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1

Use of siliconised infant endotracheal tubes reduces work of breathing under turbulent flow

Stankiewicz B., Rawicz M., Darowski M., Zielinski K., Kozarski M., Chwojnowski A.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 1

59--65

EN

The high resistance of an infant endotracheal tube (ETT) can markedly impair ventilation and gas exchange. Since some manufacturers cover the inner surface of their ETTs with a silicon layer in order to diminish deposition and ease mucous evacuation from airway, via surface roughness decrease, we assessed whether the silicon layer may affect tube resistance, work of breathing and other parameters of ventilation. We compared SUMI (Poland) non-siliconised and siliconised polyvinyl chloride ETTs (2.5, 3.0 and 4.0 mm ID), twenty of each type and size combination. Simulating volume-controlled ventilation with the hybrid (numerical–physical) lung models of a premature infant and a 3-month-old baby peak inspiratory pressure (PIP), peak inspiratory and expiratory flow (PIF, PEF), (patient + ETT) inspiratory and expiratory airway resistance (Rins, Rexp) and work of breathing by ventilator (WOBvt) were measured. Additionally, images of the both type surfaces were taken using Hitachi TM-1000 electron microscope. When 2.5 and 3.0 mm ID ETTs were examined, laminar flow (Re <2300) across the tube was observed, and there were no clinically significant differences in the ventilation param-eters between non-siliconised and siliconised tubes. Whereas, when 4 mm ID ETTs were tested, turbulent flow was observed, and PIP, Rins, Rexp and WOBvt were significantly lower (5%, 17%, 17%, and 7%, respectively) (P < 0.05), but PIF and PEF were significantly higher (8%, 14%) (P < 0.05). Thus, the silicone inner surface of ETT offers less resistance and WOBvt in presence of turbulent flow. However, artifacts observed on the surface of non-siliconised and siliconised ETTs can potentially impair ventilation.

2

A hybrid (hydro-numerical) circulatory model: investigations of mechanical aortic valves and a numerical valve model

Kozarski M., Suwalski P., Zieliński K., Górczyńska K., Szafron B., Pałko K. J., Smoczyński R., Darowski M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2015

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Vol. 63, nr 3

605--612

EN

In most cases of diseased heart valves, they can be repaired or replaced with biological or mechanical prostheses. Biological prostheses seem to be safer than mechanical ones and are applied with good clinical outcomes. Their disadvantage, when compared with mechanical valves, is durability. In the development and application of mechanical and biological heart valves, a significant role can be played by a Hybrid (Hydro-Numerical) Circulatory Model. The aim of this paper is to demonstrate the opportunities created by the hybrid model for investigations of mechanical heart valves and their computer models under conditions similar to those of the circulatory system. A diode-resistor numerical valve model and three different design mechanical aortic valves were tested. To perform their investigations, computer applications were developed under RT LabView to be run on a PC. Static and dynamic characteristics of the valves were measured and registered - pressure in the numerical time-varying elastance left ventricle (pLV), in the aorta (pas) and flow (f), proving, among other factors, that 1) time delay of pas with respect to pLV is mainly related to the valve’s opening time, and 2) the valves of substantially different designs tested under identical hydrodynamic conditions reveal nearly the same dynamic performance.

3

EtCO2 -Based Biofeedback Method of Breath Regulation Increases Speech Fluency of Stuttering People

Stankiewicz B., Zieliński K., Darowski M., Michnikowski M.

Archives of Acoustics

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2015

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Vol. 40, No. 4

469–-474

EN

Respiratory disturbances frequently accompany stuttering. Their influence on lung ventilation can be assessed by measurement of the end-tidal CO2 concentration (EtCO2). The effectiveness of the CO2-based visual feedback method of breath regulation (VF) designed for stuttering therapy was tested in this study. The aim of the study was to answer the question if the VF helps to reduce respiratory disturbances in stuttering and increase speech fluency. 20 stuttering volunteers aged 13–45 years took part in the 3-parts test consisting of: 1. speaking without any techniques improving speech fluency, 2. learning the VF method, 3. VF-assisted speaking. The CO2/time signal and an acoustic signal of an utterance were recorded during the test. Significant increase of FE – the factor of breath ergonomics during speaking (based on both signals), from 47% to 71% (P < 0.01), and significant decrease of %SS – the percent of syllables stuttered, from 14% to 10% (P < 0.01) were received for VF-assisted utterances compared to the utterances without VF assistance. The results indicate that the VF can help to eliminate respiratory disturbances in stuttering and increase speech fluency.

4

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.

5

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.

6

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.

7

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.

8

A new control solution for independent synchronous ventilation of lungs

Darowski M., Michnikowski M., Nestorowicz A., Mikaszewska-Sokolewicz M., Glapiński J., Guć M., Stankiewicz B.

Biocybernetics and Biomedical Engineering

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2010

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Vol. 30, no. 2

29-39

EN

A new control solution for independent, synchronous ventilation of lungs has been developed and a controller to perform it with use of only one respirator and a bilumen intubation tube has been built. The controller enables division of the inspiratory tidal volume between the lungs in desired ratio, and setting of the positive end-expiratory pressure (PEEP) separately for each lung. The model tests have shown that the characteristics of the flow meters used, however not linear, is good enough to achieve clinically accepted accuracy of volume division. The tests have shown that the volume division is independent from the total tidal volume and PEEP. Maximal errors of the tidal volume division was less than 10%. The case study of patient after lung injury has shown significant improvement of the X-ray image and respiratory parameters (blood oxygenation, ventilatory pressures) during the independent ventilation of lungs with the use of the new device. The clinical study of 60 patients has shown that differences between actually realized volume division and the adjusted values are practically negligible.

9

The new hybrid pneumo-electrical piston model of lungs mechanics - preliminary tests

Kozarski M., Zieliński K., Pałko K. J., Stankiewicz B., Bożewicz D., Darowski M.

Biocybernetics and Biomedical Engineering

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2009

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Vol. 29, no. 3

3-18

EN

A design principle, construction and results of preliminary tests of a new hybrid physical-electrical model of lungs mechanics has been presented, The methods leading to development of lungs models of different complexity have been also included. The basic component of the model is a voltage controlled Bow source build up with a piston ~ cylinder system driven by a servomotor. This is used to develop a functional module playing a role of an impedance converter transforming an input electrical impedance Z0 of any electrical network connected to its electrical terminals into a pneumatic impedance Zin. Static and dynamic characteristics of the model connected to different pneumatic signal sources have been presented i.e. for the model connected with the respirator (expiration by the respiratory valve) and for the model with free unobstructed expiration. The very good dynamic features (time constant of the piston Bow source less than 1 ms) and a small resultant error of impedance conversion (less than 1%) enable the model to be applied in many application especially when new methods of lung ventilation are developed.

10

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.

11

A hybrid model of the respiratory system

Michnikowski M., Glapiński J., Guć M., Gólczewski T., Darowski M.

Biocybernetics and Biomedical Engineering

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2009

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Vol. 29, no. 1

71-80

EN

The aim of this work is building a hybrid model of the human respiratory system which enables connecting the real clinical devices (respirators) with the computerized virtual lungs. A simulation of the artificial ventilation of lungs, with the use of the hybrid model and the Siemens Servo 900 respirator, was made. Waveforms of pressure inside the lungs, flow in the respiratory tract, and the lung volume during the simulated artificial ventilation were recorded. The compliance and resistance of the hybrid model of the respiratory system were calculated on the basis of the inspiratory pause algorithms and compared to the values set in the model. The initial tests have shown that the calculated values of the parameters differ by 20% (worst result) from the values set in the model. The model will enable the investigation of the different modes of lung ventilation, as well as educational presentation of the respirator-patient interaction.

12

Urządzenie ECP-100 do nieinwazyjnego wspomagania układu krążenia wykorzystujące metodę kontrpulsacji zewnętrznej

Bachorz M., Godecki M., Darowski M., Kozarski M.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

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2009

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Vol. 15, nr 1

52-53

PL

Urządzenie ECP-100, opracowane przez ITAM Zabrze przy współpracy z 1B1B PAN Warszawa, umożliwia terapię pacjentów z chorobą niedokrwienną serca. Podczas zabiegu pacjent z zestawem mankietów pneumatycznych spoczywa na leżu zabiegowym. Zestaw składa się z trzech mankietów (podobnych do tych stosowanych przy pomiarze ciśnienia), które są owinięte dookoła łydek, ud i pośladków. Mankiety są napełniane sekwencyjnie na początku fazy rozkurczu serca i opróżniane przed fazą skurczu. Napełnianie i opróżnianie mankietów jest zsynchronizowane z przebiegiem EKG, tak by zoptymalizować korzyści terapeutyczne.

13

The virtual cardio-respiratory system: a sub-model of gas exchange and transfer

Gólczewski T., Darowski M.

Biocybernetics and Biomedical Engineering

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2008

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Vol. 28, no. 1

29-40

EN

A virtual cardio-respiratory system (CRS) is proposed for testing ventilatory support and scientific hypothesis. It may appear more convenient than experiments on animals or limited investigations on patients. In particular, there are no limitations for manipulation of virtual CRS parameters while such manipulation is difficult or impossible in the case of real CRS. The virtual CRS architecture: The proposed virtual CRS consists of: (a) the sub-model of respiratory system mechanics (RSM) previously used as the stand-alone virtual respiratory system, (b) a sub-model of gas exchange and transfer in the respiratory and circulatory systems (GET), which is constituted with three modules: gas transfer in respiratory system, gas exchange in lungs, and gas transfer in circulation. The GET utilizes airflows and pressures supplied by the RSM whereas the RSM utilizes volumes of gases supplied by the GET. Results: the CRS gave proper results for both respiration and respiratory arrest. In particular, if the CRS 'respired' with pure oxygen then arterial blood saturation with oxygen remained high for tens of minutes after respiratory halt when airways were open; otherwise atelectasis developed during 8-10 minutes. Like for real patients, carbon dioxide tension in blood decreased quickly when ventilation increased and it increased slowly when the ventilation fell.

14

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.

15

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.

16

Choice of proper lung ventilation method

Darowski M., Gólczewski T., Michnikowski M.

Biocybernetics and Biomedical Engineering

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2006

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Vol. 26, no. 1

21-37

EN

In the article three different methods of lung ventilation have been analyzed: Continuous Positive Airways Pressure (CPAP), Proportional Assist Ventilation (PAV) and Pressure Support Ventilation (PSV). The aim of these analyses was to predict clinical situations when the considered modes of ventilation would play their role in the best, optimal way. The study on effective ventilatory support by CPAP, PAV and PSY was conducted using virtual respiratory system - a new, but yet verified model of the system, recently developed by our group. Computer simulation, done on a healthy lung model and on a pathologically changed lung model, has clearly shown the conditions under which CPAP, PAV or PSY could be really effective. CPAP is worth using in patients with a high airways resistance, in which case this mode of ventilatory support ensures breathing with normal frequency and less energy-consuming inspiration. PAV usually results in a smaller peak and the mean alveolar pressure than PSY which decreases a potentially harmful effect of the positive pressure ventilation on the cardiovascular system. On the other hand, PAV may be used safely when estimation of the parameters such as the lung/thorax compliance and the airway resistance is reliable, since the setting of the supporting pressure is based on this estimation.

17

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).

18

Visual feedback based on expired CO2 as a therapy method for respiratory disturbances in stuttering

Stankiewicz B., Adamczyk B., Zieliński K., Darowski M.

Archives of Acoustics

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2006

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Vol. 31, No. 4

439-444

EN

A new CO2-based visual feedback therapy method (VF) for respiratory disturbances in stuttering was preliminarily assessed. Sound and expired CO2 signals were registered in 12 stutterers and 12 fluent speakers while speaking without and with VF to control breathing as well as during rest respiration, before each utterance. In stutterers, the end-tidal CO2 (ETCO2), the area under CO2/a time curve (SCO2), and the average emission of CO2 (ECO2 = SCO2/tbreath_cycle) for the CO2 peaks connected with the phrases containing tonic errors (with reference to rest respiration) were higher than those connected with fluent phrases (p<0.000001). Thus, a tendency to hypoventilation caused by tonic errors was observed. The factors of breath ergonomics while speaking FE (based on both signals) of stutterers were lower than those in fluent speakers (p<0.001). Using VF by stutterers increased FE (p<0.005) and decreased stuttering intensity.

19

Identification of mechanical parameters of respiratory system during ventilatory support of lungs

Pałko K. J., Kozarski M., Darowski M.

Biocybernetics and Biomedical Engineering

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2005

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Vol. 25, no. 1

73-81

EN

Identification of mechanical parameters of lungs by using a pressure method with an added compliance is presented in this paper. This method is based on periodically connecting an additional external mechanical compliance to the respirator-lungs circuit, to determine the values of the mechanical parameters of the respiratory system from measurements of the pressure in specific phases of the respiratory cycle. The expiratory flow was measured to estimate the time constant and the respiratory resistance. The identification of the parameters of lungs is connected with the dynamic signal analysis of the pressure courses registered in a very short time (< 200 ms) at the beginning of the expiratory phase, when the respiratory muscles are non-active. The measurement system is driven by the computer, which is also used to analyse the signals received from the lung model. The results confirm that the measurement time of 200 ms is sufficient to determine the lung compliance.

20

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.