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Operating the Electrocardiograph

Before running the ECG, remind the patient to remain as still as possible and not to talk. Be sure the patient is comfortable. A comfortable patient is less likely to move around and cause artifacts on the ECG tracing.

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Standardizing the Electrocardiograph

Follow the steps described in Procedure 52-1 if you need to standardize the electrocardiograph. Some machines have automatic standardization. The stylus should move upward above the baseline 10 mm (two large squares) when you press the standardization button. If it does not, you must see to it that the instrument is adjusted before continuing.

Running the ECG

You can now run the ECG. On most machines, turning the lead selector to the automatic mode produces a standard 12-lead strip. Because each lead provides a specific view of the heart's electrical activity, each of the 12 leads has a characteristic tracing (Figure 52-10).

Figure 52-10.
The tracing from each lead will differ. The long tracing of a single lead along the bottom is the rhythm strip.
Source: Courtesy of Cardiac Science Corporation, Milton, Wisconsin.
Manual ECGs.

If your office has a machine without an automatic setting, you must manually run the ECG for each of the 12 leads. You may also be required to repeat certain leads manually if artifacts are detected. Most of the ECG machines are able to run single channel or multichannel ECGs.

To run a manual ECG, standardize the machine as already outlined. Then turn the lead selector to standby mode. Some older machines may require you to stop the paper before selecting the first lead (I) using the lead selector. Push the marking button on the machine to indicate the lead if the machine does not do this automatically. Allow the strip to run for four to five cardiac cycles, taking about 3 to 5 seconds. Turn the machine back to the standby mode; stop the paper if necessary, and repeat the procedure for leads II and III, the augmented leads, and the precordial leads. Remember to standardize the machine for consistency before running each lead.

Many physicians request another strip on lead II to assess for rhythm. Some physicians choose a different lead for the rhythm strip. Run the rhythm strip on the requested lead to produce a strip that is at least 2 feet long so rhythmic abnormalities can be easily recognized.

Multiple-Channel Electrocardiographs.

Some electrocardiographs have multiple channels that can record three, four, or six leads simultaneously (Figure 52-11). Electrode placement is the same for these types of electrocardiographs.

 
Figure 52-11.
Some electrocardiographs allow you to run six leads at the same time.
Source: Courtesy of Cardiac Science Corporation, Milton, Wisconsin.
Checking the ECG Tracing

After running the 12 leads and before disconnecting the patient from the machine, check all tracings to make sure they are clear and free of artifacts. If any of the leads do not appear on a tracing, it may mean that a wire has come loose. In this case reconnect the wire, and repeat the tracing. Repeat any tracings that are not clear.

Also check that all tracings are contained within the boundaries of the paper and that no waves peak above the edges of the paper. If this happens, recenter the stylus if it is positioned too high, or set the sensitivity selector to ½ before repeating the tracing. In the reverse situation—where very low peaks appear—set the sensitivity selector to 2 to increase the height of the peaks.

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If the peaks in a tracing are too close together, increase the paper speed to 50 mm per second. Increasing the speed separates the peaks and makes the tracing easier to read.

Make a note on the ECG tracing whenever it is necessary to adjust sensitivity or speed settings. This information is vital to the interpretation of the test.