Identification of phase angle and Triglyceride-Glucose index as biomarkers for prediction and management of diabetic foot disease.

Introduction: Approximately 25 % of diabetic patients develop diabetic foot ulcers (DFUs), significantly increasing morbidity, mortality, and healthcare costs. Effective control and prevention are crucial. Objective: This study aims to identify easily measurable parameters for predicting DFU risk by assessing the correlation between Phase Angle (PA) and the Triglyceride-Glucose (TyG) index with DFU risk. Materials and methods: A comparative case-control study was conducted at the General Hospital of Elche from March to June 2023 with 70 participants (33 with diabetes, 37 without). Cases had diabetes for over five years and a diabetic foot risk grade of 0, 1, or 2 (IWGDF 2019). Exclusion criteria included inability to walk, prior use of orthoses, and severe complications like edema or wounds. Predictive variables were PA, TyG index, body composition, and biochemical markers. Statistical analyses included Pearson/Spearman tests for correlations, Student's t-test/Mann-Whitney test for group comparisons, and ANOVA/Kruskal-Wallis tests for normally and non-normally distributed variables. Results: PAand TyG index were strongly linked to diabetic foot risk, supporting their potential as biomarkers. Significant relationships with other relevant biomarkers were also confirmed. Conclusion: PA and TyG index are valuable, easily measurable biomarkers for assessing diabetic foot risk, and can be monitored in primary care settings. Implementing these biomarkers in routine practice could enhance the management of diabetic complications, particularly in resource-limited settings, by enabling early detection and intervention, thus improving patient outcomes and reducing the burden of advanced complications.

Combined method for reduction of high frequency interferences in surface electroenterogram (EEnG).

Surface electroenterogram (EEnG) recording is a novel technique for monitoring intestinal motility non-invasively. However, surface EEnG recordings are contaminated by cardiac activity, the respiratory artefact, movement artefacts and other types of interference. The goal of this work is to remove electrocardiogram (ECG) interference and movement artefacts from surface EEnG by means of a combined method of empirical mode decomposition and independent component analysis. For this purpose, 11 recording sessions were conducted on animal models. In order to quantify the effectiveness of the proposed method, several parameters were calculated from each session: signal-to-ECG interference ratio (S/I), energy over 2 Hz (EF2) which quantifies the intestinal motility index of external EEnG recording and the variation of EF2. The proposed method removes both ECG interference and movement artefacts from surface EEnG, obtaining a significantly higher S/I ratio and considerably reducing the non-physiological variation of EF2. Furthermore, after applying the combined method, the correlation coefficient between internal recording EF2 and surface recording EF2 rises significantly. The proposed method could therefore be a useful tool to reduce high frequency interference in EEnG recording and to provide more robust non-invasive intestinal motility indexes.

The detection of intestinal spike activity on surface electroenterograms.

Myoelectrical recording could provide an alternative technique for assessing intestinal motility, which is a topic of great interest in gastroenterology since many gastrointestinal disorders are associated with intestinal dysmotility. The pacemaker activity (slow wave, SW) of the electroenterogram (EEnG) has been detected in abdominal surface recordings, although the activity related to bowel contractions (spike bursts, SB) has to date only been detected in experimental models with artificially favored electrical conductivity. The aim of the present work was to assess the possibility of detecting SB activity in abdominal surface recordings under physiological conditions. For this purpose, 11 recording sessions of simultaneous internal and external myolectrical signals were conducted on conscious dogs. Signal analysis was carried out in the spectral domain. The results show that in periods of intestinal contractile activity, high-frequency components of EEnG signals can be detected on the abdominal surface in addition to SW activity. The energy between 2 and 20 Hz of the surface myoelectrical recording presented good correlation with the internal intestinal motility index (0.64 +/- 0.10 for channel 1 and 0.57 +/- 0.11 for channel 2). This suggests that SB activity can also be detected in canine surface EEnG recording.

Characterization of the sensitivity of a TCB laplacian sensor for surface EEnG recordings.

The improvement of the quality of electroenterogram (EEnG) recordings on abdominal surface could lead to a non-invasive technique to diagnose intestinal motility dysfunctions. In this context, the use of coaxial active electrodes, which permit to record the laplacian potential, can help to achieve such signal enhancement. In this paper, we present a methodology to obtain the maps of sensitivity of this kind of electrodes to pick up the activity of electric dipoles of different orientations. The proposed methodology employs mathematical models, as well as experimental studies (phantoms) to check the theoretical results. The mathematical model of the electrode, and of the human abdomen is developed by means of ANSYS. A simplified physical model is formed by real ring electrodes, a methacrylate tank of size 50 x 50 x 50 cm filled with a saltwater mixture of 2.5 g/l concentration, and moving electric dipoles made by wires of 0.3 mm in diameter. Sensitivity of the sensor is obtained for different depths and different axial distances of vertical and horizontal dipoles. Preliminary results of tripolar ring electrodes in bipolar configuration (TCB) are shown. The obtained results prove the agreement between mathematical and experimental results. The validated model will allow us to study the behavior of laplacian ring electrodes of different dimensions and materials to record the EEnG activity and to analyze the influence of the abdominal layers.

Enhancement of the non-invasive electroenterogram to identify intestinal pacemaker activity.

Surface recording of electroenterogram (EEnG) is a non-invasive method for monitoring intestinal myoelectrical activity. However, surface EEnG is seriously affected by a variety of interferences: cardiac activity, respiration, very low frequency components and movement artefacts. The aim of this study is to eliminate respiratory interference and very low frequency components from external EEnG recording by means of empirical mode decomposition (EMD), so as to obtain more robust indicators of intestinal pacemaker activity from the external EEnG signal. For this purpose, 11 recording sessions were performed in an animal model under fasting conditions and in each individual session the myoelectrical signal was recorded simultaneously in the intestinal serosa and the external abdominal surface in physiological states. Various parameters have been proposed for evaluating the efficacy of the method in reducing interferences: the signal-to-interference ratio (S/I ratio), attenuation of the target and interference signals, the normal slow wave percentage and the stability of the dominant frequency (DF) of the signal. The results show that the S/I ratio of the processed signals is significantly greater than the original values (9.66 +/- 4.44 dB versus 1.23 +/- 5.13 dB), while the target signal was barely attenuated (-0.63 +/- 1.02 dB). The application of the EMD method also increased the percentage of the normal slow wave to 100% in each individual session and enabled the stability of the DF of the external signal to be increased considerably. Furthermore, the variation coefficient of the DF derived from the external processed signals is comparable to the coefficient obtained using internal recordings. Therefore, the EMD method could be a very useful tool to improve the quality of external EEnG recording in the low frequency range and therefore to obtain more robust indicators of the intestinal pacemaker activity from non-invasive EEnG recordings.

Quantification of combined method for interferences reduction in multichannel surface electroenterogram.

Surface electroenterogram (EEnG) is a non-invasive method for monitoring the intestinal motility. However, surface EEnG signals are contaminated by strong physiological interferences. The main interferences which affect high-frequency components of surface EEnG are cardiac activity and movement artifacts. The aim of this work is to quantify the effectiveness of a combined method based on empirical mode decomposition and independent component analysis to remove these interferences from multichannel surface EEnG. In order to do so, several parameters were calculated from five recording sessions: Signal-to-ECG interference ratio (S/I) and variation of energy over 2 Hz (EF2). The results show that the S/I of processed signals was significantly higher than that of original signals, moreover the improvement of the S/I ratio is due to the attenuation of energy associated to interference. The proposed method also allows cancelling movement artifacts from surface EEnG, reducing considerably the non-physiological variation of EF2. Furthermore after the application of the combined method, correlation coefficient between EF2 of internal recording with EF2 of surface recording is greatly higher. Therefore, the proposed method could be helpful to reduce high-frequency interferences in EEnG recording and to provide more robust non-invasive intestinal motility indicators.

Combined method for artifact reduction in surface electroenterogram.

Surface electroenterogram (EEnG) is a non-invasive method for monitoring the intestinal motility. However, surface EEnG recordings are contaminated by movement artifact, cardiac activity, respiratory artifact and other interferences. The aim of this work is to remove movement artifacts by means of a combined method of empirical mode decomposition (EMD) and independent component analysis (ICA). Four recording sessions were conducted on canine model. Surface signals from 4 different channels are decomposed using EMD. Resulting intrinsic mode functions are the inputs of ICA analysis which permits to separate and identify the activities of different origin. Signal components associated to movement artifacts are removed and the original signals are reconstructed by means of an inverse procedure. The results show that the proposed method allows extracting and cancelling movement artifacts from surface EEnG, avoiding the presence of irregular peaks in external intestinal motility indexes. Therefore, the proposed method could be useful to reduce artifacts in EEnG recording and to provide more robust non-invasive intestinal motility indicators.

Empirical mode decomposition: a method to reduce low frequency interferences from surface electroenterogram.

The surface electroenterogram (EEnG) is a non-invasive method of studying myoelectrical bowel activity. However, surface EEnG recordings are contaminated by cardiac activity, respiratory and motion artifacts, and other sources of interference. The aim of this work is to remove the respiration artifact and the very low frequency components from surface EEnG by means of empirical mode decomposition (EMD). Eleven recording sessions were carried out on canine model. Several parameters were calculated before and after the application of the method: signal-to-interference ratio (S/I ratio) and the attenuation level of the signal and of interference. The results show that the S/I ratio was significantly higher after the application of the method (3.68+/-5.54 dB vs. 10.45+/-3.65 dB), the attenuation level of signal and of interference is -0.49+/-0.80 dB versus -7.26+/-5.42 dB, respectively. Therefore, EMD could be a useful aid in identifying the intestinal slow wave and in removing interferences from EEnG recordings.

Identification of the slow wave of bowel myoelectrical surface recording by empirical mode decomposition.

Surface electroenterogram (EEnG) is a non-invasive method to study bowel myoelectrical activity. Nevertheless, surface recorded EEnG is contaminated by respiratory, motion artifacts, and other interferences. The goal of this paper is to remove the respiration artifact and ultra-low frequency components from surface EEnG by means of empirical mode decomposition (EMD). Seven recording sessions on abdominal surface of three Beagle dogs were conducted. Power percentages of interferences and of fundamental slow wave were calculated before and after the application of the method. The results show that the interference power is significantly reduced (23 +/- 16% vs. 5 +/- 4%), and fundamental slow wave power is significantly increased (59 +/- 17% vs. 76 +/- 13%). Therefore, the EMD method can be helpful to remove respiration and ultra-low frequency components from the external EEnG recordings.

Stationarity study of the myoelectrical signal recorded from small bowel.

Electroenterogram (EEnG) is the myoelectrical signal recorded from small intestine. Due to the relationship between mechanical activity and myoelectrical activity of the intestinal smooth muscle, EEnG could be a solution for quantifying intestinal motility. Motility indexes are traditionally calculated from 1-minute window analysis. However, no prior works have analyzed whether signal properties remain constant or not within this time interval. The aim of present paper is to study time evolution of changes in EEnG spectrum in order to determine if traditional analysis and window length is satisfactory from the signal dynamics point of view. Mechanical and electrical activities are recorded simultaneously in bowel rings (at duodenum, angle of Treitz and jejunum) of three Beagle dogs. Thirteen recording sessions were carried out. A stationary index (SI) based on statistical analysis of time evolution of spectral parameters is defined and calculated over EEnG recording sessions. Results show that myoelectrical signal from bowel muscle is stationary during quiescence periods and maximum contractions periods. However, during irregular contractile activity (i.e. transitions from no-activity to maximum activity, or in fed state) electroenterogram is a non-stationary signal if 1-minute length is chosen for its analysis. Therefore, traditional intestinal motility indexes must be redefined using non-stationary techniques.

Relation between the bowel electromyogram and the intestinal pressure wave. An experimental study in dogs.

OBJECTIVE: A linear regression study is made of the parameters identifying the electrical activity of the small bowel, with the aim of determining those variables most closely related to the type I pressure waves. PATIENTS AND METHODS: A computer system was used for the simultaneous and real time acquisition of the manometric activity (using microballoons implanted in the bowel mucosa) and electromyogram of the intestine (employing bipolar electrodes implanted in the intestinal serosa) in dogs. RESULTS: Of the electromyogram intestinal parameters studied, those determining signal energy (root mean square voltage and energy) yielded the highest correlation coefficients (0.71 +/- 0.08 in the jejunum and 0.78 +/- 0.06 in the duodenum) to bowel pressure. Peak-to-peak voltage also shows good correlation, though to a lesser degree. The rest of the parameters studied, such as those that measure the duration of the action potential or its number of peaks, yielded poor correlations to pressure. CONCLUSIONS: It is concluded that the energy of the intestinal electromyogram represents the mechanical activity of the small bowel, reflecting intestinal motility, and that the recording of this parameter is not subjected to subjective cutoff values or threshold levels. On the other hand, and unlike in the case of manometric recordings, the signal obtained is free of background interference and noise.

Small bowel motility: relationship between smooth muscle contraction and electroenterogram signal.

A study is made to correlate the electrical and mechanical activity of the smooth muscle of the small bowel. Bioelectrical signal recording from the intestinal serosa (electroenterogram) comprises a slow wave (SW) and spike burst (SB), though only the latter reflects intestinal pressure. The electroenterogram and smooth muscle pressure are simultaneously recorded in the canine small bowel. Spectral and time series analysis of the electroenterogram are performed to establish those electrical parameters that best reflect intestinal pressure. The results reveal an underlying correlation between the estimated parameters of electrical activity and smooth muscle pressure. In addition, parameters derived from the spectral techniques were closely correlated to pressure events in the intestine, even more so than the variables directly acquired from the classical time domain analyses. Specifically, spectral energy above 2 Hz and mean frequency (both calculated from the biosignal periodogram), are parameters that identify intestinal pressure. The extrapolation of these spectral parameters to long time periods could serve to define a motility index (MI) from electrical gut activity. In this context, electroenterogram recording and analysis can contribute to solve problems inherent to manometric recording, though the need for surgical intervention restricts electrical methods to experimental or surgical studies.