Heart rate and blood pressure variability in normal subjects compared withdata from beat-to-beat models developed from de Boer's model of the cardiovascular system

The objective of this study was to assess the ability of de Beer's model of the cardiovascular system to reproduce the heart rate and blood pressure v ariability observed in a range of normal subjects, and to make modification s to improve its performance. EGG, blood pressure and chest wall movement w ere recorded from 12 normal human subjects during controlled breathing. For each beat, systolic pressure, diastolic pressure, arterial time constant a nd RR interval were extracted. RR interval and systolic pressure spectral p ower in low and high frequency bands and the baroreflex sensitivity index, cr, were then determined. For each subject, mean values were input to the m odel and the beat-to-beat output compared with the actual data for that sub ject. Finally, the effects of reducing the influence of baroreflex on perip heral vascular resistance and of providing separate sympathetic and vagal b aroreflex sensitivities were assessed. Simulations resulted in data which w ere qualitatively similar to those of each subject's recording. With the mo difications. the log ratio of simulated to real data improved from 7.2 to 1 .5 (p = 0.003) for low frequency RR, from 0.27 to 0.55 (p = 0.011) for high frequency RR and from 8.5 to 0.9 (p = 0.003) for low frequency systolic pr essure. We conclude that de Beer's model reproduces many of the characteris tics of heart rate and blood pressure variability, and our modifications to baroreflex sensitivities and the feedback effect on peripheral resistance resulted in significant improvements.