The job of the sleep tech is to produce a quality sleep study. When evaluating a PSG one should expect to see clean, artifact free tracings in all channels throughout the duration of the study. Some distortion of tracings can occur during patient movement, however, it should not be dominating – causing problems identifying and scoring sleep stages.
Accuracy of sleep recordings depend on 3 basic principles:
- quality of input signals
- precise equipment calibration
- on-line evaluation, artifact recognition, and maintenance of the sleep recording
Things that can result in poor quality tracings and recording artifacts:
- patient movement
- position changes
- sweat
- electrical interference
- disconnected sensors, etc.
Artifact slideshow with EEG examples:
CHECK LIST FOR HIGH QUALITY SLEEP RECORDINGS
- lab environment free of excessive electrical interference and all equipment grounded
- PSG and ancillary equipment should have routine checks for malfunctions and leakage current
- all power cords lengths kept to a minimal and plugged directly into their own AC wall receptacles
- Electrodes and sensors made of high quality material / proper condition
- Patients head measured according to 10/20 measuring system
- electrode sites adequately prepared and checked for low and relatively equal electrode impedances (The resistance to the flow of current through the electrical circuit)
- electrodes and sensors securely attached to patient
- lead and cable connections intact, and input signals correctly routed to appropriate amplifiers
- cabling to PSG machine intact
- equipment and patient calibrations clearly documented
BIO CALIBRATIONS
Bio calibrations are a sequence of tests used to verify and document appropriate responses and reliability of electrode and sensor application.
Serves as a baseline scoring reference, representative of patients unique waveform.
Before starting, ask patient to relax and lie still. Test intercom, observe patient on video.
If results unclear, have patient repeat.
Check potential problems such as loose electrodes, dislodged sensors, 60Hz interference, excessive ECG artifact with the EEG, EOG, or EMG channels, application breakdown, or equipment malfunction.
SAMPLE BIO CALIBRATION ROUTINE
- relax and keep your eyes open (30 seconds)
- without moving your head, look to the right (30 sec), look left (30 sec)….repeat
- without moving head, look up….look down….look up….look down
- slowly and distinctly blink your eyes 5 times
- clench your jaw and grit your teeth
- flex or extend your right foot
- take a couple of slow breaths, inhale…exhale….etc.
- while remaining still, take a breath and hold it for 10 seconds
- close your eyes and relax without sleeping (record for 30 sec)
- pretend you are doing a stomach crunch/sit up
Polysomnography Study Guide 