P1.12 Comparison of Arterial Relaxation Time in Normotensive and Hypertensive Subjects

Abstract

Arterial stiffening is emerging as an important determinant of increased systolic blood pressure (SBP) and pulse pressure in the aging population. The relation of the brachial artery was studied in both normotensive and hypertensive volunteers. The test subjects include six healthy, normotensive (SBP/DBP < 120/80 mm Hg) subjects (control group, four in the age range 19 to 23 years, and two in the older subjects, 57 and 60 years) and four subjects (48 to 58 years) with elevated SBP (ranging from 130–168 mm Hg) and who are currently on hypertensive medications (hypertensive group). Temporal measurements of the pressure and volume waveforms were recorded in both hands with one arm at heart level and the other initially at heart level and then raised a distance of 35 cm above heart level. Upon raising the arm, a delay is observed in the pulse measurement of the raised arm relative to the hand at heart level. The delay has previously been shown to decay exponentially with time. For the normotensive subjects, the average values of the pressure and volume relaxation times τ_P and τ_V were 75 s and 41 s for the younger-age group and 86 s and 68 s for the older-age group. The delay times for subjects in the hypertensive group were assumed to approach the baseline asymptotically. The validity of this assumption has been demonstrated in the control group. The average value of τ_P in the hypertensive group was found to be 581 s, significantly larger than the control group.