WO2016204612A1

WO2016204612A1 - Infusion pump unit

Info

Publication number: WO2016204612A1
Application number: PCT/NL2016/050427
Authority: WO
Inventors: Timotheus Joan Marie Lechner
Original assignee: Apad Octrooi B.V.
Priority date: 2015-06-17
Filing date: 2016-06-15
Publication date: 2016-12-22
Also published as: NL2014978B1

Abstract

The invention relates an infusion pump unit, comprising a pump device, a pressure sensor and a monitoring device. The infusion pump unit is configured to operate in a detection mode to locate an anatomical structure in the body of a patient, and in an infusion mode to infuse fluid into a patient. In the infusion mode, the monitoring device is configured to compare the sensor signal with a threshold pressure value, and to provide a warning signal when the sensor signal exceeds the threshold pressure value. In the detection mode, the monitoring device is configured to continuously provide on the basis of the sensor signal, a pressure level signal representative of a pressure level and/or pressure variation in the fluid.

Description

Infusion pump unit The present invention relates to an infusion pump unit. Infusion pump units are configured to infuse fluids into a patient.

Infusion pump units generally comprise a pump device to pump fluid to a patient. In certain embodiments of an infusion pump unit, a pressure sensor is provided to determine a pressure in the fluid pressurized by the pump device, and a monitoring unit to monitor the pressure in the fluid.

A blockage in the fluid path from the infusion pump unit to the patient, for example when a fluid conduit through which the fluid is guided is squeezed and blocked, results in an increasing pressure measured by the pressure sensor. To ensure that such blockage is noticed, the monitoring device is configured to provide a warning signal, when the pressure measured by the pressure sensor exceeds a predetermined threshold pressure level.

The warning signal may be used to warn medical personal, for example a nurse, by an audible or visual signal. Also the warning signal may be used to stop the pump device such that the pressure does not further increase.

Next to infusion pump units, devices for locating an anatomical structure, for example an anatomical cavity, in a body are known. These devices are configured to assist a physician in placing a needle in an anatomical cavity of a patient, for example in the epidural cavity of the patient. An embodiment of such device for locating an anatomical structure, in particular an anatomical cavity is for instance disclosed in WO 03/000146 A1.

The present invention provides an infusion pump unit, comprising:

a pump device configured to pump fluid towards a connection device configured to connect a fluid conduit,

a pressure sensor configured to provide a sensor signal representative for a pressure level in the pumped liquid,

a monitoring device configured to monitor the pressure level on the basis of the sensor signal,

characterized in that the infusion pump unit is configured to operate in a detection mode to locate an anatomical structure, for example an anatomical cavity, in the body of a patient, and in an infusion mode to infuse fluid into a patient,

wherein, in the infusion mode, the monitoring device is configured to compare the sensor signal with a threshold pressure value, and to provide a warning signal when the sensor signal exceeds the threshold pressure value, wherein, in the detection mode, the monitoring device is configured to continuously provide on the basis of the sensor signal, a pressure level signal representative of a pressure level and/or pressure variation in the fluid.

The infusion pump unit of the invention is configured to selectively operate in an infusion mode or in a detection mode.

In the infusion mode, the infusion pump unit is configured for conventional use, i.e. for infusion of fluid into a patient.

In the detection mode, the infusion pump unit is configured to assist in locating an anatomical structure, in particular an anatomical cavity in the body of a patient. This assistance is in particular useful in the detection of anatomical structures in which the detection involves a certain risk, such as the epidural space. Therefore, there is a need for devices that can assist in locating the respective anatomical structure. The detection mode can also be used to check the location of a catheter in an anatomical structure.

Stand-alone devices for locating an anatomical cavity such as disclosed in WO 03/000146 A1 are known. However, these devices are not configured for infusion of fluid into patients. Similarly, the known infusion pump devices are not configured to locate anatomical cavities in a patient.

The present invention provides an integrated device configured for infusion of fluid into a patient and for locating an anatomical structure in a body of a patient.

Such integrated device offers a number of advantages. A first advantage is that only a single infusion pump unit is required for both fluid infusion and locating the anatomical structure; as a result, components of the infusion pump unit for similar functions, such as pump device, pressure sensor and monitoring unit can be shared in the single device.

Further, the components of the infusion pump device can be optimized for both functions. Moreover, switching between the infusion mode and the detection mode can be carried out in a simple and reliable manner.

A further advantage is that the combined function of the infusion pump unit, allows to check the location of a catheter in the body, for example just after placement of the catheter or at a later moment. For example, after localization of an anatomical cavity by using, a fluid conduit and the infusion pump unit of the invention, it may be desirable to place a catheter in the anatomical cavity, for example to introduce anesthetics into the anatomical cavity. A catheter is a tube having a relatively small diameter with which the desired fluids can be introduced into the patient.

The distal catheter end can be brought into the anatomical cavity by advancing the distal end of the catheter through a needle of which the distal end is located in the anatomical cavity. When the distal catheter end is located in the anatomical cavity, the needle can be withdrawn from the body of the patient, while the distal catheter end remains in the body. By connecting the proximal end of the catheter to the infusion pump unit, the infusion pump unit can be used, in the infusion mode, in combination with the catheter to infuse fluid into the anatomical cavity.

By activating in this configuration the detection mode, the pressure resistance at the distal catheter end can be determined by measuring a pressure level in the pumped fluid and comparing the measured pressure level with an expected pressure level, i.e. a pressure level or pressure level range associated with a correct location of the catheter in the anatomical cavity.

When the pressure level determined in the detection mode is close to the expected pressure level or within the expected pressure range, it can be concluded that the distal catheter end is still properly located in the anatomical cavity. However, when there is a substantial difference between the expected pressure level or expected pressure level range and the measured pressure level, in particular when the measured pressure level is substantially higher, it can be concluded that the distal catheter end is no longer properly located in the anatomical cavity, but in other tissue providing a higher flow resistance at the distal catheter end.

The expected pressure level or expected pressure level range can be based on pressure levels earlier measured with different patients or with the same patient, for example just after placement of the catheter.

Operating the infusion pump unit alternately in the detection mode and the infusion mode with the same catheter, also obviates the need to decouple the catheter from an infusion pump and couple it to a location detection device, and vice versa, in order to check the location of the distal catheter end.

The pump device of the infusion pump unit may be any suitable pump, but is preferably a pump device configured to pump liquid with a constant flow rate.

The pressure sensor may also be any device configured to continuously measure the pressure prevailing in the liquid pumped by the pump device.

The monitoring device may be any suitable processing device, for example a computer or tablet device.

In an embodiment, the infusion pump unit comprises a switch device configured to switch the infusion pump unit between at least the detection mode and the infusion mode. For operating the infusion pump unit in the detection mode different settings of the infusion pump unit are required than in the infusion mode. Therefore, a switch device to switch between the infusion mode and the detection mode is useful, since this allows for an easy switching between the two operational modes. The switch device may for example comprise two buttons, wherein pressing one button switches the infusion pump unit to detection mode and pressing the other button switches the infusion pump unit to infusion mode. The buttons may for example be physical buttons, but also digital buttons, i.e. buttons displayed on a touchscreen. In alternative embodiments, the switch device may comprise one button, wherein pressing the button results in alternately switching between the infusion mode and the detection mode, or in a temporary activation of the detection mode.

In yet other embodiments, the switch device may comprise a selector knob with which the desired mode can be selected by rotation or sliding of the knob. The switch device may also comprise any other device to switch between the infusion mode and the detection mode.

Preferably, switching of the infusion pump unit between the infusion mode and the detection mode can be carried out by a single action of the user, i.e. pressing a single button or such.

In an embodiment, a pressure level resulting from pumping fluid by the pump device in the detection mode is larger than the threshold pressure level in the infusion mode. In the detection mode a relative high pressure may occur. In known stand-alone devices pressure levels of more than 93.31 KPa (700 mmHg), for example 119.77 KPa (900 mmHg), are used during detection of an anatomical cavity, such as an epidural space.

This pressure level is substantially larger than pressure levels used by conventional infusion pump units to infuse fluid into a patient. This increased pressure level can for example be obtained by increasing the flow rate of fluid pumped by the pump device, in particular by increasing the flow rate of a constant flow rate fluid pump. The flow rate during infusion mode may for example be in the range of 1 - 20 ml/h, preferably 2 - 10 ml/h, while the flow rate during the detection mode may for be increased to above 30 ml/h, preferably above 40 ml/h, for instance in a range between 50 - 100 ml/h.

In conventional infusion pump units a threshold pressure level is present, whereby a monitoring unit is configured to provide a warning signal when this threshold pressure level is exceeded. This threshold pressure level is normally below 79.98 KPa (600 mmHg), for example as low as about 19.99 KPa (150 mmHg).

When this threshold pressure level is exceeded, this is deemed to be caused by a blockage of the fluid pathway between the infusion pump unit and the patient, and a warning signal is issued by the monitoring unit. The warning signal is for example used to activate an acoustic device to give an acoustical signal or a display device to show a visual signal. Also, the warning signal can be used to stop the pump device in order to avoid further increase in pressure in the fluid pathway. In an embodiment, the monitoring device is, in the detection mode, configured to compare the sensor signal with a detection mode threshold pressure value, and to provide a warning signal when the sensor signal exceeds the detection mode threshold pressure value, wherein the detection mode threshold pressure value is at least five times larger than the threshold pressure value in the infusion mode.

The pressure level normally used in detection mode is substantially larger than the pressure level used in infusion mode. Nevertheless, it may be desirable that it is monitored that the pressure level in the fluid does not become too high, for example as a result of squeezing a fluid conduit between the infusion pump unit and the patient. Therefore, also in the detection mode, the monitoring unit may be configured to compare the sensor signal with a detection mode threshold pressure value. When the sensor signal exceeds the detection mode threshold pressure value, a warning signal may be provided by the monitoring device that the pressure in the fluid exceeds the threshold pressure level.

It will be clear that this threshold pressure value will be larger than the operational pressure value of the fluid during the detection mode. As the operational pressure value in detection mode may for example be 119.77 KPa (900 mmHg), the detection mode threshold pressure value in detection mode may be at least 133.32 KPa (1000 mmHg), while the threshold pressure value in the infusion mode may be between about 13.33 KPa (100 mmHg) and about 26.66 KPa (200 mmHg).

However, since the pressure is continuously monitored during detection mode, the comparison of the sensor signal with a detection mode threshold pressure value may also be omitted in the detection mode.

In an embodiment, the monitoring unit is configured to automatically switch from detection mode to infusion mode and/or provide an alarm signal after a predetermined amount of time after activation of the detection mode. In detection mode, higher pressure levels are required in order to properly assist the user, e.g. the physician, during locating an anatomical cavity. To make higher pressure levels possible, the threshold pressure value used in infusion mode is substantially enlarged or the threshold pressure level monitoring is temporarily stopped. The increased pressure level is typically obtained by substantially increasing the flow rate of fluid pumped by the pump device.

It is therefore undesirable that the infusion pump unit remains in detection mode during infusion of a patient. To avoid that the infusion pump unit remains inadvertently in detection mode, the monitoring unit can be configured to automatically switch from detection mode to infusion mode after a predetermined amount of time after activation of the detection mode, for example a duration of time normally required for performing a detection of a location of an anatomical cavity. Such period of time is for example 10-30 minutes. As an alternative, or in addition, the monitoring unit may be configured to provide an alarm signal when the infusion pump unit is unexpectedly long in detection mode.

In the case of automatically switching back to the infusion mode and/or of an alarm signal indicating a long detection mode duration, the detection mode may for example be reactivated by manipulation of the switch device, for example pressing a button.

Additionally or as an alternative, in an embodiment of the infusion pump unit in which the detection mode automatically stops, the infusion pump unit may provide the possibility to prolong activation of the detection mode before the detection mode has actually stopped. For example, a light signal may indicate the last minute of the detection mode. Pressing of a button or another action may prolong the duration of the detection mode.

In an embodiment, the infusion pump unit comprises an acoustic device configured to output an acoustic signal on the basis of the warning signal and/or the detection signal. This acoustic device is for example a loudspeaker. As an alternative, or in addition, the infusion pump unit may comprise a display device to display a pressure level or pressure level variation on the basis of the sensor signal and/or detection signal.

In conventional infusion pump units, the infusion pump unit may comprise a acoustic device, such as a loudspeaker, or a displace device to provide an acoustical or visual alarm signal when the pressure level in the fluid exceeds the threshold pressure level of the infusion pump unit.

This acoustical device and/or display device may also be used to provide detection signals that are used in the process of locating an anatomical structure. In the case of an acoustical signal, the pitch of a sound signal or the frequency of an intermitting sound signal may for example indicate the pressure level or pressure variation in the fluid, which is an indication of the tissue or structure in which a tip of needle connected to the infusion pump unit is located. It may be advantageous to use another sound than the sound of a threshold pressure level being exceeded.

Warning signals may also be used to indicate that the detection mode of the infusion pump unit is active. These warning signals may for example be used to light a warning light, such as a red light, or another device indicating that the detection mode is active.

The invention further relates to a combination of the infusion pump unit of any of the claims 1-14, a fluid conduit and a hollow needle, wherein one end of the fluid conduit is connected to the hollow needle and a second opposite end is connected to a connection device of the infusion pump unit. The combination may further include a catheter that can be advanced through the needle, and that comprises at least one end that is connectable to the connection device of the infusion pump unit. The invention also relates to a method to locate an anatomical structure, for example an anatomical cavity, such as an epidural space in a patient, and to infuse fluid comprising medicine, in particular an anesthetic into the anatomical structure, in particular the anatomical cavity, comprising the steps of:

providing a combination as claimed in claim 15,

locating the anatomical cavity with the needle with assistance of the infusion pump unit in detection mode;

providing a catheter having a distal end and a proximal end,

arranging the distal end in the anatomical cavity through the needle, and connecting the proximal end to the fluid outlet of the infusion pump unit, infusing fluid into the anatomical cavity through the catheter using the infusion pump unit in infusion mode.

In an embodiment, the invention comprises the step of checking the location of the distal catheter end by switching the infusion pump unit to detection mode, and comparing the measured pressure level with an expected pressure level or expected pressure level range associated with a correct location of the distal catheter end.

Further advantages and characteristics of the invention will now be elucidated by description of an embodiment of the invention, whereby reference will be made to the accompanying drawings in which:

Figure 1 shows schematically an embodiment of an infusion pump unit according to the invention.

Figure 1 shows an infusion pump unit generally indicated by reference numeral 1. The infusion pump unit 1 is configured to hold a syringe 2 comprising a cylindrical fluid reservoir 2a and a plunger 2b to push liquid 30 out of the fluid reservoir 2a. A pump device 3 is provided which is connected to the plunger 2b. By actuation of the pump device 3, the plunger 2b can be moved in the longitudinal direction of the fluid reservoir 2a. By moving the plunger 2b into the fluid reservoir 2a infusion fluid can be pushed towards and out of the fluid outlet 4. At the fluid outlet 4 a first end of a fluid conduit 40 is connected. To the other end of the fluid conduit a needle 50 is connected. The connection of the fluid conduit 40 is preferably realized by releasable connection device 41 , such as a Luer-lock. Also the needle 50 is connected to the fluid conduit by a releasable connection device 42, such as a Luer- lock. The pump device 3 is configured to pump the liquid with a constant flow rate, independent of the pressure in the fluid conduit and the flow resistance of the fluid conduit, needle and/or tissue at the distal end of the needle.

The pump device 3 may also be any other pump device configured to pump liquid, but is preferably a pump device configured to pump liquid with a constant flow rate.

The needle 50 can be used to determine the location of an anatomical cavity, such as the epidural space. Once the needle 50 is placed in the anatomical cavity, the needle 50 can also be used to place a distal end 61 of a catheter 60 in the anatomical cavity by advancing the catheter 60 through the needle into the anatomical cavity in which the needle 50 is placed. Once the distal catheter end 61 is placed in the anatomical cavity, the needle 50 can be withdrawn from the body of the patient over the catheter 60, while the distal catheter end 61 remains in the anatomical cavity. After the needle 50 has been removed from the catheter 50, the proximal end 62 of the catheter 60 can be connected to the fluid outlet 4 of the infusion pump unit 1 by connection at the connection device 41.

The catheter 60 can then be used to infuse fluid, for example anesthetics, from the fluid reservoir 2a into the anatomical cavity in which the distal end 61 of the catheter 60 is placed.

The advantage of the infusion pump unit 1 is that it can be used both to locate an anatomical cavity and to infuse liquid into the anatomical cavity. Moreover, the infusion pump unit 1 can be used to check the location of the catheter 60 after it has been placed in the anatomical cavity, as will be explained hereinafter.

The infusion pump unit 1 comprises a pressure sensor 5 configured to determine a pressure level of fluid pumped by the pump device 3. The pressure sensor 5 provides a sensor signal representative for the pressure measured in the fluid. This sensor signal is received by a monitoring unit 6.

The monitoring unit 6 is configured to process the sensor signal and for example provide output signals to a display device 7, a loudspeaker 8 or an output connector 9. The output connector 9 is configured to connect other devices to the infusion pump unit 1.

The infusion pump unit 1 , in particular the monitoring unit may comprise a storage device, such as a hard disk configured to store relevant data, such as the pressure signals received from the pressure sensor 5. Also an external storage device, for example connected to the output connector 9, may be used to store data of interest.

The monitoring unit 6 is connected to a control device 10. The monitoring device 3 and the control device 10 may be formed by separate devices. But in the embodiment of Figure 1 the monitoring device 3 and the control device 10 are integrated in a single processing device, for example a computer device. The control device 10 is configured to send actuation signals to the pump device 3 in order to make the pump device 3 pump fluid at a desired constant flow rate.

The infusion pump unit 1 further comprises a switch device 1 1 that comprises two buttons to activate different operational modes of the infusion pump unit 1. A first button 12 is provided to activate an infusion mode of the infusion pump unit 1 and a second button 13 is provided to activate a detection mode of the infusion pump unit 1. By pressing one of the buttons 12, 13 a respective operational mode, e.g. the detection mode and infusion mode, can be activated therewith automatically deactivating another of the operational modes.

In the infusion mode, the infusion pump unit 1 is configured, as a conventional infusion pump device, to infuse fluid, possibly comprising medication, such as anesthetics, or nutrients, into a patient. Infusions may for example be given intravenously,

subcutaneously, or in the epidural cavity, in particular through the catheter 60.

In the infusion mode, a relatively low pressure, for example 50-150 mmHg, is used to pump the fluid into the patient. The monitoring unit 10 is configured to monitor the pressure prevailing in the fluid. This measured pressure level may for instance be displayed on the display device 7 such that the nurse or physician can easily follow the development of pressure in the course of time.

Generally, it is undesirable that the pressure in the fluid becomes too high as such high pressure may indicate that a blockage occurs in the catheter 60, for example as a result of squeezing the fluid conduit 60. For this reason, the monitoring unit 6 is configured, at least during the infusion mode, to compare the sensor signal of the pressure sensor 5 with a predetermined threshold pressure value, and to provide a warning signal when the sensor signal exceeds the threshold pressure value. The threshold pressure value may for example be 150 mmHg. This means that a warning signal will be provided by the monitoring unit 6 when the measured pressure value exceeds the threshold pressure value of 150 mmHg.

It is remarked that the threshold pressure value is a value that is compared with the sensor signal representative for the pressure. This means that the threshold pressure value does not have to be expressed in the exact pressure value, but in a way that it is

comparable with the sensor signal.

The warning signal of the monitoring unit 6 may be used to activate different actions. In the shown embodiment, this warning signal is used to show a warning symbol on the display device 7 and to produce a warning sound by the loudspeaker 8. Also, the warning signal may be used to activate the control device 10 to send an actuation signal to the pump device 3 to stop pumping fluid in order to avoid that the pressure in the fluid conduit further increases. By pressing the button 13, the detection mode of the infusion pump unit 1 is activated. The detection mode can be used to assist a physician to locate an anatomical cavity in the body of a patient, in particular to locate the epidural cavity of a patient.

In this detection mode, the pressure level of the fluid is continuously monitored and feedback is given to the user on the actual pressure level and/or pressure variation in the fluid. This actual pressure level and its variation indicates to the user what flow resistance the fluid encounters when the fluid leaves the needle 50 at its distal tip. For example, when the needle 50 is moved through tissue with higher density, the fluid will have more difficulty to leave the needle 50 and, as a result, a higher pressure level will be measured by the pressure sensor 5. When the needle tip reaches the epidural cavity or another anatomical cavity, the fluid can easily leave the needle tip and, as a result, the pressure measured by the pressure sensor 5 will suddenly decrease.

The feedback to the user can be given by acoustical signals, such as a changing frequency of an intermittent beep provided by the loudspeaker 8 in dependency of the pressure level or pressure level variation. Also other signals, such as visual signals may be provided. These detection signals may also be taken from the output connector 9 as input for other indication devices. Possible embodiments of useful detection signals and ways of showing them are for example disclosed in WO 03/000146 A1 and WO 2010/071416 A1.

In order to make a useful feedback possible during locating an anatomical cavity, a substantial higher operational pressure level is normally required in the pressurized fluid than the pressure level used in the infusion mode. This increased pressure level can for example be obtained by increasing the flow rate of fluid pumped by the pump device. The flow rate during infusion mode may for example be in the range of 2 - 10 ml/h, while the flow rate during the detection mode may be increased to a range between 50 - 100 ml/h.

The pressure level in detection mode is for example at least 700 mmHg, for example

900 mmHg. Thus, when switching from infusion mode to detection mode by pressing the button 13, the threshold pressure value of the infusion mode should substantially be increased to a level above the operational pressure level, for example above 1500 mmHg or the comparison in the monitoring device should be deactivated to avoid that a warning signal is issued by the monitoring device 6 as a result of the pressure exceeding the threshold pressure value.

As described above, the pressure levels required in order to properly assist the user, e.g. a physician, during locating an anatomical cavity in a patient are substantially higher than the pressure levels used for infusion of a patient. It is therefore undesirable that the infusion pump unit 1 remains in detection mode with high pressure levels during infusion of a patient. To avoid that the infusion pump unit 1 remains inadvertently in the infusion mode, the monitoring unit 6 is configured to automatically switch from the detection mode to the infusion mode after a predetermined amount of time after activation of the detection mode, i.e. a predetermined time after pressing the button 13 to switch the infusion pump unit to the detection mode.

The monitoring unit 6 may also be configured to provide an alarm signal when the infusion pump unit is unexpectedly long in detection mode. In addition, or as an alternative, the monitoring unit 6 may be configured to provide an indication signal to indicate that the detection mode is active. For example, the indication signal may be used to provide a light signal.

The infusion pump unit 1 of Figure 1 is a single unit that can be used both in detection mode and infusion mode. The pump device 3, pressure sensor 5, monitoring unit 6, display device 7, loudspeaker 8, and control device 10 are all mounted in a single housing 14.

This makes a combination of different devices for detection of a location of an anatomical cavity and infusion of a patient superfluous.

Furthermore, switching between the detection mode and the infusion mode is very simple and reliable, by pressing of a single button 12, 13. Such single action switching avoids the need of changing multiple settings in an infusion unit.

The infusion pump unit 1 is in particular useful in medical procedures in which the steps of locating of an anatomical cavity in a patient and infusion of a fluid into the anatomical cavity are to be carried out subsequently.

For example, if the administering of an anesthetic substance is desired in the epidural space of a patient, first a catheter has to be placed in the epidural space, before the infusion can be started. The infusion pump unit 1 may advantageously be used for such procedure.

First, one end of a fluid conduit 40 may be connected to the fluid outlet 4 and a needle 50 may be connected to the other end.

Then, the infusion pump unit 1 is used to assist in placing a needle 50 in the epidural space. For this reason the button 13 is pressed to activate the detection mode. In the detection mode a higher pressure or pressure profile is used to assist the physician in locating the epidural space. In this detection mode the user continuously receives feedback on the pressure or pressure variation to determine whether the tip of the needle has reached the epidural space. During the detection of the anatomical cavity an isotonic fluid can be used.

As soon as the top of the needle 50 has reached the epidural space, the distal catheter end 61 of the catheter 60 can be placed through the needle 50 into the epidural space and the needle 50 can be withdrawn from the epidural space. Then, as described above, the proximal catheter end 62 can be connected to the infusion pump unit 1 , and the infusion mode of the infusion pump unit 1 can be activated by pressing the button 12 of the switch device 1 1.

In the infusion mode, anesthetics can be infused via the catheter 60 into the patient using the infusion pump unit 1.

The infusion pump unit 1 can advantageously be used to check the position of the distal catheter end 61. This location is important as this location is the location where the liquid, for example anesthetics, is introduced into the body of the patient. Although, the catheter 60 may be carefully introduced into the patient, the location is not always correct or the catheter 60 may be dislocated after placement. It is for example possible that the distal catheter end 61 is dislocated due to movements of the patient or pulling of the catheter 60.

To check the location of the distal catheter end 61 , the detection mode may be activated by depression of the button 13. This will increase the pressure level to a higher operational pressure of the detection mode. The actual value of this higher operational pressure depends on the location of the distal catheter end 61. When the distal catheter end

61 is still properly positioned in the epidural space the actual pressure value will be lower than when the distal catheter end 61 has been moved into surrounding tissue in which the flow resistance is higher.

The pressure level value in the epidural space can be based on knowledge obtained from other patients, but may also be obtained by measuring the actual pressure level direct after placement of the catheter 60.

It may be advantageous to measure the pressure level directly after placement of the catheter 60 and compare with values obtained from other patients, and, when this first measured value is close to an expected pressure level or within an expected pressure level range, using this measured actual value to determine at a later stage whether the distal catheter end 61 is still properly position in the epidural space.

Since the infusion pump unit 1 is used both for checking the correct location of the distal catheter end 61 in the epidural space, or another anatomical cavity, and for infusing liquid into the patent, these steps can be carried out without the need of decoupling the catheter 60. This reduces the risk on infections.

Hereinabove, the use of the infusion pump unit 1 in the detection mode has been described to localize an anatomical cavity, in particular the epidural space. It is remarked that the infusion pump unit 1 , in detection mode, can also be used to locate another anatomical structure which is situated in a body which in terms of its properties differs from the area which immediately surrounds it. In this context, consideration may be given, for example, to locate an intumescence or a tumor in the body of a person. A tumor generally has different properties from the surrounding tissue in which it is situated, and in particular the tumor will present a different resistance to the penetration of a fluid compared to the surrounding tissue. If the infusion pump unit according to the invention is used in a similar way to that described above, a sudden change in the measured pressure at a needle point of a needle connected to the unit will indicate that the area which is being looked for has been reached. In this context, it is assumed that pressure variations which occur in the fluid during displacement of the needle in a section of the body which precedes the structure, e.g. region, area, cavity or such, which is to be located are much smaller than the pressure variation which occurs in the fluid when the needle point reaches the said area. It is advantageous if it is known how the structure which is to be located differs from the area which surrounds this structure, so that it is possible to establish with a high degree of certainty that the structure which is to be located has in fact been found.

Claims

1. An infusion pump unit, comprising:

characterized in that the infusion pump unit is configured to operate in a detection mode to locate an anatomical structure in the body of a patient, and in an infusion mode to infuse fluid into a patient,

wherein, in the infusion mode, the monitoring device is configured to compare the sensor signal with a threshold pressure value, and to provide a warning signal when the sensor signal exceeds the threshold pressure value,

wherein, in the detection mode, the monitoring device is configured to continuously provide on the basis of the sensor signal, a pressure level signal representative of a pressure level and/or pressure variation in the fluid.

2. The infusion pump unit of claim 1 , wherein the infusion pump unit comprises a switch device configured to switch the infusion pump unit between at least the detection mode and the infusion mode.

3. The infusion pump unit of claim 2, wherein the switch device comprises at least one button to switch between infusion mode and detection mode or wherein the switch device comprises at least one selector knob to switch between the infusion mode and the detection mode.

4. The infusion pump unit of any of the preceding claims, wherein at least the pump device, the pressure sensor, and the monitoring device are mounted in a single housing.

5. The infusion pump unit of any of the preceding claims, wherein a pressure level provided by the pump device in the detection mode is larger than the threshold pressure level in the infusion mode.

6. The infusion pump unit of claim 5, wherein the threshold pressure value in the infusion mode is smaller than about 79.98 KPa (600 mmHg), and wherein the pressure level in the detection mode is at least 93.31 KPa (700 mmHg).

5 7. The infusion pump unit of any of the preceding claims, wherein, in the detection

mode, the monitoring device is configured to compare the sensor signal with a detection mode threshold pressure value, and to provide a warning signal when the sensor signal exceeds the detection mode threshold pressure value, wherein the detection mode threshold pressure value is at least five times larger than the threshold pressure value in the 10 infusion mode.

8. The infusion pump unit of claim 7, wherein the threshold pressure value in the infusion mode is between about 13.33 KPa (100 mmHg) and about 26.66 KPa (200 mmHg), and wherein the detection mode threshold pressure value is at least 106.64 KPa (800

15 mmHg).

9. The infusion pump unit of any of the preceding claims, wherein the monitoring unit is configured to automatically switch from the detection mode to the infusion mode after a predetermined amount of time after activation of the detection mode.

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10. The infusion pump unit of any of the preceding claims, wherein the infusion pump unit comprises an acoustic device configured to output an acoustic signal on the basis of the warning signal and/or the detection signal.

25 1 1. The infusion pump unit of any of the preceding claims, wherein the infusion pump unit comprises a display device to display a pressure level or pressure level variation on the basis of the warning signal and/or detection signal.

12. The infusion pump unit of any of the preceding claims, wherein the infusion pump 30 unit comprises a control device to control the pump device and the monitoring device in dependency of whether the infusion mode or detection mode is selected.

13. The infusion pump unit of claim 1 1 , wherein the motoring device and the control device are an integral device.

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14. The infusion pump unit of any of the preceding claims, wherein the pump device is configured or instructable by a control device to pump, in the detection mode, fluid according to a predetermined pressure profile.

15. A combination of the infusion pump unit of any of the preceding claims, a fluid conduit and a hollow needle, wherein one end of the fluid conduit is connected to the hollow needle and a second opposite end is connected to a connection device of the infusion pump unit.