ECG EEG EMG | Difference btw ECG test,EEG test and EMG test

This page compares ECG, EEG and EMG machines and mentions difference between them. It also mentions ECG test, EEG test and EMG test conducted using ECG, EEG and EMG machines respectively.

ECG Machine Or EKG Machine

• ECG is the short form of Electrocardiogram.
• It can also be known by name EKG.
• The ECG machine is used to test irregularities in the way heart functions.
• It ECG test is conducted by placing skin electrodes on different parts of the human body.
• ECG test records the electrical activity of the heart muscle.

ECG test conducted using ECG machine

The figure-1 depicts waveforms in normal ECG pattern. This pattern repeats continuously on the screen of the ECG machine. The connections are probes placed on the body of the patients which interfaces with the ECG machine. Total 10 electrodes are used during ECG test viz. 4 are connected to left/right arms and left/right legs while 6 are placed on the chest. Here 10 electrodes constitute 12 leads.

As shown it consists of P wave, QRS complex, T wave and U wave. Following are the normal intervals in ms. This will help in interpreting or reading the ECG test report.
PR interval: Normally between 120 to 200 ms. It will be 3 to 5 squares ion ECG report.
QRS duration: range upto 120ms, 3 squares on ECG test report.
QT interval: range upto 440ms , it varies with rate of the heart and it is slightly longer in female compare to male.

Heart rate estimation using ECG test report

Each second is equivalent to say 250 ms (i.e. 5 squares of larger size).
Following table-1 mentions number of squares and their interpretation about Heart Rate (i.e. HR).

EEG Machine and EEG Test

• EEG is the short form of electroencephalogram.
• EEG test is used to help detect abnormalities in the brain by observing electrical activity.
• In EEG test, small size metal disc along with thin wires (i.e. electrodes) are used. These are placed on scalp and connected with computer. Figure-2 shows electrode cap with electrodes(about 10 to 12) placed on the scalp.
• The computer records the result in the form brain wave patterns.
• The entire EEG test takes about 20 to 30 minutes.
• It is painless method.

EEG test generates waves known as brain waves. They are divided into following four major groups based on frequency range. These are also referred as EEG bands. This bands help in analyzing different conditions of the brain based on age in the EEG test report.
Beta (> 13 Hz)
Alpha ( 8 to 13 Hz)
Theta ( 4 to 8 Hz)
Delta (0.5 to 4 Hz)

EEG test report can be used for following:
• To monitor coma or alertness condition or brain condition after injury or for analysis.
• Test epilepsy drug effects
• Monitor human/animal brain development

EMG Machine OR ELECTRO-MYOGRAPH

• EMG is the short form of Electromyography.
•  It is used to evaluate and to record electrical activity of skeletal muscles. It uses electrodiagnostic medicine based technique known as electromyography.
• The equipment detects electric potential as generated by muscle cells. In this EMG test, muscle cells are neurologically or electrically activated.
• During the test fine needle is inserted into muscle being tested.
• Presense, shape and size of waveform of potential is recorded.
• The EMG test recording is done while muscle is in rest condition as well as in contraction condition. As we know muscle fiber produces potential during contraction. The two electrodes are used surface and needle.

EMG test conducted using EMG machine

• The EMG test is performed using EMG machine.
• The result of record of EMG test is known as electromyogram.
• The test will help in analyzing medical abnormalities (if any) during recruitment or other contests.
• It is used to identify and analyze neuromuscular diseases.

All of these are biomedical equipments. Following table mentions functional difference between ECG, EEG and EMG machines.

Biomedical test and measurement equipments

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