Engineering, 2012, 5, 124-125
doi:10.4236/eng.2012.410B032 Published Online October 2012 (http://www.SciRP.org/journal/eng)
Heart and Lung Mechanical Assist Devices are
Comprehensively Tested by the New Hybrid Simulators
M. Darowski1, K. J. Pałko1, M. Kozarski1, K. Zieliński1, K. Górczyńska1, G. Ferrari2,
L. Fresiello2, A. Di Molfetta2
1Nałęcz Institute of Biocybernetics and Biomedical Engineering, PAS, Ks. T r o j de n a 4, 02-109, Warsaw, Poland
2Inst itut e of Clinical Physiolog y, Section of Rome, CNR, Via Sa n Martin o della Battaglia 44, 00185, Rome, Italy
Received 2012
ABSTRACT
Two applications of the hybrid simulators have been presented as examples: nonpulsatile VAD interaction with lumped parameters
cardio vascular syst em numeric al model an d resp irator inter acting with th e Dubois nu merical model of obstru ctive lung diseas es. Th e
results of simulations showed how the tested assist devices change biological system - assist device characteristics in the course of
heart or lungs diseases and how it influences pressure and flow in a particular point of cardiovascular or respir atory system numerical
model.
Keywords: Ventricular Assist Device; Respirator; Modelling; Hybrid Simulator
1. Introduction
Different type of heart and lung support systems and devices
like ventri cular assist devices (VAD) and r espirators have been
developed up to now but the problem how to test them, objec-
tivel y, compare their features - advan tages and disad vantages is
still to be solved [1-3].
The heart and lung assist devices are, generally speaking,
mechanical pu mps th at shou ld be tested befor e th eir clin ical use,
according to appropriate standards. In order to access the fea-
tures of these devices it is necessary to connect them to me-
chanical models of the biological organ or system (the human
circulatory or respiratory systems) that are to be assisted or
supported. Such mechanical models of the human circulatory or
respiratory systems are expensive, as they have to be complex
to simulate different pathologies of the biological (cardiovas-
cular or respiratory) systems.
Computer models of the human cardiovascular or respiratory
systems are much cheaper th an the mechanical on es but, on the
other hand, they can not be connected with mechanical assist
devices like blood pumps or respirators [4,5].
2. Materials and Methods
The solution we propose to test heart and lung assist devices is
to use a new type of simulators (patent pending) – so called
hybrid ones. They consist of a computer model of the human
cardiovascular or respiratory system and a specially designed
interface to connect this model with the mechanical assist de-
vice. These interfaces (electro-hydraulic for VAD or elec-
tro-pneumatic for respirators) play a role of impedance con-
verters, as t hey enable to convert a part of the numerical model
into a physical part o f the same impedan ce, to which the tested
assist d evi ce is connected ( Fig ure 1).
It was possible to realize this concept thanks to the applica-
tion of electrically connected flow and/or pressure sources as
basic components of the impedance converters (see Figures
2-3).
There are varieties of technical realization of the impedance
convert er. In a case of test ing the VAD we used a gear pu mp to
build the voltage controlled flow source being a crucial part of
the imped ance convert er (Figure 2) and in a case of testing t he
respirators, a voltage controlled piston flow source was used as
a basic co mponen t of the impedance conver ter (Figure 3).
Figure 1. The idea of testing mechanical assist devices on a hybrid
simulator of the cardiovascular or respiratory system.
Fig ur e 2 . Set-up of the hydro-numerical interface (VAD-lef t a tr i um)
for testing a nonpulsatile VAD on the hybrid simulator with a gear
pump as a voltage controlled flo w source.

M. DAROWSKI ET AL.
125
3. Results
Two applications of the mentioned above simulators have been
presented as examples: nonpulsatile VAD interaction with
lumped p arameters cardi ovascular syste m numerical model and
respirator interacting with the Dubois numerical model of ob-
structive lung diseases. The results of simulations showed how
the tested assist devices change biological systems characteris-
tics in the course of heart or lungs diseases and how it influ-
ences pressure and flow in a particular point of cardiovascular
or respirato ry system numerical model.
The results of simulations of the cardiovascular system in-
teracting with a nonpulsatile VAD were shown in Figure 4 as
P-V loops.
Modelling of physiological and pathological states of the
cardiovascular system was done and in the case of pathology
the VAD was applied as assist1 and assi st 2.
As we can see fro m Figure 4, VAD application changes P-V
loop location but not so dramatically as pathology of the car-
dio vascular system.
The results of simulations of the respiratory system interact-
ing with a respirator are shown in Figure 5 as time curves of
control (Pin) and pleural (Pt) pressures. The respirator is pro-
viding pressure control ventilation of the human lungs which is
a t ypical Du b oi s model with an ab stract ive lu ng d iseas e. As can
be seen fro m Figure 5, thi s disease causes posi tive end expira-
tory pressure to appear in the lungs.
Figure 3. Set-up for testing a respirator on the hybrid simulator
with a voltage controlled piston flow source.
0
20
40
60
80
100
120
140
160
050100 150 200
Vlv [cm
3
]
Plv [mmHg]
phy siology
pathology
path+assist1
path+assist2
Figure 4. The results of simulations of the cardiovascular system
interacting with a nonpulsatile VAD.
0
0,2
0,4
0,6
0,8
1
30 3540 45
time [s]
pressur e [kPa]
Pin
Pt
Figure 5. The results of simulations of the respiratory system inte-
racting with a resp irator .
4. Conclusion
Tests of the hybrid simulators performance and simulations of
their interaction with heart and lung assist devices proved that
they are reliable and accurate tools to test these devices and
help to optimize their applications in different cases of heart
and lungs pathology (as decision support systems).
5. Acknowledgements
The resear ch leadin g to these resul ts has received fu nding from
the European Community’s Seventh Framework Programme
(FP7/2007-2013) under grant agreement No. 248763 (Senso-
rART Project).
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