivity, and in this example, eight types are used, but 300 types in increments of 0.2 Ωm may be calculated in advance and used as the database 36.

  As described above, a sensitivity matrix widely used in EIT in recent years is used, and each element of Dmean is compared with each element of Dmodel by division, and further, a value corrected by multiplying the sensitivity matrix to weight each element EIT (n) can be calculated for each pixel.

  The determination means 38 estimates and determines the optimum electrical characteristic value for each pixel from the plurality (n) of electrical characteristic values. The tomographic image display control unit 39 displays a tomographic image on the display unit 32 based on the optimum electrical characteristic value in each pixel.

Specifically, for each pixel, n in a state where there is no difference between Dmean and Dmodel (n), that is, n at which the rate of change is zero is the resistivity to be finally obtained. When the EIT (n) corrected by multiplying by the matrix is n, the resistivity to be finally obtained is obtained. With respect to this, the determining means 38 can determine the resistivity to be finally obtained when EIT (n) converges to zero by iterative calculation. Alternatively, n can be set discretely and EIT (n) It is also possible to determine the resistivity to be finally obtained when the absolute value or when [EIT (n)] ² is minimum n. If there are other slices, the same processing is performed for the other slices. The process executed for obtaining the resistivity as the optimum electrical characteristic value by the second calculation means 37 and the determination means 38 described so far can be referred to as the optimum electrical characteristic value determination process.

  The ventilation amount calculating means 41 calculates the ventilation amount of the living body based on the optimal electrical characteristic value in each pixel obtained as described above. For example, the flow rate of the subject is obtained by a flow sensor, and the optimal electrical characteristic value pattern (array) and average value of each pixel at this time are obtained and stored in a database, and each pixel determined by the determination means 38 is determined. Search the database using the optimal electrical characteristic value in and find the ventilation rate at the nearest pattern or average value.

  The central control unit 60 is composed of, for example, a computer. The central control unit 60 is connected to information input means 62 such as a keyboard, a touch panel, or a mouse, and information such as a display device having a screen such as an LCD or LED. Output means 61 is connected.

  The central control unit 60 is connected to the main body 51 of the computer system 50 that constitutes the impedance respiration measurement apparatus, and is connected to the main body 31 of the computer system 30 that constitutes the electrical impedance tomogram measurement apparatus. The central control unit 60 receives ventilation volume information and body movement information from the main body 51 of the impedance respiration measuring apparatus, and receives EIT image information and ventilation volume information from the main body 31 of the electrical impedance tomogram measurement apparatus, and processes them. And only valid information is output to the output means 61. The ventilation information of the electrical impedance tomography measuring device is also provided to the respiratory information output means 55 of the impedance respiratory measurement device, and the respiratory information output means 55 can be used as needed when a change in body position occurs. Using the ventilation information of the dynamic impedance tomography measuring device, the calibration means recalculates the calibration formula for average impedance and ventilation.

  By the way, the accuracy of the EIT image information and the ventilation information provided from the main body 31 of the electrical impedance tomogram measuring apparatus is highly likely to be significantly reduced by body movement. Therefore, when the central control unit 60 receives body motion information indicating that body motion is occurring from the main body 51 of the impedance respiration measurement device, the central control unit 60 receives the EIT image information and the ventilation amount received from the electrical impedance tomogram measurement device. The information is not output to the output means 61, and only the ventilation information provided from the main body 51 of the impedance respiration measuring device is output.

  The central control unit 60 cuts out the EIT image obtained from the main body 31 of the electrical impedance tomogram measuring apparatus as EIT data for each breath, and obtains the ventilation volume information obtained from the main body 51 of the impedance respiration measuring apparatus. And stored in the database in association with the respiration waveform, and when requested, as shown in the example in FIG. EIT for the average of one breath within a predetermined time by averaging (excluding EIT data where the ventilation volume exceeds the predetermined range, as indicated by x in FIG. 7). Is displayed with high accuracy. For example, Fig. 8 shows an example in which a typical EIT for every hour from 9:00 to 16:00 is displayed on a single screen, which is effective for understanding the status of diseases whose symptoms change greatly in units of several hours. It is.

20 Electrode control unit 21 Constant current applying unit 22 Measuring unit 22 Measuring unit 30 Computer system 31 Main unit 32 Display unit 33 Input unit 34 Mathematical model creation unit 35 Calculation unit 36 Database 37 Calculation unit 38 Determination unit 39 Tomographic image display control unit 41 Ventilation amount calculation means 50 Computer system 51 Main body 52 Display section 53 Input section 54 Calculation means 55 Respiration information output means 56 Body position change detection means 57 Body movement detection means 60 Central control section 61 Information output means 62 Information input means

Claims (14)

A plurality of electrodes attached to surround a predetermined position on the surface of the living body ;
When given the current from the first input electrode pairs selected from the plurality electrodes, and detects the potential difference different from the first output electrode pair and the first input electrode pairs selected from the plurality electrodes, wherein A potential difference detecting means for detecting a potential difference between a second output electrode pair different from the first output electrode pair when a current is applied from a second input electrode pair different from the first input electrode pair;
Calculating means for calculating an average impedance based on a potential difference obtained from each of the first output electrode pair and the second output electrode pair;
An impedance respiration measurement device comprising:   The impedance respiration measuring apparatus according to claim 1, wherein the calculating means obtains respiratory state information of a living body based on the calculated average impedance. The impedance respiration measurement device further includes:
The first and second input electrode pairs selected from the plurality of electrodes and the first and second output electrode pairs are changed, the average impedances calculated by the calculation means are compared, and the optimum input electrode pair and the optimum output electrode are compared. impedance respiration measurement apparatus according to claim 1 or 2, characterized by comprising an electrode position determining portion that determines the pair. The impedance respiration measurement device further includes:
A ventilation volume measuring means capable of measuring the ventilation volume simultaneously with the calculation of the average impedance, and a calibration means for calculating and storing a plurality of calibration equations for converting the average impedance into the ventilation volume,
The impedance respiration measurement according to any one of claims 1 to 3 , wherein an appropriate calibration formula is selected from calibration formulas provided by the calibration means, and a ventilation amount is estimated from an average impedance calculated by the calculation means. apparatus. The impedance respiration measuring device comprises body position change detecting means for detecting presence or absence of body position change,
When a change in body position is detected by the body position change detection means, the calibration formula provided by the calibration means is switched, or a new calibration formula is calculated, and the ventilation volume is estimated from the average impedance calculated by the calculation means. The impedance respiration measurement apparatus according to claim 4, wherein: A plurality of electrodes attached to surround a predetermined position on the surface of the living body;
Detecting a potential difference of a first output electrode pair different from the first input electrode pair selected from the plurality of electrodes when a current is applied from the first input electrode pair selected from the plurality of electrodes; A potential difference detecting means for detecting a potential difference between a second output electrode pair different from the first output electrode pair when a current is applied from a second input electrode pair different from the first input electrode pair; An impedance respiration measurement device comprising: a calculating means for calculating an average impedance based on a potential difference obtained from each of the output electrode pair and the second output electrode pair;
Based on the positions of the organs and tissues of the living body and the electrical characteristics thereof, the biological cross section is divided into a number of meshes, and the electrical property value of each mesh is changed into a plurality (n) of three or more dimensions that can be calculated. A mathematical model is created, and using this mathematical model, the electrical characteristic value of an arbitrary mesh is changed to a plurality (n), and any two of the plurality of electrodes are selected as a third input electrode pair. When a current is applied, a plurality (n) of first potential differences (Dmodel) respectively generated in a third output electrode pair in which any two of the plurality of electrodes are selected are calculated, and the third When a constant current is applied to the input electrode pair, a plurality (n) of second potential differences (Dmean) generated in the third output electrode pair are measured, and the first potential difference (Dmodel) and the second potential difference are measured. Using (Dmean) Electrical impedance tomographic image measuring apparatus for obtaining a tomographic image from said electrical characteristic value to estimate the optimum electrical characteristic values at each pixel to calculate the electrical characteristic values of a plurality (n) corresponding to each pixel,
A central control unit that obtains respiratory state information of the living body from the electrical impedance tomogram measurement device and the impedance respiration measurement device,
A respiratory condition measuring system comprising: In the impedance respiration measuring device, the first and second input electrode pairs and the first and second output electrode pairs selected from a plurality of electrodes are changed, the calculation is performed by the calculation means, and the optimum input electrode pair and the output are output. The respiratory state measurement system according to claim 6, further comprising an electrode position determination unit that determines an electrode pair.   The respiratory condition measurement according to claim 6 or 7, wherein the electrical impedance tomographic image measuring device comprises a ventilation amount calculating means for obtaining a ventilation amount of a living body based on an optimum electrical characteristic value in each pixel. system. The impedance respiration measurement device further includes:
Calibration means for calculating and storing a calibration formula for converting the average impedance into the ventilation volume from the average impedance calculated by the calculation means and the ventilation volume provided from the ventilation volume calculation means of the electrical impedance tomogram measuring device. Prepared,
9. The respiratory condition measurement system according to claim 8, wherein an appropriate calibration formula is selected from calibration formulas provided by the calibration means, and a ventilation amount is estimated from an average impedance calculated by the calculation means. The impedance respiration measuring device comprises body position change detecting means for detecting presence or absence of body position change,
When a change in body position is detected by the body position change detection means, the calibration formula provided by the calibration means is switched, or a new calibration formula is calculated, and the ventilation volume is estimated from the average impedance calculated by the calculation means. The respiratory condition measuring system according to claim 9. The impedance respiration measuring device includes body motion detecting means for detecting body motion,
Central control unit, when it is detected that is in motion by the body motion detecting means, claims 6 to 10, characterized in that processing only ventilation information obtained from the impedance respiratory measuring device as an active The respiratory state measurement system according to any one of the above. The impedance respiration measurement device comprises body position change detecting means for detecting the presence or absence of body position change,
Central control unit, when detecting a change in posture by the posture change detection means, according to any one of claims 6 to 11, characterized in that re-calibrate the ventilation information obtained from the impedance respiratory measuring device Respiratory status measurement system. The respiratory state according to any one of claims 6 to 12 , wherein the central control unit adds and averages the optimum electrical characteristic value in each pixel obtained by the electrical impedance tomography apparatus for a certain period. Measuring system.   In addition averaging, calculation is performed using an optimal electrical characteristic value in each pixel obtained by the electrical impedance tomogram measurement device when the ventilation obtained from the impedance respiration measurement device is within a predetermined range. The respiratory state measurement system according to claim 13.