Prepare the machine by placing the ECG machine close to the patient's bed, and plug the power cord into the wall outlet. To accommodate the precordial leads and minimize electrical interference on the ECG tracing, remove the electrodes if the patient is already connected to a cardiac monitor. Keep the patient away from objects that might cause electrical interference, such as equipment, fixtures, and power cords.
Explain the procedure to the patient as you set up the machine to record a 12-lead ECG. Tell him that the test records the heart's electrical activity and it may be repeated at certain intervals. Also, tell him that the test typically takes about 5 minutes. Emphasize that no electrical current will enter his body.
Have the patient lie in a supine position in the center of the bed with his arms at his sides. You may raise the head of the bed to promote his comfort. Expose his arms and legs, and drape him appropriately. His arms and legs should be relaxed to minimize muscle trembling, which can cause electrical interference.
Place the patient's hands under his buttocks to prevent muscle tension if the bed is too narrow. Also use this technique if the patient is shivering or trembling. Make sure his feet aren't touching the bed board.
Select flat, fleshy areas to place the electrodes. Avoid muscular and bony areas. If the patient has an amputated limb, choose a site on the stump. If an area is excessively hairy, clip it. Clean excess oil or other substances from the skin to enhance electrode contact.
Apply the electrode paste or gel or the disposable electrodes to the patient's wrists and to the medial aspects of his ankles. If you're using paste or gel, rub it into the skin. If you're using disposable electrodes, peel off the contact paper and apply them directly to the prepared site, as recommended by the manufacturer's instructions. To guarantee the best connection to the leadwire, position disposable electrodes on the legs with the lead connection pointing superiorly.
If you're using paste or gel, secure electrodes promptly after you apply the conductive medium. This prevents drying of the medium, which could impair ECG quality. Never use alcohol or acetone pads in place of the electrode paste or gel because they impair electrode contact with the skin and diminish the transmission quality of electrical impulses.
Connect the limb leadwires to the electrodes. Make sure the metal parts of the electrodes are clean and bright. Dirty or corroded electrodes prevent a good electrical connection.
You'll see that the tip of each leadwire is lettered and color-coded for easy identification. The white or RA leadwire goes to the right arm; the green or RL leadwire, to the right leg; the red or LL leadwire, to the left leg; the black or LA leadwire, to the left arm; and the brown or V1 to V6 leadwires, to the chest.
Now, expose the patient's chest. Put a small amount of electrode gel or paste on a disposable electrode at each electrode position.
If your patient is a woman, be sure to place the chest electrodes below the breast tissue. In a large-breasted woman, you may need to displace the breast tissue laterally.
Check to see that the paper speed selector is set to the standard 25 mm/second and that the machine is set to full voltage. The machine will record a normal standardization mark—a square that's the height of two large squares or 10 small squares on the recording paper. Then, if necessary, enter the appropriate patient identification data.
If any part of the waveform extends beyond the paper when you record the ECG, adjust the normal standardization to half-standardization. Note this adjustment on the ECG strip because this will need to be considered in interpreting the results.
Now you're ready to begin the recording. Ask the patient to relax and breathe normally. Tell him to lie still and not to talk when you record his ECG. Then press the AUTO button. Observe the tracing quality. The machine will record all 12 leads automatically, recording three consecutive leads simultaneously. Some machines have a display screen so you can preview waveforms before the machine records them on paper.
When the machine finishes recording the 12-lead ECG, remove the electrodes and clean the patient's skin. After disconnecting the leadwires from the electrodes, dispose of or clean the electrodes, as indicated.
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