Patent Description:
The fluid is typically based on saline. It need not contain a drug or other biologically active ingredient: it could be used purely to maintain fluid pressure or hydration in the patient. Alternatively, the fluid could be a bodily fluid such as blood or plasma that is first removed from the patient, treated and then recirculated back to the patient.

HIPEC is a procedure that is used following surgery to remove cancerous tumours from inside the abdominal (or peritoneal) cavity. In order to kill cancerous cells that might remain, a heated saline solution containing one or more chemotherapy drugs is pumped into the peritoneal cavity to bathe the abdominal organs for a period of time: normally at least <NUM> to <NUM> minutes. By heating the fluid above ambient temperature, e.g. to <NUM>, the efficacy of the chemotherapy drugs is increased. Dedicated apparatus is provided for, in a recirculation mode, pre-treating the fluid by using a pump to circulate the fluid through a heated reservoir until it reaches the required temperature; then, in a delivery mode, pumping the pre-treated fluid into the abdominal cavity of the patient.

There are two variants of the HIPEC procedure. In closed HIPEC, at the end of the surgery a delivery tube and a return tube are inserted into the abdominal cavity and the main incision is stitched to close the cavity and substantially seal around those tubes. The HIPEC apparatus then pumps fluid into the cavity through the delivery tube. When the cavity is full, continued pumping causes the excess fluid to return to the apparatus via the return tube, owing to the internal pressure in the cavity. In open HIPEC, at the end of the surgery a delivery tube and a return tube are inserted into the abdominal cavity, which is left open. The HIPEC apparatus then pumps fluid into the cavity through the delivery tube. The apparatus simultaneously pumps excess fluid out of the cavity to return to the apparatus via the return tube. One advantage of open HIPEC is that the surgeon continues to have access to the abdominal cavity during the HIPEC process and can manipulate the abdominal organs to ensure that the fluid reaches all parts of them. A disadvantage is that it requires a second pump to drain the fluid from the patient.

The known HIPEC apparatus requires manual input to switch the apparatus between the recirculation mode and the delivery mode by rotating a dial. It would be preferable for switching to be under automatic control. The apparatus should also be suitable for use in both open and closed HIPEC procedures.

Because the delivery and return tubes must be inserted into the abdominal cavity at the end of the surgical procedure, they need to be kept sterile both inside and outside, while the HIPEC apparatus generally needs to be kept sterile only on the internal surfaces that come into contact with the fluid. There is a need for a convenient and reliable method of connecting the sterile delivery and return tubes to the non-sterile HIPEC apparatus.

Published patent application <CIT> discloses a surgical fluid management system that is not intended for HIPEC but for distending a uterine cavity to allow cutting and extraction of abnormal uterine tissue. The system comprises a fluid source, fluid delivery lines, one or more pumps, and a filter for re-circulating the fluid between the source and the uterine cavity.

Published patent application <CIT> discloses an arrangement for preparing sterile fluid at a predetermined temperature and pressure for medical use: specifically for peritoneal dialysis. The fluid may be heated by passing it through a coil in a bath of heating fluid, while a pump recirculates the heating fluid in the bath to homogenize its temperature. Similarly, The fluid may be cooled by passing it through a coil in a bath of cooling fluid, while a pump recirculates the cooling fluid in the bath to homogenize its temperature.

The invention provides a medical apparatus for delivering fluid to a patient, as defined in claim <NUM>. The scope of the invention is defined by the appended set of claims.

Features of the invention that are preferred but not essential are defined in the dependent claims.

One advantage of the fluid delivery apparatus of the present invention is the ease with which it can be switched from the recirculation mode to the fluid delivery mode, simply by reversing the direction of the first pump. This means that the mode can be changed automatically or under electronic control, without the need to manually turn a valve, for example.

Preferably, when the pump reverses, the valve assembly will respond to the change in pressure at the second valve port by opening one and closing the other of the first and second valves to direct fluid flow in the appropriate manner. However, the invention in its broadest scope does not exclude other means of achieving the same result, such as operating the valves under automatic control or replacing the first and second valves with a single, three-way valve.

<FIG> shows medical apparatus <NUM> for delivering fluid to a patient during a HIPEC procedure, in accordance with the invention. The apparatus <NUM> comprises a wheeled trolley <NUM>, on which the apparatus can be moved around. A column <NUM> carries a handle <NUM> for steering the trolley <NUM>, and a screen <NUM>, which can display information to an operator and may also be an interactive touch screen through which the operator can input instructions to the apparatus. The centre of the trolley <NUM> contains a recess <NUM>, into which a removable body <NUM> of the apparatus can be lowered. The removable body <NUM> will be described in more detail below. It is intended to be removed and replaced after each use of the apparatus to deliver fluid to a patient during a surgical procedure, while the other parts of the apparatus <NUM> can be re-used in multiple procedures. The recess <NUM> contains electrical contacts <NUM> for providing power and control signals to the removable body <NUM>. Projecting from each side wall of the recess <NUM> is the rotor <NUM> of a peristaltic pump.

<FIG> is a perspective view of the removable body <NUM> of <FIG>. It principally comprises a reservoir <NUM>, which is formed by securing together a lower part <NUM> that can contain a fluid and an upper part <NUM> that acts as a cover. The upper part <NUM> includes a handle <NUM> to facilitate lifting the removable body <NUM> into and out of the recess <NUM> of the trolley <NUM>.

A first side wall of the reservoir <NUM> is moulded with an arcuate recess that forms a track <NUM> for a first peristaltic pump <NUM>. Near the ends of the arcuate recess, the first side wall is penetrated by first and second pump ports <NUM>,<NUM>. The opposite, second side wall of the reservoir <NUM> is similarly moulded with an arcuate recess that forms a track <NUM> for a second peristaltic pump <NUM>, and is penetrated by third and fourth pump ports <NUM>,<NUM>. The first and second pump ports <NUM>,<NUM> are connected to one another by a first compressible tube <NUM> that runs around the track <NUM> of the first peristaltic pump <NUM>. In a well known manner, the first peristaltic pump <NUM> comprises a hub that is mounted for rotation about a horizontal axis and supports a set of rollers about its circumference. The rollers in one sector of the circumference compress the tube against the track <NUM>, trapping portions of fluid in the uncompressed lengths of tube between them. By rotating the hub, the rollers are caused to move around the track and force the portions of fluid to move with them. The direction of the first pump <NUM> is reversible so that it can be operated to pump fluid from the first pump port <NUM> to the second pump port <NUM> or vice versa. The second peristaltic pump <NUM> is configured in an identical manner to pump fluid between the third and fourth pump ports <NUM>,<NUM> via a second compressible tube <NUM>, although for the purpose of the present invention it is not essential that the second pump <NUM> should be reversible.

A heating panel <NUM> is provided in the base of the reservoir <NUM>. A temperature probe <NUM> is provided within the reservoir <NUM> and adjacent to the second pump port <NUM> to measure the temperature of fluid as it emerges from the second pump port <NUM>.

A valve assembly <NUM> is supported by the cover <NUM> of the reservoir <NUM>. Details of the valve assembly <NUM> are shown in the cut-away view of <FIG>. The valve assembly <NUM> comprises first, second and third chambers <NUM>,<NUM>,<NUM> associated respectively with first, second and third valve ports <NUM>,<NUM>,<NUM>.

The first valve port <NUM> opens between the first valve chamber <NUM> and the interior of the reservoir <NUM>. It is coupled to the upper end of an intake tube <NUM>, the lower end of which opens into the reservoir <NUM> below the expected fluid level.

The second valve port <NUM> opens between the second valve chamber <NUM> and the interior of the reservoir <NUM>. It is coupled to the upper end of a first transfer tube <NUM>, the lower end of which is coupled to the first pump port <NUM>, whereby the first transfer tube <NUM> passes through the interior of the reservoir <NUM> but fluid contained within the first transfer tube <NUM> remains separate from the bulk fluid in the reservoir <NUM>.

The third valve port <NUM> opens between the third valve chamber <NUM> and the exterior of the reservoir <NUM>. During use of the apparatus it is coupled to the proximal end of a delivery tube <NUM> for delivery of fluid to a patient, as described below.

The first and second valve chambers <NUM>,<NUM> are connected via a first valve <NUM>, which permits fluid to flow from the first valve chamber <NUM> to the second valve chamber <NUM> but not in the opposite direction. The second and third valve chambers <NUM>,<NUM> are connected via a second valve <NUM>, which permits fluid to flow from the second valve chamber <NUM> to the third valve chamber <NUM> but not in the opposite direction. There is no direct connection between the first and third valve chambers <NUM>,<NUM>. In the preferred embodiment of the invention the valves <NUM>,<NUM> are umbrella valves but other types of one-way valve would be acceptable alternatives.

A filter assembly <NUM> is also supported by the cover <NUM> of the reservoir <NUM>. The filter assembly <NUM> comprises a tray that is divided into a suction chamber <NUM> and a filter chamber <NUM>. There is no direct communication between the suction chamber <NUM> and the filter chamber <NUM> so they could alternatively be formed as separate components.

The suction chamber <NUM> is airtight, except for a suction return port <NUM> and a suction outlet port <NUM>. The suction return port <NUM> opens to the exterior of the reservoir <NUM>. During certain uses of the apparatus it may be coupled to the proximal end of a suction return tube <NUM> for receiving fluid from a patient, as described below. The suction outlet port <NUM> opens to the interior of the reservoir <NUM>. It is coupled to the upper end of a second transfer tube <NUM>, the lower end of which is coupled to the third pump port <NUM>, whereby the second transfer tube <NUM> passes through the interior of the reservoir <NUM> but fluid contained within the second transfer tube <NUM> remains separate from the bulk fluid in the reservoir <NUM>.

The filter chamber <NUM> comprises a gravity return port <NUM>, a filter inlet port <NUM> (hidden from view in <FIG>) and a filter outlet port <NUM> (also hidden from view in <FIG>). The gravity return port <NUM> opens to the exterior of the reservoir <NUM>. During certain uses of the apparatus it may be coupled to the proximal end of a gravity return tube <NUM> (<FIG>) for receiving fluid from a patient, as described below. The filter inlet port <NUM> opens to the interior of the reservoir <NUM>. It is coupled to the upper end of a third transfer tube <NUM>, the lower end of which is coupled to the fourth pump port <NUM>, whereby the third transfer tube <NUM> passes through the interior of the reservoir <NUM> but fluid contained within the third transfer tube <NUM> remains separate from the bulk fluid in the reservoir <NUM>. The filter outlet port <NUM> also opens to the interior of the reservoir <NUM>, such that fluid may fall into the reservoir from the filter outlet port <NUM>. A tube (not shown) may be coupled to the filter outlet port <NUM> to guide the falling fluid and prevent splashing. The filter chamber <NUM> also contains a filter <NUM> (not shown in <FIG>), arranged such that fluid entering the chamber <NUM> via the gravity return port <NUM> or the filter inlet port <NUM> has to pass through the filter <NUM> before it can exit the chamber <NUM> via the filter outlet port <NUM>. The filter <NUM> may be formed of any suitable porous or open-mesh material, certified for medical use, which is capable of trapping and/or absorbing particulate matter or adsorbing chemical or biological constituents of the fluid returning from the abdominal cavity of a patient, which it is desired to prevent from being recirculated to the patient again.

<FIG> illustrates a connector <NUM> which is useful for coupling an external tube to an exterior port <NUM> of a medical apparatus for delivering fluid to a patient or receiving fluid from a patient. For example, in the illustrated fluid delivery apparatus, the connector <NUM> may be used to couple the delivery tube <NUM> to the third valve port <NUM>; the suction return tube <NUM> to the suction return port <NUM>; or the gravity return tube <NUM> to the gravity return port <NUM>. Each connector <NUM> may be identical so that it can engage with any port <NUM>. However, it is preferred that each connector <NUM> and its corresponding port <NUM> are provided with complementary features such as keyways (not shown) that prevent the wrong connector <NUM> being coupled to the wrong port <NUM>. The connectors <NUM> and ports <NUM> may be labelled, e.g. by colour coding, to make the correspondence apparent to users.

Ignoring the presence of any keyways, as just discussed, the port <NUM> consists of a simple, cylindrical collar <NUM> that extends through a wall <NUM> of the apparatus and is open at both ends. The connector <NUM> is essentially a smaller cylinder that fits snugly through the collar <NUM> of the port <NUM>. An O-ring <NUM> is seated in an outward-facing circumferential channel of the connector <NUM> to seal between the connector <NUM> and the port <NUM>. A flange <NUM> projects radially from the connector <NUM> so that when the connector <NUM> is inserted into the port <NUM>, the flange <NUM> butts against the outer end of the collar <NUM> and prevents the connector <NUM> being inserted further. The proximal end of the connector <NUM> is divided by slots into a number of longitudinal arms <NUM>. In the illustrated embodiment, the number of arms <NUM> is four. Each of the arms <NUM> ends in an outwardly-projecting tang <NUM>, which has a radius greater than the internal radius of the collar <NUM> such that, as the connector <NUM> is inserted into the port <NUM>, the tangs <NUM> force the arms to bend inwards to fit through the collar <NUM>. Preferably the outer surfaces of the tangs <NUM> are tapered to facilitate inserting them into the collar <NUM>. Just before the flange <NUM> comes into contact with the distal end of the collar <NUM>, the tangs pass the proximal end of the collar <NUM>, thereby allowing the resilient arms <NUM> to spring outwards and the tangs <NUM> to form a snap-fit engagement with the proximal end of the collar <NUM>, as seen in <FIG>. This prevents the connector <NUM> being withdrawn from the collar <NUM>. The distal end of the connector <NUM> comprises a circumferential barb <NUM> or a series of ridges (not shown) that permit the proximal end of a flexible tube (not shown) to be pushed onto the connector and retained by the barb <NUM> so that it cannot easily be removed.

Because the distal end of the flexible tube is generally implanted into the patient during surgery, the tube and its attached connector <NUM> need to be kept sterile, while the external surfaces of the fluid delivery apparatus are typically not sterile. For this reason, the connector <NUM> is first attached to the tube and remains with it during sterilization and surgery. When the fluid delivery apparatus is needed, it is brought into the non-sterile area of the operating theatre and the tube is then connected to it by inserting the connector <NUM> into the port <NUM> as just described. When doing that, the operator grips the outside of the tube in the region of the barb <NUM> and there is no need for them to touch the port <NUM> or any other part of the unsterilized apparatus. Until the connectors <NUM> are attached, the external ports of the apparatus are preferably closed by removable caps (not shown) to prevent contamination of the interior of the apparatus.

<FIG> and <FIG> illustrate the flow of fluids through the fluid delivery apparatus during an initial, recirculation mode of operation. <FIG> marks the flow path on a copy of <FIG> and the same features will not be described again here. <FIG> shows the flow path in schematic form (not to scale). Fluid conduits are shown as open lines, with V-shaped arrows to indicate the direction of flow. Parts of the apparatus that are active in this mode are shown in black lines, while those not involved in this mode are shown in grey.

The recirculation mode of operation is used to prepare the fluid for delivery to the patient, in particular by pre-heating it to the desired temperature for the HIPEC procedure. A suitable volume of saline fluid is first delivered from a supply <NUM> into the reservoir <NUM> and the heater <NUM> is switched on to warm the fluid at the base of reservoir. Although the heat will spread through the fluid by conduction and convection, it can be brought to a more uniform temperature by using the first pump <NUM> to recirculate the fluid. The pump <NUM> is operated in a first direction (shown as clockwise in <FIG>) that pumps fluid from the first pump port <NUM> to the second pump port <NUM>. This lowers the pressure at the second valve port <NUM> and draws fluid from the reservoir <NUM> via the valve assembly <NUM>. The path followed by the recirculating fluid is thus: from the reservoir <NUM> through intake tube <NUM> into the first valve port <NUM>; through the first valve <NUM> to exit the valve assembly <NUM> via the second valve port <NUM>; through the first transfer tube <NUM> to the first pump port <NUM> and around the first pump <NUM> to return to the reservoir <NUM> via the second pump port <NUM>. Because of the reduced pressure at the second valve port <NUM>, the second valve <NUM> remains closed.

The temperature probe <NUM> monitors the temperature of the fluid as it emerges from the second pump port <NUM> and sends measurements to a controller (not shown) that can display the information to a human operator and/or use the information for automatic control of the heater <NUM> and the first pump <NUM>. The controller may also be used for manual and/or automatic control of the second pump <NUM>, the supplies of saline <NUM> and chemotherapy drugs <NUM> and any other aspects of the apparatus. For this purpose it may receive signals from other sensors (not shown), e.g. to monitor the temperature of the fluid at different locations, or the condition of the fluid returning from a patient.

<FIG> and <FIG> are similar to <FIG> and <FIG>, respectively, but illustrate the flow of fluids through the fluid delivery apparatus during a delivery mode of operation in a closed HIPEC procedure. As previously explained, in closed HIPEC heated saline containing chemotherapy drugs is pumped into the body cavity <NUM> of the patient. The cavity <NUM> being closed, pressure in the cavity <NUM> causes fluid to be discharged via a return tube <NUM> and return - normally assisted by gravity - to the fluid delivery apparatus.

In this mode, the first pump <NUM> is operated in the direction (shown as anti-clockwise in <FIG>) opposite to that in the recirculation mode. This draws fluid from the reservoir <NUM> via the second pump port <NUM> and pumps it to the first pump port <NUM>, from where it travels along the first transfer tube <NUM> and increases the pressure at the second valve port <NUM>. This closes the first valve <NUM> and opens the second valve <NUM> to allow fluid to emerge from the valve assembly <NUM> via the third valve port <NUM>. From there, it passes along the delivery tube <NUM> to the body cavity <NUM> of the patient. Fluid discharged from the body cavity <NUM> flows along the gravity return tube <NUM> to enter the filter chamber <NUM> through the gravity return port <NUM>. The fluid must pass through the material of the filter <NUM>, which traps particles and optionally other contaminants, before the filtered fluid flows out of the filter outlet port <NUM> and falls back into the reservoir <NUM>.

At some stage, the supply <NUM> of chemotherapy drugs is turned on to add those drugs to the fluid in the reservoir, from where the saline fluid can carry them to the patient. The apparatus is capable of introducing the chemotherapy drugs after the circulation shown in <FIG> and <FIG> has already been established with pure saline or, according to medical need, the drug supply <NUM> may be opened earlier, e.g. during the recirculation mode of operation, to ensure good mixing of the drugs with the saline before delivery to the patient. Similarly, a fixed dose of the chemotherapy drugs may be delivered at the outset or the supply my be continuous or intermittent as the need arises.

The apparatus is further provided with a waste tank <NUM> coupled to the delivery tube <NUM> by a discharge tube <NUM>. A valve (not shown) may be operated by the controller to divert circulating fluid into the waste tank <NUM>, for example in the event that there is excess fluid in the system or the fluid needs to be refreshed with clean fluid from the supply <NUM>.

The heater <NUM> may continue to operate during the delivery mode of the apparatus, in order to replace heat lost by the fluid as it circulates via the patient. It may be operated at selective times or at a power level determined in response to signals from the temperature sensor <NUM>, which can monitor the temperature of the fluid entering the second pump port <NUM>, or signals from other temperature sensors (not shown), e.g. for monitoring the temperature of fluid as it passes through the body cavity of the patient or when it returns to the reservoir.

<FIG> and <FIG> are similar to <FIG> and <FIG>, respectively, but illustrate the flow of fluids through the fluid delivery apparatus during a delivery mode of operation in an open HIPEC procedure. As previously explained, in open HIPEC heated saline containing chemotherapy drugs is pumped into the body cavity <NUM> of the patient. The cavity <NUM> being open, it remains at ambient pressure so fluid to be discharged needs to be pumped away. For this purpose the second pump <NUM> is brought into operation.

The first pump <NUM> and the valve assembly <NUM> operate in just the same manner as with closed HIPEC, described above with reference to <FIG> and <FIG>. However, when set up for open HIPEC, the return tube is connected as a suction return tube <NUM> to the suction return port <NUM> instead of the gravity return port <NUM>. As previously described, this might require the use of a different connector <NUM> on the return tube <NUM> if the ports <NUM>,<NUM> and connectors <NUM> have complementary keyways to prevent them being wrongly paired up.

The second pump <NUM> is operated in a direction (shown as anti-clockwise in <FIG>) that pumps fluid from the third pump port <NUM> to the fourth pump port <NUM>. This creates low pressure in the suction chamber <NUM> and draws fluid from the patient, via the suction return tube <NUM>, into the suction chamber <NUM>. From there, the fluid is drawn out via the suction outlet port <NUM> and the second transfer tube <NUM> to pass through the second pump <NUM> along the second compressible tube <NUM>. The fluid is pumped out of the fourth pump port <NUM> and passes through the third transfer tube <NUM> to enter the filter chamber <NUM> through the filter inlet port <NUM>. It must pass through the material of the filter <NUM>, which traps particles and optionally other contaminants, before the filtered fluid flows out of the filter outlet port <NUM> and falls back into the reservoir <NUM>.

The reader will understand that it is not essential for the fluid paths to be exactly as described in relation to the illustrated embodiment of the invention. For example, the first, second and third transfer tubes pass through the interior of the reservoir <NUM> only because they need to connect respectively to the first, third and fourth pump ports <NUM>,<NUM>,<NUM>. Although this keeps the tubes neatly contained within the apparatus, a different physical arrangement could be without changing the essential features of the fluid circuit.

Claim 1:
Medical apparatus for delivering fluid to a patient, comprising:
a reservoir (<NUM>) for a fluid;
a first pump (<NUM>) comprising first and second pump ports (<NUM>,<NUM>); and
a valve assembly (<NUM>) comprising first, second and third valve ports (<NUM>,<NUM>,<NUM>); wherein:
the first valve port (<NUM>) is in fluid communication with the reservoir (<NUM>);
the second valve port (<NUM>) is in fluid communication with the first pump port (<NUM>);
the third valve port (<NUM>) is an outlet for delivering fluid to a patient;
the second pump port (<NUM>) is in fluid communication with the reservoir (<NUM>); and
characterized in that
the first pump (<NUM>) is reversible such that:
in a recirculation mode, the valve assembly (<NUM>) is configured to permit fluid flow from the first valve port (<NUM>) to the second valve port (<NUM>) but not to the third valve port (<NUM>), the pump (<NUM>) being operated in one direction to draw fluid from the reservoir (<NUM>) through the valve assembly (<NUM>) to the first pump port (<NUM>) and to recirculate the fluid from the second pump port (<NUM>) to the reservoir (<NUM>); and
in a fluid delivery mode, the valve assembly (<NUM>) is configured to permit fluid flow from the second valve port (<NUM>) to the third valve port (<NUM>) but not to the first valve port (<NUM>), the pump (<NUM>) being operated in an opposite direction to draw fluid from the reservoir (<NUM>) to the second pump port (<NUM>) and to deliver the fluid from the first pump port (<NUM>) through the valve assembly (<NUM>) to the third valve port (<NUM>).