Urine Weighing Apparatus

Abstract

A urine weighing apparatus comprises support means configured to support a urine collection vessel, a transducer for converting the weight of the vessel into an electrical signal, and a processor for processing the electrical signal to continuously calculate the weight of the vessel. The processor calculates the weight of urine therein and allows the urine output rate to be determined.

Claims

1. A urine weighing apparatus comprising support means configured to support a urine collection vessel, a transducer for converting the weight of the vessel into an electrical signal, and a processor for processing the electrical signal to continuously calculate the weight of the vessel, and thereby calculate the weight of urine therein and allow the urine output rate to be determined.

2. An apparatus according to claim 1, wherein the apparatus is configured to measure the weight of the vessel, and thereby calculate, in real-time, the volume of urine therein.

3. An apparatus according to claim 1, wherein the transducer is a load cell.

4. An apparatus according to claim 3, wherein the load cell is an S-type load cell, a piezoelectric load cell, a shear beam load cell, a double-ended shear beam load cell or a rope clamp load cell.

5. An apparatus according to claim 3, wherein the load cell is an S-type load cell with a minimum of two strain gauges configured to measure both positive and negative changes in force.

6. An apparatus according to claim 1, wherein the apparatus is configured to calculate voided urine volume at a plurality of time points, and then calculate a rate of change of urine volume over the plurality of time points.

7. An apparatus according to claim 1, wherein the support means is a hook, a latched hook, a clip or cradle which supports the collection vessel.

8. An apparatus according to claim 1, wherein the urine collection vessel is a urine collection bag.

9. An apparatus according to claim 1, wherein the apparatus comprises an amplifier configured to amplify the electronic analogue signal generated by the transducer.

10. An apparatus according claim 1, wherein the apparatus is configured to process the data to remove unwanted changes and data artefacts due to shock inputs, clinical interventions and/or movement of the apparatus and/or subject.

11. An apparatus according to claim 10, wherein the processor is programmed with an algorithm which manages the fluid volume data, including interventions, such as bag emptying operations and urine sample collections, which abruptly change the vessel's weight.

12. An apparatus according to claim 1, wherein the apparatus comprises a wireless module for transmission of data to a separate electronic device, computer, server, web page, laptop, tablet or smart phone.

13. (canceled)

14. A method of measuring the urine output from a subject, the method comprising attaching the apparatus according to claim 1 to the subject, and measuring the urine output therefrom.

15. A method according to claim 14, wherein the method comprises processing the data to remove unwanted changes and data artifacts due to shock inputs, clinical interventions and movement of the apparatus and/or subject.

16. A urine detection system comprising the apparatus according to claim 1, and a urine collection vessel.

17. A system according to claim 16, wherein the system comprises a delivery means for delivering urine from a subject to the urine collection vessel.

18. A system according to claim 17, wherein the delivery means is a catheter.

19. (canceled)

Description

[0032] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

[0033] FIG. 1 shows a forward view of one embodiment (i.e. the MictuRATE MKII) of an apparatus for continuously measuring urine output according to the invention;

[0034] FIG. 2 is a block diagram of one embodiment of the apparatus used in the MKII shown in FIG. 1;

[0035] FIG. 3 is a forward view showing the location of the apparatus in use by a catheterised patient on a hospital bed;

[0036] FIG. 4 is a schematic diagram showing the main components of a urine detection system in which the apparatus shown in FIGS. 1 & 2 can be used. However, FIG. 4 shows a second embodiment of the apparatus incorporated in the system;

[0037] FIG. 5 shows a plan view of a tablet computer (used for testing) that may be wirelessly connected to the apparatus shown in FIG. 1 and used in the system shown in FIG. 4;

[0038] FIG. 6 shows examples of clinical raw and processed (with a processing algorithm) data generated using an embodiment of the invention (MictuRATE MK II). The upper panel shows raw data with intermittent noise events. In the lower panel the noise events have been removed; and

[0039] FIG. 7 shows a virtual embodiment of a MictuRATE apparatus for continuously measuring urine output according to the invention. Importantly, it shows how such a monitoring device may be used within a clinical environment.

EXAMPLES

Example 1Gravimetric Urine Output Measuring Apparatus

[0040] Referring to FIGS. 1 and 2, there is shown an embodiment of the gravimetric apparatus 2 according to the invention, which may, for example, be used to measure urine output from a catheterised patient. The gravimetric apparatus 2 comprises a miniature S-type load cell 16, which is operably linked to a hook 4 that is used to bear the weight of a urine collection bag 8. The hook 4 is positioned such that, when the apparatus 2 is in use, it is in-line with the urine collection bag 8 (i.e. the apparatus 2 is configured such that it has a vertical uniaxial arrangement with respect to the urine collection bag 8). Thus, strain/weight applied to the hook 4 by the urine collection bag 8 is converted into an analogue electrical signal by the S-type load cell 16.

[0041] Referring to FIG. 2, there is shown a block diagram showing the inter-relationship between various components of one embodiment of the gravimetric apparatus 2 (referred to as MictuRATE Mk II). As can be seen, the S-type load cell 16 converts a change in force (i.e. strain), applied to the hook 4 by the urine bag 8, into an analogue electrical signal. The (analogue) electrical signal is typically collected over an interval of 1000 ms at 1 MS/s at a resolution of 12 bits. The electrical signal is inversely proportional to the force being measured. The electrical signal is amplified by an amplifier 18 and then fed into an analogue-to-digital converter (ADC) 20, which is disposed within a signal-processing module 26. A microprocessor 22 converts the digital output data from the ADC 20 into comma separated values (CSV) and then transmits the converted data to a wifi module 24a. The microprocessor 22 exchanges data with a memory storage device 28. The wifi module 24a, the microprocessor 22 and the memory storage device 28 are also disposed within the signal-processing module 26. The wifi module 24a enables wireless telemetry of urine output data to a separate computer located at, for example, a nursing station 14, such that the data can be monitored in real time and/or stored in the patient's electronic record. The load cell 16, the amplifier 18 and the signal-processing module 26 are all powered by a battery and power management system 29.

[0042] As shown in FIG. 3, in the use, the gravimetric apparatus 2 is attached to the bed/trolley 12 of a catheterised patient (not shown). The catheter 10 is attached to the patient, and is fed directly into a urine collection bag 8, which is elevated off of the floor by the hook 4 of the in-line gravimetric apparatus 2. Thus, when the patient urinates, their urine flows into the urine collection bag 8 via the catheter 10. The gravimetric device 2 measures both the total amount of urine output, based on the weight of the urine collection bag 8, and also the rate of urine output, based on the change in weight of the collection bag 8 over time.

[0043] FIG. 4 shows an embodiment of a urine detection system 50 including the gravimetric apparatus 2 described above. Data output of the microprocessor 22 is processed by software 54, and then transmitted directly (i.e. via a wired connection) to a display and/or input apparatus 52. Data (i.e. urine volume and output rate) is displayed in real time. The apparatus 2 includes a Tare button 56 to allow correction for the urine vessel 8 weight at the start of the measurement, when the vessel is emptied or when a sample is removed. If the alert signal notifies a full vessel status, the algorithm 54, in conjunction with the Tare function 56, will recognise a replaced or emptied vessel 8 and append subsequent data to that already collected.

[0044] In addition, or alternatively, the processed data from the microprocessor 22 is fed to a wireless or wifi module 24a. The data emitted by the wireless/wifi module 24a is detected by a corresponding module 24b operably linked to a separate display 14 of a computer, mobile phone, smart phone, tablet or similar monitoring device, an example of which is shown in FIG. 5, which may be located at a nursing station. The data is then converted by software 38 loaded on the computer/tablet/monitoring system 14 into a format that can be understood by a nurse, displayed on the screen and saved directly to the patient's electronic file. Data (i.e. urine volume and output rate) is displayed in real time.

[0045] The upper panel of FIG. 6 displays raw data collected from a catheterised patient using the apparatus 2 according to the invention. Raw data includes multiple digitised load cell values with a date-time stamp. The x-axis corresponds to time and the y-axis corresponds to sensor output, in Volts. The raw data of the upper panel of FIG. 6 has been processed using MS Excel to remove noise events mentioned in the upper panel, such as treatment and nurse check.

[0046] The data output of the lower panel of FIG. 6 is the output, i.e. the descending line, of the urine output monitor. This data is inversely proportional to the total volume of urine output and is therefore used to calculate the total volume of urine output, i.e. the ascending line, of the catheterised patient. There is no medical data available from the subject; known as Patient X except that they were heavily sedated, had no renal complications and their fluid input was being managed at 180 ml/hr (typical output is therefore expected to be between 1 ml and 2 ml/hr/kg). As expected for patient X, the urine output was steady. This was recorded by the apparatus 2 (see FIGS. 1-3) and included the output volume (at any point in time), average rate and output characteristics. The resolution of the continuous monitoring achieved by the apparatus 2 is such that any change in output quickly identifies oliguria, polyuria and anuria (or potential catheter blockage) in the patient.

Example 2Applications of the Gravimetric Urine Output Measuring Apparatus

[0047] The apparatus 2 measures the urine output and flow rate of a catheterised patient in either the clinical or care home setting. The apparatus 2 works with any currently used collection bags 8 because it adopts an in-line measuring technique. This feature also mitigates any infection risk as there are no expensive sensors or dead volumes in the actual catheter tube 10 (difficult to sterilise micro volumes) or adaptors connected to existing catheter tubes. In fact, there is no change in the current hung bag configuration, except that the apparatus 2 is in-line with the bag 8; this makes the system very familiar with all medical and care staff. Unlike the existing technique of reading levels from a flexible bag (or rigid flow rate container), the apparatus 2 is consistently accurate and sensitive to small changes in collected fluid. Signal processing and algorithms are used to remove spurious data caused by routine intervention (a bed bath for example) and movement of the patient. During initial set-up by nursing staff the apparatus 2 is initiated (tare function for example) and subsequent changes (bag 8 emptied or urine sample removed) recorded by user interface on the apparatus 2 or automatically by the software algorithm 54.

[0048] The apparatus 2 can also include alarms for blockage, sudden change in output and/or full bag status. The apparatus 2 requires no leads to connect to a computer base station 14, which is achieved via a wireless link and has no external units, like a power supply or separate display (except data displayed wirelessly on a nursing station computer 14). There are two basic operating modes for the apparatus 2; wireless monitoring mode, in which the raw data from the apparatus 2 is transmitted wirelessly to a nursing computer base station, tablet or laptop or smart phone 14, and standalone operation mode, in which the apparatus 2 is completely independent and operated via a user interface on the surface of the apparatus 2.

[0049] Standalone operation lends itself to small scale use or facilities that do not have a well-developed IT infrastructure (possibly emerging countries). Nursing staff would still record the data manually, from the apparatus display, on common fluid balance charts. Supporting both modes of operation is the display on device feature that shows current values, recent fluid trends and alerts. Furthermore, this feature enables easy reading of the data at night by nursing staff without switching on the lights, a common complaint by patients.

[0050] When employed in a wireless monitoring mode the software installed on a separate computer 14 continuously monitors the urine output, providing a high resolution trend and history, which provides integrity of data and avoids possible falsification of data or incorrect entry of data by staff. The forgotten catheter is a common problem across the medical industry and the apparatus 2 offers a partial solution to this concern if it is used routinely for all catheterised patients by flagging use of apparatus 2 and by assumption of use of a catheter 10 via an electronic record. The apparatus 2 is also rugged being mainly solid state and hence can be used in a variety of environments e.g. hospital, care homes etc. The apparatus 2 is reusable as it can be moved and recharged for use easily. Finally, as there is no direct interface with the catheter 10 and due to its sealed type box design can be easily cleaned with wipes etc. to meet medical cleanliness requirements avoiding need for specialised cleaning protocols and facilities.

REFERENCES

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