Analysis of autonomous nerve response to tilt test by new HRV parameters

In this study, the parameters obtained from the impulse response function in the time domain are proposed as new pamameters for evaluation of HRV (heart rate variability). The impulse response function is estimated from the autoregressive model by which the R R interval time series is expressed. HRV during graded head-up tilt was analyzed using the parameters, ARV, TP, heart rate, CV(R-R), and a power spectrum density function. RII, power, time constant, and settling time were obtained from the impulse response function. The RHI is the summation of the impulse response function during the transient decreasing of the function. The power is the average value of the square of the impulse response function of the maximum settling time. The time constant is the time to reach the output value of the system when stimulation is input to 1/c or less. The settling time is the time for the value of the impulse response function to become .0.1 or less. ARV expresses the irregularity of the time series, TP evaluates the adjustment function of the system. The subjects were the healthy males aged 19 to 27 years old. The tilt angle was 0, 20, 30, 45, 60, 90, and 0 degrees, and it was changed, respectively, every four minutes. As a result, RH1, power and TP showed a high correlation between LF/HE, that is, the index of sympathetic nerve activity. ARV exhibited a high correlation between HF, that is, the index of the parasympathetic nerve. It was possible to analyze the autonomous nerve response by TP, ARV, RHI and the power of the impulse response function. With these parameters, the realization of a simple, portable autonomous nerve response analysis device targeting real-time, non-stationary data is expected.