Polysomnography PSG a.k.a. sleep study:
What is recorded:

  • Eye movements: REM vs Non-REM
  • EMG (submental or limb): tone
  • Electroencephalography (EEG): alpha and theta activity
  • O2 saturation
  • +/-Video

Normal REM sleep:

  • REM Rapid eye movements
  • EMG: minimal to no EMG tone
  • EEG: mixed alpha and theta activity


  • Hypopnea: 10 seconds of decrease in airflow for <10 secons by >50%. Or decrease in airflow <50% with arousal. Or decrease in airflow <50% with 3% desaturation.
  • Apnea: decrease in airflow =or>80% for 10 seconds.
  • Obstructive apnea: apnea that occurs with continued respiratory effort.
  • Central apnea: apnea without continued respiratory effort
  • Hypoventilation: increased CO2