Computer-aided analysis of gastrointestinal myoelectric activity

COMPUTER-AIDED ANALYSIS OF GASTROINTESTINAL MYOELECTRIC ACTIVITY A. Latour

and

J.P. Ferrb

ABSTRACT

phases of regular spike activity are recognized during the interdigestive periods. The system has been used in a series of comparative measurements of duodenal activity before and after feeding, and in studies involving drug-induced regular spike activity.

This method of analysing gastrointestinal motility involves data collection fir 12 h periods and calculations from electromyographic signals at I 5 s intervals; results are printed for successive 20 min epochs. In addition, Keywords:

Signal processing,

EMG automatic

processing,

parameters

extraction

INTRODUCTION Electrical activity in the antrum and small intestine is of two kinds: a slow periodic wave considered to be a pace-setter potential, and a nonperiodic spike burst which is intermittently superimposed on the slow wave and associated with muscular contraction. The two components may be separated in most instances by active low-pass and high-pass filters. A commonly used method for the quantification of contractile activity is a manual tabulation of the percentage of slow waves associated with spike bursts within a specified period; interpretation of data by this method is both subjective and very time consuming. Latour’ has developed a novel approach to the quantification of spike activity over a selected period; he uses simple integration after high pass filtering and half-wave rectification to quantify the summated amplitude of spike activity for 15 s periods. Between each period the integrator timer is reset. An additional circuit was used in studies of the canine antrum where slow waves having a high amplitude are accompnied by high frequency components which cannot be removed by filtering. To circumvent this problem, a circuit was developed to detect slow wave activity and pass it to the integrator for a specific period after a short delay (a time window) following each slow wave2. A different technique was developed for the quantification of colonic spike activity; the signals were digitized at 2 samples/s and a threshold calculated every 5 min (600 samples) so as to minimize the effect of artifacts. The upper threshold values were used to recognize the two classes of motor events3. Summated myoelectric activity of the small intestine clearly demonstrates migrating myoelectric Laboratoire de Physiologic, Capelks, 31076 Toulouse

kale Nationale CCdex, France

@ 1985 Butterworth & Co (Publishers) 0141-5425/85/020127-05 SO3.00

Veterinaire,

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complexes which consist of a phase of irregular spike activity (ISA) followed by a phase of regular spike activity (RSA), and terminating in a quiescent phase; the complexes recur at 15 min intervals in the rat? and 40 to 120 min intervals in other species6. Calculation of the percentage of slow waves with superimposed spike bursts’, or counting spike bursts greater than a given amplitude after pulse production by Schmidt triggers and pulse shaping circuitPO, produces similar results. A more detailed analysis can be obtained by measuring amplitude, duration, average upward slope and velocity of the propagated signal, or by the use of flexible threshold parameters set in trial replays of signals recorded on magnetic tape”. In order to conserve computer memory, filters external to the computer were used recently instead of digital filtration’*. / Precise quantification of myoelectric activity during the continuous motor pattern associated with feeding (feeding pattern) and recognition of RSA phases during the interdigestive period (fasting pattern) is of great informative value and reflects the intestinal motility index when signals are analysed from at least two electrode sites. In species such as the rat, where the duration of the RSA phase and subsequent quiescent phase is often less than 4 min, summated electromyographic activity is well correlated with the index of motility determined by means of extraluminal strain gaugesi3. The aim of this paper is to describe a system which first measures myoelectric activity at 15 s intervals from 8 electrode sitesi (and permits the recognition of the RSA phases), and then analyses data from 8 electromyogram recordings for 12 h periods in order to provide an index of both spontaneous and induced motility changes. METHODS The computing

system (Figure I) consists of an

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Myoelecttical activity analysis: A. L&our and J.l? Fe&

Apple IIe with an eight-channel Analogue/Digital converter (Progetec ADC 8 B 100 M), four Digital/ Analogue converters (Progetec DAC 12b-4 V), a real time clock (Mountain computer) and two floppy disks. A line printer and a xy plotter were used for the off-line display of data.

l-l EEG

MACHINE

Data collection The myoelectric activity of the rat small bowel was recorded from chronically implanted electrodes14 and amplified by an EEG machine (ALVAR, Mini VIII) with a time constant of 0.1 s. These electrical signals were summed by an eight-channel integrator with a reset every 15 s. (Figure 2, 0). This approach produced a graphic display as a function of time. Before resetting, the integrated value for each channel was determined and stored. All these values were then transferred to disk at 30 min intervals. After collecting data for 12 h, the integrator was reset by the internal timer (Figtlre 2, I)

Block diagram of data collection from 8 channels of Figure 1 an EEG machine. Values are printed at 20 min intervals and the 12 h recording is transferred to a x y plotter

Event marker. During data collection, switches were used to signal events (Figure 4; these switches utilized inputs PDL O-3 of the I/O connector, each controlled a pair of channels since a correct representation of the motor profile can be obtained in a rat only from two electrode sites 10 cm apart on the duodenojejunum.

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Myoelectrical activity analysis: A. L&our and J. I? Fer&

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bits) and the gain of the integrator was adjusted for 0 - 127 A/D converter output. To distinguish the RSA phase from an ISA phase, or quiescence, the 15 s integrated values were expanded according to the formula E = exp (E/5); the program was automatically truncated to 128 all higher values. Detection of the RSA phase required the recognition of a series of six 15 s values greater than the threshold (128) followed by a minimum of 6 consecutive 155 values lower than the same threshold. The number of RSA occuring during each 20 min period was printed. Figure 4 demonstrates that recognition of the RSA phases was in agreement with the integrated record in all instances but one. The reliability of this method has been tested in species other than the rat, in the duodenum and jejunum of the pig, sheep and dog. For the latter species, the special circuit eliminating slow waves must be included*. In all cases, the method provides accurate results comparable with manual measurements and plotting the results.

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Event marker operated by four switches. Each Figure 3 switch is linked to the pair of channels representing two electrode sites of the same animal

Treatment

of data and RSA detection DISCUSSION

The numerical values for each 15 s interval were summed to give a total for each 20 min period. The 20 min periods before and after an event, such as a meal or an injection of a pharmacological agent, gave an index which was in agreement with periods of shorter duration (5, 10 or 15 min).

Simple analysis of electrical spike activity with a 3 stage RC amplifier, high-pass filtering of slow waves and a linear integrator over 15 s intervalsllZ produces a useful graphical display but is of limited quantitative value. The computer record described here offers a similar display (Figure 5) and, in addition, yields an index of motility for a fixed time interval. Comparison of the motility index for intervals of 20 min with shorter intervals of I-10 min during motility changes induced by feeding suggests that the information derived from data obtained at 20 min intervals was of greater value. More detailed patterns from data derived from shorter time intervals is less informative than the present method when the overall changes occuring during 6-8 h are assessed. More precisely, duodenal motility index calculated for 10 periods of 1 min was 3.6 f 3.1 (mean f SE) before and

The RSA in rats has a duration of 1.8-4.5 min and is followed by a quiescent period of at least 3 min (F&w~ 4, integrated record). In other species, the duration is 5 - 7 min and the period of quiescence varies from 2 to 20 min. Detection of the RSA phase consisted of a comparison of values, after D/A conversion, with the user-defined threshold for each 15 s squared data sample; if exceeded, this sample was taken to be the beginning of an RSA phase. The output converter values were in the range 0 - 127 (7 INTEGRATED

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Myoelectrical activity analysis: A. L&our and J. I? Fe&

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Figure 6 Analysis of the effects (a) of the cerebroventricular administration of an enkephalin pentapeptide (DADLE) and (b) of the subcutaneous administration of morphine in a fed rat It is obvious that the ‘fasting pattern’ of electrical activity induced 100 min after the administration of DADLE or 6 h after that of morphine, corresponded to a lower level of duodenal motility

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Myoelectncal actiuity analysis: A. Latour and J.I? Ferri

8.7 f 2.9 after feeding in the rati3. Figure 5 depicts that after feeding, the highest values occurred 20 60 min following access to food.

The detection of RSA phases concomitantly with the index motility provides an interesting comparison of drug actions. For example, the cerebroventricular injection of enkephalins in the fed rat is followed within 35-40 min by a ‘fasted pattern’. Our processing data analysis indicated that after n-Ala-n-Leu-enkephalin (DADLE) injection, the values during 20 min periods are of the same order as those seen during the interdigestive periods (Figure 6). In contrast, the values for the RSA-like pattern recorded about 6 h after the injection of morphine are relatively low.

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ACKNOWLEDGEMENTS Our work is primarily supported by C.N.RS. (A. Latour) as an individual aid to Prof. Y. Ruckebusch

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REFERENCES Latour, A. Un dispositif simple d’analyse quantitative de l’electro-myogramme intestinal chronique. Ann Rech vitir. 1973,4, 347-353 Latour, A. Quantitative analysis and measurement of myoelectrical spike activity at the gastroduodenal junction. Ann Bio. Anim Bioch Biophys. 1978, 18, 7 1 I-716 Latour, A., Bueno, L and Fioramonti, J. Quantitative measurement of human colonic electrical activity by a micro-computerized system. Int. J. Bio-Med Cornput. 1983, 14, 7-16

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Ruckebusch, M. and Fioramonti, J. Electrical spiking activity and propulsion in small intestine in fed and fasted rats. Gastroenterology 1975, 68, 1500-1508 Wright, J.W., Healy, T.E.J., Balfour, T.W. and Hardcastle, J.D. A method for long-term recording of intestinal mechanical and electrical activity in the unrestrained rat. J Pharmac. Meth. 1981, 6, 233-242 Ruckebusch, Y. Motor functions of the intestine. Adu. Vet. Sci Camp. Med, 198 1, 25, 345-369 Freinkel, W.D. and Hinder, RA. Recording the interdigesive myoelectrical complex. A new technique. S. Afx Med. J. 1980, 58, 238-240 Wingate, D.L., Barnett, T.G., Green, W.E.R. and Armstrong-James, M. Automated high-speed analysis of gastrointestinal myoelectric activity. Amer. J Dig. Dis. 1977, 22, 243-251 Wingate, D.L. and Barnett, T. The logical analysis of the electro-enterogram. Amer. J. Dig. Dis. 1978, 23, 553-558 Hutton, M.RE. and Wingate, D.L. A method for recording intestinal myoelectric activity in the conscious rat J. Physiol (Lond), 1980, 313, 25-26P Summers, R.W., Cramer, J. and Flatt, A.J. Computerized analysis of spike burst activity in the small intestine. IEEE Trans. Biomed Eng 1982, 29 (5), 309-314 Groh, W.J., Takahashi, I., Sarna, S., Dodds, W.J. and Hogan, W.J. Computerized analysis of spike-burst activity of the upper gastrointestinal tract. Dig Dis. Sci 1984, 29, 422-426 Ruckebusch, Y. and Brady, C.J. Recording and analysis of electrical and mechanical activity of the gastrointestinal tract. In Techniques in the Life Sciences, (Ed. D.A. Titchen) Elsevier Scientific Publ. Ireland Ltd., County Care, 1982, pp l-28 Ruckebusch, Y. and Grivel, M.L A technique for long term studies of the electrical activity of the gut in the foetus and neonate. In ROC. 4th Symp. Gastrointestinal Motility, Bar@ Mitchell Press, Vancouver, 1974, pp 428-434

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