How to operate electrocardiogram

I. Introduction

Electrocardiograph can automatically record the bioelectric signal (ECG signal) produced by myocardial excitement during cardiac activity, and has become a commonly used medical electronic instrument for clinical diagnosis and scientific research.

Cardiac electrophysiological function is closely related to ECG, and many cardiac electrophysiological dysfunction can be reflected from ECG.

When the heart keeps moving rhythmically, it will produce weak electrical signals and transmit them to all aspects of the human body. When the second brother electrode is placed on any different part of the human body surface, a variety of ECG signals can be obtained. The lead of ECG is how the electrode is placed in which part of the body and how the electrode is connected with the positive and negative electrodes of ECG.

At present, the ECG leads commonly used in clinic (Wilson network leads) include standard leads (I, II and III), pressurized unipolar limb leads (aVR, aVL and aVF) and chest leads (V 1 ~ V6). Abnormal leads include bipolar chest leads (CC, CL, CF), right chest leads (V3R, V4r...V8r), and V7 ~ V9, V' 1 ~ V' 5, VE lead, S5 lead, atrial lead (A lead), improved CL 1 lead (MCL

Second, the placement of ECG electrode matters needing attention:

1. Prepare the patient's skin. Because skin is a poor conductor, the contact between electrode and skin is very important in order to obtain good ECG signal.

-If necessary, please shave the hair off the electrode accessories.

-Thoroughly clean electrode accessories with soapy water. It is not recommended to use ether or ethanol, because they will dry the skin and increase resistance.

-Wipe the skin hard to make it completely dry, so as to increase the capillary blood flow in the tissue and remove useless skin debris and skin grease.

2. Before placing the electrode, place a clip or button on the electrode. If you don't use pre-bonded electrodes, please apply electrode glue before placing the electrodes.

3. Place the electrode on the patient according to the lead placement scheme you choose.

Three. Precautions for operation and use:

1. If any ECG waveform displayed is too small or clipped, you can change the size of one or all ECG waveforms on the screen. Changing the adjustment coefficient will only change the visual appearance of ECG waveform on the screen. It will not affect the ECG signal analyzed by the monitor. To change the size of all ECG waveforms on the screen with a fixed adjustment factor:

-amplitude x0.5 can halve the waveform size.

-Amplitude x 1 The waveform can be displayed without scaling.

-The amplitude x2 can amplify the waveform by 1 times.

The amplitude x4 can make the waveform four times larger.

2.ECG filtering settings define how to smooth ECG waveforms. Filtering reduces the interference to the signal. This setting is necessary if the signal is interfered by high frequency or low frequency.

-50 Hz AC interference

-35 Hz EMG interference

-100hz low frequency interference

Four, lead classification:

1. Standard leads I, II and III

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The left upper limb electrode is connected to the positive electrode of the ECG amplifier input, and the right upper limb electrode is connected to the amplifier.

Negative electrode, the potential obtained is the difference between the potentials of the two upper limbs. When the left upper limb potential is higher than the right upper limb potential, the traced waveform is upward, and vice versa.

(2) Lead II

The left lower limb electrode is connected to the input positive pole of the amplifier, and the right upper limb electrode is connected to the input negative pole of the amplifier. When the left lower limb potential is higher than the right upper limb potential, the depicted waveform is upward, and vice versa.

(3) Lead III

The left lower limb electrode is connected to the input positive pole of the amplifier, and the left upper limb electrode is connected to the negative pole of the amplifier. Dangzuo

When the lower limb potential is higher than the upper limb potential, the traced waveform is upward to prevent downward.

2. Pressurized unipolar limb leads

(1) aVR lead (pressing a single right upper limb lead)

The electrode of the left upper limb is connected to the input anode of the amplifier through a resistor, and connected to the changed central power station.

At the input cathode of the amplifier, the left upper limb electrode and the left lower limb electrode are respectively connected to the amplifier through resistors.

On the changed neutral power station.

(2) aVL lead (pressurized monopolar left upper limb lead)

The electrode of the left upper limb is connected to the input anode of the amplifier through a resistor, and connected to the changed neutral power station.

At the negative pole of the amplifier, the right upper limb electrode and the left upper limb electrode are respectively connected to the changed electrode through resistors.

At the neutral power station.

(3) aVF lead (pressurized monopolar left lower limb lead)

The electrode of the left lower limb is connected to the input anode of the amplifier through a resistor and connected to the changed neutral power station.

At the input cathode of the amplifier, the right upper limb electrode and the left upper limb electrode are respectively connected to the amplifier through resistors.

On the changed neutral power station.

3. Unipolar lead

(1) Lead V 1: The chest electrode is placed in the fourth intercostal space at the right edge of the sternum.

(2) Lead 2)V2: Place the chest electrode in the fourth intercostal space of the left sternum.

(3) Lead V3: The chest electrode is located at the midpoint of the connecting line between V2 and V4.

(4) Lead 4)V4: The chest electrode is placed between the left clavicle midline and the fifth rib.

(5) Lead 5)V5: The chest electrode is placed between the left axillary front line and the fifth rib.

(6) Lead 6)V6: The chest electrode is placed between the left axillary midline and the fifth rib.