Ventilation related heart rate oscillations - respiratory sinus arrhythmia (RSA) - originate in human from several mechanisms. Two most important of them - the central mechanism (direct communication between respiratory and cardiomotor centers), and the peripheral mechanism (ventilation-associated blood pressure changes transferred to heart rate via baroreflex) have been described in previous studies. The major aim of this study was to compare the importance of these mechanisms in the generation of RSA non-invasively during various states by quantifying the strength of the directed interactions between heart rate, systolic blood pressure and respiratory volume signals. Seventy-eight healthy volunteers (32 male, age range: 16.02-25.77 years, median age: 18.57 years) participated in this study. The strength of mutual interconnections among the spontaneous beat-to-beat oscillations of systolic blood pressure (SBP), R-R interval (RR signal) and respiration (volume changes - RESP signal) was quantified during supine rest, orthostatic challenge (head-up tilt, HUT) and cognitive load (mental arithmetics, MA) using bivariate and trivariate measures of cardio-respiratory information transfer to separate baroreflex and nonbaroreflex (central) mechanisms. Our results indicate that both basic mechanisms take part in RSA generation in the intact cardiorespiratory control of human subjects. During orthostatic and mental challenges baroreflex based peripheral mechanism becomes more important.
- MeSH
- baroreflex fyziologie MeSH
- dospělí MeSH
- elektrokardiografie metody MeSH
- fotopletysmografie metody MeSH
- krevní tlak fyziologie MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- respirační sinusová arytmie fyziologie MeSH
- srdeční frekvence fyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
A wobble board (WB) is a balance rehabilitation tool that is used in physiotherapy to improve strength and stability. The WB tested in this study includes a sensory module for measuring patients' tilt and rotation during stance. The aim of this study was to assess the reliability and validity of a balance measurement using a WB. Thirty healthy young adults participated in this study. The participants stood on the WB to simultaneously record the tilt of the WB and the center of pressure data using a force plate. The data were recorded during five measurement sessions on various days, with four trials each. Sways, velocities and indexes of complexity (CI) were computed. For reliability assessment, we used intra-class correlation coefficients within and between sessions; for validity, we computed Spearman correlation coefficients. The velocities and CI showed good intra-session reliability, and the sways showed mostly poor intra-session reliability. The results of inter-session reliability showed good to excellent reliability for CI, poor reliability for sways and poor to good reliability for velocities. The Spearman correlation coefficient showed excellent agreement between the mean velocities computed from the force plate and the WB. Our results confirm that the WB tested is suitable for stability assessment in young adults.
- MeSH
- entropie * MeSH
- lidé MeSH
- mladý dospělý MeSH
- posturální rovnováha * MeSH
- reprodukovatelnost výsledků MeSH
- Check Tag
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
In previous studies, one of the systolic time intervals - preejection period (PEP) - was used as an index of sympathetic activity reflecting the cardiac contractility. However, PEP could be also influenced by several other cardiovascular variables including preload, afterload and diastolic blood pressure (DBP). The aim of this study was to assess the behavior of the PEP together with other potentially confounding cardiovascular system characteristics in healthy humans during mental and orthostatic stress (head-up tilt test - HUT). Forty-nine healthy volunteers (28 females, 21 males, mean age 18.6 years (SD=1.8 years)) participated in the study. We recorded finger arterial blood pressure by volume-clamp method (Finometer Pro, FMS, Netherlands), PEP, thoracic fluid content (TFC) - a measure of preload, and cardiac output (CO) by impedance cardiography (CardioScreen® 2000, Medis, Germany). Systemic vascular resistance (SVR) - a measure of afterload - was calculated as a ratio of mean arterial pressure and CO. We observed that during HUT, an expected decrease in TFC was accompanied by an increase of PEP, an increase of SVR and no significant change in DBP. During mental stress, we observed a decrease of PEP and an increase of TFC, SVR and DBP. Correlating a change in assessed measures (delta values) between mental stress and previous supine rest, we found that deltaPEP correlated negatively with deltaCO and positively with deltaSVR. In orthostasis, no significant correlation between deltaPEP and deltaDBP, deltaTFC, deltaCO, deltaMBP or deltaSVR was found. We conclude that despite an expected increase of sympathetic activity during both challenges, PEP behaved differently indicating an effect of other confounding factors. To interpret PEP values properly, we recommend simultaneously to measure other variables influencing this cardiovascular measure.
- MeSH
- krevní tlak fyziologie MeSH
- lidé MeSH
- minutový srdeční výdej fyziologie MeSH
- mladiství MeSH
- mladý dospělý MeSH
- psychický stres patofyziologie psychologie MeSH
- srdeční frekvence fyziologie MeSH
- sympatický nervový systém fyziologie MeSH
- tepový objem fyziologie MeSH
- test na nakloněné rovině metody MeSH
- Check Tag
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
Photometry enables determination of a substance in solution based on the absorption of monochromatic light. A simple photometer was designed, which can serve for teaching the principles of photometry and photometric determinations. The designed photometer is small, compact, modular, portable and inexpensive.