Electrogastrogram based digestion detection system for coma patients

Electrogastrogram based non-invasive digestion diagnostic system for coma patients

CHAPTER 1

INTRODUCTION

Electrogastrography is a noninvasive method for the recording of gastric

myoelectrical activity that controls gastric motility. Although the first measurement of the

EGG was reported 70 years ago, the progress in this field has been very slow , especially

compared with other cutaneous electrophysiological measurements, such us the

Electrogastrography because of its difficulty in data acquisition, lack of understanding ,etc. .

Due to the advancement in quantitative analysis of the EGG, more and more physicians and

biomedical researchers have been interested in this field. The abnormality arises due to

recurrent nausea, vomiting, Dyspepsia, Stomach ulcer, Cyclic vomiting syndrome, etc which

signals that the stomach is not emptying food normally. If the EGG is abnormal, it confirms

that the problem probably is with the stomach's muscles or the nerves that control the

muscles. This project deals with the novel approach of recording of the electrical signals that

travel through the muscles of the stomach and control the muscle’s contraction and analysis

with the statistical parameters such as mean, rms, kurtosis, mode, median, amplitude,

variance, frequency and power. The EGG can be considered as an experimental procedure

since its exact role in the diagnosis of digestive disorders of the stomach has not been defined

yet.

1.1 ELECTROGASTROGRAM

An EGG is similar to an electrocardiogram of the heart. It is a recording of the

electrical signals that travel through the muscles of the stomach and control the muscle’s

contraction. EGG is used when there is a suspicion that the muscles of the stomach or the

nerves controlling the muscles are not working normally. EGG done by placing the electrode

cutaneously over the stomach and the electrical signals coming from the stomach’s muscles

are sensed by the electrode and recorded on a computer for analysis by lying patient quietly.

In normal individuals the EGG is a regular electrical rhythm generated by the muscles of the

stomach and the power (voltage) of the electrical current increases after the meal. In patients

with abnormalities of the muscles or nerves of the stomach, the rhythm often is irregular or

there is no post-meal increase in electric power. EGG will not have any side effects and it is

Sahrdaya College of Engineering and Technology 1


painless study. The normal individual EGG frequency value is found to be approximately 3

cycles per minute.

1.1.1 Measurement of Electrogastrogram

The stomach Gastric Myoelectrical Activity (GMA) can be measured serosally,

intraluminally, or cutaneously. The serosal recording can be obtained by placing electrodes

on theserosal surface of the stomach surgically. The intraluminal recording can be acquired

by incubating a catheter with recording electrodes into the stomach. Suction is usually

applied to assure a good contact between the electrodes and the stomach mucosal wall. The

serosal and intraluminal electrodes can record both slow waves and spikes, since these

recordings represent myoelectrical activity of a small number of smooth muscle cells. These

methods are invasive and their applications are limited in animals and laboratory settings.

EGG, a cutaneous measurement of GMA using surface electrodes, is widely used in humans

and clinical settings, since it is non-invasive and does not disturb the ongoingactivity of the

stomach (Chen and Mccallum 1991). A number of validation studies have documented the

accuracy of the EGG by comparing it with the recording obtained from mucosal and serosal

electrodes (Hamilton et al 1986). Reproducibility of the EGG recording has been

demonstrated, with no significant day-to-day variations. In adults, age and gender do not

seem to have any influence on the EGG.

1.2 ANATOMY OF THE STOMACH

The main function of the stomach is to process and transport food.After feeding, the

contractile activity of the stomach helps to mix, grind andeventually evacuate small portions

of chyme into the small bowel, while therest of the chyme is mixed and ground.

Anatomically, the stomach can bedivided into four major regions: Fundus (the most

proximal), Corpus (body),Antrum and pylorus. Histologically, the fundus and corpus are

hardlyseparable. In the antral area, the density of the smooth muscle cells increases.The area

in the corpus around the greater curvature, where the split of thelongitudinal layers takes

place, is considered to be anatomically correlatedwith the origin of gastric electrical activity.

The stomach wall, like the wall ofmost other parts of the digestive canal, consists of three

layers: the mucosal(the innermost), the muscularis and the serosal (the outermost).



Fig 1.2 Anatomy of stomach

The mucosal layer itself can be divided into three layers: themucosa (the epithelial

lining of the gastric cavity), the muscularis mucosae (low density smooth muscle cells) and

the submucosal layer (consisting of connective tissue interlaced with plexi of the enteric

nervous system). The second gastric layer, the muscularis, can also be divided into three

layers: the longitudinal (the most superficial), the circular and the oblique. The longitudinal

layer of the muscularis can be separated into two different categories: a longitudinal layer that

is common with the esophagus and ends in the corpus, and a longitudinal layer that originates

in the corpus and spreads into the duodenum as shown in Figure 1.2.

1.2.1 Normal GastricMyoelectricalActivity

Myoelectrical activity is originated along the gastrointestinal tract.In vitro studies

using smooth muscle strips of the stomach have revealed independent GMA from different

regions of the stomach (Smout et al 1980).The highest frequency of the gastric myoelectrical

activity was recorded in thecorpus and the lowest frequency in distal antrum. However, in

vivo studies demonstrated a uniform frequency in the entire stomach under healthy

conditions, because the myoelectrical activity in the corpus with the highest frequency drives

or paces the rest of stomach into the same higher frequency. GMA is composed of slow

waves and spike potentials. The slow wave is also called the pacesetter potential, or electrical

control activity. The spike potentials are also called action potentials or electrical response



activity. While slow waves originated from the smooth muscles, in vitro electrophysiological

studies suggest that Interstitial Cells of Cajal (ICC) are responsible for the generation and

propagation of the slow wave (Sanders, 1996).

Frequency of normal slow waves is species-dependent,approximately 3 cpm in

humans and 5 cpmin dogs, with little day-to-day variations. The slow wave is known to

determine the maximum frequency and propagation of gastric contractions. Figure 1.3

presents an example of normal gastric slow waves measured from a patient. Normal 3 cpm

distally propagated slow waves are observed. Spike potentials are known to be directly

associated with gastric contractions, that is, gastric contractions occur when the slow wave is

superimposed with spike potentials (Chen et al 1993). In the stomach, it is not uncommon to

record gastric contractions with an absence of spike potentials in the electrical recording.

Some other forms of superimposed activity are also seen in the electrical recording in the

presence of gastric contractions (Chen J et al 1994).

1.3 EGG SIGNALS

EGG signal for the normal activity is defined as an electrical signalat a frequency of 3

cpm and it is shown in Figure 1.3.

Digestive System disorders namely bradygastria, dyspepsia, nausea,tachygastria, ulcer

and vomiting result in the variation in the EGG waveform. Brief detail of the above

mentioned disorders is presented below.

1.3.1Bradygastria

Bradygastria is defined as a decreased rate of electrical pacemakeractivity in the

stomach which is less than 2cpm for at least 1 minute. The EGG pattern for bradygastria is


Fig 1.3 EGG of a normal person


shown in Figure 1.3.1. It may be associated with nausea, gastroparesis, irritable bowel

syndrome, and functional dyspepsia.

1.3.2 Dyspepsia

Dyspepsia (Indigestion) is a vague feeling of discomfort in theupper belly or abdomen

during or right after eating or it is also known as upset stomach. This includes:

A feeling of heat, burning, or pain in the area between thenavel and the lower part of

the breastbone.

A feeling of fullness that is bothersome and occurs soon afterthe meal begins or when

it is over.

It can be accompanied by bloating, belching, nausea, or heartburn.Dyspepsia is a

common problem, and is frequently due to Gastro EsophagealReflux Disease (GERD) or

gastritis (Kenneth 1995 and Sha et al 2009), but for some cases it may be the first symptom

of peptic ulcer disease (an ulcer of the stomach or duodenum) and occasionally cancer.

Figure 2.4 is the EGG for dyspepsia having a frequency of 4–5 cpm.


Fig 1.3.2 Dyspepsia EGG

Fig 1.3.1 Bradygastria EGG


1.3.3 Nausea

Nausea is defined as a sensation of unease and discomfort in theupper stomach with

an involuntary urge to vomit. It often, but not always, precedes vomiting. A person can suffer

nausea without vomiting. Some common causes of nausea are motion sickness, dizziness,

fainting, gastroenteritis (stomach infection) or food poisoning. Nausea may also be caused by

stress, anxiety, disgust, worry and depression.

EGG pattern of Nausea having a frequency of 3.5–6 cpm is shownin Figure 2.5.

1.3.4 Tachygastria

Tachygastria is defined as the increased rate of electrical activity inthe stomach. A

one minute recording having more than 4 cycles is shown in Figure 1.3.4. It is associated

with nausea,gastroparesis, irritable bowel syndrome, and functional dyspepsia.

1.3.5 Ulcer or Peptic Ulcer

Stomach ulcer or peptic ulcer is small erosion (hole) in thegastrointestinal tract. The

most common type, duodenal, occurs in the first 12 inches of small intestine beyond the


Fig 1.3.3 Nausea EGG

Fig 1.3.4 Tachygastria EGG


stomach. Ulcers of that form in thestomach are called gastric ulcers. An ulcer is not

contagious or cancerous.Duodenal ulcers are almost always benign, while stomach ulcers

may become malignant. A peptic ulcer is a sore in the lining of the stomach or the duodenum,

the first part of the small intestine. Burning stomach pain is the most common symptom. The

pain

May come and go for a few days or weeks.

May disturb one’s activity when the stomach is empty.

1.3.6 Vomiting

Vomiting is the forceful expulsion of contents of the stomach andoften, the proximal

small intestine. It is a manifestation of a large number of conditions, many of which are not

primary disorders of the gastrointestinal tract. Regardless of the cause, vomiting can have

serious consequences, including acid-base derangements, volume and electrolyte depletion,

malnutrition and aspiration pneumonia. The frequency is observed to be 5.5-6.5 cpm.

The diagrams of the above waveforms are referred from the following paper.

http://shodhganga.inflibnet.ac.in:8080/jspui/bitstream/10603/16353/7/07_chapter2.pdf


Fig 1.3.5 Ulcer EGG

Fig 1.3.6 EGG during vomiting


1.4 EGG ELECTRODES

Electrodes are the sensors which tap the electrical signals from the outer layer of the

stomach. Surface electrodes like silver/silver chloride (Ag/AgCl) shown in Figure 1.4a are

used for this purpose.

It is available in two sizes, standard 20 mm and miniature 11 mm. These electrodes

provide stable recordings for various physiological measurements including sleep recordings,

exercise testing, pediatric monitoring and the recording of low voltage DC and low

frequencies like the signals from the stomach. Surface electrodes are very popular because of

their small covering area and adhesive to provide highly accurate, optimal recordings.

Fig 1.4a Ag-AgCl surface electrodes

Demerits of Passive Electrodes (Ag/AgCl)

High skin contact impedance due to their irregular surfaces,and consequently they

introduce high frequency noise.

Introduce dc offset into front-end electronic sensing circuitsdue to motion artifacts.

Gel or other adhesive materials need to be used.

Not reusable when used with an adhesive.

High impedance signals are susceptible to physicalmovements and power line

interference.

In addition to Ag-AgCl electrode, active electrodes are also used. The role of the

active electrode is to pick up a bio potential signal while transforming high source impedance

to low source impedance. Due to the high source impedance the signal loses energy and

becomes weaker. The output impedance of the active electrode is low and reduces the

interference of the electrically and mechanically induced noise. Thus interference due to 50

Hz supply harmonics and the electromagnetic interference is reduced by using active



electrode. Schematic of the active electrode is shown in Figure 1.4c. They are used to buffer

the signals and also provide impedance matching. Silver coins are placed on the surface of

the stomach to tap the signal. The active electrodes are well protected within a shield to

reduce electromagnetic interference.

Merits of Active Electrodes

Pick up a bio potential signal while transforming high sourceimpedance to low source

impedance.

Buffer is used for impedance matching

No external signal interference

Reusable

Only drawback is a separate power supply requirement for the IC.


Fig 1.4b Active Electrode

Fig 1.4c Schematic of active electrode circuit


For acquisition of EGG, the electrodes sense the electrical signals coming from the stomach's

muscles cutaneously and data is recorded on a computer for further analysis with different

techniques.

1.4.1 Electrode placement

Standard electrocardiographic type electrodes are commonly used for EGG

recordings. Although there is no established standard, it is generally accepted that the active

recording electrodes should be placed as close to the antrum as possible to yield a high

signal-to-noise ratio. The EGG signals can be recorded with either unipolar or bipolar

electrodes, but bipolar recording yields signals with a higher signal-to-noise ratio. The

electrical signals are generally produced in the mid-corpus of the stomach where the

electrical activity takes place. The positioning of the Ag/ Agcl electrodes or Active Electrode

(AE) for tapping of these signals is shown in Figure 1.4.1.

Fig 1.4.1 Placement of Electrodes

Two electrodes A and B are placed in the fundus and the mid corpus of the stomach.

The third electrode C is placed as ground at the end of the stomach region for patient safety

i.e. with respect to figure, Electrode A is shown in red color, it is positioned in the

midclavicular line (left side) approximately two inches below the left costal margin,

Electrode B is shown in Black color, it is placed at the midpoint between the xiphoid and

umbilicus and ground Electrode C or reference electrode shown in green color is positioned

in the midclavicular line on the right side (Krusiec and jonderko 2008).



1.5 EGG RECORDING PROCEDURE

EGG is vulnerable to motion artifacts due to the nature of cutaneous measurement.

Accordingly, a careful and proper preparation before the recording is crucial in obtaining

reliable data. EGG signals are very weak, it is very important to minimize the impedance

between the skin and electrodes. The abdominal surface where electrodes are to be positioned

should be shaved if necessary, cleaned and abraded with some sandy skinpreparation jelly

(e.g. K-Y Jelly, produced by Johnson & Johnson Co) in order to reduce the impedance

between the bipolar electrodes and skin. The EGG may contain severe motion artifacts if the

skin is not well prepared. The subject undergoing EGG procedure needs to be in a

comfortable supine position or sit in a reclining chair in a quiet room throughout the study

(Anna Kascika- Jonderko et al 2006,Krusiec and jonderko 2008 and Contreras et al 2010).

The supine position is recommended for recording EGG, because the subject is more relaxed

in this position, and thus introduces fewer motion artifacts. The subject should not be

engaged in any conversation and should remain as still as possible to prevent motion artifacts.

Recordings are made for both fasting and after a meal with the patient lying quietly.

1.6 COMA

In medicine, a coma is a state of unconsciousness lasting more than six hours in which

a person: cannot be awakened; fails to respond normally to painful stimuli, light, or sound;

lacks a normal wake-sleep cycle; and, does not initiate voluntary actions. A person in a state

of coma is described as being comatose.

Fig 1.6 Statistics of comatose patients worldwide


http://en.wikipedia.org/wiki/Unconsciousness


1.6.1 Causes

A comatose person exhibits a complete absence of wakefulness and is unable to

consciously feel, speak, hear, or move. For a patient to maintain consciousness, two

important neurological components must function. The first is the cerebral cortex—the gray

matter that covers the outer layer of the brain. The other is a structure located in the

brainstem, called reticular activating system (RAS). Injury to either or both of these

components is sufficient to cause a patient to experience a coma. The cerebral cortex is a

group of tight, dense, "gray matter" composed of the nuclei of the neurons whose axons then

form the "white matter", and is responsible for perception, relay of the sensory input

(sensation) via the thalamic pathway, and many other neurological functions, including

complex thinking.

RAS, on the other hand, is a more primitive structure in the brainstem that is tightly in

connection with reticular formation (RF). The RAS area of the brain has two tracts, the

ascending and descending tract. Made up of a system of acetylcholine-producing neurons, the

ascending track, or ascending reticular activating system (ARAS), works to arouse and wake

up the brain, from the RF, through the thalamus, and then finally to the cerebral cortex. A

failure in ARAS functioning may then lead to a coma.

1.6.2 Feeding Tube

A person who is in a coma or persistent vegetative state can’t say she’s thirsty.

Similarly, a severely brain damaged person may be unable to express himself. Such

individuals won’t even understand what’s happening. They’ll simply feel thirst and, within

five to 21 days, they will die of dehydration.

If a person is having ongoing and serious trouble swallowing and can't get enough

food or liquids by mouth, a feeding tube may be put directly into the stomach through the

abdominal skin. This procedure is called a percutaneous endoscopic gastrostomy (PEG). The

tube allows feeding directly into the gastrointestinal tract to occur by bypassing

the mouthand esophagus (the “food tube” leading to the stomach).

The feeding of a coma patient is a hectic task, which involvespassing a feeding tube

from the patient’s nose into the stomach. Their digestion is checked by sucking out the

contents from the stomach at periodic intervals of time. If the acquired content is more, it

means that the digestion is not proper, whereas a little content indicates the proper digestion.


http://www.webmd.com/digestive-disorders/picture-of-the-esophagus

http://www.webmd.com/oral-health/ss/slideshow-mouth-problems

http://www.webmd.com/skin-problems-and-treatments/picture-of-the-skin

http://www.webmd.com/digestive-disorders/picture-of-the-stomach

http://www.webmd.com/oral-health/anatomy-of-the-mouth

http://en.wikipedia.org/wiki/Reticular_activating_system

http://en.wikipedia.org/wiki/Cerebral_cortex


1.6.3 Checking for Residual Contents

The most common reasons for checking gastric content residual include determining

whether to continue or hold a feeding, and assessing patient tolerance to the feeding by

measuring the amount of food left in the stomach (School Health Handbook, 2001). This

procedure should be included in the physician’s order or in the district procedure approved by

the physician and parent. A typical procedure includes:

Insert a 30–60 mL syringe into the adaptor port and gently aspirate stomach content to

determine the amount of gastric residual.

If the amount exceeds a specified amount (usually 50–100 mL), return aspirated

contents to the stomach and hold the feeding for one hour.

Recheck residual in one hour and hold feedings if it continues to exceed residual

limits. Notify the physician for direction and inform the parent.

Fig 1.6.2 Feeding tube

1.7 PROJECT IDEA

This project aims at determining whether the digestion has occurred properly or not,

by using ElectroGastroGram (EGG) signal obtained through surface electrodes from the

patient’s abdomen. The pre-prandial (before meal) and post-prandial (after meal) signals are

acquired and pre-processed using an instrumentation amplifier and then through a DAQ, it is

fed to a low-pass filter and then fed into the LABVIEW software, which indicates the

respective values of signal amplitude, frequency, mean, mode, median, variance, RMS etc.

Thus, after comparing with standard values, the features of an EGG signal will express the

digestion condition, thereby eliminating the invasive suction procedure, applicable to those

patients in CCUs and paralysed state.



CHAPTER 2

LITERATURE SURVEY

Walter Alvarez (1920), a gastroenterologist first performed andreported about

Electrogastrography and in 1921, recorded the first humanEGG by placing two electrodes on

the abdominal surface of ‘‘a little oldwoman’’ and connected them to a sensitive string

galvanometer. A sinusoidlikeEGG with a frequency of 3 cycles/min (cpm) was then recorded.

Harrison Tumpeer (1926), a pediatrician is the second investigator to discoverthe

EGG. He used limb leads to record the EGG from a 5 week old child whowas suffering from

pyloric stenosis and observed the EGG as looking like anECG (electrocardiogram) with a

slowly changing baseline.

Davis (1957), a psychophysiologist published two papers on thevalidation of the EGG

using simultaneous recordings from needle electrodes and a swallowed balloon. Although

Davis made only slow progress in EGG research, his two papers had stimulated several other

investigators to begin doing EGG research. Stern (2000), started to work in Davis’ lab to do a

research in EGG.

Stevens and Worrall (1974) were probably the first ones who applied the spectral

analysis technique to EGG and then analyzed EGG data using Fourier transform.

Brown et al (1975) mentioned that if recording was started within an hour of attaching

electrodes there was often a large amount of electrode noise and respiratory artifactis

observed.Smout et al (1980) showed that the amplitude of the EGG increases when

contractions occur.

Koch et al (1985) reported their study on simultaneous recordings of the EGG and

fluoroscopy. They repeatedly observed the correspondence between EGG waves and antral

contractions during simultaneous EGGfluoroscopyrecordings.To extract information about

both the frequency of 18 EGG and time variations of the frequency, a running spectral

analysis method using FFT was introduced by van der Schee and Grashus (1987).

Waldhausenet al (1990) studied adout the gastrointestinal myoelectric and clinical

pattern recovery after aparotomyChen et al. (1989) developed a modern spectral analysis

technique based on an adaptive autoregressive moving average model. This method yields

higher frequency resolution and more precise information about the frequency variations of

the gastric electrical activity. It is especially useful in detecting dysrhythmic events of the

gastric electrical activity with short durations.



Sobakin et al (1962) performed the EGG in 164 patients and 61 healthy controls and

reported that ulcers caused no change in the EGG, but that pyloric stenosis produced a

doubling of amplitude, and stomach cancer caused a breakup of the normal 3 cpm rhythm.

This was probably the first large-scale clinical use of the EGG.

In the past two decades, numerous studies have been reported on the clinical use of

the EGG including understanding the relationship between the EGG and gastric motility,

gastric myoelectrical activity in pregnant women, gastric myoelectrical activity in diabetics or

gastroparetic patients, gastric myoelectrical activity in patients with dyspepsia and prediction

of delayed gastric emptying using the EGG.

Stern (2000) wrote “the history of EGG can be described as three beginnings, a length

period of incubation, and a recent explosion”.

Zhishun Wang and Chen (2001) identified that myoelectricalrecording of gut contains

slow rhythmicity and fast rhythmicity (spikes). They said that conventional method is not

accurate in the separation of the slow wave and the spikes. They introduced a novel and fast

blind source separation (BSS) algorithm to extract spike activities from the myoelectrical

recordings 19 obtained in dogs and it is not affected by the high frequency components of the

slow wave. The independent component analysis (ICA) is performed using fourth order

statistic movements (Kurtosis). They observed that the detection of gastrointestinal motility is

important and clinical gastroenterology and gastroenterological research. They also said that

motility parameters are useful in the identification of gastrointestinal motility patterns.

Anna Kascika- Jonderko et al (2006) carried out a study on conductive area size of

recording electrodes affecting the quality of a multichannel electrogastrogram and they found

that type 2222 yields a stable between electrode- electrical conductivity throughout the

examination and type 2660 (Ag/Agcl) is recommended because it offers a good performance

in EGG acquiring and it is not require any supplementation with a conductive gel. They

found single channel is a classical one and they declared that huge research work still has to

be performed to overcome it. For analysis of EGG signal they applied three algorithms

namely – A running spectrum analysis, overall spectrum analysis, cross channel analysis for

both preprandial andpostprandial condition. The authors found that 2-2.5 cm2 conductive

areas is sufficient to obtain an accurate result with good quality of electrodes, careful

observation is done in the procedure of skin preparation. They also declared that current

system of bioelectrical signal acquisition, conditioning and analysis are to be perfect to avoid

noisy source of a weak electrical signal across the abdominal wall from the stomach to the

abdominal surface.



Jung (2006) designed and implemented telemetry capsule for measuring EGG. Jin et

al (2007) reported EGG is useful for evaluating the effect of illumination and taste

stimulation.

Krusiec and jonderko (2008) checked reproducibility of parameters of multichannel

electrogastrogram in subjects for different condition 20 comprising of normal subjects and

abnormal subjects. They found that reproducibility of multichannel electrogastrographic

parameters did not sufferbetween normal and abnormal subjects. Also they observed that

gender; test meals did not affect the reproducibility and Medium Term Reproducibility

(MTR) worse than the Short Term Reproducibility (STR). From the finding the average

percentage of slow wave coupling (APSWC) provides a good reproducibility for clinical

application than Maximum Dominant Frequency Difference (MDFD) and Spatial Dominant

Power Difference (SDPD). They conducted this study according to Helsinki declaration. The

acquisition is performed either with a pair of active electrode with reference electrode or pair

of active electrode with ground electrode. They analyze the EEG by applying three

algorithms used by Anna Kascika- Jonderko et al 2006.

Jang et al (2009) said that cutaneous electrogastrogram recording suits for non

invasive gastrointestinal diagnosis. They developed a portable EEG recording system with

voice recording devices with low supply voltages, low power consumption, and software

demodulation to simplify the complexity of the system. It is small in size, compact and

suitable for long term portable recording.

Contreras et al (2010) recorded EGG signals with three pair of electrodes cutaneously

with cut off frequency of 1 Hz for low pass filter and acquired with a sampling frequency of

10Hz. They analyzed the EGG signals online and also they said that signal can also be

reanalyzed offline for generating EGG database with latest windows 2000/XP and vista. They

classified the signals in four possible conditions based on the frequency as tachygastria,

bradygastria, arrhythmic and typical conditions using spectrum value and percentage of each

pacemaker frequency. The authors declared that there is no public database of EGG in

different conditions. Also they said that using the relevance of this work a database can be

created and new parameters can also be studied. They also mentioned that EGG

characteristics (or) 21 electrical parameters obtained from it for the dysfunction in

electromechanical functions of the stomach by introducing a non invasive technique which

isaccepted in the diagnostic clinic in mexico.

G.Gopu, R.Neelaveni and K.Porkumaran, presented a research paper on

“Investigation of Digestive System Disorders using Electrogastrogram”, Proceeding



International conference on Computer and Communication Engineering (ICCCE ’08), Vol.2,

pp.201-205, 13-15 May 2008, Kuala Lumpur, MALAYSIA.

G.Gopu, R.Neelaveni and K.Porkumaran, presented a research paper on “Acquisition

and Analysis of Electrogastrogram for Human Stomach Disorders”, Proceeding International

conference on Recent Trends in Computational Science (ICRTCS’08), Vol.1,pp.162-169, 11-

13 June 2008, Ernakulam, Kerala,INDIA



CHAPTER 3

DESIGN AND DEVELOPMENT

The sensors used in this recording setup are Ag/Agcl electrodes. The electrodes are used to

tap the electrical signals directly from the surface of the stomach. The electrical signals

generated are usually of very low amplitude ranging from 0.01 to 0.5 mV. This is given as a

input to an instrumentation amplifier which has a gain of 1000. The amplified signal is then

connected to the Data Acquisition Card [DAQ]. DAQ is an instrument for LabVIEW

software. The key function of the DAQ is to act as an interface between the external signal

and the subject after the amplification is sent to the DAQ. The DAQ digitizes this signal and

makes it edible for further processing. DAQ assistant is a module in the LabVIEW flow

diagram which has set of parameters that should be selected to acquire the signal from the

DAQ. There are various other noises that will be obtained during the during signal

acquisition process namely respiratory effects, disturbances due to bowel movements etc., in

order to reject these signals and select the EGG we will have to filter out there noises.

Butterworth band pass filter of tenth order is used for this purpose. The lower cut off

frequency is set to 0.008 Hz and the upper cut-off frequency is set to 1 Hz, which implies that

all those frequency components except in this range will be rejected. The band-pass filter is

designed in LabView itself.This leaves the EGG Signal alone to the Statistical analysis. The

block diagram is given below.


Fig 3. Functional Block Diagram


3.1 INSTRUMENTATION AMPLIFIER

Instrumentation amplifier is a kind of differential amplifier with additional input

buffer stages. The addition of input buffer stages makes it easy to match (impedance

matching) the amplifier with the preceding stage. Instrumentation are commonly used in

industrial test and measurement application. The instrumentation amplifier also has some

useful features like low offset voltage, high CMRR (Common mode rejection ratio), high

input resistance, high gain etc. The circuit diagram of a typical instrumentation amplifier

using opamp is shown below.

Fig 3.1 Instrumentation Amplifier Circuit

A circuit providing an output based on the difference between two inputs (times a

scale factor) is given in the above figure. In the circuit diagram, opamps labelled A1 and A2

are the input buffers. Anyway the gain of these buffer stages are not unity because of the

presence of R1 and Rg. Op amp labelled A3 is wired as a standard differential amplifier. R3

connected from the output of A3 to its non inverting input is the feedback resistor. R2 is the

input resistor. The voltage gain of the instrumentation amplifier can be expressed by using

the equation below.

Voltage gain (Av) = Vo/(V2-V1) = (1 + 2R1/Rg ) x R3/R2

If need a setup for varying the gain, replace Rg with a suitable potentiometer.

Instrumentation amplifiers are generally used in situations where high sensitivity, accuracy

and stability are required. Instrumentation amplifiers can be also made using two opamps, but

they are rarely used and the common practice is to make it using three opamps like what is

shown here. The only advantages of making an instrumentation amplifier using 2 opamps are

low cost and improved CMRR.


Fig 3. Functional Block Diagram


A high gain accuracy can be achieved by using precision metal film resistors for all

the resistances. Because of large negative feedback employed, the amplifier has good

linearity, typically about 0.01% for a gain less than 10. The output impedance is also low,

being in the range of milli-ohms. The input bias current of the instrumentation amplifier is

determined by the op-amps A1 and A2.

To design for a gain of 1100, A1 = 2 , A2=50 and A3=11

For A1 = 2, select Rg= 1k and R1 = 560ohm.

For A2 = 50, select R2 = 1k and R3 = 47k.

For A3 = 11, select Rg = 1k and Rf = 10k.

The 4 op-amps need +15V and -15V to function. The power supply was made using the

circuit shown in figure 3.1.1.

3.1.1 15V dual power supply regulated

Below is the circuit of a 15V regulated dual power supply. The output of the circuit is

+15V and -15V DC. The 110V or 220V to 18V center tap transformer is used to step down

the mains voltage. The Diode D1 to D4 performs the process of rectification which will

convert 18V AC to 18V DC. The 2200uF capacitor is used to filter the voltage coming from

the diodes, and other capacitors in the circuit are used for decoupling. The LM7815 and

LM7915 are voltage regulator ICs which steps down their input voltage to regulated Dual

15V DC.

Fig 3.1.1 15V dual power supply regulated



3.2 NI DAQ USB 6009

Data acquisition (DAQ) is the process of measuring an electrical or physical

phenomenon such as voltage, current, temperature, pressure, or sound with a computer. A

DAQ system consists of sensors, DAQ measurement hardware, and a computer with

programmable software. Compared to traditional measurement systems, PC-based DAQ

systems exploit the processing power, productivity, display, and connectivity capabilities of

industry-standard computers providing a more powerful, flexible, and cost-effective

measurement solution.

Fig 3.2 NI DAQmxUSB 6009



CHAPTER 4

METHODOLOGY

Electrogastrography is a non-invasive technique for recording gastric myoelectrical

activity using cutaneous electrodes placed on the abdominal skin over the stomach. The

surface recording obtained using electrography is called the electrogastrogram.

4.1 RECORDING SETUP

Although this information is most commonly omitted in a biomedical research paper,

appropriate setting of the recording equipment is critically important. Two major issues

associated with an EGG recording device are: (1) amplification: the EGG signal is usually in

a range of 50-500 µV and adequate amplification needs to be provided by a recording device

so that the amplified signal is of an appropriate range for display and analysis, and (2) filter

setting: it determines the frequency range of the EGG signal to be maximally amplified. The

interested range of the EGG signal is in the range of 0.5-9.0 cpm or 0.0083 to 0.15 Hz which

is much lower than that of most of extracellular recordings. In addition to the basic

fundamental frequencies of 0.5-9.0 cpm, it is also important to record certain harmonics

(multiples of the fundamental frequency).Accordingly, an appropriate frequency setting is in

the range of 0.0083 to 1 Hz. A wrong selection of filtering range may lead to a severe

distortion or even disappearance of gastric slow waves in the EGG.

4.2 PROCEDURE FOR RECORDING THE ELECTROGASTROGRAPHY

One common mistake made in the EGG recording is the inadequate preparation of

skin and placement of electrodes. Since the EGG signal is weak, it can be easily distorted or

interfered by motion artifacts due to body movement and/or breathing. In order to accurately

record an EGG, the following procedure should be strictly followed.

4.2.1 Skin preparation

First, the abdominal skin where the electrodes are to be positioned should be

thoroughly cleaned to ensure that the impedance between the pair of electrodes is below 10

kΩ. To do so, it is advised to abrade the skin until it turns pinkish using some sandy skin-

preparation jelly, and then apply a thin layer of electrode jelly for 1 minute for the jelly to



penetrate into the skin. Before placing the electrode, the excessive jelly must be completely

wiped out.

4.2.2 Electrode placement

Regular electrocardiogram (ECG) electrodes can be used for EGG recordings. The

most commonly used configuration for recording 1-channel EGG is to place one electrode at

the midpoint on a line connecting the xiphoid and umbilicus, and the other electrode 5 cm

away (up and 45 degree) to the patient's left. The ground electrode is placed on the left costal

margin horizontal to the first active electrode. If a 4-channel EGG recording device is used,

multiple electrodes should be placed according to previous studies. The multiple channel

EGG may provide more information about slow wave propagation and coupling.

Fig 4.2.2 Electrode Placement

4.2.3 Subject position

The most important points in positioning the subject are (1) to ensure that the subject

is in a comfortable position, most commonly supine, so that body movement can be

completely avoided or reduced to the minimal. The subject should be asked not to talk, move,

read or make phone calls during the procedure; and (2) to ensure that the position of the

subject is the same if there are multiple sessions. Timing of unavoidable body movement or

motion artifacts should be noted and the recording periods with motion artifacts must be

removed before analysis.



4.2.4 Duration of recording

Another common mistake in recording the EGG is that the recording is too short.

Unlike the ECG in which there are about 60 waves every minute, the EGG is composed of

only 3 waves every minute. That is, if the recording is of a short duration of 5 minutes, there

are only 15 waves which are obviously insufficient for analysis and interpretation. Ideally, at

least a 30-minute period is needed to ensure an accurate measure of gastric slow waves in a

particular state, such as fasting, fed, baseline or after intervention.

4.2.5 Protocol for a clinical electrogastrography test

When EGG is used as a clinical test, the EGG should be recorded in both fasting and

fed states. To ensure the stomach is empty when the baseline or fasting EGG is recorded, the

subject should be fasted for at least 6 hours because the complete emptying of the stomach

takes about 4 hours in a healthy subject and this can be longer if a patient has a suspected

gastric motility disorders. Drinking (water) is not allowed at least 2 hours before the test. The

duration of the postprandial recording should be at least 30-60 minutes, depending on the

symptomatic response of the subject to meals. Similarly to other motility tests, any

medications known to alter gastric motility should be discontinued for at least 2-3 days before

the EGG test.

The test meal should contain a minimum of 250 kcal (better > 400 kcal) with no more

than 35% of fat. Solid meals are usually recommended although a few investigators have

used water as the test "meal." It should be noted that different test meals may result in

different postprandial EGG responses. Accordingly, when data are compared among different

studies, the composition of the meal should be carefully examined. In healthy humans, a solid

test meal with sufficiently high calories (> 400 kcal) results in an increase in both amplitude

and frequency of gastric slow waves; a liquid meal may increase slow wave amplitude but

reduce its frequency; a meal with a high percentage of fat (> 50%) may induce gastric

dysrhythmia. Accordingly, the composition of the meal should be considered when

interpreting postprandial EGG.

The study subject should be kept alert and should not fall asleep during the procedure

as gastric slow waves have been reported to change during sleep.



4.2.6 Pitfalls in electrogastrography recording

It is most important to note that an EGG study could be flawed or completely useless

if any of the followings takes place: the skin is not appropriately prepared, the subject is

engaged in conversation, the subject moves frequently and the periods with body movement

are not deleted, or the recording for a particular condition is shorter than 15 minutes.

4.3 ELECTROGASTROGRAM: ANALYSIS

Unlike the electrocardiogram with which a physician can perform diagnosis by

visually examining the tracing, the EGG must be subjected to computerized spectral analysis.

This is because the EGG signal is weighted summation of all gastric slow waves presented in

the stomach; its waveform is dependent on many uncontrollable factors and no diagnostic

criteria have been established using the waveform of the EGG. In addition, the EGG also

contains respiration artifact that is between 12-25 cpm and sometimes the ECG artifacts (< 60

cpm). Occasionally, the slow wave of the small intestine may also be recorded in the EGG (9-

12 cpm). Although these interferences distort gastric slow waves in the EGG, their

frequencies do not overlap with that of the gastric slow waves. Consequently, spectral

analysis can be performed to separate the gastric slow waves from interferences. As stated

earlier, before spectral analysis is performed, any periods with motion artifacts must be

identified and deleted because motion artifactscannot be separated from the gastric slow

waves even with spectral analysis.

The signal analysis is performed using LabVIEW 8.5 statistical analysis sub VI for

the recorded EGG before and after food to determine the following parameters.

Amplitude - The amplitude of a periodic variable is a measure of its change over a

single period (such as time or spatial period).

Frequency - Frequency is the number of occurrences of a repeating event per unit

time.

Variance - In probability theory and statistics, variance measures how far a set of

numbers is spread out. A variance of zero indicates that all the values are identical.

Variance is always non-negative: a small variance indicates that the data points tend

to be very close to the mean (expected value) and hence to each other, while a high

variance indicates that the data points are very spread out around the mean and from

each other.



Mode - The mode is the value that appears most often in a set of data. In other words,

it is the value that is most likely to be sampled. The mode of a continuous probability

distribution is the value x at which its probability density function has its maximum

value, so, informally speaking, the mode is at the peak.

Median - In statistics and probability theory, the median is the letter separating the

higher half of a data sample, a population, or a probability distribution, from the lower

half.

Kurtosis - In probability theory and statistics, kurtosis (from Greek: κυρτός, kyrtos or

kurtos, meaning "curved, arching") is any measure of the "peakedness" of the

probability distribution of a real-valued random variable. In a similar way to the

concept of skewness, kurtosis is a descriptor of the shape of a probability distribution

and, just as for skewness, there are different ways of quantifying it for a theoretical

distribution and corresponding ways of estimating it from a sample from a population.

Root Mean Square - The root mean square (abbreviated RMS or rms), also known as

the quadratic mean in statistics is a statistical measure defined as the square root of

the mean of the squares of a sample. In physics it is a value characteristic of a

continuously varying quantity, such as a cyclically alternating electric current,

obtained by taking the mean of the squares of the instantaneous values during a cycle.

Power - The power of a signal is the sum of the absolute squares of its time-domain

samples divided by the signal length, or, equivalently, the square of its RMS level.

4.4 ALGORITHM AND FLOWCHART

Lightly abrade the skin with abrasive pads, and put a spot of gel on the electrode

contact area.

Two electrodes are placed on the Fundus and the mid-corpus and a reference

electrode is placed on the right side of the abdomen.

The output of the electrodes is given to the Instrumentation amplifier.

The amplified output signal is given to the virtual instrument setup via DAQ

instrument.

From DAQ Assistant (NI-DAQmx) device,analog voltage is selected and the same is

filtered using tenth order Low pass Butterworth filter.

The output of the filter is given to the statistical and spectral analysis sub VI.



The statistical parameters such us mean, rms, kurtosis, mode, median, amplitude,

variance, frequency and power are recorded.

These data are displayed on the PC using LabVIEW software and the statistical

parameters are recorded for preprandial and postprandial conditions.


Fig 4.4 Flowchart of the procedure


CHAPTER 5

RESULT

The standard values of all the above mentioned signal parameters for a normal

digestion condition are already determined. Therefore, by comparing with those standard

values, we could determine whether the digestion has occurred properly or not. The

LabVIEW 8.5 version was used to carry out the signal analysis. DAQ USB 6009 was used to

interface the signals with the computer. The snapshots of the block diagrams and the front

panels of the program are given below.


Block Diagram of the EGG write program



Front Panel of the EGG write program

Block Diagram of the EGG read program


The experiment was performed on a 20 year old female subject. The obtained values

of the signal features and the snapshot of the whole recording setup is given below.

PRE-PRANDIAL SIGNAL POST-PRANDIAL SIGNAL

Amplitude (Maximum peak) 0.432 1.63327

Peak to peak amplitude 0.864 3.26654

Mode 0.0029 0.00816637

Median 0.00965 0.0169349

Skewness 0.965 1.78671

RMS 0.02568 0.0480096

Kurtosis 10.586 5.10173

Variance 0.006 0.16961

Standard Deviation 0.235 0.411838


Front Panel of the EGG read program

SIGNAL PARAMETERS




CHAPTER 6

DISCUSSION

In this project, we have used the EGG to record myoelectrical activity for the patients,

who are not able to voluntarily eat. The statistical parameters for the EGG signals are

obtained with the help of LabVIEW software and its accessories for the both preprandial

condition and postprandial condition. A normal or abnormal EGG will not only help

distinguish patient heterogeneity in clinical studies but might also provide a useful objective

marker of treatment effect . Further studies of wavelet transform tool in MATLAB software

may improve the accuracy of the stomach disorders diagnosis.

The statistical parameters of the EGG are compared and it is observed that the power

of the signal increased is confirmed in the postprantial condition. The signal analysis can be

extended further using spectral analysis to a greater extent to study the intricate behaviour of

the EGG signals which would help diagnose the diseases more efficiently and precisely. A

database for each disease is desired to be created so that sufficient data will be available to

diagnose a disease.

The obtained signals were combined with so many artefacts. So a perfect EGG signal

was not obtained in the college lab. Thus, filtering was a great difficulty.

Working on this project have given us a new and definitely valuable experience in

user-centered design and development. The most interesting part was the cooperation we had

among the group members and the hard work that we put forward to complete it.We also

planned to produce an automatic feeding system as a continuation of this project.



CHAPTER 7

CONCLUSION

The diagnosis of coma has become one of the biggest battlegrounds in medical care.

While some doctors insist that comatose patients will never recover and should be starved or

dehydrated to death, examples of people who have emerged from comas to live full and

productive lives can be found across the country.The feeding of a coma patient is a hectic

task, which involvespassing a feeding tube from the patient’s nose into the stomach. Their

digestion is checked by sucking out the contents from the stomach at periodic intervals of

time. If the acquired content is more, it means that the digestion is not proper, whereas a little

content indicates the proper digestion.

This project aimed at determining whether the digestion has occurred properly or not,

by using ElectroGastroGram (EGG) signal obtained through surface electrodes from the

patient’s abdomen. The pre-prandial (before meal) and post-prandial (after meal) signals

wereacquired and pre-processed using an instrumentation amplifier, and then through a DAQ,

it was fedto the LABVIEW software via a Butterworth Low-pass filter. The computer

indicated the respective values of signal amplitude, frequency, mean, mode, median,

variance, RMS etc. Thus, after comparing with standard values, the features of an EGG signal

could express the digestion condition, thereby eliminating the invasive suction procedure,

applicable to those patients in CCUs and paralysed state.



REFERENCE

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[8] A.Leahy, K.Besherdas, C.Clayman, I.Mason, O.Epstein., “Abnormalities of the

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http://shodhganga.inflibnet.ac.in:8080/jspui/bitstream/10603/16353/7/07_chapter2.pdf

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Electrogastrogram based digestion detection system for coma patients