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# proefschrift gommer inhoud met kaft.indd

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.
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