Table 2: Types of Sleep Studies.

Level I	Standard PSG, includes EEG (frontal, central and occipital derivations), EOG, chin EMG, ECG and recordings of airflow, respiratory effort, oxygen saturation, and limb EMG; a technician is in constant attendance
Level II	Comprehensive portable PSG is the same as Level I except that a heart rate monitor can replace the ECG and a technician is not in constant attendance
Level III	Modified portable sleep apnoea testing is a cardiorespiratory study that includes ventilation (at least two channels of respiratory movement or respiratory movement and airflow), heart rate or ECG, and oxygen saturation
Level IV	Continuous (single or dual) bioparameter recordings where devices that measure a minimum of one parameter, usually oxygen saturation, are used

EMG = electromyogram; EOG = electrooculogram; PSG = polysomnography. Source: Jafari et al.[¹⁶]