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Handbook of Electrogastrography$
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Kenneth L. Koch and Robert M. Stern

Print publication date: 2003

Print ISBN-13: 9780195147889

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780195147889.001.0001

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Analysis of the Electrogastrogram

Analysis of the Electrogastrogram

(p.83) 5 Analysis of the Electrogastrogram
Handbook of Electrogastrography

Kenneth L. Koch

Robert M. Stern

Oxford University Press

The analysis of electrogastrogram (EGG) recordings involves an initial visual inspection of the signal to assess the quality of the signal, identification of artifacts, and selection of the minutes of EGG signal to analyze visually and by computer. This chapter discusses an approach to analyses of the EGG for clinical and research studies. All raw EGG recordings must be visually inspected to identify 3- cycles per minute (cpm) signals, gastric dysrhythmias, and any artifacts in the signal. Certain characteristics of the EGG can be determined and qualitative judgments can be made on the basis of visual inspection of an EGG record. Artifact-free minutes of the EGG signal must be selected for use in analyses that are generated by computer programs. When inspecting the EGG recording, there are several important questions to ask: 1. Is the baseline EGG recording rhythmic or dysrhythmic? 2. Are bradygastria, normal, or tachygastria frequencies identifible? 3. Is the amplitude of the EGG signal low, medium, or high? 4. After a provocative stimulus, does the EGG signal become more or less rhythmic? For example, Figure 5.1 shows a normal 3-cpm EGG signal that shifts to a tachygastria as the subject experienced nausea in a rotating optokinetic drum. Clinically relevant gastric dysrhythmias are persistent and last at least 3 to 5 minutes, usually much longer. 5. Is there a normal increase in the amplitude of the EGG after eating? Figure 5.2 shows an EGG recorded from a healthy subject before and after eating a test breakfast meal. Note the obvious increase in EGG amplitude at 3 cpm after the ingestion of food. 6. Are there artifacts in the EGG signal associated with movements of limbs or body or changes in respiration? Portions of the EGG recording with artifacts must be identified and not submitted for computer analysis; otherwise, erroneous data quantitative data will be generated. Thus, frequency and amplitude of the raw EGG signal during baseline and in response to the test stimulus should be first assessed visually. The visual inspection of the EGG record determines the general quality of the EGG signal and the presence of any artifacts.

Keywords:   Adaptive filtering, Bandpass filters, Fourier analysis, Leakage, Power ratio, Windowing

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