Data Acquisition, Recording, and Documentation
Core concepts
Data acquisition covers the polysomnographic montage, filters, sensitivity, sampling rate, and documentation. Know the purpose of each channel: EEG for staging, EOG for eye movements, chin EMG for muscle tone, ECG for rhythm, airflow and effort for respiratory events, oximetry for oxygen saturation, and sensors for snore, position, and limb movements. Filters shape the display: a low-frequency filter removes slow baseline sway; a high-frequency filter removes fast artifact; a 60 Hz notch filter reduces electrical interference. Sensitivity affects displayed amplitude, not the underlying signal. Recognize common artifacts: 60 Hz electrical interference, sweat artifact with slow sway, ECG artifact in EEG or EMG channels, pulse artifact, and snore vibration. Document calibration, interventions, technical problems, and signal changes with times. Never fabricate or backfill data.
Traps
Do not confuse filter changes with real physiological changes. A sensitivity change can make EEG look higher in amplitude without any change in the patient. Do not document an event after the fact without a time reference. Avoid adjusting settings to “hide” artifact; correct the source. A question may ask what to do first for 60 Hz artifact-check impedance and ground before changing filters.
Worked example
A technologist sees 60 Hz artifact in multiple channels. Check electrode impedance and the ground or reference connection, and re-prep if needed. If artifact persists, verify nearby electrical equipment.
Rule of thumb
If a signal looks wrong, troubleshoot the source-contact, cable, or equipment-before changing display settings, and document what you did.