Fluid monitoring

Abstract

A monitoring apparatus for monitoring fluid flow into or out of a patient comprises a fluid flow sensor and an output means. The fluid flow sensor is configured to attach to a fluid line fluidly connected to the patient and measure fluid volume data comprising data proportional to the volume of fluid which has passed through the fluid line over a time period. The monitoring apparatus is configured to determine, using the fluid volume data, a volume of fluid which has passed through the fluid line over the time period. The output means is configured to provide an output based on the volume of fluid and the time period.

Description

[0001] 124.172.170723 / 02

[0002] Fluid Monitoring

[0003] FIELD

[0004] The present invention relates to an apparatus, system, method, and computer software for monitoring fluid flow into and / or out of a patient.

[0005] BACKGROUND

[0006] In some healthcare settings, a patient may be provided with fluids by being connected to at least one fluid source, e.g. an intravenous (IV) bag containing blood, saline solution, antibiotics, etc. These fluids may be provided to the patient via any appropriate input devices, such as intravenously by cannulas, or via a feeding tube (e.g. a nasogastric feeding tube). In some situations, fluids will also leave the patient through a medical device, e.g. through a catheter or surgical drain.

[0007] The rate at which fluid is supplied to the patient from a fluid source (e.g. an IV bag) may be set by a healthcare professional. Usually, the healthcare professional will set an instantaneous flow rate of fluid from the source in terms of volume (e.g. millilitres per hour) or in terms of drops (e.g. drops per minute). In the exemplary case of the supply of fluid from an IV bag, the total volume of fluid supplied to the patient is typically determined by assessing the volume of fluid left in the IV bag and / or the number of IV bags used. The total fluid volume provided to the patient can be difficult to track using this technique.

[0008] It is similarly difficult to track the amount of fluid which has left (i.e. flowed out of) the patient. More specifically, it is difficult to track the amount of fluid which has flowed out of the patient in a given time. Net fluid flow in a patient, sometimes referred to as fluid balance, i.e. the difference between he fluid that has gone into a patient and the fluid which has left the patient, is a useful measure in a healthcare setting. For example, if a patient is given 500 millilitres of fluid per hour via a canula, but only expels 50 millilitres per hour via a catheter, then is it highly probable that the fluid is accumulating elsewhere in the body. A scenario such as this poses significant risk to overall patient wellbeing and recovery, and the detection of such a scenario could easily be missed by healthcare professionals using current equipment until substantial time has passed. The present invention aims to address or at least mitigate one or more of the problems outlined above.

[0009] SUMMARY

[0010] From a first aspect, the invention provides a monitoring apparatus, for monitoring fluid flow into or out of a patient, the monitoring apparatus comprising:

[0011] a fluid flow sensor configured to:

[0012] attach to a fluid line fluidly connected to the patient; and measure fluid volume data comprising data proportional to the volume of fluid which has passed through the fluid line over a time period; wherein the monitoring apparatus is configured to determine, using the fluid volume data, a volume of fluid which has passed through the fluid line over the time period, and wherein the monitoring apparatus further comprises:

[0013] an output means configured to:

[0014] provide an output based on the volume of fluid and the time period.

[0015] Thus it will be seen that, in accordance with the first aspect, by determining a volume of fluid which has passed through a fluid line connected to a patient over a time period and providing an output based on both the volume of fluid and the time period, the fluid flow into or out of a patient can be more appropriately monitored by a healthcare professional. The apparatus according to the invention may help inform healthcare professionals of the actual volume of fluid passing through the fluid line over a period of time, rather than having to rely on, for example, manual extrapolation using a preset flow rate set at the fluid source. Healthcare professionals may intervene based on the output if, for example, the output indicates that an abnormal volume of fluid has passed through the fluid line over the time period. For example, the output may indicate that too little or too much fluid has passed through the fluid line over the time period, which could indicate problems with fluid delivery or that fluid (e.g. bodily fluids such as blood) is accumulating within the patient.

[0016] In some embodiments, the output comprises the volume of fluid and the time period. In such examples, the output provides the value of the volume of fluid which passed through the fluid line over the time period and the value of the time period (i.e. the time period for which the volume of fluid has passed through the fluid line). For example, in embodiments wherein the output means is in the form of a display (as discussed in more detail below), the output means may display “50 ml in past 2 hours”. It will be appreciated that this differs to a device which simply displays “50 ml / h” or “650ml” as these two pieces of information alone do not allow a healthcare professional to determine the amount that has been received in a given time period. Using the apparatus according to this set of embodiments a healthcare professional can thus quickly and easily determine the volume of fluid which the patient has received or expelled in the given time.

[0017] In some embodiments, the output means comprise a display. The display may be a wired or wireless display. In such examples, the output means may display the output. The display may display the volume of fluid alongside the time period, such that healthcare professionals may observe how much fluid has passed through the fluid line in the time period. For example, the display may display text such as “120 ml in past 1 hour”. If the healthcare professional observes that too much (or not enough) fluid has passed through the fluid line over the time period, the healthcare professional may intervene.

[0018] In some embodiments, the output means comprises a speaker. The speaker may provide an audible output based on the volume of fluid and the time period. For example, the speaker may audibly announce “50 ml in past hour”. The apparatus may comprise a user operable component, e.g. a button, configured to cause the speaker to provide the output. In other embodiments, the speaker, or indeed any output means, may be configured to automatically provide the output e.g. periodically, e.g. upon at least one criterion being met. Such a criterion may, for example, comprise the fluid volume over the time period exceeding a threshold.

[0019] In some embodiments, the output means may comprise a transmitter. The transmitter may be configured to communicate with an external (i.e. separate) device (e.g. a pager, a tablet, a mobile phone). The external device may comprise a mobile device. The transmitter may communicate the output to the external device. This may allow for healthcare professionals to remotely monitor the status of the patient based on the output from the monitoring apparatus. The transmitter may operate according to a wireless communication standard as will be appreciated by those skilled in the art. For example, the transmitter may communicate with the external device via Bluetooth, or Wi-Fi, or Radio Frequency (RF) control.

[0020] In some embodiments, the time period may be the time since attachment of the fluid flow sensor to the fluid line. This may be detected automatically by the apparatus. For example, as soon as a fluid flow is detected by the flow sensor, the time period may begin. In some embodiments, the time period may be set by a user, e.g. a healthcare professional. This may be achieved, for example, by a user inputting a time period via a user interface of the apparatus. A healthcare professional may set any suitable time period. For example, the time period may be set at e.g. 1 hour, e.g. 2 hours, e.g. 3 hours, e.g. 4 hours. The time period may be a rolling time period. The time period according to any relevant embodiment herein may be a rolling time period.

[0021] In some embodiments, the monitoring apparatus may be further configured to determine if the volume of fluid exceeds a threshold for a pre-set time period (e.g. a time period as referred to previously). In some embodiments, the pre-set time period may be different to the time period. Exceeding such a threshold may indicate that the volume of fluid measured over the pre-set time period is abnormal (e.g. too much or too little fluid passed through the fluid line over the pre-set time period). The output may be based, in addition to the volume of fluid and the time period, on whether the threshold has been exceeded. Specifically, the output may comprise an indication that the threshold has been exceeded. In the exemplary case of an output means in the form of a display, a visual warning, e.g. the word “Warning” may be output on the display. Such embodiments may allow a healthcare professional to quickly and easily identify potential issues with fluid flow into or out of a patient.

[0022] In some embodiments, the output comprises an alert when the volume of fluid exceeds the threshold. The monitoring apparatus may provide an alert if the volume of fluid exceeds the threshold (e.g. too much or too little fluid) for the time period. The attention of healthcare professionals may therefore be more easily drawn to the patient when the alert is raised. For example, the pre-set threshold may be set at 100 ml in an hour, and the apparatus may determine that 135 ml has passed through the line in the past hour. In such a scenario, the apparatus would cause the output to indicate that the threshold has been exceeded. This may, for example, comprise issuing a warning on a display, or outputting an audible beep using a speaker. In some embodiments, the fluid flow sensor may connect to a port (e.g. a Luer, Luer-lock or Enfit hub) of the fluid line. In some embodiments, fluid may physically flow through the flow sensor. The fluid flow sensor may comprise an input port through which a fluid enters the fluid flow sensor and an output port through which fluid leaves the fluid flow sensor. The flow sensor may be arranged fluidically between the fluid line and a supply of fluid (e.g. an IV bag). In other embodiments, the fluid flow sensor may attach to an outside (e.g. an outer surface) of the fluid line and be capable of monitoring fluid flow therethrough (without physically contacting the fluid passing through the fluid line).

[0023] In some embodiments, the fluid line is one of: a cannula, a feeding tube, a catheter, or a surgical drain (e.g. a chest drain or an abdominal drain).

[0024] In some embodiments, the fluid flow sensor may be a volumetric fluid flow meter. In some embodiments, the fluid flow sensor may be a fluid velocity flow meter.

[0025] In some embodiments, the fluid flow sensor may be calibrated for a specific type of fluid. For example, the fluid flow sensor may be calibrated for saline solution when the corresponding fluid line is connected to a saline intravenous (IV) bag. In another example, the fluid flow sensor may be calibrated for blood when the corresponding fluid line is connected to a blood bag. The calibration of the fluid flow sensor may be achieved through manual input by a user into the monitoring apparatus. For example, a user may select the type of fluid being passes through the fluid flow sensor. This may, for example, be achieved through use of a user interface on the monitoring apparatus. In other embodiments, the fluid flow sensor may automatically determine the type of fluid passing therethrough (e.g. based on viscosity) and perform automatic calibration thereof.

[0026] In some embodiments, the monitoring apparatus comprises a plurality of fluid flow sensors. Each fluid flow sensor may be configured to be attached to a respective fluid line fluidly connected to the patient, and therefore measure respective fluid volume data for the respective fluid line. The monitoring apparatus may be configured to determine, using fluid volume data from each of the fluid flow sensors, a total volume of fluid which has passed through all of the fluid lines over the time period. In some embodiments, the monitoring apparatus comprises a controller. The controller may use the fluid volume data in order to determine the volume of fluid which has passed through the fluid line(s) over the time period. The controller may be a microcontroller. In examples where the monitoring device comprises a controller, the controller may be connected to the output means, and indeed the fluid flow sensor, via a wired or wireless connection.

[0027] The fluid flow sensor, controller (where provided) and output means may be provided as a single integrated device. In other embodiments, at least the fluid flow sensor may be a standalone device, which is connected to the controller (where provided) and output means, by a wired or wireless connection. Such embodiments may allow for the output means to be positioned in a more suitable location such that it can provide an output to a user. In the exemplary case of an output means in the form of a display, it may allow the display to be positioned where it can more readily be observed by a healthcare professional.

[0028] As set out above, the monitoring apparatus may be used to monitor fluid flow into or out of a patient. The Applicant has recognised that monitoring the fluid flow through (i.e. monitoring both fluid flow into and out of) a patient over a time period may also be advantageous in a healthcare setting. Accordingly, from a second aspect, the present invention provides a system for monitoring fluid flow through a patient, the system comprising:

[0029] an input fluid flow sensor configured to:

[0030] attach to an input fluid line fluidly connected to the patient; and measure input fluid volume data comprising data proportional to the volume of fluid which has passed through the input fluid line over a first time period;

[0031] an output fluid flow sensor configured to:

[0032] attach to an output fluid line fluidly connected to the patient; and measure output fluid volume data comprising data proportional to the volume of fluid which has passed through the output fluid line over a second time period; and

[0033] an output means; wherein the system is configured to determine: i) an input fluid volume based on the input fluid volume data measured over the first time period; ii) an output fluid volume based on the output fluid volume data measured over the second time period; and iii) a difference between the input fluid volume and the output fluid volume; and wherein the system is further configured to:

[0034] provide an output via the output means based on the difference.

[0035] In accordance with the second aspect, by determining a difference between the input volume and output volume of a patient, and providing an output based on the difference, the systems facilitates an accurate overall view of the fluid flow through the patient. This allows a healthcare professional to more easily monitor the net fluid flow through a patient, i.e. the fluid balance of a patient. As a result, healthcare professionals may be able to more readily intervene if, for example, it is determined that too little fluid volume is being output for the measured input fluid volume. This may indicate that fluid is building up within the patient and could negatively affect patient outcomes. In cases where a higher volume of fluid is being output than what has been input to the patient, this may indicate, for example, that the patient is suffering from an internal bleed.

[0036] The difference, determined by the system, may be the input fluid volume minus the output fluid volume. Where the difference is positive, this may indicate that there is a build-up of fluid within the patient and where the difference is negative, this may indicate that there is a loss of fluid within the patient. Equally, the difference may be the output fluid volume minus the input fluid volume. In this case, a positive difference may indicate that there is a loss of fluid within the patient and a negative difference may indicate that there is a build-up of fluid within the patient. Of course, it will be appreciated that for any given patient at any given time, the difference may be positive or negative, within thresholds, or indeed zero, and the patient may be clinically fine. It may only be when the magnitude of the difference exceeds a threshold that there is a cause for concern.

[0037] In some embodiments, the output comprises the difference. For example, in embodiments wherein the output means comprises a display, the display may output “Net fluid flow: +54 ml”. The output may comprise the first and second time periods. For example, where the output means comprises a display, the output means may output “Net fluid flow: +54ml over past 1 hour”. In such embodiments, at least where the difference together with the first and second time periods are output, a healthcare professional can assess the difference and the time period in which it is occurred. This may provide useful information, for example if a large difference has occurred over a short time period, as this may be more concerning that a similar difference that has occurred over a longer time period.

[0038] The output may comprise the input and / or output fluid volumes. Again, in the exemplary case wherein the output means comprises a display, the display may output “Fluid in: 43ml, Fluid out: 12 ml in past hour”. This may allow a healthcare professional to quickly determine the amount of fluid in and / or out of the patient.

[0039] In some embodiments, the output means is connected to the system (e.g. the input and / or output fluid flow sensor) via a wired or wireless connection.

[0040] In some embodiments, the output means comprises a display. In some embodiments, the output means comprises a speaker. The speaker may provide an audible output based on the difference.

[0041] In some embodiments, the output means comprises a transmitter. The transmitter may be configured to communicate with an external device (e.g. a pager, a tablet, a mobile phone). The transmitter may communicate the output to the external device. The external device may comprise a mobile device. Transmission to an external device may allow for healthcare professionals to remotely monitor the status of the patient based on the output from the system. The transmitter may operate according to a wireless communication standard as will be appreciated by those skilled in the art. For example, the transmitter may communicate with the external device via Bluetooth, or Wi-Fi, or Radio Frequency (RF) control.

[0042] In some embodiments, the system comprises a plurality of input fluid flow sensors. The input fluid flow sensor discussed above may be one of such plurality of input fluid flow sensors. Each of the input fluid flow sensors may comprise the features of the input fluid flow sensor of the second aspect described above. Each of the plurality of input fluid flow sensors may be configured to be attached to a respective input fluid line fluidly connected to the patient. In such embodiments, each input fluid flow sensor contributes to the input fluid volume data. Specifically, the input fluid volume is based on the sum of input fluid volume data over the first time period for each of the input fluid flow sensors. In other words, the input fluid volume data may be the linear sum of the outputs from each input fluid flow sensor. In such examples, the input fluid volume data may be proportional to the total volume of fluid which has passed through the input fluid lines.

[0043] In some embodiments, the system comprises a plurality of output fluid flow sensors. The output fluid flow sensor discussed above may be one of such plurality of output fluid flow sensors. Each of the output fluid flow sensors may comprise the features of the output fluid flow sensor of the second aspect described above. Each of the plurality of fluid flow sensors may be configured to be attached to a respective output fluid line fluidly connected to the patient. In such embodiments, each output fluid sensor contributes to the output fluid volume data. Specifically, the output fluid volume is based on the sum of the output fluid volume data over the second time period for each of the output fluid flow sensors. In other words, the output fluid volume data may be the linear sum of the outputs from each output fluid flow sensor. In such examples, the output fluid volume data may be proportional to the total volume of fluid which has passed through the output fluid lines.

[0044] Where a plurality of input fluid flow sensors is provided, the input fluid volume determined by the system may be the input fluid volume through all of input fluid flow sensors. Where a plurality of output fluid flow sensors is provided, the output fluid volume determined by the system may be the output fluid volume through all of the output fluid flow sensors. The difference between the input fluid volume and the output fluid volume may thus be the difference between the sum of the volume through each of the plurality of input fluid flow sensors and the sum of the volume through each of the plurality of output fluid flow sensors.

[0045] In some embodiments, the system may be configured to determine if the difference exceeds a threshold. The threshold may be set for a pre-set time period. Exceeding such a threshold may indicate that the difference between the input fluid volume and the output fluid volume is abnormal (i.e. the net flow through the input fluid flow line(s) and the output fluid flow line(s) is beyond a safe level). The threshold may be calculated automatically by the system (e.g. based on the volume of fluid being input to the patient) or the threshold may be manually input by a user. The output may be based on the threshold. For example, the output may indicate if the threshold has been exceeded. In examples where the output means comprises a display, the display may display “Alert” if the threshold is exceeded.

[0046] In some embodiments, the system comprises a controller. The controller may be configured to determine one or more of: the input fluid volume, the output fluid volume, the difference, and whether the difference exceeds the threshold. The controller may determine the threshold.

[0047] In embodiments with a plurality of input fluid flow sensors, a plurality of output fluid flow sensors, and where the system determines if the difference exceeds a threshold, the threshold may be adjusted based on the number of input fluid flow sensors and output fluid flow sensors. The adjustment may be done automatically by the system, or it may be manually adjusted by a user.

[0048] In embodiments with a plurality of input fluid flow sensors, each input fluid flow sensor may be configured to be connected to a different type of input fluid line. For example, one input fluid line may be a cannula, and another input fluid line may be a feeding tube. The system may therefore monitor the input fluid flow through each input fluid line.

[0049] In embodiments with a plurality of output fluid flow sensors, each output fluid flow sensor may be configured to be connected to a different type of output fluid line. For example, one output fluid line may be a catheter, and another output fluid line may be a surgical drain. The system may therefore monitor the output fluid flow through each output fluid line.

[0050] In some embodiments, the input fluid flow sensor(s) and the output fluid flow sensor(s) are configured to have an individual fluid designation that designates which fluid the respective fluid flow sensor will be measuring. The designation may be provided by a user. Alternatively, or in addition, the input / output fluid flow sensor(s) may determine the fluid designation automatically (e.g. based on one or more fluid parameters such as viscosity). Each fluid flow sensor may communicate the respective fluid designation to a controller, where provided. In some embodiments, the system may comprise a controller and the individual fluid designations from the input fluid flow sensor(s) and output fluid flow sensor(s) may be provided to the controller. In an example with two input fluid flow sensors, the controller may, for example, store that a first input fluid sensor is measuring input fluid volume data from a first fluid source (e.g. a saline bag), and a second input fluid sensor is measuring input fluid volume data from a second fluid source (e.g. a source of blood). This information may be used by the system when it determines the difference.

[0051] In some embodiments, the input fluid flow sensor(s) and the output fluid flow sensor(s) may be calibrated for specific types of fluid. The calibration may allow for the flow sensor(s) to accurately measure fluid volume data for specific types of fluid. For example, when one output fluid line is connected to a catheter bag, the corresponding output fluid flow sensor may be calibrated for urine. In another example, the output fluid line may be connected to the patient’s circulatory system, and so the corresponding output fluid flow sensor may be calibrated for blood. The calibration may be provided by a user, or the fluid flow sensor(s) may determine fluid type automatically (e.g. using viscosity), and perform calibration automatically. In examples with multiple input and / or output fluid flow sensors(s), the input / output fluid volume data may comprise data measured for different types of fluid, and the system may use the measured data when determining the total input / output fluid volume.

[0052] In some embodiments, the input fluid flow sensor(s) and the output fluid flow sensor(s) may communicate the input / output fluid volume data via a wireless connection(s). Wireless connection(s) may be performed according to wireless communication standards as will be appreciated by those skilled in the art. For example, the wireless connection(s) may be performed via Bluetooth, or Wi-Fi, or RF control.

[0053] In some embodiments, the input fluid flow sensor(s) and the output fluid flow sensor(s) may communicate the input / output fluid volume data via a wired connection(s). The wired connection may ensure that a consistent stream of input fluid volume data and output fluid volume data is provided to the system. This may be advantageous when wireless signal is particularly poor. In some embodiments, the input fluid flow sensor(s) and the output fluid flow sensor(s) may communicate the input / output fluid volume data via a combination of wired and wireless connection(s).

[0054] The first and second time periods may at least partially overlap in time. In some embodiments, the first and second time periods are the same time period. In other words, they may have the same start and end time. In such embodiments, the fluid flow in and the fluid flow out of the patient are measured for a common time period, i.e. the same period in time. In such embodiments, the first and second time periods may be considered to be a given time period. In other embodiments, the first and second time periods may be chronologically discontinuous (i.e. they do not overlap in time). Such embodiments may be of particular interest where it is known that a particular fluid flow into a patient will not likely be processed and leave the patient for a period of time, and thus measurement of fluid out before expiration of said time period may not be of particular interest.

[0055] The first and second time periods may have the same duration. The first and second time periods may be different durations. The first / second time periods may be 5, 30, 60, 90, or 120 minutes. The first / second time periods may be 1, 2, 6, 12, 24, 48, or 72 hours. The first / second time period may be specified by a user (e.g. input by a user into the system), or they may be a time since the input and output fluid flow sensors were attached to the input / output fluid lines. In some embodiments the first and / or second time periods may be since attachment of the input / output fluid flow sensor to the respective fluid line. This may be detected automatically by the system. In some embodiments, the first and / or second time periods may be set by a user, e.g. a healthcare professional. The same timings and features of the first and second time periods set out above may equally applied to the time period of the first aspect of the present invention.

[0056] In some embodiments, the display may display successively determined differences over a time period greater than that of the first or second time periods. Thus, for example, whilst the difference may be determined every five minutes, the display may show the successively determined differences over the past hour. This may advantageously allow for healthcare professionals to observe the changes in the fluid balance of the patient over a longer time period. In some embodiments, the output means may comprise an alarm which is configured to provide an alert when the system determines that the difference exceeds the threshold. In some examples, the alert may comprise an audible sound. The alert may comprise a visual indicator (e.g. a flashing light).

[0057] In some embodiments, the system may determine the difference at regular intervals. In some examples, the interval may be once every five minutes. It may be every thirty minutes. It may be every hour. It may be every six hours. The interval may be set by a user of the system.

[0058] In some embodiments, the output means may provide the output to an external device. The external device may be associated with a healthcare professional. The external device may be a mobile device, such as a tablet, a laptop, a mobile phone (i.e. a smartphone or otherwise), or a pager. The output means may send a message to the external device when the predetermined threshold has been exceeded. Therefore, when a healthcare professional is carrying or is nearby the external device and receives the message, the healthcare professional can take decisive action on behalf of the patient.

[0059] In any of the embodiments described above relating to the first or second aspects of the invention, the fluid flow sensor, the input flow sensor and / or the output fluid flow sensor may comprise any suitable means for measuring data proportional to the volume of fluid. In some embodiments, it may comprise mechanical fluid flow sensor, which comprises a gear, rotor, impeller or turbine which is caused to move in response to fluid flowing therethrough. In some embodiments, the fluid flow sensor may comprise a paddle wheel sensor.

[0060] It may be advantageous for a user (e.g. a healthcare professional) to be able to request data produced by the monitoring apparatus or system for a selected time in the past - i.e. request historic data generated by the monitoring apparatus or system. For example, a user may wish to see historic data captured by the system or monitoring apparatus over a time period that happened several hours ago. In such embodiments, the historic data may comprise the output (e.g. the output that is based on the volume of fluid and the time period, in the case of the monitoring apparatus, or the output based on the difference, in the case of the system). The data may also comprise the input fluid volume and / or the output fluid volume.

[0061] Therefore, in some embodiments of the first aspect of the invention, the monitoring apparatus further comprises a storage means or is configured to communicate data with a remote storage means, and the monitoring apparatus is further configured to:

[0062] store data comprising at least one of the fluid volume data and the output, together with an associated time, in the storage means or remote storage means thereby forming historic data;

[0063] receive a request for historic data for a time and / or time period; and

[0064] in response, provide, via the output means, the historic data that corresponds to the requested time and / or time period.

[0065] For example, the apparatus may be configured to store data comprising the fluid volume data and the associated time the fluid volume data was measured. In addition or alternatively, the apparatus may be configured to store data comprising the output and the associated time the output was generated. The storage means (comprised in the apparatus) may be considered to be a local storage means. The remote storage means may not be part of the fluid flow sensor, and / or any controller which the sensor directly communicates with.

[0066] In some embodiments, instead of the monitoring apparatus receiving the request for historic data and providing said data via the output means, a request for historic data may instead be provided directly to the remote storage means (e.g. via any suitable interface) and the requested historic data may be output accordingly, e.g. on an output device that is remote to the apparatus, e.g. on a computer / tablet etc. In this instance, the ability for the apparatus to receive the request and provide the historic data may be omitted.

[0067] In some embodiments of the second aspect of the invention, the system further comprises a storage means or is configured to communicate data with a remote storage means, and the system is further configured to:

[0068] store data comprising at least one of: the input fluid volume data, the output fluid volume data, the difference and the output, together with an associated time, in the storage means or the remote storage means thereby forming historic data; receive a request for historic data for a time and / or time period; and

[0069] in response, provide, via the output means, the historic data that corresponds to the requested time and / or time period.

[0070] For example, the system may be configured to store data comprising the input fluid volume data and the associated time the input fluid volume data was measured. In addition or alternatively, the system may be configured to store data comprising the output fluid volume data and the associated time the output fluid volume data was measured. In addition or alternatively, the system may be configured to store data comprising the difference and the associated time the difference was determined. In addition or alternatively, the system may be configured to store data comprising the output and the associated time the output was determined. The storage means (comprised in the system) may be considered to be a local storage means. The remote storage means, in some embodiments, may be considered to form part of the system. In being remote, the remote storage means may not form part of the input fluid flow sensor / output fluid flow sensor and / or a controller which they may communicate directly with.

[0071] In some embodiments, instead of the system receiving the request for historic data and providing said data via the output means, a request for historic data may instead be provided directly to the remote storage means (e.g. via any suitable interface) and the requested historic data may be output accordingly, e.g. on an output device that is remote to the system, e.g. on a computer / tablet etc. In this instance, the ability for the system to receive the request and provide the historic data may be omitted.

[0072] In other words, any data which a user may wish to have access to may be stored and time-stamped.

[0073] In any of the embodiments described above, the remote storage means may comprise a remote server comprising a memory, on which the data is stored. The remote storage means may be accessed via a (e.g. standardised) healthcare data interface. For example, the interface may comprise (and / or comply with) Health Level 7 (HL7) or Fast Healthcare Interoperability Resources (FHIR). This interface may facilitate communication with a patient record system (e.g. comprising Epic, Cerner, Allscripts, Medidata, etc), sometimes referred to as an electronic patient record (EPR) or an electronic health record (EHR). Transferring data in this manner to a remote storage means may provide improved access to the data across a range of healthcare professionals. Any of the data generated in apparatus and / or systems set out herein may be transferred over to and stored on the remote storage means using the interfaces and record systems set out above. The data may be transferred in its raw form, e.g. in the form of volumes and associated time stamps, and / or in the form of processed data, e.g. including volumes, rates of change, etc and associated time periods which may be selected by an operator of the apparatus / system.

[0074] In some embodiments of the apparatus, the historic data comprises the fluid volume data and the output stored together with the associated time as respective elements of the historic data, and the apparatus is further configured to:

[0075] receive a request for one of the respective elements of the historic data for a time and / or time period; and

[0076] in response, provide, via the output means, the requested element of the historic data that corresponds to the time and / or time period.

[0077] In some embodiments of the system, the historic data comprises two or more of: the input fluid volume data, the output fluid volume data, the difference and the output, together with an associated time, as respective elements of the historic data, and the system is be further configured to:

[0078] receive a request for one of the respective elements of the historic data for a time and / or time period; and

[0079] in response, provide, via the output means, the requested element of the historic data that corresponds to the time and / or time period.

[0080] Thus, a user may be able to select a particular element of the historic data (e.g. only input fluid volume data), when the historic data comprises more than one kind of data, for a selected time / time period.

[0081] The storage means may be a non-volatile memory, such as a solid-state memory (e.g. a flash memory). In some embodiments, the requested time period is a portion, or all, of the time period for which data has been recorded in the storage means.

[0082] The system or monitoring apparatus may be configured to store the data from a point at which the monitoring apparatus or system is initially activated.

[0083] The system or monitoring apparatus may be configured to store the data from a point at which the fluid flow sensor (in the case of the apparatus) or the input fluid flow sensor and / or the output fluid flow sensor (in the case of the system) was attached to suitable fluid flow line (e.g. an input fluid line and / or an output fluid line).

[0084] The time period for which historic data is request may be continuous in time or discontinuous in time. In one embodiment, the time period may correspond to two or more discontinuous subsections of the period for which data is stored. For example, the time period requested may correspond to “10am to 11am and 3pm to 4pm”. Thus, it will be seen that a user can input a requested time or time period (e.g. “1pm to 3pm today”, or “the past three hours”), and in response can be provided with the output that was recorded during that time period.

[0085] In embodiments in which the output is stored, the monitoring apparatus or system may store the output as it is generated. The same may apply to the fluid volume data, input fluid volume data, output fluid volume data and the difference.

[0086] In some embodiments, the output means also provides, via the output means, the requested time or requested time period of the requested historic data. In such embodiments, the monitoring apparatus or system therefore provides both the historic data selected and the associated time / time period. Thus, in an illustrative example where the historic data comprises the difference, the monitoring apparatus or system receiving the requested time or requested time period provides the difference and the requested time or requested time period. The system may therefore provide, via the output means, an output which may be displayed (e.g. by a display) as “+350ml from 11am to 12pm”. This may advantageously make it easier for a user of the monitoring apparatus or the system to review changes in fluid balance by having immediate access to both the historical difference and the time period over which it was recorded. In some embodiments, the monitoring apparatus or the system comprises a user interface, and the time / time period for the historic data is received by the monitoring apparatus or the system from a user using the user interface.

[0087] The Applicant has recognised that in embodiments comprising a controller that communicates wirelessly with a fluid flow sensor (in the case of a monitoring apparatus), or indeed an input fluid flow sensor or output fluid flow sensor (in the case of a system), the sensors may be interchanged between different controllers. In such a situation, it may become necessary to associate the respective sensor with the controller, in order for the apparatus / system to function. Thus, in embodiments where the monitoring apparatus comprises a controller, the fluid flow sensor may comprise an identification means, and the controller may be configured to obtain information from the identification means and associate the fluid flow sensor with the controller.

[0088] In embodiments where the system comprises a controller, the input fluid flow sensor and / or the output fluid flow sensor may comprise an identification means, and the controller may be configured to obtain information from the identification means and associate the input and / or out fluid flow sensor with the controller.

[0089] In associating the fluid sensor, input fluid sensor and / or output fluid sensor with the controller, this may comprise facilitating further communication therebetween, e.g. the communication of fluid volume data, outputs etc. For example, a communication interface and / or protocol may be established between the fluid sensor / input fluid sensor / output fluid sensor and the controller, thereby facilitating further communication, e.g. comprising the communication of data such as the fluid volume data, output, input fluid volume data, output fluid volume data, the difference. In some embodiments, association of the fluid sensor, input fluid sensor and / or output fluid sensor with the controller may be considered to be a pairing of the respective sensor with the controller. Following pairing, further communication, e.g. of data relating to measurements performed by the sensor, may be permitted.

[0090] Thus, in accordance with embodiments of the invention, the fluid flow sensor(s) (i.e. of the monitoring apparatus or of the system) can be associated (e.g. paired) with the controller using the identification means. This is particularly advantageous in embodiments where the fluid flow sensor(s) operate via wireless connections. A user can use the identification means to easily pair the sensor(s) with the controller when a new patient is using the apparatus / system.

[0091] In some embodiments, the identification means comprises a wireless communication means configured to communicate with the controller. The wireless communication means may operate according to a Near-field Communication (NFC) protocol, and the controller is connected to a reader configured to scan the wireless communication means. A user may therefore scan each fluid flow sensor on the reader to associate the fluid flow sensors with the controller, and therefore the apparatus / system. The wireless communications means may comprise a radio frequency identification tag (RFID Tag). The wireless communication means may be configured to only establish communication with, i.e. be readable by, the reader when it is within a range of less than less than 1 m, e.g. less than 0.5 m, e.g. less than 10 cm, e.g. less than 1 cm.

[0092] In some embodiments, the identification means comprises a machine-readable label. The machine-readable label may comprise a QR code, barcode, or other known label types. In such embodiments, the controller is connected to a reader which comprises a means for scanning the machine-readable label to associate the fluid flow sensor(s) with the controller. A user may therefore associate the fluid flow sensor(s) with the controller by scanning the labels with the reader. In embodiments where the apparatus or the system comprises a controller, associating the fluid flow sensor (in the case of the apparatus) or the input fluid flow sensor and / or the output fluid flow sensor (in the case of the system) with the controller comprises identifying the fluid flow sensor(s) as an input fluid flow sensor or an output fluid flow sensor to the controller.

[0093] The Applicant has appreciated that the relevance of outputs in the monitoring apparatus or system set out above may have at least some dependency on characteristics of the patient being monitored. Thus, in some embodiments, where a threshold is utilised, the monitoring apparatus or system may be configured to receive one or more patient parameters, and the threshold may be calculated at least in dependence upon the one or more patient parameters. The patient parameters may comprise a patient weight and / or a patient height. The patient parameters may comprise other parameters for the patient, for example one or more of: age, sex, body mass index (BMI), body surface area, renal function markers (creatinine, estimated glomerular filtration rate “eGFR”), cardiac function markers, diagnosis / condition, medications, surgical procedure type, time since procedure, and clinical protocol selection (e.g. post-cardiac surgery, sepsis resuscitation, renal protection, paediatric, burns, liver failure, critical illness).. Thus, the system may be provided with parameters specific to the patient, and the threshold may be calculated based on those parameters. In the exemplary case of a patient that has a greater height and weight, it may be acceptable for said patient to have a greater input fluid volume, as compared to a patient that has a smaller height and weight. Accordingly, the threshold can be customised to suit the patient in question, as it will be appreciated that patients which, for example, are taller or have a greater weight may be expected to have a nominal threshold that is larger than a shorter or lighter patient.

[0094] In any of the embodiments disclosed herein, in respect of the first and / or second aspect, the apparatus or system may be configured to determine a rate of change of volume (e.g. volume, input volume and / or output volume) and / or rate of change of the difference. Where an output is provided, the output may be based on the rate of change of volume / difference. For example, the monitoring apparatus may output a rate of change and an associated time period, e.g. “Rate of change increase: 50 ml / h in past 2 hours”. Where a threshold is utilised, the threshold may comprise a rate of change of volume (in the exemplary case relating to the monitoring apparatus) or difference (in the case of the system). In this instance, for example, the threshold may be a rate of change of 25 ml / h. When a volume through the flow sensor is detected to have a rate of change of greater than 25 ml / h for a given period, e.g. 1 hour, this may be indicative of a medical concern and a suitable output, e.g. an alert or alarm, may be provided. Detecting this may be indicative of acute deterioration. Monitoring rate of change, as opposed to total volume / difference, may facilitate earlier detection of fluid loss, e.g. when blood initially begins gushing out of a patient. It will be appreciated that these features relating to rate of change can be equally applied to the monitoring apparatus and the system set out previously and any parameters measured / determined therein.

[0095] Exemplary cases include a surgical drain suddenly outputting 50 ml / h more than it was previously, which may indicate potential active bleeding. Similarly, urine output dropping by 20 ml / h may indicate renal disfunction. The rate of change of the difference (i.e. the net fluid flow) may indicate fluid overload developing. The threshold may comprise a threshold rate of change of the difference (between the input fluid volume and the output fluid volume).

[0096] Where rate of change is being monitored, the time period (which the output may be based on) may be smaller, for example of the order of minutes, as opposed to hours, to facilitate early indication. A user may be able to select rate of change monitoring, and the time period over which analysis is performed, e.g. by the apparatus or system, may be pre-set, e.g. at less than 15 minutes, e.g. less than 10 minutes, e.g. less than 5 minutes, e.g. less than 1 minutes.

[0097] In any of the embodiments described herein, the time period, first time period and / or second time period may be a rolling time period any of which may comprise a e.g. 12 hour rolling time period, e.g. a 24 hour rolling time period, e.g. a 48 hour rolling time period. In this sense, the volume data may be continually monitored. A time period, e.g. of 12 hours, 24 hours, etc, may be considered to correspond to a cumulative time period, as opposed to a more instantaneous time period, e.g. of 5 minutes, 30 minutes etc.

[0098] In any embodiments relating to thresholds, the threshold(s) comprise a plurality of thresholds, each of the plurality of thresholds corresponds to a different time window. For example, a first threshold may be set for a first time window (e.g. a time period corresponding to an hour), and a second threshold may be set for a second time window (e.g. a time period corresponding to 24 hours). For example, the first threshold may be a volume of 50 ml for 1 hour, whereas the second threshold may be set at 500 ml for 24 hours. Thus, in a given day, the apparatus and / or system may provide an output, e.g. in the form of an alert, if a patient exhibits 50 ml of fluid loss (in the case of monitoring fluid output) over an hour, and similarly if they exhibit more than 500 ml over the course of 24 hours, another output may be generated. This may, effectively, facilitate short and long -term monitoring of the fluid flow. The features set out above may be equally applied to volume, input volume and / or output volume, but may also be applied to any suitable parameter, for example the rate of change thresholds set out above, differences in input fluid volume and output fluid volume, etc.

[0099] In any of the embodiments described above, the threshold(s) may be set based on a type of fluid the sensor (e.g. the fluid flow sensor, the input fluid flow sensor and / or the output fluid flow sensor) is monitoring. The type of fluid being monitored by the sensor may be input by an operator and / or be detected by the sensor (e.g. by detecting viscosity). The threshold which is specific for the type of fluid may be manually input and / or adjusted by an operator (e.g. a healthcare professional) and / or the threshold may be automatically set by the apparatus and / or system. For example, the apparatus and / or system may comprise a record of different fluids and associated thresholds, upon being provided with a type of fluid (e.g. through manual input or automatic detection), the apparatus and / or system may interrogate the record and set the threshold(s) accordingly. An operator may be able to manually adapt the pre-stored threshold(s) as needed. For example, in the case of monitoring blood, the threshold may be set to be any measurement exceeding 500 ml / h, for urine output the threshold may be set at anything less than 30 ml / h, and for a surgical drain, the threshold may be set at anything more than 200 ml / h.

[0100] The Applicant has also appreciated that the above embodiments extend to computer software.

[0101] Accordingly, from a third aspect, the invention provides a non-transitory computer readable storage medium comprising instructions for execution by a processor of a system for monitoring net fluid flow through a patient, the system comprising:

[0102] an input fluid flow sensor configured to:

[0103] attach to an input fluid line fluidly connected to the patient; and measure input fluid volume data comprising data proportional to the volume of fluid which has passed through the input fluid line over a first time period;

[0104] an output fluid flow sensor configured to:

[0105] attach to an output fluid line fluidly connected to the patient; and measure output fluid volume data comprising data proportional to the volume of fluid which has passed through the output fluid line over a second time period; and

[0106] an output means;

[0107] wherein the instructions, when executed, cause the system to:

[0108] (i) determine an input fluid volume based on the input fluid volume data measured over the first time period; (ii) determine an output fluid volume based on the output fluid volume data measured over the second time period; and

[0109] (iii) determine a difference between the input fluid volume and the output fluid volume to; and

[0110] provide an output via the output means based on the difference.

[0111] From a fourth aspect, the invention provides a non-transitory computer-readable storage medium comprising instructions for execution by a processor of an apparatus for monitoring fluid flow into or out of a patient, the monitoring apparatus comprising:

[0112] a fluid flow sensor configured to:

[0113] attach to a fluid line fluidly connected to the patient; and measure fluid volume data comprising data proportional to the volume of fluid which has passed through the fluid line of a time period; and an output means;

[0114] wherein the instructions, when executed, cause the monitoring apparatus to:

[0115] determine, using the fluid volume data, a volume of fluid which has passed through the fluid line over the time period; and

[0116] provide an output via the output means based on the volume of fluid and the time period.

[0117] In any of the aspects or embodiments described above, the time period, first time period and / or second time period, as appropriate, may be selected by a user. For example, if a user is interested in fluid flow over the past 1 hour, the user of the apparatus or system may suitably select a time period of 1 hour, e.g. using a user interface of the apparatus or system.

[0118] Features of any aspect or embodiment described herein may, wherever appropriate, be applied to any other aspect or embodiment described herein. For example, any of the features of any embodiment of the monitoring apparatus may be equally applied to, as appropriate, any embodiment of the system. Where reference is made to different embodiments or sets of embodiments, it should be understood that these are not necessarily distinct but may overlap.

[0119] BRIEF DESCRIPTION OF THE DRAWINGS

[0120] Some exemplary embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 is a schematic drawing of an exemplary monitoring apparatus according to an embodiment of the present invention;

[0121] FIG. 2 is a schematic drawing of an exemplary monitoring system according to an embodiment of the present invention;

[0122] FIG. 3 is a schematic drawing of another exemplary monitoring system according to another embodiment of the present invention;

[0123] FIG. 4 is a schematic drawing of an exemplary output means, in accordance with an embodiment of the present invention, communicating with an external device;

[0124] FIG. 5 is a schematic drawing of an exemplary monitoring system according to an embodiment of the present invention;

[0125] FIG. 6 is a schematic drawing of exemplary input and output fluid flow sensors, and an exemplary controller according to an embodiment of the present invention; and

[0126] FIG. 7 is a flowchart showing an exemplary method performed by the monitoring system according to an embodiment of the present invention.

[0127] DETAILED DESCRIPTION

[0128] In many healthcare settings, such as a hospital ward or a surgical theatre, a patient may be connected to one or more fluid sources which will replenish fluids such as blood, antibiotics, etc. These may be provided via fluid lines such as intravenous (IV) lines, feeding tubes, etc. A patient may also expel fluid via fluid lines such as catheters, tube drains, etc. It can be difficult for healthcare professionals to get an accurate and up to date reading of the volume of fluid input to, and / or output from, a patient over a period of time. It can also take healthcare professionals a long time to notice that a patient is expelling too little or too much fluid for a given volume of input fluid over the course of treatment using current methods. Accumulating fluid in the patient can cause serious harm to the patient, for example by putting additional strain on the cardiovascular system. It is therefore important to find a way of precisely and timely monitoring the amount of fluid that flows into and / or out of a patient over a course of treatment.

[0129] Fig. 1 is a schematic diagram of a monitoring apparatus 1 (hereinafter referred to as “the apparatus 1”) in accordance with an embodiment of the present invention. In the embodiment depicted, the apparatus 1 monitors the volume of fluid that flows into a patient 6 over a time period. Whilst the apparatus 1 is depicted as monitoring the fluid flow into a patient, it will be appreciated that the apparatus 1 may equally be used to monitor the fluid flow out of a patient.

[0130] As depicted in Fig. 1, the apparatus 1 comprises a fluid flow sensor 2 attached to a fluid line 4. The fluid flow sensor 2 may be attached in line with the fluid line 4, such that fluid flows through the flow sensor 2. The fluid line 4 is fluidly connected to the patient 6. One or more sources of fluid (not shown), such as IV bags containing fluids like blood, saline, etc., may fluidly connect to the fluid line 4. Fluid therefore flows from the fluid source(s) through the fluid line 4 and into the patient 6. Though not depicted in Fig. 1, the fluid line 4 may instead be arranged to carry fluid out of the patient 6 and into a fluid receptacle, such as a fluid waste bag. The apparatus 1 is therefore also capable of monitoring the volume of fluid that flows out of the patient 6 over a time period.

[0131] The fluid flow sensor 2 measures fluid volume data over a time period. The time period is a period of time where fluid is flowing through the fluid line. For example, the time period may be 1 hour. This time period should be understood as purely exemplary, and the skilled person will understand that to the fluid volume data may be measured over any suitable time period. The time period may be a rolling time period, i.e. it may be a rolling hour. Fluid volume data is data which is proportional to the volume of fluid which has passed through the fluid line over a time period. For example, the fluid flow sensor 2 may be a volumetric flow rate meter, and the fluid volume data may therefore comprise a volumetric fluid flow rate (e.g. in cubic millimetres per hour). In other embodiments, however, the fluid flow sensor 2 may instead be a fluid velocity meter, and the fluid volume data in this example may thus comprise a fluid velocity (e.g. millimetres per second).

[0132] The monitoring apparatus 1 uses the fluid volume data to determine a volume of fluid which has passed through the fluid line 4 over the time period. For example, when the fluid volume data comprises a volumetric fluid flow rate, the monitoring apparatus 1 may determine the volume of fluid by calculating the product of the volumetric flow rate, and the time period. If the fluid volume data instead comprises a fluid velocity, the monitoring apparatus may determine the volume of fluid by calculating the product of the fluid velocity, a cross-sectional area of a portion of the flow sensor 4 through which the fluid is flowing, and the time period.

[0133] As is also depicted in Fig. 1, the apparatus 1 also comprises an output means 8. The output means 8 is used to provide an output based on both the volume of fluid and the time period. The output means 8 is shown in Fig. 1 to be separate from the fluid flow sensor 2. However, in some embodiments, the output means 8 is physically connected to the fluid flow sensor 2, such that the output means 8 and the fluid flow sensor 2 form an integrated unit within the apparatus 1. In the example of Fig. 1, the output means 8 comprises a display 10 and a speaker 12. It should be understood that the output means 8 may be provided with only one of the display 10 or speaker 12, or neither of these.

[0134] The output, provided via the output means 8, may comprise the volume of fluid and the time period, such that these values are provided to a user such as a healthcare professional for monitoring of the fluid delivery to the patient 6. For example, the output means 8 may use the display 10 to display the volume of fluid alongside the time period (e.g. 500 millilitres in past 1 hour). Healthcare professionals may therefore easily observe the volume of fluid that has passed through the fluid line and into the patient 6 over the time period. This is in contrast to existing apparatus, where a healthcare professional may only be aware of a flow rate set at the fluid source, or a total fluid volume without any context as to the time in which it has been delivered.

[0135] The monitoring apparatus 1 may, in some embodiments, determine if a threshold has been exceeded for a time period. The threshold may indicate that insufficient, or too much, fluid has been delivered to the patient 6 via the fluid line 4 as measured by the fluid flow sensor 2. For example, if the patient 6 requires 1000 millilitres of fluid to be delivered over the course of 1 hour, the threshold is may be exceeded if the monitoring apparatus 1 determines that only 500 millilitres (an example value) has been delivered over the time period of 1 hour. The monitoring apparatus 1 may use the output means 8 to provide an alert to healthcare professionals if the threshold is exceeded. The threshold may be input by a user of the apparatus 1, or the apparatus may determine the threshold based on information received from the fluid flow sensor 2. A threshold may be exceeded by being greater than or less than a pre-set value, depending on whether the apparatus 1 is being used to monitor fluid flow into or out of a patient. In addition or alternatively to outputting information using the display 10, the output, be that an output comprising volume and time period, or an output based on whether a threshold has been exceeded, may be provided using the speaker 12 in which an audible announcement may be provided.

[0136] The threshold used by the monitoring apparatus 1 can be based on characteristics of the patient. Accordingly, in some embodiments, the monitoring apparatus 1 may be configured to receive one or more patient parameters, and the threshold may be calculated in dependence upon at least the received patient parameters. The parameters may be input to the monitoring apparatus 1 via a user interface (e.g. by the user of the apparatus). In one example, the patient parameters comprise a patient weight and a patient height, though it will be appreciated that the patient parameters may comprise only one of these, or include other suitable patient parameters. In an example where a patient has a greater height and weight, the volume of fluid which is acceptable to enter and / or exit the patient may be appreciably different compared to a patient with a lower height and weight, because differently sized patients can have different fluid balance requirements. Therefore, the threshold for a larger patient will be different to a threshold for a patient having a lower height and weight. Indeed, the threshold for the patient having the greater height and weight may be larger than the threshold for the patient that has a lower height and weight. Of course, the specifics of the patient using the monitoring apparatus will impact the value of the threshold as calculated based on the patient parameters. It will be appreciated that the ability for the apparatus to determine the threshold based on patient parameters may be equally applied to the system(s) discussed below.

[0137] While measuring the volume of fluid that enters or exits a patient individually is advantageous in healthcare settings, it is also useful to be able to monitor the volume of fluid that passes through a patient (i.e. the volume of fluid that enters and exits a patient) over a time period. Aspects of the above described monitoring apparatus can therefore be combined to achieve this kind of monitoring, and will be discussed in more detail with reference to Figs. 2 and 3 below.

[0138] Fig. 2 shows an example monitoring system 3 for monitoring the flow of fluid into and out of a patient. As in Fig. 1, Fig. 2 shows a patient 6 fluidly connected to an input fluid line 4, where an input fluid flow sensor 2 is attached thereto. The input fluid line 4 may be fluidly connected to one or more fluid sources (not shown) for the patient 6. Similar to the monitoring apparatus 1, the input fluid flow sensor 2 measures input fluid volume data, which comprises data proportional to the volume of fluid which has passed through the input fluid line 4 over a first time period.

[0139] In addition, the patient 6 is connected to an output fluid line 16 with an output fluid flow sensor 14 attached thereto. The output fluid flow sensor 14 measures output fluid volume data which is proportional to the volume of fluid which has passed through the output fluid line 16 over a second time period.

[0140] Using the input fluid volume data, the monitoring system 3 determines an input fluid volume over a first time period. The output fluid volume data is used by the monitoring system 3 to determine an output fluid volume over a second time period. Both the input and output fluid volumes may be determined by the monitoring system 3 in a similar fashion to how the monitoring apparatus 1 determines the volume of fluid described above. Depending on the scenario, the first and second time periods may overlap in time, or they may not (i.e. they may be chronologically discontinuous). The first and second time periods may have the same duration, such that the monitoring system 3 can monitor the input volume and the output volume determined over the same quantity of time. The first time period and the second time period may completely overlap in time, such that the monitoring system 3 simultaneously monitors the input and output volumes. In such embodiments, the first and second time periods may have the same start and end times. In such embodiments, the first and second time periods may each be considered to be a given time period.

[0141] Once the input fluid volume and output fluid volume are determined, the monitoring system 3 determines a difference between the two volumes. For example, the monitoring system 3 may subtract the output fluid volume from the input fluid volume. The difference may be positive, negative, or zero, depending on the values of the input and output fluid volumes.

[0142] As depicted in Fig. 2, the system 3 may comprise a controller 18, which may, for example, be a microcontroller. The controller may be located on (i.e. physically connected to) the input fluid flow sensor 2 or the output fluid flow sensor 14. Alternatively, the controller 18 may be distinct from (i.e. not physically connected to) the fluid flow sensors 2, 14. The controller 18 may be used by the monitoring system 3 to perform some or all of the steps required when operating the monitoring system 3. For example, the controller 18 may be used by the monitoring system 3 to determine one or both of the input volume and output volume. The controller 18 may also be used to determine the difference between the two volumes.

[0143] As with the monitoring apparatus 1 , the monitoring system 3 comprises the output means 8. The output means 8 is used by the monitoring system 3 to provide an output based on the determined difference. The output, provided by the output means 8, may comprise the determined difference, and in some examples the output means 8 uses the display 10 to display the difference. The speaker 12 may be used to provide an audible output based on the difference, such as announcing the difference. As discussed previously, outputting the difference may allow a healthcare professional to quickly and easily determine the net fluid flow through a patient allowing them to take appropriate action as required. The difference may be output together with the first and / or second time periods. Again, this may provide sufficient information to the healthcare professional to make a quick judgement as to the current fluid flow situation of the patient.

[0144] The controller 18 may be located on (i.e. be physically connected to) the output means 8. In some embodiments, the controller 18 and the output means 8 may be part of a single device, e.g. contained within a single housing. In examples where the output means 8 comprises the display 10, the controller 18 may be located on (i.e. be physically connected to) the display 10. In other embodiments, the controller 18 may be separate from the output means 8 and / or the display 10 and be part of a separate device.

[0145] In addition to determining the difference between an input fluid volume and an output fluid volume, the monitoring system 3 (or the controller 18 thereof) may establish if the difference exceeds a threshold. Exceeding the threshold may indicate that the difference is beyond a safe value, where for example the patient 6 is losing too much fluid through the output fluid line 16 for the amount of fluid provided through the input fluid line 4, or wherein too much fluid is collecting with the patient 6. In some embodiments, the threshold may be calculated by the monitoring system 3 (or the controller 18 thereof) and stored in memory. In some embodiments, a user may determine the threshold and input the threshold to the system 3. The threshold may change depending on the first and / or second time period.

[0146] In some scenarios, it is possible for the patient 6 to be fluidly connected to multiple input and output fluid lines during the course of a treatment. Nevertheless, monitoring the volume of fluid passing through the patient 6 is still important. Fig. 3 is a schematic drawing showing another monitoring system 5, in accordance with an embodiment of the present invention, which is similar to the monitoring system 3 of Fig. 2 except it is configured to support multiple fluid inputs and outputs. Like references are used for like elements from Figs. 1 and 2.

[0147] Fig. 3 shows the patient 6 fluidly connected to first, second, and third input fluid lines 2a, 2b, 2c to deliver a set of fluid sources (not shown for simplicity) to the patient 6. While three input fluid lines 2a-c are shown in Fig. 3, it will be appreciated that the patient 6 may have fewer input fluid lines (i.e. only one as seen in Fig. 2, or only two), or more input fluid lines (i.e. more than three) depending on the needs of the patient 6. The input fluid lines 2a-c may each be cannulas, feeding tubes, or any other kind of input fluid line. Each of the input fluid lines 2a-c may be a unique type of input fluid line, or one or more of the input fluid lines 2a-c may be of the same type of fluid line.

[0148] Similarly to what has been described above with relation to Fig. 2, attached to each input fluid line 4a-c is a corresponding input fluid flow sensor 2a-c. The input fluid flow sensors 2a-c are configured to measure input fluid volume data, which in this example comprises the outputs from each input fluid flow sensor 2a-c. For example, the first input fluid flow sensor 2a is attached to the first input fluid line 4a, and the first input fluid flow sensor 2a is configured to measure respective input fluid volume data. The respective input fluid volume data may comprise a volumetric flow rate of fluid that flows through the first input fluid line 4a at the location of the first input fluid flow sensor 2a over a first time period. Alternatively, the input fluid flow sensors 2a-c may each comprise a flow meter which measures a fluid velocity of fluid through each corresponding input fluid line 4a-c. Alternatively, the input fluid flow sensors 2a-c may be able to directly measure the volume of fluid that flows through the respective input fluid line 4a-c during the first time period. Fig. 3 also shows the patient 6 fluidly connected to first and second output fluid lines 16a, 16b which allow for fluid to be removed from the patient 6. At least one of the first and second output fluid lines 16a, 16b may comprise a catheter connected to a catheter bags, and at least one of the first and second output fluid lines 16a, 16b may comprise a surgical drain (e.g. a chest drain or abdominal drain). The skilled person will appreciate that any type of output fluid line may be used, as appropriate. The skilled person will appreciate that the patient may have fewer output fluid lines (i.e. only one as shown in Fig. 2), or more output fluid lines (i.e. more than two) depending on the needs of the patient. Attached to each output fluid line 16a, 16b are respective output fluid flow sensors 14a, 14b. The output fluid flow sensors 14a, 14b are configured to measure output fluid volume data, which in this example comprises the outputs from each output fluid flow sensor 14a, 14b, as described above in relation to Figs. 1 and 2. For example, the first output fluid flow sensor 14a measures respective output fluid volume data. This may comprise a volumetric flow rate of fluid that flows through the output fluid line 16a at the location of the first output fluid flow sensor 14a over the second time period. The output fluid flow sensors 14a, 14b may each be a flow meter which directly measure a fluid velocity. Alternatively, the output fluid sensors 14a, 14b may be able to directly measure the respective volume of fluid that flows through the respective output fluid line 16a, 16b over the second time period.

[0149] The input fluid flow sensors 2a-c and the output fluid flow sensors 14a, 14b are in this example connected to the controller 18. Each flow sensor 2a-c, 14a, 14b are connected to the controller 18 via a wired or wireless connection, or a combination thereof. For example, when a wired connection is used, the first input fluid flow sensor 2a is connected to the controller 18 using a wire, which may be dedicated to the first input fluid flow sensor 2a. The same may apply to the other flow sensors.

[0150] Any suitable part of the system 5 may determine and sum the total input volume and determine and sum the total output volume and determine the difference therebetween. In the example shown in Fig. 3, the controller 18 is configured to receive the input fluid volume data and the output fluid volume data. The controller 18 then determines an input fluid volume for the first time period by summing the respective input fluid volume data from the plurality of input fluid flow sensors 2a-c. The controller 18 also determines an output fluid volume for the second time period by summing the respective output fluid volume data from the output fluid flow sensors 14a, 14b. Determining the input fluid volume and output fluid volume may also involve the controller 18 converting measurements of volumetric fluid flow rate into volume data, or into any other kind of data that is required to determine the values of input fluid volume and output fluid volume.

[0151] In some embodiments, some or all of the input fluid flow sensors 2a-c and / or some or all of the output fluid flow sensors 14a, 14b may determine the input / output fluid volume for each respective sensor. The determination may be shared, i.e. communicated, between the flow sensors and the controller 18.

[0152] Once the input fluid volume and the output fluid volume has been determined, the controller 18 performs one or more operations to determine the difference between the input fluid volume and the output fluid volume. For example, the controller 18 may subtract the output fluid volume from the input fluid volume. The difference may be a single scalar value of volume difference. A positive difference may indicate that more fluid is entering the patient 6 than exiting. A negative difference may indicate that more fluid is exiting the patient 6 than entering. A difference of zero indicates that the fluid volume flowing into the patient 6 is balanced with the fluid volume exiting the patient 6.

[0153] Once the difference has been determined, the controller 18 may output the difference via the output means 8. In the embodiment shown in Fig. 3, the output means 8 comprises a display 10, and the output from the output means 8 may involve the difference being displayed on the display 10. This allows for healthcare professionals to see at a glance the balance of total fluid flow being provided to the patient 6. The display 10 may also be configured to display the individual values for the input fluid volume data and output fluid volume data. This allows for a healthcare professional to see the volume of fluid provided to the patient 6, and the volume of fluid output from the patient 6. The controller 18 in Fig. 3 is connected to the output means 8 via a wired connection. However, it will be appreciated that the controller 18 may be connected to the output means 8 using a wireless connection. The controller 18 and display 10 may be part of a single device. In some embodiments, the controller 18 is integrated into the output means 8, such that the controller 18 and the output means 8 are part of the same unit of the monitoring system 5. As will be appreciated, the system 5 shown in Fig. 3 may provide a net fluid flow through the patient 6 which can be quickly and easily seen by the healthcare professional. This is contrasted to prior art techniques whereby a healthcare professional would have to individually sum up the fluid flow through each input and output manually.

[0154] The controller 18 may also compare the difference with a threshold volume difference value. The threshold value may represent a value of fluid flow through the patient which is considered unsafe. For example, if the controller 18 has determined that 2000 millilitres of fluid is input to the patient 6 over an interval of one hour (which may comprise the first and / or second time periods), and only 20 millilitres of fluid is output from the patient 6 over an interval of one hour, then this may indicate that the patient 6 is accumulating fluid somewhere in the body. In the example of Fig. 3, the difference exceeds the safety threshold. The controller 18 may also compare the input volume (i.e. the sum of the individual volume through each input fluid line 4a, 4b, 4c) and / or the output fluid volume (i.e. the sum of the individual volume through each fluid output line 16a, 16b) to one or more pre-determined thresholds. An alert may be generated based on whether such thresholds are exceeded.

[0155] Based on the controller 18 determining that the difference exceeds the threshold value, the controller 18 sends a signal to the output means 8 to trigger an alarm to alert nearby healthcare professionals. In Fig. 3, the alarm is an audible alarm, announced using the speaker 12, however the alert may also be an electronic signal sent to one or more external devices (e.g. pagers) of healthcare professionals (discussed in more detail with reference to Fig. 4 below). The alert may comprise both an audible and visual component, such as an audible sound and an indicator light. The indicator light may flash.

[0156] The monitoring systems 3, 5 are able to determine the difference between the volume of fluid input to the patient 6 via input fluid line(s) and the volume of fluid output from the patient 6 via output fluid line(s). By determining this difference, the monitoring system 3, 5 can provide an output based on the difference, which may include displaying said difference for visual inspection by healthcare professionals. The monitoring system 3, 5 can also determine whether to use an alarm to send an alert when the determined difference is outside a safe threshold.

[0157] The monitoring systems 3, 5 are able to calculate the threshold volume difference value (i.e. net fluid flow over time). The calculation may be based upon one or more patient parameters. In one example, the patient parameters comprise a patient weight and a patient height. The patient parameters can be provided to the system 3, 5 (e.g. to the controller 18) via a user interface (not depicted). As will be appreciated, patients with different physical size (i.e. different heights and / or weights) may have a different value of the threshold volume difference that is appropriate. For example, the threshold volume difference may be calculated to be higher when a higher value for patient height and / or weight is input, as the patient may be expected to require more volume of fluid to be input and therefore expel a larger volume of fluid. Conversely, a patient with a lower height and / or weight will result in a lower calculated value for the threshold volume difference. The monitoring system can therefore customise the threshold volume difference value based on relevant patient parameters.

[0158] In some embodiments, the monitoring apparatus 1 and monitoring systems 3, 5 are configured to be provided with fluid designations for one or more specific fluid flow sensor(s). The apparatus 1 or systems 3, 5 may therefore be able to provide further information in the output that is specific to the kinds of fluid that is entering / exiting the patient 6. The fluid designations may be provided by a user. In these embodiments, the fluid flow sensor(s) of the monitoring apparatus 1, and monitoring systems 3, 5 may be configured to monitor the viscosity of the fluid that flows therethrough.

[0159] Fig. 4 is a schematic diagram of the output means 8 of any of Figs. 1-3, with the following differences. The output means 8 further comprises a wireless transceiver 22. The output means 8 may wirelessly send a signal to an external device 24 using the transceiver 22. The external device 24 comprises a transceiver 26 which can receive signals from the transceiver 22 of the output means 8. The transceiver 22 of the output means 8 and the transceiver 26 of the external device 24 may wirelessly communicate according to a standard wireless communication protocol such as Wi-Fi or Bluetooth or RF control as will be understood by those skilled in the art. The external device 24 may be a laptop, a mobile phone, a pager, or any similar device which can be used by a healthcare professional. Thus, when the external device 24 receives a signal from the output means 8 via the transceiver 22, the external device 24 can provide an immediate alert to a healthcare professional even when the healthcare professional is not nearby to the patient 6. In some embodiments, the display 10 and / or the speaker 12 may be included in addition to the transceiver 22. However, in other embodiments one or both of the display 10 and speaker 12 may be omitted. In some embodiments, the monitoring apparatus 1 or the monitoring systems 3, 5 are configured to store historic data - i.e. data generated by the apparatus or systems over time. Fig. 5 shows a schematic diagram of a monitoring system 7, but it will be appreciated that the following discussion also applies to embodiments of the monitoring apparatus 1 or the monitoring systems 3, 5. The monitoring system 7 has the same features as the monitoring system 3 described with reference to Fig. 2, but with the following differences. The output means 8 has been simplified in this Figure to only show a memory 20 (sometimes referred to as a storage means herein) and a user interface 21. In addition, or alternatively to the storage means 20, a remote storage means 20A may be provided. The storage means 20A may be utilised in a similar manner to the storage means 20 as is discussed below. The only difference may be that the apparatus / system may communicate with the remote storage means 20A via a suitable interface, and the remote storage means 20A may facilitate the retrieval of historic data separately to the apparatus / system.

[0160] The monitoring system 7, as with the other monitoring systems described herein, is able to determine the difference between the volume of fluid input to the patient 6 via the input fluid line 4 and the volume of fluid output from the patient 6 via output fluid line 16. The monitoring system 7 then provides an output via the output means 8 based on the difference.

[0161] The output means 8 described with reference to Fig. 5 comprises a storage means 20, and a user interface 21. The storage means 20 in this example is a non-volatile memory (e.g. a flash memory), though any other suitable kind of storage means may be used as appropriate. The storage means 20 stores historic data, which comprises at least one of the input fluid volume data, the output fluid volume data, the difference, and the output. When applied to the monitoring apparatus 1 , the historic data comprises at least one of the fluid volume data and the output. The historic data is stored together with an associated time. Accordingly, the system 7 stores timestamped historic data in the storage means 20.

[0162] A user (e.g. a healthcare professional) may input a request for historic data for a particular time or time period. This may be done via the user interface 21, or any other suitable means of the system 7. In response, the system 7 provides (e.g. via the user interface of the output means 8) the historic data that corresponds to the requested time / time period. The user can therefore ask to see the historic data with an associated time of, for example, 8pm, and then system 7 provides the historic data associated with that time.

[0163] The user can therefore provide a requested time period (e.g. 2pm to 3pm). As before, the system 7 is able to provide via the output means 8 the historic data that corresponds to the requested time period. The user may therefore be able to see how the output has changed over time, particularly with reference to a time period in the past.

[0164] When the historic data comprises more than one of the examples given above, each kind of data may be considered as an element of the historic data, and the user can therefore request a particular element of the historic data for the time / time period.

[0165] The requested time period may can be continuous in time or discontinuous in time. For example, a continuous time period requests historic data over a single time period (10am to 11am), whereas a discontinuous time period requests historic data over more than one time period (e.g. 10am to 11am and 4pm to 5pm). The user is therefore able to see how the output changes over multiple time periods within the requested time period, e.g. at the beginning of the day and at the end.

[0166] The output means 8 can also provide the requested time / time period along with the historic data associated with the requested time / time period. The user may therefore be able to see (e.g. via the user interface 21), the requested historic data and the corresponding time / time period.

[0167] In embodiments of the monitoring apparatus or the monitoring apparatuses that comprise a controller (e.g. in the case of the monitoring system the systems 3, 5, 7), it may be possible to change which fluid flow sensors are being used. Accordingly, it may be advantageous to associate the fluid flow sensors with the controller to ensure proper functioning of the apparatus / system. Therefore, Fig. 6 is a schematic diagram showing an example input fluid flow sensor 2, an output fluid flow sensor 14, and a controller 18 as previously described, but with the following differences. The input fluid flow sensor 2 has a first identification means 28, and the output fluid flow sensor 14 has a second identification means 29. The controller 18 has a reader 18a. The following discussion applies equally to examples of the monitoring apparatus or the monitoring system described herein, where for example as embodiments of the monitoring apparatus only comprise a single fluid flow sensor, there is only one identification means.

[0168] The controller 18 is configured to obtain information from the identification means 28, 29 and then to associate the fluid flow sensors 2, 14 with the controller 18. In one example, the identification means 28, 29 are Near-field Communication (NFC) tags or sensors that operate according to an NFC communication protocol, and so the fluid flow sensors can be associated with the controller by using the NFC tags / sensors. In this example, associating one or more fluid flow sensors with the controller 18 involves establishing a communication interface between the fluid flow sensors and the controller to facilitate further communication between the sensor and the controller 18. The fluid flow sensors can therefore be “paired” with the controller, allowing the fluid sensors to communicate wirelessly with the controller 18. In this example where the identification means 28, 29 are NFC tags / sensors, the identification means can be brought into close proximity to, or direct contact with, the reader 18a to enable association with the controller 18. The fluid flow sensors 2, 14 can therefore be associated with the controller 18 by having the respective identification means 28, 29 scanned by the reader 18a when the identification means 28, 29 are in close proximity to the controller 18. In this example, the reader 18a is an NFC receiver sensor configured to detect the presence of nearby NFC tags / sensors. Accordingly, the fluid flow sensors 2, 14 can only establish communication with the controller 18 when they are within a range of less than 1 metre to the reader 18a.

[0169] In another example, the identification means 28, 29 include respective machine readable labels, such as a QR code or barcode, and the reader 18a is a camera configured to read the machine readable labels.

[0170] Once associated with the controller 18, the fluid flow sensors may be identified to the controller 18 as either an input sensor or an output sensor. The controller 18 can therefore interpret data wirelessly received by the input fluid flow sensor 2 as input fluid volume data, and interpret data wirelessly received by the output fluid flow sensor 14 as output fluid volume data. This identification may be performed automatically, or e.g. following user input, e.g. the input of whether a given sensor is an input or output fluid sensor.

[0171] Fig. 7 is a flowchart which describes a method performed by the monitoring system 3 in order to monitor the fluid flow through the patient 6. The following method will be described in relation to the monitoring system 3 of Fig. 2, but it will be understood that the method equally applies to the monitoring system 5 of Fig. 3.

[0172] At step 30, the input fluid flow sensor 2 measures input fluid volume data over a first time period. When there are multiple input fluid flow sensors (e.g. input fluid flow sensors 2a, 2b, 2c of Fig. 3), the input fluid volume data comprises the output from each input fluid flow sensor. The monitoring system 3 then uses the measured input fluid volume data and the first time period to determine an input fluid volume for the first time period.

[0173] At step 32, the output fluid flow sensor 16 measures output fluid volume data over a second time period. When there are multiple output fluid flow sensors (e.g. output fluid sensors 14a, 14b of Fig. 3), the output fluid volume data comprises the output from each output fluid flow sensor. The monitoring system 3 then uses the measured output fluid volume data and the second time period to determine an output fluid volume for the second time period.

[0174] At step 34, the monitoring system 3 determines a difference between the input fluid volume and the output fluid volume. The monitoring system 3 determines the difference by subtracting the output fluid volume from the input fluid volume. As mentioned above, the monitoring system 3 may be provided with fluid designation information from the input / output fluid flow sensor(s) that allows the monitoring system 3 to track what type of fluid is flowing through the input / output fluid sensor(s) . The monitoring system 3 may then need to implement a more complex method of determining the difference that may involve determining the difference for each type of fluid, depending on the configuration of the system 3. At step 36, the output means 8 provides an output based on the difference. That may involve the output means 8 outputting the difference to the display 10, and the display 10 subsequently displays the difference.

[0175] In some embodiments, as depicted, at step 38, the monitoring system 3 compares the difference to a threshold to establish if the difference exceeds a threshold. The same step may be performed for input fluid volume and / or output fluid volume and associated thresholds.

[0176] In some embodiments, as depicted, at step 40, if the monitoring system 3 has determined that the difference is outside of the threshold, then the monitoring system 3 may generate an alert. The alert may be an audible sound broadcast by the speaker 12 of the output means. Alternatively, or in addition, the alert may be an electronic signal which is sent to a nearby healthcare professional (e.g. to an external device 24 discussed above).

[0177] It will be appreciated by those skilled in the art that the invention has been illustrated by describing one or more specific embodiments thereof, but is not limited to these embodiments; many variations and modifications are possible, within the scope of the accompanying claims.

Claims

CLAIMS1. A monitoring apparatus, for monitoring fluid flow into or out of a patient, the monitoring apparatus comprising:a fluid flow sensor configured to:attach to a fluid line fluidly connected to the patient; and measure fluid volume data comprising data proportional to the volume of fluid which has passed through the fluid line over a time period; wherein the monitoring apparatus is configured to determine, using the fluid volume data, a volume of fluid which has passed through the fluid line over the time period, and wherein the monitoring apparatus further comprises:an output means configured to:provide an output based on the volume of fluid and the time period.

2. The monitoring apparatus of claim 1, wherein the output comprises the volume of fluid and the time period.

3. The monitoring apparatus of claim 1 or 2, wherein the output means comprises a display configured to display the output.

4. The monitoring apparatus of any preceding claim, wherein the output means comprises a speaker configured to provide an audible output based on the output.

5. The monitoring apparatus of any preceding claim, wherein the output means comprises a transmitter configured to communicate the output to an external device.

6. The monitoring apparatus of any preceding claim, wherein the time period is the time since attachment of the fluid flow sensor to the fluid line.

7. The monitoring apparatus of any of claims 1 to 5, further comprising a user interface, wherein the time period is set by a user using the user interface.

8. The monitoring apparatus of any preceding claim, further configured to determine if the volume of fluid exceeds a threshold for a pre-set time period, and wherein the output is further based on the threshold for the pre-set time period.

9. The monitoring apparatus of claim 8, wherein the output comprises an alert when the volume of fluid exceeds the threshold for the time period.

10. The monitoring apparatus of any preceding claim, wherein the fluid flow sensor is configured to connect to a port of the fluid line.

11. The monitoring apparatus of any of claims 1 to 9, wherein the fluid flow sensor is configured to attach to an outside of the fluid line.

12. The monitoring apparatus of any preceding claim, further comprising a plurality of fluid flow sensors, wherein each fluid for sensor is configured to:attach to a respective fluid line fluidly connected to the patient; and measure respective fluid volume data for the respective fluid line; wherein the monitoring apparatus is configured to determine, using fluid volume data from each of the fluid flow sensors, a total volume of fluid which has passed through all of the fluid lines over the time period.

13. The monitoring apparatus of any preceding claim, further comprising a controller which uses the fluid volume data to determine the volume of fluid which has passed through the fluid line over the time period.

14. The monitoring apparatus of any preceding claim, wherein the fluid flow sensor and output means are provided as a single integrated device.

15. The monitoring apparatus of any preceding claim, further comprising a storage means or is configured to communicate data with a remote storage means, and wherein the monitoring apparatus is further configured to:store data comprising at least one of the fluid volume data and the output, together with an associated time, in the storage means or remote storage means thereby forming historic data;receive a request for historic data for a time and / or a time period; and in response, provide, via the output means, the historic data that corresponds to the requested time and / or time period.

16. The monitoring apparatus of any preceding claim, further comprising a controller, and wherein the fluid flow sensor comprises an identification means, and the controller is configured to obtain information from the identification means and associate the fluid flow sensor with the controller.

17. A system for monitoring fluid flow through a patient, the system comprising: an input fluid flow sensor configured to:attach to an input fluid line fluidly connected to the patient; and measure input fluid volume data comprising data proportional to the volume of fluid which has passed through the input fluid line over a first time period;an output fluid flow sensor configured to:attach to an output fluid line fluidly connected to the patient; and measure output fluid volume data comprising data proportional to the volume of fluid which has passed through the output fluid line over a second time period; andan output means;wherein the system is configured to determine: i) an input fluid volume based on the input fluid volume data measured over the first time period; ii) an output fluid volume based on the output fluid volume data measured over the second time period; and iii) a difference between the input fluid volume and the output fluid volume; and wherein the system is further configured to:provide an output via the output means based on the difference.

18. The system of claim 17, wherein the difference is the input fluid volume minus the output fluid volume.

19. The system of claim 17 or 18, wherein the output comprises the difference.

20. The system of any of claims 17 to 19, wherein the output comprises the input fluid volume and / or the output fluid volume.

21. The system of any of claims 17 to 20, wherein the system further comprises a storage means or is configured to communicate data with a remote storage means, and the system is further configured to:store data comprising at least one of: the input fluid volume data, the output fluid volume data, the difference and the output, together with an associated time, in the storage means or remote storage means thereby forming historic data;receive a request for historic data for a time and / or time period; andin response, provide, via the output means, the historic data that corresponds to the requested time and / or time period.

22. The system of any of claims 17 to 21 , wherein the system further comprises a controller, and the input fluid flow sensor and / or the output fluid flow sensor comprises an identification means, and the controller is configured to obtain information from the identification means and associate the input fluid flow sensor and / or out fluid flow sensor with the controller.

23. The system of any of claims 17 to 22, wherein the output means comprises a display configured to display the output and / or a speaker which provides an audible output based on the output.

24. The system of any of claims 17 to 23, wherein the output means comprises a transmitter configured to communicate the output to an external device.

25. The system of any of claims 17 to 24, comprising a plurality of input fluid flow sensors, each being configured to:attach to a respective input fluid line fluidly connected to the patient; and measure respective input fluid volume data for a respective input fluid line; wherein the system is configured to determine, using the sum of the respective input fluid volume data over the first time period for each of the input fluid flow sensors, the input fluid volume that has passed through all of the input fluid lines over the first time period.

26. The system of any of claims 17 to 25, comprising a plurality of output fluid flow sensors, each being configured to:attach to a respective output fluid line fluidly connected to the patient; and measure respective output fluid volume data for a respective output fluid line; wherein the system is configured to determine, using the sum of the respective output fluid volume data over the second time period for each of the output fluid flowsensors, the output fluid volume that has passed through all of the output fluid lines over the second time period.

27. The system of any of claims 17 to 26, further configured to determine if the difference exceeds a threshold, and wherein the output is further based on the threshold.

28. The system of claim 27, wherein the output means comprises an alarm which is configured to provide an alert when the difference exceeds the threshold.

29. The system of claim 27 or 28, wherein the threshold is adjusted based on the number of input fluid flow sensors and the number of output fluid flow sensors.

30. The system of any of claims 27 to 29, further configured to receive one or more patient parameters, and calculate the threshold at least in dependence upon the one or more patient parameters.

31. The monitoring apparatus of any of claims 8 or 9, wherein the apparatus is further configured to receive one or more patient parameters, and calculate the threshold at least in dependence upon the one or more patient parameters.

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