Advances in Medical Sciences br Fig
Advances in Medical Sciences 64 (2019) 44–53
Fig. 1. Placement of electrodes for registering a multichannel electro-gastrogram on the abdominal skin: 1–4 - active electrodes, Ref - reference electrode, Gnd - grounding electrode (according to operating manual).
and remove any fragments containing motion artefacts . Three al-gorithms were then applied to analyze the multichannel electro-gastrograms:
1) A running spectrum analysis (RSA) that involved an auto-regressive moving average approach executed on consecutive 60-s data sets. The percentage EGG classification ranges were defined as 1.8–2.0 cpm for bradygastria, 2.0–4.0 cpm for normogastria, 4.0–9.0 for ta-chygastria. A default value of 2.5 dB for the classification threshold was assumed. This stage of analysis yielded the following parameters for each of the four registration 3X FLAG within a given period: (a) the relative time share of normogastria (3CPM), (b) the share of the power within the normogastria range relative to the total power of the whole considered frequency band;
2) For the overall spectrum analysis a fast Fourier transform using a Hamming window was run on consecutive 256-s data sets with a 128-s overlap. Subsequently, the meal-induced change in DP is compared to the fasted situation.
3) A cross-channel analysis was accomplished using the VAIVA Propalyzer module12 to derive: (a) the percentage of slow wave cou-pling defined as the relative time within a given period during which the difference in DF between two channels is < 0.2 cpm; averaging the results pertaining to six possible channel pairs yielded the average percentage of slow wave coupling (ACSWC) . EGG recordings were taken to analysis from 1 or 2 channel in patients with gastric cancer after subtotal gastrectomy, in other investigated groups – from 3 channel [27,28].
The definition of normal and abnormal gastric myoelectical activity was based on the validation proposed by Yin et al. . The abnormal response of the EGG to a test meal was defined as a lack of increase in the EGG DP. Changes in the EGG DP were reflected by gastric con-tractility [1,2]. Gastric myoelectric activity is combined of slow waves associated with electric response activity . The frequency of normal gastric slow waves (normogastria) corresponds to approximately 3 (2–4) cmp; normal gastric slow waves represent > 70% of the EGG percentage time of the normogastria [2,15]. The list of potential de-viations from normogastria includes gastric dysrhythmias (bradygas-tria, tachygastria and arrhythmia), electro-mechanical uncoupling and abnormal slow wave propagation [10,15,29].
2.1.2. Assessment of GI dyspeptic symptoms
All patients completed a self-administered survey (Appendix 1 in supplementary material) on subjective presence and severity of ten dyspeptic symptoms: epigastric pain, abdominal discomfort, heartburn, regurgitation, early fullness, feeling of food retention in the stomach, epigastric bloating, nausea, vomiting, and loss of appetite. The severity of each symptom was scored from to 5 points (0 – absent, 1 –
Fig. 2. Recording of the overall spectrum of EGG from 3 channels (EGG 3) and 4 channels (EGG 4): preprandial (green line) and postprandial recording (yellow line). Patients with gastric cancer (A) – abnormal (irregular) rhythm of gastric slow wave, without dominant frequency (DF) peaks, control subject (B) – normal rhythm of gastric slow wave, peaks of dominant frequency (DF) in area 2–4 cycle per minute (cpm), increase of dominant power (DP) after meal.
2.2. Assessment of autonomic system activity
Autonomic function was determined on the basis of HRV deriving from sinus rhythm. The measurements were taken in the morning (between 8:00 and 10:00 AM), after an overnight (12-h) fast, with the subject in a supine position. Prior to the examination, the participants were provided with detailed information on the testing procedure. Furthermore, we verified if they were in a stable clinical status, re-frained from drinking coffee and strenuous physical exercise, and did not take medications with potential modulatory effect on autonomic activity within 72 h prior to the testing .
After a 20-min rest and achieving respiratory rate of 14 breaths/ min, 30-min ECG recordings simultaneously to the preprandial period of EGG were obtained from 4 conventional leads with Task Force® Monitor 3040i (CNSystems, Austria). The Task Force® Monitor 3040i uses the bipolar principles of EINTHOVEN I and EINTHOVEN II. A 2 channel ECG is included for RR-interval evaluation. These biosignals are recorded in 16bit resolution with a maximum sampling frequency of 1000 Hz. After manual edition of electrocardiograms for potential ar-tifacts, the results were analyzed with Task Force Monitor V2.2 soft-ware. Frequency domain analysis of HRV was conducted based on the Aggregating Algorithm Regression (AAR). The following frequency domain HRV analysis parameters were analyzed: power spectral density (PSD) or total power (TP) of the spectrum at 0.0033-0.4 Hz, very low frequency (VLF) component at 0.0033-0.04 Hz – reflecting HRV modulated by chemoreceptors of the renin – angiotensin – aldosterone system (RAA), low frequency (LF) component at 0.04-0.15 Hz – re-flecting HRV modulated by the sympathetic system, associated with cyclic changes in the arterial blood pressure and depending on baror-eceptors’ activity, high frequency (HF) component at 0.15-0.4 Hz – re-flecting HRV controlled by the parasympathetic system, associated with breathing, low frequency to high frequency component ratio (LF/HF) - a measure of the relationship between the two components of vegeta-tive modulation, and normalized components, LFnu [LF/(TP-VLF)*100] and HFnu [HF/(TP-VLF)*100] .