Figure 3-6 Measuring distances on the ECG with calipers.
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Calipers: The Clinician’s Best Friend
In our opinion, it is almost impossible to interpret arrhythmias with any degree of accuracy if you do not use calipers (Figure 3-6). This is a strong statement, but it is true. It is possible to measure intervals and waves without calipers. It is even possible to evaluate consistency when you are evaluating the rhythm. We have seen people do all kinds of creative markings on pieces of paper to transfer the heights and widths of complexes. However, for accuracy and dependability, nothing beats the ECG calipers. If you don’t own a set, go to your nearest medical bookstore or drafting supply house to get one. Always have them with you when you work clinically. It will simplify your life.
Figure 3-6 Measuring distances on the ECG with calipers.
© Jones & Bartlett Learning.
REMINDER
When interpreting an ECG, always check the format! Make sure the rhythm strip is temporally related to the complexes above. (In some cases, it isn’t.)
How do you use the calipers? Place one of the pins at the beginning of the object you are measuring, and move the other pin to the end. Then you can transfer that distance to an uncluttered part of the ECG paper to evaluate the height or the time of the measured object. The following are some simple ways to use calipers.
Once you have measured the distance, it is easier to calculate the actual time frame on a cleaner, less cluttered area of the ECG paper (Figure 3-7). Remember, the big boxes are 0.20 seconds; there are two of these in Figure 3-7, for a total of 0.40 seconds. The small boxes are 0.04 seconds, and there are two and a half of these for a total of 0.10 seconds. Thus, altogether, the width is 0.50 seconds.
Figure 3-7 Total width of the complex is 0.50 seconds.
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DescriptionNow, suppose you want to see if the distance between three complexes is the same. First, measure the distance between complex A and complex B. Then, without lifting the right pin, swing the left pin to see if the distance from B to C is equal (Figure 3-8). By not moving the right pin, you are ensuring that the distances are the same. Swinging one pin over the other like this is called “walking.”
Figure 3-8 Walking the calipers. The distances are equal.
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DescriptionYou can walk the calipers back and forth across a strip to check the regularity of the complexes. You can also take that distance and move it anywhere you want on the paper. This technique is useful in determining third-degree heart blocks and many other ECG or rhythm abnormalities. Take your calipers and practice on some of the rhythm strips in the back of this book. Make sure you do some measurements as well.
Explaining this one is a bit of overkill, but we really want you to understand the usefulness of the calipers. Suppose you wanted to see if distance A is the same as or longer than distance B (Figure 3-9). Position the calipers to measure distance A, then move them—transferring the distance accurately—to see if B is the same.
Figure 3-9 Distances A and B are not the same.
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DescriptionYou will be using this technique for a great many comparisons in looking for atrioventricular blocks, aberrant beats, premature atrial contractions (PACs), premature ventricular contractions (PVCs), and so on. If you don’t know what those things mean, don’t worry about it; you will after you have read Chapter 7, How to Interpret a Rhythm Strip.