High resolution (HR) multi-electrode mapping is increasingly being used to evaluate gastrointestinal slow wave behaviors. To create the HR activation time (AT) maps from gastric serosal electrode recordings that quantify slow wave propagation, it is first necessary to identify the AT of each individual slow wave event. Identifying these ATs has been a time consuming task, because there has previously been no reliable automated detection method. We have developed an automated AT detection method termed falling-edge, variable threshold (FEVT) detection. It computes a detection signal transform to accentuate the high ‘energy’ content of the falling edges in the serosal recording, and uses a running median estimator of the noise to set the time-varying detection threshold. The FEVT method was optimized, validated, and compared to other potential algorithms using in vivo HR recordings from a porcine model. FEVT properly detects ATs in a wide range of waveforms, making its performance substantially superior to the other methods, especially for low signal-to-noise ratio (SNR) recordings. The algorithm offered a substantial time savings (>100 times) over manual-marking whilst achieving a highly satisfactory sensitivity (0.92) and positive-prediction value (0.89).

/pdf/falling-edge-variable-threshold-fevt-method-for-the-4vr0d2plfv.pdf

Falling-Edge, Variable Threshold (FEVT) Method for the Automated Detection of Gastric Slow Wave Events in High-Resolution Serosal Electrode Recordings

The bowel sounds of 21 patients with mechanical obstruction of the intestine were studied. A computer analysis of bowel sounds was performed using a signal processor. Bowel sounds of patients were classified into 3 types (Types I, II, and III) based on the histograms, although these were not distinguishable on auscultation. The lower, peak, and upper frequencies were 173 +/- 25 Hz, 273 +/- 64 Hz, and 667 +/- 58 Hz, respectively, in Type I; 309 +/- 121 Hz, 632 +/- 94 Hz, and 878 +/- 116 Hz, respectively, in Type II; and 330 +/- 120 Hz, 612 +/- 86 Hz, and 766 +/- 82 Hz, respectively, in Type III. High frequency sounds above 900 Hz were recorded in Types I and II but not in Type III. The ratio of the operated patients was 0, 23, and 100 percent in Types I, II, and III, respectively. The intervals between the times of admission and operation were 4.3 days and 1.2 days in Types II and III, respectively. Thus, it appears that the methods described by the authors could provide a very objective assessment of the severity and help determine the treatment (conservative or operative) of each patient.

Clinical application of spectral analysis of bowel sounds in intestinal obstruction

Background: Abdominal auscultation has an important position in the physical examination of the abdomen. Little is known about rater agreement. The aim of this study was to describe rater agreement...

Physicians' Abdominal Auscultation: A Multi-Rater Agreement Study

https://www.gastrojournal.org/article/S0016-5085(76)80202-8/pdf

The genesis of bowel sounds: influence of viscus and gastrointestinal content

Myoelectric recordings from the gastrointestinal (GI) tract in conscious animals have been limited in duration and site. Recently, we have implanted 24 electrodes and obtained electrograms from these sites simultaneously (200 Hz sampling rate; 1.1 MB/min data stream). An automated electrogram analysis was developed to process this large amount of data. Myoelectrical recordings from the GI tract often consist of slow wave deflections followed by one or more action potentials (=spike deflections) in the same traces. To analyze these signals, a first module separates the signal into one containing only slow waves and a second one containing only spikes. The timings of these waveforms were then detected, in real time, for all 24 electrograms, in a separate slow wave detection module and a separate spike-detection module. Basic statistics such as timing and amplitudes and the number of spikes per slow wave were performed and displayed on-line. In summary, with this online analysis, it is possible to study for long periods of time and under various experimental conditions major components of gastrointestinal motility.

Mapping slow waves and spikes in chronically instrumented conscious dogs: automated on-line electrogram analysis

Bowel sounds were recorded under standard conditions for 30 minutes before, and for 90 minutes after a standard meal in 12 healthy human volunteers. The sounds were analyzed with the aid of a computer, and the evolution in time of specific parameters obtained as a quantitative printout. The number, total duration, and mean energy of sounds totaled for ten minute periods were found to be markedly influenced by the ingestion of the meal. A peak of activity occurred immediately after the meal; the activity then decreased to 85% of premeal value 60 minutes later, and a second peak followed after a further 60 minutes. An excellent correlation (correlation coefficient better than 0.9) was found at two recording sites between the three analyzed parameters, taken in pairs. For any given parameter, a correlation was also found between its value at the two sites (k better than 0.9),but the actual value were significantly different (p <0.001). When bowel sounds are interpreted, therefore, food ingestion should be taken into consideration.

Postprandial Bowel Sounds

A computer system for quantitative analysis of gastrointestinal signals

An instrument has been developed to record simultaneously and continuously potential differences and impedance in the gastrointestinal tract The characteristics of the high-impedance differential amplifier limit the amount of flowing bioelectric current and reduce to a very small fraction the error introduced by changes in impedance, improving accuracy and repeatability of measurements Interruption of the circuit is seen plainly on the impedance recording, and thus artefacts in potential differences can be recognised Built-in filters ensure easily recordable low-noise analogue voltages as outputs for potential and impedance This instrument should prove useful in the study of potential differences in the gastrointestinal tract

Noel Van Houtte

Papers

Postprandial Bowel Sounds

A computer system for quantitative analysis of gastrointestinal signals

An improved instrument to record potential differences and impedance from the gastrointestinal tract.