Cleveland Family Study
17.16 PSG Equipment Care and Maintenance
17.16.1 Electrode Overview
The gold disk electrodes supplied by Compumedics are reusable and should last through many cycles of use. The electrode is made of metal (which conduct electrical signals from the patient into the recorder via a wire cable). Certain metals are more stable conductors than others. The gold disk electrodes used by the Compumedics equipment are made of a layer of gold over a silver core. The gold overlay provides for ease in cleaning and a wider variety of disinfection procedures than would an electrode consisting of pure silver. The weakest part of the electrode is the thin wire cable at the end of the gold disk. Since this wire is very thin and hidden by an opaque covering a broken, or bad, electrode may look perfectly fine yet yield distorted, inaccurate information. The best way to determine if the electrode is working correctly is through the impedance test after the electrodes are placed on the participant. If the electrode yields unsatisfactory impedance levels after proper troubleshooting it is most likely time to replace the electrode.
Since gold disk electrodes are expensive, certain things should be understood about how to obtain the longest life from them. The key points in maintaining your gold disk electrodes is to:
- Keep them clean.
- Disinfect between participants.
- Treat the wire and connection points with respect.
- Condition new electrodes before the first use.
17.16.1.1 Keep Gold Disks Clean
Between uses, the surface of the gold disk electrode must be kept free of dried electrolyte paste. An electrode with dried paste does not come into proper contact with the skin and creates an air pocket, which increases impedance and distorts the signal. Additionally, an electrode with visually crusted paste cannot be properly disinfected. Ensure the gold cup and the connection leading to the wire is free of crusted paste.
17.16.1.2 Disinfect Gold Disks Between Participants
Intact skin is naturally a protective barrier. The participant’s skin is prepared with an abrasive material before attaching the electrode. With abrasion the skin loses its integrity as the topmost layer is scratched or rubbed away; the skin is no longer intact. Any time the skin is abraded there is risk of blood borne pathogens even if blood, itself, is not visible. This is called occult blood. Reusable equipment that comes in contact with non-intact skin must be disinfected after use. Disinfection is the best measure to prevent transmission of disease from one participant to another. It is important to understand that there are different levels of disinfection: low, intermediate and high. The step above high-level disinfection is sterilization. Gold disk electrodes do not require sterilization. Gold disk electrodes require high-level disinfection between participants to eliminate the risk of transmitting blood borne pathogens from occult blood.
17.16.1.3 Treat Electrode Wires with Respect
The weakest part of the electrode is the thin wire cable at the end of the gold disk. The most vulnerable place for injury to the wire is the point it interfaces with the gold cup or the PIB. If the connection is loose at either of these places, the electrode cup may receive an adequate signal but it will never reach the recording unit successfully. Since this wire is very thin and hidden by an opaque covering a broken, or bad, electrode may look perfectly fine yet yield distorted, inaccurate information. The wires should be kept clean and free of crusty paste or sticky tape. If tape is used for the participant hook-up, or a gob of paste ends up on the wires, it should be removed and the wires wiped to remove any stickiness. Never pull excessively on the electrode wire or bend the wire near the point of connection to the gold cup or PIB. Do not wind the wire around any small objects that may cause the wire to kink. After use, any knots that may have formed in the wire should be removed, and the wires straightened. To keep the wires from kinking during storage, after disinfecting electrodes the wires may be wrapped and secured around a larger object, such as an empty plastic water or soft drink bottle. Wires that are knotted or kinky can increase impedance.
17.16.1.4 Cleaning and Disinfection Before the First Use
Electrodes are a durable object with a long shelf life. They may have been manufactured long before they are shipped to the user. If spare electrodes are ordered, they may be kept in storage for a long time before they are needed as a replacement. In order to keep a new electrode looking fresh until the first use, it is treated with a coating before being packaged. If you have ever used a brand new electrode without conditioning it you may have been puzzled as to why your impedances were just as high as with the broken electrode. Sometimes the patient, PIB or recording unit gets blamed. Condition new gold disk electrodes prior to the first use. Electrodes carried as spares in the equipment case should also be conditioned for ready use.
- To condition a gold disk electrode for the first use, lightly brush both sides (top and bottom of the cup) with a stiff nylon brush or hair comb. Brush a new electrode well.
- The gold disk can then be washed with a soapy solution and rinsed with warm water.
- Lastly the gold disk is placed in some electrolyte (or smear some conducting paste on both sides).
- Allow the electrolyte to remain on the gold disk for several hours (or overnight).
- After the electrolyte soak, rinse to clean with warm water and dry. The electrode is now ready for the first use.