Arterial compliance (AC) is an important cardiovascular parameter characterizing mechanical properties of arteries. AC is significantly influenced by arterial wall structure and vasomotion, and it markedly influences cardiac load. A new method, based on a two-element Windkessel model, has been recently proposed for estimating AC as the ratio of the time constant T of the diastolic blood pressure decay and peripheral vascular resistance derived from clinically available stroke volume measurements and selected peripheral blood pressure parameters which are less prone to peripheral distortions. The aim of this study was to validate AC estimation using a virtual population generated by in silico model of the systemic arterial tree. In the second part of study, we analysed causal coupling between AC oscillations and variability of its potential determinants - systolic blood pressure and heart rate in healthy young human subjects. The pool of virtual subjects (n=3818) represented an extensive AC distribution. AC was estimated from the peripheral blood pressure curve and by the standard method from the aortic blood pressure curve. The proposed method slightly overestimated AC set in the model but both ACs were strongly correlated (r=0.94, p<0.001). In real data, we observed that AC dynamics was coupled with basic cardiovascular parameters variability independently of the autonomic nervous system state. In silico analysis suggests that AC can be reliably estimated by noninvasive method. The analysis of short-term AC variability together with its determinants could improve our understanding of factors involved in AC dynamics potentially improving assessment of AC changes associated with atherosclerosis process. Key words Arterial compliance, Cardiovascular model, Arterial blood pressure, Causal analysis, Volume-clamp photoplethysmography.
- MeSH
- arterie * fyziologie MeSH
- cévní rezistence fyziologie MeSH
- dospělí MeSH
- krevní tlak * fyziologie MeSH
- lidé MeSH
- mladý dospělý MeSH
- modely kardiovaskulární * MeSH
- počítačová simulace * MeSH
- poddajnost MeSH
- srdeční frekvence fyziologie MeSH
- tuhost cévní stěny fyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- validační studie MeSH
Understanding the mechanics of the respiratory system is crucial for optimizing ventilator settings and ensuring patient safety. While simple models of the respiratory system typically consider only flow resistance and lung compliance, lung tissue resistance is usually neglected. This study investigated the effect of lung tissue viscoelasticity on delivered mechanical power in a physical model of the respiratory system and the possibility of distinguishing tissue resistance from airway resistance using proximal pressure measured at the airway opening. Three different configurations of a passive physical model of the respiratory system representing different mechanical properties (Tissue resistance model, Airway resistance model, and No-resistance model) were tested. The same volume-controlled ventilation and parameters were set for each configuration, with only the inspiratory flow rates being adjusted. Pressure and flow were measured with a Datex-Ohmeda S/5 vital signs monitor (Datex-Ohmeda, Madison, WI, USA). Tissue resistance was intentionally tuned so that peak pressures and delivered mechanical energy measured at airway opening were similar in Tissue and Airway Resistance models. However, measurements inside the artificial lung revealed significant differences, with Tissue resistance model yielding up to 20% higher values for delivered mechanical energy. The results indicate the need to revise current methods of calculating mechanical power delivery, which do not distinguish between tissue resistance and airway flow resistance, making it difficult to evaluate and interpret the significance of mechanical power delivery in terms of lung ventilation protectivity.
- Klíčová slova
- elastické tahy,
- MeSH
- analýza zatížení zubů MeSH
- lidé MeSH
- mechanický stres MeSH
- ortodontické aparáty * MeSH
- pružnost MeSH
- techniky in vitro MeSH
- testování materiálů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
BACKGROUND: The purpose of dermal substitutes is to mimic the basic properties of the extracellular matrix of human skin. The application of dermal substitutes to the defect reduces the formation of hypertrophic scars and improves the scar quality. This study aims to develop an original dermal substitute enriched with stable fibroblast growth factor 2 (FGF2-STAB®) and test it in an animal model. METHODS: Dermal substitutes based on collagen/chitosan scaffolds or collagen/chitosan scaffolds with nanofibrous layer were prepared and enriched with FGF2-STAB® at concentrations of 0, 0.1, 1.0, and 10.0 μg ‧ cm-2. The performance of these dermal substitutes was tested in vivo on artificially formed skin defects in female swine. The outcomes were evaluated using cutometry at 3 and 6 months. In addition, visual appearance was assessed based on photos of the scars at 1-month, 3-month and 6-month follow-ups using Yeong scale and Visual Analog Scale. RESULTS: The dermal substitute was fully integrated into all defects and all wounds healed successfully. FGF2-STAB®-enriched matrices yielded better results in cutometry compared to scaffolds without FGF2. Visual evaluation at 1, 3, and 6 months follow-ups detected no significant differences among groups. The FGF2-STAB® effectiveness in improving the elasticity of scar tissues was confirmed in the swine model. This effect was independently observed in the scaffolds with nanofibres as well as in the scaffolds without nanofibres. CONCLUSION: The formation of scars with the best elasticity was exhibited by addition 1.0 μg ‧ cm-2of FGF2-STAB® into the scaffolds, although it had no significant effect on visual appearance at longer follow-ups. This study creates the basis for further translational studies of the developed product and its progression into the clinical phase of the research.
- MeSH
- chitosan * MeSH
- fibroblastový růstový faktor 2 * MeSH
- hojení ran účinky léků MeSH
- jizva hypertrofická MeSH
- kolagen MeSH
- kůže MeSH
- modely nemocí na zvířatech MeSH
- nanovlákna terapeutické užití MeSH
- popálení MeSH
- prasata MeSH
- pružnost * MeSH
- tkáňové podpůrné struktury MeSH
- umělá kůže * MeSH
- viskozita MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND AND AIMS: Tympanosclerosis (TS) is a scarring process that may occur during otitis media. Aortic stiffness (AS) is a significant predictor for the development of heart diseases due to its close relationship with atherosclerosis. Similar pathophysiological processes based on inflammation may explain both TS and AS formation. This study aimed to determine echocardiographically whether aortic elasticity is impaired in TS-detected patients and to correlate blood inflammatory parameters with TS and aortic elasticity. METHODS: Ninety-eight participants diagnosed with chronic otitis media were enrolled in the study. TS-detected 42 participants were assigned to the study group, while 56 without TS constituted the control group. The two groups' demographic, clinical, echocardiographic, and laboratory characteristics were comparable. RESULTS: Demographic, clinical, and laboratory parameter differences were insignificant. Hs-CRP, neutrophil-to-lymphocyte ratio, and systemic immune-inflammation index were significantly higher in the study group than in the control group (P=0.018, P=0.003, P=0.019, respectively). The study group had significantly lower aortic strain (11.80 ± 4.84 vs. 16.30 ± 3.91; P<0.001) and distensibility (5.23 ± 2.68 vs. 7.24 ± 2.89; P=0.001) values than the control group. The AS index was significantly higher in the study group than in the control group (4.81 ± 2.41 vs. 3.12 ± 1.02; P<0.001). CONCLUSION: In TS-detected patients, AS parameters were found to be impaired. Aortic elasticity parameters measured by echocardiography, a non-invasive and easily accessible method, may signify early cardiovascular involvement in TS-developed patients.
- MeSH
- echokardiografie metody MeSH
- lidé MeSH
- otitis media * MeSH
- pružnost MeSH
- tuhost cévní stěny * fyziologie MeSH
- zánět MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Polypropylene (PP) belongs among the most important commodity plastics due to its widespread application. The color of the PP products can be achieved by the addition of pigments, which can dramatically affect its material characteristics. To maintain product consistency (dimensional, mechanical, and optical), knowledge of these implications is of great importance. This study investigates the effect of transparent/opaque green masterbatches (MBs) and their concentration on the physico-mechanical and optical properties of PP produced by injection molding. The results showed that selected pigments had different nucleating abilities, affecting the dimensional stability and crystallinity of the product. The rheological properties of pigmented PP melts were affected as well. Mechanical testing showed that the presence of both pigments increased the tensile strength and Young's modulus, while the elongation at break was significantly increased only for the opaque MB. The impact toughness of colored PP with both MBs remained similar to that of neat PP. The optical properties were well controlled by the dosing of MBs, and were further related to the RAL color standards, as demonstrated by CIE color space analysis. Finally, the selection of appropriate pigments for PP should be considered, especially in areas where dimensional and color stability, as well as product safety, are highly important.
- MeSH
- houby MeSH
- modul pružnosti MeSH
- plastické hmoty * MeSH
- polypropyleny * MeSH
- pomocné látky MeSH
- Publikační typ
- časopisecké články MeSH
The demand for biomaterials has been increasing along with the increase in the population of elderly people worldwide. The mechanical properties and high wear resistance of metallic biomaterials make them well-suited for use as substitutes or as support for damaged hard tissues. However, unless these biomaterials also have a low Young's modulus similar to that of human bones, bone atrophy inevitably occurs. Because a low Young's modulus is typically associated with poor wear resistance, it is difficult to realize a low Young's modulus and high wear resistance simultaneously. Also, the superelastic property of shape-memory alloys makes them suitable for biomedical applications, like vascular stents and guide wires. However, due to the low recoverable strain of conventional biocompatible shape-memory alloys, the demand for a new alloy system is high. The novel body-centered-cubic cobalt-chromium-based alloys in this work provide a solution to both of these problems. The Young's modulus of <001>-oriented single-crystal cobalt-chromium-based alloys is 10-30 GPa, which is similar to that of human bone, and they also demonstrate high wear and corrosion resistance. They also exhibit superelasticity with a huge recoverable strain up to 17.0%. For these reasons, the novel cobalt-chromium-based alloys can be promising candidates for biomedical applications.
AIM: To compare the elasticity of the sternocleidomastoid and trapezius muscles in patients with cervicogenic headache and in healthy volunteers. METHODS: The medical history of 23 patients with cervicogenic headache was taken with a focus on pain characteristics. Elasticity of the sternocleidomastoid and trapezius muscles was measured by using shear wave elastography. Results were then compared with 23 healthy volunteers. RESULTS: The sternocleidomastoid muscle was significantly stiffer in patients with cervicogenic headache compared to healthy volunteers. The stiffness increased gradually from the parasternal area, where it was negligible, to the area near the mastoid process where it reached over 20 kPa. There was no difference in the stiffness of the trapezius muscle. The stiffness of the sternocleidomastoid muscle does show a significant dependence on headache characteristics (e.g., laterality, severity, or frequency). CONCLUSION: The results of this pilot study show that patients with cervicogenic headache have a higher stiffness of the sternocleidomastoid muscle than healthy volunteers. These findings suggest that elastography could be used as a diagnostic tool in cervicogenic headache.
Arterial compliance is an important cardiovascular parameter characterizing mechanical and structural properties of arteries and significantly influencing ventricular-arterial coupling. Decreased arterial compliance is associated with several physiological states and pathological processes. Furthermore, arterial compliance is influenced by other cardiovascular parameters even at short time scales. Today, there are numerous noninvasive methods of estimation arterial compliance in vivo introducing some level of confusion about selection of the best method for particular application and measurement setting. In this review, the most common noninvasive methods of arterial compliance estimation are summarized, discussed and categorized. Finally, interpretation of estimated arterial compliance in the context of other possible confounders is discussed.
- MeSH
- arterie * fyziologie MeSH
- krevní tlak fyziologie MeSH
- poddajnost MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
A new method to estimate the selected viscoelastic parameters of foods using damped vibration analysis is presented for the evaluation of fruits and baked products. A flat disk is attached to the flat sample surface using a laser rangefinder that measures the sample thickness in advance, and it is locked by a trigger. Next, the trigger is released to allow the probe to press the sample through the force of gravity. The damped vibration of the probe caused by the deformation of the food is measured by monitoring the displacement of the probe via a linear encoder. The bulk modulus and viscosity are estimated using the fractional Zener model and mass. Young's modulus (E) is estimated independently by determining the maximum velocity of the probe using Hooke's law. Poisson's ratio (ν), and the shear modulus and viscosity are calculated by employing the estimated E and bulk modulus. The bulk modulus, bulk viscosity, shear modulus, shear viscosity, and E of apples were found to be higher than those of bananas. The bulk modulus, bulk viscosity, E, and shear modulus for white bread were lower than those for pound cake, but the ν values were higher, whereas those of sponge cake were intermediate. After drying the baked products for 1 day, most of the parameters of the samples increased, but the value of ν for white bread decreased. The proposed free-falling device estimated the four viscoelastic coefficients, Poisson's ratio, and Young's modulus of the food sample in less than 1 s.
- MeSH
- modul pružnosti MeSH
- pružnost * MeSH
- viskozita MeSH
- Publikační typ
- časopisecké články MeSH
