Reproducibility of blood pressure and inter-beat interval variability in man.

Increased blood pressure variability (BPV) and decreased inter-beat 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 (SBPV(0.1r)/SBPV(0.1a)) and diastolic (DBPV(0.1r)/DBPV(0.1a)) blood pressure variability in relative (r.u.) and absolute (mmHg(2)/Hz) units and inter-beat interval (IBIV(0.1r)/IBIV(0.1a)), or heart rate (HRV(0.1r)/HRV(0.1a)) variability in relative (r.u.) and absolute (ms(2)/Hz, resp. mHz(2)) units were determined by the spectral method as spectral power at the frequency of 0.1 Hz and 0.33 Hz (SBPV(0.33r)/SBPV(0.33a), DBPV(0.33r)/DBPV(0.33a), IBIV(0.33r)/IBIV(0.33a), HRV(0.33r)/HRV(0.33a)). 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.