Noninvasive tracking of peripheral resistance by ear densitography

Owing to the interaction between the left ventricle and the arterial system, pulse contour during ejection is significantly affected by changes in peripheral resistance. Quantitative description of the pulse configuration as a function of peripheral resistance involves invasive investigation of complex frequency and impedance spectra. The ear densitogram noninvasively yields a pulse wave shown to closely track changes in the central arterial pulse; in this investigation, its decreasing systolic slope responded to changes in the peripheral resistance like those in the central pulse and in arterial models. The decreasing slope of the ear densitogram pulse (RNAD) can reliably track changes in peripheral resistance.