Chapter 2 function analysis when instead of the beat-to-beat ABP and CBFV signals, the intrinsic mode functions of the MMPF were used. Statistical analysis The non-parametric Wilcoxon-signed rank test was used to test for left/right and morning/afternoon differences for each method. Reproducibility was quantified by the intraclass correlation coefficient (ICC) using the generalisability theory 8, 28. ICC, defined as the sum of variances except for repeated measurements components divided by the total variance, was calculated 25 using the GENOVA (version 2.2, 1984) program. Although ICC is specific to the population studied, it does give clear indications of inter-method reproducibility being a major purpose of this study. Results Spontaneous blood pressure variations From all recorded data (19 subjects*2 sessions *1 hour = 39 hours) only a single period of 20 minutes had to be excluded because of bad signal quality. Pair wise comparison of coherence, gain and phase parameters between left and right CBFV recordings did not reveal significant differences. Therefore, per individual and recording session left and right side data were pooled for further analysis. Morning and afternoon dCA parameters for the four analysis methods are given in the supplemental material (table S1). MMPF results are presented for intrinsic mode functions 3 and 4. The mean frequencies of ABP and CBFV for these components 3 and 4 and their standard deviations are indicative for narrow- banded signals. Also the frequencies of intrinsic mode functions 3 and 4 match very well for ABP and CBFV. 26
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