Page 185 - Critical Care Nursing Demystified

170 CRITICAL CARE NURSING DeMYSTIFIED

reversed the electrodes, the waveform would be negative. That is not so hard.
So the first thing is that we are looking at these waveforms created by the heart
and looking for positive, negative, or baseline forms.

The ECG Paper
Next, we examine the ECG paper. It runs out of the monitor in grids that have
little tiny squares on them. Each square (horizontal axis) across means time, but
it is in small amounts of time—0.04 seconds. Each up and down square or ver-
tical square is in measurements of voltage or strength. Each tiny box up or
down is 0.1 millivolt. WOW! That is really small, is not it?
Look at Figure 4–2. You will need to commit those values to memory. Since
we will spend most of the time on the horizontal axis you will get really good at 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.

0.5 mV Bigger
(Tall) box

Little
0.1 mV box
(Tall)

0.04 seconds
(Wide)

0.20 seconds
(Wide)
FIGURE 4–2 • Those little and bigger boxes.