Vascular Variation of PTT and the Vascular Characteristic Index According to the Posture Change

The analysis of an arterial stiffness is essential for estimating the cardiovascular disease. Many indices suck as pulse transit time (PTT), reflection index (RI), stiffness index (ST) and characteristic impedance (Zc) are introduced to assess arterial stiffness. The purpose of this study is to analyze the variation aspect of PTT and the vascular characteristic index according to the posture change in the human body. The PTT is defined as the time interval between the peak of QRS complex in ECO and the characteristic point of the pulse wave. In this study, the characteristic point of the pulse wave is obtained using the maximum of the second derivative and peak point of PPQ signal, which is known to be noise resistant and to contribute a stable result. The vascular characteristic index was acquired through the analysis of waveform in peripheral pulse. The variation aspect of PTT and characteristic index according to the posture change were analyzed and the usefulness of those parameters was also evaluated. Experimental result indicated all parameters changed significantly according to the posture change. Therefore, proposed method can be an indispensable complement to existing methods for the non-invasive assessment of the vascular characteristics and body condition. It is possible to make ubiquitous healthcare monitoring because of simplicity, convenience and ease to access.