Vol.2, No.6, 431-434 (2009)
doi:10.4236/jbise.2009.26062
SciRes Copyright © 2009 Openly accessible at http://www.scirp.org/journal/JBISE/
JBiSE
Design of occlusion pressure testing system for
infusion pump
Peng Zhang1, Shu-Yi Wang1, Chuan-Yi Yu1, Min-Yan Zhang1
1School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, China.
Received 23 June 2008; revised 16 July 2009; accepted 28 July 2009.
ABSTRACT
Reliability of medical devices such as infusion
pumps is extremely important because these
devices are being used in patients who are in
critical condition. Occlusion pressure, as an
important parameter of infusion pumps, should
be detected when an occlusion occurred. How-
ever, infusion pumps’ occlusion pressure could
not be tested and the performance of these
pumps is not known to us. In order to test the
occlusion pressure of infusion pump, a testing
system has been put forward according to
standards of IEC 60601-2-24:1998/ GB 9706.27-
2005. The system is comprised of sensor, ac-
quisition card, three-way tap and so on; this
system is controlled by a PC. At the same time,
sampling rate could be changed if necessary
and test time could be recorded. And then the
characteristics of this system were studied,
such as linear, effects of pump rates and dif-
ferent pumps. The system remained linear in a
given environment. The higher is the pump rate,
the faster is the time to reach occlusion condi-
tion. The testing system has been proved to be
effective in testing the occlusion pressure of
infusion pumps and the accuracy error of
pressure is content the demand of ±1% of
range.
Keywords: Infusion Pump; Occlusion Pressure;
Testing System
1. INTRODUCTION
Infusion pumps have been widely used in clinical prac-
tice, such as in intravenous infusion therapy to infuse
fluids, medication or nutrients into patient’s circulatory
system and can produce quite high but controlled pres-
sure so as to inject controlled amount of fluids, however,
pressure values are different regarding to different pumps.
Nowadays, most infusion pumps have an occlusion
pressure preset threshold, once the pressure of tubing,
connecting to patients, exceeds the preset limit, the
alarm of occurring occlusion will be active. Some infu-
sion pumps adopt a method of speed administration, in
this case, if fluid rate is zero during a certain time and
the alarm of occlusion will be active. However, on the
one hand, the pressure values of vascular are different
regarding to different persons and the same person at
different time. When an occlusion occurs along the de-
livery path, medication will not be delivered to patient
but the pressure does not reach the preset pressure and
the alarm will not be active. In this case, the pump can
not only continue to operate normally, but it can display
erroneous values about the infusion rate and accumu-
lated volume. This incorrect record for the patient could
lead to an improper analysis, which will cause injury to
patient. The higher is occlusion pressure, the more seri-
ous is the injury, so the test of occlusion pressu re is cru-
cial to pumps [1]. On the other hand, the inaccurate in-
fusion rates of infusion pumps could be generated if the
pumps are not checked up after a long time usage. At last,
some infusion pumps could be used to detect tissue ex-
tra vag at io n [ 2]. A t th is mo me nt , infu s ion pu mps mus t b e
periodically tested to determine whether they are func-
tioning pr o perly [3,4].
A testing system of infusion pump occlusion pressure
is designed to test an infusion pump and determine
whether the pump is operating correctly.
At present, there are several products commercial
availably in market; mostly they are designed by for-
eigners, such as IDA-4 Plus Infusion Pump Analyzer,
Infutest Solo Infusion Pump Analyzer and so on. The
former is designed by Fluke, it has a function of PCA
(Patient Controlled Analgesia) Pumps Bolus measure-
ment and testing four pumps at the same time; the latter
is designed by Datrend Systems Inc. and there are other
corporations to design infusion pump analyzers (tester)
[5,6]. Though these devices have well performances, th e
price is high accordingly. At the same time, some of
these devices are not designed rationally; one device is

P. Zhang et al. / J. Biomedical Science and Engineering 2 (2009) 431-434
SciRes Copyright © 2009 Openly accessible at http://www.scirp.org/journal/JBISE/
432
ruined for its first using, so we designed this simple but
good performance testing system. But the most impor-
tant point is that these devices are not designed followed
the IEC 60601-2-24:199 8 stan dard, so th ey can be not be
used to test other infusion pumps and so on.
During our previous work, we have found that, if fluid
speed is low in syringe pumps, in the curve of time-
pressure, there exists and smooth phase liking a part of
round and pressure values should be the in this phase.
On this condition, we adopted a different method and got
an elementary result, but this method was not satisfac-
tory and would be ameliorated.
2. METHODS AND APPARATUS
2.1. Description of Apparatus
According to th e standards of IEC 60601-2-24:1998 and
GB 9706.27-2005 , a test system is designed which is sh-
own in Fi gure 1. This system is applied to infusion pum-
ps, volumetric infusion pumps and syringe pumps [7,8].
The testing system can be divided into three parts ac-
cording to their different functions.
Part 1: In this part, the aim is designed to provide in-
fusion pumps to be tested; and infusion pumps provide
the driving force for occlusion pressure. The administra-
tion set, which is medical tubing in this system, sets to 1
m.
Part 2: The aim is designed to simulate the occlusion
in patient and collect the fluids. Occlusion is realized
through the turning of three-way tap and then the signal
of sensor is transmitted to the acquisition card. At the
beginning of test, when the three-way tap is opened,
fluids will be collected in the collecting vessel; if
three-way tap is closed, occlusion pressure will be gen-
erated following the rigid tubing and then the pressure
signal is transmitted to the pressure transducer. At the
end of test, fluids will be collected in the collecting vessel.
Part 3: In this part, the interface between PC, running
under Windows XP and sensor was realized through an
RS-232 connection. The sampling rate is controlled by
PC and software, which is basing on Visual C++ 6.0
platform. The signal, coming from sensor, is obtained by
acquisition card, and then is transmitted to computer.
After the further dealing and calculation of signals, the
dealt signals could be displayed on monitor in the form
of wave.
2.2. Measurements
The test is carried out using a test solution of ISO class
Ⅲ water for medical use, under normal condition
(20℃±2℃, 65%±5%RH (Relative humidity)). There are
several steps to implement this apparatus [7,8]:
First: Connect all the joints and check the testing sys-
tem. The rigid tubing between three-way tap and sensor
should fill with water in advance. If the occlusion alarm
threshold can be selected, set it to minimum. Then, set
the appropriate pump rate and volume, then start it.
Second: Open the three-way tap (stopcock) and let
fluids flows into the collecting vessel. Close the three-
way tap (stopcock) when the internal liquid flow be-
comes steady and test the occlusion pressure alarm
threshold, this threshold will be registered by computer,
then collect fluids, which generated by the expand of
medical tubing.
Third: If the occlusion alarm threshold can be selected,
repeat the test with the occlusion pressure set to maxi-
mum.
Pressure sensor is an important part in testing system,
and the accuracy and precision of sensor are influenced
by actual environment, such as temperature, relatively
humidity. So to ensure the accuracy of the testing result,
pressure calibration of the testing system is necessary
before testing infu sion pumps.
Figure 1. Structure of infusion pumps testing system.

P. Zhang et al. / J. Biomedical Science and Engineering 2 (2009) 431-434
SciRes Copyright © 2009 Openly accessible at http://www.scirp.org/journal/JBISE/
433
Table 1. Relation between calibrator value and computer display value.
Calibrator
display(KPa) 10.10 19.99 29.96 40.01 50.01 60.02 70.01 79.99 89.98 99.98
Computer
display(V) 2.7309 2.9733 3.2176 3.4636 3.7087 3.9555 4.2012 4.4464 4.6906 4.9373
Results of
expression(KPa) 10.13 19.99 29.92 39.96 49.95 60.01 70.01 80 89.96 99.99
error 0.03 0 0.04 0.05 0.06 0.01 0 0.01 0.02 0.01
Regarding to the Infusion Pump Analyzers mentioned
before, the occlusion pressures are recorded once the
pressure level is highest, at the same time the elapsed
time is recorded [5,6]. In this testing system, the occlu-
sion pressure and elapsed time are recorded, meanwhile,
the delayed time, between the pressure reaches to the
alarm threshold of infusion pump and the pump is not
active, is recorded. The delayed time is also an important
parameter though it is zero in some pumps. The real-
time pressure wave could be displayed in monitor and
could be reviewed and analyzed.
3. RESULTS
In this testing system, pressure calibrator of Fluke-718
30G was used, it can be used to calibrate pressure sensor
and this testing system, its accuracy is ±0.05% of range
and resolution is 0.01KPa [9].The performance of pres-
sure sensor, under the same environment is summarized
in Ta b le 1. The unit of calibrator is KPa and computer
display is V (voltage), computer display is the value of
pressure signal, which has been magnified and filtered.
From the data results above, we can see that if the
value of calibrator increases about 10KPa, the value of
computer display increases about 0.24V correspond-
ingly, so the perfor mance of pressur e sensor shows well
linear.
Based on the relationship between calibrator value
and computer display value, a line could be drawn. The
relation between the display of computer and pressure
calibrator is almost linear. The expressions were calcu-
lated with least squares approximation and they are:
and ,
respectively. The sign x is computer display which is
obtained form acquisition card and th e sign y is the value
of calibrator. Since the model is almost linear, the pri-
mary output is proportional to the input signal, so the
first expression is enough in this system. In our testing
system, the range of pressure is 0-200KPa and the accu-
racy of testing system is ±1%, so the error is allowed
basing on the linear exp ression.
11.101732.40  xy 66.101033.410392.0 2 xxy
Three different infusion pumps (ANGEL-AJ5800,
YDBS-11A, and ATOM-P300) were tested under the
infusion rate of 250ml/h and sa mpling rate was 1Hz. Th e
performance of infusion pumps is shown in Figure 2.
4. DISCUSSION AND CONCLUSIONS
The lines in Figure 2 are test results of the pumps and
these tests were implemented under normal environment.
From these results, firstly, a peak pressure (occlusion
pressure) can be found, peak pressure of ATOM-P300
infusion pump, ANGEL-AJ5800 infusion pump and
YBDS-11A infusion pump was 114.80KPa, 215.80KPa,
and 165.1KPa respectively. Secondly, occlusion time
(the time from occlusion to occlusion alarm) was 12s,
38s and 12s, respectiv ely.
The different occlusion pressures between infusions
pumps could be seen from the test results. ATOM-P300
infusion pump has a pressu re sensor and the precision is
high; ANGEL-AJ5800 infusion pump has a higher oc-
clusion pressure value. Pressure of YBDS-11A is neither
high nor low. In order to ensure the safety of patients,
low occlusion pressure and occlusion time are necessary
and pressure sensor is the better choice in fusion pumps.
The occlusion pressure of usual infusion pumps is about
100KPa, and some new made infusion pumps is about
7PSI (48.265KPa) or even more lower. Occlusion pres-
sure alarm of ATOM-P300 infusion pump is lower than
YBDS-11A infusion pump and ANGEL-AJ5800，
ATOM-P300 infusion pump can prevent patient from
hurting much sooner than the latter if an occlusion hap-
pens.
The sensor is influenced by environment, especially
by temperature. In order to ensure the accuracy of the
Figure 2. Relation between time and pressure of different
pumps.

P. Zhang et al. / J. Biomedical Science and Engineering 2 (2009) 431-434
SciRes Copyright © 2009 Openly accessible at http://www.scirp.org/journal/JBISE/
434
Figure 3. Structure of infusion pump.
test, calibration process should be implemented before
performance, even in stable environment, calibration
should be oper a t ed pe ri o di cal l y.
Most infusion pumps are peristaltic, so the pressure is
not stable. After a higher (lower) value, there is a lower
(higher) value, as shown in Figure 2. That is determined
by the structure of infusion pump, shown in Figure 3, so
it is natural for the unstable pressure value.
We have mentioned that pressure curve of syringe
pump is different to infusion pump; it is also determined
by their structure.
In this study the infusion pump testing system is de-
signed and its focus is detection of occlusion pressure.
The results of infusion pump automatic detection system
have verified that this method is efficient in different
type of infusion pumps. The future research is concerned
with these following topics.
1) Software should be perfect. The essential function
could be achieved in present software, but many acces-
sional functions should be achieved in the future. The
friendly interface is necessary and the manual operation
should be decrease to ensure the accuracy of the testing
system.
2) Although the occlusion pressures of infusion pumps
were recorded, the delayed time should be recorded by
testing system automatically, through analyzing the ob-
tained data results.
3) The system is influenced by environment, such as
temperature，relative humidity, so more tests should be
implemented to come to a much better relation between
system and environment, which can be a reference for
further tests.
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