Infusion device and method for administering a medical fluid to a patient

Abstract

An infusion device includes a pump for pumping a medical fluid from a fluid container through a delivery line towards a patient at a flow rate, a sensor for measuring a force on the pump or the delivery line, and a processor device configured to derive, from the force measured by the sensor, a pressure value indicative of the pressure in the delivery line and to compare the pressure value to a threshold value for determining whether an occlusion in the delivery line is present. A storage device stores a compliance value associated with the pump and/or the delivery line, and the processor device is configured to compute, from the stored compliance value, the flow rate and the threshold value, an estimate of a duration between the time of an occurrence of an occlusion and the time at which the pressure value exceeds the threshold value.

Claims

1. An infusion device for administering a medical fluid to a patient, comprising: a pumping mechanism for pumping a medical fluid from a fluid container through a delivery line towards a patient at a set flow rate, a sensor device for measuring a force on the pumping mechanism or the delivery line, a processor means for deriving, from the force measured by the sensor device, a pressure value indicative of a pressure in the delivery line, the processor means for comparing the pressure value to a threshold value from a user for determining whether an occlusion in the delivery line is present, and a storage means for storing a compliance value associated with the pumping mechanism and/or the delivery line, the processor means for computing, from the compliance value, the flow rate and the threshold value, a dynamic estimate of a duration between a time of an occurrence of an occlusion in the delivery line and a time at which the pressure value exceeds the threshold value, the storage means for storing a multiplicity of compliance values including the compliance value, the multiplicity of compliance values associated with a multiplicity of different pumping mechanisms and/or delivery lines, and wherein if the pumping mechanism comprises a syringe pump, the compliance value is associated with a syringe used on the syringe pump, the fluid container comprising the syringe, and if the pumping mechanism comprises a volumetric pump, the compliance value is associated with a tubing set used on the volumetric pump, the delivery line comprising the tubing set, the processor means for (i) issuing a warning if the dynamic estimate of the duration exceeds a predetermined limit, (ii) preventing the user from entering the threshold value that led to the dynamic estimate of the duration that exceeded the predetermined limit, (iii) prompting the user to enter another, smaller threshold value, (iv) receiving from the user the another, smaller threshold value, and (v) computing, from the compliance value, the flow rate, and the another, smaller threshold value the dynamic estimate of the duration between the time of the occurrence of the occlusion in the delivery line and the time at which the pressure value exceeds the threshold valve, and repeating (i) to (iv), if necessary.

2. The infusion device according to claim 1, further comprising an input device allowing a user to program the flow rate and/or the threshold value.

3. The infusion device according to claim 1, the processor means for computing the dynamic estimate of the duration according to the following equation: $T=\frac{P_{\mathrm{thres}}.Math.C}{f}$ wherein T represents the duration between the time of occurrence of the occlusion in the delivery line and the time at which the pressure value exceeds the threshold value, P.sub.thres represents the threshold value, C represents the compliance value, and f represents the flow rate.

4. The infusion device according to claim 1, further comprising a display device configured to display the dynamic estimate of the duration.

5. The infusion device according to claim 1, the processor means for computing the threshold value such that the dynamic estimate of the duration is required to fall into a predefined range.

6. A method using an infusion device for administering a medical fluid to a patient, in which: a pumping mechanism pumps the medical fluid from a fluid container through a delivery line towards the patient at a flow rate, a sensor device measures a force on the pumping mechanism or the delivery line, a processor means derives, from the force measured by the sensor device, a pressure value indicative of a pressure in the delivery line, wherein the processor means is configured to compare the pressure value to a threshold value from a user for determining whether an occlusion in the delivery line is present, and a storage means, the method comprising: storing on the storage means a compliance value associated with the pumping mechanism and/or the delivery line, computing using the processor means, from the compliance value stored on the storage means, the flow rate and the threshold value, a dynamic estimate of a duration between a time of an occurrence of an occlusion in the delivery line and a time at which the pressure value exceeds the threshold value, wherein the storage means stores a multiplicity of compliance values including the compliance value, the multiplicity of compliance values associated with a multiplicity of different pumping mechanisms and/or delivery lines, wherein if the pumping mechanism comprises a syringe pump, the compliance value is associated with a syringe used on the syringe pump, the fluid container comprising the syringe, and if the pumping mechanism comprises a volumetric pump, the compliance value is associated with a tubing set used on the volumetric pump, the delivery line comprising the tubing set, and using the processor means, (i) issuing a warning if the dynamic estimate of the duration exceeds a predetermined limit, (ii) preventing the user from entering the threshold value that led to the dynamic estimate of the duration that exceeded the predetermined limit, (iii) prompting the user to enter another, smaller threshold value, (iv) receiving from the user the another, smaller threshold value, and (v) computing, from the compliance value, the flow rate, and the another, smaller threshold value the dynamic estimate of the duration between the time of the occurrence of the occlusion in the delivery line and the time at which the pressure value exceeds the threshold valve, and repeating (i) to (iv), if necessary.

7. The method according to claim 6, wherein computing the dynamic estimate of the duration is performed according to the following equation: $T=\frac{P_{\mathrm{thres}}.Math.C}{f}$ wherein T represents the duration between the time of occurrence of the occlusion in the delivery line and the time at which the pressure value exceeds the threshold value, P.sub.thres represents the threshold value, C represents the compliance value, and f represents the flow rate.

8. The method according to claim 6, further comprising displaying the dynamic estimate of the duration.

9. The method according to claim 6, further comprising, using the processor means, computing the threshold value such that the dynamic estimate of the duration is required to fall into a predefined range.

Description

(1) The idea of the invention shall subsequently be described in more detail with reference to the embodiments shown in the figures. Herein:

(2) FIG. 1 shows a view of an infusion device constituted as a syringe pump;

(3) FIG. 2 shows a schematic diagram of a pressure rise over time in case of an occlusion; and

(4) FIG. 3 shows a view of an infusion device in the shape of a volumetric (peristaltic) infusion pump.

(5) FIG. 1 shows an embodiment of an infusion device 1 in the shape of a syringe pump. 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.

(6) The infusion device 1 comprises a receptacle 12 in which a syringe 2 having a cylindrical tube 20 is arranged. A plunger 21 is movable within the cylindrical tube 20 and is in engagement with a driving element 11 of a pumping mechanism of the infusion device 1. At an end of the cylindrical tube 20 opposite the plunger 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.

(7) The plunger 21 comprises a head 210 facing away from the cylindrical tube 20 and being in abutment with the driving element 11 of the infusion device 1. During operation of the infusion device 1, the driving element 11 is electromotorically driven in an actuation direction A such that the plunger 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.

(8) 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.

(9) 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 plunger 21 is continuously pushed into the cylindrical tube 20 such that a desired flow rate is obtained, which is programmed by a user prior to the start of the infusion operation.

(10) 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 to 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 needle for providing an intravenous access to the patient B. During an infusion process an occlusion O in the delivery line 3 must be avoided and, if it nevertheless occurs, must be detected such that appropriate countermeasures to overcome the occlusion O can be taken. For this, a force sensor 14 is placed on the driving element 11 facing the head 210 of the plunger 214 measuring a force exerted on the plunger 21 during an infusion process. From a force measured by means of the force sensor 14 an estimate of the pressure within the syringe 2 can be obtained, such that the pressure within the syringe 2 and the delivery line 3 can be monitored. If it is found that the pressure within the syringe 2 and the delivery line 3 rises beyond a permissible threshold value, an alarm is triggered indicating that an occlusion O may be present in the system.

(11) FIG. 2 shows in a schematic diagram the pressure P over time tin case of an occlusion O. Generally, the pressure P is very small (almost 0) during normal infusion operation in case no occlusion O is present (see the pressure P prior to the time t0). If at the time t0 an occlusion O occurs, the pressure P will start to rise and will continue to rise (if the occlusion O does not disappear) until a threshold value P.sub.thres is exceeded, at which moment an alarm is triggered by the processor device 15 such that a user is warned of the occlusion O.

(12) The occlusion O, in the example of FIG. 2, occurs at time t0. Until the pressure threshold value P.sub.thres actually is exceeded by the pressure curve P at time t1, a substantial time duration T may pass, due to the continuous rise of the pressure P following the occlusion O at a finite slope, the slope of the pressure rise herein depending on a multiplicity of factors, for example the flow rate and the compliance of the system, in particular the compliance of the cylindrical tube 20 of the syringe 2 and of the delivery line 3 extending in between the cylindrical tube 20 and the patient B.

(13) Generally, the pressure in the delivery line 3 will rise according to the following equation:

(14) $P=\frac{f.Math.t}{C}.$

(15) Herein, P denotes the pressure, f denotes the flow rate, t denotes the time, and C denotes the compliance.

(16) The time duration T also depends on the threshold value P.sub.thres such that by suitably setting the threshold value P.sub.thres the time duration T in between the occurrence of the occlusion O and the time of the alarm can be influenced. The preset threshold value P.sub.thres is for example programmed by a user prior to conducting an infusion process and should be chosen by the user such that the time duration T does not become excessively large (generally, the warning for an occlusion should be triggered in a timely fashion after occurrence of the occlusion O such that the infusion process is not interrupted for too long a time).

(17) To facilitate the setting of the threshold value P.sub.thres for a user, the processor device 15 is constituted to compute an estimate of the time duration T making use of the following equation:

(18) $T=\frac{P_{\mathrm{thres}}.Math.C}{f},$

(19) Herein, P.sub.thres denotes the threshold value, C denotes the compliance and f denotes the flow rate. Upon programming the threshold value P.sub.thres by a user, the processor device 15 immediately computes the estimate of the duration T and outputs the estimate to the user such that the user obtains a feedback about an estimate of the expected time in between the actual occurrence of an occlusion and the time at which an alarm the triggered during the actual infusion operation of the infusion device 1.

(20) The compliance value C associated with the syringe 2 and the delivery line 3 is stored in the storage device 16 of the infusion device 1. The storage device 16 in this regard may store a multiplicity of compliance values C for different syringes 2 and different delivery lines 3 such that, by inputting for example the type of syringe 2 to the infusion device 1, the processor device 15 may refer to the compliance value C associated with the particular syringe 2 used on the system for computing the estimate of the duration T.

(21) The storage device 16 may for example store a compliance value for a syringe 2 of a particular manufacturer and a particular volume. The storage device 16 may in addition store a default value for a syringe 2 of a particular volume, which may be used in case a particular syringe 2 of a particular manufacturer is not explicitly defined in the infusion device 1. A delivery line 3 may be identified by its length, its inner and/or outer diameter or the like and by its manufacturer, and associated with a particular type of delivery line 3 a particular compliance value may be stored in the storage device 16.

(22) The storage device 16 may store a constant value for the compliance. Just as well it is conceivable that the storage device 6 stores a nonlinear relation for the compliance depending for example on the pressure in the system.

(23) The computation of the estimate of the duration T may be used to provide a feedback to the user upon programming the threshold value P.sub.thres. If the threshold value P.sub.thres exceeds a predetermined limit, for example 30 minutes, in addition a warning may be triggered to the user, or the user may be prevented from entering a threshold value P.sub.thres which causes the duration T to rise beyond the predefined limit.

(24) Alternatively, the infusion device 1 may be constituted to set the threshold value P.sub.thres automatically such that the threshold value P.sub.thres falls within a predefined range. For example, upon programming the flow rate the system may set the threshold value P.sub.thres automatically such that the threshold value P.sub.thres is below for example 15 minutes and above for example 5 minutes.

(25) 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.

(26) 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.

(27) 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 pump 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.

(28) 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. In the storage device 16 a compliance value of the tubing set 3 may be stored, wherein different compliance values for different tubing sets 3 of different types and of different manufacturers may be stored. The processor device 15 controls the operation of the infusion device 1 and, from the readings of a force sensor 14 measuring a force on the downstream tube section 320, the pressure P in the downstream tube section 320 may be determined and may be observed in order to detect an occlusion O in the system.

(29) The invention is not limited to the embodiments described above, but can be carried out in an entirely different fashion. In particular, the invention generally is applicable to different kinds of infusion devices used for different purposes for administering a medical fluid into a patient.

LIST OF REFERENCE NUMERALS

(30) 1 Infusion device 10 Housing 100 Front face 101 Receptacle 102 Channel 103 Housing element (door) 11 Pumping mechanism 12 Receptacle 13 Display device 14 Force sensor 15 Processor device 16 Storage device 2 Pumping device (syringe) 20 Cylindrical tube 21 Plunger 210 Head 3 Delivery line 30, 31 End 32 Pump module 320, 321 Tube section A Actuation direction B Patient D Pivoting axis O Occlusion P Pressure P.sub.thres Pressure threshold t time T Duration