Aim: 

Mechanisms of short term diastolic pressure variability are less clear than systolic ones. It is also debated if arterial pressure variability depends on the same mechanisms in spontaneous and paced breathing. We compared hypertensive and control subjects in the two conditions.

Methods: 

In 15 never treated essential hypertensive patients (37.4 5.7 yrs), and 15 healthy control subjects (32.8 5.8), we recorded sphygmograms by Finapres technique. 5 min time series of systolic (BPs) and diastolic (BPd) blood pressure were analysed in spontaneous breathing (SB) and after pacing it at 0.2 Hz (PB). Spectral power density was calculated by FFT in the total .02-.4 Hz interval (TOT), in the VLF (.02-.04), LF (.04-.15) and HF (.15-.4) bands. Two-ways ANOVA and Bonferroni's post-test were used for statistical comparisons.

Results: 

BPs-TOT and BPs-LF were higher in H than in C during SB (10.7 6.9 vs 4.5 2.7 mmHg²·Hz^-1, p < .05; 5.8 3.9 vs 2.5 1.7, <.05), but not in PB. On the contrary, BPd-TOT and BPd-LF were higher in H than in C during PB (8.9 13.1 vs 3.8 3.7, <.05; 3.9 5.4 vs 1.8 1.6, <.05), but not in SB. The transition from SB to PB, significantly decreased and increased, respectively, the LF/(LF+HF) and HF/(LF+HF) ratios in both H and C subjects with respect to BPs, but only in H with respect to BPd.

Conclusion: 

Sympathetic tone is known to be higher in essential H subjects than in C. This agrees with a greater BPs variability in H than in C during SB, mainly in the LF band. On the contrary, BPd variability is about the same in H and C subjects during SB, but it is increased more in H than in C by the transition to PB. The concomitant relative changes in HF and LF bands, suggest that in SB and PB conditions different contributions occur of baroreflex to BPs and BPd short term variability.