TECH N ICAL FI E LD

The present invention relates to a drainage device for removing fluid from a body cavity of a patient, and more precisely to a drainage device with a drainage completion detector. The present invention also relates to a method of determining when drainage is completed.

BACKG ROU N D

In contemporary medical care, the removal of bodily fluid from a body cavity, such as the pleural cavity or the abdomen, is a routine need and can be performed in several ways. Excessive bodily fluids, such as blood, pleural fluids, abdominal fluids, or pus, can accumulate into a body cavity due to pathological processes or surgical trauma. The excessive bodily fluid may then be drained through a conduit such as a polyvinyl chloride (PVC) tube which is accessed to the patient by a catheter.

Many times, the bodily fluid is drained under the forces of gravity, and the flow rate is controlled by a roller clamp which can be adjusted to restrict the flow. Furthermore, it is becoming more and more common to use an electronically controlled drainage pump. Such pumps include, for example, peristaltic-type pumps and valvetype pumps which can drain fluid in a gentle, slow and/or steady manner.

Draining pumps known in the art need constant monitoring by medical staff to ensure that the draining process is performed in the correct way. If any issues are encountered, the medical staff will manually interrupt the draining process. Should medical staff, for some reason, not be available to monitor the entire draining process, complications may be encountered. There is accordingly a need for a drainage device that can at least partially be used without supervision from medical staff.

Current draining procedures are also typically performed in a hospital or the like. Since the condition of accumulating excessive fluid may last for a prolonged time period, and drainage of fluid has to be performed at regular intervals, this imposes a strain to both hospitals (e.g. available beds, available medical staff), and to the patients who regularly needs to go to the hospital. There is accordingly a need for a drainage device that may be used at home.

A typical draining pump will be set to run for a predetermined amount of time. The pump therefore continues to run at constant suction pressure until it is being shut down. However, towards the end of the draining process, a pump running at constant suction pressure until the predetermined time has lapsed may cause severe pain to the patient. There is accordingly a need to provide an alternative drainage cycle.

From the above, it is understood that there is room for improvements and the invention aims to solve or at least mitigate the above and other problems.

SU M MARY

The invention is defined by the appended independent claims. Additional features and advantages of the concepts disclosed herein are set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the described technologies.

In a first aspect, there is provided a drainage device for draining fluid from a body cavity of a patient, the drainage device comprising: a pump unit connectable to a drainage tube, wherein the pump unit is configured to apply a suction pressure, through the drainage tube, to the fluid in the body cavity; and a detector for detecting a completion of drainage, the detector comprising: a sensor configured to measure a property indicative of air in the drainage tube; and a processor configured to detect air in the drainage tube in dependence on a change in the measured indicative property, wherein the processor is further configured to determine a completion of drainage in dependence on the detection of air in the drainage tube.

The drainage device is advantageous in that it can automatically detect a completion of drainage. This ensures that the drainage process can be interrupted, or a user notified, when sufficient excessive bodily fluid has been removed from a body cavity of a patient.

Because the suction pressure is not maintained after all excessive fluid has been removed, the drainage process can be significantly less painful to the patient. As a result of this, the drainage process may be performed without the need for painkillers and/or anesthesia. There is also less risk to tissue and organ damage, and a significantly reduced risk of an entrapped lung.

Because the drainage device can detect when the drainage is completed, the drainage process can also be tailored to the individual patient in a way that has not previously been possible.

Because completion of drainage is automatically detected by the drainage device, the drainage process can also be performed without a healthcare professional monitoring at all times. The drainage device may for example be used at home. The drainage process may also be remotely monitored and/or controlled by, for example, a healthcare professional.

Preferably, the indicative property is a property of the drainage device or a property of the fluid drained from the body cavity. Such a property has been found advantageous to measure, and allows the detector to be incorporated in the drainage device without significantly increasing the complexity and manufacturing cost of the drainage device.

Preferably, the sensor is external to the drainage tube such that, in use, it is not in contact with the fluid. An advantage of using an external sensor is that it allows the detector to be used with replaceable drainage tubes and/or existing drainage tubes in a cost-efficient manner. An external sensor also avoids a potential degrading of performance due to contaminants in the bodily fluid that may attach to a sensor in contact with said fluid.

Preferably, the sensor is configured to measure a propagation of waves through the drained fluid in the drainage tube, wherein the sensor preferably comprises emitting means for emitting waves, and receiving means for receiving waves, wherein, in use, the receiving means are configured to receive waves emitted by the emitting means. This provides for a property that can easily be measured by an external sensor. The propagation of waves is also highly dependent on the medium through which the waves propagate and can thus give a reliable indication of whether air is present in the drainage tube or not.

Preferably, the sensor is an ultrasonic sensor, and wherein the waves are ultrasonic sound waves. The propagation of ultrasonic waves is different through air compared to liquid. The ultrasonic waves can thus be used to distinguish between liquid and air in the drainage tube. Ultrasonic waves can also easily pass through the drainage tube and are accordingly usable with an optically non-transparent tube.

Preferably, the sensor is an optical sensor, and wherein the waves are electromagnetic waves in an optical spectrum, and wherein the drainage device is expected to be used together with an optically transparent drainage tube. Optical waves advantageously have a short wavelength which allows even small air bubbles to be measured and detected.

Preferably, the sensor is configured to measure an energy consumption or exerted torque of the pump unit. An advantage of measuring energy consumption or torque is that the sensor can be integrated in the drainage device, and does not have to be mounted on or near the drainage tube. The size and weight of the drainage device can accordingly be reduced, which makes it more portable.

Preferably, in use, the sensor is located along the drainage tube in a portion of the drainage tube between the first end portion of the drainage tube and the pump unit, and wherein the sensor is configured to detect air in the corresponding portion of the drainage tube. The fluid in this portion is advantageously less perturbed by the operation of the pump unit. The detection of air in the drainage tube can accordingly be more accurate.

Preferably, the drainage device further comprises: notification means configured to notify a user that drainage is completed; and/or a controller for controlling the pump unit, wherein the controller is configured to halt the pump unit or initiate a run- down operation of the pump unit when completion of drainage is determined. This is advantageous because the drainage process can be interrupted, or a user be notified.

Preferably, the processor is further configured to calculate a drained volume of liquid. Knowing the drained volume of fluid for each drainage process gives a good indication of the success rate of the long-term drainage treatment.

Preferably, the pump unit comprises a rotatable peristaltic pump and the drained volume is estimated based on an angular rotation amount of the rotatable peristaltic pump from a start of drainage until the determined completion of drainage. The flow rate through a rotatable peristaltic pump is advantageously linearly dependent on the angular rotation amount of the rotatable peristaltic pump. The angular rotation amount of the rotatable peristaltic pump is also easy to measure. Thus, an accurate determination of the volume can be obtained from the start of drainage until the detected completion of drainage.

In a second aspect, there is provided a drainage system for draining fluid from a body cavity of a patient, the drainage system comprising: a drainage device according to any preceding claim; and a drainage tube connectable in a first end portion to the body cavity.

In a third aspect, there is provided a detector for detecting a completion of drainage of a drainage device, the detector comprising: a sensor configured to measure a property indicative of air in the drainage tube; and a processor configured to detect air in the drainage tube in dependence on a change in the measured indicative property, wherein the processor is further configured to determine a completion of drainage in dependence on the detection of air in the drainage tube.

In a fourth aspect, there is provided a method of detecting a completion of draining of a liquid from a body cavity, the method comprising: connecting a drainage tube to a body cavity; draining a liquid through a drainage tube by a pump unit connected to the drainage tube; detecting air in the drainage tube by a detector; and determining by the detector that draining is completed in dependence on the presence of air in the drainage tube.

In a fifth aspect, there is provided a method of determining a volume of drained liquid by a drainage device, the method comprising: detecting a completion of drainage by the method of the fourth aspect; measuring an angular rotation amount of a peristaltic pump of the pump unit from a start of drainage until the detected completion of drainage; and determining the volume of drained liquid based on the measured angular rotation amount. BRIEF DESCRIPTION OF TH E DRAWINGS

In order to best describe the manner in which the above-described embodiments are implemented, as well as define other advantages and features of the disclosure, a more particular description is provided below and is illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the invention and are not therefore to be considered to be limiting in scope, the examples will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

Fig. 1 is an illustration of a patient with pleural effusion;

Fig. 2 is a perspective view of a drainage device according to embodiments;

Fig. 3 is a schematic block diagram of a drainage device according to embodiments;

Fig. 4 is a top view of a drainage device according to embodiments;

Fig. 5 is schematic block diagram of a drainage device with a detector according to embodiments;

Fig. 6 is a schematic block diagram of a detector according to embodiments;

Fig. 7 is an illustration of a detector according to embodiments;

Fig. 8a is a top view of a drainage tube mounted optical sensor according to embodiments;

Fig. 8b is a front view of a drainage tube mounted optical sensor according to embodiments;

Fig. 8c is a top view of a drainage tube mounted ultrasonic sensor according to embodiments;

Fig. 8d is a front view of a drainage tube mounted ultrasonic sensor according to embodiments;

Fig. 9a is a top view of a drainage device comprising a detector according to embodiments;

Fig. 9b is a top view of a drainage device comprising a detector according to embodiments;

Fig. 10 is a schematic illustration of an energy consumption of a pump unit according to embodiments;

Fig. 11a is a schematic illustration of a peristaltic pump mechanism;

Fig. 11b is a detail view of a peristaltic pump mechanism;

Fig. 11c is a schematic illustration of a flow rate through a peristaltic pump mechanism;

Fig. 12 is a flowchart of a method for determining a completion of drainage according to embodiments;

Fig. 13 is a flowchart of a method for determining a drained volume according to embodiments. Further, in the figures like reference characters designate like or corresponding elements or parts throughout the several figures. The first digit in the reference character denotes the first figure in which the corresponding element or part appears.

DETAI LED DESCRI PTION

Various embodiments of the disclosed methods and arrangements are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components, configurations, and steps may be used without parting from the spirit and scope of the disclosure.

Hereinafter, certain embodiments will be described more fully with reference to the accompanying drawings. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the inventive concept. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice disclosed herein. It is to be understood that elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed or omitted, certain features may be utilized independently, and embodiments or features of embodiments may be combined, all as would be apparent to on skilled in the art.

The embodiments herein are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept. It should be understood that the description and the drawings are not intended to limit the invention to the particular form disclosed, but to the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. If nothing else is stated, different embodiments may be combined with each other.

Fig. 1 shows an illustration of an upper body of a patient 101. It is a common medical condition for excessive bodily fluid to accumulate in a body cavity 103, such as the pleural cavity or the abdomen. The bodily fluid may be blood, pleural fluids, abdominal fluid, pus, or similar fluids commonly found in the human body. The fluid may start to accumulate due to a pathological condition (e.g. cancer diseases) or a surgical trauma or the like. The condition of accumulating excessive fluid may last for a prolonged time period. The patient 101 in Fig. 1 has accumulated excessive fluid in a body cavity 103 between the lungs 102 and the lung lining, or pleura, surrounding the lungs 102. This condition is referred to as pleural effusion.

A typical procedure to mitigate the accumulation of excessive fluid in a body cavity 103 is to drain the excessive fluid.

Fig. 2 shows a drainage device 201 according to embodiments which may be used to drain excessive fluid from a body cavity 103. The drainage device 201 comprises a pump unit 202. In operation, the pump unit 202 creates a suction pressure which can be used to drain fluid from the body cavity 103. The pump unit 202 may comprise any suitable pump which can create a gentle, slow and/or steady suction pressure.

Preferably, the pump unit 202 comprises a peristaltic pump using a peristaltic pump mechanism. Alternative pump units 202 comprise valve-type pumps, and pumps employing a pumping motion created by a plurality of roller members which roll along a tube to impart motion to fluid in the tube.

In an embodiment, the pump unit 202 is contained in a housing 203 of the drainage device 201.

When the draining device is used, a drainage tube 204 is connected between the pump unit 202 and the body cavity 103. The drainage tube 204 is used to transport the fluid away from the body cavity 103. The removal of fluid from the body cavity 103 is thus achieved by the pump unit 202 creating a suction pressure to the body cavity 103 through the drainage tube 204, so that the fluid flows through the drainage tube 204 away from the body cavity 103.

The drainage tube 204 may be any suitable tube, conduit, pipe, or the like. Preferably the drainage tube 204 is flexible such that a suction pressure can be created through compression of the drainage tube 204, for example by a peristaltic pump mechanism. Preferably the drainage tube 204 is not permeable of fluid and/or air such that the drained fluid (and/or any air contained in said fluid) does not leak through the drainage tube 204. The drainage tube 204 may be made from any material suitable for medical use, and in particular may comprise polyvinyl chloride or any other thermoplastic material, an elastomer such as rubber, or any other material comprising polymers.

When the drainage device 201 is used to drain fluid from the body cavity 103, the drainage tube 204 is, in a first end portion 204a, connected to the body cavity 103. The drainage tube 204 is typically not inserted directly into the body cavity 103 since this would have medical and hygienic implications. Instead, an access port is usually provided to the body cavity 103 of the patient 101 that allows the drainage tube 204 to be connected thereto. The access port may be a catheter, a chest tube penetrating through the chest of the patient 101 into the body cavity 103, or the like, and are well known to a medical practitioner. The first end portion 204a of the drainage tube 204 is preferably provided with a patient side connecting means for connecting to the access port, which are well known in the medical field.

In use, a collection unit 205 may also be provided. The collection unit 205 is used to collect fluid drained from the body cavity 103. The collection unit 205 may, for example, be connected to a second end portion 204b of the drainage tube 204 so that the drained fluid flows through the drainage tube 204 and into the collection unit 205. In operation of the drainage device 201 , a suction pressure is created in the body cavity 103 by the pump unit 202, and bodily fluid is drained from the body cavity 103. The bodily fluid thus enters the first end portion 204a of the drainage tube 204 via the access port and patient side connector, passes the pump unit 202, and enters into a second end portion 204b of the drainage tube 204, after which it enters the collection unit 205 (if such is provided) or in another way is disposed of.

In an embodiment, the drainage tube 204 and/or the collection unit 205 is comprised by the drainage device 201. Alternatively, the drainage tube 204 and/or the collection unit 205 may be provided separately from the draining device, for example, to allow them to be replaced after use.

Fig. 3 shows a block diagram of the drainage device 201. The drainage device 201 comprises, in addition to the features mentioned above, also a controller 301. The controller 301 is used to control the pump unit 202. The controller 301 may be connected to the pump unit 202 through one or more electrical connector means, including but not limited to electrical wires and cables.

It is appreciated that the controller 301 may be integrated as part of a control system, where said control system may, for example, also comprise one or more power sources (e.g. batteries, connections to external DC voltage sources and/or AC voltage sources), one or more processing means and other features typically employed when controlling a pump unit 202, and these will be well known to a person skilled in the art.

The controller 301 may control the pump unit 202 in a pre-programmed manner to perform what is denoted a drainage cycle. The drainage cycle comprises an acceleration phase during which the pump unit 202 is controlled to accelerate from stationary to an operational rotational speed. The drainage cycle then comprises a steady operation phase during which the pump unit 202 is controlled to operate at the operational rotational speed. The drainage cycle also comprises a run-down period during which the pump unit 202 is controlled to decelerate from the operational rotational speed to stationary.

The acceleration phase allows a slow start of the drainage. This reduces the uncomforting feeling experienced by the patient as the drainage is initiated. It allows for the body of the patient to get accustomed to the suction pressure. The acceleration phase may preferably last for a time period in the interval of 20-40 seconds, and most preferably 30 seconds.

The steady operation phase is the time period where most of the bodily fluid is removed from the body cavity 103. The steady operation preferably lasts long enough for at least a substantial amount of the excessive fluid to be drained. The steady operation phase may preferably last for a time period in the interval of 150 to 250 seconds, and most preferably 200 seconds. The run-down phase is provided to reduce the uncomforting feeling experienced by the patient when the drainage process is suddenly stopped. It allows for the body of the patient to get accustomed to the pressure increase that occurs when the suction pressure is removed. The run-down period may preferably last for a time period in the interval of 20-40 seconds, and most preferably 30 seconds.

Fig. 4 shows a top portion of the drainage device 201 . The pump unit 202 in Fig. 4 is shown as a peristaltic pump. As can be seen, a central portion 204c of the drainage tube 204 is mounted around the peristaltic mechanism. As the peristaltic pump mechanism rotates around a central axis 403, rollers 402 of the peristaltic pump mechanism at least partially compress a portion of the drainage tube 204 so as to, during rotation, impart a linear wave motion in the fluid. A suction pressure is thus created in the drainage tube 204.

The drainage tube 204 may be fixed in an operating position by one or more fixation means 401 for attaching the drainage tube 204 to the housing 203. The fixation means 401 ensures that the drainage tube 204 does not move along with the rollers 402 of the peristaltic pump as the peristaltic pump rotates. The fixation means 401 are preferably provided with mechanical protrusions or indentations to enable the drainage tube 204 to be attached in a predetermined position. The fixation means 401 may alternatively be adhesive tape portions, cable connectors, or any other means capable of providing a secure but reversible fixation of the drainage tube 204 to the pump unit 202 and/or housing 203.

The controller 301 is shown in Fig. 4 as a dashed portion in the housing 203, but it is appreciated that the controller 301 may be located internally in the housing 203, or externally from the housing 203.

Fig. 5 shows a block diagram of a drainage device 201 according to an embodiment. In this embodiment, the drainage device 201 comprises a detector 501 for automatically detecting a completion of drainage. The detector 501 is arranged to detect when the drainage is completed. The detector 501 may thus be considered a detection completion detector. The detector 501 detects that drainage has been completed when at least a substantial quantity of the excessive fluid in the body cavity 103 has been removed.

The drainage process may, for example, be considered completed when half (i.e. 50 %) of the excessive fluid has been removed, preferably when more than half (i.e. 50 to 100 %) of the excessive fluid has been removed, more preferably when substantially all (e.g. 80 to 100 %) excessive fluid has been removed, or most preferably when all (i.e. 100%) of the excessive fluid has been removed.

Detecting a completion of drainage, in accordance with embodiments, allows the drainage process to be interrupted when the drainage is completed. A drainage device without a detector 501 typically run for a predetermined amount of time (e.g. about 4 minutes). During the latter part of this period, the excessive fluid may already be sufficiently removed. Thus, when the drainage process is allowed to continue, a vacuum may be built up in the body cavity 103: This can be very painful to the patient, especially if the suction pressure is maintained after the vacuum has been obtained in the body cavity 103. It is therefore common for patients who undergo a drainage process to take medicaments such as painkillers or anesthesia. Furthermore, sustained suction pressure after completion of drainage may cause damage to tissue and/or internal organs. In some cases, a continued suction pressure can also cause the lung to become entrapped, resulting in severe pain to the patient.

The inventor has thus realized that it would be advantageous to detect a completion of drainage, so as to allow an action to be taken when the drainage is completed. Detecting a completion of drainage allows, for example, the drainage process to be interrupted when it has been completed. This mitigates the above problems of a drainage process set to run for a predetermined amount of time. A drainage device according to embodiments that is capable of detecting a completion of drainage allows the drainage process to be tailored to the needs of the specific patient in question. As all patients are inherently different, they will also accumulate different volumes of fluid over time. Thus, a patient-specific drainage process improves the medical care that can be given to any patient.

For example, the drainage process can be stopped before the predetermined amount of time has lapsed. The controller 301 may thus be configured to stop the pump unit 202 when completion of drainage has been detected.

Upon detection of completion of drainage, a run-down procedure (as explained above) may also be initiated. The controller 301 may thus be configured to initiate a run-down procedure of the pump unit 202 when completion of drainage has been detected.

In another embodiment, the drainage device 201 can notify a user (e.g. the patient or a healthcare professional) that drainage is completed. The drainage device 201 may comprise notification means for notifying the user that drainage is completed. The notification means may be based on an audio, haptic, or a visual notification, or a combination of the above. An audio-based notification may be a sound signal. A haptic notification may be a vibration, such as a vibrating portion of the housing 203 or other part of the drainage device 201 which the user can feel through touch. A visual notification may be provided by one or more lights, such as light emitting diodes (e.g. changing color, blinking), or by a user display located on the drainage device 201 which can indicate that drainage is completed. The notification means may preferably notify the user that the drainage process is approaching completion of drainage. For example, the notification means may comprise light emitting diodes that change color as the drainage process approaches completion of drainage (e.g. a green light indicating the drainage process not being close to completion of drainage, amber light indicating that the drainage process is close to completion of drainage, and red light indicating a completion of drainage). In another example, a sound signal emitted by the notification means may increase in volume as the drainage process approaches completion of drainage.

The drainage device may further be provided with a user interface, preferably comprising one or more buttons. The user interface may allow the user to interrupt the drainage process when the user has been notified that drainage is completed.

The process of draining excessive fluid from a body cavity 103 has generally been performed in hospitals or the like, and in the presence of professional healthcare workers. This enables the healthcare workers to monitor the draining process and, if considered necessary, stop the drainage process.

However, a drainage device 201 may, for various reasons, not be monitored at all times by medical staff. It is therefore not certain that a healthcare professional notices when all, or most, excess fluid has been removed from the body cavity 103. Embodiments are, in addition to usage in a hospital or the like, also directed to use while the patient is at home. Thus, there may be no or limited monitoring by a healthcare professional. The inventor has realized that there is a need for a drainage device 201 that automatically detects a completion of drainage.

The drainage device 201 with a drainage completion detector 501 according to embodiments may therefore be used at home and/or under less supervision of medical staff.

The drainage device 201 may comprise wireless communication means for connecting the drainage device 201 to a user terminal. The user terminal may be a remote control, a laptop, a smart phone, a smart watch, a tablet, or other similar device capable of communicating with the drainage device 201.

The drainage device 201 may communicate with the user terminal via the Internet, a cloud network, a Wireless Fidelity (Wi-Fi) network, a Wireless Local Area Network (WLAN), a Local Area Network (LAN), a telephone line (POTS), and/or a Metropolitan Area Network (MAN), a Bluetooth network or other network capable of transferring information between the drainage device 201 and the user terminal. The communication between the drainage device 201 and the user terminal may be performed in accordance with various communication protocols, such as Transmission Control Protocol and Internet Protocol (TCP/IP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), ZigBee, EDGE, infrared (IR), IEEE 802.11 , 802.16, cellular communication protocols, and/or Bluetooth (BT) communication protocols. The wireless connection means of the drainage device 201 may be connected to the user terminal via one or more servers, clouds, or similar.

The user terminal may comprise a user interface that allows the user to remotely interact with the drainage device 201. The user interface may be in the form of hardware such as physical buttons, or in the form of software, for example via a smartphone app. The controller 301 may thus be configured to control the drainage device 201 in response to a signal from the user terminal. Furthermore, the user terminal may be configured to receive data transmitted from the wireless communication means of the drainage device 201 , for example data about the status of the drainage device 201. The user terminal may be configured indicate the transmitted data to a user of the user terminal. The drainage device 201 can thus send a signal to the user terminal when completion of drainage is detected, and in response to said signal, the user terminal may notify a user (e.g. a healthcare professional) that drainage is completed. The user may then interact with the user interface of the user terminal and instruct the drainage device to interrupt the drainage process. Thus, even if a drainage process is performed at home, the drainage process can be monitored and/or controlled by a remotely located healthcare professional.

Fig. 6 shows an embodiment of the detector 501. The detector 501 can detect a completion of drainage as described above. The inventor has found that a reliable indication of completion of drainage is the presence of air in the drainage tube 204 during the drainage process. If there is a large amount of excessive fluid in the body cavity 103, then the drainage tube 204 will be filled with said fluid. However, as the drainage proceeds, and less fluid is present in the body cavity 103, some air may flow with the bodily fluid into the drainage tube 204. When all of the excessive fluid has been drained from the body cavity 103, the drainage tube 204 will be filled mostly, or entirely, with air. Although there is no continuous supply of air in the body cavity 103 (i.e. if the suction pressure is maintained, eventually there will be a vacuum in the body cavity 103), it has been found that a sufficient amount of air is usually present to fill at least a portion of the drainage tube 204.

Thus, a presence of air in the drainage tube 204 is indicative of drainage being completed. Moreover, the amount of air in the drainage tube 204 may be indicative of how close the drainage process is to completion. For example, one air bubble being present in the drainage tube 204 may indicate that the drainage process is near to completion, but a not insignificant amount of excessive fluid still remains in the body cavity 103, while a drainage tube 204 filled with air may indicate that the drainage process is fully completed and that no excessive fluid remains in the body cavity 103.

The presence of air, and potentially also the amount of air, in the drainage tube 204 accordingly provides a reliable measure of the completion of drainage.

As shown in Fig. 6, the detector 501 comprises a sensor 601 and a processor 602.

The sensor 601 can measure a property indicative of air in the drainage tube 204 during a drainage process. The measured property may be an internal property of the drainage device 201 , such as a property of the pump unit 202. Alternatively, the measured property may be a property of the fluid in the drainage tube 204 during the drainage process.

Examples of internal properties of the drainage device 201 that may be measured by the sensor 601 include energy consumption of the pump unit 202, torque of the pump unit 202 (for a set flow rate and/or rotational speed), and/or the flexibility of the drainage tube 204 (which is different if filled with liquid compared to air).

Examples of properties of the fluid that may be measured by the sensor 601 include a composition of the fluid in the drainage tube 204, the oxygen level in the drainage tube 204, the density of the fluid in the drainage tube 204, a propagation and/or transmissivity of waves (e.g. electromagnetic waves and/or sound waves) through the fluid in the drainage tube 204.

In one embodiment the sensor 601 is internal to the drainage tube 204. The internal sensor 601 is thus a sensor 601 arranged on a lumen side of the drainage tube 204. The sensor 601 may, for example, be located inside the drainage tube 204, or partially inside the drainage tube 204, such that it is in contact with the fluid drained through the drainage tube 204. The internal sensor 601 may thus be considered a sensor 601 with fluid contact.

Alternatively, in a preferred embodiment, the sensor 601 is external to the drainage tube 204, that is, the sensor 601 is located externally to the drainage tube 204. The external sensor 601 is thus a sensor 601 arranged on a non-lumen side of the drainage tube 204. The sensor 601 is thus not in contact with the drained fluid during the draining process. The external sensor 601 may thus be considered a sensor 601 without fluid contact.

The sensor 601 may, for example, be located along an outside portion of the drainage tube 204, on or in the housing 203 of the drainage device 201 , or on or inside the pump unit 202.

A sensor 601 external to the drainage tube 204 is advantageous for a number of reasons. The external sensor 601 will not be in direct contact with the fluid drained from the body cavity 103. The drained fluid may contain contaminants (such as blood clots, fat tissue etc.) which can attach to an internal sensor 601 . The external sensor 601 therefore avoids a potential degrading of performance due to these contaminants after a number of uses and allows the external sensor 601 to be used multiple times. Furthermore, an external sensor 601 poses fewer limitations on the drainage tube 204 used. For example, an external sensor 601 can be used with replaceable drainage tubes 204, whereas an internal sensor 601 has to be provided in each replaceable drainage tube 204. The external sensor 601 therefore reduces the cost of the system and also allows for easy manufacturing of the system. An external sensor 601 is also compatible with already available drainage tubes 204, and there is no need to modify said drainage tubes 204 to accommodate the internal sensor 601. For example, there is no need to provide the drainage tube 204 with one or more openings for inserting and/or attaching the sensor 601 thereto. Thus, the manufacturing of the drainage tubes 204 is simpler, and a risk of leakage is also avoided (e.g. if the openings are not properly sealed).

In a preferred embodiment, the sensor 601 measures a propagation of waves through the fluid in the drainage tube 204. This measurement has been found to be a very good indication of the presence of air in the drainage tube 204 and can be measured by an external sensor 601.

In an alternative preferred embodiment, the sensor 601 measures an energy consumption of the pump unit 202. This measurement has been found to be a very good indication of the presence of air in the drainage tube 204 and can be measured by an external sensor 601.

The sensor 601 measures the relevant property and sends a signal representing the measured values to the processor 602. The processor 602 receives the signal from the sensor 601 and determines whether the measured signal is indicative of air in the drainage tube 204. For example, the processor 602 may identify a change in the measured signal which is indicative of air in the drainage tube 204. The change may be a deviation from a reference value where the reference value corresponds to the measured value when no air is present in the drainage tube 204.

The processor 602 may determine if the change in sensor signal is indicative of air in the drainage tube 204 based on a threshold amount of a change. For example, if the change or deviation is larger than the threshold amount, then the change can be considered indicative of air in the drainage tube 204.

The processor 602 may alternatively determine if the change in sensor signal is indicative of air in the drainage tube 204 based on the duration of the deviation from the reference value. For example, if the deviation lasts longer than a threshold amount of time, then the change can be considered indicative of air in the drainage tube 204.

The processor 602 may further be able to determine the amount of air in the drainage tube 204 based on the signal representing the measured values and/or a change in the signal representing the measured values. For example, a larger change in the signal may correspond to a larger amount of air in the drainage tube 204.

When air has been detected, the processor 602 determines whether the detection of air in the drainage tube 204 is consistent with drainage being completed.

The processor 602 may determine that drainage is completed if a detected amount of air is larger than a threshold amount. This criterion prevents drainage being considered completed due to e.g. a small air bubble being present before drainage is completed.

The processor 602 may determine that drainage is completed if the detected amount of air increases over time. This criterion prevents drainage being considered completed if an irregular presence of air is detected, for example, if an air pocket is present (with a steady stream of bodily fluid before and after) before drainage is completed.

The processor 602 may determine that drainage is completed based on the number or rate of air bubbles present, and/or on the size of air bubbles being present.

In an embodiment, the processor 602 determines that drainage is completed when the drainage tube 204 is filled with air.

In an embodiment, the processor 602 is configured to determine a temporal proximity of the drainage process to completion of drainage. The temporal proximity to completion of drainage may be determined based on an amount of air in the drainage tube 204 (where the amount of air is less than the amount of air at completion of drainage). For example, as the amount of air in the drainage tube 204 increases, the processor 602 may determine that the drainage process approaches completion of drainage, and preferably also the temporal proximity of the drainage process to completion of drainage, up until the time that the processor 602 determines that drainage is completed.

Once the processor 602 has determined that drainage is completed, the processor 602 can send a signal to the controller 301 indicating that drainage is completed. In response to the signal from the processor 602, the controller 301 may take one or more of the actions described previously, such as notifying a user, interrupting the drainage process, or initiating a run-down procedure.

The detector 501 may preferably comprise filtering means 603. The filtering means 603 can apply a signal processing filter, or any other signal processing operation, to the signal measured by the sensor 601. The filter may be applied to the measured signal itself, or to a measured change compared to a reference value (e.g. an initial value). The filtering can make it easier for the processor 602 to determine whether the measured change in sensor signal is indicative of air in the drainage tube 204. Signal processing filters are well known to a skilled person in the art and will therefore not be described herein in any more detail.

In various embodiments, the processor 602 and the controller 301 may be integrated in one control or processing unit. In various embodiments, at least a part of the processor 602 may be integrated in the sensor 601. In an embodiment, the whole detector 501 is contained in the sensor body 805.

Fig. 7 shows an illustration of a detector 501 according to embodiments. The sensor 601 in embodiments measures a propagation of waves 705 through the fluid in the drainage tube 204.

The sensor 601 in this embodiment comprises emitting means 701 and receiving means 702. The emitting means 701 and the receiving means 702 may be separated by the drainage tube 204 as shown in the Fig. 7. The emitting means 701 emits a packet of waves 705 through the drainage tube 204. The receiving means 702 receive the packet of waves 705 after it has passed through the drainage tube 204. The received packet of waves 705 by the receiving means 702, will be different if air (indicated by air bubbles 704) is present in the fluid 703 in the drainage tube 204, compared to when no air is present in the drainage tube 204. Thus, the signal measured by the receiving means 702 can indicate whether air is present in the drainage tube 204.

In alternative embodiments, the emitting means 701 and the receiving means 702 may be located on the same side of the drainage tube 204. A reflective surface may be provided on an opposite side of the drainage tube 204 so as to reflect the waves emitted by the emitting means 701 back to the receiving means 702. The waves received by the receiving means 702, will be different if air (indicated by air bubbles 704) is present in the fluid 703 in the drainage tube 204, compared to when no air is present in the drainage tube 204. Thus, the signal measured by the receiving means 702 can indicate whether air is present in the drainage tube 204.

Alternatively, instead of providing a reflective surface, the sensor can measure a portion of the emitted waves that has been reflected back by the fluid 703 in the drainage tube 204. A portion of the emitted waves may be reflected back due to a difference in refractive index between the fluid 703 and any air 704. The amount of the waves that are reflected back by the fluid in the drainage tube 204 is thus indicative of the presence and amount of air in the drainage tube 204.

The waves 705 used in Fig. 7 may be electromagnetic waves or sound waves. An embodiment with electromagnetic waves may use light, preferably in the optical spectrum. An embodiment with sound waves may use ultrasonic sound waves.

The emitting means 701 and the receiving means 702 are connected to the processor 602 and the measured signal is transmitted to the processor 602 by the sensor 601. The connection may be via wired connection means including an electrical conductor such as an electrical cable or wire, an optical fiber cable or any other suitable media for transferring a measured signal, or via wireless connection means such as the Internet, Bluetooth, Wi-Fi or other wireless network.

Fig. 8a and 8b shows an optical sensor 601. The emitting means 701 of the optical sensor 601 are configured to emit light waves in the optical spectrum. Any known optical sensor 601 may be used which is suitable for detecting air in a drainage tube 204. One example of such sensor 601 is sensor AD-101 Air Bubble Detector as manufactured by TE Connectivity.

The sensor 601 may comprise a sensor body 805. The sensor 601 may further comprise a first protrusion 802 and a second protrusion 803 extending the sensor body 805 so as to define a central tube cavity 804 where a portion of the drainage tube 204 may be inserted. The emitting means 701 and the receiving means 702 may be located in the first protrusion 802 and the second protrusion 803 respectively. The sensor 601 may further be provided with one or more holes 801 for fastening the sensor 601 by one or more screws, nails or the like to another object. Alternatively, the sensor 601 may be provided with an adhesive, tape or similar to fasten it to another object. The sensor 601 further comprises an electrical connection means 706 for transmitting a signal to the processor 602.

In an embodiment, the sensor body 805 comprises the processor 602. In such case, the electrical connection means 706 may instead be connected to the controller 301.

Fig. 8c and 8d show an ultrasonic sensor 601 . The emitting means 701 of the ultrasonic sensor 601 are configured to emit ultrasonic sound waves. Any known ultrasonic sensor 601 may be used which is suitable for detecting air in a drainage tube 204. One example of such sensor 601 is sensor SONOCHECK ABD07/xx-1 as manufactured by Sonotec.

The structural elements of the ultrasonic sensor 601 may be substantially similar to those of the optical sensor 601 and will therefore not be described here further.

Although no fastening holes are provided in the figures, it will be appreciated that such may nonetheless be provided.

Fig. 9a shows a drainage device 201 with a sensor 601 mounted on the housing

203 of the drainage device 201. The drainage device 201 is similar to the drainage device 201 of Fig. 4, and the features described in relation to Fig. 4 will not be described further here.

The sensor 601 is mounted to the housing 203 of the drainage device 201. The sensor 601 is located in a position where the drainage tube 204 is easily accessible. The sensor 601 may be mounted to the housing 203 through the fastening holes, or by other means such as an adhesive.

Although, the processor 602 is shown as being located in the housing 203 of drainage device 201 , it should be appreciated that the processor 602 may alternatively be located in the sensor body 805, or that the processor 602 may be integrated in a processing and control unit comprising both the processor 602 and the controller 301.

Although not shown in Fig. 9a, there may be provided further fixation means 401 for attaching the drainage tube 204 to the sensor 601.

Mounting of the sensor 601 on the housing 203 of the drainage device 201 ensures that no parts are loose and that it is easy to correctly insert the drainage tube

204 in the drainage device 201. Furthermore, the sensor 601 is fixed in place along the drainage tube 204 so that no (or limited) relative movement (e.g. sliding of the sensor 601 along the drainage tube 204) can occur.

Fig. 9b shows an alternative embodiment of the drainage device 201. The sensor 601 in Fig. 9b is flexibly mounted to the drainage tube 204. The sensor 601 is connected to the housing 203 of the drainage device 201 through electrical connector means 706. Apart from the mounting of the sensor 601 , all features are similar to those described in relation to Fig. 9a, and will accordingly not be described further here.

The flexibly mounted sensor 601 of Fig. 9b allows the sensor 601 to be moved along the drainage tube 204. This may be beneficial if, for example, a portion of the drainage tube 204 is smudged or dirty such that no proper measurement can be made by the sensor 601 in that portion. The flexibly mounted sensor 601 also allows for a size of the housing 203 of the drainage device 201 to be minimized. This is beneficial if the drainage device 201 is intended to be portable and/or used at home.

Although not shown in Fig. 9b, there may be provided a means for preventing sliding to ensure that the sensor 601 does not slide along the drainage tube 204. For example, a portion of the tube cavity 804 of the sensor 601 and/or the drainage tube 204 may be lined with a friction enhancing material.

The sensor 601 is preferably located between the pump unit 202 and the first end portion 204a of the drainage tube 204, i.e. at a portion of the drainage tube 204 between the pump unit 202 and the patient 101. The drained fluid in this portion of the drainage tube 204 is largely unperturbed by the pump unit 202. Thus, the accuracy of the sensor 601 can be improved. Furthermore, the sensor 601 is preferably mounted at or upstream of a first fixation means (the first fixation means being the fixation means 401 located closest upstream of the pump unit 202). Fig. 9a and Fig. 9b shows a sensor 601 located upstream of the first fixation means. This allows the first fixation means to be placed in close proximity to the pump unit 202, so as to allow for more reliable fixation of the drainage tube 204.

The sensor 601 may also be integrated in the first fixation means. For example, the first fixation means may comprise one or more openings through which the sensor can measure the property indicative of air. In another embodiment, the first fixation means are transparent so as to allow the waves emitted by the emitting means 701 of the sensor 601 to propagate therethrough.

The sensor 601 may alternatively be integrated in the drainage device 201. This may be particularly appropriate if the sensor 601 measures one or more internal properties of the drainage device 201 itself as described previously, such as an energy consumption of the pump unit 202 or torque of the pump unit 202.

Fig. 10 shows a signal from a sensor 601 which measures the energy consumption of the pump unit 202. It has been found that a change in the energy consumption is a reliable indication of air in the drainage tube 204.

A sensor 601 measuring energy consumption of the pump unit 202 may preferably be integrated in the drainage device 201. The sensor 601 may for example be part of a processing and control unit comprising the sensor 601 , the processor 602, and the controller 301 .

In embodiments, the controller 301 is configured to measure the rotational speed of the peristaltic pump, and, in response to the measured rotational speed, the controller 301 is configured to adjust the operation of the peristaltic pump so as to keep the rotational speed close to constant. In other words, the controller 301 is arranged to keep the rotational speed of the peristaltic pump constant by adjusting the power supply to the pump unit 202. The supplied power to the pump unit 202 may thus be used as a measure of the load on the pump unit 202.

The rotational speed of the peristaltic pump can thus be kept close to constant even if the load on the pump unit 202 varies. The presence of air in the drainage tube will reduce the load on the pump unit 202. Thus, when air is present in the drainage tube 204, and as the rotational speed of the peristaltic pump is kept constant by the controller 301 , the energy consumption (or torque) of the pump unit 202 will be reduced. A change in energy consumption (or torque) of the pump unit 202 is accordingly a good indicator of air in the drainage tube. The sensor 601 may thus be configured to measure the energy consumption (or the mechanical torque) of the pump unit 202.

Alternatively, the controller 301 may be configured to keep the energy consumption of the pump unit 202 constant. Thus, when air is present in the drainage tube 204, and the load on the pump unit 202 is reduced, the rotational speed of the peristaltic pump will increase. The sensor 601 may accordingly be configured to measure the rotational speed of the peristaltic pump.

As can be seen in Fig. 11 , and as explained previously, there may be an acceleration phase at the start of the draining process. The acceleration phase in Fig. 11 lasts until the indicated time 1001. After the acceleration phase, there is a steady state phase during which the pump unit 202 is operated at a steady operational rotational speed. The energy consumption during the steady state phase should accordingly be substantially constant until air enters the drainage tube 204. As air enters the drainage tube 204, the energy consumption of the pump unit 202 is likely to decrease. This is shown in Fig. 10 at time 1002 and time 1003, where the sensor 601 measures a change in energy consumption. At time 1002 a short temporary change in energy consumption is measured. Such a change may be indicative of an air bubble being present in the drainage tube 204. At time 1003 a larger and sustained change in energy consumption is measured. Such a change may be indicative of at least a portion of the drainage tube 204 being at least partially filled with air. It should be appreciated that the measured signal shown in Fig. 10 is merely illustrative, and that the changes in the measured signal shown may be overexaggerated or underexaggerated depending on the specific circumstances of the operating conditions and system used.

The processor 602 may determine that a change in energy consumption change is indicative of air being present in the drainage tube 204 based on a threshold amount of a change. For example, if the change in energy consumption is larger than the threshold amount, then the change is considered indicative of air in the drainage tube 204.

The detector 501 may additionally be able to determine that there is a blockage in the drainage tube 204, caused by, for example, blood clots, lumps of fat or other organic material commonly present in a human body. Such a blockage may at least partially restrict the flow of fluid through the drainage tube 204. A blockage would thus cause the energy consumption of the pump unit 202 to increase.

To determine that there is a blockage in the drainage tube 204, the detector 501 may be able to differentiate between a change in energy consumption indicative of air in the drainage tube 204 and a change in energy consumption change indicative of a blockage in the drainage tube 204. For example, the detector 501 may determine that a change is indicative of air in the drainage tube 204 if the change is positive, while the detector 501 may determine that a change is indicative of blockage if the change is negative, or vice versa.

Furthermore, the detector 501 may determine if the energy consumption change is indicative of a blockage in the drainage tube 204 based on a threshold amount of a change. For example, if an energy consumption change amount is larger than the threshold amount, then the change is considered indicative of a blockage in the drainage tube 204.

In many situations it is desirable to know the amount of fluid drained in a drainage process. The volume of drained fluid during a drainage process may, for example, be a good indicator for the long-term success rate of a draining treatment for a patient. Typically, for a patient suffering from accumulation of bodily fluid in a body cavity, there is a need for repeated or recurrent drainage of said fluid. For example, it may be necessary to drain the accumulated fluid on a daily basis, or on a weekly basis. However, after an amount of time, the amount of accumulated fluid in the body cavity will typically decrease, such that less and less fluid is accumulated per day.

Once the accumulation of fluid is sufficiently low, it may be appropriate to stop the draining treatment. For example, if the drained volume in consecutive drainage procedures (for example one drainage procedure every day) is below a threshold amount, it may be decided that the draining treatment has been successful and thus to stop the draining treatment. Accordingly, it is important to know the amount of fluid drained for every drainage procedure.

The drainage device 201 may be provided with a memory for storing the drained volume for one or more successive drainage processes during a drainage treatment. The processor 602 may thus be configured to compare the determined volume of a current drainage process with the determined volumes of previous drainage processes. The processor 602 may further be configured to decide that the drainage treatment is completed in dependence on the drained volumes in current and previous drainage processes. Known methods of estimating a drained volume of fluid is based on either (i) visual indication on a collection unit 205 or similar, or (ii) by merely estimating that the drained volume is equal to a reference flow rate through the pump unit 202 (at operational conditions) multiplied by the predetermined running time of the drainage process. The first method involves collection of fluid and relies on an ocular inspection by a user in order to estimate the drained volume. The second method merely provides a reference value of the drained volume in a scenario where excessive fluid is available in the body cavity throughout the predetermined time period. The drained volume will accordingly be significantly overestimated in a scenario where the excessive fluid is fully drained before the predetermined time period has lapsed. Accordingly, there is a need to provide a more accurate method of automatically determining a volume of drained fluid.

Disclosed is a method of calculating the drained volume of fluid using a drainage device 201 as previously described. In calculating the drained volume according to embodiments, the completion of drainage is detected by the drainage device 201 as described previously.

The drainage device 201 can calculate the drained volume by considering the flow rate of fluid passing through the pump unit 202 for the duration of time between start of drainage until the detected completion of drainage. An accurate estimate of the volume of drained fluid can thus be obtained no matter how long the drainage process lasts.

When the pump unit 202 comprises a peristaltic pump, the flow rate of fluid passing through the pump unit 202 can be accurately determined. Fig. 11 a illustrates how rotation of the peristaltic pump relates to the amount of fluid 703 passing through the pump unit 202.

In a first part of the rotation, a first roller 402a compresses a portion of the drainage tube 402 such that fluid 703 upstream of the first roller 402a cannot pass it the first roller 402a.

In a second part of the rotation, an amount of fluid 703 enters a portion of the drainage tube 204 upstream of the first roller 402a.

In a third part of the rotation, the peristaltic mechanism has rotated such that the amount of fluid 703 is enclosed between the first roller 402a and a second roller 402b compressing a portion of the drainage tube 204 upstream of the first roller 402a.

In a fourth part of the rotation, the compression caused by the first roller 402a has ceased and the amount of fluid 703 can pass through the drainage tube 204 downstream of the peristaltic pump.

Thus, as the peristaltic pump rotates a set amount, a set amount of fluid will pass through. For example, as the peristaltic pump with three rollers 402 illustrated in Fig. 11 a rotates 120 degrees, a volume of fluid equal to the reference amount of fluid will pass through the pump unit 202. The volume of fluid corresponding to the reference amount is dependent on the specific configuration of the peristaltic pump and drainage tube 204 used, and is related to, for example, the diameter of the drainage tube 204, the flexibility of the drainage tube 204, the diameter of the rollers 402, the diameter of the peristaltic pump, and the number of rollers 402.

The drainage device may typically be intended to operate with a designated type of drainage tube. Thus, the specific configurations of the peristaltic pump and the drainage tube 204 are typically known in advance, and the volume can therefore be accurately determined.

Alternatively, the user may, for example through a user interface of the drainage device 201 , specify the drainage tube characteristics for the specific drainage tube 204 that is used.

Fig. 11 b shows a detail view of a peristaltic pump. Two rollers 402 are shown, each compressing a portion of the drainage tube 204. The rotational speed is shown as n, and the flow rate through the pump unit 202 is denoted Q. Here, the rollers 402 do not entirely compress the drainage tube 204 such that the fluid is entirely enclosed between two rollers 402 but rather some leakage past a roller 402 may occur.

Fig. 11c shows the flowrate for such a system as a function of rotational speed. It has been shown experimentally that the flow rate Q is substantially linear to the rotational speed n, for relatively low rotational speeds (speeds below the line indicated as 1101). At high rotational speeds, non-linear effects may occur. However, peristaltic pumps used in the drainage device 201 according to embodiments operate at low rotational speeds and thus in the linear portion of the curve.

In other words, the flow rate through the pump unit 202 is proportional to the rotational speed of the peristaltic pump, and a known volume will pass through the pump unit 202 for every complete rotation of the peristaltic pump. The amount of fluid passing through the pump unit 202 can therefore accurately be determined based on the amount of rotation of the peristaltic pump.

Thus, for a specific system with known drainage tube 204 characteristics and peristaltic pump characteristics, the flowrate can accurately be determined based on the rotation of the peristaltic pump. Thus, by measuring the angular rotation amount (i.e. the accumulated angular rotation) of the peristaltic pump, from start of drainage until the detected completion of drainage, the drained volume can accurately be determined.

In an embodiment, the processor 602 is configured to calculate the drained volume according to the above-described method.

Before the start of a drainage process, the drainage tube 204 is likely to be (at least partially) filled with air. Thus, as the drainage device 201 is started, the detector 501 may detect a false completion of drainage due to an initial amount of air being present in the drainage tube 204. To mitigate this problem, the detector 501 may be inactivated until the initial amount of air in the drainage tube 204 has been replaced by bodily fluid. The detector 501 may, for example, be inactive for a predetermined amount of time at the start of the drainage process during which at least some of the initial amount of air is present. The predetermined amount of time may, for example, correspond to the time of the acceleration phase of the drainage cycle. Alternatively, the processor 602 may detect, based on a signal from the sensor 601 , when the initial amount of air in the drainage tube 204 has been replaced with bodily fluid.

Fig. 12 shows a method of detecting a completion of drainage for a drainage device 201.

In step 1201, a drainage tube 204 is connected to a pump unit.

In step 1203, fluid is drained through the drainage tube 204, using the pump unit 202.

In step 1205, air is detected in a portion of the drainage tube 204 using a detector 501.

In step 1207, drainage is determined to be completed in dependence on air being detected in the drainage tube 204.

Fig. 13 shows a method of determining a volume of drained fluid for a drainage device 201.

In step 1301, fluid is drained, and a completion of drainage is detected according to steps 1205 and 1207.

In step 1303, an angular rotation amount of a peristaltic pump of the pump unit 202 is measured from the start of a drainage process until the detected completion of drainage.

In step 1305, a drained volume of fluid is determined based on the measured angular rotation amount, by the above-described method.

Although specific reference has been made to the drainage of fluid from the pleural cavity, fluid may accumulate in other areas of the body, apart from the lungs, in connection with other medical conditions. For example, fluid may accumulate in the abdomen during a medical condition called ascites, or lymphatic fluid may accumulate just below the skin in the axillary and breast region after mastectomy after cancer surgery. The invention is thus not limited to drainage of the lung area.

Although specific reference has been made to the use of embodiments in the context of draining a bodily fluid from a body cavity, it is appreciated that where the context allows, embodiments are not limited to use in medical applications.

Throughout this specification, the word “may” is used in a permissive sense (i.e. meaning having the potential to), rather than in the mandatory sense (i.e. meaning must). Throughout this specification, the words “comprise”, “include”, and variations of the words, such as “comprising”, “comprises”, “including” and “includes”, do not exclude other elements or steps.

As used throughout this specification, the singular forms “a”, “an”, and “the”, include plural referents unless explicitly indicated otherwise. Thus, for example, reference to “an” element includes a combination of two or more elements, notwithstanding use of other terms and phrases for one or more elements, such as “one or more” or “at least one”.

The term “or” is, unless indicated otherwise, non-exclusive, i.e. encompassing both “and” and “or”. For example, the feature “A or B” includes feature “A”, feature “B” and feature “A and B”.

Unless otherwise indicated, statements that one value or action is “based on” and/or “in dependence on” another condition or value or action, encompass both instances in which the condition or value or action is the sole factor and instances where the condition or value or action is one factor among a plurality of factors.

Unless otherwise indicated, statements that “each” instance of some collection have some property should not be read to exclude cases where some otherwise identical or similar members of a larger collection do not have the property, i.e. each does not necessarily mean each and every.

Embodiments include the following clauses:

1. A drainage device for draining fluid from a body cavity of a patient, the drainage device comprising: a pump unit connectable to a drainage tube, wherein the pump unit is configured to apply a suction pressure, through the drainage tube, to the fluid in the body cavity; and a detector for detecting a completion of drainage, the detector comprising: a sensor configured to measure a property indicative of air in the drainage tube; and a processor configured to detect air in the drainage tube in dependence on a change in the measured indicative property, wherein the processor is further configured to determine a completion of drainage in dependence on the detection of air in the drainage tube.

2. The drainage device according to clause 1 , wherein the indicative property is a property of the drainage device or a property of the fluid drained from the body cavity.

3. The drainage device according to clause 1 or 2, wherein the sensor is external to the drainage tube such that, in use, it is not in contact with the fluid.

4. The drainage device according to any of clauses 1 to 3, wherein the sensor is configured to measure a propagation of waves through the drained fluid in the drainage tube.

5. The drainage device according to any of clauses 1 to 4, wherein the sensor comprises emitting means for emitting waves, and receiving means for receiving waves, wherein, in use, the receiving means are configured to receive the waves emitted by the emitting means.

6. The drainage device according to clause 4 or 5, wherein the sensor is an ultrasonic sensor, and wherein the waves are ultrasonic sound waves.

7. The drainage device according to clause 4 or 5, wherein the sensor is an optical sensor, and wherein the waves are electromagnetic waves in an optical spectrum, and wherein the drainage device is expected to be used together with an optically transparent drainage tube.

8. The drainage device according to any of clauses 1 to 3, wherein the sensor is configured to measure an energy consumption or exerted torque of the pump unit.

9. The drainage device according to any preceding clause, wherein, in use, the sensor is located along the drainage tube in a portion of the drainage tube between the first end portion of the drainage tube and the pump unit, and wherein the sensor is configured to detect air in the corresponding portion of the drainage tube.

10. The drainage device according to any preceding clause, wherein the sensor is an in-line sensor configured to be mounted on an outside portion of the drainage tube.

11. The drainage device according to any preceding clause, wherein the sensor is configured to transmit a signal relating to the measured indicative property to the processor, and wherein the processor is configured to detect air in the drainage tube in dependence on a change in the signal.

12. The drainage device according to clause 11 , wherein the detector further comprises filtering means configured to apply a filter to the measured signal.

13. The drainage device according to any preceding clause, wherein the drainage device further comprises notification means configured to notify a user that drainage is completed.

14. The drainage device according to any preceding clause, wherein the drainage device further comprises a controller for controlling the pump unit, wherein the controller is preferably configured to halt the pump unit or initiate a run-down operation of the pump unit when completion of drainage is determined.

15. The drainage device according to any preceding clause, wherein the processor is further configured to calculate a drained volume of liquid.

16. The drainage device according to clause 15, wherein the pump unit comprises a rotatable peristaltic pump and wherein the drained volume is estimated based on an angular rotation amount of the peristaltic pump from a start of drainage until the determined completion of drainage.

17. The drainage device according to any of clauses 1 to 14, wherein the pump unit comprises a rotatable peristaltic pump.

18. A drainage system for draining fluid from a body cavity of a patient, the drainage system comprising: a drainage device according to any preceding claim; and a drainage tube connectable in a first end portion to the body cavity.

19. The drainage system according to clause 18, wherein the first end portion of the drainage tube is connectable to the body cavity through an access port. 20. A detector for detecting a completion of drainage of a drainage device, the detector comprising: a sensor configured to measure a property indicative of air in the drainage tube; and a processor configured to detect air in the drainage tube in dependence on a change in the measured indicative property, wherein the processor is further configured to determine a completion of drainage in dependence on the detection of air in the drainage tube.

21. A method of detecting a completion of draining of a liquid from a body cavity, the method comprising: connecting a drainage tube to a body cavity; draining a liquid through a drainage tube by a pump unit connected to the drainage tube; detecting air in the drainage tube by a detector; and determining by the detector that draining is completed in dependence on the presence of air in the drainage tube.

22. A method of determining a volume of drained liquid by a drainage device, the method comprising: detecting a completion of drainage by the method of clause 21 ; measuring an angular rotation amount of a peristaltic pump of the pump unit from a start of drainage until the detected completion of drainage; and determining the volume of drained liquid based on the measured angular rotation amount.