Page 183 - Critical Care Nursing Demystified

168 CRITICAL CARE NURSING DeMYSTIFIED

Next, a lead wire is attached to the electrode. This is done in many different ways.
Sometimes it is clipped on to the electrode by an alligator clamp. Yes, again you are
correct! It is called an alligator clamp because its jaws look just like an alligator. Be
careful not to pinch the patient’s skin when attaching these! Sometimes it is
snapped on to the electrode. If you use this type of system, try to snap the electrode
onto the lead wire before placing the electrode on the chest—attaching the lead to
an electrode already on the chest might cause the patient pain.
The next step is to connect the lead wire to a cable, which finally attaches
to the monitor or telemetry unit. So all of these pieces—the electrode, lead
wires, and cable—are just conductors! No real work has been done yet to “see”
the rhythm, but it is vital that these are checked periodically for proper attach-
ment to the patient, to see whether they are frayed or damaged, and to ensure
that the connections are tight.
The monitor does the real work of rhythm detection. It takes the electrical
energy in the form of those millivolts and converts it to mechanical energy that
we can analyze to tell if there are rhythm changes in the heart. That is essen-
tially how it all works.
Following is a summary of the jobs done by a cardiac monitoring system:
• Electrode – the conductor Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.
• Lead wires – further conductor
• Monitor – ultimate conversion tool
Not to confuse the issue when you think you have gotten it, but there are
different kinds of monitoring devices: hardwire, telemetry, and Holter monitors.
Table 4–2 describes the basic differences between these three systems.
These are not to be confused with a 12-lead ECG. (More on this later in the
chapter when you have got some analysis under your belt!) So get ready for
more experience with what happens.

So What Do These Systems “See”?

These systems pick up a series of small waveforms that we can analyze on spe-
cial paper called ECG paper. When the heart depolarizes and repolarizes, those
positive and negative charges cause waveforms to go up and down from the
flatline, which is called the baseline or also isoelectric line. It is very logical and
not hard at all. Positive electrical charges cause waveforms to go up and nega-
tive charges cause waveforms to go down (see Table 4–3).
When the waveform is traveling toward the positive electrode, it is positive;
when it is traveling toward the negative electrode, it is negative; and when it is
traveling toward neither or in the middle of the road, it is baseline or flat.