JPH05137725A - Ultrasonic doppler blood flow quantity monitor - Google Patents

Abstract

PURPOSE:To provide the blood flow quantity monitor which can measure continuously the blood flow quantity, based on the blood flow quantity by a heat dilution method as a reference. CONSTITUTION:In a catheter 1 inserted into a blood vessel, plural ultrasonic vibrators are provided, and based on ultrasonic signals transmitted and received by these vibrators, the blood flow quantity is calculated continuously in an ultrasonic Doppler blood flow quantity measuring part 3, and also, in addition thereto, the blood flow quantity is calculated by a heat dilution method blood flow quantity measuring part 2. By the blood flow quantity derived by this heat dilution method, the blood flow quantity derived by the ultrasonic signal is calibrated. In such a way, by calculating continuously the blood flow quantity, based on the ultrasonic signal, a heart function is monitored with the same effect as the blood flow quantity is measured continuously by the heat dilution method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention inserts a catheter equipped with an ultrasonic transducer into a blood vessel, transmits and receives ultrasonic waves to and from a blood flow, and calculates the blood flow based on the obtained ultrasonic Doppler signal. The present invention relates to a blood flow monitoring device.

[0002]

2. Description of the Related Art In recent years, due to the development of medical technology, it has become possible to perform surgery and to treat diseases and the like which were conventionally difficult to treat surgically. Moreover, such complicated surgery tends to take a long time, and it is very important for the surgeon to monitor the cardiac function appropriately during the long operation and grasp the patient's condition at any time. That is.

At present, as a monitor of cardiac function during and after surgery, it is general to determine the cardiac output by the thermodilution method. In the thermodilution method, a catheter is inserted through the jugular vein or femoral vein, and the catheter tip is passed through the vena cava, right atrium, and right ventricle to reach the pulmonary artery. Then, cold water is injected into the right atrium through this catheter, the temperature of blood in the pulmonary artery is detected by a temperature sensor provided in the catheter, and the cardiac output is calculated from the change over time of this temperature. As described above, since the thermodilution method is a method of injecting cold water into blood, it means that the instantaneous cardiac output is measured during the injection of cold water, and the cardiac output cannot be continuously measured.

However, the information actually desired in patient management is the cardiac function data at any time, and it is more preferable if this can be continuously monitored. In this respect, the thermodilution method, which can measure only cardiac output during cold water injection, is not a satisfactory method. In other words, in the thermodilution method, a sudden change in the patient's condition during surgery cannot be detected immediately, and the response may be delayed.

A device for improving the above problems of the thermodilution method and continuously monitoring the heart function is provided by CARDIOMET.
ORICS is developing it. This device is DOPCO
It is called M / FLOWCATH, and a catheter equipped with an ultrasonic Doppler transducer is inserted into the pulmonary artery, and based on the received ultrasonic Doppler signal, the blood vessel volume or cardiac output is measured by measuring the blood vessel inner diameter and the blood flow velocity. The amount is obtained, and thereby the cardiac function is monitored. FIG. 7 (A),
The main part of the catheter 50 of this device is shown in FIG. First
The ultrasonic transducer 51 is arranged so as to transmit and receive ultrasonic waves at a predetermined angle with respect to the blood flow direction.
The second and third ultrasonic transducers 53 are arranged so as to transmit and receive ultrasonic waves in directions perpendicular to the catheter 50 and opposite to each other. In this device, the blood flow velocity is calculated based on the ultrasonic Doppler signal in only one direction. That is, from the Doppler frequency shift of the ultrasonic waves transmitted and received by the first ultrasonic transducer 51, the velocity component (v
_{α 2} ) is calculated and further corrected by the incident angle (α) of the ultrasonic wave with respect to the blood flow direction to calculate the absolute value (v) of the blood flow velocity. However, here, the catheter is arranged parallel to the blood flow direction, and the incident angle (α) of the ultrasonic waves is equal to the installation angle of the first transducer 51 with respect to the catheter. The following equation is given by the equation.

V = v _α × cos α Also, ultrasonic waves are transmitted and received by the second oscillator 52 and the third oscillator 53, and the distances d ₁ and d ₂ to the inner wall 91 of the blood vessel are measured. The blood vessel inner diameter (D) is the sum of the above d ₁ and d ₂ and the distance d ₀ between the second oscillator 52 and the third oscillator 53.

D = d ₁ + d ₂ + d _{0 From} this, the blood vessel cross-sectional area (A) is calculated. As described above, the blood flow rate (Q) is calculated as the product of the obtained cross-sectional area (A) and the blood flow velocity (v), and the heart function is monitored using this.

[0008] ^{A = πD 2/4 Q =} v × A

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the OM / FLOWCATH device, the catheter 5
The blood flow velocity is calculated assuming that the direction of 0 is arranged parallel to the blood flow direction (v), and the blood flow rate is calculated assuming that the measured distance between blood vessel walls is the blood vessel diameter. However, the blood flow direction (v) and the direction of the catheter 50 are not always parallel, such as when affected by the bent portion of the blood vessel. The state in this case is shown in FIG. Also,
The distance between the blood vessel walls is not always able to measure the blood vessel diameter when the catheter 50 is not located in the center of the blood vessel, and the blood vessel cross-sectional shape is not necessarily circular. FIG. 9 shows a state in which the catheter 50 is not located in the center of the blood vessel and is biased.

As described above, if the direction of blood flow (v) and the direction of the catheter 50 are not constant, the incident angle (α) of ultrasonic waves will not be constant, and the blood flow velocity (v) calculated based on this will not be constant.
Will include an error. When the catheter 50 is biased, the inner diameter of the blood vessel is smaller than the actual inner diameter (D) (D
₁ ) is measured, and the cross-sectional area (A) calculated from this also contains an error. Therefore, blood flow velocity (v)
Blood flow (Q) calculated as the product of blood vessel cross-sectional area (A)
Also includes an error.

Further, most of the clinical data obtained at present are those obtained by the thermodilution method, and DOPCO
The clinical data from the M / FLOWCATH device are still small and not reliable enough for practical use during surgery.

As described above, DOPCOM / FLOWC
In blood flow measurement with an ATH device, (a) the calculated blood flow velocity and blood vessel cross-sectional area include errors,
The accuracy of the blood flow calculated from this is not sufficient. (B) The clinical data for blood flow measurement with this device are still small, and it has not been possible to obtain a sufficient amount of accumulated data as a monitor of cardiac function during surgery. There is a problem.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a blood flow monitoring device capable of continuously measuring the blood flow based on the blood flow by the thermodilution method. ..

[0014]

An apparatus according to the present invention is a blood flow measuring unit for measuring a blood flow by a thermodilution method at a predetermined time interval, and a blood flow is continuously measured based on an ultrasonic Doppler signal. An ultrasonic Doppler blood flow measuring unit, calibrates the blood flow measured from the Doppler signal by the blood flow measured by the thermodilution method, and calibrates the calibrated reference blood flow and the continuously measured ultrasonic Doppler. A blood flow correction unit for calculating a blood flow equivalent to that continuously measured by the thermodilution method by comparing the blood flow based on the signal.

Further, the apparatus according to the present invention comprises a blood flow measuring unit for measuring a blood flow by a thermodilution method at a predetermined time interval, and an ultrasonic Doppler for continuously measuring a blood flow velocity based on an ultrasonic Doppler signal. A blood flow velocity measurement unit, a coefficient indicating these relationships is calculated from the blood flow rate measured by the thermodilution method and the blood flow velocity measured by the ultrasonic Doppler signal, and the coefficient and the ultrasonic Doppler signal are calculated. And a blood flow rate calculating section equivalent to a blood flow rate continuously measured by the thermodilution method for continuously calculating the blood flow rate.

[0016]

The blood flow rate calculated based on the ultrasonic Doppler signal is calibrated by the blood flow rate obtained by the thermodilution method, so that the blood flow rate is continuously measured based on the thermodilution method. This allows continuous monitoring of cardiac function during and after surgery.

Further, the blood flow velocity calculated based on the ultrasonic Doppler signal is compared with the blood flow velocity obtained by the thermodilution method, and the coefficient showing the relationship between them is obtained. Then, by continuously measuring the blood flow velocity, the same measurement result as that obtained by continuously measuring the blood flow volume by the thermodilution method is obtained. This allows continuous monitoring of cardiac function during and after surgery.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the overall construction of the first embodiment. Reference numeral 1 is a catheter to be inserted into a blood vessel. The apparatus main body is provided with a thermodilution method blood flow measuring unit 2 and an ultrasonic Doppler blood flow measuring unit 3 for calculating the blood flow based on the signal sent from the catheter 1, and both blood flow measuring units 2 , 3 for comparing and correcting the blood flow rates calculated by 3 and 3, the determination section 1 for instructing the alarm device 11 to issue an alarm when the corrected blood flow rate is below a predetermined value.
0 is provided with a display unit 9 for displaying the blood flow rate. The ultrasonic Doppler blood flow measuring unit 3 includes a blood vessel cross-sectional area measuring unit 4, a blood flow velocity measuring unit 5, and an ultrasonic Doppler blood flow calculating unit 6. The heart rate detecting unit 7 detects a heartbeat by an electrocardiographic electrode attached to the patient, and sends this heartbeat signal to the blood flow velocity measuring unit 5 and the thermodilution blood flow measuring unit 2.

FIG. 2 is a view showing the details of the distal end portion of the catheter 1. Reference numerals 21 and 22 denote ultrasonic transducers for measuring the blood flow velocity, which are arranged on the catheter 1 so as to have different incident angles with respect to the blood flow. 23,
Reference numeral 24 is an ultrasonic transducer for measuring the distance between the inner walls of blood vessels, and is arranged so as to transmit ultrasonic waves in directions orthogonal to the axis of the catheter 1 and in directions opposite to each other. Two
Reference numeral 5 is a water injection hole for injecting cold water into the right atrium when measuring the blood flow by the thermodilution method, and 26 is a temperature detection unit for detecting the temperature of blood in the pulmonary artery with a thermistor. 27
Is a balloon that carries the catheter 1 on the bloodstream and sends it through the right atrium to the pulmonary artery.

The balloon 27 is made of a stretchable material such as rubber and is usually in close contact with the catheter 1. However, when a liquid (eg, physiological saline) is injected through the tube from the other end, the balloon 27 is inflated as shown in the figure. A part thicker than the diameter of the catheter 1 is formed at a part of the tip of the catheter 1. When the distal end of the catheter 1 is inserted into a vein and the balloon is inflated as described above, the catheter 1 rides on the blood flow of the vena cava 92 and is sent to the heart, passing through the right atrium 93 and the right ventricle 94 to the pulmonary artery 95. Reach Then, the liquid in the balloon is drained to fix the position of the catheter. FIG. 3 shows a state where the catheter has reached a predetermined position.

In this state, the ultrasonic transducers 21 and 2 are
2, 23, 24 and the temperature detection unit 26 are arranged in the catheter 1 so as to be located in the pulmonary artery 95, and the water injection hole 25 is arranged in the catheter 1 so as to be located in the right atrium 93.

Measurement of blood flow by thermodilution method When a predetermined amount of cold water is injected into the right atrium 93 through the water injection hole 25 provided in the catheter 1, the temperature of the blood in the right atrium 93 decreases. This low-temperature blood is sent to the right ventricle 94 and the pulmonary artery 95 as the heart beats. When the cardiac output is large, the low temperature blood in the right atrium 95 is promptly sent to the pulmonary artery 95, and the temperature of the blood in the pulmonary artery 95 also decreases, but the temperature returns to the normal temperature quickly. On the contrary, when the cardiac output is small, it takes time for the once lowered blood temperature to return to the normal temperature. The thermodilution method measures cardiac output, that is, blood flow (Qn) based on such a temperature history.

Measurement of Blood Flow by Ultrasonic Wave Ultrasonic waves are transmitted to the bloodstream and reflected waves are received from the above-mentioned two ultrasonic transducers 21 and 22. At this time, the ultrasonic waves are arranged on the catheter so that the incident angles (α, α + θ) of the ultrasonic waves with respect to the blood flow direction are different. The details are shown in Fig. 4.
Shown in. The received signal of the reflected wave received by each of the transducers is sent to the blood flow velocity measuring unit 5. Due to the Doppler effect, the frequency of this reflected wave deviates in accordance with the blood flow velocity. The relationship between the Doppler shift frequency (Δf ₁ , Δf ₂ ) obtained from both of these oscillators and the blood flow velocity v is expressed by the following equation.

Δf ₁ = (2 * f _c ) * v * cos α (1) Δf ₂ = (2 * f _c ) * v * cos (α + θ) (2) f _c Transmit ultrasonic wave (reference wave) Frequency c Sound velocity in living body v Blood flow velocity α Incident angle of transmitted ultrasonic wave with respect to blood flow direction θ Angle between two ultrasonic wave transmission / reception directions Blood flow velocity measuring unit 5 receives signals transmitted from both transducers. Based on the Doppler shift frequency (Δf ₁ ,
Calculate Δf ₂ ).

By eliminating α from the above two equations, the following equation is obtained.

V = {c / (2 * f _c * sin θ)} * {(Δf ₁ ) ² −2 * Δf ₁ * Δf ₂ * cos θ + (Δf ₂ ) ² } ^1/2 (3) Based on the blood flow velocity measuring unit 5, the ultrasonic wave incident angle (α)
Blood flow velocity (v) that is not affected by By transmitting and receiving ultrasonic waves from two directions in this manner, the blood flow velocity (v) can be calculated even when the catheter 1 is affected by the bent portion of the blood vessel and the direction is not parallel to the blood flow direction. ..

As described above, in order to measure the absolute value of the blood flow velocity irrespective of the incident angle of the ultrasonic wave, Doppler measurement may be performed from at least two directions, and the transducer shown in FIG. Arrangement is sufficient. However, it is more desirable that the arrangement directions of the two vibrators are orthogonal to each other in terms of manufacturing ease and accuracy control. 4B and 4C show an example of the arrangement of the transducers in this case, that is, θ = 90 °. At this time, the equation (3) is simplified as the following equation.

V = {c / (2 * f _c )} * {(Δf ₁ ) ² + (Δf ₂ ) ² } ^1/2 (4) In these oscillator arrangements, each of the oscillators 21 and 22 is Although the sample points cannot be the same point, the depth of the sample points is about 1 cm, considering the measurement of blood flow velocity in the blood vessel. It is possible to keep the distance between sample points within 2 cm. Within this range, the direction of blood flow may be almost constant, and there is no problem in calculating the blood flow velocity.

Further, in the arrangement of the transducers shown in FIG. 4B, since ultrasonic waves from the two transducers intersect, it is necessary to alternately transmit and receive with the two transducers. In the arrangement of the transducers shown in FIG. 4), the interval between the sampling points is further widened as compared with FIG. It is possible to measure up to the flow velocity.

The ultrasonic transducers 23 and 24 irradiate ultrasonic waves to the inner wall of the blood vessel and receive reflected waves, as in the conventional example.
The blood vessel cross-sectional area measurement unit 4 calculates the distance to the inner wall of the blood vessel based on the time from the transmission of the ultrasonic wave to the reception thereof, and calculates the cross-sectional area (A) of the blood vessel. As described above, the blood flow rate (Qd) is calculated from the calculated blood flow velocity (v) and blood vessel cross-sectional area (A).

Correction of blood flow rate Although the blood flow rate (Qn, Qd) can be calculated by the above two methods, the blood flow rate cannot be continuously measured by the thermodilution method as described above. Therefore, first, the blood flow rate is measured at the same time by the thermodilution method and ultrasonic Doppler, and the blood flow rate correction unit 8 measures the blood flow rate (Qn
), The blood flow volume (Qd) by ultrasonic Doppler is calibrated, and this blood flow volume is used as the reference blood flow volume (Qd0). After that, only the blood flow rate (Qd1) by ultrasonic Doppler is measured, and the blood flow rate is continuously calculated based on the following equation. Q = (Qd1 / Qd) · d0 (5) In this way, the blood flow rate in the pulmonary artery, that is, the cardiac output is measured, and in this manner, the cardiac output equivalent to that measured by the thermodilution method is obtained. The measurement can be performed continuously. Further, the correction by the thermodilution method may be performed at predetermined time intervals if necessary.

As described above, the calculated cardiac output can be displayed on the display unit 9 and monitored in real time during and after the operation. When the patient's condition changes and the cardiac output decreases, in order to immediately notify the operator of this, the determination unit 10 alerts the alarm device 11 when the cardiac output falls below a predetermined value. Instruct to emit.

5 and 6 show a second embodiment of the blood flow monitoring device according to the present invention. FIG. 5 is a diagram showing the entire configuration of the second embodiment. The difference from the first embodiment is that the blood vessel cross-sectional area measurement unit 4 and the ultrasonic Doppler blood flow calculation unit 6 are eliminated, and the blood flow correction unit 8 is This is the point of the flow rate calculation unit 12. Further, FIG. 6 shows the distal end portion of the catheter, and the difference from the catheter of the first embodiment is that the ultrasonic transducers 23 and 24 for measuring the inner diameter of the blood vessel are not provided. Other configurations are the same as those of the first embodiment, and these are denoted by the same reference numerals as those of the first embodiment, and description thereof will be omitted.

The difference of this embodiment from the first embodiment is that the blood flow rate is not calculated from the ultrasonic Doppler signal, but the blood flow velocity is directly compared with the blood flow rate obtained by the thermodilution method.

The blood flow rate calculation unit 12 calculates the equation (6) from the blood flow rate (Qn) calculated by the thermodilution method and the blood flow rate (v) calculated by the blood flow rate measurement unit 5 which is measured at the same time. ), The flow rate coefficient (k) is obtained, and thereafter the blood flow rate (Q) is continuously calculated from the blood flow velocity (v) and the flow rate coefficient (k) according to the equation (7).

K = Qn / v (6) Q = k × v (7)

[0038]

As described above, according to the present invention, the cardiac output can be continuously measured, and the cardiac function can be continuously monitored. As a result, it is possible to immediately detect a sudden change in the patient's condition and quickly respond to this. In addition, it is possible to minimize dilution of blood concentration by injecting cold water into the blood vessel for measurement by the thermodilution method.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of a blood flow monitoring device according to the present invention.

FIG. 2 is a detailed view of the catheter tip end portion of the first embodiment.

FIG. 3 is a diagram showing a state in which a tip of a catheter reaches a pulmonary artery.

FIG. 4 is a diagram showing an arrangement example of ultrasonic transducers.

FIG. 5 is a configuration diagram of a second embodiment of the blood flow monitoring device according to the present invention.

FIG. 6 is a detailed view of the catheter tip end portion of the second embodiment.

FIG. 7 is an explanatory view of a conventional blood flow measuring device.

FIG. 8 is an explanatory diagram of a conventional blood flow measuring device.

FIG. 9 is an explanatory diagram of a conventional blood flow measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Catheter 2 Thermodilution method blood flow measurement unit 3 Ultrasonic Doppler blood flow measurement unit 8 Blood flow correction unit 9 Display unit 10 Judgment unit 11 Alarm device 12 Blood flow calculation unit 21, 22 Ultrasonic transducer for blood flow measurement 23 , 24 Ultrasonic transducer for measuring the inner wall spacing of blood vessels

Claims (2)

[Claims] 1. A blood flow measuring unit for measuring a blood flow by a thermodilution method at a predetermined time interval, an ultrasonic Doppler blood flow measuring unit for continuously measuring a blood flow based on an ultrasonic Doppler signal, Calibrating the blood flow measured from the Doppler signal with the blood flow measured by the dilution method, and comparing the calibrated reference blood flow with the blood flow based on the continuously measured ultrasonic Doppler signal. And a blood flow correction unit that continuously calculates a blood flow equivalent to that measured by the thermodilution method. 2. A blood flow measuring unit for measuring a blood flow at a predetermined time interval by a thermodilution method, and an ultrasonic Doppler blood flow measuring unit for continuously measuring a blood flow based on an ultrasonic Doppler signal. From the blood flow rate measured by the thermodilution method and the blood flow velocity measured from the ultrasonic Doppler signal, a coefficient indicating these relationships is calculated, and the coefficient and the ultrasonic Doppler signal are continuously measured. And a blood flow rate calculating unit that calculates a blood flow rate equivalent to that continuously measured by the thermodilution method from the blood flow rate.