WO2000065313A1

WO2000065313A1 - A flowmeter

Info

Publication number: WO2000065313A1
Application number: PCT/DK2000/000187
Authority: WO
Inventors: Thomas Friis JØRGENSEN; Mads Hejrskov Pedersen
Original assignee: Joergensen Thomas Friis; Mads Hejrskov Pedersen
Priority date: 1999-04-23
Filing date: 2000-04-14
Publication date: 2000-11-02
Also published as: AU3957700A; DK199900558A

Abstract

Bag assembly, flowmeter and method for continuously measuring human urine output, wherein the urine flow is measured by detecting the rotation of a signalling (34) device rotating passively in the urine flow.

Description

A f lowmeter

The present invention relates to a flowmeter and a method of measuring human urine output .

At hospitalisation of patients in intensive care units it is usual to monitor the patients' urine output.

This may be done, for example, over long periods, such as the so-called 24 -hour diuresis, or on an hourly basis, so-called one-hour diuresis.

In this connection, the patient excretes urine through a catheter and via tubes through a measuring device to a collection container.

In addition to measuring the urine output it is of importance that test may be carried out on the urine collected in the container. It is therefore a prerequi- site that the catheter, the tubes, the measuring device and the collection container may be sterilized and kept sterile prior to use.

Since these parts come into contact with the urine excreted by the patient and are thus contaminated during use, they are not reused, and efforts are therefore made to make them as inexpensive as possible.

In its simplest form, the measuring device and the collection container are combined in the form of a collection bag for the urine, which bag is provided with a volumetric scale allowing the total volume to be read on the bag and the volume flow to be calculated by subtracting the value of a previous reading and dividing by the time that has lapsed since the previous reading.

To be able to perform the calculation it is therefore necessary that for each reading the value read as well as the time of the reading have been recorded. Such systems are favourable in terms of costs, but leave much to be desired in terms of accuracy. There are further developments of such systems m which a measuring device m the form of a volumetric container is provided before the collection bag. This volumetric container is read at regular intervals, whereupon the contents are transferred to the collection bag .

In both these systems and the above systems, the reading is manual, and the measuring result and the time are written down. Such systems suffer from the disadvantage that it is important for an accurate reading that the volumetric container and/or the bag is/are suspended and vertically aligned. The reading becomes further complicated because the collection bag with pertaining volumetric container is typically suspended below the bed, since the urine of course has to be able to run away from the patient. Thus, the person reading the volumetric container either has to bend down to read or to pick up the bag and volumetric container for reading. Finally, both volumetric container and the pertaining movable parts m the form of valves and the like are complicated and cost-intensive and, as mentioned, they cannot be reused.

Various systems have been proposed for remedying the problems of manual reading of the volumetric container For example, both US-A-4343316 and US-A-4745929 describe systems m which a measuring volume or a volumetric container is arranged above a collection bag and is connected therewith via a tube which is closed off electromagnetically by a measuring unit. For measuring the volume, photocells are provided m connection with the volumetric container, which photocells at a specific degree of filling release the electromagnetic closmg-off of the tube so that the known volume is transferred to the collection bag concurrently with recordal thereof by the measuring unit. Since the transferred volume is known, the measuring unit can record the urine output

These systems suffer from the same disadvantages as the previously mentioned systems concerning vertical suspension .

Although these systems have the electronic and electromagnetic parts separated from the urme-conduct- mg system, it is still necessary to have a calibrated volumetric urine container, which cannot be reused, as mentioned above. Moreover, the electromagnetic closing off requires a complicated mechanical part which is relatively energy- intensive so that a battery supply becomes voluminous if the system is to be able to run continuously without any change of battery or recharging during the typical treatment period for a patient m intensive care, for example about 14 days. Normally, a mams supply via a cable is undesirable as patients m intensive care often need to be moved, for which purpose it would be necessary to interrupt the measuring. Moreover, the number of tubes and cables of a patient m intensive care is often so high already that they hinder staff movements so that further cables should be avoided EP-A-109373 describes a similar device using a peristaltic pump instead of magnetic valves This device exhibits the same disaαvantages concerning suspension and energy consumption as the above systems using magnetic valves. EP-679247 describes yet another device for measuring urine output. This device is based on measuring the weight of the urine Accordingly, a collection bag is suspended m a dynamometer. This dynamometer may incorporate a strain gauge and thus be adapted to have a low energy consumption The device further includes means for converting the mass measured into volume. Also this device has to be suspended approximately vertically to function although means are incorporated to compensate for skew suspension. An overall feature of the prior art described above is that a volume is measured at discrete time intervals. From EP-A-901778 there is known a two part system for measuring and monitoring post operation urine excretion. The system incorporating a separate electronic part in the form of an optical or capacitive drip sensor. The drip sensor is adapted to be removably attached to a transparent drip chamber interposed between the catheter and a collecting bag of the conventional kind. With a conventional collecting bag, ie . one without a measuring device, catheter or tube would either have to be cut above the collecting bag in order to allow the interposition of the drip chamber, or be delivered as separate parts . It is clearly the intention to deliver these as separate parts as it is described how the inlet tube of the bag may be cut down to a desired length. It is thus clear that the sterility is not an issue as it would be compromised when assembling the parts as described.

Apart from the sterility the use of a drip chamber involves some further problems.

One is that in order to function properly the device must, like some of the previously described prior art, be vertically suspended.

Another is that in order to produce the drops the continuous urine flow must be restricted. This is achieved by a narrow drip spigot ensuring that the urine is in the form of drops rather than a continuous stream.

In order to prevent solid objects such as blood clots, purulent matter and other impurities which may be present m the urine from blocking the narrow spigot a filter is placed upstream from the spigot.

The use of the narrow drip spigot is disadvantageous since it allows only a restricted flow rate. Further, even with the filter present there is a risk of blockage of the urine flow from the patient, as substantial amounts of eg. blood clots may be present in the urine in the post operation phase where it is intended to monitor the urine production. This may compromise the monitoring of the urine production and may even be harmful to the patient if the urine accumulates in the bladder.

The object of the invention is to provide a method that overcomes said disadvantages . The invention achieves this object through a method for continuously measuring human urine output, eg. through a catheder, which method is characterized in that the urine flow is measured by detecting the rotation of a signalling device rotating passively in the urine flow.

The basis of the present invention is thus the fundamental concept of measuring a continuous urine flow by means of a simple, reusable detector which has a low consumption of energy and which does not come into contact with the urine, and on this basis to calculate the urine output for a desired time interval as required .

In a preferred embodiment of the invention, the method for measuring human urine output is characterized m that a signalling part passively rotating m the urine flow is used, that the rotation of the signalling part is detected electronically, that the urine output is calculated on the basis of the electronically detected rotation of the signalling part and that the urine output is electronically read out. Advantageous further developments of the method according to the invention appear from the dependent claims 2 to 9.

Thus, in an advantageous embodiment the rotation of the signalling device is detected optically.

This has the substantial advantage that the free rotation of the passively rotating signalling device is not restricted.

In a further advantageous embodiment the urine output is calculated on the basis of the detected rotation of the signalling device, and that the urine output is electronically read out .

Calculating the urine output before readout is advantageous since in this way, the result may either be read-out directly on a display or to a separate display device or both.

It is particularly advantageous if the readout is effected to a display device or to a device which can store and show the instantaneous output over a long period, since this allows better long-term monitoring and the possibility of post-processing of the data.

It is however preferred that the readout is effected as accumulated volume read out at fixed intervals . This is the way the personnel is used to do it, and it thus requires little habituation and training.

If a separate display device which can store the values read out, it may be preferred to continuously read out and show instantaneous output rate over a long period, for better monitoring.

It is convenient if the urine is collected in a bag .

A bag is easy to hang, takes up little storage space prior to use, and easily disposed of. For the specific use where the urine is to be examined later it is advantageous if the catheter, signalling device and bag are sterile prior to use.

Preferably the catheter, signalling device and bag are assembled and sterilized during manufacture, as this allows for delivery of a sterile unit easily kept sterile during handling

For flow measuring, GB-A-2105855 describes a device comprising a separate electronic part and a separate mechanical part, the mechanical part comprising a first housing with both an inlet port and an outlet port for the liquid whose flow is to be measured. This housing encapsulates a rotatably mounted signalling device which can be brought to rotate by the liquid flow. This sig- nailing device is formed as a impeller with radial blades acted upon by the liquid flow. Perpendicularly to the blades there are also radial vanes which serve to interrupt a ray of light from the electronic part . The electronic part comprises a fork-shaped housing, one prong containing a source of light and the other prong containing a light-sensitive detector. The fork-shaped housing can be clicked onto the housing of the mechanical part m a manner to make the ray of light pass through it so that at rotation the signalling device interrupts this ray of light by its vanes, whereby the rotation of the signalling device can be detected. The detection is read out by means of a pair of cables.

This flowmeter is intended for measuring fuel consumption m automobiles and consequently has a number of disadvantages rendering it unsuitable for use m connection with the measurement of human urine output . In particular, the flow to be measured m connection with the fuel consumption of an automobile is subject to considerably larger and more abrupt fluctu- ations of the flow, for example at direct transition from idling to maximum acceleration At the same time it must be ensured, since the mechanical part is inserted m a fuel pipe, that no pressure drop occurs downstream of the meter as the primary purpose m an automobile remains forwarding fuel to the engine

The mechanical part of the flowmeter is therefore unnecessarily complicated and thus too costly for single use m urine measurement .

The electronic part is adapted to be clicked on to the mechanical part by means of shape-locking means. Since, contrary to the above described use for urine measurement, the use m an automobile does not necessitate frequent replacement of the parts of the flowmeter, both parts typically being able to last for the entire life of the automobile, the shape-locking means have a design that makes them no longer accessible once the mechanical part and the electronic part are assembled, as they are located inside the electronic part . To separate the mechanical and the electronic parts it is therefore necessary to break the structural integrity of the electronic part. This means that the electronic part proper has to be taken apart by means of tools to provide access to the shape-locking parts.

This is not compatible with medical use for urine measurement where, for reasons of hygiene, it is necessary to dispose of the mechanical part of the flowmeter after short-term use and replace it by another wnile the electronic part is retained

Furthermore, the prior-art flowmeter is powered by means of cables so that it will also exhibit the disadvantages described above concerning cables for patients m intensive care

From EP-A-140614 there is known a bag assembly using a vaned rotary flow indicator. This bag assembly, however, does not deal with sterile measurement of urine production. Instead it deals with irrigation of a stoma.

The irrigation of a stoma typically made with pure, Put not sterile, water Thus the teaching of the docu- ment does not concern sterility, and the bag assembly accordingly is a reusable bag where the components have and extended useful life.

Further, since pure water is used for irrigation the document does not concern any teaching relating to the passage of solid objects such as blood clots and purulent matter which is an important aspect of the present invention

Finally the vaned flow indicator is merely a visual indication, and there is no indication that a precise measurement may be derived from the rotation thereof.

The document thus does neither deal with nor presents a solution to the problems addressed m the present invention.

It is a further object of the invention to provide a flowmeter to be used m the method according to the invention .

This object is achieved by a flowmeter comprising a separate electronic part and a separate mechanical part, the mechanical part comprising a first housing with both an inlet port and an outlet port for the liquid whose flow is to be measured, the electronic part and the mechanical part both being adapted to be assembled into constituting a complete flowmeter and to be disassembled for replacement of one part while retaining their individual integrity as units, characterized m that the mechanical part comprises a rotata- bly mounted signalling device which is encapsulated m the first housing and may be brought to rotate by the liquid flow, and that the electronic part comprises and means for detecting the rotation of the signalling device .

This has the advantage that the mechanical part may be a disposable unit, disposable with the bag assembly, whereas the electronic part is reusable.

Advantageous further developments of the invention appear from the dependent claims 13-26.

Thus, the signalling device is preferably an impeller which comprises at least six blades. With less blades, eg. three, the invention will still work.

However, the rotation speed will not be as constant as desired. With a larger number of blades this is not a problem. However, increased mass from a subatantially larger number of baldes will make it harder for the liquid to rotate the impeller and further the increased materal costs make a large number of blades undesirable.

The preferred number of blades is thus six, but other numbers, in particular a larger number, could be used.

Also, preferably the first housing is transparent and the detection is performed by optical means arranged in connection with the second housing and preferably the signalling device is provided with screens to block the passage of light through the first housing.

It is advantageous if the screens are disposed between respective pairs of blades.

Preferably, the signalling device is dimensioned with a clearance in relation to the first housing, whicn clearance is sufficient to permit passage of solid objects, such as blood clots or purulent matter, having dimensions of up to approximately 2 mm that may be present in the fluid.

In the flowmeter the first housing may also comprise a constricted area adapted to the thickness of the screens. The flowmeter may further be advantageous m that the readout means is a display or m that the readout means are a data communications line.

Another advantageous feature of the flowmeter is that the second housing comprises means for use m suspension of a reservoir for collection of the fluid which has passed the flowmeter.

Also a flowmeter wherein the mechanical part is a disposable part and the electronic part is a reusable part is advantageous.

In this respect a flowmeter wherein the mechanical part and the electronic part have mutually corresponding fπctional or shape-locking means for their assembly is preferred, m particular the friction or shape-locking means most exposed to wear may provided on the disposable part .

Preferably, the through- flowing fluid is human urine .

Finally, the invention relates to a preassembled disposable bag assembly comprising a tube, a bag, and a mechanical part comprising a housing with both an inlet port and an outlet port and a rotatably mounted signalling device encapsulated m the housing, characterized m that the mechanical part is adapted to be assembled with a separate reusable electronic part.

This bag assembly provides a disposable urine collection and signalling part for use m connection with the method and the flowmeter according to the invention Preferably the preassembled disposable bag assembly is sterile, sterilized during or m connection with manufacture

Thus, it does not have to be sterilised immediately before use. Also preferably the preassembled disposable bag assembly comprises at least one eye for suspending the bag

This allows for the suspention of the bag m connection with suspension means associated with the electronic part .

Expressed m other words the present invention concerns a flowmeter comprising a separate electronic part and a separate mechanical part, the mechanical part comprising a first housing with both an inlet port and an outlet port for the liquid whose flow is to be measured, and a rotatably mounted signalling device which is encapsulated m the first housing and can be brought to rotate by the liquid flow, the electronic part comprising a second housing, means for detecting the rotation of the signalling device and readout means, wherein the electronic part and the mechanical part can both be assembled into constituting a complete flowmeter and be disassembled for replacement of one part while retaining their individual integrity as units.

The invention may also be expressed m other words as s method of measuring human urine output, wherein the urine flow is measured continuously, and that the urine output is read out electronically. In this method of measuring human urine output a signalling device passively rotating m the urine flow is preferably used, the rotation of the signalling device detected electronically, the urine output calculated on the basis of the electronically detected rotation of the signalling device, and the urine output is electronically read out

Preferably the readout is effected as accumulated volume read out at fixed intervals

Alternatively the readout is effected continuously as instantaneous output rate The readout may also be effected to a display device or to a device which can store and/or show the instantaneous output over a long period.

Finally expressed m other words the invention concerns a bag assembly comprising a tube and a bag further comprising a mechanical part comprising a housing with both an inlet port and an outlet port and a rotatably mounted signalling device encapsulated m the housing The invention will now be described m more detail below with reference to examples and with reference to the schematic drawing, m which

Fig. 1 is a perspective view of a system with a urine bag with mounted signalling part and as yet unmounted flowmeter,

Fig. 2 is a perspective view of the system according to Fig. 1 during mounting of the flowmeter,

Fig. 3 is a perspective front view of the system according to Figs. 1 and 2 with mounted flowmeter, Fig. 4 is a perspective rear view of the system according to Figs. 1 and 2 with mounted flowmeter,

Fig. 5 shows the system according to Fig. 4 mounted on a suspension device which supports the urine bag,

Fig. 6 is a schematic cross-sectional view of a signalling means with a rotatable signalling device according to the present invention, seen along the axis of rotation of the signalling device,

Fig 7 is a schematic cross-sectional view of the signalling part according to Fig 6, seen along the line X-X,

Fig. 8 s a schematic cross-sectional view corresponding to Fig. 7 of another embodiment of a signalling part .

Fig. 1 shows a separate electronics part 1 for mounting m connection with a bag assembly 2 comprising a bag 40 for collection of urine, a signalling part 3 and a tube 16 for passing urine excreted from a patient to the bag 40 The bag assembly 2 is preferably a prefabricated or ready-made catheter bag having one end of a tube 16 fixed to it, the other end of the tube being adapted, m a manner known per se, to be connected to a catheter. The signalling part 3 is preferably inserted between the tube 16 and the opening m the bag 40 Alternatively, there might be a piece of tube between the bag 40 and the signalling part.

The parts comprised m the pre- fabricated bag assembly are assembled and sterilized during manufacture so as to be delivered, m an appropriate packaging sterile and ready for use with the separate electronics part 1.

The electronics part, which is a separate unit, is adapted to detect a parameter from the signalling part 3, for example rotation of a signalling rotor 34 m the signalling part 3. In consideration of the flexibility of the tube 16, it may include both very flexible corrugated tube parts 6 and less flexible smooth tube parts 5 To enable the bag 40 to be suspended, it may be provided with one or more eyes 4 Fig 1 best shows how a signalling part 3 has been inserted between the tube 16 and the bag 4 m the embodiment shown Alternatively to being arranged between tne tube 16 and the bag 40, the signalling part 3 can, of course, also be inserted elsewnere m the tube 16 that is, at a distance from the bag 40 However, m consideration of the suspension it is preferred, as will e described below, to nave the signalling part arranged as close to the bag 40 as possible

Tne electronics part 1 is a separate unit which comprises a housing 8 with a cover 9 Externally, the electronics part 1 comprises an on/off switch 11, a plug 10 for mounting an external connection cable (not shown) , guideways 12 for a suspension device 14, a recess 13 for reception of the signalling part 3 and a display 15.

In addition to the on/off function, the switch 11 can be used to control several display functions, such as is known from, for example, watches and bicycle computers, but it is, of course, also possible to use more than one switch to control the functions, for example like the pushbuttons 24, 25 indicated.

Fig 2 shows how the electronics part is arranged above the signalling part 3 and is pressed into place . Preferably, the supporting device 14 is used and inserted into the guideways 12, thereby closing the recess 13 m which the signalling part 3 is located, for establishing the mechanical connection between the signalling part 3 and the electronics part 1.

However, resilient, releasable engagement means 18, known per se, may also be provided. An example thereof are resilient claw means 18 arranged m the recess 13. They are arranged so that they correspond to the indentations 20, where part of the inlet tube 21 m the signalling part 3 is uncovered. These claw means 18 can then resiliently engage about the circular cross-section of the tube, effecting fixation m both the transversal and the longitudinal directions. Preferably the claw means 18 are formed as an integral part of the housing 8 and are made of a suitable type of plastic material. The suspension device 14 is provided with a hook

19, so that the device 14 can be suspended from, for example, the bed frame of a hospital bed m a manner to make the display 15 visible to the hospital staff.

Opposite the hook 19, the suspension device has a cross-piece 17 on which there are a number of pegs 141 for the purpose of hanging the bag 40 by means of the eyes 4 of the latter. The cross-piece 17 also serves as a stop to its displacement in the guideways 12. The suspension device 14 may be made of plastic or of metal, 5 it merely has to possess the requisite strength, in practice this means for supporting the weight of a filled urine bag. If the suspension device is made of plastic, this plastic material should preferably be opaque to prevent light penetration from the outside,

10 which will be explained below.

When the three parts, the signalling part 3, the electronics part 1 and the bag assembly 2, are assembled as shown in Fig. 5, they constitute an aggregate unit which is easy to handle and simplifies the monitoring

15 of a patient's urine output.

The signalling part 3 will now be described with reference to Fig. 1 and Figs. 6 to 8.

The signalling part comprises a housing 31. At least in certain places, the housing 31 has windows 33

20 which are transparent to light of a given wavelength, for example infrared or visible light. These windows 33 are arranged so as to permit light to pass through the housing 31 in an axial direction in relation to the axis of rotation 32 of a rotatably mounted signalling rotor

25 34.

The signalling rotor 34 is an impeller provided with a number of blades 35 and a number of screens 36. Preferably, six blades are provided, as this yields a suitably smooth movement of the rotor at the flow rates

30 typically to be measured.

The signalling rotor 34 is rotatably mounted in a preferably cylindrical cavity 7 in the rotor housing 31. The cavity 7 is provided with a tubular inlet port 37 n and a similar tubular outlet port 38. The inlet port 37

35 and the outlet port 38 are arranged at opposite ends of a chord for the circular cylinder cross-section of the cavity 7. The chord may, for example, be arranged so that it approximates a tangent .

When liquid m the form of urine flows into the

5 housing 31 through the tubular inlet port 37 and out through the outlet port 38, the liquid will impinge on the blades 35 and thus drive the signalling rotor 34 round.

When a urine flow is present the signalling rotor 0 will passively rotate freely and largely unrestricted apart from possible friction m the bearings.

Photocell means are arranged m the electronics part 1 on opposite sides of the recess which, m the assembled state, receives the signalling part 3. The 5 photocell means may comprise a light-emitting diode 51 on one side and, arranged oppositely, a photo detector 50 m the form of, for example, a photo diode, photo transistor, photo resistor or the like. These photocell means are also arranged so that they correspond to the 0 transparent windows 33 m the rotor housing 31. They can thus detect light passing through the signalling part 3 when the latter is arranged m the recess 13.

Using photocell means and light for detecting the light passing through the signalling part 3, when not 5 interrupted by the signalling rotor 34 is advantageous since the use of light will not influence or restrict the free rotation of the signalling rotor 34.

Although transparent windows 33 m the rotor housing 31 have been mentioned m the above, this does C not preclude the entire rotor housing 31 from being transparent. This may especially be the case m embodiments as tne one described, where the entire rotor housing 31 is confined between the electronics part 1 and the suspension device 14 and therefore cannot be 5 influenced by disturbances from external light, of course provided that the housing 31 and the suspension device 14 are not made of a transparent material . The resulting advantage thereof is that the entire housing can be made of very few parts of one and the same type 5 of plastic.

At passage of urine through the signalling part 3 , the urine flow will make the signalling rotor 34 rotate so that the screens 36 will pass between the photocell means and interrupt the passage of light to the detector

10 50.

The electronics part 1 has calculator electronics 52 capable, on the basis of the detected interruptions of the light and the resulting signals from the photo- detector 50, of calculating the rotational speed of the

15 signalling rotor and on this basis the urine flow. The calculator electronics 52 are preferably microprocessor- based.

For this calculation, the calculator electronics also have to know the speed characteristics of the

20 signalling rotor 34 as a function of the flow. That is, the non-linear correlation between the rotational speed of the signalling rotor and a given flow. For a signalling part 3 this can easily be predetermined by experiments. If standardized signalling parts 3 are made

25 so that only certain standardized signalling parts 3 fit into a given corresponding recess 13 in the electronics part 1, the electronics part can be made to be usable only in connection with signalling parts for which it knows the given speed characteristic.

30 To minimize the power consumption for the photocell means, the distance between the light-emitting diode 51 and the photo detector 50 can be minimized. In a preferred embodiment according to Figs. 7 and 8 this is done by the rotor housing 31 having a constriction 39

35 through which the screens 36 pass. A preferred embodiment provides a large clearance 60 between the signalling rotor 34 and the rotor housing 31 This permits passage of any impurities m the urine which might cause slowing down or blocking of the signalling rotor 34. This clearance has to be balanced with the dimensions of the impurities to be taken into consideration This means mainly such impurities as can pass through the catheter

It has turned out that even with a considerable clearance 60, for example 2 mm on both sides of the signalling rotor m a cylindrical housing having an internal height of 6 mm and a blade length of half the radius of the cylinder, it is possible to have a speed characteristic which permits a calculation of the flow at an accuracy of few per cent .

As mentioned, the electronics part 1 is provided with an m-built display 15, which may, for example, show the current flow, the accumulated volume over a long period, the maximum flow, etc It is also possible to provide the electronics part with a plug for external connection, for example a data communications line so that the calculator unit 52 can exchange information with, for example, a general patient monitoring unit In this case the electronics part 1 may possibly be powered through this external connection

Generally, however, the electronics part 1 will have such low power consumption that it can function as an independent unit and therefore has no need of an external power supply It is therefore also easy to handle, as tne three parts are simply procured for a patient, they are assembled, the assembly is connected to the patient's catheter and suspended m a suitable visible place, and the electronics part 1 s reset By suitable pressures on the pushbuttons 24, 25 or on 11, depending on the design of the electronics part, the type of readout desired is set. Subsequently, readouts can be made continuously. An advantageous manner of performing the readout is as the accumulated volume, which is read out at fixed intervals. This is the manner m which staff has conventionally performed readouts and therefore hardly requires habituation. Alternatively, the readout can be effected continuously as a instantaneous output rate. The advantage of this is that the staff need not perform any calculations

It is especially advantageous if the latter readout is effected to a display device which can store and show the instantaneous output over a long period.

It will then be possible to obtain a graph of the patient's urine output which not only indicates the instantaneous output or the mean value over a long period, but also the actual output at any time. This can also advantageously be used m connection with the above patient monitoring devices.

Alternatively, the separate unit m the form of the electronics part 1 can be formed as a detector which directly detects the liquid flow m a tube, for example by acoustical methods. This obviates the signalling part 3 with the mechanical signalling device and the movable parts entailed thereby. However, m consideration of the complexity and energy consumption of the electronics, optical detection on the basis of the above rotating signalling device is preferred.

List of reference numerals used Electronics part

Bag assembly

Signalling part

Eyes

Smooth tube parts

Corrugated tube parts

Cavity

Housing

Cover

Plug

Switch

Guideways

Recess

Suspension device

Display

Tube

Cross-piece

Claw means

Hook

Indentation

Inlet tube

Pushbutton

Rotor housing

Axis of rotation

Transparent window

Signalling rotor

Blade

Screen

Inlet port

Outlet port

Constriction

Bag

Volumetric graduation

Photo detector Light-emitting diode Calculator electronics Clearance Pegs

Claims

P A T E N T C L A I M S 1. A preassembled disposable bag assembly comprising a tube (16) , a bag (40) , and a mechanical part (3) comprising a housing (31) with both an inlet port (37) and an outlet port (38) and a rotatably mounted signalling device (34) encapsulated m the housing (31), c h a r a c t e r i z e d m that the mechanical part (3) is adapted to be assembled with a separate reusable electronic part (1) . 2. A preassembled disposable bag assembly according to claim 1, c h a r a c t e r i z e d m that it is sterile .

3. A preassembled disposable bag assembly according to any one of the preceding claims, c h a r a c t e r - l z e d m, that it comprises at least one eye (4) for suspending the bag.

4. A method for continuously measuring human urine output, which method is c h a r a c t e r i z e d m that the urine flow is measured by detecting the rotation of a signalling (34) device rotating passively m the urine flow.

5. A method of measuring human urine output according to claim 4, c h a r a c t e r i z e d m that the rotation of the signalling device (34) is detected optically.

6 A method according to claim 4 or 5 , c h a ra c t e r i z e d m that the urine output is calculated on the basis of the detected rotation of the signalling device, and that the urine output is electroni- cally read out

7. A method according to claim 6, c h a r a c t e r i z e d in that the readout s effected as accumulated volume read out at fixed intervals.

8. A method according to claim 6, c h a r a c t e r i z e d m that the readout is effected continuously as instantaneous output rate.

9. A method according to claim 6, c h a r a c - S t e r i z e d m that the readout is effected to a display or to a device which can store and/or show the instantaneous output over a long period.

10. A method according to any one of claims 4 to

9, c h a r a c t e r i z e d m that the urine is col- 0 lected m a bag.

11. A method according to any one of claims 4 to

10, c h a r a c t e r i z e d m that the catheter, signalling device and bag are sterile prior to use.

12. A method according to claim 11, c h a r a c - 5 t e r i z e d m that catheter, signalling device and bag are assembled and sterilized during manufacture.

13. A flowmeter comprising a separate electronic part (1) and a separate mechanical part (3) , and readout means, the mechanical part (3) comprising a first 0 housing (31) with both an inlet port (37) and an outlet port (38) for the liquid of which the flow is to be measured, the electronic part (1) and the mechanical part (3) both being adapted to be assembled into constituting a complete flowmeter and to be disassembled 5 foi replacement of one part while retaining their individual integrity as units (15) , c h a r a c t e r i z e d m that the mechanical part comprises a rotatably mounted signalling device (34) which is encapsulated m the first housing (31) and may be 0 brought to rotate by the liquid flow, and that the electronic part (1) comprises means (50, 52) for detecting the rotation of the signalling device (34; .

14. A flowmeter according to claim 13, c h a r a c t e r i z e d m that the signalling device (34) 5 is an impeller.

15. A flowmeter according to claim 13, c h a r a c t e r i z e d m that the impeller comprises at least six blades (35) .

16. A flowmeter according to any one of claims 13 to 15, c h a r a c t e r i z e d m that the first housing (31) is transparent and that the detection is performed by optical means (50, 51) arranged m connection with the electronic part (1) .

17. A flowmeter according to claim 16, c h a r - a c t e r i z e d m that the signalling device is provided with screens (36) to block the passage of light through the first housing (31) .

18 A flowmeter according to claim 17, c h a r a c t e r i z e d m that the screens (36) are disposed between respective pairs of blades (35) .

19. A flowmeter according to any one of claims 13 to 18, c h a r a c t e r i z e d m that the signalling device is dimensioned with a clearance (60) m relation to the first housing, which clearance is sufficient to permit passage of solid objects having dimensions of up to approximately 2 mm that may be present m the liquid.

20. A flowmeter according to claim 17, c h a r a c t e r i z e d m that the first housing (31) comprises a constricted area adapted to the thickness of the screens (36) .

21. A flowmeter according to claim 13, c h a r a c t e r i z e d in that the readout means (15; is a display 22 A flowmeter according to claim 13, c h a r a c t e r i z e d m that the readout means is a data communications line

23 A flowmeter according to claim 13, c h a r a c t e r i z e d m that the second housing (8) comprises means for use m suspension (12) of a reser- voir (40) for collection of the liquid which has passed the flowmeter.

24. A flowmeter according to any one of claims 13 to 23, c h a r a c t e r i z e d m that the mechan- ical part (3) is a disposable part and the electronic part (1) is a reusable part.

25. A flowmeter according to any one of claims 13 to 24, c h a r a c t e r i z e d m that for their assembly the mechanical part (3) and the electronic part (1) have mutually corresponding fπctional or shape- locking means (18) .

26. A flowmeter according to claim 25 when dependent on claim 24, c h a r a c t e r i z e d m that the friction or shape- locking means most exposed to wear are provided on the disposable part (3) .

27. A flowmeter according to any one of claims 13 to 26, c h a r a c t e r i z e d m that the mechanical part constitutes the mechanical part (3) of a preassembled bag assembly according to any one of claims 10 to 11.

28. A flowmeter according to any one of claims 13 to 27, c h a r a c t e r i z e d m that the through- flowing liquid is human urine.

29 Use of a flowmeter according to any one of claims 13 to 28 for measuring human urine output

30. A preassembled disposable bag assembly according to any one of claims 1 to 3 , c h a r a c t e r i z e d m that it comprises the mechanical part of a flowmeter according to any one of claims 13 to 28