Systolic and diastolic blood pressure (BP) changes over different mean pressure levels has been used to generate the (ambulatory) arterial stiffness index, and may reflect functional arterial properties. We hypothesized that pressure changes obtained by changing arm position may represent a tool to investigate arterial function at bedside.

In 56 healthy subjects (age 48±18 years, BP 125/71±18/10 mmHg), we measured carotid-radial pulse wave velocity (PWV) and sitting brachial BP (12 readings with the arm in 4 different positions, 3 readings per position). SBP-on-DBP slope, estimated by the ratio of their standard deviations, was defined as BPVR (BP variability ratio). Recent model expresses BPVR as the systolic-to-diastolic stiffness ratio. Diastolic stiffness was expressed by PWV² (Bramwell-Hill formula).

As expected from Stevin’s law, mean pressure changed linearly with the cuff-heart vertical distance (−14 mmHg, −8 mmHg, and +9 mmHg, respectively, at +20, +10 and −15 cm; p for linear trend <0.001). Diastolic PWV² had a linear relationship with DBP (r=0.40, p=0.005). Also, calculated systolic stiffness (BPVR × diastolic PWV²) had a direct relationship with SBP (r=0.60, p<0.05). BPVR had no relation with PWV² (r=−0.18, p=n.s.), and a strong one with age (r=0.45, p<0.01) and Framingham coronary risk (r=0.60, p<0.001).

In conclusion, SBP/DBP changes at different arm heights may provide a novel measure of arterial function. The resulting SBP-on-DBP slope had no correlation with diastolic arterial stiffness, and increased with increasing SBP, age and estimated coronary risk. Results support the theoretical expression of SBP-on-DBP slope as the ratio between systolic and diastolic stiffnesses.