On line display of the reconstructed pressure waves of the radial artery from the monitored output pressure waves at the same site

: The input-output relationship of transducer and catheter system is described by linear, second-order differential equation with three coefficients: inductance (L), resistance (R), and capacitance (C). Once the natural frequency (fo) and the damping ratio (beta) of the monitoring system have been measured, three coefficients of the differential equation are uniquely obtained. We measured the frequency response of the monitoring system, which we usually use in our hospital, to obtain fo and beta, and reconstructed the original input arterial pressure wave from output signal on the display using the simple time-domain approach. The analysis of this linear, second-order differential equation, is applicable in on-line bedside monitoring, because the calculation of this equation is simpler than that using Fourier's translation. The pressure waves of the radial artery both monitored (output) and restored (input) were depicted on the same display at the same time. We can evaluate the changes in systemic circulation from the changes in the wave shapes of arterial blood pressure.