Electrodes are central to all branches of electrotherapy. Their role is to facilitate the transmission of electric signals into the body. They do this by achieving a sound electrical contact between the patient’s skin and the device that is generating the electrical signal (TENS, ultrasound unit, etc).
In the broadest sense, medical practitioners use electrodes in four branches of electrotherapy – ECG, EEG, defibrillation and blood gas measurement. You can also classify them into four broad design categories – reusable disc, saline based, disposable and headband electrodes.
Probably the most important factor in choosing the correct electrode is size. The correct size in any particular case depends on the area of the body that will be treated. The main objective will be to make good electrical contact throughout the surface of the electrode. You may find that a smaller electrode works better on more contoured body areas. The shape of the electrode can also be an important factor in ensuring good electrical contact.