Abstract
We have developed a method, based on the oscillometric method for indirectly measuring blood pressure, that determines an arterial stiffness index (ASI). The method quantifies the stiffness of the intima and tunica media of the arterial segment. We provide a theory for the ASI measurement with the experimental data. The mechanism of occurrence of the change in the amplitude of pulsation during the blood pressure measurement using oscillometric method can be elucidated on the non-linear Pressure-Volume (P-V) curve of the artery. The properties of the tunica media and the outer membrane makes a non-linear P-V relation. Thus, the amplitude of arterial volume pulsation is varied with transmural pressure which is the difference between arterial pressure and cuff pressure. The property of the artery with stiff tunica media makes a flat-topped graphical pattern of amplitudes of arterial volume variations and that for the normal artery produce a sharp-peaked pattern. The width of a flat-topped pattern was calculated so as to produce the ASI. We have experimentally evaluated this theory using rabbit artery. The right carotid artery was subjected to pressure sufficient to cause occlusion several times, damaging the endothelial cells, while the left carotid artery was left intact. After feeding the rabbits a diet including 5% cholesterol for 6 weeks, the P-V relations in both segments were measured. The results strongly supported the theory for the indirect measurement of ASI. [Jpn J Physiol 55 Suppl:S104 (2005)]
