Is there a condition it is related to? Such as COPD or Sleep Apnea? You may need to code the underlying condition with one of the codes below.
G47.36 - If it is sleep related you may consider G47.36 Sleep-related hypoventilation in conditions classified elsewhere or Sleep-related hypoxemia in conditions classified elsewhere. This will require an underlying condition.
R09.02 Hypoxemia- deficient oxygenation of the blood.
R09.89 - Other specified symptoms and signs involving the circulatory and respiratory systems.