Submitted on December 8, 2004
Accepted on May 10, 2006
Wavelet analysis of scaling properties of gastric electrical activity
Bruce J West1*, Artur Maciejewski2, Miroslaw Latka2, Tadeusz Sebzda3, Zbigniew Swierczynski4, Sylwia Cybulska-Okolow5, and Eugeniusz Baran5
1 Mathematical & Information Science Directorate, Army Research Office, Research Triangle Park, North Carolina, United States
2 Institute of Physics, Wroclaw University of Technology, Wroclaw, Poland
3 Department of Pathophysiology, Wroclaw Medical University, Wroclaw, Poland
4 4Department of Electronic and Photonic Metrology, Wroclaw University of Technology, Wroclaw, Poland
5 Dermatology,Venerology and Allergology, Wroclaw University of Medicine, Wroclaw, Poland
* To whom correspondence should be addressed. E-mail: bruce.j.west{at}us.army.mil.
We present a novel approach to the analysis of fluctuations in human myoelectrical gastric activity measured noninvasively from the surface of the abdomen. The time intervals between successive maxima of the wavelet transformed quasi-periodic electrogastrographic (EGG) waveform define the gastric rate variability (GRV) time series. Using the method of average wavelet coefficients (AWC) the statistical fluctuations in the GRV signal in healthy individuals are determined to scale in time. Such scaling was previously found in a variety of physiologic phenomena, all of which support the hypothesis that physiologic dynamics utilize fractal time series. We determine the scaling index in a cohort of 17 healthy individuals to be 0.80 [plusmn] 0.14, which when compared to a set of surrogate data is found to be significant at the level p < 0.01. We also determined the dynamical pattern, so evident in the spectrum of AWC of the GRV time series of healthy individuals, is significantly reduced in a cohort of systemic sclerosis patients having a scaling index 0.64 [plusmn] 0.17. These results imply that the long-term memory in GRV time series is significantly reduced from healthy individuals to those with systemic sclerosis. Consequently, this disease degrades the complexity of the underlying gastrointestinal control system and this degradation is manifest in the loss of scaling in the GRV time series.
