JP6301696B2 - Flow sensor, extracorporeal circulation apparatus provided with flow sensor, and control method thereof - Google Patents

Description

  The present invention relates to an extracorporeal circulation apparatus that transfers blood outside a patient's body for circulation.

  For example, when performing cardiac surgery on a patient, the pump of the extracorporeal circulation device is operated to remove blood from the patient's vein (vena cava), and after exchanging the gas in the blood using an artificial lung, Perform extracorporeal blood circulation back to the patient's artery (aorta). In order to appropriately perform such surgery and treatment, it is necessary to accurately grasp the blood flow rate value by the pump.

  Patent Document 1 shows a flow rate estimation method for an implantable pump that is different from the extracorporeal circulation device. In this pump flow rate estimation method, it is possible to suppress deterioration in accuracy of the estimation result of the blood discharge flow rate due to individual differences in pump characteristics. In the first step of the pump flow rate estimation method, a step of creating a general flow rate estimation formula including a correction term using each of a plurality of pumps, and a measurement term obtained using an actual pump embedded in the patient's body are corrected terms. And a step of creating a flow rate estimation formula in the actual pump from the general flow rate estimation formula. Then, in the second step, the rotational speed N of the motor in the pump actual machine implanted in the patient's body, the current consumption I of the motor, and the attribute data Z of the patient's blood are measured, and the flow rate estimation formula and these values in the pump actual machine are measured. Based on N, I and Z, the flow rate of the pump is estimated.

  When estimating the flow rate of this pump, in the second step, as described in paragraph No. 0033 of Patent Document 1, patient blood attribute data Z is used instead of measuring the blood viscosity and density of the patient. The hematocrit value of the patient's blood is measured, and the discharge flow rate of the pump is estimated using the converted viscosity and the converted density obtained by conversion from the hematocrit value.

JP 2010-119859 A

  In the estimation method of the discharge flow rate of the pump described in Patent Document 1, the actual viscosity of the pump embedded in the patient's body is measured, and the converted viscosity obtained by converting the hematocrit value from the hematocrit value and The pump discharge flow rate is estimated using the converted density.

  Since this method is only an estimation method, it cannot be expected as a strict flow rate management method for extracorporeal circulation procedures.

One of the commonly used methods for strict flow rate control is a propagation time difference type flow meter that uses ultrasonic waves, but there are some ultrasonic flow time difference type flow meters outside the tube that sends blood. In some cases, measurement is performed by transmitting an ultrasonic wave from the sensor, and therefore, accuracy is affected not only by parameters of blood (blood) and temperature to be measured but also by tube conditions.
The inventor paid attention to the fact that the propagation path of the ultrasonic wave is deviated when these parameters related to the measured flow rate deviate from a specific calibration condition. If the propagation path of the ultrasonic wave is deviated, an error occurs in the calculation of the flow measurement because the ultrasonic intensity and the ultrasonic wave propagation time when reaching the ultrasonic receiving device are different from those at the time of calibration.

  Therefore, when the blood circulation is performed by operating the pump, the present invention is adapted to the change in blood characteristics of the patient that changes from moment to moment, and is adapted to the tube used at that time and the blood flow rate value. It is an object of the present invention to provide a flow sensor capable of accurately measuring the flow rate, an extracorporeal circulation device using the flow sensor, and a control method thereof.

The extracorporeal circulation apparatus of the present invention is an extracorporeal circulation apparatus that circulates the blood of a patient outside the patient's body using a pump arranged in the circulation circuit, and is arranged in the circulation circuit formed by an elastic tube. A flow sensor for obtaining a measured flow value of the blood passing through the circulation circuit using an ultrasonic signal, a temperature sensor for obtaining an ambient temperature, and the circulation sensor disposed in the circulation circuit and passing through the circulation circuit. A measuring unit that measures a hematocrit value of blood; and a timer that measures a time related to transmission / reception of the ultrasonic wave, and is opposed to the inside of the flow rate sensor at a position displaced with the circulation circuit interposed therebetween. An ultrasonic transmission apparatus provided, an ultrasonic reception apparatus that receives ultrasonic waves transmitted from the ultrasonic transmission apparatus, and an angle change that changes a transmission angle of the ultrasonic waves of the ultrasonic transmission apparatus To Yes and location, and the ultrasonic transmitting unit and the control unit and the ultrasonic receiving device is connected. The control unit calculates an ultrasonic wave propagation velocity of the blood based on the blood temperature measurement value measured by the temperature sensor and the hematocrit value measured by the measurement unit, and is measured by the timer And the ultrasonic wave of the elastic tube based on the time from when the ultrasonic wave transmission device transmits the ultrasonic wave to when the ultrasonic wave reception device receives the ultrasonic wave and the ultrasonic wave propagation velocity of the blood. Calculate a propagation speed, calculate a refraction angle at the boundary between the elastic tube and the blood based on the ultrasonic propagation speed of the blood and the ultrasonic propagation speed of the elastic tube, and based on the refraction angle characterized by being configured to the measurement accurately measured flow rate value of the adjusted the blood by the angle changing device transmission angle of the ultrasonic wave from the ultrasonic transmitting device.
According to the above configuration, the extracorporeal circulation device of the present invention includes a flow rate sensor, a temperature sensor, a measurement unit that measures a hematocrit value of blood, and a timer that measures a time related to transmission / reception of ultrasonic waves. The flow rate sensor includes an ultrasonic transmission device provided so as to face each other at a position shifted with respect to the circulation circuit, an ultrasonic reception device that receives ultrasonic waves transmitted from the ultrasonic transmission device, and the ultrasonic transmission device An angle changing device for changing the transmission angle of the ultrasonic wave, and a control unit . The control unit calculates the ultrasonic propagation velocity of the blood based on the blood temperature measurement value measured by the temperature sensor and the hematocrit value measured by the measurement unit. In addition, the control unit is an elastic tube based on the time measured by the timer until the ultrasonic transmission device receives the ultrasonic wave after the ultrasonic transmission device transmits the ultrasonic wave, and the ultrasonic wave propagation velocity of the blood. Calculate the ultrasonic wave propagation speed. Further, the control unit calculates a refraction angle at the boundary between the elastic tube and blood based on the ultrasonic propagation velocity of blood and the ultrasonic propagation velocity of the elastic tube. And a control part adjusts the transmission angle of the said ultrasonic wave from an ultrasonic transmission apparatus with the said angle change apparatus based on the calculated refraction angle . Thereby , since the propagation path from the said ultrasonic transmitter to the said ultrasonic receiver can be adjusted correctly and can be measured, flow measurement accuracy improves.

Preferably, the said in response to the transmission angle of the ultrasonic waves have a measuring device for ultrasonic wave reception intensity at the ultra sound Nami受 communication apparatus, and ultrasonic reception intensity is given to the control unit, the control unit Therefore, the transmission angle of the ultrasonic wave is determined at a location where the reception intensity is strongest.
According to the above configuration, in the ultrasonic receiver that receives the ultrasonic wave transmitted while adjusting the transmission angle from the ultrasonic transmitter, the ultrasonic reception intensity measuring device detects a sufficiently high reception intensity in practical use. At that time, by determining the ultrasonic transmission angle of the ultrasonic transmission device, it is possible to correctly adjust and measure the propagation path from the ultrasonic transmission device to the ultrasonic reception device. Measurement accuracy is improved.

Preferably, the ultrasonic transmission device and the ultrasonic receiving device, are arranged so as positioned in the radial direction and the oblique direction across the circulation circuit together, the radial direction of the circulation circuit, the circulation in a direction transverse to the circuit diagonally are configured to transmit and receive ultrasonic waves, when the ultrasonic propagation path of the previous SL ultrasonic transmitting device reaches to the ultrasonic receiver across the circulation circuit diagonally, the traveling path of ultrasonic waves, to pass through the tubing of the circulation circuit, further passes through the contents of the circulation circuit, wherein due to the refractive index change when passing through a different medium to pass through the tubing of the circulation circuit again The transmission angle of the ultrasonic transmission device is determined so as to appropriately adjust the refraction angle.

According to the above configuration, by transmitting ultrasonic waves in the radial direction of the circulation circuit, the transmission time to obtain a reflected wave reflected by the boundary between the blood flowing in the circulation circuit is measured, also transmitted wave diameter The time to reach a sensor arranged in the direction can be measured. Based on these time data, the tube thickness which comprises a circulation circuit can be calculated | required. The speed of sound when the tube is transmitted can be obtained based on the tube thickness and the time until the reflected wave returns. Furthermore, the temperature information and hematocrit value of the blood flowing through the circulation circuit can be measured to estimate the sound velocity in the blood. As a result, it is possible to adapt to the tube used at that time and always obtain the optimum ultrasonic wave emission angle under ambient temperature conditions.

Preferably, characterized by determining the transmission angle of the ultrasonic transmission device to pass in distance intermediate position of the ultrasonic path of travel is the paired said ultrasonic Namioku communication apparatus and the ultrasonic receiving device And
According to the above arrangement, when determining the ultrasonic path so as to pass through the intermediate position of the distance paired the ultrasonic Namioku communication apparatus and the ultrasonic receiving apparatus can obtain the correct flow rate.

Further, the present invention is arranged in the circulation circuit of an extracorporeal circulation device that circulates the blood of a patient outside the patient's body using a pump arranged in a circulation circuit formed by an elastic tube. A flow rate sensor that obtains a measured flow rate value of the blood passing therethrough using an ultrasonic signal, an ultrasonic transmission device provided such that the flow rate sensor is opposed at a position displaced with respect to the circulation circuit, and the ultrasonic transmission An ultrasonic receiving device that receives ultrasonic waves transmitted from the device, and determines a sound velocity of the ultrasonic waves in the blood based on a temperature and a hematocrit value of blood that is blood flowing through the circulation circuit. Based on one sound speed specifying step, the time from when the ultrasonic transmission device transmits the ultrasonic wave to when the ultrasonic reception device receives the ultrasonic wave, and the velocity of the ultrasonic wave in the blood. Based on the second sound velocity specifying step for obtaining the ultrasonic wave of the ultrasonic wave in the tube, the ultrasonic wave velocity of the ultrasonic wave in the blood and the ultrasonic wave of the ultrasonic wave in the elastic tube, according to Snell's law, the elastic tube and the blood A refractive index specifying step of obtaining a refractive index of the medium on which the ultrasonic wave travels at a boundary between the ultrasonic wave and obtaining an angle at which the ultrasonic wave should be transmitted based on the refractive index obtained by the refractive index specifying step Thus, the flow rate measurement method determines an ultrasonic transmission angle by the ultrasonic transmission device at the angle .
According to the above configuration, in the first sound speed specifying step, the sound speed of the ultrasonic wave in the blood is obtained based on the temperature and hematocrit value of the blood flowing through the circulation circuit. Further, in the second sound velocity identification step, the time in the elastic tube is determined based on the time from when the ultrasonic transmission device transmits the ultrasonic wave until the ultrasonic reception device receives the ultrasonic wave and the sound velocity of the ultrasonic wave in the blood. Find the ultrasonic wave. Further, in the refractive index specifying step, the refraction of the medium in which the ultrasonic wave travels at the boundary between the elastic tube and the blood is determined according to Snell's law based on the speed of the ultrasonic wave in the blood and the ultrasonic wave in the elastic tube. Find the rate. Thus, by changing the angle of the ultrasonic wave transmitted from the ultrasonic transmission device, the ultrasonic wave propagates through the circulation circuit through an appropriate path, and the correct flow velocity can be obtained.

Preferably, the ultrasonic transmitting device and the ultrasonic receiving apparatus, the flow rate sensor so is arranged to be positioned in the radial direction and the diagonal direction across said circulation circuit, and a radial direction of the circulation circuit, wherein This is a flow rate measuring method in which the ultrasonic waves are transmitted and received in a direction obliquely across the circulation circuit.
According to the above configuration, for the reason already described, it is possible to adapt to the tube used at that time and always obtain the optimum flow velocity under ambient temperature conditions .

In addition, the present invention provides an ultrasonic transmission device that is disposed in a circulation circuit formed by an elastic tube through which blood flows, and is disposed so as to be opposed to each other at a position shifted with respect to the circulation circuit, and the ultrasonic transmission An ultrasonic receiving device that receives ultrasonic waves transmitted from the device, an angle changing device that changes the ultrasonic transmission angle of the ultrasonic transmitting device, and at least the ultrasonic transmitting device and the ultrasonic receiving device are connected A control unit configured to calculate an ultrasonic wave propagation speed of the blood based on the blood temperature and the hematocrit value of the blood, and the ultrasonic transmitter transmits the ultrasonic wave. The ultrasonic wave propagation speed of the elastic tube is calculated based on the time from transmission until the ultrasonic wave reception device receives the ultrasonic wave and the ultrasonic wave propagation speed of the blood, and the ultrasonic wave of the blood A refraction angle at the boundary between the elastic tube and the blood is calculated based on the carrying speed and the ultrasonic wave propagation speed of the elastic tube, and the ultrasonic wave from the ultrasonic transmission device is calculated based on the refraction angle. the measured flow rate value of the transmission angle adjusted by the angle changing device the blood is the flow rate sensor that be measured accurately.

  In the present invention, when blood circulation is performed by operating a pump, the blood flow rate value can be accurately adjusted by adapting to the changes in blood characteristics of the patient, which changes every moment, and adapting to the tube used at that time. It is possible to provide a flow sensor that can measure the flow rate, an extracorporeal circulation device using the flow sensor, and a control method thereof.

The systematic diagram which shows embodiment of the extracorporeal circulation apparatus of this invention. Schematic which shows the structural example of a flow sensor. Schematic which shows the structural example of a flow sensor. The flowchart which shows the method of calculating the ultrasonic wave propagation velocity of blood. The flowchart which shows the method of calculating the ultrasonic propagation velocity of tube material. The flowchart which shows the method of determining the transmission angle of an ultrasonic wave. Schematic which shows the structural example of a flow sensor. The graph which shows a mode that an ultrasonic reception sensitivity changes according to the transmission angle of an ultrasonic wave. The flowchart which shows the method of determining the transmission angle of an ultrasonic wave. The conceptual diagram which shows another example of the mechanism which changes an ultrasonic transmission angle. The conceptual diagram which shows another example of the mechanism which changes an ultrasonic transmission angle.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
The embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.
FIG. 1 is a system diagram showing a preferred embodiment of the extracorporeal circulation apparatus of the present invention.
“Extracorporeal circulation” performed by the extracorporeal circulation apparatus 1 shown in FIG. 1 includes “extracorporeal circulation operation” and “auxiliary circulation operation”. The extracorporeal circulation device 1 can perform both “extracorporeal circulation operation” and “auxiliary circulation operation”.

  The “extracorporeal circulation operation” means, for example, when the blood circulation in the heart is temporarily stopped by cardiac surgery, the extracorporeal circulation device 1 performs the blood circulation operation and the gas exchange operation (oxygenation and / or oxygen) for the blood. Or carbon dioxide removal). “Auxiliary circulation operation” means that blood from the extracorporeal circulation device 1 is also used when the heart of the patient P to which the extracorporeal circulation device 1 is applied cannot perform a sufficient function or when the gas exchange by the lung cannot be performed sufficiently. And the gas exchange operation for this blood.

For example, when performing cardiac surgery on a patient, the extracorporeal circulation device 1 shown in FIG. 1 operates the pump of the extracorporeal circulation device 1 to remove blood from the patient's vein (vena cava), and then introduces blood into the blood using an artificial lung. After exchanging the gas and oxygenating the blood, extracorporeal blood circulation can be performed to return the blood to the patient's artery (aorta) again. The extracorporeal circulation device 1 is a device that performs substitution of the heart and lungs.
The extracorporeal circulation device 1 shown in FIG. 1 has a circulation circuit 1R that circulates blood. The circulation circuit 1R includes an artificial lung 2, a centrifugal pump 3, a drive motor 4 that is a drive means, a venous catheter (blood removal side catheter) 5, an artery side catheter (blood supply side catheter) 6, and a control unit. As a controller 10.

  As shown in FIG. 1, a venous catheter (blood removal side catheter) 5 is inserted from the femoral vein, and the distal end of the venous side catheter 5 is placed in the right atrium. The artery side catheter (blood feeding side catheter) 6 is inserted from the femoral vein. The venous catheter 5 is connected to the centrifugal pump 3 using a blood removal tube 11. A blood removal tube (also referred to as a blood removal line) 11 is a conduit for sending blood. When the drive motor 4 operates the centrifugal pump 3 according to the command SG of the controller 10, the centrifugal pump 3 removes blood from the blood removal tube 11 and passes it through the oxygenator 2, and then the blood supply tube 12 (also referred to as blood supply line). The blood can be returned to the patient P via. The blood removal tube 11 is provided with a flow rate measuring device 20 for measuring blood flow rate, for example, adjacent to the centrifugal pump 3. The flow rate measuring device 20 has a flow rate sensor that will be described in detail later.

  The artificial lung 2 is disposed between the centrifugal pump 3 and the blood supply tube 12. The oxygenator 2 performs a gas exchange operation (oxygen addition and / or carbon dioxide removal) on the blood. The oxygenator 2 is, for example, a membrane oxygenator, and a hollow fiber membrane oxygenator is particularly preferably used. Oxygen gas is supplied from the oxygen gas supply unit 13 to the artificial lung 2 through the tube 14. The blood supply tube 12 is a conduit connecting the artificial lung 2 and the artery side catheter 6. As the blood removal tube 11 and the blood supply tube 12, for example, a highly transparent and flexible synthetic resin conduit such as vinyl chloride resin or silicone rubber can be used. In the blood removal tube 11, blood flows in the V direction, and in the blood supply tube 12, blood flows in the W direction.

Next, the hematological parameter monitor measurement cell (hereinafter referred to as monitor measurement cell) 70 for extracorporeal circulation will be described.
The monitor measurement cell 70 shown in FIG. 1 is detachably disposed outside the blood removal tube 11 in the middle of the blood removal tube 11. The monitor measurement cell 70 is a disposable part and is disposed in the middle of the blood removal tube 11. The monitor measurement cell 70 is a sensor unit that can optically measure the values of oxygen saturation (%), hematocrit value (%), and hemoglobin (g / dL) in a non-contact manner with respect to the blood BD. .

  That is, the monitor measurement cell 70 can measure the hematocrit value for the blood in the blood removal tube 11 that has been removed from the subject. The monitor measurement cell 70 can obtain a corrected blood flow value in response to a change in blood characteristics (density) of the patient that changes from moment to moment.

  A structural example of the monitor measurement cell 70 shown in FIG. 1 will be described. The monitor measurement cell 70 includes an optical probe 69, and the optical probe 69 includes a light emitting unit 71, a light receiving unit 72, and a microcomputer 73. For example, the light emitting unit 71 is a light emitting diode, and the light receiving unit 72 is a photodiode. The light emitting unit 71 applies light to the blood BD passing through the blood removal tube 11, and the light receiving unit 72 detects reflection of light passing through a part of the blood BD, and this detection signal is sent to the microcomputer 73 shown in FIG. send. The light pulse emitted from the light emitting unit 71 directly hits the blood BD and is reflected with a reflection intensity corresponding to the oxygen saturation amount of hemoglobin in the blood BD.

The microcomputer 73 shown in FIG. 1 analyzes the values of oxygen saturation (%), hematocrit value (%), and hemoglobin (g / dL) from this reflection intensity, and thereby calculates oxygen saturation (%) and hematocrit value. Get (%).
These numerical values SW can be displayed on a monitor device 75 such as a liquid crystal monitor shown in FIG. This hematocrit value Ht (%) is a numerical value indicating the volume ratio of blood cells in the blood.
The monitor device 75 and the monitor measurement cell 70 shown in FIG. 1 constitute a blood gas analyzer 76 for extracorporeal circulation. The numerical values SW of oxygen saturation (%), hematocrit value (%), and hemoglobin (g / dL) are sent to the controller 100 of the controller 10 through the monitor device 76.
Here, the monitor measurement cell 70 measures the hematocrit value with the reflection intensity corresponding to the oxygen saturation amount of hemoglobin, but is not limited to such a method. For example, the hematocrit value may be measured from the transmitted light intensity or absorbance corresponding to the oxygen saturation amount of hemoglobin. In this case, the monitor measurement cell has a structure in which the blood removal tube 11 is sandwiched between the light emitting unit and the light receiving unit (not shown).
The monitor measurement cell is provided with a temperature sensor 17 for detecting the temperature of blood flowing through the circulation circuit 1R.

  By the way, when the flow measuring device 20 shown in FIG. 1 is used as a blood flow meter of the ultrasonic propagation time difference method as described above, if the characteristic (density) of the blood BD passing through the blood removal tube 11 changes, the blood A measurement error occurs in the measured flow rate value. In the extracorporeal circulation apparatus 1, when measuring the flow rate of the blood BD in the blood removal tube 11, the density of the blood BD differs depending on the patient. In addition, for example, when blood is mixed with physiological saline during extracorporeal blood circulation surgery, the blood BD to be circulated becomes thin, and during the extracorporeal blood circulation surgery, the density of the patient's blood varies from moment to moment.

  Since the density (characteristic) of the blood BD changes every moment in this way, if the hematocrit value of the blood BD flowing through the blood removal tube 11 is large (when the blood density is high), the ultrasonic wave The time difference in which the blood propagates in the forward and backward directions is reduced, and the blood flow value measured by the flow measuring device 20 becomes smaller than the actual blood flow value. Conversely, when the hematocrit value of the blood BD flowing in the blood removal tube 11 is small (when the density of the blood is low), the time difference for propagating the blood in the forward and backward ultrasonic waves becomes large and is measured by the flow measuring device 20. The blood flow value becomes larger than the actual blood flow value.

  There is a correlation between the density of blood BD and the above-described hematocrit value of blood BD. For this reason, in the extracorporeal circulation apparatus 1 of the embodiment, the monitor measurement cell 70 of the blood gas analyzer 76 for extracorporeal circulation shown in FIG. 1 constantly measures the hematocrit value of the blood BD flowing in the blood removal tube 11. . The measurement result of the hematocrit value is constantly fed back from the microcomputer 73 to the control unit 100 through the monitor device 75. It has already been found that the hematocrit value Ht of the blood BD flowing in the blood removal tube 11 changes greatly, for example, before extracorporeal circulation, after 5 min. And the control part 100 correct | amends the measured flow value (discharge flow value) of the blood BD which flows through the blood removal tube 11 measured by the flow measuring device 20 by the system demonstrated later, and correct | amends the corrected flow value. To get.

Here, the flow rate of fluid such as blood, environmental changes, and changes in the intensity of ultrasonic waves will be briefly described with an example. The reference flow rate of the motor is 4 liters / minute.
When the environmental temperature is 40 ° C. and the fluid is 5% saline, the ultrasonic intensity in the flow rate sensor, which will be described later, is 227, and the flow rate value is 3601 (“milliliter / minute”, hereinafter the flow rate value is the same).
On the other hand, when the environmental temperature is 15 ° C. and the fluid is water, the ultrasonic intensity in the flow rate sensor described later is 246 and the flow rate value 4148.

That is, when the discharge flow rate value of the blood BD flowing in the blood removal tube 11 shown in FIG. 1 is measured by the flow rate measuring device 20, the measured flow rate value of the blood BD is obtained. Then, the corrected flow rate value Flow_C shown below is obtained by correcting with the hematocrit value Ht constantly measured by the monitor measurement cell 70.
The corrected flow value Flow_C can be obtained by the following conversion formula. This conversion formula is obtained for each different temperature. This conversion equation can obtain a blood flow value corrected from the relationship between the measured flow value of blood and the hematocrit value.

Flow_C = Flow_M * (1+ (Ht_B-Ht_M) * A)) ... Conversion formula

In the above equation, corrected flow rate value: Flow_C, measured flow rate value: Flow_M, measured hematocrit value: Ht_M, reference hematocrit value: Ht_B, slope: A (rate of change).
The control unit 100 shown in FIG. 1 stores a conversion formula for each blood temperature.

  In the extracorporeal circulation device 1 according to the first embodiment of the present invention shown in FIG. 1, the control unit 100 of the controller 10 stores in advance a plurality of conversion formulas corresponding to a plurality of blood temperatures. For example, as described above, the minimum temperature assumed when the liquid temperature is actually operated is 15 ° C., the maximum temperature assumed is 40 ° C., and the interval is set at an arbitrary temperature interval. A plurality of conversion formulas are stored.

For example, when performing cardiac surgery on a patient using the circulation circuit 1R of the extracorporeal circulation apparatus 1 shown in FIG. 1, when the drive motor 4 operates the centrifugal pump 3 according to the command SG of the controller 10, the centrifugal pump 3 After blood is removed from the blood removal tube 11 and passed through the artificial lung 2 to exchange blood gas and oxygenate the blood, the blood is passed to the patient P via the blood supply tube 12 (also referred to as blood supply line). To return.
At this time, the hematocrit value Ht of the blood BD flowing in the blood removal tube 11 changes greatly, for example, before extracorporeal circulation, after 5 min. May become smaller.

  Therefore, the monitor measurement cell 70 of the blood gas analyzer 76 for extracorporeal circulation shown in FIG. 1 constantly measures and updates the hematocrit value, and the monitor device 75 of the blood gas analyzer 76 for extracorporeal circulation uses the measured value as a measured value. The updated new hematocrit value is fed back to the control unit 100. Then, the control unit 100 corresponds to the temperature of the blood BD flowing in the blood removal tube 11 from the plurality of conversion formulas for each temperature from the measurement result of the hematocrit value and the temperature of the blood BD at that time. Select the temperature conversion formula to calculate. Thereby, the control unit 100 always corrects the measured flow value (discharge flow value) of the blood BD flowing through the blood removal tube 11 measured by the flow measuring device 20, and obtains the corrected blood flow value. be able to.

However, even if such calibration is performed, if the parameters in the calibration are deviated, an ultrasonic receiving device that should receive ultrasonic waves from the ultrasonic transmitting device when an ultrasonic propagation path described later shifts. If it deviates from the position, the flow rate cannot be measured or the correct flow rate cannot be obtained.
Therefore, in this embodiment, the above-described calibration is performed, and in addition to this, the method described below is performed.

  An ultrasonic transmission device provided so as to face each other at a position shifted with respect to the circulation circuit 1R in FIG. 1, an ultrasonic reception device that receives ultrasonic waves transmitted from the ultrasonic transmission device (described later), and ultrasonic transmission An angle changing device that changes the ultrasonic transmission angle of the device, and a control unit 100 to which the ultrasonic transmission device and the ultrasonic reception device are connected, and adjusts the ultrasonic transmission angle from the ultrasonic transmission device By doing so, the structure which measures the measured flow value of the said blood accurately is employ | adopted.

(First embodiment)
Next, the structure of the flow sensor used in the first embodiment for realizing such a method will be described, and a control method for flow measurement will be described.
FIG. 2 is a cross-sectional view showing a schematic configuration of the flow sensor 30.
The flow sensor 30 is provided in the flow measurement device 20, and each component is connected to the control unit 10 of the controller 100.

As already described, for the circulation circuit 1R, a highly transparent and flexible synthetic resin conduit such as vinyl chloride resin or silicone rubber is selected. In this case, since the tube is selected each time, its ultrasonic transmission characteristics and particularly the tube thickness M1 are different.
Outside the circulation circuit 1R, ultrasonic elements 32, 33, 34, and 35 as ultrasonic transmission / reception devices are arranged. The ultrasonic elements 32 and 34 are opposed to each other with the tube interposed therebetween, and the ultrasonic elements 33 and 35 that are opposed to each other as another pair are disposed at positions shifted with respect to the circulation circuit 1R. These are all the same structure.

Therefore, the ultrasonic element 32 will be described as a representative.
The ultrasonic element 32 is preferably a piezoelectric vibrator. Actually, a small dot-shaped element is practical, not a large planar head part as shown in the figure, but for convenience of understanding. It is described in the trapezoid. An acoustic lens 32a made of an elastic body or the like is preferably disposed at the front end of the head portion that receives and transmits ultrasonic waves, so that the ultrasonic waves to be transmitted can be focused along the propagation path and directed to the propagation path. It has become possible to give sex.
The piezoelectric vibrator constituting the ultrasonic element 32 is excited at a constant frequency, for example, 1.8 MHz (megahertz) by being supplied with a drive voltage by the control unit 10 via the controller 10, and an ultrasonic wave corresponding to this is excited. Can be sent. The frequency may be changed as appropriate by selecting an element made of a piezoelectric material of a type suitable for the structure and material of the circulation circuit 1R.

In addition to transmitting ultrasonic waves, the ultrasonic element 32 is excited by the received ultrasonic waves and converted into an electric signal to generate a reception signal.
In this embodiment, some or all of the ultrasonic elements are provided with the angle changing mechanism 36.
In the case of FIG. 2, the angle changing mechanism 36 is attached to all the ultrasonic elements. However, in order to exert the operation of this embodiment, at least a pair of the ultrasonic elements in an oblique direction, that is, an ultrasonic wave The elements 32 and 35 are provided with an angle changing mechanism 36 for rotating in the direction of the arrow P, so that the direction of the ultrasonic wave to be transmitted can be changed. The angle changing mechanism 36 has a motor that can rotate forward and backward so as to be able to rotate in the P direction. In addition, a motor control unit (not shown) that controls the rotation of the motor is configured in the flow rate measuring device 20 and may be electrically connected to the control unit 10 of the controller 100, or may be communicable wirelessly. Absent. The controller 10 of the controller 100 may directly control the motor. That is, the control unit 10 has a function of a motor control unit. In this case, the motor control unit is not configured in the flow rate measuring device 20.

  Further, it is preferable that the ultrasonic elements 32 and 35 having diagonal directions are rotated in synchronism so that the transmission angle and the reception angle of the ultrasonic wave coincide with each other.

The flow sensor 30 is configured as described above. Next, an example of a flow measurement method using the flow sensor 30 of FIG. 2 will be described.
In this case, even if an ultrasonic wave is transmitted from one of the paired ultrasonic elements to the other ultrasonic element and received, the tube itself and the blood flowing through the tube are different, and the physical properties are different. The ultrasonic path is refracted at these boundaries.
Considering this, unless a transmission angle of an ultrasonic element that transmits ultrasonic waves is appropriately determined, a propagation path that is correctly received by the other ultrasonic element cannot be determined.
Therefore, the transmission angle is determined as follows.

Together with FIG. 3, reference is made to the flowcharts of FIGS.
FIG. 4 relates to a method for obtaining the ultrasonic wave propagation velocity corresponding to the blood flowing through the circulation circuit R1, and FIG. 5 relates to a method for obtaining the ultrasonic wave propagation velocity of the tubes constituting the circulation circuit 1R. These are performed separately, and there is no rule before and after the execution of each process. However, the ultrasonic transmission angle shown in FIG. 6 is determined based on the results of the steps shown in FIGS.

  In FIG. 4, first, a blood temperature measurement value is obtained from the temperature sensor 17 of FIG. 1 (ST1). Next, the hematocrit value Ht is acquired by the monitor measurement cell 70 (ST2). At this time, the ultrasonic propagation velocity V2 of blood (*) is obtained by the conversion formula described above. This is the propagation speed of each M2 portion of the diameter M of the circulation circuit R1 in FIG.

  Instead of the conversion formula, the ultrasonic wave propagation velocity V2 may be obtained using table data prepared in advance based on conditions such as temperature and hematocrit value Ht.

Reference is now made to FIG.
The propagation time of the ultrasonic wave (reflected wave) by the flow sensor 30 is measured (ST11).
This is according to the following procedure.
In FIG. 2, it is necessary to know the tube thickness M1 in order to accurately know the propagation speed of the ultrasonic wave propagating through the tube. The tube is taken into consideration when it is used after being replaced.
First, an ultrasonic wave is transmitted vertically downward from the ultrasonic element 32 and is received by the ultrasonic element 34 through a path P1. The received ultrasonic wave is reflected vertically upward by the ultrasonic element 34 as a reflected wave, and is received by the ultrasonic element 32 through the path P2. The time during this period is measured by the timer 17 in FIG.

2 and 5, the time measured by the timer 17 is S, and the time required for the ultrasonic wave to pass through the tube thickness distance M1 is S1. The time S2 required for the ultrasonic wave to pass through the blood (pass through the inner diameter of the tube) is obtained immediately since the speed at which the ultrasonic wave propagates through M2 is known as V.
That is, the time S2 = S−S1 required to pass this blood.
The tube inner diameter M2 = V × S2.
From these relationships, when the tube thickness M1 is obtained,
M1 = (M−M2) / 2
It is.
Next, S1 = (S−S2) / 2, and the ultrasonic wave propagation velocity V2 of the tube is calculated by M1 / S1 (ST12).

Reference is now made to FIGS.
When the ultrasonic element 32 is rotated in the P1 direction (simultaneously rotating the ultrasonic element 35 in the P2 direction by the same amount), the rotation angle is obtained by rotating the virtual perpendicular Z by θ1.
Snell's law is sinθ1 / sinθ2 = V2 / V
Therefore, θ1 and θ2 are obtained from right-angled triangles formed by the oblique inclined line L1 and the virtual perpendicular line Z without the inside of the tube and the tube thickness. (ST21).
Therefore, in FIG. 3, by rotating the ultrasonic element 32 by θ1 with respect to the virtual perpendicular Z in the P1 direction, the ultrasonic wave propagation path L1 passes through the midpoint between the ultrasonic elements 32 and 35, and the ultrasonic element 35 Are received without any positional deviation (ST22).
For convenience of understanding, in FIG. 3, the head portions of the rotated ultrasonic elements 32 and 35 are separated from the tube, but as described above, the biasing means 32b causes the head portions to be related to the rotation position. The head portion of the ultrasonic element is in close contact with the tube.

As described above, according to the present embodiment, when blood circulation is performed by operating the pump, it is possible to adapt to the change in blood characteristics of the patient that changes from moment to moment, and to the tube used at that time. The blood flow rate can be accurately measured.
In addition, when taking the above method, the ultrasonic element 33 can be omitted.
Further, the above results may be performed using the ultrasonic elements 33, 34, and 35, and the results of both may be averaged for fine correction.

  Note that the above explanation is a method in the case where the flow velocity change at the radial position in the tube is not considered on the assumption that the blood flow velocity in the tube is uniform. Therefore, for more accuracy, for example, when passing blood, considering the Hagen-Poiseuille flow at the time of viscous blood, the flow is fast near the center of the pipeline, and the flow velocity becomes slower as it approaches the tube wall In view of this, when the flow velocity distribution according to the position in the tube is calculated in advance and the ultrasonic transmission angle is corrected based on the calculation result, more accurate measurement is possible.

(Second Embodiment)
FIG. 7 shows a second embodiment of the ultrasonic element. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. Hereinafter, differences will be mainly described.
FIG. 8 is a graph in which the ultrasonic reception sensitivity is measured, and FIG. 9 is a flowchart showing a measurement method according to the second embodiment.

In FIG. 7, in this flow sensor 41, if there is only a pair of ultrasonic elements 32 and 35 that sandwich the tube in a diagonal direction, the transmission angle of the ultrasonic wave can be determined.
First, an ultrasonic wave is transmitted from the ultrasonic element 32. In this state, the ultrasonic element 32 is rotated in the direction of arrow P1 by the rotation mechanism 36 (ST21). At this time, the ultrasonic element 35 is also rotated in the P2 direction in synchronization.
During this operation, the control unit 100 monitors the ultrasonic reception state of the ultrasonic element 35.

In FIG. 9, as shown in the graph, the reception sensitivity of the ultrasonic element 35 gradually increases as indicated by K1, becomes highest at the point of KP, and then decreases as indicated by K2. To go.
Accordingly, with reference to the graph of FIG. 9, for example, the control unit differentiates the value, stops the rotation of the ultrasonic element 32 at the moment when it reaches the vertex KP or the differential value turns negative, and obtains the angle θ1. In the case of FIG. 8, the case where θ1 is 45 degrees is exemplified, but the angle is not limited to 45.
When the ultrasonic element 32 transmits an ultrasonic wave at an angle θ, the ultrasonic wave propagation path is L2, and the ultrasonic element 32 is accurately received without being displaced in synchronization with the ultrasonic element 35 opposed thereto.
Rather, it is important to find the location of KP in FIG. 9, and the ultrasonic transmission angle θ1 is determined at this location.
The present embodiment is configured as described above, can exhibit the same functions and effects as those of the first embodiment, and can obtain the functions and effects by a simpler technique.

(Modification)
FIG. 10 and FIG. 11 are mainly modifications of the second embodiment, and show another configuration of the ultrasonic element 32.
In this case, this is a configuration example in which an ultrasonic wave can be “transmitted” at a specific angle without rotating the ultrasonic element itself.
As shown in FIG. 11, the ultrasonic element includes a plurality of elements constituted by small piezoelectric oscillators or the like along the length direction of the tube, such as 32-1, 32-2, 32-3. Arrange many. It is important that these ultrasonic elements transmit the ultrasonic waves to be transmitted in a diffused state without focusing.

As shown in FIG. 10, the drive voltages are applied to the respective ultrasonic elements 32-1, 32-2, 32-3,. It has become.
Thus, the ultrasonic waves are transmitted as a diffused beam in order from the left in FIG. 11, and the position where the front surface of the ultrasonic wave arrives is faster in the left and delayed as it goes to the right. As it goes, the fracture surface of the leading edge of the ultrasonic wave from each ultrasonic element becomes slower and smaller.
Thereby, as a whole, the location where the intensity of the ultrasonic wave is high advances along the angle θ5 with respect to the virtual perpendicular Z.

  Using this mechanism, the intervals of the driving voltage peaks applied to the ultrasonic elements 32-1, 32-2, 32-3,... Shown in FIG. By making it faster, the angle θ can be swung, and an ultrasonic wave having a peak KP can be transmitted by changing the timing of applying the drive voltage while viewing FIG.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the claims.
A part of each configuration of the above embodiment can be omitted, or can be arbitrarily combined so as to be different from the above.

  DESCRIPTION OF SYMBOLS 1 ... Extracorporeal circulation apparatus, 1R ... Circulation circuit, 2 ... Artificial lung, 3 ... Centrifugal pump, 4 ... Drive motor, 5 ... Vein side catheter (blood removal side catheter), 6 ... Arterial side catheter (blood feeding side catheter), 10 ... Controller as control unit, 20 ... Flow rate measuring device, 30, 31 ... Flow rate sensor, 32, 33, 34, 35 ...・ Ultrasonic element

Claims (7)

An extracorporeal circulation device for circulating a patient's blood outside the patient's body using a pump arranged in a circulation circuit,
A flow rate sensor disposed in the circulation circuit formed by an elastic tube to obtain a measured flow value of the blood passing through the circulation circuit using an ultrasonic signal ;
A temperature sensor for obtaining the ambient temperature;
A measuring unit disposed in the circulation circuit for measuring a hematocrit value of the blood passing through the circulation circuit;
A timer for measuring time relating to transmission and reception of the ultrasonic wave;
With
An ultrasonic transmitter provided inside the flow rate sensor so as to face each other at a position displaced with respect to the circulation circuit, and an ultrasonic receiver that receives ultrasonic waves transmitted from the ultrasonic transmitter;
An angle changing device for changing a transmission angle of the ultrasonic wave of the ultrasonic transmission device;
A control unit to which the ultrasonic transmission device and the ultrasonic reception device are connected;
The control unit calculates an ultrasonic wave propagation velocity of the blood based on the blood temperature measurement value measured by the temperature sensor and the hematocrit value measured by the measurement unit, and is measured by the timer And the ultrasonic wave of the elastic tube based on the time from when the ultrasonic wave transmission device transmits the ultrasonic wave to when the ultrasonic wave reception device receives the ultrasonic wave and the ultrasonic wave propagation velocity of the blood. Calculate a propagation speed, calculate a refraction angle at the boundary between the elastic tube and the blood based on the ultrasonic propagation speed of the blood and the ultrasonic propagation speed of the elastic tube, and based on the refraction angle extracorporeal循characterized in that a configuration in which the measurement accurately measured flow rate value of the adjusted the blood by the angle changing device transmission angle of the ultrasonic wave from the ultrasonic transmitting device Ring device. Wherein in response to the transmission angle of the ultrasonic waves have a device for measuring the ultrasonic wave reception intensity at the ultra sound Nami受 communication apparatus, and ultrasonic reception intensity is given to the control unit, the most by the control unit The extracorporeal circulation device according to claim 1, wherein the transmission angle of the ultrasonic wave is determined at a location where reception intensity is strong. The ultrasonic transmitting device and the ultrasonic receiving device, arranged to be positioned in the radial direction and the oblique direction across the circulation circuit together, the radial direction of the circulation circuit, across the circulation circuit obliquely It is configured to transmit and receive ultrasound in the direction ,
When ultrasound traveling path of the previous SL ultrasonic transmitting device reaches to the ultrasonic receiver across the circulation circuit obliquely traveling path of ultrasonic is passed through the tubing of the circulation circuit, further wherein passing the contents of the circulation circuit, to properly adjust the angle of refraction due to the refractive index change when passing through a different medium to pass through the tubing of the circulation circuit again, the transmission angle of the ultrasonic transmitting device The extracorporeal circulation device according to claim 1, wherein the extracorporeal circulation device is determined. Claims, characterized in that determining the transmission angle of the ultrasonic transmission device to pass in distance intermediate position of the ultrasonic path of travel is the paired said ultrasonic Namioku communication apparatus and the ultrasonic receiving device Item 4. The extracorporeal circulation apparatus according to Item 3. Using the pump arranged in the circulation circuit formed by the elastic tube, the measured flow rate of the blood passing through the circulation circuit arranged in the circulation circuit of the extracorporeal circulation device for circulating the patient's blood outside the patient's body A flow sensor that obtains a value using an ultrasonic signal ;
An ultrasonic transmission device provided so that the flow rate sensor is opposed to the position where the flow sensor is displaced across the circulation circuit, and an ultrasonic reception device that receives ultrasonic waves transmitted from the ultrasonic transmission device;
With
A first sound velocity specifying step for obtaining a sound velocity of an ultrasonic wave in the blood based on a temperature and a hematocrit value of blood that is blood flowing through the circulation circuit;
Based on the time from when the ultrasonic transmission device transmits the ultrasonic wave until the ultrasonic reception device receives the ultrasonic wave and the speed of sound of the ultrasonic wave in the blood, the ultrasonic wave in the elastic tube A second sound speed specifying step for obtaining a sound wave;
Based on the sound velocity of the ultrasonic wave in the blood and the sound wave of the ultrasonic wave in the elastic tube, the refractive index of the medium in which the ultrasonic wave travels at the boundary between the elastic tube and the blood is obtained by Snell's law. Refractive index identification step;
Have
A flow rate characterized by obtaining an angle at which the ultrasonic wave is to be transmitted based on the refractive index obtained by the refractive index specifying step, and determining an ultrasonic transmission angle by the ultrasonic transmission device at the angle. Measuring method. Said ultrasonic transmitting device and the ultrasonic receiving device, arranged to as the flow rate sensor is positioned in the radial direction and the diagonal direction across said circulation circuit, and a radial direction of the circulation circuit, said circulation circuit in a direction transverse to the diagonal, the flow rate measuring method according to claim 5, characterized in that causing sending and receiving the ultrasonic waves. It is placed in a circulation circuit formed by an elastic tube through which blood flows.
An ultrasonic transmitter provided so as to be opposed to each other at a position shifted with respect to the circulation circuit, and an ultrasonic receiver that receives an ultrasonic wave transmitted from the ultrasonic transmitter;
An angle changing device for changing a transmission angle of the ultrasonic wave of the ultrasonic transmission device;
A control unit to which at least the ultrasonic transmission device and the ultrasonic reception device are connected , and
The control unit calculates an ultrasonic propagation velocity of the blood based on the temperature of the blood and the hematocrit value of the blood, and the ultrasonic reception device transmits the ultrasonic wave after the ultrasonic transmission device transmits the ultrasonic wave. The ultrasonic propagation speed of the elastic tube is calculated based on the time until the apparatus receives the ultrasonic wave and the ultrasonic propagation speed of the blood, and the ultrasonic propagation speed of the blood and the elastic tube The refraction angle at the boundary between the elastic tube and the blood is calculated based on the ultrasonic propagation velocity, and the transmission angle of the ultrasonic wave from the ultrasonic transmission device is calculated by the angle changing device based on the refraction angle. adjusting the flow rate sensor, it characterized that you measure accurately measured flow rate value of the blood.

Images