The correlation between baroreflex sensitivity (BRS) and the spectrum component at a frequency of 0.1 Hz of pulse intervals (PI) and systolic blood pressure (SBP) was studied. SBP and PI of 51 subjects were recorded beat-to-beat at rest (3 min), during exercise (0.5 W/kg of body weight, 9 min), and at rest (6 min) after exercise. BRS was determined by a spectral method (a modified alpha index technique). The subjects were divided into groups according to the spectral amplitude of SBP at a frequency of 0.1 Hz. The following limits of amplitude (in mm Hg) were used: very high ≥ 5.4 (VH); high 5.4 > H ≥ 3 (H); medium 3 > M ≥ 2 (M), low < 2 (L). We analyzed the relationships between 0.1 Hz variability in PI and BRS at rest, during the exercise and during recovery in subgroups VH, H, M, L. The 0.1 Hz variability of PI increased significantly with increasing BRS in each of the groups with identical 0.1 Hz variability in SBP. This relationship was shifted to the lower values of PI variability at the same BRS with a decrease in SBP variability. The primary SBP variability increased during exercise. The interrelationship between the variability of SBP, PI and BRS was identical at rest and during exercise. A causal interrelationship between the 0.1 Hz variability of SBP and PI, and BRS was shown. During exercise, the increasing primary variability in SBP due to sympathetic activation was present, but it did not change the relationship between variability in pulse intervals and BRS., N. Honzíková, A. Krtička, Z. Nováková, E. Závodná., and Obsahuje bibliografii
The aim of this study was to assess carotid baroreflex responses during graded lower body negative pressure (LBNP). In 12 healthy subjects (age 29±4 years) we applied sinusoidal neck suction (0 to -30 mmHg) at 0.1 Hz to examine the sympathetic modulation of the heart and blood vessels and at 0.2 Hz to assess the effect of parasympathetic stimulation on the heart. Responses to neck suction were determined as the change in spectral power of RR-interval and blood pressure from baseline values. Measurements were carried out during progressive applications (0 to -50 mmHg) of LBNP. Responses to 0.1 and 0.2 Hz carotid baroreceptor stimulations during low levels of LBNP (-10 mmHg) were not significantly different from those measured during baseline. At higher levels of LBNP, blood pressure responses to 0.1 Hz neck suction were significantly enhanced, but with no significant change in the RR-interval response. LBNP at all levels had no effect on the RR-interval response to 0.2 Hz neck suction. The unchanged responses of RR-interval and blood pressure to neck suction during low level LBNP at -10 mmHg suggest no effect of cardiopulmonary receptor unloading on the carotid arterial baroreflex, since this LBNP level is considered to stimulate cardiopulmonary but not arterial baroreflexes. Enhanced blood pressure responses to neck suction during higher levels of LBNP are not necessarily the result of a reflex interaction but may serve to protect the circulation from fluctuations in blood pressure while standing., C. M. Brown, M. J. Hecht, B. Neundörfer, M. J. Hilz., and Obsahuje bibliografii
Increased blood pressure variability (BPV) and decreased interbeat interval (heart rate, respectively) variability (IBIV, HRV respectively) are associated with cardiovascular disorders. The aim of this study was to evaluate the reproducibility of BPV and IBIV (HRV) in young healthy individuals. Blood pressure and inter-beat intervals (instantaneous values of heart rate, respectively) were recorded beat-to-beat at rest (5 min, Finapres, breathing at 0.33 Hz) in 152 subjects (19-24 years) 3 times in periods of one week. Systolic (SBPV0.1r/SBPV0.1a) and diastolic (DBPV0.1r/DBPV0.1a) blood pressure variability in relative (r.u.) and absolute (mmHg2/Hz) units and inter-beat interval (IBIV0.1r/IBIV0.1a,), or heart rate (HRV0.1r/HRV0.1a) variability in relative (r.u.) and absolute (ms2/Hz, resp. mHz2) units were determined by the spectral method as spectral power at the frequency of 0.1 Hz and 0.33 Hz (SBPV0.33r/SBPV0.33a, DBPV0.33r/DBPV0.33a, IBIV0.33r/IBIV0.33a, HRV0.33r/HRV0.33a). All indices of BPV and IBIV (resp. HRV) revealed a lower intraindividual than interindividual variability (ANOVA; p<0.001). The mean values of all indices in each subject significantly correlated with distribution of individual values in the same subject (Pearson's correlation coefficient; p<0.001). Blood pressure and inter-beat interval (heart rate) variability is an individual characteristic feature., M. Jíra ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy