Affiliations: [a] Institute of Medical Statistics, Computer Sciences and Documentation, Medical Faculty of the Friedrich Schiller University Jena, Germany | [b] Hopitaux de Toulouse, CHU Rangueil, Angiologie, France | [c] CNR Institute of Clinical Physiology, Univ. di Pisa, Italy
Correspondence:
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Corresponding author: Prof. Dr Herbert Witte, Friedrich-Schiller-Universität Jena, Institut für Med. Statistik, Informatik und Dokumentation, Jahnstraße 3, D-07740 Jena, Germany. Tel.: 0049/3641 633 133; Fax: 0049/3641 633 200; E-mail: iew@imsid.uni-jena.de.
Note: [*] This study was supported by the CEC BIOMED I (CT920006).
Abstract: Time-variant AR-modelling was used to analyse the non-stationary properties of LDF signals during provocation tests. The procedure for the estimation of time-varying AR parameters based on Kalman filtering is presented. The estimates can be used to calculate instantaneous measures, such as peak frequency, spectral band power and coherence. The resulting course of instantaneous peak frequency of a sinusoidal signal with frequency jump was compared to similar parameters derived from short-time FFT and Hilbert transformation. Univariate time-variant spectral analysis was used to investigate LDF measurements in patients with Raynaud’s phenomena. The experimental protocol was splitted into phases of different room temperature. The results demonstrate time-dependent variations of spectral components (amplitude and frequency). By means of time-variant coherence analysis of LDF and diameter measurements of vessels in a hamster skin fold the existence of a main rhythm around 0.1 Hz in the LDF signals which is related to vasomotion is shown.
