Obstructive apnea: At least a 90% drop in peak signal excursion of the oronasal thermal sensor in the presence of continued respiratory effort lasting longer than 2 respiratory cycle times.
Central apnea: At least a 90% drop in peak signal excursion of the oronasal thermal sensor in the absence of respiratory effort and at least one of the following: (1) ≥ the event lasts 20 seconds; (2) the event lasts at least 2 respiratory cycles and is associated with ≥ 3% oxygen desaturation; or (3) the central event lasts at least 2 respiratory cycle times and is associated with heart deceleration.
Mixed apnea: Criteria for apnea need to be met for at least 2 respiratory cycles and associated with absent respiratory effort during one portion of the event and inspiratory effort in another portion.
Hypopnea: All the following three criteria need to be met: (1) at least 30% decrease in the amplitude of the nasal pressure signal; (2) duration ≥ 2 respiratory cycles times; and (3) ≥ 3% oxygen desaturation or the event is associated with arousal.
Obstructive hypopnea: To score hypopnea as obstructive, the following need to be met: (1) snoring during the event; (2) increased inspiratory flattening of the nasal pressure flow signal compared with baseline breathing; and (3) associated thoracoabdominal paradox occurs during the event but not during pre-event breathing.
Hypoventilation: Criteria are met when end-tidal CO2 (PETCO2) >50 mmHg persists for more than 25% of total sleep time.
Apnea index (AI): Number of obstructive and/or central apneic events per hour of sleep.
Obstructive apnea index (oAI): Number of obstructive apneic events per hour of sleep.
Hypopnea index (HI): Number of hypopneas per hour of sleep.
Apnea/hypopnea index (AHI): The summation of apnea index and hypopnea index.
Obstructive apnea/hypopnea index (oAHI): The summation of obstructive apneic events and hypopneic events per hour of sleep.
