INFUSION DEVICE SUITABLE TO TEST FOR EXTRAVASATION

Abstract

An infusion device (1) for administering a medical fluid to a patient (P) comprises a pumping mechanism (11) for pumping a medical fluid through a delivery line (3), and a processor device (15) for controlling the pumping mechanism (11), during an infusion operation, to pump the medical fluid through the delivery line (3) in a downstream direction (F1). Herein, the processor device (15) is constituted to perform, prior to an infusion operation, a test function during which the processor device (15) controls the pumping mechanism (11) to pump the medical fluid through the delivery line (3) in an upstream direction (F2) opposite the downstream direction (F1). In this way an infusion device is provided that supports a user, in particular a nurse, to perform an infusion operation, in particular to set up the infusion device for performing the infusion operation.

Claims

1. An infusion device for administering a medical fluid to a patient, comprising: a pumping mechanism for pumping a medical fluid through a delivery line, and a processor device for controlling the pumping mechanism, during an infusion operation, to pump the medical fluid through the delivery line in a downstream direction, wherein the processor device is configured to perform, prior to an infusion operation, a test function during which the processor device controls the pumping mechanism to pump the medical fluid through the delivery line in an upstream direction opposite the downstream direction.

2. The infusion device according to claim 1, further comprising a sensor device for measuring a measurement value indicative of a pressure in the delivery line, wherein the processor device is configured to evaluate, during the test function, measurement values obtained from the sensor device to identify a change in pressure in the delivery line during the test function.

3. The infusion device according to claim 1, further comprising an input device enabling a user to input a control command to trigger the processor device to perform the test function.

4. The infusion device according to claim 1, further comprising an output device for outputting information relating to a change in pressure during the test function.

5. The infusion device according to claim 1, wherein the control device is configured to terminate the test function according to at least one criteria observed during the performing of the test function.

6. The infusion device according to claim 1, wherein the control device is configured to terminate the test function in case the pressure in the delivery line falls under a predetermined negative pressure threshold.

7. The infusion device according to claim 1, wherein the control device is configured to terminate the test function in case the volume of fluid pumped in the upstream direction during the test function exceeds a predetermined maximum volume.

8. The infusion device according to claim 1, wherein the control device is configured to terminate the test function in case an input device is released.

9. The infusion device according to claim 1, wherein the control device is configured to control the pumping mechanism, after termination of the test function, to pump fluid through the delivery line in the downstream direction to reinject fluid pumped in the upstream direction during the test function.

10. The infusion device according to claim 9, wherein the control device is configured to control the pumping mechanism to reinject a volume of fluid matching the volume of fluid pumped in the upstream direction during the test function.

11. The infusion device according to claim 1, wherein the infusion device is a syringe infusion pump or volumetric infusion pump.

12. A method for operating an infusion device for administering a medical fluid to a patient, comprising: pumping a medical fluid through a delivery line using a pumping mechanism, controlling, using a processor device, the pumping mechanism, during an infusion operation, to pump the medical fluid through the delivery line in a downstream direction, and performing, prior to an infusion operation, a test function during which the processor device controls the pumping mechanism to pump the medical fluid through the delivery line in an upstream direction opposite the downstream direction.

13. The method according to claim 12, further comprising measuring a measurement value indicative of a pressure in the delivery line using a sensor device, wherein the processor device evaluates measurement values obtained from the sensor device to identify a change in pressure in the delivery line during the test function.

Description

[0034] The idea of the invention shall subsequently be described in more detail with reference to the embodiments shown in the figures. Herein:

[0035] FIG. 1 shows a view of an infusion device constituted as a syringe pump;

[0036] FIG. 2 shows a graphical view of the measured pressure during a reverse pumping operation; and

[0037] FIG. 3 shows a view of an infusion device constituted as a volumetric (peristaltic) infusion pump.

[0038] FIG. 1 shows an embodiment of an infusion device 1 in the shape of a syringe pump.

[0039] The infusion device 1 comprises a housing 10 having a front face 100 and a display device 13 arranged thereon. The display device 13 may for example be a touch-sensitive display allowing a user to enter commands for operation of the infusion device 1 and displaying operational information regarding the process of an actual infusion operation.

[0040] The infusion device 1 comprises a receptacle 12 in which a syringe 2 having a cylindrical tube 20 is arranged. A piston 21 is movable within the cylindrical tube 20 and is in engagement with a pusher device 11 of a pumping mechanism of the infusion device 1. At an end of the cylindrical tube 20 opposite the piston 21 a delivery line 3 extends from the cylindrical tube 20 towards a patient B, the delivery line 3 being connected to the cylindrical tube 20 at an end 30 and to the patient B at an end 31.

[0041] The piston 21 comprises a head 210 facing away from the cylindrical tube 20 and being in abutment with the pusher device 11 of the infusion device 1. The piston head 210, when the syringe 2 is placed in the receptacle 12, is fixed to the pusher device 11 by means of a clamping device 110 reaching around the piston head 210, such that the piston head 210 is held in tight abutment with the pusher device 11. During operation of the infusion device 1, the pusher device 11 is electromotorically driven in an actuation direction A such that the piston 21 is moved into the cylindrical tube 20 and a medical fluid contained in the cylindrical tube 20 is delivered via the delivery line 3 towards the patient B.

[0042] The infusion device 1 comprises a processor device 15 and a storage device 16. Via the processor device 15 the infusion operation of the infusion device 1 is controlled. In the storage device 16 operational parameters, such as mechanical characteristics of the syringe 2 used on the infusion device 1 as well as operational data, may be stored.

[0043] During an infusion process a medical fluid, for example a medication or a nutritional fluid for the parenteral feeding of a patient or the like, is delivered from the cylindrical tube 20 via the delivery line 3 towards the patient B. For this, the piston 21 is continuously pushed into the cylindrical tube 20 in the actuation direction A such that a desired flow rate is obtained, which is programmed by a user prior to the start of the infusion operation.

[0044] The delivery line 3 generally is made of a flexible tubing made for example from a PVC material. The delivery line extends from the cylindrical tube 20 towards the patient B and is, at its first end 30, in fluid connection with the cylindrical tube 20 and, at its second end 31, for example connected to a catheter for providing an intravenous access to the patient B.

[0045] In between the pusher device 11 and the piston head 210 a force sensor 14 is placed which measures the force exerted on the piston head 210. The force sensor 14 is capable to measure a force when actuating the pusher device 11 to push the piston 21 in the actuation direction A into the cylindrical tube 20 in order to deliver a medical fluid from the cylindrical tube 20 in a downstream direction F1 towards the patient B. Likewise, due to the tight abutment in which the piston head 210 is held on the pusher device 11 by means of the clamping device 110, the force sensor 14 is capable also to measure the force between the pusher device 11 and the piston head 210 in case the pusher device 11 is actuated in a direction opposite to the actuation direction A such that the piston 21 is pulled out of the cylindrical tube 20 and a fluid is drawn in an upstream direction F2 through the delivery line 3.

[0046] The pusher device 11 and the force sensor 14 arranged thereon may for example be constituted as described in WO 2012/123417 A1, whose contents shall be incorporated by reference herein.

[0047] It is to be noted in particular that the infusion device 1 is constituted to measure the (positive) force during a regular infusion operation while pushing on the piston 21 of the syringe 2 and the (negative) force during a reverse pumping action while pulling on the piston 21.

[0048] To observe the pressure in the delivery line 3, the force applied to the piston head 210 of the piston 21 by means of the pusher device 11 is measured by the sensor 14 placed in between the pusher device 11 and the piston head 210 and abutting the piston head 210 for example with an elastic pretension. The force measured in this way allows for an indirect measurement of the pressure within the cylindrical tube 20, which generally equals the pressure in the delivery line 3.

[0049] The pressure in the cylindrical tube 20 during an infusion operation (during which the pusher device 11 pushes the piston 21 in the actuation direction A into the cylindrical tube 20) depends on the measured force according to the following relation:

[00001]$P=\frac{F-F_0}{S}.$

[0050] Herein, P denotes the pressure, F denotes the measured force, F.sub.0 denotes a frictional force component and S denotes the effective surface by which the piston 21 acts onto the fluid contained in the cylindrical tube 20. The effective surface S is substantially determined by the inner diameter of the cylindrical tube 20. Whereas F is measured and S is known from the geometrical dimensions of the cylindrical tube 20 of the syringe 2, the frictional force component F.sub.0 may be assumed as constant or may be determined for a particular syringe 2 using a calibration or a modeling. F.sub.0 may dependent on the particular syringe 2 used and on the position of the piston 21 within the cylindrical tube 20.

[0051] During a reverse pumping, i.e. during a pulling of the piston 21 out of the cylindrical tube 20 by actuation of the pusher device 11 in a direction opposite to the actuation direction A, the pressure in the delivery line 3 can be deduced from the sensor readings of the force sensor 14 using the equation:

[00002]$P=\frac{F+F_0}{S}$

[0052] Hence, taking into account that the frictional force F.sub.0 opposes the movement and hence changes signs, for deriving the pressure P in the delivery line 3 during the reverse pumping in the upstream direction F2 the frictional force component F.sub.0 is used with opposite sign as compared to the equation noted above for the for the pumping in the forward, downstream pumping direction F1. Again, F is the force value measured by the force sensor 14, and S denotes the effective surface by which the piston 21 of the syringe 2 acts onto fluid contained in the cylindrical tube 20 of the syringe 2, determined by the inner parameter of the cylindrical tube 20. During reverse pumping, the measured force F can be expected to be negative, due to a pulling force exerted on the piston 21. If the measured force F during the reverse pumping is smaller thanF0, the (estimated) pressure P in the infusion line becomes negative.

[0053] Prior to starting an infusion operation, it must be made sure that a catheter linked to the delivery line 3 is correctly placed in the patient B and accesses the infusion route desired. In particular, if an intravenous infusion shall be performed, it must be made sure that the catheter is correctly placed in the vein that shall be accessed. If the catheter is not placed correctly in the patient B (because the catheter for example has missed the vein or has punctured the vein's wall) a potential risk of extravasation exists, i.e. a leaking of a (e.g.) vesicant fluid or medication into the surrounding tissue, which may bear the risk of severe injury for the patient B.

[0054] To check for the correct placement of the catheter, the processor device 15 of the infusion device 1 is constituted to perform a test function prior to the start of an infusion operation. The infusion device 1, in the embodiment shown in FIG. 1, comprises a number of dedicated buttons 104, one of which may be dedicated to the performing of the test function. If a user presses the button 104 associated with the test function, the infusion device 1 may automatically start and perform the test function. Herein, in one embodiment it may be provided that the test function is carried (at maximum) as long as a user presses the button 104. Hence, the user may be required to keep pressing the button 104 during performance of the test function, a release of the button 104 leading to a termination of the test function.

[0055] During the test function, the processor device 15 controls the pusher device 11 to actuate the piston 21 in a direction opposite to the actuation direction A. Hence, fluid is pumped in the upstream direction F2 such that body fluid is aspirated from the patient B. During the reverse pumping, the force on the piston 21 is measured by means of the force sensor 14 and the pressure in the delivery line 3 is monitored by the processor device 15.

[0056] Generally, if the catheter is placed correctly in the patient B and a reverse pumping is initiated, body fluid will be drawn out of the patient B at low resistance. In case the catheter is (correctly) placed in a vein of the patient B for an intravenous infusion, blood is aspirated. In case of a correct placement of the catheter, the pressure in the delivery line 3 will only slightly become negative (i.e., a small negative pressure will develop in the delivery line 3 due to the sucking force of the piston 21).

[0057] In case of an incorrect placement, in contrast, the resistance for drawing body fluid from the patient B is substantially increased, leading to a substantial drop in the pressure in the delivery line 3. Hence, a substantial negative pressure in the delivery line 3 will develop, which can be evaluated by the processor device 15 and which for example can be displayed on the display device 13 such that a user is noticed of the abnormal pressure drop in the delivery line 3.

[0058] For example, the processor device 15 may display a curve of the pressure on the display device 13. Alternatively or in addition, information relating to the absolute pressure drop and/or a slope of the pressure drop may be displayed on the display device 13.

[0059] The test function, during which fluid is reversely pumped in the upstream direction F2 by moving the pusher device 11 and (together with the pusher device 11) the piston 21 opposite to the actuation direction A, may be performed for a predetermined amount of time or for a predetermined volume. In the latter case, if it for example is found that the volume pumped in the upstream direction F2 is equal to or exceeds a predefined maximum value, the test function may be stopped.

[0060] In addition or alternatively, as illustrated in FIG. 2, the (negative) pressure in the delivery line 3 may be compared to a negative pressure threshold P.sub.thres. If, in the example of FIG. 2, the test function is initiated at time t1 and the pressure in the infusion line 3 becomes smaller than the negative pressure threshold P.sub.thres at the time t2, the test function may be terminated at the time t2 and a corresponding warning message may be displayed on the display device 13.

[0061] When an abnormal condition during the test function arises, for example due to the pressure in the infusion line 3 dropping below the negative pressure threshold P.sub.thres, a warning message can be displayed on the display device 13 comprising relevant information about the pressure drop and/or a text message warning about a potential wrong placement of the catheter, wherein alternatively or additionally an acoustic alarm message may be triggered.

[0062] After termination of the test function, the processor device 15, in one embodiment, controls the pusher device 11 to pump a volume of fluid in the downstream direction F1 to reinject the volume of fluid that has been reversely pumped during the test function. Hence, the body fluid aspirated during the test function is redelivered to the patient B. Beneficially, the volume of fluid pumped in the upstream direction F2 during the test function matches the volume of fluid which is reinjected after termination of the test function in the downstream direction F1, such that the net sum of the pumped fluid is zero.

[0063] The invention is not limited to syringe pumps as shown in FIG. 1. Rather, as illustrated in FIG. 3, the invention likewise is applicable also to volumetric pumps.

[0064] In the example of FIG. 3, an infusion device 1 is constituted as a volumetric (peristaltic) infusion pump having a housing 10 and a front face 100 comprising a receptacle 101 in which a pump module 32 of an infusion set 3 can be received. A housing element 103 (also denoted as the door) is pivotable about a pivoting axis D relative to the housing 10 and can be approached towards the front face 100 such that in a closed state the tubing set 3 is held on the infusion device 1.

[0065] From the pump module 32 tube sections 320, 321 extend. Of these tube sections 320, 321, an upstream tube section 321 connects the pump module 32 to a container containing a medical fluid, whereas a downstream pump section 320 connects the pump module 32 to a patient B for delivering the medical fluid towards the patient B. The infusion device 1 comprises a pumping mechanism 11 (illustrated only schematically in FIG. 3) having for example a wobbling device acting onto the pump module 32 for peristaltically pumping a medical fluid through the tubing set 3 towards the patient B.

[0066] The invention may be implemented in the infusion device 1 according to FIG. 3 in an analogous fashion as described above, such that it shall be referred to the above. Herein, the pumping mechanism 11 of the infusion device 1 is constituted to pump fluid in the downstream direction F1 during a regular infusion operation and in the upstream direction F2 when performing the test function.

[0067] The idea of the instant invention is not limited to the embodiments described above, but may be carried out in an entirely different way in entirely different embodiments.

LIST OF REFERENCE NUMERALS

[0068] 1 Infusion device [0069] 10 Housing [0070] 100 Front face [0071] 101 Receptacle [0072] 102 Channel [0073] 103 Housing element (door) [0074] 104 Input device [0075] 11 Pumping mechanism (pusher device) [0076] 110 Clamping device [0077] 12 Receptacle [0078] 13 Display device [0079] 14 Force sensor [0080] 15 Processor device [0081] 16 Storage device [0082] 2 Pumping device (syringe) [0083] 20 Cylindrical tube [0084] 21 Piston [0085] 210 Piston head [0086] 3 Delivery line [0087] 30, 31 End [0088] 32 Pump module [0089] 320, 321 Tube section [0090] A Actuation direction [0091] B Patient [0092] D Pivoting axis [0093] F1 Downstream direction [0094] F2 Upstream direction [0095] P Pressure [0096] P.sub.thres Pressure threshold [0097] t time