WO1999058178A1

WO1999058178A1 - Infusion pump calibration device and method

Info

Publication number: WO1999058178A1
Application number: PCT/IL1999/000244
Authority: WO
Inventors: Nimrod Lev; Talmon Rabinovitz
Original assignee: Infutec Medical Systems Ltd.
Priority date: 1998-05-13
Filing date: 1999-05-10
Publication date: 1999-11-18
Also published as: AU3727399A

Abstract

A system comprising an infusion pump for cooperating with a flexible tube segment of a medicinal liquid infusion set which comprises a tubing for pump-control delivery of a liquid from an inlet and to an outlet end of the tubing, the system comprises a calibrating device having a liquid inlet port connectable to the outlet end, a liquid outlet port, a precise flow rate measurement unit for measuring flow rate of liquid between the inlet and the outlet port, a signal data port connectable to the pump for transmission of flow rate control signal from the device to the pump and a processor unit for issuing a nominal flow rate control signal to the pump through the signal data port to induce the pump to deliver liquid through the tube at a nominal rate corresponding to the control signal, and for comparing the nominal flow rate with the actual flow rate measured by the measurement unit and issuing calibration data for correcting pump flow rate set up in order to obtain the nominal flow rate.

Description

INFUSION PUMP CALIBRATION DEVICE AND METHOD

FIELD OF THE INVENTION

The present invention relates to an improvement in a system for infusing medicinal liquid from a liquid source to an individual, of the kind which comprises a peristaltic pump, or a syringe pump that induces flow in a liquid flow set. Peristaltic pumps and syringe pumps will hereinafter be referred to collectively as "infusion pumps ".

BACKGROUND OF THE INVENTION

Infusion sets typically comprise an integral piece of tubing leading liquid from a liquid container, typically a liquid bag, connectable to its one end, to a needle or a catheter connected to its other end. The tubing usually comprises also a drip chamber which allows to determine the drop rate by monitoring the drops in the chamber.

Modern infusion systems typically operate with a peristaltic or syringe pump which cooperates with a flexible tube segment of an infusion set for delivery of liquid through the tubing at a controlled rate. The actual flow rate depends on the pump's set up as well as on the exact parameters of the cooperating flexible tube segment. For example, the precise dimensions of the lumen of the flexible tube segment, may significantly affect the actual flow rate. The actual flow rate also depends on other parameters including, for example, the flexibility of this tube segment. Different infusion sets, particularly sets of different manufacturers, as well as at times different batches of sets manufactured by the same manufacturer, may differ in the exact physical and mechanical parameters of the pump-cooperating flexible tube segment. Many times, in order to increase accuracy, each pump is designed to work with an infusion set of a specific manufacturer. However, this by itself, in addition to the limitation of reducing the hospital's flexibility to purchase sets from different manufacturers, and render it bound to a single manufacturer, does not solve the problem of changes between different batches. Some infusion pumps which are currently available, are pre-programmed to allow them to work with infusion sets of different manufacturers. In such pumps, the user typically puts in the indication of the specific infusion set which is being used, and the pump can then make some adjustment in the flow rate, according to pre-programmed data, to somewhat change its rate to yield a flow rate close to that which is desired.

In current economic environments, hospitals as well as other healthcare providers, need to make cost considerations and therefore desirably

- employ economical considerations in their purchase of medical supply, including disposables. As infusion sets are widely used commodities in today's medical environment, it would be highly desirable for a hospital or any other healthcare provider, to base its purchased consideration of infusion sets, on economically-guided considerations. However, the changes in the actual parameters, noted above, which influence the actual flow rate of infusion sets, typically limit the hospital to buy infusion sets from one or only a few suppliers.

GENERAL DESCRIPTION OF THE INVENTION

It is an object of the invention to provide means which would allow to calibrate a pump accurately to administer liquid at a desired flow rate, regardless of the exact physical/mechanical parameters of the flexible tube segment of a specific flow set.

The present invention provides, by a first of its aspects, a system comprising an infusion pump for cooperating with a flexible tube segment of a medicinal liquid infusion set which comprises a tubing for pump-controlled delivery of a liquid from an inlet end to an outlet end of the tubing, characterized in that: the system comprises a calibrating device having a liquid inlet port connectable to said outlet end; a liquid outlet port; a precise flow rate measurement unit for measuring flow rate of liquid between the inlet and the outlet port; a signal data port connectable to the pump for transmission of a flow rate control signal from said device to the pump; and a processor unit for issuing a nominal flow rate control signal to the pump through said signal data port to induce the pump to deliver liquid through the tube at a nominal rate corresponding to said control signal, and for comparing the nominal flow rate with the actual flow rate measured by said measurement unit and issuing calibration factor for correcting pump flow rate set up in order to obtain said nominal flow rate.

The present invention provides, by another of its aspects, a method for calibrating an infusion pump to deliver liquid through a liquid infusion set at an actual rate corresponding to a nominal set up rate, the liquid infusion set having tubing for pump-controlled delivery of liquid from an inlet end to an outlet end of the tubing, the method comprising:

(a) inducing the pump to deliver liquid through the set at a first nominal rate;

(b) passing the delivered liquid through a calibration device and measuring the first actual rate of liquid flow therethrough;

(c) comparing the nominal flow rate with the actual flow rate to obtain a calibration factor; and (d) inputting data, based on said first calibration factor, to correct the flow rate of the pump such that when set to the first nominal rate, the actual flow rate will correspond thereto.

As will be appreciated, steps (a)-(c) of the above method may be repeated by inducing the pump to deliver liquid at one or more different nominal flow rates, i.e. a second nominal flow rate, a third nominal flow rate, etc., measure corresponding second actual flow rate, third actual flow rate, to obtain respective calibration factors, and then the input to the pump will be based on a combination of these. In addition, repeated measurements at the same flow rate may also be performed.

By a further aspect of the present invention, the system is also suitable for calibrating a pump accurately to administer liquid at a desirable pressure. Accordingly, the calibration device comprises also a precise pressure measurement unit for measuring pressure between the inlet and the outlet ports; a second signal data port connectable to the pump for transmission of a pressure control signal from the device to the pump; a processor unit for issuing a nominal pressure control signal to the pump through the second signal data port to induce the pump to deliver liquid through the tube at a nominal pressure corresponding to said pressure control signal and for comparing the nominal pressure with the actual pressure measured by the pressure measurement unit and issuing a pressure calibration factor for correcting the pump pressure set up in order to obtain the nominal pressure.

By a further aspect, the invention also provides a method for calibrating an infusion pump to deliver liquid through a liquid infusion set at an actual pressure corresponding to a nominal pressure rate, the liquid infusion set having tubing for pump-control delivery of liquid from an inlet and to an outlet end of the tubing, the method comprising:

(a) inducing the pump to deliver liquid through the set at a first pressure rate; (b) passing the delivered liquid through a pressure calibrating device and measuring the first actual liquid pressure therethrough;

(c) comparing the nominal pressure rate with the actual pressure rate to obtain a pressure calibration factor; and (d) inputting data, based on the first pressure calibration factor, to correct the pressure rate of the pump such that when set to a first nominal pressure rate, the actual pressure rate will correspond thereto.

The term "corresponding" used above and further below means to denote the actual flow rate which is identical or essentially identical (with the difference being very small) to the nominal flow rate.

The invention will now be illustrated in the following non limiting description of some preferred embodiments, with occasional reference to the annexed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a general view of a system in accordance with the invention;

Fig. 2 is a block diagram illustration of the system's components; Fig. 3 shows a typical calibration scheme of the system of the invention; Fig. 4 illustrates a general view of a system according to the invention in one with a syringe pump.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring first to Fig. 1, there is shown a system generally designated 20 comprising a liquid infusion set 22 consisting of a tubing 24 optionally provided with a drip chamber 26, a roller clamp 28. Tubing 24 has an inlet end .30 connected to a liquid bag or container 32 and an outlet end 34. The liquid infusion set 22 further comprises a flexible tube segment at 36 (not seen) incorporated within a peristaltic pump unit 40. The peristaltic pump unit has a control panel 42 for inputting a nominal flow set up value. The pump 40 is connected to an optical drop counter 44 for counting drops in drip chamber 26, for internal control of the pump's flow rate and further to provide an alert when bag 32 is completely drained. The system further comprises a calibration unit 50 having a liquid inlet port 52, a liquid outlet port 53, a control panel 54 and a display 55 and a first and second data ports 56 and 58. Data port 56 is connected via a cable 60, typically an RS232 communication cable, to pump 40, and data port 58 is connected through communication cable 64 to computer 66. It will be appreciated by a skilled person that other connections are possible as well.

It should be noted that data port 58 and computer 66 are optional components and are used in embodiments, where it is desired to record and maintain the calibration parameters characterizing each batch of a liquid infusion set. The different modules of the system of the invention can be seen in Fig. 2, in which the same reference numerals have been used to designate the same component.

Included within calibration unit 50 is a flow meter typically having a rigid tube 72 with a precisely known diameter associated with an flow measurement unit 74 which in the present embodiment is an ultrasonic flow measurement unit. Unit 74 is connected to an analog-to-digital (A-D) converter 76 which is in turn connected to a central processing unit (CPU) 78. Thus CPU 78 receives a digital data input at 80 indicative of the flow rate measured by unit 74. CPU 78 can issue a flow rate command signal from port 84 which is transmitted to pump 40 through line 60A and the compensation data signal from port 86 which is transmitted to pump 40 through line 60B.

CPU 78 is connected to control panel 54 through line 90 and to display 55 through line 92. Unit 50 further comprises, as optional components, a pressure sensor 96 and a valve 98 which communicate with CPU 78 via communication lines 100 and 102, respectively. Pressure sensor 96 measures the pressure in the flow line between ports 52 and 53, which information can then be used for pressure calibration and can further be correlated with the data acquired by unit 74.

A typical calibration process is illustrated in Fig. 3. The user inputs a start calibration command 110, by pressing appropriate one or more keys of control panel 51. At a first step 112, the CPU 78 issues a zero rate control command to pump 40, setting the pump to the zero flow rate (no flow) state. Flow rate is then measured to confirm that indeed no liquid flows through module 70. In case flow is detected, a flow-indicating signal is issued, which may be an audio signal, a signal displayed on display 55, a signal displayed on the display of computer 66. At a next step 114 a rate control command is issued to induce the pump to operate at a certain nominal pumping rate, e.g. at a rate of 50 ml/hr. The pump is allowed to operate at this rate for a period of time, e.g. 30 minutes, and the actual flow rate is then compared to the nominal flow rate.

This may subsequently be repeated with different flow rates, e.g. 200 ml/hr for 15 minutes, and then 900 ml/hr for an additional 10 minutes, corresponding with steps 116 and 118, respectively.

A flow calibration curve comparing actual flow rate with nominal flow rate may then be derived from these steps to allow the generation of a mathematical calibration matrix 120 for correcting the pump to achieve a desired flow rate at a given nominal flow rate set up of the pump. This mathematical matrix 120 may then be used for all liquid infusion sets of the same batch. .

Optionally, the calibration process may include an additional intermediate step 122 between steps 118 and 120, which is an automatic 8

pressure calibration step. Valve 98 is closed and pump 40 is activated at a high rate (e.g. 600 ml/hr) at pressures of 0.3 bar and 1 bar measured by sensor 96, where signals are being transferred to the CPU 78 and a mathematical pressure matrix is then calculated for pressure calibration. Calibrating the pressure built up by the pump is an important feature which is significant in determining mishaps such as fluid flow blocks in the tubing or in the catheter connected to a patient or even in a blood vessel to which the infusion set is connected. Accordingly, a calibration device 50 is fitted with the pressure sensor 96 cooperating with the CPU 78 whereby a pressure calibrating curve comparing actual pressure rate with nominal pressure rate may be derived from steps similar to the steps described above in connection with deriving a flow calibration curve, for correcting the pump to achieve a desired pressure rate.

It will be understood that processor unit (CPU) 78 may be used both for the flow calibration and the pressure calibration procedures and the same or other control lines may be used, as may be required.

Fig. 4 is in principle similar to Fig. 1, wherein the infusion pump is a syringe pump 130 wherein an end 132 of tubing 24 cooperates with the syringe 134. All the other components of the embodiment in this figure are similar to components discussed hereinabove and the skilled person will have no difficulties in understanding their cooperation.

It will be appreciated by the artisan that the above illustrated embodiments are an example only and a variety of different configurations, all within the scope of the invention as defined in the appended claims are possible.

Claims

CLAIMS:

1. A system 20 comprising an infusion pump 40 for cooperating with a flexible tube segment 24 of a medicinal liquid infusion set 22 which comprises a tubing for pump-control delivery of a liquid from an inlet 30 and to an outlet end 34 of the tubing, characterized in that: the system comprises a calibrating device 50 having a liquid inlet port 52 connectable to said outlet end 34; a liquid outlet port 53; a precise flow rate measurement unit 74 for measuring flow rate of liquid between the inlet 52 and the outlet port 53; a signal data port 56 connectable to the pump 40 for transmission of flow rate control signal from said device 50 to the pump 40; and a processor unit 78 for issuing a nominal flow rate control signal to the pump 40 through said signal data port 53 to induce the pump 40 to deliver liquid through the tube 34 at a nominal rate corresponding to said control signal, and for comparing the nominal flow rate with the actual flow rate measured by said measurement unit 74 and issuing calibration data for correcting pump flow rate set up in order to obtain said nominal flow rate.

2. A method for calibrating an infusion pump 40 to deliver liquid through a liquid infusion set 22 at an actual rate corresponding to a nominal set up rate, the liquid infusion set 22 having tubing 24 for pump-control delivery of liquid from an inlet end 30 to an outlet end 34 of the tubing, the method comprising:

(a) inducing the pump 40 to deliver liquid through the set 22 at a first nominal rate; (b) passing the delivered liquid through a calibration device 50 and measuring the first actual rate of liquid flow therethrough;

(c) . comparing the nominal flow rate with the actual flow rate to obtain a calibration factor; and 10

(d) inputting data, based on said first calibration factor, to correct the flow rate of the pump such that when set to the first nominal rate, the actual flow rate will correspond thereto.

3. A method according to Claim 2, comprising additional step after step (c):

(cl) repeating the procedure of steps (a)-(c) with one or more additional nominal flow rates, different than the first nominal flow rate, measuring respective actual flow rates to obtain said calibration factor.

4. A method according to Claim 3, wherein a mathematical function is derived out of the calibration factors obtained in steps (cl), characterizing the flow rate performances of the infusion pump.

5. A system according to Claim 1, wherein the calibration device 50 comprises also a precise pressure measurement unit 96 for measuring pressure between the inlet and the outlet ports 52;53; a second signal data port connectable to the pump 40 for transmission of a pressure control signal from the device 50 to the pump 40; a processor unit 78 for issuing a nominal pressure control signal to the pump 40 through the second signal data port 58 to

" induce the pump to deliver liquid through the tube at a nominal pressure corresponding to said pressure control signal and for comparing the nominal pressure with the actual pressure measured by the pressure measurement unit and issuing a pressure calibration factor for correcting the pump pressure set up in order to obtain the nominal pressure.

6. A method for calibrating an infusion pump 40 to deliver liquid through a liquid infusion set at an actual pressure corresponding to a nominal pressure rate, the liquid infusion set 22 having tubing for pump-control delivery of liquid from an inlet 30 and to an outlet 34 end of the tubing, the method comprising: .

(a) inducing the pump to deliver liquid through the set at a first pressure rate; 11

(b) passing the delivered liquid through a pressure calibrating device and measuring the first actual liquid pressure therethrough;

(c) comparing the nominal pressure rate with the actual pressure rate to obtain a pressure calibration factor; and

(d) inputting data, based on the first pressure calibration factor, to correct the pressure rate of the pump such that when set to a first nominal pressure rate, the actual pressure rate will correspond thereto.

7. A calibration device according to Claim 1, for use in the system of Claim 1, or in the method of any one of Claims 2 to 4.