WO1993021822A1

WO1993021822A1 - Device for determining the volume and/or throughflow of a section of a human or animal circulatory system

Info

Publication number: WO1993021822A1
Application number: PCT/EP1993/001034
Authority: WO
Inventors: Ulrich Pfeiffer; Reinhold Knoll
Original assignee: Ulrich Pfeiffer; Reinhold Knoll
Priority date: 1992-04-29
Filing date: 1993-04-29
Publication date: 1993-11-11
Also published as: EP0592644A1; DE4214068A1

Abstract

A device for determining the volume and/or throughflow of a section of a human or animal circulatory system has a liquid reservoir (1) containing a liquid kept at a temperature different from that of the blood of the patient, an injection device (12) linked by a pumping device (3) to the liquid reservoir (1) in order to inject liquid from the liquid reservoir (1) into the circulatory system of a patient, a temperature sensor (13) for measuring the temperature in the circulatory system of the patient downstream of the injection spot and an evaluating device (20) which receives the measurement values from the temperature sensor (13) and other measurement parameters. The injected liquid is kept at the ambient temperature and the pumping device (3) injects the liquid in pulses, so that measurement can be continuously carried out while injecting each time a small amount of liquid.

Description

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Device for determining the volume and / or the throughput of a circulatory section of humans or animals

description

The invention relates to a device for determining the volume and / or the throughput of a circulatory section of humans or animals with a liquid supply which contains a liquid with a temperature deviating from the blood temperature of the patient, an injection device connected to the liquid supply via a pump device Injecting liquid from the liquid supply into the patient's circuit, a temperature sensor for measuring the temperature in the patient's circuit at a point in the flow direction behind the injection point and an evaluation device at which the measured values of the temperature sensor and further measurement parameters lie.

Such a device can be used, for example, to measure the volume of any section of a patient's blood circulation and / or to measure the blood to determine throughput in this section. However, such a device can be used in particular to monitor the cardiac output and the circulatory filling status of a patient. For this purpose, the liquid is intravenously infused with simultaneous thermodilution measurement by evaluating the resulting temperature profile of the blood mixed with the liquid.

In particular, the intensive medical control of a seriously ill patient requires knowing the cardiac output and the circulatory filling condition. The cardiac output, i.e. the blood volume that the heart pumps per unit of time is usually determined by means of dilution. The circulatory filling state is then estimated from the blood volume in the anterior chambers of the heart or in the heart chambers themselves. Since no practical methods for direct measurement of these volumes have been available to date, in clinical practice the blood volume in the atria of the heart is estimated indirectly from the hydrostatic pressure caused by the corresponding volume.

A catheter, for example a so-called pulmonalis thermodilution catheter, is inserted into the patient to measure the cardiac output and to assess the circulatory filling condition by means of the device mentioned at the beginning. This catheter has a first channel that ends in front of the right ventricle (so-called proximal lumen) and is freely in contact with the blood stream, and a second channel that ends behind the right ventricle in the artery pulmonalis (so-called distal lumen) and is in free contact with the blood stream, via a further third closed channel, which enables the inflation of a balloon at the tip of the catheter in the pulmonary artery, and via a fourth channel, likewise closed off from the blood flow, in which the electrical connections of the placed at the tip of the catheter in the pulmonary artery Temperature sensor are guided.

The cardiac output is then determined using the thermodilution method. For this purpose, a certain amount of cooled, especially ice-cold glucose or saline solution is injected via the proximal lumen in front of the right ventricle. The indicator solution mixes with the blood and is pumped from the right ventricle into the pulmonary artery. The temperature drop behind the right ventricle resulting from thermodilution is registered in the pulmonary artery by means of the temperature sensor.

Cardiac output (cardiac output) can be calculated in the following way: m (l)

(GI.1) HZV =

J c (l) German

Applied to thermodilution, this equation is:

| ^* σ _B -η ^{) *} K

(GI.2) HZV =

AT German

/ where V _j = injectate volume T _ß = blood temperature T _j = injectate temperature K = correction factor for specific weight and specific heat of the injectate and blood T = blood temperature t = time

In practice, the thermodilution measurement is carried out when the doctor considers it necessary. For this purpose, a syringe is filled with the cooled injectate and after initialization of the evaluation device, for example a cardiac output computer, injected into the right ventricle via the injection channel of the pulmonary irrigation catheter. The cardiac output computer uses the measured values of the temperature sensor, which is attached distally to the catheter, to follow the temperature profile over time in the pulmonary artery and calculates the cardiac output from the above-mentioned integral and the variable V _j , T _ß , T _j and the constant K volume.

The patient's circulatory filling condition is assessed by measuring the hydrostatic pressures in the antechambers. The pressure in the right ventricle of the heart (central venous pressure CVP) and indirectly in the left ventricle of the heart (pulmonary capillary closure pressure = PCWP) can thus be determined by means of the pulmonary thermodilution flushing catheter. Since these are relatively low pressures of a few cm H ₂ O, errors due to measurement technology occur relatively frequently. In addition, these pressures are, under certain circumstances (for example in the case of positive pressure ventilation) not representative of the volume in the respective heart anterior chamber. As far as measurement technology is concerned, a measurement process must always be carried out to determine these pressures, which necessitates the presence of a doctor or a person commissioned by him.

The cardiac output and the circulatory filling status are parameters relevant to survival. They can change to life-threatening proportions within a few minutes. For example, the circulatory filling state and, as a result, the cardiac output can decrease as a result of acute internal bleeding. In order to be able to recognize such situations at an early stage, a continuous or as frequent as possible measurement of the cardiac output would be desirable. In the method described above, in which the device mentioned at the outset is used, the cardiac output and the circulatory filling condition of a patient can only be determined be averaged if the doctor or one of his representatives takes a corresponding measurement. As a result, no more than 12 to 18 cardiac output and circulatory fill condition measurements are usually performed on a patient per day. The measurements are usually carried out in series of six measurements three times a day. The result of this is that at intervals of approximately 8 hours on average between the individual measurement series, rapid deteriorations in the health status of a patient are often detected far too late.

Since ice-cold injections were previously used in thermodilution measurements, a loss of cold occurs, which can no longer be neglected with small amounts of injectate. The cold loss was previously taken into account by an empirical correction value which is dependent on the catheter type. Due to the large time constant of the heat transfer from the dormant liquid in the pipe system to the surrounding air (50s), the thermal equilibrium required for such a correction cannot be established with frequent injection. Since the proportion of dead space volume to be taken into account (1.2ml) is very large for small quantities of injectate, a large error arises. Measurements with small amounts of injectate have therefore not been possible until now.

The object on which the invention is based is to design the device of the type mentioned at the outset in such a way that permanent determination of the volume and throughput in the respective circulatory section and, in particular, permanent monitoring of the cardiac output and the circulatory filling condition of a patient are possible.

This object is achieved according to the invention in that, in the device of the type mentioned at the outset, the injected liquid is uncooled, ie has room temperature, and the pump device is designed such that the liquid is injected continuously in a pulsating manner. With the device according to the invention, it is possible to continuously monitor the volume and the throughput in said circuit section and in particular the cardiac output and the circuit filling state, the measurements being able to be carried out fully automatically.

The device according to the invention has the particular advantage that, through the continuous supply of an uncooled measuring liquid, which is carried out in small doses per measuring process, solutions can be used as the measuring liquid which should or should be supplied to the patient anyway during treatment or hospitalization sen. In this way, simultaneous monitoring ensures that the solutions to be applied are supplied. This is not possible with the discontinuous measurement with high volumes of cooled injection liquid that has been customary until now.

The use of room-temperature-controlled ijectate means that there is no loss of cold to the surrounding air. The dead space volume to be taken into account is therefore reduced to the part of the control system located in the patient's body (0.1 ml to 0.2 ml). The cold is transported through the catheter wall to the surrounding blood so quickly that the injectate in the remaining dead space warms up to the blood temperature within a few seconds (time constant 2.5s). Since this, like the injection itself, leads to a cooling of the blood, there is no loss of cold associated therewith. The remaining cold loss, for example in the longitudinal direction of the catheter, is taken into account as usual via an empirical correction value. The error can be further reduced by weighting the correction value, which is dependent on the type of liquid and type of catheter, with the temperature difference between the injectate and blood. The lower amount of cold caused by the lower temperature difference between blood and injectate is compensated for by the negligible loss of cold. siert.

Particularly preferred refinements and developments of the device according to the invention are the subject of claims 2 to 11.

Particularly preferred exemplary embodiments of the device according to the invention are described in more detail below with reference to the accompanying drawing. Show it

1 is a schematic view of the assignment and connection of the liquid-carrying part of a first exemplary embodiment of the device according to the invention for the drive and evaluation device,

2 shows a longitudinal sectional view of the pump device with associated drive device in the embodiment shown in FIG. 1,

3 shows a cross-sectional view of the pump device with associated drive device according to FIG. 2,

4 shows a schematic illustration of the assignment and connection of the liquid-carrying part of a second exemplary embodiment of the device according to the invention for the drive and evaluation device,

FIG. 5 shows a longitudinal sectional view of the pump device with associated drive device in the exemplary embodiment shown in FIG. 4 and

6 shows a cross-sectional view of the pump device with associated drive device according to FIG. 5.

In the embodiment of the device according to the invention shown in FIG. 1, there is a supply of infusion liquid at room temperature in an infusion bag 1. The infusion bag 1 can be compressed by a suitable device, not shown, so that the overpressure generated thereby prevents air from penetrating .

A drip chamber 2, a pump device 3, an air sensor 4, a check valve 5 and an infusion liquid Speed temperature sensors 6 are releasably connected to one another and to the infusion bag 1 and a connection 9 of an injection device 12 (proximal lumen) via a hose system.

The pump device 3 can be constructed from elastically deformable parts and in particular comprises an elastically deformable tube or a hose 16. As is shown in particular in FIGS. 2 and 3, the tube 16 between a holder 54 and a cover 56 is one Drive device 21 arranged. The drive device 21 works in such a way that in the injection phase, the tube 16 is pressed and the liquid out of the tube 16 by a time-coordinated movement of a plurality of sliders 51, which are arranged to be movable in the axial direction of the tube 16 and against the tube 16 is pressed to the injection device 12 via the check valve 5, the air sensor 4 and the infusion temperature sensor 6. In the filling phase, the tube 16 is relieved of the slide 51, i.e. the slides 51 are withdrawn from the tube 16 so that it returns to its original shape. As a result, liquid flows from the infusion bag 1 into the tube 16 via the drip chamber 2. The slides 51 are moved by a drive motor 63 by means of springs 50, which prestress the sliders 51 in the direction of the tube 16, and cams 52 via a shaft 53 and a gear 57, 58, 59, 60.

In order to achieve a pulsed or burst-like injection of the infusion liquid, a high pressure is generated in the pump device 3 during the injection phase. This pressure is limited by the springs 50 to a value corresponding to the spring preload. The springs 50 cause energy storage during the filling phase, whereby the motor 63 is loaded evenly over time.

By suitably shaped contact surfaces of the holder 54, the cover 56 and the slide 51 of the drive device device 21 with the tube 16 such a deformation of the tube 16 is achieved that a secure closure of the tube 16 and a largely constant pressure curve during the injection phase is brought about. A convex / concave deformation of the tube 16, ie a lateral pushing in of the tube wall in the direction of the tube axis and the corresponding resetting, is particularly advantageous.

With the drip chamber 2, the infusion flow can be monitored both visually and via an evaluation and control device 20 which is connected to it. If there is air in the line system, this is recognized by the air sensor 4. The check valve 5 opens and closes depending on the direction of flow and allows the infusion liquid to flow from the infusion bag 1 only to the injection device 12. A backflow of blood from the circulation is thus prevented. The function of the check valve 5 can also be controlled by controlled valves, e.g. by suitably controlled slide 51 can be met.

The drive device 21 is controlled by the control and evaluation device 20, with which the drip on the he 2, the air sensor 4, the infusion temperature sensor 6 and the connection 10 of a blood temperature sensor 13 are connected, which is provided at the distal end of the injection device 12.

The injection device 12 with its connection 9 and the blood temperature sensor 13 are preferably installed in a catheter 11. A balloon 15 with a connector 8 facilitates the insertion of the catheter 11. The distal lumen 15 with the connector 7 is used for other tasks, e.g. available for pressure measurements.

The entire arrangement is designed without cooling devices and / or heat insulation devices, so that the injection liquid remains at room temperature and is injected at room temperature. To measure the cardiac output and circulatory filling condition, the catheter 11 is placed, for example, in the patient's venous blood circulation in such a way that the injection device 12 is located in the right atrium of the heart and the blood temperature sensor 13 at the distal end in the pulmonary artery. However, other arrangements and placements are also possible.

A cycle duration, an average infusion rate and an amount of injectate per cycle of, for example, 2 minutes, 90 ml per hour and 2 to 3 ml per cycle can be specified in the control and evaluation device 20. However, it is also possible to set the control and evaluation device 20 in such a way that the cycle duration is shortened to a minimum value which is dependent on the result of the evaluation. In order to avoid overinfusion of the patient, the user can specify a maximum permissible amount of infusion. This enables more precise monitoring of the patient if necessary.

An infusion consists of the phases of the slow filling of the pump device 16 and the rapid injection by the pump device 16. The injection leads to a change in the temperature lag at the blood temperature sensor 13. In connection with the injection time, this information is evaluated and Control unit 20 evaluated. The injection tongues are thus carried out automatically periodically or continuously pulsating, the cardiac output and the circulatory filling condition being determined and recorded for each injection.

The evaluation and control device 20 monitors the entire arrangement. If there is air in the system, one of the sensors fails or there is no more infusion liquid, a technical alarm is given and the next infusion is prevented. A medical alarm is triggered if the determined cardiac output or the circulatory filling status exceed or fall below the specified limit values given.

The second exemplary embodiment of the device according to the invention shown in FIGS. 4 to 6 differs from the first exemplary embodiment shown in FIGS. 1 to 3 in the design of the pump device. The pump device 31 in the second exemplary embodiment shown in FIGS. 4 to 6 comprises a piston 32 movable in a cylinder and is arranged in the manner shown in FIGS. 5 and 6 between a holder 77 and a cover 76 of the drive device 21. By pushing a slide 74, the piston 32 is pressed into the pump device 31 and the liquid is pumped out of the pump device 31 via a two-way valve 30, the air sensor 4 and the infusion temperature sensor 6 to the injection device 12. When the slide 74 is withdrawn, the piston 32 is pulled out of the pump device 31. As a result, liquid flows out of the infusion bag 1 via the drip chamber 2 and the two-way valve 30 into the pump device 31. The slide 74 is moved by means of a spindle 73 via a gear 71, 79, 80 by a motor 81.

The two-way valve 30 opens and closes depending on the flow direction. It only allows a flow from the infusion bag 1 to the pump device 31 and from the pump device 31 to the injection device 12. The function of the two-way valve 30 can also be fulfilled by controlled valves.

With the device according to the invention, the volume and throughput of a circulatory section, in particular the cardiac output, the right ventricular end-diastolic volume and the pre-pulmonary blood volume, can be measured and monitored almost continuously in short time intervals, for example at intervals of minutes, ie. By means of a corresponding statistical analysis of the mixed temperature curve, if necessary, not only can the cardiac output be calculated analogously to equation 2, but also the right-handed tricular end-diastolic ventricular volume RVEDV and the so-called prepulmonary blood volume PPBV are calculated, which represents the sum of the end-diastolic volumes on the right atrium (atrium) and ventricle (ventricle).

The RVEDV ventricular volume is calculated as the product of the cardiac output HZV and the time constant (tau) of the exponential drop in the mixing temperature curve:

RVEDV = HZV * dew

The blood volume PPBV is calculated as the product of the cardiac output HZV and the mean transit time MTT of the mixed temperature curve:

PPBV = HZV * MTT

The RVEDV and PPBV values are sensitive, reliable indicators of the circulating blood volume.

A standard intensive care patient receives at least about 20 ml / kg / 24h of crystalline solutions (sugar solutions, salt solutions) and solutions for parenteral nutrition as a basic infusion. In the device according to the invention, the basic infusion solution can be used as an indicator solution. With the above-mentioned minimum infusion rate of crystalline solutions, a body weight of 75 kg and an infusion volume of 3 ml per cycle enables at least 500 measuring cycles per day without additional need for injectate. This corresponds to a measuring cycle of 3 minutes. So far, a maximum of 20 injections per day were possible with a tolerable additional load on the patient of 200 ml of injectate per day (24 hours) and 10 ml of injectate volume per measurement. There is no special preparation and injection of the injectate for thermodilution measurement. The otherwise constant addition of basic infusion solution is only modulated accordingly, the modulation preferably being needle-shaped, but also being sinusoidal. The device according to the invention fulfills the tasks of an infusion device and a thermodilution injector. You administered the so far continuously administered solutions periodically as a bolus and evaluates changes in blood temperature that occur. All solutions to be administered intravenously are suitable for infusion, and there are no medical objections to their application as a bolus of small volume (a few ml). Such solutions are, for example, isotonic electrolyte solutions (saline, Ringer's solution), isotonic glucose solutions, isotonic nutrient solutions without added fat.

The device according to the invention therefore has the advantage in its use that no additional injectate is required for the measurement, the automatic operation makes work easier for the operators and the monitoring can take place almost continuously. The device can at the same time be used as an infusion device, wherein conventional pulmonary irrigation catheters can be used.

Claims

1. Device for determining the volume and / or the throughput of a circuit section of humans or animals with

- a fluid supply containing a fluid at a temperature different from the patient's blood temperature,

an injection device connected to the liquid supply via a pump device for injecting liquid from the liquid supply into the patient's circulation,

- A temperature sensor for measuring the temperature in the patient's circulation at a point in the flow direction behind the injection point and

- characterized by an evaluation device on which the measured values of the temperature sensor and further measurement parameters are located. that the injected liquid is uncooled, i.e. Has room temperature and the pump device (3, 31) is designed so that the liquid is injected continuously pulsating.

2. Device according to claim 1, characterized in that the pump device (3, 31) is controlled by the evaluation device (20) as a function of the completion of the measurement for the respective previous injection process.

3. Apparatus according to claim 2, characterized in that the pump device (3, 31) by the Auswerteinrich¬ device (20) is actuated so that a quantity of liquid dependent on the previous measurement is injected.

4. The device according to claim 1, characterized in that the pumping device (3, 31) is actuated at predetermined intervals.

5. The device according to claim 4, characterized in that the pumping device (3, 31) supplies a predetermined amount of liquid.

6. Device according to one of the preceding claims, characterized in that the pump device (3) is designed in the form of an elastically deformable tube (16).

7. The device according to claim 6, characterized in that the tube wall is convex / concave deformable with respect to the tube axis.

8. Device according to one of claims 1 to 5, da¬ characterized in that the pump device (31) is designed as a Kol¬ benzylinder arrangement.

9. Device according to one of the preceding claims, characterized in that the injection device (12) consists of a catheter (11) for insertion into the patient's circulation, at the distal end of which the temperature sensor (13) is provided and which at one Place in front of the distal end is provided with an opening for dispensing the liquid to be injected.

10. The device according to claim 6 or 1, characterized gekenn¬ characterized in that the pumping device (3) has a device (50) for pressure limitation.

11. The device according to claim 6, 7 or 10, characterized in that the pump device (3) with a one Direction for storing energy is provided during the relief stroke.