WO1993009715A1

WO1993009715A1 - Measurement cell for a monitoring appliance of a body fluid flowing out of a catheter

Info

Publication number: WO1993009715A1
Application number: PCT/EP1992/002562
Authority: WO
Inventors: Sigfried Hessberg
Original assignee: Sigfried Hessberg
Priority date: 1991-11-12
Filing date: 1992-11-08
Publication date: 1993-05-27
Also published as: AU2895292A; EP0612226A1

Abstract

An appliance for monitoring in sterile conditions the rate of flow of a body fluid flowing out of a catheter according to the principle of Pitot has a measurement cell (3) upon which the body fluid is applied from above through an inflow chamber (25). The measurement cell (3) has a measurement chamber (31) separated from the inflow chamber (25) by a partition (26), and a covering part (10) with two ventilation openings (28, 28a) closed by bacteria-proof filters (110, 111) by means of which the measurement chamber (4) and the inflow chamber (25) are ventilated. The measurement cell (3) further contains a Pitot tube (43) that may be connected by a connecting pipe (39) to a pressure gauge (2). The Pitot tube (43) is also sealed by a bacteria-proof filter (60) with respect to the connecting pipe (39). Wetting of the bacteria-proof filters (60, 110) by the liquid to be measured is prevented by the liquid barriers (101, 105) arranged within the central part (9) of the measurement chamber (4) or at the lower end of the Pitot tube (43).

Description

MEASURING CELL FOR A DEVICE FOR MONITORING

BODY LIQUID LEAKING FROM A CATHETER

The invention relates to a measuring cell for a device for monitoring body fluid emerging from a catheter, in which the body fluid is collected using a measuring chamber and the filling volume of the measuring chamber is determined by means of a dynamic pressure measurement.

A device for measuring the urinary flow of patients is known from DE-A-39 33 025, with two parts which can be separated from one another, the measuring head and a collecting container which can be screwed on underneath and has a riser pipe attached to the side.

The measuring head contains an inlet funnel which opens into a vertical inlet space. Which in turn is connected via a collecting bowl both to a pressure measuring chamber and to a slotted pitot tube from which the urine can either flow into the toilet or into the collecting container. The pressure measuring space is directly connected to a pressure sensor, which measures the accumulation height in the inlet space via the air column in the pressure measuring space. The instantaneous damming height is determined by the urine inflow and the flow behavior of the urine through the slotted pitot tube. The outflow speed and thus the flow volume can be calculated using the slot width via the damming height above the outflow jet.

Furthermore, it is provided to measure the filling level of the urine in the collecting container via the pressure of the air column in the riser pipe, which is also connected to a pressure sensor. The known device has the disadvantage that the pressure measurement is sensitive to an inclined position of the measuring device or to the liquid movement within the measuring device and retrograde germ growth is not prevented. The measurement of the flow rate over a slotted tube also has the disadvantage that sediments and Koagel, which are very likely to occur in the patient's urine, immediately falsify the measurement accuracy.

US Pat. No. 4,554,687 also describes a measuring device for determining the urine flow, which works on the dynamic pressure principle. The device is installed in a toilet and has no collecting container for determining the total volume.

US-A-4,683,748 discloses a method and a device for measuring flow rates of body fluids. The device consists of a central chamber with an elliptical cross-section, into which the body fluid enters through an inlet hose.

At the opposite ends of the main cross-sectional axis of the central chamber, two tube-like areas are separated from the main chamber by internals. The two partitions end at different heights above the chamber floor, so that both areas are open at the bottom and can communicate with the main chamber.

The area with the lower-lying liquid inlet opening functions as a riser pipe and is directly connected to a pressure sensor at its upper end.

The pressure of the gas column above the liquid level above the riser pipe is therefore a measure of the liquid level in the main chamber. The second area ends in an outlet opening which is connected to a discharge hose. In this way, the chamber is automatically up to when the liquid level has reached the height of this outlet opening

emptied at a level at the level of the liquid inlet opening of the second region.

This means that a safe liquid level measurement is not guaranteed when the measuring device is moved. In addition, measuring liquid which is in contact with the outside world can get into the liquid inlet tube connected to the catheter when the device is moved and the liquid spills, which can lead to retrograde germ migration.

DE-A-3106 488 describes a drip chamber in a drainage system for body secretions, in particular urine, with a substantially rigid housing, the lower outlet of which is connected via a valve to a collecting bag or a measuring container and the upper inlet of which consists of a drip tube, which is connected to a body secretion drain.

The valve chamber has an opening on the front covered with a bacteria-proof filter for ventilation of the chamber.

In order to keep the tip of the drip tube free of contamination, it is provided that an inner annular space is formed on the vertical part of the wall of the housing, which is closed at the top and open at the bottom. The outer wall of the annular space advantageously consists of the wall of the housing, while the inner wall of the annular space is formed from a rigid sleeve, the upper end of which is fluid-tightly connected to the wall of the housing. The annular space forms a pocket that is closed at the top and open at the bottom, into which a sloping or horizontal drip the remaining amount of the flowing body secretion runs in, so that it is caught in the wall area of the drip chamber housing and is prevented from penetrating to the tip of the drip tube and the drip chamber is free of contamination over a longer period of time.

Although this drip chamber prevents retrograde germ migration, it has the disadvantage that the filter of the valve chamber e.g. during movements of the device and sloshing of the measuring liquid can be wetted by the measuring liquid and its functionality can thereby be impaired. This can go so far that either the filter becomes completely impermeable, which means that it is no longer possible to empty the chamber when the inlet is closed, or it becomes permeable to germs.

It is an object of the present invention to further develop a device of the type mentioned at the outset such that, with a structurally simple design, high measurement accuracy is ensured while avoiding the disadvantages of the prior art described and while complying with the necessary hygienic requirements in medical technology.

This object is achieved by a measuring cell for a device for monitoring body fluid emerging from a catheter with a measuring chamber which receives the body fluid from above with a cylindrical or polygonal rectangular prismatic central part, a base part, with a cover part and a pitot tube arranged in the central part, the extends from above through the cover part to a little above the bottom of the measuring chamber and at the upper end of which a pressure sensor can be connected via a connecting line, characterized in that the cover part and base part each have a connecting piece with a lockable inlet hose connected to it or drain hose is provided, in the upper part of the measuring chamber the measuring chamber from an inlet chamber through a continuous lateral intermediate wall and a floor is separated, the upper connecting piece opens into a drip pipe which projects into the inlet chamber, the end of the drip pipe being at a sufficient distance from the bottom of the inlet chamber to form a drip section, in the bottom deep ¬ most area is an opening closed by a check valve opposite the measuring chamber, as a liquid passage from the inlet chamber into the measuring chamber and there are two ventilation openings in the cover part, each with a bacteria-proof filter, through which the measuring chamber and the inlet chamber are ventilated, that Pitot tube is arranged centrally or slightly offset from the center in the measuring chamber and a bacteria-tight filter is arranged at the upper end of the pitot tube in the cover part of the measuring chamber, which seals the pitot tube against the connecting line and that a liquid barrier within the central part of the measuring chamber is arranged t, the upper web engages in a groove of the cover part, which delimits the ventilation opening to the inside, and which slopes away at an angle to the side wall of the measuring chamber and runs into an intermediate wall running parallel to this side wall and at a short distance therefrom, which extends almost to the extends lower edge of the middle part, the side flanks of the liquid barrier terminating in one with the side wall of the middle part running parallel to the intermediate wall and with the intermediate wall, and in that a liquid barrier with two intermediate floors in the form of circular segments is integrated at a slight distance from the lower end of the pitot tube is, the intermediate floors in the pitot tube are arranged at a short distance from one another so that the remaining openings are diagonally to one another.

In principle, the measuring cell according to the invention contains a lockable liquid inlet, an inlet chamber, the actual measuring chamber separated from the inlet chamber by a valve system, and a likewise lockable liquid outlet. The closed design of the measuring chamber within the measuring chamber and its separation from a closed inlet chamber result in particular advantages when using the measuring cell to determine the outflow quantities of body fluid such as urine, hemofiltrate, wound secretion, blood plasma, dialysis fluid etc. and for volume-controlled purposes Bladder irrigation.

In the measuring chamber, a riser pipe open at the bottom is arranged centrally or slightly offset from the center, at the upper ends of which a pressure sensor can be connected via a connecting line.

The hydrostatic pressure in the measuring cell is transmitted to the air column in the pitot tube and acts on the pressure cell via the connecting line. Since this is a closed system, the measuring liquid penetrates the pitot tube only minimally.

In order to allow the formation of a level of body fluid in the measuring space, the drain hose is designed to be lockable below the bottom part. The inlet hose is also preferably designed to be lockable above the cover part. The shut-off is preferably carried out by clamping the hose with the formation of hose clamp valves.

For reasons of sterility, a bacteria-proof filter is arranged at the upper end of the pitot tube in the cover part of the measuring chamber, so that the pitot tube seals against the connecting line.

The connecting line opens into a Luer-Lock connection according to DIN 13090, via which the pressure cell can be connected in a gas-tight manner. A manometer protection filter is preferably interposed between the Luer lock connection and the pressure sensor, while a second connection of the pressure sensor leads to the outside. This ensures that the pressure measurements for determining the liquid level are carried out independently of the air pressure.

In order to achieve the highest possible measuring accuracy, the gas volume between the liquid level in the pitot tube and the pressure cell is kept as small as possible.

The measuring chamber can have a circular or polygonal cross-section, the pitot tube being arranged centrally or slightly offset from the center in the measuring chamber in order to ensure the highest possible measuring accuracy even when the measuring device is tilted or in the case of liquid movements.

The diameter of the pitot tube can be freely selected for this measuring principle, but riser tubes with an inner diameter between 8 mm and 16 mm are preferably used.

In order to avoid deposits from the body fluid while the measuring cell is in use on the inside of the riser tube, it is advantageous to provide the inside of the pitot tube with an anti-adhesive layer.

Suitable anti-adhesive layer is heparin, urease or polyorganosiloxane bonded to the inner surface of the riser pipe.

The pitot tube is made of plastic, preferably of an injection-moldable thermoplastic.

The inlet chamber forms a so-called Pasteurian chamber, with a drip section for incoming body fluid and a check valve between the Pasteurian chamber and the actual measuring chamber and prevents it The measuring liquid runs back from the measuring chamber or Pasteurian chamber into the catheter connected to the patient even when the device is at an extreme incline and thus prevents the transmission of germs of the measuring liquid from the measuring chamber, which is there in connection with the outside world, to the patient. The retrograde germ migration is additionally prevented by the fact that the ventilation opening of the Pasteurian chamber arranged in the cover part is provided with a bacteria-proof filter.

If the measuring cell is inserted into the part of the device containing the measuring and evaluation electronics, the device and accordingly the measuring cell can only be tilted in one direction perpendicular to the main surface of the device when the device is used as intended. Such tilting of the device is e.g. possible if the entire device, e.g. when transferring the patient or cleaning the floor, is removed from its suspension on the bed and placed on the patient's bed.

It is possible to tilt the device in the angular ranges between 0 ° and 120 ° and between 0 ° and -30 °, with respect to the vertical. Tilting of the device in a smaller negative angular range (0 ° to -30 °) occurs e.g. when the patient is transported in his bed with the device connected and the entire device in his hanging device on the bed executes a pivoting movement in the direction under the bed in order to avoid obstacles, e.g. Door frame to dodge.

In order to ensure the functional reliability of the measuring cell and to effectively prevent retrograde germ migration, it must be prevented that both the filter of the ventilation opening of the inlet chamber and the filter of the ventilation of the measuring chamber as well as the filter between the pitot tube and the connecting line from the measuring liquid itself the sloping positions described above is wetted. To achieve this, a liquid barrier is arranged on the one hand within the middle part of the measuring chamber, the upper web of which engages in a groove of the cover part, which delimits the ventilation opening to the inside, and which falls obliquely towards the side wall of the measuring chamber and into one parallel to the latter Side wall and at a short distance from it runs out intermediate wall, which extends almost to the lower edge of the central part, the side flanks of the liquid barrier terminating on the one hand with the parallel side wall of the central part and with the intermediate wall.

The liquid barrier creates a further space within the measuring chamber, which extends between the inlet chamber and the opposite side wall of the measuring chamber and in the upper area covers the entire ventilation opening closed with a bacteria-proof filter. The part of the liquid barrier arranged parallel to the front wall of the measuring chamber can be at a distance from the front wall in the range between 2 and 10 mm.

To prevent penetration of the measuring liquid into the pitot tube and thus the wetting of the bacteria-proof filter between the pitot tube and the connecting line, a further liquid barrier with two intermediate floors in the form of circular segments is integrated at a slight distance from the lower end of the pitot tube, the intermediate floors in the riser pipe are arranged at a short distance from each other so that the remaining openings face each other. The distance between the two intermediate floors can be 4 to 8 mm.

This design of the measuring cell ensures the high hygienic standard and the high level of operational safety that must be required in the clinical use of such a device. A preferred embodiment of the present invention additionally takes into account the approval requirement for medical devices in many countries that an additional control function for monitoring the correct operation of the device must be present in order to ensure a redundant security system.

This is achieved in that the measuring cell has an active area which is transparent to the radiation used and has a light reflection surface forming the inner wall and an outer wall provided with an even number of serrated recesses, the outer side flanks of the recesses having an angle α with a perpendicular one take a straight line on the reflecting surface and the opening angle of the serrated recesses is 90 ° and the device part containing the measuring and evaluation electronics has a light transmitter and a light receiver, which are adjusted so that when the measuring cell is inserted, the emitted light beam is perpendicular to the reflecting surface is at an angle α and the beam reflected at the same angle α strikes the receiver, the angle α being derived from the equation

= sin ^" (1 / n) + k

in which n is the refractive index of the material used for the area and k can have a numerical value between 0.75 and 2.5.

The safety device follows the principle that the increase in the measuring liquid in the measuring chamber must result in a measuring signal and vice versa, that a measuring signal may only be present if a minimum amount of the liquid is also present. Therefore, in addition to one of the three measured value acquisition units described above, an optical qualitative level control is installed in the measuring device integrated, with which it can be determined whether a minimum amount of measuring liquid is present or not. The present safety device therefore serves firstly to check whether the nursing staff has correctly connected the measuring line from the measuring cell to the evaluating electronic unit. Once this has been done, another double function has come into force.

The pressure sensor controls the optics and the optics controls the pressure sensor, since in the safety-related considerations regarding the Med.GV the testing authority assumes that not both fail simultaneously. The optical fill level control is based on the fact that a light beam is directed at a certain angle onto a specially designed, optically active area of the measuring cell. If there is no liquid in the measuring cell, the beam is reflected on a surface and received by a receiver which generates a corresponding measuring signal.

This measuring principle is based on the reflection of a light beam at the interface between two media with different refractive indices n.

It applies to the critical angle of total reflection at an interface

sin α = n '/ n ε Here (see FIG. 8) a mean the critical angle of the total reflection, n the refractive index of the optically denser medium and n' the refractive index of the optically thinner medium. The angle of reflection of the reflected light beam is equal to the angle of incidence of the incident light beam. If, for example, a light beam strikes the interface between a body made of acrylic-butadiene-styrene-co- polymer (n = 1, 54) and air (n ¹ = 1), result for the limit angle of the total refl exi on

sin a = 1/1, 54 α = 40, 49 'ε ε

This means that a light beam that is irradiated at this critical angle with respect to a straight line perpendicular to the plane of reflection is completely reflected at the same angle and can be received by a detector.

Since it is a critical angle, the radiation must be somewhat flatter in order to achieve a reliable total reflection. Therefore, a numerical value k in the range between 0.75 ° and 2.5 °, preferably approximately 1.5 °, should be added to the calculated critical angle. A radiation angle which is optimal for the present example in order to achieve total reflection at the interface between ABS polymer and air is thus 42 °.

If the optically thinner medium air is now replaced by another optically thinner medium, e.g. Water, which agrees with urine to a good approximation (n "= 1.33), also results in a changed critical angle for total reflection. It applies

sin ~ 1.33 / 1.54 α = 59.73 ° ε

It follows that the conditions of total reflection are no longer met at an angle of incidence of 42 ° and the beam is no longer reflected, but is deflected at an angle α '(see FIG. 8).

The following applies to α *:

n sinα = n "sinα ';sinα:' = n sinα / n '' = = 1.54 sin (42 °) / l, 33 '~ 59.73 ° From these considerations it follows that a light beam that is at an angle

-1 α = sin (1 / n) + k,

where n and k have the meaning as described above, is irradiated onto the interface between an optically dense medium and an optically thinner medium, is completely reflected when the optically thinner medium is air with the refractive index n equal to 1 and is refracted when that optically thinner medium, for example: water or urine. The choice of the angle of incidence therefore essentially depends on the optically denser medium used.

To implement this measuring principle, the present device for the optical fill level control of the measuring cell has the following structure:

The measuring cell preferably has, at a short distance from the floor, an optically active region which is transparent to the radiation used and has a light reflection surface which forms the inner wall. In addition, the device part containing the measuring and evaluation electronics is provided with a window in the housing wall which, when the measuring cell is inserted, is arranged parallel to the optically active area and has a light transmitter and a light receiver which are adjusted in such a way that the emitted light beam takes an angle a with a straight line perpendicular to the reflection surface and the light beam reflected at the same angle α strikes the receiver, the angle α being derived from the equation

α = sin ^" (1 / n) + k

in which n is the refractive index of the material used for the above-mentioned range and k is one U

Numerical value between 0.75 and 2.5, preferably 1.5.

So that there is no loss of intensity due to reflection when the light beam strikes the outer wall of the abovementioned area of the measuring cell, this outer wall has an even number of jagged recesses, the angle of the outer side flanks of the recesses being perpendicular to the Reflecting surface standing straight line corresponds to the above-mentioned reflection angle α. The opening angle of the serrated recesses is 90 °. From this geometrical construction it follows that the respective inner side flanks of the recesses enclose an angle of 90 - α with the straight line perpendicular to the reflecting surface and the entire construction with respect to a surface perpendicular to the reflecting surface which passes through the top of the middle jagged elevation runs, is mirror symmetrical. In this way it is ensured that both the incoming light beam and the outgoing light beam basically enter or exit perpendicular to the outer wall of said measuring cell area. This avoids loss of intensity due to undesired reflection on the outer wall. The wall thickness of said measuring cell area, measured between the deepest point of one of the jagged recesses and the reflection surface, can be between 0.5 and 4 mm. With larger wall thicknesses, an optical path correction is necessary. The number of serrations is generally not critical. It results from the dimensions of the optically active area, which in a preferred embodiment has a width of 6-25 mm with 2 to 8 recesses.

The wavelength of the light used can be either in the infrared or in the visible range. Since the refractive index depends on the wavelength, the value be corrected according to the wavelength used. An LED diode is preferably used as the transmitter and a photodiode or a phototransistor is used as the receiver, which emits or receives in the visible range of the light. The transmitter and receiver are preferably arranged at a distance between 1 and 2 cm from the optically active area when the measuring cell is inserted, and the transmitter has an angle of divergence of the emitted beam between 4 and 12 °.

The entire measuring cell, including the optically active area, is preferably made of the same material as e.g. Acrylic butadiene styrene copolymer or polymethyl ethacrylate manufactured. In principle, however, the optically active area and the rest of the measuring cell can also be made of different materials.

The functionality of the optical level control can be described as follows:

When the measuring cell is inserted and the measuring device is switched on, the emitted light beam enters perpendicular to the outer wall of the optically active area of the measuring cell and is reflected at the reflection surface at the angle α if the measuring cell is not filled with measuring liquid. The intensity of the reflected beam is registered by the receiver and converted into an electronic signal. If the measuring cell now fills with the liquid to be measured, for example urine, air is displaced by the measuring liquid in the optically active area of the measuring cell, as a result of which the reflection critical angle changes and the emitted beam no longer reflects but is deflected into the inside of the measuring cell becomes. In this case, the receiver can no longer determine the light intensity and forwards a corresponding signal to the evaluation unit. The measurement signal of the measurement value acquisition unit is now compared with the signal of the optical fill level control. Are both signals correct in their qualitative do not agree, there must be an operating or device error and an alarm is triggered.

The invention also includes a method for the continuous monitoring of liquid emerging from a catheter, in particular urine and other body fluids, using the measuring cell according to the invention and a measuring and control device with integrated pressure measuring cell connected to the measuring cell.

To carry out the method, the riser pipe is brought into a gas-tight connection with the pressure cell.

The body fluid enters the inlet chamber via a drip line and from there into the measuring chamber with the drain hose shut off, and penetrates minimally into the riser pipe, the temporal pressure change in the gas space between the liquid level in the riser pipe and the pressure cell depending on the filling was measured in the measuring chamber and thereby the filling volume of the measuring chamber at certain times and the flow volume per unit time of body fluid is determined. The measuring chamber is emptied periodically when the inlet hose is shut off by briefly opening the outlet hose.

The pressure above the liquid level in the riser pipe is measured in a time interval controlled by a microprocessor from 10 milliseconds to 1 minute. Flow volumes in the range of 5 ml per hour and 500 ml per hour can be determined with sufficient accuracy. If a critical minimum flow rate is undershot or a maximum flow rate is exceeded, the device triggers an alarm. After completion of the measurement, the measuring liquid is passed with the inlet valve closed through the outlet valve opened for this purpose and a nozzle into the collecting bag. By automatically controlling the inlet and outlet valves, exactly predetermined measuring intervals can be maintained, the duration of the measuring interval being determined both by a maximum volume and by a maximum measuring duration. The measuring chamber is emptied when the maximum volume is reached, preferably 10 to 500 ml. For this purpose and with a short time offset, the inlet valve is first closed and then the outlet valve is opened. In order to equalize the pressure, air is passed through the bacteria-tight filter in the Pasteurian chamber and in the lid into the measuring chamber, thereby preventing germs from entering the measuring chamber. The drain valve remains open for 5 to 10 seconds so that remnants of the measuring liquid can flow off the walls. Then the drain valve is first closed and then the feed valve is opened at the beginning of a further measuring interval.

If the minimum measurement volume (specified by doctors or nursing staff) is not reached within the specified measurement period of preferably 1 hour, the device issues an alarm.

An optical display prompts the nursing staff to check the correct position of the upper and lower pinch valve, since the incorrect valve position can also be the cause of an insufficient measurement volume.

If the valve position is correct, the nursing staff can carry out other tests, for example checking the continuity of the supply lines in front of the measuring chamber. After eliminating any errors, the emptying of the measuring chamber is activated as described above and a new measuring cycle is initiated. In the preferred embodiment, the mode of operation of the measuring device is additionally monitored by the device for optical fill level control described above. The electronic control and measurement data processing of the liquid measurement enables a special data storage. For example, the entire measuring interval is preferably divided into 5-minute intervals and the associated fill volume of three successive 5-minute intervals is stored. The memory content is updated every 5 minutes by deleting the oldest and entering the most recent measured value. This means that there are always adapted measurement volume values from the last 15-minute interval available, which are converted to flow volumes per hour. This opens up the possibility for the attending physician to quickly and reliably check the effect of an administered medication without having to wait for an hourly measurement which does not emphasize the result so clearly.

Another aspect of the present invention is to provide a device of the type mentioned, in which the body fluid supply hose, the measuring cell, the hose connection from the riser pipe to the Luer lock connection with sterile filter, the drain hose and the collecting bag as Disposable items are designed, whereby the measuring cell can be easily installed in the measuring device and the hose connection can be easily connected via the Luer-Lock connection to the pressure sensor located in the housing of the measuring device.

It has proven to be particularly advantageous to assemble the measuring cell made of plastic together with the hose connection with sterile filter and Luer lock connection as well as a collection bag possibly connected to the measuring cell as a disposable article and to put it on the market in sterile condition . The measuring and control device and the pressure transducer with manometer protection filter can be used many times over the long term together with the measuring cell intended for single use. The measuring cell is expediently fixed by inserting guide ribs arranged on the measuring cell into a recess provided in the housing, so that it can be easily replaced.

The present invention is preferably used for monitoring the flow of urine or other body fluids of a patient, the monitoring duration being up to two weeks. It follows from this that the measurement must be carried out with constant accuracy within this period.

The device is advantageously designed as a mobile system, so that the patient connected to it can move largely unhindered, for example in order to undergo further clinical examinations.

Further features of the invention are described in the description of the figures and in the subclaims.

The preferred embodiment of the present innovation will now be explained in more detail with reference to figures.

FIG. 1 shows the measuring cell in longitudinal section and the measuring device with a view of the main surface of the measuring device. The axes of the Luer lock connection of the manometer protection filter and the pressure transducer are placed in the image plane to simplify the illustration.

FIG. 2 shows the measuring cell in detail with the same orientation as in FIG. 1.

FIG. 3 shows the measuring cell rotated by 90 ° in longitudinal section compared to the illustration in FIG. 2. Figure 4 shows the measuring cell tilted by 120 ° or -30 ° from the vertical.

FIG. 5 shows the measuring cell in cross section along the line A-A of FIG. 2.

Figure 6 shows the optical active area of the measuring cell in detail.

FIG. 7 shows a schematic representation of the device parts designed as disposable items.

Figure 8 shows schematically the measuring principle of the light reflection surface.

In FIG. 1, the device part containing the measuring and evaluation electronics is denoted by 1 and the measuring cell by 3. It is clear from this illustration that when the measuring cell 3 is pushed into the device part 1, the two liquid barriers 101 are arranged parallel and 105 perpendicular to the main surface of the device and thus when the measuring cell 3 is tilted about the pivot points A and L (FIGS. 2 and 2) 3) Prevent the sterile filter from wetting.

43 also designates the pitot tube, 202 the optically active area and 6 and 8 the inlet hose or outlet hose of the measuring cell 3.

The connecting hose 39 is connected gas-tight to the pressure cell 2 via a Luer-Lock connection 61 according to DIN 13090. In order to prevent germs entering the measuring cell 3 from the side of the pressure cell 2, the sterile filter 60 is arranged between the pitot tube 43 and the transition piece 38. To protect the pressure cell 2 from the penetration of the spray disinfectant solution, a pressure gauge filter 62 is installed between the Luer lock connection 61 and the pressure cell 2.

To install the disposable item, the urine collection bag (not shown) is pushed onto a mandrel (not shown) under the device housing 1.

The measuring cell 3 with the guide ribs 67 is now inserted into the recess 68 on the device housing 1.

At the same time, the supply hose 6 and the discharge hose 8 slip into the hose clamps 15 and 16. Finally, the connecting hose 39 is connected to the pressure measuring probe 2 with the aid of the Luer lock connection 61. This ensures simple and reliable replacement of the disposable article.

Before the measuring cell 3 is put into operation, the lower hose clamp 16 is closed by actuating the pull rod 21. The pull rod 21 is moved by an electromotive drive unit, not shown. The hose clamp 15 of the upper connecting piece 5 is open in measuring operation and is closed by moving the pull rod 19 with the aid of an electromotive drive (not shown). When the inlet hose 6 is open and the outlet hose 8 is closed, urine drips through the inlet hose 6 into the inlet chamber 25 and from there through the opening 29 into the measuring chamber 4 or the measuring chamber 31.

As illustrated in FIG. 2, the measuring cell 3 has a rectangular prismatic measuring chamber 4, which is made up of a central part 9, a bottom part 11 with a lower connecting piece 7 and a cover part 10 with an upper connecting piece 5. In the upper part of the measuring chamber 4, the measuring chamber 31 is from an inlet chamber 25 through a continuous side partition 26 and a bottom 26a separated. The upper connection piece 5 opens into a drip tube 27, which protrudes into the ^"inlet chamber 25, it being possible for the end of the drop tube 27 has a sufficient for the formation ei¬ ner drip path distance from the bottom 26a of the inlet chamber 25th

In the bottom 26a of the inlet chamber there is an opening 29, closed by a valve flap 30 opposite the measuring chamber 31, as a liquid passage from the inlet chamber 25 into the measuring chamber 31. In the cover part 10, a ventilation opening 28 is provided in the area of the measuring space * 31 and a ventilation opening 28a is provided in the area of the inlet chamber 25, both of which are each provided with a bacteria-proof filter (see FIGS. 3, 110 and 111).

The ventilation openings and the filters are protected against the ingress of liquids from above by a roof (112).

The measuring chamber 4 passes through a pitot tube 43 with a diameter of 8 mm made of plastic, which opens into the cover part 10. The pitot tube 43 is open at the bottom so that it can communicate with the measuring chamber 4. At the level of the cover part 10, the pitot tube 43 is connected gas-tight with the aid of a transition piece 38 to a connecting hose (not shown) made of PVC with a diameter of 2 to 4 mm, which leads to the pressure sensor installed in the device housing 1.

In this way a self-contained gas space is created, which means that the liquid level within the pitot tube 43 rises only slightly, even when the measuring chamber is full.

In the cover part, a bacteria-proof filter 60 is inserted below the transition piece 38, which closes the pitot tube 43 in a bacteria-proof manner from the outside world. In addition, the measuring cell 3 has two guide ribs 67 in the area of the connection point between the middle part 9 and the bottom part 11 of the measuring chamber 4, which lead out into a handle on the front side of the measuring cell 3 (see FIG. 3).

In the lower area of the base part (11) of the measuring chamber, an optically active area (202) is provided on the side facing the housing 1 when the measuring cell (3) is installed.

As can be seen particularly well from FIG. 3, a liquid barrier 101 is arranged within the middle part 9 of the measuring chamber 4, the upper web 102 of which engages in a groove 103 of the cover part 10, which delimits the ventilation opening 28 to the inside, and which is inclined to the side wall of the Measuring chamber 4 drops out and runs out into an intermediate wall 104 running parallel to this side wall and at a short distance therefrom, which extends almost to the lower edge of the middle part 9. As can be seen particularly well from FIG. 2, the side flanks of the liquid barrier 101 close off on the one hand with the side wall of the middle part 9 running parallel to the intermediate wall 26 and with the intermediate wall 26.

In this way, a defined space is created below the ventilation opening 28, into which no liquid enters, even when the measuring cell is tilted and shaken.

The prerequisite for this is that the maximum fill level of the

Measuring chamber 4 must not be higher than the lower end of the intermediate wall 104.

Furthermore, the arrangement of the second liquid barrier 105 can be clearly seen in FIG. It consists of two intermediate floors 106, 107 in the form of circular segments, which are arranged within the riser pipe 43 at a short distance from one another so that the remaining openings 108, 109 face each other.

It is clear from the illustration shown in FIG. 4 that when the measuring cell is tilted about the pivot point A or the pivot point L in the specified angular range of -30 ° to -120 °, no measuring liquid (M) the bacteria-tight filter (60, 110) can wet.

As can be seen from FIG. 5, the optically active area 202 of the measuring cell is arranged parallel to a window 210 in the housing wall 212 of the device part 1 containing the measuring and evaluation electronics when the measuring cell 3 is inserted into the device 1. The transparent optically active area 202 of the measuring cell 3 is provided with a light reflection surface 203 forming the inner wall and with an even number of jagged recesses 204 which form the outer wall. The light transmitter 208 is adjusted so that the emitted light beam enters the wall perpendicular to the inner flanks of the recesses 204 and is reflected at the reflection surface 203 at an angle α if there is no measuring liquid in the measuring cell, again passes perpendicularly through the outer wall and is registered by the receiver 209. The measuring principle should also be protected when transmitter 208 and receiver 209 are interchanged.

As can be seen in FIG. 6, the outer side flanks 206 of the recesses 204 enclose an angle which corresponds to the reflection angle α with a straight line perpendicular to the reflection surface 203. The opening angle of the serrated recess 204 is 90 °. The result of this geometric arrangement is that the optically active region 202 is mirror-like with respect to a plane perpendicular to the reflection surface 203, which runs through the tip of the central jagged elevation 207. 2 6 is symmetrical. The part of the optically active area 202 which extends into the interior of the measuring cell 3 is preferably designed as a truncated cone with an opening angle of 90 °.

In the exemplary embodiment shown in FIG. 6, the entire measuring cell consists of acrylic-butadiene-styrene copoly, resulting in a reflection angle α of 42 °.

In Figure 7, the parts of the disposable article labeled C are shown again schematically.

The measuring cell 3 has an inlet chamber 25 and the measuring chamber 31. The upper connection piece is designated by 5, followed by the inlet also 6, the end of which is provided with a conical connection element 40 with a urine withdrawal point.

At the lower connecting piece 7, the drain hose 8 is connected, which opens into the collecting bag 41. For emptying, the collection bag 41 is provided with a drain tap 42.

A sterile filter 60 is arranged below the transition piece 38. The connecting line 39 to the pressure transducer, not shown, has a Luer lock connecting piece at the end, preferably the final part of a Luer connection.

In FIG. 8 the reflection surface is designated by 203 and the optically active area of the measuring cell is designated by 202, n is the refractive index of the optically denser medium and n 'that of the optically thinner medium, n' ¹ is the refractive index of the liquid to be measured , for example urine, αg is the critical angle of total reflection, a 'reflective angle of the deflected beam, αr is the reflected critical angle. The functional relationship is described in more detail in the description when the functionality of the safety device is explained. 2S

B E Z U G S Z E I C H E N L I S T E

1 housing

2 pressure cell

M measuring liquid

3 measuring cell 4 measuring chamber

5 upper connecting pieces

6 urine inlet hose

7 lower connecting piece

8 urine drain hose 9 middle section

10 cover part

11 bottom part

15 upper hose clamp

16 lower hose clamp 19 pull rod

21 tie rod

25 inlet chamber

26 partition

26a bottom of the inlet baffle 27 drip pipe

28 vents 28a vents

29 opening

30 valve plate 31 measuring chamber

37 Luer lock connector (female)

38 transition piece

39 connecting line

40 cone with urine collection point 41 urine collection bag

42 drain cock

43 Pitot tube 60 sterile filters

61 Luer lock connection

62 Pressure gauge protection filter 67 Guide ribs

68 recess

100 measured value acquisition unit lθi liquid barrier

102 upper web 103 groove

104 partition

105 liquid barrier

106 shelves

107 intermediate floors 108 openings

109 openings

110 filters

111 filters

112 roof 202 optically active area

203 reflective surface

204 serrated recess

205 outer wall

206 outer side flanks 207 jagged elevation

208 light transmitter

209 light receiver

210 windows 212 housing wall

Claims

«PATENT REQUESTS

1. Measuring cell (3) for a device for monitoring body fluid emerging from a catheter with a measuring chamber (4) receiving the body fluid from above with a cylindrical or polygonal rectangular prismatic middle part (9), a bottom part (11), with a Cover part (10) and a pitot tube (43) arranged in the middle part (9), which extends from above through the cover part (10) to somewhat above the bottom of the measuring chamber (4) and at the upper end of which a Ver ¬ connection line (39) a pressure sensor (2) can be connected, characterized in that the cover part (10) and bottom part (11) each have a connecting piece (5, 7) with an attached lockable inlet hose (6) or outlet hose ( 8) is provided, in the upper part of the measuring chamber (4) the measuring chamber (31) is separated from an inlet chamber (25) by a continuous side partition (26) and a bottom (26a), the upper connecting piece s (5) opens into a drip pipe (27) which projects into the inlet chamber (25), the end of the drip pipe (27) being a sufficient distance from the bottom (26a) of the inlet chamber to form a drip section (25) has in the bottom (26a) in the deepest area an opening which is closed by a check valve (30) with respect to the measuring chamber (4)

(29), as a liquid passage from the inlet chamber (25) into the measuring chamber (31) and in the cover part (10) two ventilation openings (28, 28a) closed with a bacteria-proof filter (110, 111), via which the measuring chamber (4) and the inlet baffle (25) are ventilated, are present, the pitot tube (43) is arranged centrally or slightly offset from the center in the measuring chamber (4). net and at the upper end of the pitot tube (43) in the cover part (10) of the measuring chamber (4) a bacteria-tight filter (60) is arranged, which seals the baffle tube (43) against the connecting line (39) and that a liquid barrier (101) is arranged within the middle part (9) of the measuring chamber (4), the upper web (102) of which engages in a groove (103) of the cover part (10) which delimits the ventilation opening (28) towards the inside and which slopes diagonally to the front wall of the measuring chamber (4) and ends in an intermediate wall (104) running parallel to this front wall and at a short distance therefrom, which extends almost to the lower edge of the central part (9), the lateral ones Flanks of the liquid barrier (101) to one with the side wall of the central part (9) running parallel to the intermediate wall (26) and with the intermediate wall (26) and that a liquid barrier (105) at a slight distance from the lower end of the pitot tube (43) ) with z White intermediate floors (106, 107) in the form of circular segments are integrated, the intermediate floors (106, 107) being arranged in the pitot tube at a short distance from one another in such a way that the remaining openings (108, 109) are diagonal to one another .

2. Measuring cell (3) according to claim 1, characterized in that the connecting line (39) is provided with a Luer lock connection (61) according to DIN 13090 for connecting the connecting line (39) to the pressure cell (2).

3. Measuring cell (3) according to claim 2, so that the pitot tube (43) has an inner diameter in the range between 8 and 16 mm.

4. Measuring cell (3) according to claim 3, so that the pitot tube (43) is provided with an anti-adhesive layer of heparin, urease or polyorganosiloxane bonded to the inner surface.

5. Measuring cell (3) according to claim 1, that the supply hose (6) and the discharge hose (8) are designed to be shut off by means of hose clamp valves.

6. Measuring cell according to one of claims 1-5, characterized in that the measuring cell (3) together with the hose connections (6, 8, 39), the sterile filters (60, 110, 111) and Luer lock connection (61 ) and a collection bag possibly connected to the measuring cell (3) is designed as a disposable item and can be inserted into a device part (1) containing the measuring and evaluation electronics.

7. measuring cell (3 (according to claim 6, d a d u r c h g e k e n n z e i c h n e t that the measuring cell (3) one for the used

Radiation-permeable active area (202) with a light reflection surface (203) forming the inner wall and an outer wall (205) provided with an even number of serrated recesses (204), the outer side flanks (206) of the recesses (204 ) take an angle α with a straight line perpendicular to the reflection surface (203) and the opening angle of the serrated recesses (204) is 90 ° and the device part (1) containing the measuring and evaluation electronics has a light transmitter (208) and a light receiver (209) which are adjusted so that the emitted light beam when the measuring cell (3) is inserted assumes an angle a with a straight line perpendicular to the reflection surface (203) and the beam reflected at the same angle a strikes the receiver (209), the angle a resulting from the equation

a = sin (1 / n) + k

in which n is the refractive index of the material used for the area (202) and k can have a numerical value between 0.75 and 2.5.

8. The device according to claim 7, so that the area (202) is arranged in the lower part of the measuring cell (3).

9. Device according to one of claims 7 and 8, that the area (202) and the rest of the measuring cell (3) are made of different materials.

10. Device according to one of claims 7 and 8, that the entire measuring cell (3) including the region (202) are made of the same material.

11. The device according to claim 10, characterized in that the entire measuring cell (3 = including the area (202) made of acrylic -Butadi en-stryrol copoly it consists. 3 *

12. The apparatus of claim 10 d a d u r c h g e k e n n z e i c h n e t that the entire measuring cell (3) including the area

(202) consists of polymethyl methacrylate.

13. Device according to one of claims 7-12, that the wall thickness of the region (202) measured between the deepest point of one of the jagged recesses (204) and the reflecting surface

(203) is between 0.5 and 4 mm.

14. Device according to one of claims 7-12 d a d u r c h g e k e n n z e i c h n e t that the device has an infrared transmitter (208) and an infrared receiver (209).

15. The device as claimed in one of claims 7-12, that the transmitter (208) is an LED diode and the receiver (209) is a photodiode which emits or receives in the visible range of light.

16. A method for the continuous monitoring of body fluid emerging from a catheter, using a measuring cell (3) according to any one of claims 1 to 15, characterized in that the pitot tube (43) is brought into a gas-tight connection with the pressure cell (2), the body fluid passes through an inlet via a drip path into the inlet chamber (25) and from there, with the outlet hose (8) shut off, into the measuring chamber (4) and into the pitot tube (43), the pressure change in gas . space between the liquid level in the pitot tube (43) and the pressure cell (2) is measured, and thereby the filling volume of the measuring chamber (4) at certain times score and the flow rate per unit of time of body fluid is determined and the measuring chamber is periodically emptied (6) by briefly opening the drain hose (8) when the inlet is closed.

17. The method as claimed in claim 16, that the flow of urine, hemofiltrate, wound secretion, blood plasma or dialysis fluid is monitored.