Blood oxygen levels during sleep should be at a 95 percent saturation, which is considered normal, according to the American Sleep Apnea Association. A saturation of 86 percent rates as mild, while 80 to 85 percent is moderate, and 79 percent or less rates as severe. Sleep apnea occurs when airflow reduces by 80 percent. An airflow reduction to 50 to 80 percent qualifies as a hypopnea episode.
Blood oxygen levels are naturally lower during sleep, explains the University of California San Francisco Medical Center. Tests that show a waking oxygen level at or above 94 percent typically indicate a sleep oxygen level of at or above 88 percent. However, a doctor may order an overnight pulse oximetry test to determine if a patient has sleep apnea or other related disorders.
Pulse oximetry testing can be conducted in a clinical atmosphere or at home, depending upon the patient's medical history, claims RT Magazine. A diagnosis of obstructive sleep apnea-hypopnea syndrome results from multiple episodes of hypopnea, or airflow reduction, explains Mayo Clinic. It can also be caused from cessation, or the collapse of an upper airway during sleep. Conditions that can lead to obstructive sleep apnea-hypopnea syndrome include retrognathia, deviated nasal septum, low-lying soft palate and an enlarged uvula.