This is an excerpt from Laboratory Assessment and Exercise Prescription With HKPropel Online Video-Loose-Leaf Edition by Jeffrey M. Janot & Nicholas M. Beltz.
The main source of error with client preparation and electrode placement lies with the technician. The first step to ensuring a good and accurate representation of the client’s ECG tracing is skin preparation. If the steps involved in this task are not followed and performed correctly, the amount of interference and artifact on the ECG will affect the quality and clarity of the recording. If there is too much artifact, it will be difficult to accurately interpret the ECG either on the screen or on paper. A repreparation of the client will need to be done to address any artifact issues. Time and material cost is an issue in this case; thus, prepare the client correctly the first time.
Electrode placement and correct lead wire connection is the next issue affecting the accuracy of the ECG recording. Anatomical landmarks (much like for skinfold measurements) are used to standardize the placement of electrodes in order to obtain the correct representation of the individual client’s cardiac electrical activity and function. The ECG guidelines presented in the following section are largely based on correct electrode placement. If electrodes are placed in the wrong location, this can ultimately affect how the ECG is recorded and interpreted. Additionally, ensure that each lead wire is connected to the correct electrode following initial placement. It is recommended to identify the correct lead wire from the diagram on the ECG wire housing (the place where all wires originate from) and match that to the electrode of interest. The first sign of a mix-up of lead wires and their electrodes will be a very strange looking ECG.
Why is all of this so important to do correctly? In cases when physicians or other healthcare providers are using an ECG to diagnose disease or determine underlying causes of chronic conditions, it is essential to have the most accurate information possible. Thus, it is very important that you practice ECG electrode placement and that care is taken to follow all procedures of preparation and placement to get the best result.
Other minor sources of error include electrocardiograph setup prior to assessment. Make sure that recordings are set to standard gain or calibration of 10 mm/mV and paper speed of 25 mm∙s−1, which can be checked either on the machine or on most printed ECGs. Fortunately, these standard settings are the default setup for electrocardiographs. Various errors involved with the actual interpretation of the ECG recording will be discussed as necessary in the following sections.