Stages 2 and 3 are deeper sleep, and associated with delta waves
on the EEG.
Delta: Delta waves
tend to be slower and are often associated with deep dreamless, restorative sleep.
Stage 3 sleep is characterized by 20% to 50% delta waves
, and stage 4 has more than 50% delta waves
After cardioversion, ECG revealed sinus rhythm, short P-R interval, wide QRS complex and typical delta waves
of WPW syndrome.
The deepest stages, namely 3 and 4, which correspond to slow wave sleep (SWS), are characterized by the production of delta waves
, which are recognized as a key component of sleep quality.
from 0-4Hz represent sleep, Theta waves between 4-8Hz represent drowsiness, Alpha 8-12Hz has a relaxed focus.