Patent Description:
In contemporary medical care, the movement of fluid from a body cavity to another point for collection is a routine need and can be performed in several ways. When tubing or piping is used for carrying the fluid during the movement either gravity or a pump is utilized to create and/or sustain a suction pressure needed to move the fluid from one point to another.

At times the movement of fluid from the body must be performed in a gentle, slow and steady manner. Such gentle, slow and steady manner can be designated "peristalsis". Peristaltic pumping may be performed in a number of ways including, but not exclusively, by hand pump or with the use of a peristaltic pump.

Additional known methods for drainage procedures include plastic vacuum suction bottles and wall/portable suction. These methods typically produce a constant suction rather than a peristaltic suction. These methods also include plastic bottles that are pre-assembled with a vacuumed pre-set under pressure causing inadequate suction.

Since these pumps are not monitored at all times by medical staff, a problem may occur when the excess fluid has been removed from the patient. The pump continues to run until it is being shut down, and during this time the pumping causes severe pain to the patient.

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.

Prior art documents include <CIT> which discloses a chest drainage system which reduces or eliminates pooling of blood/liquid and/or clogging/clotting in the drainage tube and/or chest tube and provides objective and accurate measures of drained fluid volume and chest air leak. The chest drainage system continuously monitors chest tube and drainage tube status and clears pooled liquid in the drainage tube, and/or a clogged chest tube when necessary to restore negative pressure to the chest.

An object of the present invention is to provide a new type of drainage device which is improved over prior art, and which eliminates or at least mitigates the drawbacks discussed above. More specifically, an object of the invention is to provide a drainage device with a pressure relief valve that offers pain relief to patients in need of drainage. These objects are achieved by the technique set forth in the appended independent claims with preferred embodiments defined in the dependent claims related thereto.

According to embodiments of the invention, the above problems are solved by a pressure relief valve provided in the drainage device.

In a first aspect, a drainage device for removing fluid from a body cavity of a patient is provided. The device comprises a drainage tube, and a pressure sensing means. The drainage tube is connectable to a pump unit, which is configured to apply a suction pressure to the fluid in the body cavity, and the pressure sensing means is configured to detect when the applied suction pressure is at or above a predetermined threshold level. This is advantageous since the patient may experience the pain by a pressure exceeding the threshold level. By detecting the pressure, the pain can be relieved.

In one embodiment, the pressure sensing means is a pressure relief valve. The valve is configured to open when the pressure is at or above the predetermined threshold level. By opening the valve, the pain of the patient is relieved.

In another embodiment, the pressure relief valve, when open, is configured to allow air to flow through the drainage tube, thereby decreasing the suction pressure. A decreased suction pressure relieves the pain the patient experiences when the suction pressure becomes too high, i.e. exceeds a threshold level.

Preferably, the drainage device further comprises a non-return valve for preventing air from the pressure relief valve to enter the patient. It is advantageous from a patient security point of view not to let air travel in direction towards the patient. Complication of the patient may occur if air enters the patient.

The drainage device may further comprise a filter unit configured to remove pollutants from the air entering through the pressure relief valve. It is advantageous to remove possible pollutants from the air, which otherwise may accumulate inside the drainage device and cause a clog, a slower flow or reduced suction pressure.

The pressure sensing means comprises according to the invention a pressure sensor and a memory metal valve configured to control the suction pressure applied to the fluid in the body cavity. This is advantageous since a memory metal is a simple solution without need of additional sensors or electronics. Further, a memory metal provides a high level of recoverable plastic strain.

Preferably, the pressure sensor is configured to transmit an electric current to the valve, thus causing the valve to expand and form an opening configured to allow air to flow therethrough, thereby decreasing the suction pressure.

In one embodiment, the drainage device further comprises a pressure indicator configured to alert when the pressure is at or above the threshold level. This is helpful for the patient. If the patient feels that the suction pressure is beginning to be uncomfortably high, he/she can feel relieved by the indicator, which confirms that the pressure is actually on the high side, and that the pressure soon is going to be lowered. This can help the patient to endure any pain symptoms.

Preferably, the pressure indicator is one or more of a visual indicator, such as a lamp, a LED, a propeller means, a colour indication means or a visible air flow, or an audial indicator, such as a whistle means, or a bellow means. All forms of visual or audial indicators provide the patient with information regarding the suction pressure having reached a threshold level.

In one embodiment, a first end portion of the drainage tube is connectable to a patient side tube of a patient, and a second end portion of the drainage tube is connectable to a collection unit for collection of the removed fluid. It is advantageous to use a collection unit for gathering the removed fluid. A portable collection unit also means that the patient needs not be completely stationary when the drainage procedure is performed.

The pressure sensing means is preferably arranged between the patient side tube and the drainage tube. This is a favourable location since this is where the two tubes meet.

In one embodiment, the patient side tube is a chest tube. Fluid is often drained from the lung area of a patient, and in this case, the patient tube is a chest tube.

The predetermined suction pressure threshold level is preferably between <NUM>-<NUM> cmH<NUM>O. This is a suitable threshold level for most patients.

Embodiments of the invention will be described in the following; references being made to the appended diagrammatical drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

Hereinafter, certain embodiments will be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention, such as it is defined in the appended claims, to those skilled in the art. If nothing else is stated, different embodiments may be combined with each other.

<FIG> shows a patient <NUM> with lungs <NUM>. The lungs <NUM> are surrounded by lung lining, or pleura <NUM>. When the patient <NUM> suffers from e.g. different forms of cancer diseases, fluid may accumulate between the lung <NUM> and the lung lining <NUM>. This condition is referred to as pleural effusion <NUM>. This condition is treated by drainage by means of a drainage device <NUM> as will be described below. As such device <NUM> is not monitored at all times by medical staff, a problem may occur when the excess fluid has been removed from the patient <NUM>. The drainage device <NUM> continues to run until it is being shut down, and during this time the continued suction pressure causes the lung to become entrapped, resulting in severe pain to the patient <NUM>.

<FIG> show a front view of the drainage apparatus <NUM> and a perspective view of a part of the apparatus <NUM> respectively, according to one embodiment. The drainage apparatus is also referred to below as a drainage device, or a drainage system. The system/device <NUM> is disposable. That is, it is to be used once only, and thereafter be thrown away, such as to not spread infections between patients <NUM>.

As seen in <FIG>, the drainage apparatus <NUM> comprises a housing <NUM> for housing major components of the apparatus <NUM>, a, preferably flexible, drainage tube <NUM>, and a peristaltic mechanism <NUM>. The drainage tube <NUM> has a first end portion 7a, provided with a patient side connector <NUM> for connecting the device to an access port (not shown) of a patient <NUM>, and a second end portion 7b, provided with a device side connector <NUM>. A collection unit <NUM> is preferably provided, which is connectable to the device side connector <NUM> of the drainage tube <NUM>.

The drainage apparatus <NUM> may further comprises a pressure regulator <NUM>.

The depicted device further comprises at least one liquid property indicator <NUM>, a peristaltic movement indicator <NUM>, a peristaltic regulator <NUM>, a peristaltic regulator button 11a, a power button <NUM>, a battery power indicator <NUM>. Further, a sample port <NUM> is provided at a bottom end of the collection unit <NUM> to enable samples from the drained fluid to be extracted for further testing.

The drainage tube <NUM> is inserted through the peristaltic mechanism <NUM> and is fixed in its operating position by first fixation means <NUM> that fixes the operating position of said drainage tube <NUM> and provides optimal operating peristaltic conditions.

When the drainage tube <NUM> and the two connectors <NUM>, <NUM> are in position, the device may be activated by pushing the power button <NUM>. Thus, the device is ready for use.

To use the drainage apparatus, a patient's access port is connected to the patient side connector <NUM>.

Pressing the peristaltic regulator button <NUM> activates the drainage procedure and the peristaltic pumping is indicated by the peristaltic movement indicator <NUM>. As the bodily fluid is drained from the bodily cavity it enters the first portion 7a of the drainage tube <NUM> via the patient side connector <NUM>, passes the peristaltic mechanism <NUM> into the second end portion 7b of the drainage tube <NUM>, and then enters the collection unit <NUM> via the device side connector <NUM>.

The peristaltic regulator <NUM> controls a peristaltic motor in a preprogrammed manner to perform what may be denoted a "drainage cycle". To provide this preprogrammed manner of control the peristaltic regulator <NUM> is configured to include an acceleration phase during which the peristaltic motor is controlled to accelerate from an rpm of zero revolutions per minute up to a predetermined operational rpm during a first predetermined time period.

The peristaltic regulator <NUM> is further configured to subsequently regulate the motor to keep the predetermined operational rpm during a second predetermined time period.

The peristaltic regulator <NUM> is further configured to subsequently, during a third predetermined time period, decelerate the peristaltic motor from the operational rpm down to an rpm of zero revolutions per minute.

The first predetermined time period may preferably be chosen in the interval of <NUM>-<NUM> seconds, the second predetermined time period may preferably be chosen in the interval of <NUM> to <NUM> seconds, and the third predetermined time period may preferably be chosen in the interval of <NUM>-<NUM> seconds. Most preferably the predetermined time periods are chosen as around <NUM>, <NUM>, and <NUM> seconds respectively.

The peristaltic movement indicator <NUM> is configured to indicate to the user how much of the peristaltic movement capacity that has been utilized. The peristaltic mechanism is rotating and the regulator <NUM> controls the rotational speed. If the battery power supply reaches critical levels, the battery power indicator <NUM>, alerts the user to recharge the battery.

As liquid is transported through the second portion 7b of the drainage tube <NUM> and discharged through the device side connector <NUM> into the collection unit <NUM>, it will be in contact with the liquid property indicator <NUM>, and liquid properties such as pH and lactate are measured, as well as the totally accumulated volume.

The liquid property indicator(s) <NUM> is provided to determine properties of the drained liquid. Liquid properties are determined e.g. by means of chemical indicator(s) provided at the inside of the, preferably transparent, collection unit <NUM>.

The pH-value of the drained fluid could be measure for instance by means of a pH indicator in the form of a halo chromic chemical compound such that the acidity or basicity can be visually determined. Another option to determine the pH of the drained fluid is by means of electronic circuits configured to receive and process signals from pH sensors provided on an inner surface of the collection unit <NUM>, where the pH sensors are printed.

As described above, the liquid property indicator <NUM> may determine the presence of lactate, reflecting metabolic stress. This may be accomplished by means of a test strip that contains the immobilized substrate, L-lactate, and be visually determined by its colour intensity, or by means of electronic circuits arranged to receive and process signals from lactate sensors provided on an inner surface of the collection unit <NUM>, where the sensors are printed.

The body drainage system is preferably provided with a display unit (not shown), and the system is configured to display pH and/or lactate measurements on the display unit. The display unit may be arranged on, or as an integral part, of the drainage apparatus <NUM> or the housing <NUM>, or may alternatively be arranged at a stand or hanger (not shown) for the collection unit <NUM>.

<FIG> shows a loop of the drainage tube <NUM> and the first fixation means <NUM>. The tube <NUM> is firmly attached to the fixation means <NUM> which do not allow for any sliding between them. The first fixation means <NUM> is preferably provided with mechanical protrusions, indentations or other suitable means to enable the tube <NUM> forming the loop to be mounted in a certain position only.

The second fixation means <NUM>, shown in <FIG>, is preferably also provided with mechanical protrusions, indentations, or other suitable means, inverted in relation to those of the first fixation means <NUM>, in order to enable the first fixation means <NUM> and the loop to be mounted in a predetermined position only, and prevent mounting of the first fixation means <NUM> the wrong way in the second fixation means <NUM>. It is important for patient safety that the fixation means <NUM>, <NUM> are not mounted in the wrong way since this may cause fluid to be pumped into the patient <NUM> instead of out of the patient.

<FIG> shows the loop of the drainage tube <NUM> mounted around the peristaltic mechanism <NUM>. It can also be seen how the first fixation means <NUM> fits together with the second fixation means <NUM> to keep the drainage tube <NUM> in position for efficient pumping. In the body drainage apparatus <NUM>, the portion of the drainage tube <NUM> arranged around the peristaltic mechanism <NUM> has a length of tube corresponding to a length of arc of <NUM> to <NUM> degrees of a rotational revolution of the peristaltic mechanism <NUM>, such that the rollers of the peristaltic pump <NUM> compress this portion of the tube <NUM> during its course of action. The portion of the tube <NUM> preferably comprises a length of tube corresponding to a length of arc of <NUM> to <NUM> degrees of a rotational revolution of the peristaltic mechanism, or more preferred, <NUM> to <NUM> degrees, or most preferred <NUM> to <NUM> degrees.

<FIG> show the above described drainage apparatus <NUM> provided with a pressure relief valve arrangement <NUM>, and <FIG> show the valve arrangement <NUM>. The pressure relief valve <NUM> is configured to decrease the pressure applied by the drainage device <NUM> to a body cavity <NUM> of the patient <NUM>. Thereby the discomfort and pain experienced by the patient <NUM> is relieved.

The pressure relief valve arrangement <NUM>, which is best seen in <FIG> and <FIG>, comprises a pressure relief valve <NUM>, a filter unit <NUM>, a tap <NUM>, a first connector <NUM> and a second <NUM> connector. The valve unit <NUM> further comprises a casing <NUM> from which the connectors <NUM>, <NUM> protrude.

The filter unit <NUM> is arranged on a first surface 36a of the casing <NUM>. The filter <NUM> is permeable to air such that ambient air may enter the interior of the valve casing <NUM>, but impermeable to pollutions which are removed from the air entering the device <NUM>.

Inside the casing <NUM>, the valve <NUM> is provided with a valve membrane <NUM>. The membrane <NUM> is connected to an actuator <NUM>. The actuator is e.g. embodied as a spring, preferably as a coil spring. The interior of the casing <NUM> is further provided with a partitioning means <NUM>, which preferably is embodied as a plate. The plate <NUM> divides the interior of the casing <NUM> into a first portion <NUM> and a second portion <NUM>. The first portion <NUM> houses the valve membrane <NUM> and the spring <NUM>. The second portion <NUM> is a flow channel for the drainage fluid.

The partitioning plate <NUM> is provided with through openings <NUM>. The number of through openings <NUM> may vary between different embodiments and valve sizes. The in <FIG> shown number of seven openings <NUM> is to be seen as an example only. The entrance area 40a of the openings <NUM> is situated on the side of the partitioning means <NUM> facing the first portion <NUM> of the interior of the casing <NUM>. The exit area 40b of the openings <NUM> is situated on the side of the partitioning means <NUM> facing the second portion <NUM> of the interior of the casing <NUM>. The openings <NUM> are shaped as truncated cones. Thus, the entrance area 40a is larger compared to the exit area 40b. The openings <NUM> and their purpose will be further described below.

The pressure relief valve <NUM> is preferably a negative pressure relief valve. This means that the valve <NUM> opens when the pressure differential between the interior <NUM>, <NUM> and the exterior of the drainage device <NUM> becomes too large, i.e. exceeds a certain threshold level. The first connector <NUM> is preferably a barbed tube fitting, and it is adapted to be connected to the drainage tube <NUM>. The second connector <NUM> is adapted to be connected to a chest tube <NUM> of the patient <NUM>.

Fluid which is drained from the patient <NUM> passes through the chest tube <NUM>, entering the valve <NUM> via the second connector <NUM>, travels through the flow channel <NUM> in the direction of arrows F, and exits the valve <NUM> via the first connector <NUM>. This is shown in <FIG>.

When the suction pressure of the drainage device <NUM> applied to a body cavity <NUM> of a patient <NUM> is at or above the predetermined threshold level, the pressure relief valve <NUM> opens, which is shown in <FIG>. This is accomplished by the selection of the spring rate of the spring <NUM>. When the suction pressure exceeds the spring rate of the spring <NUM> it compresses. The compressed spring <NUM> brings the valve membrane <NUM> towards the plate <NUM>. Thus, a space is formed between the filter <NUM> and the membrane <NUM>, providing an air flow A into the first portion <NUM> of the interior of the casing <NUM>. The air flow A is led into the second portion <NUM> of the interior of the casing <NUM> by the openings <NUM>. The air flow A is thus directed into the fluid flow channel <NUM>, where it mixes with the fluid and continues into the drainage tube <NUM>, via the first connector <NUM>, thereby decreasing the suction pressure applied to the patient <NUM>. The truncated cone-shape of the openings <NUM> prevent capillary forces on the fluid and thus prevents fluid from entering the first portion <NUM>.

When/if the suction pressure normalizes, i.e. when the pressure drops to below the threshold pressure level the valve membrane <NUM> returns to its closed position. The air flow A is thus stopped.

The air A is forced in the direction of the collection unit <NUM> by the suction pressure exerted by the pump unit <NUM>. Thus, the air A is prevented from entering the patient <NUM>. For additional patient safety, the device <NUM> may be equipped with a non-return valve <NUM>, which is preferably an in-line non-return valve. The air A remains in the collection unit <NUM> once it has entered therein.

The tap <NUM> is preferably a three-way tap. The tap <NUM> is used to turn off the pressure regulation. Even though the default setting is to use the pressure regulation, in some embodiments, it may be desired not to use it. Then, the tap <NUM> becomes useful.

In one embodiment, filter unit <NUM> is a micro pore filter. The filter acts as a valve in itself since a flow-resistance needs to be overcome before air can enter through it. As long as the resistance in the tube <NUM> is smaller compared to the resistance through the filter <NUM>, no air will be let in. When the resistance through the tube <NUM> increases, air will begin to enter through the filter <NUM>, i.e. through the valve, and into the device <NUM>. Thus, the suction pressure acting on the patient <NUM> is decreased. In this embodiment, the actuator and the valve membrane are superfluous. However, the partitioning plate <NUM> is preferably provided such that the filter unit <NUM> is not in direct contact with the drained fluid. Thus, the filter <NUM> is arranged on a distance apart from the fluid, e.g. by means of the plate <NUM>. If the filter <NUM> contacts the fluid, the flow resistance through the filter may become too large for air to pass therethrough, which means that the filter cannot open.

The drainage device <NUM> comprises a pressure indicator <NUM> which indicates when the threshold pressure has been reached. This may be a signal to the user <NUM> that sufficient drainage has been achieved. The pressure indicator <NUM> is e.g. a visual pressure indicator, or it is an audial pressure indicator, which alerts the user by means of sound. The visual pressure indicator may be in the form of a LED or a lamp, or alternatively, or additionally the visual pressure indicator <NUM> comprises colour indication means. The colour pressure indicator <NUM> is configured to change its color when it comes into contact with air. Thus, when the pressure relief valve <NUM> is opened and air is let through, the colour pressure indicator <NUM> change colour and the user is alerted.

Another visual option for the pressure indicator <NUM> is a propeller means. The propeller means <NUM> is configured to rotate during depressurization, i.e. when the pressure relief valve <NUM> is open. When the pressure is normalized, the propeller means <NUM> stands still. Thus, it becomes apparent to the user <NUM> when the valve is open. If the propeller means is made to exert a noise when it is rotating a combination of visible and audial indication is obtained.

Yet another visual pressure indicator <NUM> is the air flowing through the drainage tube <NUM> when the pressure relief valve <NUM> is open.

The audial pressure indicator <NUM> may comprise bellow means. The bellow means <NUM> has an expanded mode and a collapsed mode. When the pressure is too low, the bellow means <NUM> collapses and emit a sound. When the pressure is re-normalized, the bellow means <NUM> returns to its expanded mode.

An alternative audial pressure indicator <NUM> is a whistle means. When air is entering through the whistle means <NUM>, i.e. when the pressure relief valve <NUM> is open, a sound is emitted. The whistle means may e.g. comprise a ball organ which produces a sound when air passes it.

In one embodiment, with reference to <FIG>, the valve arrangement <NUM> comprises a filter unit <NUM> and a valve membrane <NUM>. The pressure relief valve membrane <NUM> comprises a switch formed by a memory metal. The memory metal may also be referred to as one of SMA, smart metal, memory alloy, muscle wire, smart alloy. The valve membrane <NUM> of memory metal is arranged in operative connection with a pressure sensor <NUM>.

When the suction pressure registered by the pressure sensor <NUM> is below the threshold pressure level, the valve <NUM> is closed, as is shown in <FIG>. The fluid travels through pipe <NUM> in the direction of arrow F. No air is let through the valve <NUM>.

With reference to <FIG>, when the pressure detected by the pressure sensor <NUM> exceeds the predetermined threshold value, an electric current <NUM> flows from the pressure sensor <NUM> to the valve <NUM>. The current <NUM> heats the metal of the valve <NUM>, causing the memory metal to expand. Thus, an opening <NUM> in the valve <NUM> is opened. Thus, air A can flow through the filter unit <NUM>, through the opening <NUM> and into the fluid flow F, and thus relieving the suction pressure in the same way as described above in connection with <FIG>.

The connection between the valve arrangement <NUM> and the tube <NUM> is schematical only. Preferably, the connection comprises a connector valve of any suitable type. The valve arrangement <NUM> may be combined with features from the valve arrangement <NUM> as shown in <FIG> and described in connection with these figures.

In one embodiment, the drainage device <NUM> comprises a micro controller <NUM>, preferably arranged in the pump unit <NUM>. The suction pressure applied by the drainage device <NUM> is controllable by means of the micro controller <NUM>. The pressure regulation is conducted by means of for example an in-line pressure sensor <NUM> configured to communicate with the pump unit <NUM> via the micro controller <NUM>.

In one embodiment, the pressure relief valve is substituted by a pressure sensor <NUM>. When the pressure sensor <NUM> detects a pressure exceeding the predetermined threshold level, it transmits a signal to the pump unit <NUM>, thereby disconnecting the pump unit <NUM>. Alternatively, or additionally, the suction pressure applied by the pump unit <NUM> is regulated to a lower pressure.

A preferred pressure threshold level, at which the suction pressure is interrupted, is between <NUM>-<NUM> cmH<NUM>O. One possibility is to set the suction pressure threshold level to <NUM>-<NUM> cmH<NUM>O. This pressure level interval results in an efficient drainage. Another possibility is to use a lower threshold level. This is suitable for more sensitive patients <NUM>. A cancer patient may experience a lot of pain and it is preferred not to expose him/her to unnecessary pain. Thus, in this case, a preferred threshold level is <NUM>-<NUM> cmH<NUM>O. The predetermined threshold pressure could be pre-set, or it could be selectable from a variety of preset pressures, or it could be freely selectable, or it could be a combination of said options.

Claim 1:
Drainage device for removing fluid from a body cavity of a patient, the device (<NUM>) comprising a drainage tube (<NUM>), and a pressure sensing means (<NUM>; <NUM>), the drainage tube (<NUM>) being connectable to a pump unit (<NUM>), the pump unit (<NUM>) being configured to apply a suction pressure to the fluid in the body cavity (<NUM>), and the pressure sensing means (<NUM>; <NUM>) being configured to detect when the applied suction pressure is at or above a predetermined threshold level,
characterised in that the pressure sensing means comprises a pressure sensor (<NUM>) and a memory metal valve (<NUM>) configured to control the suction pressure applied to the fluid in the body cavity (<NUM>).