What does impedance measure in the context of electrodes?

Impedance, in the context of electrodes, measures electrical resistance between two points in a circuit. It is an important parameter in electrophysiological studies, including polysomnography, as it affects the quality of the signal collected from the electrodes placed on the skin.

When electrodes come into contact with the skin, the impedance can impact how well electrical signals from physiological processes—like brain waves, heartbeats, or muscle activity—are transmitted to the recording equipment. Lower impedance is generally desirable because it allows for better signal quality, reducing noise and improving the accuracy of the measurements.

The measurement of impedance provides insight into the integrity of the electrode-skin interface. Issues such as dried adhesive or improper placement of the electrodes can increase resistance, leading to higher impedance and potentially poor signal quality. Therefore, monitoring and managing impedance are essential aspects of obtaining reliable data in polysomnography.