A mathematical model of myocardial perfusion based on the lattice Boltzmann method (LBM) is proposed and its applicability is investigated in both healthy and diseased cases. The myocardium is conceptualized as a porous material in which the transport and mass transfer of a contrast agent in blood flow is studied. The results of myocardial perfusion obtained using LBM in 1D and 2D are confronted with previously reported results in the literature and the results obtained using the mixed-hybrid finite element method. Since LBM is not suitable for simulating flow in heterogeneous porous media, a simplified and computationally efficient 1D-analog approach to 2D diseased case is proposed and its applicability discussed.

• MeSH
• Finite Element Analysis * MeSH
• Contrast Media MeSH
• Coronary Circulation physiology   MeSH
• Humans MeSH
• Models, Cardiovascular * MeSH
• Computer Simulation MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

• MeSH
• Chemical Actions and Uses MeSH
• Risk Assessment MeSH
• Hazardous Substances administration & dosage   MeSH
• Environmental Exposure MeSH

• Conspectus
• Životní prostředí a jeho ochrana
• NML Fields
• chemie, klinická chemie
• environmentální vědy
• NML Publication type
• publikace WHO

• MeSH
• Biology MeSH
• Physiology MeSH
• Mathematics MeSH

• Conspectus
• Přírodní vědy. Matematické vědy
• NML Fields
• fyziologie
• biologie
• přírodní vědy

Cieľ práce: Dokázať, že pri výrazne nehomogénnej distribúcii plynov v ťažko patologicky postihnutých pľúcach je možné viachladinovou UVP zlepšiť distribúciu plynov do pomalých bronchoalveolárnych kompartmentov bez rizikovej zmeny objemového zaťaženia rýchlych kompartmentov. Autor realizoval softvérový matematický model viackompartmentných nehomogénne postihnutých pľúc, ktoré „ventiloval“ novým spôsobom UVP – tzv. trojhladinovou ventiláciou. Viachladinovú ventiláciu definuje ako spôsob (modifikáciu) UVP, pričom základnú hladinu ventilácie tvorí ventilačný režim CMV, PCV, alebo PS (ASB) a nadstavbu, tzv. ventiláciu na pozadí tvorí hladina PEEPh (PEEP high) s meniteľnou frekvenciou a trvaním prechodu medzi jednotlivými hladinami PEEPh/PEEP. Názov a sídlo pracoviska: Oddelenie anestéziológie a intenzívnej medicíny. Materiál a metodika:Viachladinová ventilácia na 3 tlakových úrovniach realizovaná matematickým modelom ako kombinácia tlakovo kontrolovanej ventilácie (PCV) a dvoch úrovní PEEP a (PEEPh). Výsledky: Pri porovnávaní jednohladinovej UVP v režime PC s tzv. trojhladinovou ventiláciou ako kombináciou PC+PEEPh/PEEP autor zistil, že plnenie pomalých kompartmentov sa na modeli výrazne zlepšilo, a to rádove o 50–60 % oproti východzej hodnote. Tento rozdiel v absolútnom vyjadrení u obštrukčných kompartmentov dosahuje 2 až 10-násobok objemu, respektive 1,2–3-násobné zvýšenie MV v kompartmentoch k4 a k5. Záver: Matematickým modelom sa dá preukázať, že aplikácia tzv. trojhladinovej UVP môže viesť k výrazným zmenám v distribúcii plynov v nehomogénne patologickým procesom postihnutom pľúcnom parenchýme. Matematický model si vyžiada klinické overenie, aby boli zodpovedané otázky účinnosti tejto modifikácie UVP.

Objective: Considering the issues of intermittent positive pressure ventilation (IPPV) in non-homogenous pathological lung processes, the author built a mathematical model of tri-compartment non-homogenously injured lungs ventilated with a new mode of IPPV – multi-level ventilation. The author defines multi-level ventilation as a type (modification) of IPPV consisting of background ventilation using the CMV, PCV or PS (ASB) ventilation mode and an added level called “on-background ventilation“ consisting of multiple levels of PEEPh (PEEP high) with variable frequency and duration of transition between individual levels of PEEP. The objective was to prove whether in cases of considerably non-homogenous gas distribution in acute pathological disorders of the lungs it is possible to improve gas distribution into slow broncho-alveolar compartments while only minimally or not at all increasing the volume load of the fast compartments by using the multi-level IPPV. Setting: Department of Anaesthesiology and Intensive Care Unit. Materials and methods: Multi-level ventilation on three pressure levels was carried out by a mathematical model as a combination of pressure-controlled ventilation (PCV) and two levels of PEEP: PEEP (constant) and PEEPh (PEEP high). Results: Comparing single-level IPPV in the PCV mode with the tri-level ventilation (PCV+PEEPh/PEEP), the author found that the loading of the slow compartments in the model was considerably improved by as much as 50–60% in comparison to the baseline value. This difference, in absolute figures, reached as much as a 2–10 times increase in volume, or a 1.2–3 times increase in minute ventilation in compartments k4 and k5. Conclusions: The mathematical model proves that the application of multi-level IPPV can achieve considerable changes in gas distribution in the lung parenchyma affected by a non-homogenous pathological process. The mathematical model requires further verification in the clinical setting to answer questions regarding its efficacy.

• MeSH
• Models, Biological MeSH
• Ventilators, Mechanical trends   MeSH
• Respiration Disorders physiopathology   therapy   MeSH
• Respiratory Distress Syndrome therapy   MeSH
• Respiration, Artificial methods   instrumentation   MeSH

BACKGROUND: Optical coherence tomography (OCT) is a well established imaging technique with different applications in preclinical research and clinical practice. The main potential for its application lies in the possibility of noninvasively performing "optical biopsy". Nevertheless, functional OCT imaging is also developing, in which perfusion imaging is an important approach in tissue function study. In spite of its great potential in preclinical research, advanced perfusion imaging using OCT has not been studied. Perfusion analysis is based on administration of a contrast agent (nanoparticles in the case of OCT) into the bloodstream, where during time it specifically changes the image contrast. Through analysing the concentration-intensity curves we are then able to find out further information about the examined tissue. METHODS: We have designed and manufactured a tissue mimicking phantom that provides the possibility of measuring dilution curves in OCT sequence with flow rates 200, 500, 1000 and 2000 μL/min. The methodology comprised of using bolus of 50 μL of gold nanorods as a contrast agent (with flow rate 5000 μL/min) and continuous imaging by an OCT system. After data acquisition, dilution curves were extracted from OCT intensity images and were subjected to a deconvolution method using an input-output system description. The aim of this was to obtain impulse response characteristics for our model phantom within the tissue mimicking environment. Four mathematical tissue models were used and compared: exponential, gamma, lagged and LDRW. RESULTS: We have shown that every model has a linearly dependent parameter on flow ([Formula: see text] values from 0.4914 to 0.9996). We have also shown that using different models can lead to a better understanding of the examined model or tissue. The lagged model surpassed other models in terms of the minimisation criterion and [Formula: see text] value. CONCLUSIONS: We used a tissue mimicking phantom in our study and showed that OCT can be used for advanced perfusion analysis using mathematical model and deconvolution approach. The lagged model with three parameters is the most appropriate model. Nevertheless, further research have to be performed, particularly with real tissue.

• MeSH
• Printing, Three-Dimensional MeSH
• Equipment Design MeSH
• Phantoms, Imaging * MeSH
• Contrast Media chemistry   MeSH
• Metal Nanoparticles chemistry   MeSH
• Nanotubes chemistry   MeSH
• Tomography, Optical Coherence methods   MeSH
• Image Processing, Computer-Assisted MeSH
• Models, Theoretical * MeSH
• Tissue Scaffolds chemistry   MeSH
• Gold chemistry   MeSH
• Publication type
• Journal Article MeSH

• MeSH
• Humans MeSH
• Mechanical Phenomena MeSH
• Tensile Strength MeSH
• Surgery, Plastic MeSH
• Polyesters MeSH
• Polypropylenes MeSH
• Tendons physiology   MeSH
• Statistics as Topic MeSH
• Sutures classification   MeSH
• Models, Theoretical MeSH
• Materials Testing methods   instrumentation   statistics & numerical data   MeSH
• Check Tag
• Humans MeSH

• MeSH
• Finite Element Analysis * utilization   MeSH
• Models, Anatomic MeSH
• Arteries * anatomy & histology   physiology   MeSH
• Biomechanical Phenomena MeSH
• Blood Pressure MeSH
• Humans MeSH
• Mechanical Phenomena MeSH
• Computer Simulation MeSH
• Elasticity physiology   MeSH
• Statistics as Topic MeSH
• Models, Theoretical MeSH
• Materials Testing * methods   instrumentation   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Research Support, Non-U.S. Gov't MeSH

Polyaniline cryogel is a new unique form of polyaniline combining intrinsic electrical conductivity and the material properties of hydrogels. It is prepared by the polymerization of aniline in frozen poly(vinyl alcohol) solutions. The biocompatibility of macroporous polyaniline cryogel was demonstrated by testing its cytotoxicity on mouse embryonic fibroblasts and via the test of embryotoxicity based on the formation of beating foci within spontaneous differentiating embryonic stem cells. Good biocompatibility was related to low contents of low-molecular-weight impurities in polyaniline cryogel, which was confirmed by liquid chromatography. The adhesion and growth of embryonic stem cells, embryoid bodies, cardiomyocytes, and neural progenitors prove that polyaniline cryogel has the potential to be used as a carrier for cells in tissue engineering or bio-sensing. The surface energy as well as the elasticity and porosity of cryogel mimic tissue properties. Polyaniline cryogel can therefore be applied in bio-sensing or regenerative medicine in general, and mainly in the tissue engineering of electrically excitable tissues.

• MeSH
• Algorithms MeSH
• Aniline Compounds chemistry   MeSH
• Biocompatible Materials chemistry   MeSH
• Cell Culture Techniques MeSH
• Electric Conductivity MeSH
• Fibroblasts MeSH
• Cryogels chemistry   MeSH
• Mechanical Phenomena MeSH
• Elastic Modulus MeSH
• Mice MeSH
• Porosity MeSH
• Models, Theoretical MeSH
• Materials Testing MeSH
• Tissue Engineering MeSH
• Cell Survival MeSH
• Chromatography, High Pressure Liquid MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Mnohé materiály používané ve farmaceutické praxi a také mnohé biologické materiály stojí svými mechanickými vlastnostmi mezi pevnými pružnými tělesy a kapalinami. Tyto materiály nazýváme viskoelastické látky. Pro popis mechanických vlastností viskoelastických materiálů nevystačíme s metodikami, které poskytuje klasická teorie pružnosti a pevnosti či hydromechanika, a používáme obecnějšího aparátu, který vychází z reologie. Jako charakteristiky obsahující informace o mechanickém chování viskoelastických těles se v reologii nejčastěji používají křivky toku. Křivky toku poskytují bezprostředně informace o mechanických vlastnostech studovaných materiálů, pro podrobnější analýzu je třeba nalézt vhodný reologický model a určit jeho parametry. Běžně používané metody identifikace a odhadu pareimetrů reologických modelů nejsou dostatečně obecné a nevyužívají plně informací, které lze z křivek toku získat. Obecnou a plně propracovanou metodiku poskytuje teorie identifikace systémů. Spolu s využitím matematického aparátu, vycházejícího z Laplaceovy transformace, lze odvodit relativně jednoduchou a prakticky aplikovatelnou metodiku, umožňující plně využít informace, které obsahují křivky toku. Tato práce obsahuje v prvních dvou kapitolách analýzu současného stavu v oblasti vytváření reologických modelů. Hlavním přínosem práce je přehled teoretického aparátu po identifikaci a výpočet prvků modelů reologických systémů včetně příkladu, na němž je demonstrována praktická aplikace metodiky. V závěru je uveden obecný návod praktického postupu.

The methodology of description and quantification of mechanical properties of visco-elastic materials is particularly important for drug production as well as for pharmaceutical applications. Of similar importance is this methodology for biomechanics and other biological disciplines, as many biological materials belong to the category of visco-elastic bodies. Methods derived from the theory of elastic bodies or hydrodynamics are not adequate for the quantification of mechanical properties of these materials. Application of more general rheological methods is necessary in these cases. In rheology, the so-called creep curves are most frequently used as a source of information on the mechanical behavior of visco-elastic materials. Further, for more exact analysis, rheological models are often derived from the creep curves. Classical methods of identification and parameter estimation of rheological models are not sufficiently general and do not derive all information involved in creep curves. A significant contribution is the application of the general theory of systems, theory of system identification, and mathematical methodology of Laplace transformation to this field. Practical application of these methods is often relatively simple. The paper presents the necessary theoretical background and a practical guide for utilization of this methodology.

• MeSH
• Biomechanical Phenomena MeSH
• Pharmaceutic Aids analysis   MeSH
• Research Support as Topic MeSH
• Colloids MeSH
• Rheology MeSH
• Models, Theoretical MeSH

Outdoor breathing trials with simulated avalanche snow are fundamental for the research of the gas exchange under avalanche snow, which supports the development of the international resuscitation guidelines. However, these studies have to face numerous problems, including unstable weather and variable snow properties. This pilot study examines a mineral material perlite as a potential snow model for studies of ventilation and gas exchange parameters. Thirteen male subjects underwent three breathing phases-into snow, wet perlite and dry perlite. The resulting trends of gas exchange parameters in all tested materials were similar and when there was a significant difference observed, the trends in the parameters for high density snow used in the study lay in between the trends in dry and wet perlite. These findings, together with its stability and accessibility year-round, make perlite a potential avalanche snow model material. Perlite seems suitable especially for simulation and preparation of breathing trials assessing gas exchange under avalanche snow, and potentially for testing of new avalanche safety equipment before their validation in real snow.The study was registered in ClinicalTrials.gov on January 22, 2018; the registration number is NCT03413878.

• MeSH
• Adult MeSH
• Double-Blind Method MeSH
• Respiration * MeSH
• Cardiopulmonary Resuscitation methods   MeSH
• Cross-Over Studies MeSH
• Avalanches * MeSH
• Humans MeSH
• Young Adult MeSH
• Aluminum Oxide * MeSH
• Silicon Dioxide * MeSH
• Pilot Projects MeSH
• Prospective Studies MeSH
• Snow * MeSH
• Models, Theoretical MeSH
• Simulation Training MeSH
• Pulmonary Gas Exchange physiology   MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Randomized Controlled Trial MeSH
• Geographicals
• Czech Republic MeSH