How do lower HFF settings affect the waveforms?

Lower high-frequency filter (HFF) settings in polysomnography can significantly impact the appearance of waveforms recorded during sleep studies. When HFF settings are lowered, the higher frequency components of the waveform are attenuated. This results in a "rounder" appearance of the waveforms, as the sharper edges of the higher frequency activity are smoothed out.

In sleep studies, this effect can be particularly important for accurately interpreting brain activity, as it can alter the representation of various sleep stages and artifacts. For instance, during sleep, brain waves like sleep spindles or sawtooth waves can appear less distinct under lower HFF settings, leading to a more rounded and less defined waveform shape. This is critical to understand, as it affects how clinicians interpret sleep data and diagnose conditions related to sleep disturbances.

The impact of HFF settings highlights the importance of proper filter settings in electrophysiological recordings, aiding in obtaining clear and interpretable data.