Pinna G D, Maestri R, Sanarico M
Department of Biomedical Engineering, Salvatore Maugeri Foundation, IRCCS Medical Centre of Rehabilitation, Montescano (PV), Italy.
IEEE Trans Biomed Eng. 1996 Jul;43(7):754-7. doi: 10.1109/10.503184.
To evaluate the effects of record length selection on the accuracy of spectral estimates of heart rate variability (HRV), a simulation study was carried out using a set of 58 signals obtained by autoregressive (AR) fitting a representative sample of real HRV signals. Four record lengths of 180, 300, 420, and 540 s were considered. Spectral estimation was performed by both the Blackman-Tukey (B-T) and AR methods. Accuracy was assessed for: 1) point spectral estimates, by computing the normalized averaged bias (NAB) and variance (NAV); and 2) the most commonly used spectral parameters [total power (TP) and the powers in the bands: very low frequency (VLF) (0 divided by 0.04 Hz), low frequency (LF) (0.04 divided by 0.15 Hz), and high frequency (HF) (0.15 divided by 0.45 Hz)], by computing the normalized bias (NB) and variance (NV). The results are: whatever the record length considered, the 90th percentiles (90P) of the NAB were < 10%, whereas those of the NB were < 9% for TP, LF, and HF powers, and < 14% for the VLF power, in both methods. The NAV was proportional to the reciprocal of record length, showing high 90P values for the shortest record length (26.4% for B-T and 44.2% for AR). The NV showed the same trend but 90P values were much lower (< 8% for TP, LF, and HF powers and < 19% for VLF power, in both methods). In the final part of the paper a procedure for the computation of approximate upper bounds of the relative absolute error of spectral measures at each record length, based on the knowledge of the NB and NV, is presented.
为评估记录长度选择对心率变异性（HRV）频谱估计准确性的影响，使用通过自回归（AR）拟合真实HRV信号代表性样本得到的一组58个信号进行了模拟研究。考虑了180、300、420和540秒这四种记录长度。通过布莱克曼 - 图基（B - T）方法和AR方法进行频谱估计。针对以下方面评估准确性：1）点频谱估计，通过计算归一化平均偏差（NAB）和方差（NAV）；2）最常用的频谱参数[总功率（TP）以及频段功率：极低频（VLF）（0至0.04Hz）、低频（LF）（0.04至0.15Hz）和高频（HF）（0.15至0.45Hz）]，通过计算归一化偏差（NB）和方差（NV）。结果表明：无论考虑何种记录长度，在两种方法中，NAB的第90百分位数（90P）均<10%，而对于TP、LF和HF功率，NB的第90百分位数<9%，对于VLF功率，NB的第90百分位数<14%。NAV与记录长度的倒数成正比，对于最短记录长度显示出较高的90P值（B - T方法为26.4%，AR方法为44.2%）。NV呈现相同趋势，但90P值要低得多（两种方法中，对于TP、LF和HF功率<8%，对于VLF功率<19%）。在论文的最后部分，基于对NB和NV的了解，给出了一种计算每个记录长度下频谱测量相对绝对误差近似上限的程序。
