The aim of this study was to obtain a detailed analysis of the relationship between the finger arterial compliance C [ml/mm Hg] and the arterial transmural pressure P(t) [mm Hg]. We constructed a dynamic plethysmograph enabling us to set up a constant pressure P(css) [mm Hg] and a superimposed fast pressure vibration in the finger cuff (equipped with a source of infra-red light and a photoelectric sensor for the measurement of arterial volume). P(css) could be set on the required time interval in steps ranging between 30 and 170 mm Hg, and on sinusoidal pressure oscillation with an amplitude P(ca) (2 mm Hg) and a frequency f (20, 25, 30, 35, 40 Hz). At the same time continuous blood pressure BP was measured on the adjacent finger (Portapres). We described the volume dependence of a unitary arterial length on the time-varying transmural pressure acting on the arterial wall (externally P(css)+P(ca).sin(2pif), internally BP) by a second-order differential equation for volume. This equation was linearized within a small range of selected BP. In the next step, a Fourier transform was applied to obtain the frequency characteristic in analytic form of a complex linear combination of frequency functions. While series of oscillations [P(ca), f] were applied for each P(css), the corresponding response of the plethysmogram was measured. Amplitude spectra were obtained to estimate coefficients of the frequency characteristic by regression analysis. We determined the absolute value: elastance E, and its inverse value: compliance (C=1/E). Then, C=C(P(t)) was acquired by applying sequences of oscillations for different P(css) (and thus P(t)) by the above-described procedure. This methodology will be used for the study of finger arterial compliance in different physiological and pathological conditions.
- MeSH
- arterie fyziologie MeSH
- diagnostické techniky kardiovaskulární * přístrojové vybavení MeSH
- krevní tlak MeSH
- lidé MeSH
- mladý dospělý MeSH
- modely kardiovaskulární MeSH
- pletysmografie metody MeSH
- poddajnost MeSH
- prsty ruky MeSH
- senioři MeSH
- vibrace MeSH
- Check Tag
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Baroreflex regulation of blood pressure primarily moderates its fluctuations and also affects mean blood pressure. Heart rate baroreflex sensitivity is described as changes of the inter-beat interval induced by a change of blood pressure of 1 mmHg (BRS). BRS is decreased in many cardiovascular diseases (hypertension, diabetes mellitus, obesity, cardiac failure, etc.). Decreased BRS in disposed individuals, especially after myocardial infarction, increases the risk of sudden cardiac death. Therefore, early diagnosis of BRS decrease gains in importance. This article describes different methods of determination of baroreflex sensitivity. The methods are based on evaluation of the spontaneous fluctuation of heart rate and blood pressure (spectral, sequential or nonlinear methods), or of primary changes of blood pressure induced by a vasoactive substance or a physiological manoeuvre and corresponding changes of cardiac intervals (Valsalva manoeuvre, phenylephrine administration). Each method has its advantages and disadvantages resulting from a different difficulty of calculation or from inclusion of different deviations in the results, which are not directly linked with baroreflex. Baroreflex regulating total peripheral resistance is less described. A mathematical model of baroreflex blood pressure regulation by fluctuation of heart rate and peripheral resistance is presented in this paper.
- MeSH
- baroreflex fyziologie MeSH
- cévní rezistence MeSH
- kardiovaskulární nemoci patofyziologie MeSH
- krevní tlak fyziologie MeSH
- lidé MeSH
- měření krevního tlaku MeSH
- modely kardiovaskulární * MeSH
- srdeční frekvence fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- anglický abstrakt MeSH
- časopisecké články MeSH
- přehledy MeSH
Re-evaluation of all functions of baroreflex by means of a simple mathematical model of circulation was the aim of the present study. The following states are modelled: 1. Rest. 2. Immediately after baroreceptor denervation. 3. Several days after denervation. 4. Physical exercise before denervation. 5. Physical exercise several days after denervation. Despite the same cardiac contractility and the same vasodilatation in working muscles as before denervation the cardiac output is by one third lower after baroreceptor denervation. In conclusion, a model simulation revealed the common regulation of blood pressure and blood volume by baroreflex and kidneys as a primary function of baroreflex.
- Publikační typ
- časopisecké články MeSH
