JP2005233681A - Pressure measuring system and pressure measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure measuring system and a pressure measurement method, capable of correctly measuring the pressure in each liquid transport device in a fluid system provided with a plurality of liquid transport devices. <P>SOLUTION: The pressure measuring system is adapted to the pressure measurement of the fluid system, provided with a blood pump 13, a dialysis solution pump 15, and a water removing pump 14. The pressure measurement system comprises a first pressure wave form calculation part 2 for calculating the pressure waveform at the pressure measurement point of the fluid system; a frequency spectrum calculation part 3 for calculating the frequency spectrum from the pressure waveform; a filter part 4 for removing the frequency band to be a noise component from the frequency spectrum, by specifying the frequency band to be the noise component; and a second pressure wave form calculation part 5 for calculating the pressure wave from the frequency spectrum removed with the frequency band which becomes the noise component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pressure measuring device and a pressure measuring method.

  FIG. 9 is a schematic configuration diagram showing an example of a conventional hemodialysis apparatus. As shown in FIG. 9, the hemodialysis apparatus mainly includes an extracorporeal circulation device 71, a dialyzer 76, a control device 77, a blood circuit 79, and a dialysis circuit 81. In the example of FIG. 9, the dialyzer 76 is a hollow fiber type dialyzer.

  The extracorporeal circulation device 71 mainly has a blood pump 73 for circulating blood exsanguinated from the patient 30, a dialysate pump 75 for supplying and discharging dialysate, and blood exsanguinated from the patient 30. A water removal pump 74 that performs water removal, and a pressure detection unit 72. In the example of FIG. 9, the dialysate pump 75 is a dual-type pump and includes a liquid supply side pump (not shown) and a drainage side pump (not shown).

  In the example of FIG. 9, the blood circuit 79 and the dialysate circuit 81 constitute one fluid system. The blood pump 73 is provided on the blood circuit 79. Further, in the dialysis pump 75, a liquid supply side pump is provided on the liquid supply line of the dialysate circuit 81, and a liquid discharge side pump is provided on the liquid discharge line.

  Furthermore, the dialyzer 76 is connected to both the blood circuit 79 and the dialysate circuit 81. For this reason, if the extracorporeal circulation device 71 is operated, the blood taken out from the patient 30 is sent to the dialyzer 76 where it is contacted with the dialysate through the dialysis membrane and purified. The purified blood is returned to the patient 30. In addition, if the dewatering pump 74 is operated in the extracorporeal circulation device 71, excess water is removed from the blood, and the blood volume of the patient 30 becomes an appropriate value.

  In the dialysis apparatus shown in FIG. 9, a pressure sensor 78 is provided on the blood inlet side of the dialyzer 76. A pressure sensor 80 is provided on the dialysate outlet side of the dialyzer 76. The pressure sensors 78 and 80 are used to perform a simulation of the internal filtration flow rate, as will be described later.

  Each of the pressure sensors 78 and 80 outputs an analog signal corresponding to the blood or dialysate pressure to the pressure detector 72. The pressure detector 72 converts the signals output from the pressure sensors 78 and 80 into digital signals, and inputs the obtained digital signals to the control device 77. The control device 77 calculates two pressure values on the blood inlet side and dialysate outlet side of the dialyzer 76 based on the input digital signal.

  However, the pressure at the two pressure measurement points varies with time, and a pressure waveform is observed at the two pressure measurement points. Therefore, in the example of FIG. 9, the control device 77 obtains a pressure waveform from the input digital signal, and calculates a value obtained by averaging the pressure waveform as a pressure value.

  As described above, in the dialysis apparatus shown in FIG. 9, the pressures at two locations on the blood inlet side and the dialysate outlet side of the dialyzer 76 are measured. Note that pressures at four locations may be measured also on the blood outlet side and the dialysate inlet side (see, for example, Patent Document 1). The measured pressure is used for simulation of the internal filtration flow rate in the dialyzer 76.

  The simulation of the internal filtration flow rate is performed in order to evaluate the dialysis efficiency and the reverse filtration of the dialysate by the internal filtration of the dialyzer 76 (see, for example, Non-Patent Documents 1 and 2). In recent dialysers, the water permeation performance has been improved, but internal filtration is likely to occur, and therefore, the simulation of the internal filtration flow rate is important.

  Moreover, the simulation of an internal filtration flow rate is performed in the following procedures (for example, refer patent document 1, nonpatent literature 1, and nonpatent literature 3). First, a differential equation is established for each of the blood side pressure, dialysate side pressure, blood flow rate, and dialysate flow rate, where x is an arbitrary position in the blood flow direction of the dialyzer 76. Next, by solving these differential equations numerically, the pressure distribution and flow velocity distribution in the dialyzer 76 are obtained.

Thereafter, the blood flow rate, dialysate flow rate, and the like are adjusted by the operator based on the analysis result. Therefore, the burden on the patient is reduced and the patient is prevented from entering a dangerous state. Thus, it is important to accurately measure the pressure from the viewpoint of improving the reliability of the result in the simulation of the internal filtration flow rate.
JP 2003-116985 A Edited by Japan HDF Study Group, “HDF Therapy Handbook”, Nankodo, 2000, p. 169 Edited by Shingo Takezawa, “New high-performance dialyzer for hemodialysis staff”, Tokyo Medical, 1998 Takeshi Sato, 8 others (Academic Committee on Blood Purifier Functional Examination Subcommittee of the Japanese Society for Dialysis Medicine), "Functions and Adaptations of Various Blood Purification Methods-Performance Evaluation Methods and Functional Classification of Blood Purifiers", Japan Dialysis Journal of Medical Society, Japan Dialysis Medical Society, 1996, Vol. 29, No. 8, p. 1231-1245

  However, in a device having a fluid system in which a plurality of liquid delivery devices such as blood pumps and dialysate pumps are installed, such as the conventional dialysis device shown in FIG. 9, the pressure of each liquid delivery device affects each other. Therefore, the pressure waveform at each measurement point obtained by the control device 77 has a complicated shape.

  For example, in a fluid system in which only a single blood pump is provided, a simple pressure waveform composed of a single frequency component (including an attenuation component) is observed. In the provided fluid system, the frequency component of pressure fluctuation in each liquid delivery device is different, so the pressure waveform observed at each measurement point is a complex waveform in which the frequency components of pressure fluctuation in each liquid delivery device are mixed. Become.

  In other words, the blood pressure is affected by the pressure on the dialysate side, and conversely, the pressure on the dialysate side is affected by the pressure on the blood side. Otherwise, an important differential equation in the simulation of the internal filtration flow rate becomes inaccurate. For this reason, in the conventional dialysis machine, there exists a problem that the accurate evaluation by simulation of an internal filtration flow rate cannot be performed.

  Also, for example, when performing long-term treatment by operating the device for a long time, such as continuous blood purification therapy using a blood purification device, clogging occurs in the filtration membrane during treatment, and the membrane The pressure difference may increase. When such clogging occurs, blood purification cannot be performed sufficiently, which causes a serious crisis in the life of the patient.

  For this reason, when performing treatment for a long time, it is required to calculate the transmembrane pressure difference during treatment in order to accurately determine clogging of the filtration membrane (semipermeable membrane). Since the transmembrane pressure difference can be calculated from three pressures on the blood inlet side, blood outlet side, and filtrate outlet side of the blood purifier, it is necessary to provide pressure sensors at these three locations in the apparatus.

  However, as in the case of the dialysis apparatus described above, in this case as well, it is difficult to perform accurate pressure measurement while the apparatus is in operation. Therefore, it is difficult to calculate an accurate transmembrane pressure difference while performing continuous blood purification therapy. For this reason, when continuous blood purification therapy is performed using a conventional device, it is necessary to stop the treatment by stopping the blood pump, the replenisher pump, etc. each time the transmembrane pressure difference is measured.

  An object of the present invention is to provide a pressure measuring device and a pressure measuring method capable of solving the above-described problems and accurately measuring the pressure by each liquid feeding device in a fluid system including a plurality of liquid feeding devices.

  In order to achieve the above object, a pressure measuring device according to the present invention is a pressure measuring device for measuring a pressure of a fluid system including a plurality of liquid feeding devices, and calculates a pressure waveform at a pressure measuring point of the fluid system. A first pressure waveform calculation unit that performs a frequency spectrum calculation unit that calculates a frequency spectrum from the pressure waveform, and a filter that specifies a frequency band that is a noise component and removes the frequency band that is the noise component from the frequency spectrum And a second pressure waveform calculation unit that calculates a pressure waveform from the frequency spectrum from which the frequency band that is the noise component has been removed.

  In order to achieve the above object, a pressure measurement method according to the present invention is a pressure measurement method for measuring a pressure of a fluid system including a plurality of liquid feeding devices, and (a) a pressure measurement of the fluid system. A step of obtaining a pressure waveform at a point; (b) a step of obtaining a frequency spectrum from the pressure waveform; and (c) identifying a frequency band to be a noise component and removing the frequency band to be the noise component from the frequency spectrum. And (d) at least a step of obtaining a pressure waveform from the frequency spectrum from which the frequency band serving as the noise component has been removed.

  Moreover, the present invention may be a program for embodying the pressure measuring method according to the present invention. By installing and executing this program on a computer, the pressure measuring method according to the present invention can be executed. Further, the computer in which this program is installed functions as a pressure measuring device in the present invention.

  As described above, according to the pressure measuring device and the pressure measuring method according to the present invention, it is possible to accurately measure the pressure of each liquid feeding device in a fluid system including a plurality of liquid feeding devices.

  For this reason, when the pressure measuring device and the pressure measuring method according to the present invention are used in a dialysis device, the reliability of the result in the simulation of the internal filtration flow rate can be improved. Therefore, it is possible to accurately grasp the solute removal characteristics accompanying internal filtration in real time, thereby improving dialysis efficiency, safety, and shortening dialysis time.

  Furthermore, when the pressure measuring device and the pressure measuring method according to the present invention are used in a blood purification device, accurate pressure measurement can be performed while performing continuous blood purification therapy. The pressure difference can be calculated. For this reason, a continuous blood purification therapy can be implemented safely compared with the past. Moreover, since the interruption of treatment can be avoided, the burden on the patient can be reduced.

  In the pressure measuring device according to the present invention, the frequency spectrum calculation unit calculates a frequency spectrum by performing Fourier transform on the pressure waveform calculated by the first pressure waveform calculation unit, and the second pressure waveform. It is preferable that the calculation unit calculates the pressure waveform by performing inverse Fourier transform on the frequency spectrum from which the frequency band that is the noise component is removed.

  Further, in the pressure measuring device according to the present invention, the pressure measuring point is plural, a pressure sensor is provided at each pressure measuring point, and the first pressure waveform calculating unit is configured to include the plurality of pressures. It is also preferable that the pressure waveform at each of the pressure measurement points is calculated based on a signal from a pressure sensor provided at each of the measurement points. Further, it is preferable that the plurality of liquid feeding devices are pumps, and the filter unit specifies a frequency band that becomes the noise component based on rotation speed information of the liquid feeding device.

  In the pressure measuring device according to the present invention, the fluid system is provided in a dialysis device including a dialyzer that contacts blood removed from a patient and dialysate through a dialysis membrane, and A blood circuit for circulating the blood extracorporeally through a dialyzer; and a dialysate circuit for supplying the dialysate to the dialyzer and discharging the dialysate from the dialyzer. The pressure measurement points are preferably provided at least on the blood inlet side and dialysate outlet side of the dialyzer.

  Further, in the pressure measuring device according to the present invention, the fluid system is provided in a device having a blood purifier that filters blood removed from a patient through a semipermeable membrane and discharges the filtrate, and A blood circuit for circulating the blood extracorporeally through the blood purifier, and a circuit for discharging the filtrate from the blood purifier, the pressure measuring point being the blood purifier It is also preferable to be provided on the blood inlet side, blood outlet side, and filtrate outlet side.

  In the pressure measurement method according to the present invention, in the step (b), the pressure spectrum obtained in the step (a) is Fourier-transformed to obtain the frequency spectrum, and (d) In this step, it is preferable that the pressure waveform is obtained by performing inverse Fourier transform on the frequency spectrum from which the frequency band serving as the noise component has been removed.

  In the pressure measurement method according to the present invention, the pressure measurement point is plural, and in the step (a), a pressure waveform at each of the pressure measurement points is provided at each of the plurality of pressure measurement points. It is also preferable to adopt a mode that is obtained based on a signal from the pressure sensor.

  In the pressure measuring method according to the present invention, the plurality of liquid feeding devices are pumps, and in the step (c), a frequency band serving as the noise component is determined based on rotation speed information of the liquid feeding device. It is also preferable that the embodiment is specified.

(Embodiment 1)
Hereinafter, the pressure measuring device and the pressure measuring method according to Embodiment 1 of the present invention will be described with reference to FIGS. In the first embodiment, an example in which a pressure measuring device is incorporated in a dialysis device will be described. Initially, the structure of the pressure measuring device in Embodiment 1 is demonstrated using FIG. FIG. 1 is a diagram showing a configuration of a pressure measurement device according to Embodiment 1 of the present invention and a configuration of a dialysis device incorporating the pressure measurement device.

  1 includes an extracorporeal circulation device 11, a dialyzer 16, a control device 17, a blood circuit 22, and a dialysate circuit 23. In the example of FIG. 1, the blood circuit 22 and the dialysate circuit 23 constitute one fluid system.

  The blood circuit 22 includes a blood removal line 22a for sending blood removed from the patient 30 to the dialyzer 16, and a blood return line 22b for returning the blood discharged from the dialyzer 16 to the patient 30. Yes. The dialysate circuit 23 includes a supply line 23 a for sending dialysate to the dialyzer 16 and a drain line 23 b for discharging dialysate from the dialyzer 16.

  Both the blood circuit 22 and the dialysate circuit 23 are connected to the dialyzer 16. Therefore, in the dialyzer 16, the blood of the patient 30 that passes through the blood circuit 22 and the dialysate that passes through the dialysate circuit 23 come into contact with each other through the dialysis membrane of the dialyzer 16. For this reason, the blood is dialyzed and purified in the dialyzer 16.

  In the example of FIG. 1, the dialyzer 16 is a hollow fiber type dialyzer in which a dialysis membrane is formed of a hollow fiber. In the present invention, the type of the dialyzer 16 is not limited to the hollow fiber type, and may be a laminated type or a coil type.

  The extracorporeal circulation device 11 includes a blood pump 13, a water removal pump 14, and a dialysate pump 15. The blood pump 13 is a roller pump and is disposed on the blood removal line 22a. With the operation of the blood pump 13, blood removed from the patient 30 circulates extracorporeally through the dialyzer 16.

  The dialysate pump 15 is disposed on the dialysate circuit 23. The dialysate pump 15 is a dual-type pump having a plunger (not shown) therein, and is provided with a liquid supply side pump (not shown) and a drainage side pump (not shown). Moreover, the liquid supply side pump is arrange | positioned on the liquid supply line 23a, and the drainage side pump is arrange | positioned on the drainage line 23b. In the dialysate pump 15, the flow rate passing through the liquid supply side pump and the flow rate passing through the drainage side pump are always the same.

  The dewatering pump 14 is provided on a bypass 24 that connects the inlet side and the outlet side of the drainage side pump on the drainage line 23b. When the water removal pump 14 is operated, filtration occurs in the dialyzer 16, and excess water is removed from the blood of the patient 30.

  As described above, in the dialysis apparatus shown in FIG. 1 as well, as in the dialysis apparatus shown in FIG. 9 in the background art, a plurality of liquid feeding devices (blood pump 13, dewatering pump 14 and dialysate pump are provided in one fluid system. 15). Further, in the dialyzer shown in FIG. 1, pressure sensors 18, 19, 20 and 21 are provided on the blood inlet side, blood outlet side, dialysate inlet side, and dialysate outlet side of the dialyzer 16, respectively. The pressure is measured at these four locations.

  In the example of FIG. 1, an analog signal corresponding to the pressure of blood or dialysate is output from each of the pressure sensors 18 to 21 to the pressure detection unit 12. Further, the pressure detection unit 12 converts the analog signal output from the pressure sensors 18 to 21 into a digital signal, and outputs the obtained digital signal to the control device 17.

  Further, in the dialysis apparatus shown in the example of FIG. 1, unlike the dialysis apparatus shown in FIG. 9 in the background art, the pressure measuring device 1 according to the first embodiment is incorporated in the control device 17. The pressure measurement device 1 includes a first pressure waveform calculation unit 2, a frequency spectrum calculation unit 3, a filter unit 4, and a second pressure waveform calculation unit 4. The digital signal output from the pressure detector 12 is input to the first pressure waveform calculator 2.

  The first pressure waveform calculation unit 2 calculates a pressure waveform at each pressure measurement point from the digital signal output by the pressure detection unit 12, and outputs this to the frequency spectrum calculation unit 3. The pressure waveform at each pressure measurement point obtained at this time has a complicated shape influenced by the blood pump 13, the water removal pump 14, and the dialysate pump 15.

  The frequency spectrum calculation unit 3 calculates a frequency spectrum from the pressure waveform output from the first pressure waveform calculation unit 2 and outputs the frequency spectrum to the filter unit 3. In the first embodiment, the frequency spectrum is calculated by subjecting the pressure waveform output from the first pressure waveform calculation unit 2 to Fourier transform such as fast Fourier transform. A specific method of Fourier transform is described in, for example, Yoshihiro Tashiro, Applied Mathematics Series 1 “Laplace transform and Fourier analysis”, published by Morikita Publishing, 1977.

  The filter unit 4 identifies a frequency band that becomes a noise component, and removes a frequency band that becomes a noise component from the frequency spectrum output by the frequency spectrum calculation unit 3. Further, the filter unit 4 outputs the frequency spectrum from which the frequency band that is a noise component is removed to the second pressure waveform calculation unit 5.

  In the first embodiment, the frequency band that becomes a noise component by the filter unit 4 is specified by specifying the rotation speeds of the blood pump 13, the water removal pump 14, the dialysate pump 15, the supply side pump and the drainage side pump Is performed based on information to be performed (hereinafter referred to as “rotational speed information”).

  Specifically, as shown in FIG. 1, a sensor (not shown) for detecting the rotation of the pump is attached to each pump, and a signal (rotational speed information) output from the sensor attached to each pump. ) Is input to the filter unit 4. Therefore, the filter unit 4 first detects the rotation speed of each pump from the signal input from each pump, and calculates the frequency of each pump from the detected rotation speed. The frequency of each pump is calculated based on, for example, Satoshi Soeda, et al., Science and Engineering Basic Series “Basics of Vibration Engineering”, Nisshin Publishing, 1989.

  Next, if the frequency spectrum is based on a signal from the sensor 18 (blood inlet side of the dialyzer 16) or the sensor 19 (blood outlet side of the dialyzer 16), the filter unit 4 is, for example, the water removal pump 14. And the frequency band including the frequency of the dialysate pump 15 are determined as noise components.

  Moreover, if the frequency spectrum is based on the signal from the sensor 20 (dialysate outlet side of the dialyzer 16), the filter unit 4 determines that the frequency band including the frequency of the blood pump 13 is a noise component.

  Further, if the frequency spectrum is based on the sensor 21 (dialysate inlet side of the dialyzer 16), the filter unit 4 includes a frequency band including the frequency of the blood pump 13 and a frequency band including the frequency of the dewatering pump 14. Are determined as noise components.

  When the frequency band that becomes the noise component can be specified, the filter unit 4 removes the frequency band that becomes the specified noise component for each frequency spectrum. In the first embodiment, the removal from the frequency spectrum of the frequency band specified as the noise component is performed based on the signal processing described in, for example, Nozomi Hamada, “Signal Processing”, published by Ohmsha, 1995. ing.

  The second pressure waveform calculation unit 5 calculates a pressure waveform from the frequency spectrum from which the frequency band that is a noise component has been removed. In the first embodiment, the calculation of the pressure waveform by the second pressure waveform calculation unit 5 is performed by performing an inverse Fourier transform on the frequency spectrum from which the frequency band that is a noise component has been removed. A specific method of the inverse Fourier transform is also described in the above-mentioned Yoshihiro Tashiro, Applied Mathematics Series 1 “Laplace transform and Fourier analysis theory”, published by Morikita Publishing, 1977.

  The second pressure waveform calculator 5 can also calculate a final pressure value based on the obtained pressure waveform. As a final pressure value calculation method, for example, a method of averaging pressure waveforms can be cited. The calculated pressure waveform or pressure value at each measurement point is output to a storage device (not shown) of the control device 17 and stored in this storage device. The control device 17 reads the pressure waveform or pressure value stored in the storage device and simulates the internal filtration flow rate. The result is displayed by a display device (not shown).

  In the first embodiment, the internal filtration flow rate can also be calculated. Specifically, the control device 17 first performs an internal filtration simulation in units of μs based on the pressure waveform calculated by the second pressure waveform calculation unit 5. Next, based on this result, the internal filtration flow rate is integrated with respect to the time axis.

  In the first embodiment, the pressure waveform or pressure value is calculated at four locations on the blood inlet side, blood outlet side, dialysate inlet side, and dialysate outlet side of the dialyzer 16. However, the present invention is not limited to this. For example, if only simulation of the internal filtration flow rate is performed, the pressure waveforms or pressure values at two locations on the blood inlet side and the dialysate outlet side may be calculated. In this case, pressure sensors need only be provided at two locations on the blood inlet side and the dialysate outlet side.

  In the first embodiment, the example in which the extracorporeal circulation device 11 and the control device 17 in which the pressure measurement device 1 is incorporated is configured as separate devices is described. However, the pressure measurement device 1 is incorporated. The control device 17 may be incorporated in the extracorporeal circulation device 11. In the first embodiment, the example in which the pressure measuring device 1 is incorporated in the control device 17 is described. However, the pressure measuring device 1 and the control device 17 may be separate. Further, the control device 17 and the extracorporeal circulation device 11 may be configured integrally, and the pressure measuring device 1 may be configured separately from these.

  Next, the pressure measuring method in Embodiment 1 of this invention is demonstrated using FIGS. However, the pressure measuring method according to the first embodiment is implemented by operating the pressure measuring device according to the first embodiment shown in FIG. Therefore, in the following, the pressure measurement method in the first embodiment will be described by describing the operation of the pressure measurement device in the first embodiment with reference to FIG. 1 as appropriate.

  FIG. 2 is a flowchart showing the operation of the pressure measurement method and the pressure measurement device according to Embodiment 1 of the present invention. In the example of FIG. 2, pressure measurement is performed in parallel with hemodialysis (extracorporeal circulation) using a dialysis machine. Therefore, after the hemodialysis by a dialysis apparatus is started, step S1-step S9 shown below are performed.

  First, as shown in FIG. 2, the first pressure waveform calculation unit 2 determines whether or not a pressure measurement point has been selected (step S1). Specifically, it is determined whether or not a selection signal for notifying the selected pressure measurement point is input from the control device 17. The selection signal is input, for example, when the operator of the dialysis machine instructs the control device 17 to measure the pressure measurement point, that is, when the control device 17 simulates the internal filtration flow rate.

  When the pressure measurement point is not selected, the pressure measurement device 1 is in a standby state. On the other hand, when the pressure measurement point is selected, the first pressure waveform calculation unit 2 outputs the pressure from the pressure sensor (any or all of the pressure sensors 18 to 21) at the selected pressure measurement point, and detects the pressure. A pressure waveform is calculated from the signal digitally converted by the unit 12 (step S2). Note that the calculation of the pressure waveform is performed for each selected pressure measurement point. The calculated pressure waveform is output to the frequency spectrum calculation unit 3.

  FIG. 3 is a diagram illustrating an example of a pressure waveform calculated by the first pressure waveform calculation unit 2. As shown in FIG. 3, when the pressure waveform is calculated based on the signal output from the pressure sensor, the pressure waveform has a complicated shape as described in the background art. This is because, during hemodialysis, the blood pump 13, the dialysate pump (feeding side pump and drainage side pump) 15, and the water removal pump 14 are operated, so these effects are not affected at each pressure measurement point. To receive.

  Next, the frequency spectrum calculation unit 3 performs a Fourier transform on the pressure waveform output from the first pressure waveform calculation unit 2 to calculate a frequency spectrum (step S4). Further, the frequency spectrum calculation unit 3 outputs the calculated frequency spectrum to the filter unit 4. FIG. 4 is a diagram illustrating an example of a frequency spectrum calculated by the frequency spectrum calculation unit 3. As can be seen from the frequency spectrum shown in FIG. 4, five peaks of A, B, C, D, and E are observed.

  Next, the filter part 4 detects the rotation speed of each pump from the signal from the sensor attached to each pump, and calculates the frequency of each pump from the detected rotation speed (step S4). By performing step S4, it is determined what each peak shown in FIG. 4 indicates.

  In FIG. 4, A indicates a peak of frequency (about 0.5 Hz) calculated from the rotation period (about 2 seconds) of the roller in blood pump 13. B shows the peak (about 0.6 Hz) of the low frequency component of the frequency calculated from the reciprocating period (about 1.7 seconds) of the plunger of the dialysate pump 15.

  C indicates the frequency peak (about 1.0 Hz) calculated from the discharge cycle (about 1 second) in the blood pump 13. D and E indicate the peaks (D: about 1.2 Hz, E: about 1.8 Hz) of the high frequency component of the frequency calculated from the reciprocating cycle (about 1.7 seconds) of the plunger of the dialysate pump 15. .

  Next, the filter unit 4 specifies a frequency that becomes a noise component by specifying a pump that causes noise for each selected pressure measurement point (step S5). Further, the filter unit 4 removes the frequency band including the identified frequency from the frequency spectrum obtained in step S3 (step S6).

  FIG. 5 is a diagram illustrating an example of a frequency spectrum from which a frequency band that is a noise component is removed by the filter unit 4. In the example of FIG. 5, the frequency band including B, D, and E peaks is removed from the frequency spectrum shown in FIG. That is, components other than the frequency component of the blood pump 13 are removed. The frequency spectrum from which the frequency band that is a noise component is removed is output to the second pressure waveform calculation unit 5.

  Next, the 2nd pressure waveform calculation part 5 performs a reverse Fourier transform with respect to the frequency spectrum from which the frequency band used as a noise component was removed, and calculates a pressure waveform (step S7). Although not shown, the second pressure waveform calculation unit 5 calculates a pressure value in addition to the pressure waveform when instructed by the operator.

  FIG. 6 is a diagram illustrating an example of a pressure waveform calculated by the second pressure waveform calculation unit 5. As can be seen from FIG. 6, since the noise component is removed by the filter unit 4, each wave has the same shape, and a regularly continuous pressure waveform is observed.

  Next, the calculated pressure waveform is output to the control device 17 by the second pressure waveform calculation unit 5 (step S8). If the pressure value is calculated, the calculated pressure value is also output to the control device 17. Thereafter, in the pressure measuring device 1, it is determined whether or not the extracorporeal circulation has ended (step S9). If the extracorporeal circulation has not ended, the process is executed again from step S1. On the other hand, when the extracorporeal circulation is finished, the processing in the pressure measuring device 1 is finished.

  As described above, according to the pressure measuring device and the pressure measuring method in Embodiment 1, a pressure waveform from which noise components are removed can be obtained in a fluid system in which a plurality of liquid delivery devices such as pumps are installed. . For this reason, the pressure by only the liquid feeding apparatus which is feeding the fluid which passes a pressure measurement point can be measured correctly.

  As a result, when the pressure measuring device and the pressure measuring method according to Embodiment 1 are applied to a dialysis device, the reliability of the result in the simulation of the internal filtration flow rate can be improved. Therefore, it is possible to accurately grasp the solute removal characteristics accompanying internal filtration in real time, thereby improving dialysis efficiency, safety, and shortening dialysis time.

  The pressure measuring apparatus according to the first embodiment can also be realized by installing a program for realizing steps S1 to S9 shown in FIG. 2 in a computer and executing the program. In this case, a central processing unit (CPU) of the computer functions as a first pressure waveform calculation unit 2, a frequency spectrum calculation unit 3, a filter unit 4, and a second pressure waveform calculation unit 5 to perform processing. Further, if the control device 17 is realized by a computer, the pressure measurement of the present invention can also be performed by installing a program for implementing steps S1 to S9 shown in FIG. An apparatus can be realized.

(Embodiment 2)
Next, a pressure measuring device and a pressure measuring method according to Embodiment 2 of the present invention will be described with reference to FIG. In the second embodiment, an example in which a pressure measuring device is incorporated in an artificial cardiopulmonary device will be described. FIG. 7 is a diagram showing the configuration of the pressure measurement device according to Embodiment 2 of the present invention and the configuration of a heart-lung machine incorporating the pressure measurement device.

  The cardiopulmonary apparatus shown in FIG. 7 is used for temporarily substituting the functions of the heart 31 and lungs (not shown) of the patient 30 during cardiovascular surgery or the like. As shown in FIG. 7, the heart-lung machine includes an extracorporeal circulation device 41 and a control device 47. The extracorporeal circulation device 41 includes a blood reservoir 42, a blood pump 43, an artificial lung 44, a pressure detection unit 46, and a blood circuit 48.

  In the oxygenator shown in FIG. 7, when the extracorporeal circulation device 41 is operated, the blood removed from the vena cava 33 of the patient 30 is temporarily stored in the blood reservoir 42. Thereafter, the blood is pumped to the artificial lung 44 by the blood pump 43. The blood sent to the oxygenator 44 is oxygenated by the oxygenator 44 and then returned to the aorta 32 of the patient 30.

  Generally, in an oxygenator, it is necessary to remove blood from the vena cava 33 of the patient 30 to the blood reservoir 42 as shown in FIG. As the main methods of blood removal, there are a drop blood removal method, a pump blood removal method, and a negative pressure blood removal method. In the heart-lung machine shown in FIG. 7, the negative pressure blood removal method is applied. .

  When the negative pressure blood removal method is applied to the heart-lung machine shown in FIG. 7, a negative pressure pump (not shown) is disposed in the blood reservoir 42. Further, when such a negative pressure pump is arranged, in order to prevent an increase in pressure in the blood reservoir caused by blockage of a line connecting the negative pressure pump and the blood reservoir 42, the pressure inside the blood reservoir 42 is reduced. It is necessary to measure.

  Therefore, in the heart-lung machine shown in FIG. 7, a pressure sensor 45 that measures the pressure inside the blood reservoir 42 is provided in the blood reservoir 42, and a signal is output from the pressure sensor 45 to the pressure detector 46. . The pressure detection unit 46 is the same as the pressure detection unit 46 of the dialysis apparatus shown in FIG. 1 in the first embodiment. The pressure detection unit 46 converts the analog signal output from the pressure sensor 45 into a digital signal and controls the control unit 47. To output.

  Incidentally, in the heart-lung machine shown in FIG. 7, a suction pump 49 and a suction circuit 50 are provided to suck blood that has bleed in the surgical field. The opposite side of the suction circuit 50 from the patient 30 is connected to the blood reservoir 42. For this reason, in the oxygenator shown in FIG. 7, the pressure in the blood reservoir 42 fluctuates due to pressure fluctuations by the suction pump 49, so that the pressure waveform obtained from the digital signal converted by the pressure detector 46 has a complicated shape. It becomes difficult to accurately measure the pressure in the blood reservoir 42.

  However, in the oxygenator shown in FIG. 7, the pressure measuring device 1 according to the second embodiment is incorporated in the control device 47. In addition, the pressure measuring device 1 in the second embodiment is similar to the pressure measuring device in the first embodiment in that the first pressure waveform calculating unit 2, the frequency spectrum calculating unit 3, the filter unit 4, and the second pressure And a waveform calculation unit 5.

  Further, a sensor for detecting the rotation of the suction pump 49 is attached to the suction pump 49, and a signal (rotational speed information) output from the sensor is input to the filter unit 4. Similarly, a sensor for detecting the rotation of the blood pump 43 is also attached to the blood pump 43, and a signal (rotational speed information) output from the sensor is input to the filter unit 4. .

  For this reason, in the second embodiment, when a digitally converted signal is input from the pressure detection unit 46 to the pressure device 1, the first pressure waveform calculation unit 2 first performs the same as in the first embodiment. A pressure waveform is calculated. Next, the frequency spectrum calculation unit 2 performs a Fourier transform of the pressure waveform to calculate a frequency spectrum.

  Next, the filter unit 4 calculates the frequencies of the suction pump 49 and the blood pump 43, specifies a frequency band including the calculated frequency as a noise component, and removes a frequency band that becomes a noise component from the frequency spectrum. Next, the second pressure waveform calculation unit 5 performs an inverse Fourier transform of the frequency spectrum from which the frequency band that is a noise component is removed, thereby calculating a pressure waveform. Thereafter, the second pressure waveform calculation unit 5 outputs the calculated pressure waveform. Also in the second embodiment, the second pressure waveform calculation unit 5 can calculate the pressure value.

  As described above, according to the second embodiment, the pressure waveform or pressure value from which the influence due to the pressure fluctuation of the suction pump 49 is removed can be obtained as the pressure waveform or pressure value in the blood reservoir 42. Therefore, when the pressure measuring device and the pressure measuring method according to the second embodiment are applied to the heart-lung machine, the pressure waveform or pressure value in the blood reservoir 42 can be accurately measured. Accurately grasp. For this reason, according to this Embodiment 2, a safe extracorporeal circulation can be implemented in open heart surgery.

(Embodiment 3)
Next, a pressure measuring device and a pressure measuring method according to Embodiment 3 of the present invention will be described with reference to FIG. In the third embodiment, an example in which a pressure measuring device is incorporated in a blood purification device will be described. Further, in the blood purification apparatus shown in the third embodiment, continuous blood purification therapy is performed. For this reason, in order to perform safe blood purification (filtration), the transmembrane pressure difference is calculated in the third embodiment.

  FIG. 8 is a diagram showing the configuration of the pressure measurement device according to Embodiment 3 of the present invention and the configuration of a blood purification device incorporating the pressure measurement device. The blood purification apparatus shown in FIG. 8 includes an extracorporeal circulation device 51, a blood purification device 56, a control device 57, a replacement fluid circuit 61, a blood circuit 62, and a filtrate discharge circuit 63. In the blood purification apparatus shown in FIG. 8, one fluid system is configured by the replacement fluid circuit 61, the blood circuit 62, and the filtrate discharge circuit 63.

  The extracorporeal circulation device 51 includes a pressure detector 52, a blood pump 53, a filtrate pump 54, and a replenisher pump 55. Blood pump 53, filtrate pump 54, and replenisher pump 55 are all roller pumps. The blood pump 53 is disposed on the blood circuit 62, the filtrate pump 54 is disposed on the filtrate discharge circuit 63, and the replenisher pump 55 is disposed on the replenisher circuit 61.

  The blood circuit 62 is a circuit for circulating blood exsanguinated from the patient 30 via the blood purifier 56. The blood circuit 62 also includes a blood removal line 62a for sending blood removed from the patient 30 to the blood purifier 56, and a blood return line 62b for returning the blood filtered by the blood purifier 56 to the patient 30. It consists of and. The blood pump 53 is provided on the blood removal line 62 a, and the blood is sent to the blood purifier 56 by the operation of the blood pump 53.

  The blood sent to the blood purifier 56 is filtered by a semipermeable membrane (not shown) provided in the blood purifier 56. The filtrate produced by this filtration is discharged through the filtrate discharge circuit 63 by the filtrate pump 54. A replacement fluid circuit 61 is connected to the blood return line 62b. Therefore, when the replenisher pump 55 is operated, the replacement fluid is applied to the blood filtered by the blood purifier 56.

  In the blood purification apparatus shown in FIG. 8, the extracorporeal circulation apparatus 51 normally has the flow rate of the filtrate pump 54 equal to the sum of the flow rate of the replenisher pump and the amount of water removed from the blood per unit time. The filtrate pump 54 and the replenisher pump 55 are controlled.

  Further, as shown in FIG. 8, in the third embodiment, pressure is measured at three locations in order to calculate the transmembrane pressure difference. Specifically, pressure sensors 58, 59, and 60 that output analog signals according to pressure are provided on the blood inlet side, blood outlet side, and filtrate outlet side of the blood purifier 56, respectively. The pressure detector 52 is the same as the pressure detector 12 shown in FIG. 1 in the first embodiment, converts the analog signal output from the pressure sensors 58 to 60 into a digital signal, and obtains the digital signal Is output to the control device 57.

  As described above, also in the blood purification apparatus shown in FIG. 8, a plurality of liquid feeding devices (blood pump 53, filtrate pump 54, and replenisher pump) are provided in one fluid system, as in the dialysis apparatus shown in the first embodiment. 55). Therefore, similarly to Embodiments 1 and 2, also in the blood purification apparatus shown in FIG. 8, the pressure waveform at each measurement point has a complicated shape.

  Therefore, also in the third embodiment, the control device 57 includes the pressure measuring device 1 as in the control device 17 shown in FIG. 1 in the first embodiment. Further, the pressure measuring device 1 in the present third embodiment is also similar to the pressure measuring device in the first embodiment in that the first pressure waveform calculating unit 2, the frequency spectrum calculating unit 3, the filter unit 4, and the second pressure And a waveform calculation unit 5.

  Further, each of the blood pump 53, the filtrate pump 54, and the replenisher pump 55 is provided with a sensor (not shown) for detecting the rotation of the roller, and the signal (rotational speed information) output from the sensor is a filter. It is input to the part 4.

  Therefore, also in the third embodiment, when a digitally converted signal is input from the pressure detection unit 52 to the pressure device 1, the first pressure waveform calculation unit 2 first performs the same as in the first embodiment. A pressure waveform is calculated. Next, the frequency spectrum calculation unit 2 performs a Fourier transform of the pressure waveform to calculate a frequency spectrum.

  Next, the filter unit 4 calculates the frequencies of the blood pump 53, the filtrate pump 54 and the replenisher pump 55. Further, a frequency band including the calculated frequency is specified as a noise component, and a frequency band that becomes a noise component is removed from the frequency spectrum. Next, the second pressure waveform calculation unit 5 performs an inverse Fourier transform of the frequency spectrum from which the frequency band that is a noise component is removed, thereby calculating a pressure waveform. Thereafter, the second pressure waveform calculation unit 5 outputs the calculated pressure waveform. Also in the third embodiment, the second pressure waveform calculation unit 5 can calculate the pressure value.

  As described above, according to the third embodiment, the pressure waveform from which the influence (noise component) due to the pressure fluctuation is removed as the pressure waveforms on the blood inlet side, the blood outlet side, and the filtrate outlet side of the blood purifier 56. A waveform can be obtained. Therefore, it is possible to accurately measure the pressure by only the liquid delivery device that delivers the fluid passing through the pressure measurement point.

  For this reason, according to the blood purification apparatus shown in FIG. 8, it is possible to calculate an accurate transmembrane pressure difference while continuing the treatment without stopping the continuous blood purification therapy. Therefore, since the clogging of the semipermeable membrane can be accurately determined, the safety of treatment can be improved. Furthermore, since the treatment is avoided from being interrupted every time the transmembrane pressure difference is calculated, the burden on the patient can be reduced.

  While performing hemodialysis with the dialyzer shown in FIG. 1, the pressure [mmHg] on the blood inlet side in the dialyzer 6 was measured using the pressure measuring device and the pressure measuring method in the first embodiment. However, the measurement conditions were set such that the blood flow rate was 200 [mL / min], the dialysate flow rate was 500 [mL / min], the dewatering flow rate was 15 [mL / min], and the measurement time was 60 [seconds]. The results are shown in Table 1. The measurement conditions are set according to “(Appendix) Evaluation Method of Blood Purifier” described in Non-Patent Document 3 described above.

(Comparative example)
As a comparative example, while performing hemodialysis with the dialyzer shown in FIG. 1, a pressure waveform is calculated using the digitally converted signal from the pressure sensor 18 as it is, and from this, the pressure [mmHg on the blood inlet side in the dialyzer 6 is calculated. ] Was requested. The measurement conditions were set in the same manner as in the above example. The results are shown in Table 1.

(Reference example)
As a reference example, in the state where only the blood pump 13 is operated in the dialysis apparatus shown in FIG. 1, the pressure waveform is calculated from the digitally converted signal from the pressure sensor 18, and the pressure on the blood inlet side in the dialyzer 6 is calculated therefrom. [MmHg] was determined. The results are shown in Table 1.

  As can be seen from the results in Table 1, if the pressure measuring device and the pressure measuring method in Example 1 are used, the measured pressure can be an average value, a maximum value, or a minimum value. It is a value approximated to the case where only 13 is operated and measured. On the other hand, in the comparative example, the measured pressure is higher by 10% or more than when only the blood pump 13 is operated, regardless of the average value, the maximum value, or the minimum value. Thus, according to the present invention, even when each liquid feeding device is operating in a fluid system including a plurality of liquid feeding devices, the pressure by each liquid feeding device can be accurately measured. For example, when applied to a hemodialyzer, accurate pressure measurement can be performed while hemodialysis is continued.

  The pressure measuring device and the pressure measuring method in the present invention can be applied without particular limitation as long as it is a fluid system including a plurality of liquid feeding devices, and the pressure by each liquid feeding device in this fluid system can be accurately measured. In addition, the pressure measuring device and the pressure measuring method according to the present invention are particularly effective in dialysis devices, blood purification devices, and heart-lung machines.

It is a figure which shows the structure of the pressure measuring device in Embodiment 1 of this invention, and the structure of the dialysis apparatus incorporating the pressure measuring device. It is a flowchart which shows the operation | movement of the pressure measuring method and pressure measuring apparatus in Embodiment 1 of this invention. It is a figure which shows an example of the pressure waveform calculated by the 1st pressure waveform calculation part. It is a figure which shows an example of the frequency spectrum calculated by the frequency spectrum calculation part. It is a figure which shows an example of the frequency spectrum from which the frequency band used as a noise component was removed by the filter part. It is a figure which shows an example of the pressure waveform calculated by the 2nd pressure waveform calculation part. It is a figure which shows the structure of the pressure measuring device in Embodiment 2 of this invention, and the structure of the heart-lung machine in which the pressure measuring device was integrated. It is a figure which shows the structure of the pressure measuring device in Embodiment 3 of this invention, and the structure of the blood purification apparatus incorporating the pressure measuring device. It is a schematic block diagram which shows an example of the conventional hemodialysis apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure measuring device 2 1st pressure waveform calculation part 3 Frequency spectrum calculation part 4 Filter part 5 2nd pressure waveform calculation part 11, 41, 51 Extracorporeal circulation device 12, 46, 52 Pressure detection part 13, 43, 53 Blood pump 14 Dewatering pump 15 Dialysate pump 16 Dialyzer 17, 47, 57 Control device 18, 19, 20, 21, 45, 58, 60 Pressure sensor 22, 48, 62 Blood circuit 22a, 62a Blood removal line 22b, 62b Blood Blood return line 23 Dialysate circuit 23a Supply line 23b Drain line 24 Bypass 30 Patient 31 Heart 32 Aorta 33 Vena cava 42 Blood reservoir 44 Artificial lung 49 Suction pump 50 Suction circuit 54 Filtrate pump 55 Replenisher pump 56 Blood purifier 61 Fluid replacement circuit 63 Filtrate drain circuit

Claims (14)

A pressure measuring device for measuring a pressure of a fluid system including a plurality of liquid feeding devices,
A first pressure waveform calculation unit for calculating a pressure waveform at a pressure measurement point of the fluid system;
A frequency spectrum calculation unit for calculating a frequency spectrum from the pressure waveform;
A filter unit that identifies a frequency band that becomes a noise component and removes the frequency band that becomes the noise component from the frequency spectrum;
A pressure measurement device comprising at least a second pressure waveform calculation unit that calculates a pressure waveform from the frequency spectrum from which the frequency band that is the noise component has been removed. The frequency spectrum calculation unit calculates a frequency spectrum by performing Fourier transform on the pressure waveform calculated by the first pressure waveform calculation unit;
The pressure measurement device according to claim 1, wherein the second pressure waveform calculation unit calculates a pressure waveform by performing inverse Fourier transform on the frequency spectrum from which the frequency band that is the noise component is removed. A plurality of pressure measurement points, each pressure measurement point is provided with a pressure sensor;
The pressure measurement device according to claim 1, wherein the first pressure waveform calculation unit calculates a pressure waveform at each of the pressure measurement points based on a signal from a pressure sensor provided at each of the plurality of pressure measurement points. The plurality of liquid feeding devices are pumps;
The pressure measuring device according to claim 1, wherein the filter unit specifies a frequency band that becomes the noise component based on rotation speed information of the liquid feeding device. The fluid system is provided in a dialysis apparatus including a dialyzer that contacts blood removed from a patient and dialysate through a dialysis membrane, and circulates the blood extracorporeally through the dialyzer. And a blood circuit for supplying the dialysate to the dialyzer and discharging the dialysate from the dialyzer,
The pressure measuring device according to claim 1, wherein the pressure measuring points are provided at least on a blood inlet side and a dialysate outlet side of the dialyzer. The fluid system is provided in a device having a blood purifier that filters blood removed from a patient through a semipermeable membrane and discharges the filtrate, and circulates the blood through the blood purifier extracorporeally. A circuit for discharging the filtrate and the circuit for discharging the filtrate from the blood purifier,
The pressure measuring device according to claim 1, wherein the pressure measuring points are provided on a blood inlet side, a blood outlet side, and a filtrate outlet side of the blood purifier. A pressure measurement method for performing pressure measurement of a fluid system including a plurality of liquid feeding devices,
(A) obtaining a pressure waveform at a pressure measurement point of the fluid system;
(B) obtaining a frequency spectrum from the pressure waveform;
(C) identifying a frequency band to be a noise component and removing the frequency band to be the noise component from the frequency spectrum;
(D) A pressure measurement method comprising: at least a step of obtaining a pressure waveform from the frequency spectrum from which the frequency band serving as the noise component has been removed. In the step (b), the frequency spectrum is obtained by Fourier transforming the pressure waveform obtained in the step (a),
The pressure measurement method according to claim 7, wherein, in the step (d), a pressure waveform is obtained by performing inverse Fourier transform on the frequency spectrum from which the frequency band serving as the noise component has been removed. A plurality of pressure measurement points;
The pressure measurement method according to claim 7, wherein, in the step (a), a pressure waveform at each of the pressure measurement points is obtained based on a signal from a pressure sensor provided at each of the plurality of pressure measurement points. The plurality of liquid feeding devices are pumps;
The pressure measurement method according to claim 7, wherein in the step (c), a frequency band to be the noise component is specified based on rotation speed information of the liquid feeding device. A program which is read into a computer and causes the computer to perform pressure measurement of a fluid system including a plurality of liquid feeding devices,
(A) obtaining a pressure waveform at a pressure measurement point of the fluid system;
(B) obtaining a frequency spectrum from the pressure waveform;
(C) identifying a frequency band to be a noise component and removing the frequency band to be the noise component from the frequency spectrum;
(D) causing the computer to execute a step of obtaining a pressure waveform from the frequency spectrum from which the frequency band that is the noise component is removed. In the step (b), the frequency spectrum is obtained by Fourier transforming the pressure waveform obtained in the step (a),
12. The program according to claim 11, wherein, in the step (d), a pressure waveform is obtained by performing inverse Fourier transform on the frequency spectrum from which the frequency band serving as the noise component has been removed. A plurality of pressure measurement points;
The program according to claim 11, wherein, in the step (a), the pressure waveform at each of the pressure measurement points is obtained based on a signal from a pressure sensor provided at each of the plurality of pressure measurement points. The plurality of liquid feeding devices are pumps;
The program according to claim 11, wherein in the step (c), a frequency band to be the noise component is specified based on rotation speed information of the liquid feeding device.

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