What is the primary purpose of the low-frequency filter in polysomnography?

The primary purpose of the low-frequency filter in polysomnography is to eliminate undesired slow frequencies. This is crucial in sleep studies where it is essential to accurately capture and analyze the relevant brainwave activity, as well as any associated physiological signals. The low-frequency filter helps to reduce artifacts that may arise from slow movements or physiological activities, such as muscle tension or breathing irregularities, which can compromise data quality. By filtering out these unwanted slow frequencies, technicians can focus on the significant frequency bands that correspond to various sleep stages and maintain the integrity of the recordings used for diagnosis.

In contrast, eliminating undesired fast frequencies, adjusting signal amplitude, and calibrating DC amplifiers serve different functions that do not specifically relate to the role of a low-frequency filter in enhancing the clarity and accuracy of sleep data.