Obstructive Apnea Index with Arousal at 4% oxygen desaturation [(Total number of obstructive apneas associated with arousals or >= 4% oxygen desaturation) / (hours of sleep)]

RDI at 4% oxygen desaturation or arousal [(Total number of apneas and hypopneas associated with arousal or >= 4% oxygen desaturation) / (hours of sleep)]