The trigonometric regressive spectral analysis - a method for mapping of beat-to-beat recorded cardiovascular parameters on to frequency domain in comparison with Fourier transformation

Heart rate and peripheral blood pressure as physiological recorded vegetati ve parameters are very often rhythmically investigated with the Fourier Tra nsformation (FT). In contrast to the original use of FT these parameters an still stochastic with overlaying rhythmical structures. The R-R intervals as independent variables of rime are not equidistant. The mathematical stru cture for the spectral decomposition is critically analysed. The purpose of this article is the presentation of a mathematical method, considering bot h the statistical and rhythmical features of such time series. On the basis of trigonometric regressions, this method is presented to eliminate the eq uidistance problems, arising with the usage of FT, by a new mathematical ap proach. This method computes more precisely the spectral power especially i n the VLF range (0.003-0.04 Hz) than FT, because this method of trigonometr ic regression does not perform a frequency quantization. This method has be en used and successfully tested for the analysis of peripheral blood pressu re and R-R intervals including an effective reduction of input data. (C) 19 99 Elsevier Science Ireland Ltd. All rights reserved.