hypopnea

Hypopnea is a sleep-related breathing disorder characterized by a partial reduction in airflow during sleep. An event typically lasts at least 10 seconds and is accompanied by a decrease in blood oxygen saturation and/or an arousal from sleep. Hypopneas are counted along with apneas to form the apnea–hypopnea index (AHI), which is used to classify the severity of sleep-disordered breathing. Unlike apnea, which is a complete or near-complete cessation of airflow, hypopnea reflects partial obstruction or reduced respiratory effort.

Hypopneas are most commonly associated with obstructive sleep apnea, in which the upper airway collapses or narrows during sleep. They can also occur with central sleep apnea, where the brain's drive to breathe is reduced. Risk factors include excess body weight, male sex, aging, craniofacial anatomy, nasal obstruction, and certain neuromuscular conditions. Positional and alcohol use can worsen hypopneas.

Diagnosis is usually made by overnight sleep testing, such as polysomnography or home sleep apnea testing. The criteria for hypopnea vary by guideline; many definitions require a ≥30% reduction in airflow for ≥10 seconds with a ≥3% or ≥4% desaturation, or an associated arousal.

Treatment targets airway patency and symptom relief. First-line therapy for significant hypopnea related to obstructive sleep apnea is continuous positive airway pressure (CPAP) therapy. Alternatives include bilevel PAP, oral appliances, weight loss, positional therapy, and, in select cases, surgery. Management of comorbid conditions, such as hypertension or atrial fibrillation, is also important. The prognosis depends on severity and comorbidity, but effective treatment reduces symptoms and cardiovascular risk.