JP2005065888A - Blood vessel access monitoring method and medical device - Google Patents

Abstract

To detect abnormalities in vascular access by extracting only the pressure waveform caused by the pulse from the blood or infusion pressure waveform existing outside the body with vascular access, from various pressure waveforms mixed It is extremely difficult to reliably extract only the pressure waveform resulting from the pulse.
By detecting the presence of a direct current component in a waveform obtained by multiplying a pressure waveform caused by an independently measured pulse and a pressure waveform of blood or infusion containing various pressure waveforms, Abnormalities in vascular access such as vascular cannula dropout can be reliably detected.
[Selection] Figure 2

Description

  The present invention relates to a method for monitoring vascular access to a patient in a medical device such as a dialysis device, a heart-lung machine, and an infusion pump, and a medical device to which the method is applied.

  As medical devices that move or circulate liquids through a blood vessel access to a patient's blood vessels, dialysis devices, cardiopulmonary devices, infusion pumps, and the like are known. For example, taking a dialysis machine as an example, the liquid that is connected to the patient's blood vessel via vascular access and moves to the blood vessel is blood. It is a system that removes the waste products and returns the filtered blood to the body to circulate the blood. In the case of an infusion pump, the liquid that is connected to the patient's blood vessel via the vascular access and moves to the blood vessel corresponds to a liquid medicine or nutrient solution, and the medicine or nutrient solution is transferred via the vascular access. The system is injected into the patient's body.

  Here, the dialysis apparatus will be described in detail. First, a blood vessel cannula (needle) is inserted into a blood vessel to realize blood vessel access, and the liquid derived from the patient's body by driving a blood pump via the blood vessel access, that is, blood passes through the dialyzer, The waste and water in the blood are removed and purified by the osmotic pressure difference between the dialysate flowing outside the hollow fiber and the blood flowing inside the hollow fiber and ultrafiltration. The dialysis treatment is generally performed over a long period of 4 to 5 hours, and during this treatment period, the dialysis patient spends sleeping, watching TV, or reading.

  However, there is a risk that a serious accident such as dropping of a blood vessel cannula (needle) due to tumbling during sleep may occur. For example, if the needle on the venous side is removed, blood may continue to flow out. On the other hand, if the needle on the arterial side is removed, there is a risk of air flowing into the blood vessel, which is a serious problem for patient safety. . For this reason, the arterial side detects air bubbles with a bubble detector, and measures are taken to detect the dropout of the arterial needle. In addition to detachment of the vascular cannula, problems such as poor dialysis blood circulation due to twisting of the vascular tube may occur.

  Thus, Patent Document 1 discloses a method for detecting needle dropout for dialysis. According to this method, the pressure wave generated by the heart is detected by the pressure sensor through the blood to be dialyzed, and if the pressure wave is not detected, the needle has fallen off. FIG. 5 shows an example of pressure waveforms observed by the arterial and venous pressure sensors. This pressure waveform includes not only the pressure waveform caused by the pulse, but also the pressure waveform caused by the blood pump, etc., or disturbance that occurs temporarily due to the patient turning over, etc. The problem is whether to select only the pressure waveform to be used.

  According to the method of Patent Document 1, since the frequency of the pressure waveform generated by the heart and the pressure waveform generated by the blood pump are different, a means for extracting only the pressure waveform caused by the heart using a bandpass filter or the like is employed. ing.

  Further, according to the method of Patent Document 2, when the valves in the dialysate supply pipe and the carry-out pipe of the dialyzer are switched, a negative pulse pressure is generated, and the pulse is measured by the pressure sensor. When the needle is inserted and removed, a characteristic change in the pressure waveform is used to detect the drop of the needle. However, it is difficult to reliably detect needle drop by capturing subtle changes in the pressure waveform.

  Further, according to the method of Patent Document 3, changes in the addition pressure and the differential pressure between the arterial pressure and the venous pressure observed by the dialyzer are input to a discriminant, and the output of the discriminant is compared with a threshold value. The needle drop is detected. However, with this method, the venous pressure measurement during dialysis is highly disturbed and easily causes false detection.

Japanese National Patent Publication No. 11-513270 JP 11-104233 A JP 2000-140101 A

  The above-described method is a method of monitoring the state of vascular access using a pressure waveform obtained by measuring the pressure applied to the fluid moving through the vascular access such as a dialysis machine. However, the pressure waveform observed in the liquid is a combination of the pressure waveforms of various factors and also includes disturbances, so it is extremely difficult to extract only the pressure waveform due to the pulse. It is difficult to monitor the state of reliable vascular access with many false detections.

  The present invention has been made under the circumstances as described above, and an object of the present invention is a pressure obtained by measuring the pressure of a liquid that moves through a vascular access and includes various pressure waves and disturbances. Method for determining whether or not there is a pressure waveform due to a pulse in the waveform, and reliably monitoring that an abnormality has occurred in the vascular access of the medical device due to the disappearance of the pressure waveform due to the pulse And a medical device using the method.

  The present invention relates to a blood vessel access monitoring method in a medical device that has a mechanical device that is coupled to a patient's blood vessel via vascular access and applies pressure to move fluid to the blood vessel. The purpose is to measure the pressure waveform of the pressure applied to the liquid and the pressure waveform resulting from the pulse of the patient, multiplying the pressure waveform of the liquid by the pressure waveform resulting from the pulse, and the result of the multiplication This is achieved by monitoring the abnormality in the vascular access by extracting the direct current component from the waveform and determining the level of the direct current component. The above-mentioned object of the present invention can be achieved more effectively by measuring the pressure waveform of the liquid at least one of an arterial liquid and a venous liquid.

  The present invention also relates to a medical device having a mechanical device that is coupled to a patient's blood vessel via vascular access and applies pressure to move fluid to the blood vessel. First pressure detecting means for measuring a pressure waveform of pressure applied to the liquid, second pressure detecting means for measuring a pressure waveform caused by the pulse of the patient, pressure waveform of the liquid and the pulse Multiplying means for multiplying the resulting pressure waveform, direct current component extracting means for extracting a direct current component from the multiplication result of the multiplying means, and determining means for measuring a level of the direct current component to determine abnormalities in blood vessel access This is achieved by providing a vascular access monitoring circuit. Further, the object of the present invention is to measure the pressure waveform of the pressure applied to the liquid by the first pressure detecting means by measuring at least one of the pressure of the artery side liquid or the vein side liquid. Achieved more effectively.

  According to the present invention, when a pressure waveform including waveforms of various factors obtained by measuring a pressure applied to a liquid moving via a vascular access is multiplied by a pressure waveform caused only by a pulse, the liquid A DC component is formed in the multiplied waveform only when there is a pressure waveform due to the pulse in the tube, so by detecting the disappearance of the DC component, abnormalities in vascular access such as vascular cannula dropout can be ensured. It is possible to provide a blood vessel access monitoring method that can be detected and a medical device to which the method is applied.

  First, the basic idea of the present invention will be described, and then specific examples will be described.

  When connected to a patient's blood vessel using a blood vessel cannula (needle) or the like, and the patient's blood vessel and the medical device are connected via a tube filled with liquid, the pressure wave resulting from the patient's pulse Propagate through. Therefore, when the pressure wave due to the pulse does not exist in the liquid, it is considered that the blood vessel access is abnormal such as the drop of the blood vessel cannula. As an example of the liquid, blood of a patient in a dialysis machine, or a drug or nutrient to be injected into a patient if an infusion pump is considered.

  However, in addition to the pressure wave due to the pulse, for example, in the dialysis machine, the pressure wave of the dialysate circulation pumps, the pressure wave affecting the liquid when the patient moves the body irregularly, etc. Because it is included, it is difficult to extract only the pressure wave caused by the pulse. Therefore, the present invention measures the pressure applied to the liquid instead of extracting the pressure waveform resulting from the pulse from the pressure waveforms obtained by measuring various pressures applied to the liquid. It is detected whether or not the pressure waveform resulting from the pulse exists in the obtained pressure waveform.

  In this method, a pressure waveform caused by a pulse is measured independently using a detection means such as a pulse sensor, and the pulse is included in various pressure waveforms contained in the liquid by referring to the pressure waveform. This is a method for detecting whether or not the resulting pressure waveform exists.

The theory of the detection method will be described below.
In general, a waveform can be expanded into a sine wave or a cosine wave as shown in Equation 1 by Fourier transform. The pressure waveform of the pressure applied to the liquid related to the vascular access and the pressure waveform caused by the pulse are a kind of waveform, and the waveform is also expressed by superposition of a sine wave and a cosine wave as shown in Equation 1. it can.

ここで、αはα＝ω_αｔ＝２πｆ_αｔを表わす。

Here, α represents α = ω _α t = 2πf _α t.

  Therefore, when the two waveforms are multiplied, a term (sin (α) · sin (β)) obtained by multiplying the sine wave and the sine wave as shown in Equation 2 is generated. And expand.

となる。ここで、βはβ＝ω_βｔ＝２πｆ_βｔを表わす。

It becomes. Here, β represents β = ω _β t = 2πf _β t.

Here, if α = β, cos (α−β) = 1, and cos (α−β) is a term that does not include α or β, that is, a direct current component that does not include f _α or f _β. .

Here, f _α is a frequency caused by the pulse detected by the pulse sensor. On the other hand, if f _β is a frequency component of a pressure wave contained in the liquid, f _β is a pressure wave frequency caused by a dialysis pump or the like, a pressure wave frequency caused by a patient turning over, or a pressure wave caused by a pulse. Various frequencies such as the frequency (f _α ) are included.

However, among the various frequency f _β of pressure waves contained in the liquid, the same frequency component (f _α = f _β , that is, α = the same as the frequency f _α caused by the pulse detected by the pulse sensor used as the reference frequency. The pressure wave with β) is only the frequency f _α due to the patient's pulse. That is, as a reference, the pressure waveform caused by the pulse detected by the pulse sensor is multiplied by the pressure waveform detected by the pressure sensor installed in the liquid, and the DC component is extracted from the multiplied value. It is only the multiplication result by the pressure waveform resulting from the pulse among the various pressure waveforms contained in the liquid. At a frequency not caused by a pulse, for example, a frequency caused by a dialysis pump or the like, the relationship of f _α = f _β , that is, α = β does not hold, and therefore has a frequency component instead of a direct current component in a polynomial obtained as a result of multiplication. It exists as a term.

  Therefore, as long as a direct current component exists in the polynomial obtained by multiplying the pressure wave detected by the pulse sensor and the pressure wave of the liquid, vascular access to the liquid is normal. This means that there is no abnormality in vascular access such as omission or twisting of the vascular tube. On the contrary, when the term which DC component has does not exist, it means that the pressure wave resulting from the pulse does not propagate to the liquid due to the drop of the blood vessel cannula or the like.

  Therefore, as a detection method, a low-pass filter for extracting a DC component from a waveform obtained by multiplying the pressure waveform caused by the pulse detected by the pulse sensor and the pressure waveform of the pressure applied to the liquid. And the like, and abnormalities in blood vessel access are detected based on the presence or absence of the DC component.

  An embodiment when applied to an actual apparatus based on this detection principle will be described below.

  First, an embodiment in which the present invention is applied to a dialysis apparatus that is an example of a medical apparatus will be described with reference to FIGS. 1 and 2. In the dialysis machine, the moving liquid corresponds to blood to be dialyzed by the patient.

  FIG. 1 shows an overall configuration diagram of the dialysis machine. In FIG. 1, the liquid moving through the vascular access is blood before dialysis containing waste or blood after dialysis. In such a dialysis device, the blood of the patient to be dialyzed is sent from the arterial cannula 1 inserted into the patient's artery side blood vessel to the dialyzer 6 via the blood tube 2 and the artery side drip chamber 4. In the dialyzer 6, waste or the like contained in the patient's blood is filtered, and the patient's blood from which the waste has been removed is sent to the venous drip chamber 8 and further through the venous blood tube 2 to the venous cannula 10. To the patient's blood vessels. This blood circulation is forcibly performed by the blood pump 3. The waste of blood is transferred to the dialysate by the dialyzer 6, and the dialysate containing the waste is transported through the dialysate tube 13.

  As the pressure applied to the blood circulating in the extracorporeal circulation blood circuit, the pressure by the blood pump 3 is the largest, and the pressure by the dialysate circulation pump (not shown) and the pressure by the patient's pulse are superimposed. Also included are temporary disturbances that occur when the patient rolls over. The arterial side pressure sensor 5 and the venous side pressure sensor 9 which are the first pressure detecting means for measuring the pressure waveform of these pressures applied to the blood circulating in the extracorporeal circulation circuit are connected to the arterial drip chamber 4 and the venous side. Each is installed in the drip chamber 8. The pressure waveforms measured by the arterial pressure sensor 5 and the venous pressure sensor 9 are as shown in FIG. 5, and the pressure waveforms include pressures of various factors as described above.

  Next, the arterial pressure data of the circulating blood obtained by the arterial pressure sensor 5 and the venous pressure sensor 9 is sent to the control circuit 11 of the dialyzer. The pump control circuit 12 controls the operation of the blood pump 3 based on the rotation frequency according to the instruction from the control circuit 11. Further, a pulse sensor 21 which is a second pressure detecting means for detecting a pressure waveform resulting from the patient's pulse is attached to the patient's arm.

  FIG. 2 is a diagram showing the configuration of this embodiment. The configuration is such that the output signal of the pulse sensor 21 as the second pressure detection means attached to the patient's arm and the output signal of the venous pressure sensor 9 as the first pressure detection means attached to the dialyzer Is input to a multiplier 22 which is a multiplication means. The output of the multiplier 22 is input to a low-pass filter 23 (hereinafter referred to as LPF) that is a DC component extraction means, and the output of the LPF 23 is input to a level detector 24 that is a determination means. Therefore, the blood vessel access monitoring circuit according to the first embodiment includes the pulse sensor 21, the vein side pressure sensor 9, the multiplier 22, the LPF 23, and the level detector 24. The multiplier 22, the LPF 23, and the level detector 24 exist in the control circuit 11, and can be configured by hardware. When the control circuit 11 is configured by a microcomputer or the like, It is also possible to configure with software.

  In the operation in such a configuration, the pressure waveform caused by the pulse is measured by the pulse sensor 21, while the pressure waveform of the circulating blood dialyzed by the vein pressure sensor 9 is measured. The pressure waveform of the circulating blood includes not only the pressure waveform caused by the pulse but also the pressure waveform of the blood pump 3 and the like and the temporary pressure waveform such as the patient turning over.

  Next, the pressure waveform resulting from the pulse and the pressure waveform of the pressure applied to the circulated blood to be dialyzed are input in synchronization with the multiplier 22, and both pressure waveforms are multiplied in the multiplier 22 and output. Is input to the LPF 23. Since the LPF 23 passes only the direct current component, if the direct current component exists in the output of the multiplier 22, the direct current component is also output to the output of the LPF 23. That is, as described above, if there is a pressure wave due to the pulse in the pressure wave of the circulating blood to be dialyzed, a direct current component is output to the multiplication result.

  Next, the DC component that is the output of the LPF 23 is input to the level detector 24. The reason for using the level detector 24 is to detect a direct current component and at the same time to prevent erroneous detection. That is, if only the DC component is detected purely, the reference value Ref of the level detector 24 may be 0, but the reference value is set to a certain level (size or intensity) in order to avoid erroneous detection. In this case, even when a small level of noise or the like is input to the level detector 24, erroneous detection can be avoided. In order to avoid erroneous detection, the level detector 24 may have a time delay element. In other words, if it is confirmed that the pressure wave caused by the pulse is included in the circulating blood only after the time when the input DC component becomes the reference value or more exceeds a certain time, a large level of noise is generated. Even if it is instantaneously input to the level detector 24, erroneous detection can be avoided.

  FIG. 3 shows the output of the LPF 23 before and after the blood vessel cannula 10 is dropped. Before the blood vessel cannula 10 is dropped, the DC component is present above a certain value. The component drops and eventually becomes zero. If the reference value of the level detector 24 is set to Ref, abnormalities in blood vessel access such as dropout of the blood vessel cannula 10 and twisting of the blood vessel tube 2 can be detected at time t2. Here, the level of the reference value is determined by the noise environment of the place where the medical device is installed or the resistance against noise of the medical device.

  In FIG. 2, if the DC component that is the output of the LPF 23 is equal to or greater than the reference value Ref, it means that the blood vessel access is normal. On the other hand, when the vascular cannula 10 is dropped, the direct current component does not exist, so the direct current component, which is the output of the LPF 23, falls below the reference value Ref, and it is determined that the vascular access is abnormal.

  When the blood vessel access is determined to be abnormal by the level detector 24, the blood vessel access alarm 25 is used as a trigger for the operation of the safety device of the medical device, or informs a medical staff or the like by sound or a display. The medical personnel can immediately recognize abnormalities in vascular access.

  In the above description, the case where the venous pressure sensor 9 is used as the first pressure detecting means has been described. However, if the arterial pressure sensor 5 is used instead of the venous pressure sensor 9, the arterial side sensor is similarly used. Abnormalities in vascular access can be monitored. In addition, not only one of the venous pressure sensor 9 and the arterial pressure sensor 5 is used as the first pressure detecting means, but both of the sensors are used at the same time, and the vascular access abnormality on the venous side and It is also possible to detect both vascular access abnormalities on the arterial side.

  Further, although the embodiment using the LPF 23 as the DC component extracting means has been described, it is also possible to extract the DC component by Fourier transforming the output waveform of the multiplier 22 instead of the LPF, and other DC component extracting means. The same effect can be obtained by using.

  In the first embodiment, the case where the medical device is a dialysis device has been described. In the second embodiment, the medical device is an infusion device. FIG. 4 shows an embodiment when the present invention is applied to an infusion device. Unlike a dialysis machine or the like, an infusion device does not circulate blood and does not measure the pressure of circulating blood. In the case of the infusion device, the patient's blood vessel and the infusion tube 200 are connected via the vascular cannula 100. Therefore, the infusion injected into the blood vessel corresponds to the liquid that moves into the blood vessel, and the pressure applied to the infusion is detected by the pressure detecting means 9 as the first pressure detecting means, and the pressure wave and pulse of the infusion pump 300 and the like are detected. The resulting pressure waves are mixed. Therefore, if the pressure waveform that is the output of the pressure detection means 9 and the pressure waveform resulting from the pulse that is the output of the pulse sensor 21 that is the second pressure detection means are input to the multiplier 22, the rest is the same as in the first embodiment. In this way, abnormalities in vascular access such as vascular cannula dropout can be monitored.

It is a figure which shows the structure of the dialysis apparatus to which this invention is applied. It is a figure which shows the structure of one Example of this invention. It is a figure which shows the output of the LPF circuit at the time of blood vessel cannula dropout. It is a figure which shows the structure of the infusion injection apparatus to which this invention is applied. It is a figure which shows the pressure waveform by the side of the artery of the dialyzed blood of a dialyzer, and the vein side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Arterial cannula 2 Blood tube 3 Blood pump 4 Arterial drip chamber 5 Arterial pressure sensor 6 Dializer 7 Bubble sensor 8 Venous side drip chamber 9 Venous pressure sensor 10 Venous cannula 11 Control circuit 12 Pump control circuit 13 Dialysate tube 21 Pulse Sensor 22 Multiplier 23 Low-pass filter 24 Level detector 25 Blood vessel access alarm 100 Blood vessel cannula 200 Infusion tube 300 Infusion pump

Claims (4)

In a vascular access monitoring method in a medical device having a mechanical device coupled to a patient's blood vessel via vascular access and applying pressure to move fluid to the blood vessel,
The pressure waveform of the pressure applied to the liquid and the pressure waveform resulting from the pulse of the patient are measured, the pressure waveform of the liquid and the pressure waveform resulting from the pulse are multiplied, and the resulting waveform is multiplied. A blood vessel access monitoring method comprising: extracting a direct current component and monitoring the abnormality of the blood vessel access by determining a level of the direct current component. The vascular access monitoring method according to claim 1, wherein the pressure waveform of the liquid is measured by at least one of an arterial liquid and a venous liquid. A medical device coupled to a patient's blood vessel via vascular access and having a mechanical device that applies pressure to move liquid into the blood vessel, the first measuring a pressure waveform of the pressure applied to the liquid Pressure detecting means; second pressure detecting means for measuring a pressure waveform caused by the pulse of the patient; multiplication means for multiplying the pressure waveform of the liquid by the pressure waveform caused by the pulse; and the multiplying means. A blood vessel access monitoring circuit comprising: a direct current component extracting means for extracting a direct current component from the multiplication result; and a determining means for measuring a level of the direct current component to determine abnormalities in blood vessel access. apparatus. The medical device according to claim 3, wherein the first pressure detection means measures a pressure waveform of a pressure applied to the liquid at least one of an arterial liquid and a venous liquid.

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