IEEE Trans Biomed Eng. 2018 Jun;65(6):1226-1234. doi: 10.1109/TBME.2017.2710622.
N-point moving average (NPMA) is a simplified method of central aortic systolic pressure (CASP) estimation in comparison with the generalized transfer function (GTF). The fundamental difference or similarity between the methods is not established. This study investigates theoretical properties of NPMA relative to GTF and explores the integer and fractional denominator for the averaging process in the NPMA.
Convolution of a specified square wave and the radial (or brachial) blood pressure waveform constituted the NPMA . A single uniform tube model-based TF (MTF) was employed to investigate potential physiological meaning of NPMA. In experimental analysis, invasive, simultaneously recorded aortic and radial pressure waveforms were obtained in 62 subjects under control conditions and following nitroglycerin administration. CASP was estimated by NPMA (), GTF ( ), and MTF (CASP ) from radial waveforms by tenfold cross validation.
Theoretical analysis showed that NPMA was an inversed constant TF. Its spectrum matched that of MTF in low frequency (<4 Hz for radial and <5 Hz for brachial) by optimizing reflection coefficient and propagation time. Experiment results showed the NPMA optimized fractional denominator of K = 4.4 significantly decreased the mean difference between CASP and measured CASP to 0.0 ± 4.7 mmHg from -1.8 ± 4.6 mmHg for integer denominator of K = 4. CASP correlated with CASP and CASP (r = 0.99 and 0.97, mean difference: -0.3 ± 1.8 and 0.5 ± 2.7 mmHg).
This study demonstrated that NPMA is similar in nature to the GTF.
与广义传递函数（GTF）相比，N 点移动平均（NPMA）是一种简化的估算中心主动脉收缩压（CASP）的方法。这两种方法之间的基本差异或相似性尚未确定。本研究调查了 NPMA 相对于 GTF 的理论性质，并探讨了 NPMA 平均过程中的整数和分数分母。
指定方波与径向（或肱动脉）血压波形的卷积构成了 NPMA。采用基于单个均匀管模型的传递函数（MTF）来研究 NPMA 的潜在生理意义。在实验分析中，在 62 名受试者的对照条件下和给予硝化甘油后，同时获得了有创的、记录的主动脉和桡动脉压力波形。通过十倍交叉验证，从桡动脉波形中使用 NPMA（）、GTF（）和 MTF（CASP）估算 CASP。
理论分析表明，NPMA 是一个反常数传递函数。通过优化反射系数和传播时间，其频谱在低频（桡动脉<4 Hz，肱动脉<5 Hz）与 MTF 匹配。实验结果表明，NPMA 优化的分数分母 K=4.4 显著将 CASP 与实测 CASP 的平均差值从整数分母 K=4 的-1.8±4.6mmHg 降低至 0.0±4.7mmHg。CASP 与 CASP 和 CASP （r=0.99 和 0.97，平均差值：-0.3±1.8 和 0.5±2.7mmHg）相关。
本研究表明，NPMA 在性质上与 GTF 相似。
