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1

A new hybrid (hydro-numerical) model of the circulatory system

Darowski M., Kozarski M., Ferrari G., Zieliński K., Górczyńska K., Szczepanowski A., Pałko K. J., Fresiello L., Di Molfetta A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2013

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Vol. 61, nr 4

993--1003

EN

The paper presents a hybrid (hydro-numerical) circulatory model built to be used as a complementary tool for clinical purposes. It was developed at the Institute of Biocybernetics and Biomedical Engineering - Polish Academy of Sciences (Poland) in co-operation with the Institute of Clinical Physiology - National Council of Research (Italy). Main advantages of the model are: 1) high accuracy and repeatability of parameters setting, characteristic of numerical solutions, 2) maximum flexibility achieved by implementing the largest possible number of the model’s elements in the numerical way, 3) ability to test mechanical heart assist devices provided by special computer applications; in the model two physically different signal environments - numerical and hydraulic - are connected by special impedance transformers interfacing physical and numerical parts of the model; 4) eliminating flowmeters, as the voltage controlled flow sources embedded in the system provide information on flows. In vitro tests were performed to evaluate the circulatory model: a) modelling and simulation of physiological and pathological states parameters vs. left ventricular end-systolic elastance (Emax l) and rest volume (Vol) variations, b) testing the effect of LVAD counterpulsation on circulatory hemodynamics and ventricular energetics; it resulted in the increase of total cardiac output (COLV tot) from pathological value 3.8 to 5.4 l·min−1, mean aortic pressure mPas from 67.8 to 96.1 mmHg and in the decrease of left atrial pressure mPla from 15.7 to 7.7 mmHg and External Work nEW by 37.5%. The model was verified based on literature data.

2

A hybrid (hydro-numerical) cardiovascular model: application to investigate continuous-flow pump assistance effect

Kozarski M., Ferrari G., Zieliński K., Górczyńska K., Pałko K. J., Fresiello L., Di Molfetta A., Darowski M.

Biocybernetics and Biomedical Engineering

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2012

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Vol. 32, no. 4

77-91

EN

A hybrid (Hydro-numerical) model of blood circulation developed at the Institute of Biocybernetics and Biomedical Engineering (IBIB) of the Polish Academy of Sciences (PAN) -Warsaw, Poland, in co-operation with the Institute of Clinical Physiology (IFC) of the National Council of Research (CNR) - Rome, Italy, is a basic model of this type solutions commonly accepted by the researchers. It is able to simulate all essential hemodynamic functions of the human cardiovascular system including the heart. During last years, resumption of works on constant-flow non pulsatile rotary pumps to be used as heart support devices is observed because of their small dimensions and easier way of implantation. Control modes of rotary pumps are different and evidently influence heart support effects. The main aim of this paper was to investigate different control systems of rotary pumps in a role of the assist devices. To fulfill this task on the hybrid model, a special computer application was worked out. The investigations included: a) loading characteristics p(q) of the rotary pump assignment at two values of a control voltage - 18V, 24V; b) physiological and pathological states simulation including parallel atrial-aortic assistance by the rotary pump. The results of the simulations obtained on the model treated as a 'virtual patient' are in agreement with the data received in medical conditions.

3

Influence of ventilation mode on blood oxygenation - investigation with Polish Virtual Lungs and Italian Model of Circulation

Gólczewski T., Zieliński K., Ferrari G., Pałko K. J., Darowski M.

Biocybernetics and Biomedical Engineering

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2010

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Vol. 30, no. 1

17-30

EN

Positive alveolar (PA) and thoracic (Pr) pressures during artificial ventilation disturb pulmonary circulation, and might influence arterial blood oxygenation (PaO2). Initial analysis of such influence of different artificial ventilation modes is the goal of this paper. Previously elaborated virtual respiratory system (IBIB PAS, Warsaw, Poland) and cardiovascular system model (ICP CNR, Rome, Italy) were connected with two files-buffers to work as one virtual cardio-pulmonary system. Dependence of PaO2 on two methods (continuous inspiratory airflow (VCV) or pressure (PCV)), two ventilatory frequencies (fV = 15 or 7.5/min), and two values of the minute ventilation (Vmin = 6 or 8L/min) was investigated. Perfusion dependence on gravity was neglected as the virtual patient was in the supine position. Simulations showed that when fV = 15/min, neither the used method nor Vmin influence pulmonary blood flow significantly, whereas they influence the flow during expiration when fV = 7.5 (blood flow falls more for PCV and Vmin = 8 L/min). Vmin more significantly influences alveolar partial pressure of oxygen (P02) when fV = l5/min. P02 was greater for PCV. As effects on the flow and PO2 were contradictory, Pa02 was almost independent of the used method and fV. It depended on Vmin more significantly if fV = 15/min.

4

Biventricular pacemaker synchronization: A numerical cardiocirculatory model application to reproduce in vivo data

Di Molfetta A., De Lazzari C., Ferrari G., Moscariello F., Aguzzi G., Fresiello L., Darowski M., Trivella M. G., Alessandri N

Biocybernetics and Biomedical Engineering

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2010

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Vol. 30, no. 1

3-15

EN

Cardiac Resynchronization Therapy (CRT) seems to be the most encouraging treatment to limit the damages of ventricular remodelling in patients with moderate-severe cardiac insufficiency. Mathematical modelling of the cardiovascular system is a tool potentially useful to understand how the Biventricular Pacemaker (BPM) must be synchronised during CRT. In this work a computer simulator reproduces clinical data measured, on different patients affected by asynchronous ventricular contraction, before and after CRT. Three patients, affected by asynchronous ventricular contraction, were monitored before and after biventricular stimulation through CRT. Measured and simulated data were compared. Results show that the software simulator can well reproduce in vivo data. Besides, simulated results from BPM together with drug therapy are in accordance with literature data. Numerical modelling could be a useful tool to optimize the BPM synchronization.

5

Role and applications of circulatory models in cardiovascular pathophysiology

Ferrari G., Kozarski M., De Lazzari C., Górczyńska K., Pałko K. J., Zieliński K., Di Molfetta A., Darowski M.

Biocybernetics and Biomedical Engineering

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2009

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Vol. 29, no. 4

3-24

EN

Circulatory models are relevant for research, education and testing of prosthetic devices/components. Independently of its structure that can be numerical, physical or hybrid the models can be used in different areas of cardiovascular pathophysiology. However, the models are often used to reproduce specific circulatory conditions instead of being used as 'systemic' tools. That is to say, the models are used to evaluate the global effects of external disturbances such as pathologies, therapies, special environments or surgery on the circulatory system. Aim of this paper is to illustrate a family of circulatory models developed to represent the whole circulatory system in pathophysiological conditions describing some of the possible applications.

6

Open loop hybrid circulatory model: the effect of the arterial lumped parameter loading structure on selected ventricular and circulatory variables

Kozarski M., Ferrari G., Zieliński K., Górczyńska K., Pałko K. J., Tokarz A., Darowski M.

Biocybernetics and Biomedical Engineering

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2008

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Vol. 28, no. 1

17-27

EN

Different combinations of the artero-ventricular coupling design (numerical, physical and hybrid) and the arterial system structure (four-element standard, simplified, modified and three-element three-lump "ladder" Windkessel) have been applied in an open loop circulatory model to test their influence on selected ventricular and circulatory variables. Numerical investigations have shown that a four-element Windkessel with an introduced in series lumped inertance can evoke some numerical problems e.g. when combined with the simplified ventricular model containing "ideal" zero switching time heart valves or constant valve resistance during opening. The four-element Windkessel structure modification i.e. replacing the in series inertance by the parallel one, considerably improves the network match. Also the three-element three-lump "ladder" Windkessel has been found very useful in the blood circulation modelling thanks to relatively small input inertance and high input capacitance of its first lump.

7

Hybrid modeling of biomedical systems and measuring nonlinear characteristics of biosignals for improving quality of life

Darowski M., Klonowski W., Kozarski M., Ferrari G., Zieliński K., Stępień R.

Metrology and Measurement Systems

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2007

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Vol. 14, nr 1

89-100

EN

The main purpose of this paper is to present some metrological aspects of the new concept of hybrid modeling (combined physical and in silico) of biological systems as well as possible applications of nonlinear (symbolic) biosignal analysis for improving quality of life through modeling and knowledge-based measurements in medicine.

8

A family of circulatory computer models developed to analyse and predict physiopathological events: applications to mechanical circulatory and ventilatory assistance

De Lazzari C., Darowski M., Ferrari G., Tosti G.

Biocybernetics and Biomedical Engineering

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2006

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Vol. 26, no. 2

25-37

EN

The aim of this work is to present a family of circulatory computer models suitable to be used for analysis and prediction. Circulatory models can reproduce many circulatory phenomena for several practical applications referable to the main functional sectors of analysis and prediction. Of course, the models are different in relation to the phenomena to be represented. An important issue is the possibility to represent the artero-ventricular interactions and the effects, in different ventricular conditions, of the influence of mechanical ventilatory and circulatory assistance. In these models of human cardiovascular system, the influence of mechanical ventilation was introduced, changing the thoracic pressure to positive values. In the work, two different applications were presented: in the first one the trends of the haemodynamic variables were analysed when mechanical ventilation of the lungs was applied for different values of mean intrathoracic pressure. In the second application, were presented the effects on the haemodynamic variables of the left ventricular assist device (in particular arotary blood pump).

9

Development of hybrid (numerical-physical) models of the cardiovascular system: numerical-electrical and numerical hydraulic applications

Ferrari G., Kozarski M., De Lazzari C., Górczyńska K., Darowski M., Tosti G.

Biocybernetics and Biomedical Engineering

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2005

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Vol. 25, no. 4

3-15

EN

Circulatory models are relevant to research, education and prosthetic devices/components testing. Their structure can be both numerical and physical, according to the specific needs. Numerical models are often developed first and then followed or accompanied by physical models. This approach is associated with higher costs, less accuracy and time-consuming development. Circulatory models defined as hybrid (merger of numerical and physical sections) can solve these problems. This paper presents two applications of the hybrid model with the physical section based on two different structures (electrical and hydraulic). The results show that the model can represent hemodynamic relationships in different circulatory conditions, including IABP assistance.

10

Virtual instruments (VIs) in the study of cardiovascular and respiratory systems research

Clemente F., Ferrari G., De Lazzari C., Mimmo R., Guaragno M., Tosti G.

Biocybernetics and Biomedical Engineering

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2003

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Vol. 23, no. 2

17-26

EN

The aim of this paper is to discuss problems (and solutions!) related to the design and the realisation of a system devoted to on line signal processing in different fields of engineering and applicable in cardiovascular and respiratory systems research and their interaction. A description of our approach is reported with some consideration of the hardware and software lay out. Different applications using our system have been described. These applications involve the use of a PC based system in clinical environment and in our laboratory on a mock circulatory system.

11

The influence of ventilatory support on coronary flow and oxygen consumption in different circulatory conditions

De Lazzari C., Darowski M., Ferrari G., Mimmo R., Guaragno M., Tosti G.

Biocybernetics and Biomedical Engineering

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2003

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Vol. 23, no. 1

103-110

EN

The aim of this work is to predict the influence of mechanical ventilation on cardiac output, coronary flow and left ventricular myocardial oxygen consumption in different circulatory conditions. To study this interaction we used a computer simulator of human cardiovascular system in which lumped parameters models were used to reproduce the circulatory phenomena in terms of pressure and volume relationships. Variable elastance models reproduce the Starling's law of the heart, for each ventricle. In the study the left ventricular elastance assumed two different values. Symetric arterial resistance was changed during the simulation. The influenece of mechanical ventilation was introduced by positive mean thoracic pressure. Positive thoracic pressure, changes of peripheral resistance and different ventricular elastance values have a significant influence on cardiac output, coronary flow and myocardial oxygen consumption.

12

The electrohydraulic impedance converter in mock circulatory system design

Kozarski M., Ferrari G., Darowski M., Górczyńska K., Clemente F., Pałko K. J.

Biocybernetics and Biomedical Engineering

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2003

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Vol. 23, no. 2

27-34

EN

In the paper a new concept of a mock circulatory circuit design, utilizing the special impedance converter, i.e. the electrohydraulic gyrator, has been presented as well as basic theoretical considerations and simple examples of impedance conversions. Some results of experiments, illustrating physical and systemic features of the electrohydraulic gyrator, have been shown. A simple hybrid windkessel model has been investigated. Obtained results fully confirmed advantages of the presented new concept of a mock circulatory circuit design.

13

Physical modelling of the cardiovascular system : development of a new simulation system based on hybrid (numerical-hydraulic) components

Ferrari G., De Lazzari C., Kozarski M., Clemente F., Górczyńska K., Mimmo R., Tosti G., Guaragno M.

Biocybernetics and Biomedical Engineering

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2003

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Vol. 23, no. 2

3-15

EN

Research, education, testing of assist devices and training are among the applications of physical models of the circulation. Unfortunately, they are rather expensive and the scope of their use is structure-dependent as it is not easy to modify them. As numerical models do not have these limitations, our aim is to develop a physical model of the circulation limited to the sections of interest merging them with numerical models representing the remaining parts of the circulatory system. The system under development is therefore a hybrid where physical and numerical sections, merged together, represent the circulatory system. The sections developed till now represent one of the ventricles and part of the arterial tree. This paper is devoted to the description of the hybrid ventricular model and its first applications.

14

The influence of selected left ventricular and systemic parameters on cardiovascular hemodynamics and energetics - modeIIing study

Górczyńska K., Ferrari G., De Lazzari C., Mimmo R., Tosti G., Clemente F., Englisz M., Guaragno M.

Biocybernetics and Biomedical Engineering

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2000

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Vol. 20, no. 3

35-47

EN

Ventricular sufficiency can be estimated basing on the heart muscle's ability to effective ejection in systole and filling conditions created in diastole. These features, in quantitative sense, can be evaluated by selected energetic and hemodynamic parameters of the ventricle and the circulatory system. In the computer model and the physical model of blood circulation, pathological states of the left ventricle and the systemic arterial tree, represented by ventricular compliance, the filling characteristic and peripheral resistance have been simulated. The influence of the modelled pathological states on hemodynamics and energetics of the circulatory system has been discussed. In some cases, left ventricular assistance using an LVAD has been appIied. The computer model CARDIOSIM and the physical model MCS, with computer-controIled ventricles and peripheral resistances, were developed at the Institute of Biomedical Technologies CNR in Rome (Italy). In these models, the energetic relations among the ventricle, the arterial system and the assist device are analysed on the pressure-volume piane (P-V). The LVAD was developed at the Institute of Biocybernetics and Biomedical Engineering PAS. It consists of the foIlowing units: the artificial left ventricle ALV, the pneumatic drive unit PDU and the electronic control system ECS. In the device, the driving positive and negative pressure signals for the systole and diastole phases are realised by means of one pneumatic element in the PDU of special original design. The foIlowing parameters were used to estimate condition of the circuIatory system in different pathological states, including left ventricular assistance: left atrial pressure P(LA) aortic pressure P(as), arterial pulmonary pressure P(ap) cardiac output CO, cardiac output index CI, external work EW, oxygen consumption V(O2) and cardiac mechanicaI efficiency CME.

PL

Sprawność komory serca może być oceniana na podstawie zdolności mięśnia sercowego do efektywnego wyrzutu krwi z komory w fazie skurczu i warunków napełniania komory krwią w fazie rozkurczu. W sensie ilościowym, cechy te mogą być oceniane na podstawie wybranych parametrów energetycznych i hemodynamicznych serca i układu krążenia. Na fizycznym i komputerowym modelu układu krążenia zamodelowano stany patologiczne lewej komory i systemowego układu tętniczego, reprezentowane przez podatność komory, charakterystykę jej napełniania i oporność peryferyjną. Dokonano analizy wpływu zamodelowanych stanów patologicznych na hemodynamiczne i energetyczne parametry układu krążenia i lewej komory, również w przypadku jej wspomagania za pomocą urządzenia LVAD. Komputerowy model układu krążenia CARDIOSIM i fizyczny model MCS ze sterowanymi komputerowo komorami serca i opornościami peryferyjnymi, zostały opracowane i wykonane w Instytucie Technologii Biomedycznej CNR w Rzymie. W modelach tych energetyczne zależności pomiędzy sercem, układem krążenia i urządzeniem wspomagającym analizowane są na płaszczyźnie P-V (ciśnienie-objętość). Urządzenie LVAD, służące do wspomagania pracy serca za pomocą sztucznej lewej komory, zostało opracowane i wykonane w Instytucie Biocybernetyki i Inżynierii Biomedycznej PAN w Warszawie. W skład urządzenia wchodzą: sztuczna lewa komora ALV, pneumatyczny układ napędowy PDU i elektroniczna jednostka sterująca EIS. W urządzeniu tym, dodatni i ujemny sygnał ciśnieniowy dla fazy skurczu i fazy rozkurczu jest realizowany w PDU, za pomocą tego samego elementu pneumatycznego o specjalnej, oryginalnej konstrukcji. W niniejszej pracy, do ogólnej oceny kondycji układu krążenia w różnych stanach patologicznych, z uwzględniem wspomagania lewej komory serca, użyto następujących parametrów: ciśnienie w lewym przedsionku P(LA) ciśnienie aortalne P(as) ciśnienie w tętnicy płucnej P(ap) wskaźnik serca CI, praca zewnętrzna EW, zużycie tlenu V(O) i mechaniczna wydajność serca CME.

15

A PC based model to simulate artero-ventricular interaction and the effect of mechanical circulatory and ventilatory support

De Lazzari C., Darowski M., Clemente F., Guaragno M., Ferrari G.

Biocybernetics and Biomedical Engineering

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1999

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Vol. 19, no. 4

79-89

EN

A software package for the simulation of the cardiovascular system and of artero-ventricular interaction has been developed. It includes the reproduction of the effects of mechanical circulatory like Left Ventricular Assist Device (LVAD), Biventricular Assist Device (BVAD), Intra-aortic Balloon Pump (IABP) and ventilatory support systems. Lumped parameters models were used to reproduce the circulatory phenomena in terms of pressure and volume relationships. Variable elastance models reproduce the Starling's law of the heart, for each ventricle. LVAD and BVAD are inserted with atrial-arterial cannulation and can be synchronised with the onset of the natural ventricle systole. IABP model, inserted in the arterial tree, is considered as a flow source. Controlling the level of thoracic pressure (Pt) performs the simulation of mechanical ventilation. The examples of simulations are presented in the paper as the effects of LVAD and mechanical ventilatory support on circulatory system, in terms of hemodynamic parameters changes.

PL

W artykule przedstawiono model komputerowy CARDIOSIM@ i oprogramowanie do symulacji zależności hemodynamicznych w układzie sercowo-naczyniowym na komputerze zgodnym z PC. Oprogramowanie to umożliwia także symulację wpływu różnych metod mechanicznego wspomagania krążenia, np. sztucznej lewej komory serca (LVA]), wspomagania dwukomorowego (BVAD), lub pompy wewnątrzaortalnej (lABP) i oddychania na parametry hemodynamiczne i energetyczne. Modele LV AD, BVAD i IABP są zsynchronizowane z pracą naturalnej lewej komory serca (z początkiem fazy systolu). LVAD i BVAD są umieszczone równolegle z komorami serca, a IABP jest traktowane jako źródło przepływowe w tętniczej części modelu. Regulacja poziomu średniego, dodatniego ciśnienia w klatce piersiowej w modelu oddaje wpływ sztucznej wentylacji płuc na układ sercowo-naczyniowy. Model komputerowy opisujący zależności ciśnieniowo-przepływowe w poszczególnych częściach układu sercowo-naczyniowego jest modelem liniowym o staIych skupionych. Do opisu własności każdej z komór serca wg prawa Starlinga wykorzystano model zmiennej elastancji. W pracy przedstawiono przykłady symulacji komputerowej, jako cenną możliwość przewidywania wpływu stosowania LVAD i wspomagania oddychania na hemodynamikę.

16

Evaluation of influence of LVAD assistance on haemodynamics and ventricular energetics in closed-loop mock circulatory system

Ferrari G., Górczyńska K., Lazzari C., Engliasz M., Tosti G., Ambrosi D., Mimmo R., Fabrizio C.

Biocybernetics and Biomedical Engineering

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1998

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Vol. 18, no. 1-2

19-34

EN

The choice of control strategy of a Left Ventricle Assist Device in heart recovery is an open problem. It affects circulatory parameters, myocardial perfusion and energetic variabies, directly related to oxygen consumption in both ventricles. The experiments were performed by a computer controlled closed loop mock circulatory system, in known and constant pathological condition, connected to a pneumatic LVAD. The assistance was realized by changing artificial left ventricular systole duration and its relation to the QRS complex of ECG signal. The data were analysed as a function of haemodynamic parameters as well as energetic variabies (external work EW, oxygen consumption V0(2), cardiac mechanical efficiency CME). The results have shown: 1) assistance effect, besides driving pressure of the artificial ventricle, depends on its systole beginning and duration and on the value of peripheral resistance; 2) left heart assistance influences right ventricular parameters in limited way; it increases right atrial pressure and decreases arterial pulmonary pressure and oxygen consumption.

PL

Wybór strategii sterowania urządzenia wspomagającego LVAD dla poprawy kondycji niewydolnego serca jest problemem otwartym. Proces wspomagania oddziaływuje na parametry cyrkulacji, perfuzję mięśnia sercowego i parametry energetyczne związane bezpośrednio ze zużyciem tlenu przez obie komory serca. Opisane w niniejszej pracy eksperymenty przeprowadzono na sterowanym komputerowo fizycznym modelu układu krążenia, na którym zamodelowano stany patologiczne, poddane następnie wspomaganiu kontrpulsacyjnemu za pomocą urządzenia LVAD. W procesie wspomagania zmieniano czas trwania fazy skurczu sztucznej lewej komory urządzenia LVAD poprzez zmianę opóźnienia końca fazy skurczu tej komory względem zespołu QRS przebiegu EKG "sztucznego pacjenta". Opóźnienie początku fazy skurczu sztucznej komory pozostawało nie zmienione. Uzyskane wyniki analizowano na gruncie hemodynamicznym (ciśnienia, przepływy) i energetycznym (praca zewnętrzna EW, zużycie tlenu V0(2), współczynnik wydajności mechanicznej serca CME). Stwierdzono: 1) na efektywność wspomagania, oprócz ciśnienia sterującego pracą sztucznej komory, wpływa czas trwania jej fazy skurczu i czas opóźnienia względem zespołu QRS oraz wielkość oporności peryferyjnej; 2) wspomaganie lewej komory wywiera ograniczony wpływ na prawe serce, co się objawia niewielkim wzrostem ciśnienia w prawym przedsionku i pewnym spadkiem ciśnienia arterialnego płucnego oraz zużycia tlenu.

17

Energetic cardiovascular variabIes during positive pressure ventilation

Dąbrowski M., De Lazzari C., Ferrari G., Nicoletti A.

Biocybernetics and Biomedical Engineering

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1998

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Vol. 18, no. 3-4

19-29

EN

Thc application of mechanical ventilatory support can affect both haemodynamic and energetic cardiovascular variables. The aim of our computer simulation was to trace the influence of positive pressure ventilation on external work (EW) of the natural ventricle, cardiac mechanical efficiency (CME) and pressure volume area (PVA). Physiological and pathological conditions of the heart were reproduced. Systemic arterial resistance (Ras) was also changed to model physiological and pathological states. The influence of mechanical ventilation was introduced by changing levels of mean thoracic pressure. Our simulation showed that positive thoracic pressure changes all the energetic cardiovascular variables and shouId be taken into accoulnt during the assessment of mechanical ventilation. Pathological changes of left ventricular contractility and Ras have a considerable effect on EW, CME and PVA. On the other hand energetic parameters for the left ventricle are not especially effected by pulmonary vasoconstriction phenomenon.

PL

Stosowanie mechanicznego wspomagania oddychania może wpływać na parametry hemodynamiczne i energetyczne układu sercowo-naczyniowego. Celem niniejszej symulacji komputerowej było określenie wpływu dodatniego ciśnienia sztucznej wentylacji na pracę zewnętrzną (EW) naturalnej komory serca, współczynnik mechanicznej wydajności (CME) oraz całkowitą energię generowaną w jednym cyklu pracy serca (PVA). Zostały odtworzone stany patologiczne i fizjologiczne serca. Zmieniana była także systemowa oporność tętnicza (Ras), zgodnie ze stanami fizjologicznymi i patologicznymi. Wpływ mechanicznej wentylacji był symulowany przez zmiany średniego ciśnienia wewnątrz klatki piersiowej. Nasza symulacja wykazała, ze dodatnie ciśnienie wewnątrz klatki piersiowej zmienia wszystkie parametry energetyczne układu sercowo-naczyniowego, co powinno być brane pod uwagę podczas prowadzenia mechanicznej wentylacji. Patologiczne zmiany elastancjl lewej komory i Ras mają znaczny wpływ na EW, CME i PVA. Z drugiej strony energetyczne parametry lewej komory zmieniają się tylko nieznacznie przy symulacji automatycznych zmian oporu plucnego (pulmonary vasoconstriction).