JPH0445687Y2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a catheter for measuring flow rate, particularly a catheter for measuring blood flow rate based on the thermodilution method.

B. Prior Art Conventionally, methods for measuring blood vessel flow velocity include laser Doppler method, pulse modulation Doppler method, ultrasonic Doppler method, Pitot tube catheter method, hot film method, and the like. Further, as methods that can theoretically measure cardiac output (total flow rate), there are impedance method, electromagnetic flowmeter method, admittance splenomography, and the like.

On the other hand, thermodilution and dye dilution using Fick's law are excellent methods for measuring blood flow (particularly cardiac output) without being affected by changes in blood vessel diameter or intravascular flow velocity distribution. law is used. These methods measure the rate at which a physical quantity injected from outside the body, such as the low temperature caused by a cold water mass or the coloring caused by a dye, is diluted by blood, and the cardiac output is determined from this measured value.

According to the thermodilution method, as shown in Figure 7, the vena cava 1
The catheter 2 is guided through the right atrium 4 of the heart 3 and further through the right ventricle 5 to the pulmonary artery 6.
Cold water 7 is injected into the blood, and a sensor (usually a thermistor) 8 near the tip measures changes in blood temperature. That is, the recovery from the low temperature state caused by the cold water 7 due to the blood flow is measured by the thermistor 8 as a change in resistance. In the figure, 9 is the left atrium, 10 is the left ventricle, 11 is the pulmonary vein, and 12 is the aorta. The catheter 2 is shown in FIGS. 7, 8, 9, and 10.
As shown in the figure, the main body 13 includes a side hole 14 for injecting cold water, a thermistor 8, and a balloon 1.
6. Side holes 31 are provided for supplying and exhausting air to the balloon 16, and correspondingly, a lumen (not shown) for supplying cold water and wiring 3 for the thermistor 8 are provided.
18 lumens for pressure measurement, 1 lumen for pressure measurement
9, a lumen 20 for feeding air into the balloon 16, and a second pressure measuring lumen (not shown) for measuring blood pressure on the upstream side. Then, as shown in Fig. 7, the catheter 2
When inserting (usually percutaneously inserting) the catheter 2 into the bloodstream, the balloon 16 is inflated (as shown by the dashed line in FIG. 8) and the catheter 2 is carried.

A blood flow calculation display device 37, a syringe 41 for balloon expansion/deflation, and an infusion bottle 42 (syringe barrel 43 and sterilization filter) are connected to the catheter 2 inserted into the living body via the connectors 33, 35, and 44 (included) is connected. The blood flow calculation display device 37 is provided with a blood flow meter 47, a condition setting key 46, and the like. The injection liquid 7 used above is injected after being cooled to a predetermined temperature, and its types include maintenance liquids used for maintaining body fluids of patients;
Alternatively, it is preferable to use intravenous fluids for nutritional support. In other words, by using such maintenance fluids or infusions, it is possible to replenish maintenance fluids, etc. at the same time as measuring blood flow, which is very efficient and allows for the injection necessary for thermodilution without losing the balance of body fluids. liquid can be supplied.

In the above, the blood temperature change obtained by the sensor 8 is converted into cardiac output using the following equation (1).

Vb=Vi(Tb-Ti)60/∫ ∝/o ΔTb(t)dt ×Ci-Si/Cb・Sb...(1) [However, Vb: cardiac output (blood flow rate) Vi: injected Amount of cold water (ml) Tb: Temperature of blood before cold water injection (°C) Ti: Temperature of injected cold water (°C) Cb: Specific heat of blood Sb: Specific gravity of blood Ci: Specific heat of injected water Si: Specific heat of injected water Specific gravity t: Time (seconds) ΔTb: Blood temperature change In this case, in measuring blood flow, the signal is processed according to the flow shown in FIG. That is, the measured value of the temperature measurement unit 21 that measures the temperature of the liquid injected into the catheter 2 is input to the A/D converter 26 and digitized, and the thermistor 8 of the catheter 2 detects the blood temperature as a change in electrical resistance. , this is extracted as a current signal by the bridge circuit 23 and sent to the amplification circuit 24.
The signal is amplified by , and then input to the A/D converter 26 through an automatic zero adjustment circuit 25 that compensates for drift over time. The output of the A/D converter 26 is processed by a central processing unit (CPU) 45, and the blood flow rate is displayed on a display device 37 and further recorded on a printer 27.

Incidentally, in the above catheter 2, the sensor 8 constituting the temperature measuring section 28 is fixed with an adhesive 29 in direct contact with the catheter body 13, as shown in FIGS. 9 and 10. Because of the heat transfer between these and the blood flowing outside (that is, heat transfer from the blood to the sensor 8
and conduction via the adhesive 29), the temperature is measured by the sensor 8. However, since the amount or rate of heat transfer through the main body 13 and the adhesive is generally low, it takes a long time for the sensor 8 made of a thermistor to detect a predetermined temperature. Therefore, even if the blood flow rate is calculated based on the above-mentioned Hook's law, it will be the true blood flow rate and will have a large error. This tendency becomes particularly noticeable as the heart rate increases.

C. Purpose of the invention The purpose of the present invention is to provide a flow rate measuring catheter that greatly reduces measurement errors, enables accurate measurement, and allows smooth insertion and removal into a living body.

D. Structure of the invention That is, the present invention provides a catheter used for measuring the flow rate of a fluid by the thermodilution method, in which a temperature measuring element for measuring the temperature of the fluid is removable between the catheter body and the outer surface thereof. The present invention relates to a flow rate measuring catheter characterized in that it is disposed in a catheter body.

Example Examples of the present invention will be described below.

1 to 3 show a catheter 22 for measuring blood flow based on the thermodilution method according to the first embodiment of the present invention.
This shows that. However, parts common to those described in FIGS. 6 to 9 are given common reference numerals, and their explanations may be omitted.

This catheter 22 is fundamentally different from the conventional catheter 2 described above, in particular, a sensor 8 for measuring blood flow is disposed at the tip of a lumen 58 provided in the catheter body 13, and the sensor 8 is disposed on the outer surface of the same position. A small piece-shaped opening/closing part 13a covering the side is molded so as to be elastically deformable integrally with the main body 13, and a hollow support member 5 through which wiring 34 is passed as shown in FIG.
By pushing 0 in the direction of arrow 51 with a force from outside the body, the sensor 8 at the tip elastically deforms (rotates) the opening/closing part 13a upward and is exposed (protrudes) onto the outer surface of the main body 13. has been done. For this purpose, the base 52 of the opening/closing part 13a is formed as a hinge part, for example, and is configured to rotate counterclockwise or clockwise (however, it rotates clockwise by elastic restoring force). Further, the tip of the opening/closing part 13a is tapered 53 so that there is no step or gap between the opening and closing part 13a and the main body 13 in the closed state. Second
When the support member 50 is pulled in the direction opposite to the arrow 51 from the state shown in the figure, the opening/closing part 13a is further pushed open by the sensor 8, and then the sensor 8 is dragged into the lumen 58. The opening/closing portion 13a elastically restores to its original state and returns to the state shown in FIG.

In this way, according to this embodiment, the sensor 8 is placed between the catheter body 13 and its outer surface so that it can be taken in and out, so when inserting the catheter 22 into the blood vessel of the living body, the sensor 8 is inserted into the blood vessel of the living body as shown in FIG. Like sensor 8
is placed in the lumen 58 to make the outer surface of the main body flat, making it easy to insert the sensor 8. After being indwelled in the blood vessel, the support member 50 is pushed as shown in FIG. the blood temperature is measured. Therefore, when measuring,
As already mentioned, heat transfer between the sensor 8 and the blood no longer takes place via the catheter body 13;
This occurs directly with the blood (this is done in both cases of heating and cooling by the blood).As a result, the sensor 8 quickly responds to changes in blood temperature and detects the changes. Since the temperature can be detected, the thermal time constant during temperature measurement is reduced, and measurement errors are significantly reduced, making it possible to perform accurate measurements.

Also, when removing the catheter 22 from inside the blood vessel, the sensor 8 can be retracted into the lumen 58 in the same way as when inserting the catheter 22 described above, so that the operation can be smoothly carried out when inserting and removing the catheter 22 through the blood vessel (and even the skin). It can be performed.

FIG. 4 shows an example in which the opening/closing part 13a shown in FIG. 1 is removed to form an opening 60 for inserting and removing the sensor 8.

In this example, as well as the above example, during measurement, the sensor 8 can be placed with a small contact area with the catheter body 13 as shown by the dashed line (or it is possible to have no contact at all), so the measurement can be performed accurately. Ru. Moreover, since the sensor 8 can be retracted as shown by the solid line when the catheter 22 is inserted or removed, there is no problem with the operation. The presence of the opening 60 makes it easier for blood to enter the lumen 58, but this can be done by providing a seal ring 61 in the lumen 58 that ensures movement of the support member 50 while also providing sealing performance. It can be resolved. . This seal ring may be similarly employed in the catheters shown in FIGS. 1 to 3 (and also in FIGS. 5 and 6, which will be described later).

5 and 6 show still another embodiment of the present invention.

According to this example, a lumen 78 into which the support member 50 of the sensor 8 is inserted is provided on one side of the catheter body 13, and the end of the lumen 78 (i.e., the location where the sensor 8 is located) is cut out to form an elongated opening 70. That's what I'm saying.

Therefore, when the catheter 22 is inserted or removed as indicated by the solid line in FIG. 6, and the support member 50 is pushed as shown by the dashed-dotted line, the support member 50 hits the wall surface of the main body 13 at the tip of the lumen 78. ) At the same time, the support member 5
0 is elastically bent upward and the sensor 8 is connected to the main body 13.
lifted onto the outer surface of the By measuring the blood temperature in this state, accurate measurement with less error becomes possible. Moreover, if the force on the support member 50 is released, it can be returned to the original state shown by the solid line.

In addition, in this example, 13 is shown in Figures 1 to 3.
An opening/closing section similar to that shown in a may be provided to close the opening. However, in this case, it is preferable that the opening/closing part be opened in a double-opening manner so that it opens from exactly the position of the sensor 8 to both sides.

Although the present invention has been illustrated above, the above-mentioned example can be further modified based on the technical idea of the present invention.

For example, the structure of the above-mentioned temperature measurement section (sensor 8 part) may be modified in various ways, and the structure for inserting and removing it is not limited to that described above. Also,
The sensor 8 can also use a thermocouple instead of a thermistor. The type, size, structure, material, etc. of each part of the catheter can be varied.

Note that the catheter of the present invention is not only inserted into the heart as described above, but can also be applied to other sites.

F. Functions and Effects of the Invention As mentioned above, in this invention, the temperature measuring element for fluid such as blood is placed in and out of the catheter body, so when it is inserted into and removed from a living body, the temperature measuring element is placed inside the catheter body. It can be retracted to make its outer surface flat, so it does not interfere with work. Furthermore, after indwelling in a living body, the temperature measuring element can be exposed on the outer surface of the catheter body, and temperature can be measured directly from the fluid, allowing rapid response to and detection of temperature changes in the fluid. Therefore, the thermal time constant during temperature measurement becomes small, so that measurement errors are significantly reduced and accurate measurement is possible.

[Brief explanation of drawings]

1 to 6 show an embodiment of the present invention, in which FIG. 1 is an enlarged sectional view of the main part of the catheter, FIG. 2 is a sectional view similar to FIG. 1 when the sensor is exposed, 3 is a plan view of FIG. 1 (- line cross section in FIG. 3 is FIG. 1), FIG. 4 is a sectional view similar to FIG. 1 of a catheter according to another example, and FIG. A plan view of the catheter according to the example, FIG. 6 is a sectional view taken along the line -- of FIG. 7 to 10 show conventional examples, in which FIG. 7 is a schematic sectional view showing the state of catheter insertion during blood flow measurement, FIG. 8 is a schematic front view of the catheter, and FIG. 9 is a blood vessel. FIG. 8 is an enlarged cross-sectional view taken along the line -- in FIG. 8 showing the catheter inside along with the circuit system, and FIG. 10 is an enlarged cross-sectional view taken along the line -- in FIG. In addition, in the symbols shown in the drawings, 1... vena cava, 2, 22... catheter, 4... right atrium, 5
...Right ventricle, 6...Pulmonary artery, 7...Infusion fluid, 8...
...Sensor (thermistor), 13... Catheter body, 13a... Opening/closing part, 34... Wiring, 50...
Supporting member, 58, 78... lumen, 61... sealing material, 70... opening.

Claims (1)

[Scope of utility model registration request] A catheter used for measuring the flow rate of fluid by a thermodilution method, characterized in that a temperature measuring element for measuring the temperature of the fluid is disposed on the catheter body so as to be removable between the catheter body and the outer surface thereof. A catheter for measuring flow rate.