- Apnea Hypopnea Index>5 in a PSG study with daytime symptoms. Apnoea = period of complete cessation of oronasal airflow for minimum of 10s; period of more than 50% reduction of oronasal airflow with a decrease of more than 3% of ongoing saturated O2 = hypopnea.
- recurrent sleep-induced collapse of the pharyngeal airway leading to hypoxaemia, hypercapnia, with arousal from sleep required to re-establish airway patency
- Obstructive: continued/raised diaphragm EMG activity and/or thoracoabdominal wall movement; thoracoabdominal paradox may be present
- Central: absent diaphragm EMG and thoracoabdominal movement
- Mixed: components of both