To Obtain ECG of a Resting Human Subject and Verify the Algebraic Relationship

5/28/2018 To Obtain ECG of a Resting Human Subject and Verify the Algebraic Relationship

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Applied Instrumentation Lab 8EI7

Global Technical Campus, Jaipur Page 1

Experiment No.7

Object: - To obtain ECG of a resting human subject and verify thealgebraic relationship amongst units leads.

Apparatus: - Heart ratemonitor cum ECG Simulator ST2351, ECG Electrodes, PC,RS 232 Cable, Oscilloscope, Banana Connector

Theory: - The heart is basically a hollow muscular pump, which pushes the bloodthroughout the body via the blood vessels. It is located between the lungs and slightly to

the left of center. The heart is an involuntary muscle that has approximately seventy toninety contractions per minute during a restful state. It begins to pump early in the life of

a foetus and will continue unceasingly until death. The heart wall is divided into three

layers: Pericardium, Myocardium and Endocardium. The heart is divided by a partition orseptum into two halves. The halves are in turn divided into chambers. The upper two

chambers of the heart are called atria and the lower two chambers are called ventricles.

Valves allow blood to flow in one direction between the chambers of the heart.The heart

has four distinct chambers.

1. Right atrium is the thin-walled area that receives the venous or "used" blood returning

to the body by the veins.

2. Right ventricle is the "pump" area of the heart's right side. The atrium dumps the blood

into the ventricle where it is then pumped out the pulmonary arteries and to the lungs.3. Left atrium receives the oxygenated blood returning from the lungs.

4. Left ventricle has the thickest walls of all. It is from this chamber the blood is pumped

out of the heart, into the aorta and out to the rest of the body.

Fig. 1.1HumanHeart Construction


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Heart valves:

1. Tricuspid valve is the one located at the entrance of the right ventricle. It prevents theblood from washing back into the right atrium.

2. Pulmonary semi lunar valve is located between the right ventricle and the pulmonaryartery.

3. Mitral valve is made of very heavy cusps and is located at the entrance of the leftventricle. This is a powerful valve that closes as the left ventricle begins each of its

contractions to ensure the oxygenated blood doesn't re-enter the left atrium.

4. Aortic valve is located, as its name would imply, between the left ventricle's exit andthe aorta itself.

Electo Cardio Gram (ECG): -As the heart undergoes depolarization and repolarization,the electrical currents that are generated spread not only within the heart, but alsothroughout the body. This electrical activity generated by the heart can be measured by

an array of electrodes placed on the body surface. The recorded tracing is called anElectrocardiogram (ECG, or EKG). A "typical" ECG tracing is shown below. Thedifferent waves that comprise the ECG represent the sequence of depolarization and

repolarization of the Atria and Ventricles.

Fig. 1.2ECG Wave form PQRST

The P wave represents the wave of depolarization that spreads from the SA node

throughout the atria, and is usually 0.08 to 0.1 seconds (80-100 ms) in duration.

The QRS complex represents ventricular depolarization. The duration of the QRS

complex is normally 0.06 to 0.1 seconds. This relatively short duration indicates that

ventricular depolarization normally occurs very rapidly.


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The T wave represents ventricular repolarization and is longer in duration than

depolarization (i.e., conduction of the repolarization wave is slower than the wave ofdepolarization). Typically the total time required for one complete cycle of the heart

electrical activity ranges from approximately 0.4 to 0.6 second. A healthy ECG shows anormal sinus rhythm. This is when each depolarization of the cardiac conduction system

creates a P wave, followed by a QRS complex, followed by a T wave. During a normalsinus rhythm, the atria are contracting first (around the time of the P wave), and the

ventricles contract second (around the time of the QRS complex). Ventricular relaxation

occurs around the time of the T wave.

Electrodes and Standards ECG Leads:- The Bio Electric signal generated on the

surface of body is picked up by using the electrodes. The electrodes make electricalconduction, which is necessary for making measurements. The surface electrodes picked

up potentials from the surface when placed over it without damaging the tissues; whereas

deep-seated electrode senses the potential difference arising inside the live tissue or cell.The most common types of electrodes routinely used for ECG recording are circular or

rectangular surface electrodes. An electrode conductive jelly is applied between the body

and the electrode to reduce contact impedance. Floating are suitable and effective for

long term monitoring they consists of Agcl3metal electrode and flat plastic washer whichdoes not allow metal to make contact with the body directly. This arrangement reduces

the effect of motion artifacts. Floating electrodes are placed on the chest with electrodes

conductive jelly and fixusing sticking plastics. The voltage generated by the pumping

action of the heart is actually a vector whose magnitude, as well as spatial orientation,changes with time. Because the ECG signal is measured from electrodes applied to the

surface of the body, the waveform of this signal is very dependent on the placement of

electrodes. To record the ECG pattern of a subject (human body) it is necessary to applyECG metal electrodes to the patient's limbs in special formats called leads, on each arm

and leg, and six electrodes are placed at defined locations on the chest. These electrode

leads are connected to a device that measures potential differences between selectedelectrodes to produce the characteristic electro-cardio-graphic tracings.

1. Limb Leads (Bipolar)2. Augmented Limb Leads (Unipolar)3. Chest Leads (Unipolar)


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Fig. 1.3Verify the algebraic relationship amongst units leads

Procedure: -

1. Connect the Heart-rate monitor cum ECG Trainer ST2351 to AC mains.2. Switch ON the trainer by Mains switch.3. Now place the electrodes in Lead I of standard Bipolar lead configuration

Positive electrode (yellow) in left arm of subject, negative electrodes (Red) in

right arm, and common (reference) electrode (Black) in the right leg of subject

properly with ECG Gel and connect the cables to the kit.

4. Observe the ECG waveform in Lead I configuration at test-point Amplifier block(TP3) of trainer. (Adjust gain of the amplifier if required). Or Make a serial

Connection between RS232 port on Training kit and RS232 port (COM1)

available on PC. And observe the waveforms and analyze them with Real time

ECG Analysis Software.

5. Then observe ECG waveforms at outputs of the different blocks of Heart-ratemonitor cum ECG Trainer ST2351.


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Fig. 1.4Real Time ECG Analysis Software

Heart-rate monitor cum ECG Trainer ST2351 provides in-depth study of

Electrocardiogram), ECG standard leads configuration, and the measurement of heart ratei.e. number of ECG pulses (heartbeats) per minute. ST2351 enables the

Electrocardiogram observation by affixing Biomedical Electrodes to the human body in

standard bipolar leads configuration. The Heart-rate monitor receives each ECG

observation (heartbeat) i.e. detects the electrical action executed by heart of subject(human body) and displays the heart-rate as number of heartbeats per minute. ST2351

also monitors the abnormalities occurs in human cardiovascular system tachycardia(faster heart-rate) and Bradycardia (slower heart-rate) using visible controls. It also

facilitates real time acquisition of raw data (ECG) and their corresponding measurementsby its real time Analysis Software.

Result: - Thus we have obtained Electro Cardio Gram (ECG) of a resting humansubject, verify the algebraic relationship amongst units leads and also monitor heart rate.

To Obtain ECG of a Resting Human Subject and Verify the Algebraic Relationship

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