Hypopnea is typically defined by a decreased amount of air movement into the lungs and can cause hypoxemia (low levels of oxygen in the blood.)
It commonly is due to partial obstruction of the upper airway, but can also have neurological origins in central sleep apnea.
The combined number of apnea and hypopnea events that occur on average per hour during sleep is noted using the Apnea–hypopnea index (AHI).
The periods of silence can last 20 seconds or longer and can happen many times each hour, resulting in poor sleep and reduced levels of oxygen in the blood.
Other symptoms of hypopnea may include depression, forgetfulness, mood or behaviour changes, trouble concentrating, loss of energy, nervousness, and morning headaches.
Hypopnea is a disorder that may result in excessive daytime sleepiness and compromised quality of life, including traffic accidents, diminished productivity in the workplace, and emotional problems.
Among the causes of hypopnea are: In the context of diagnosis and treatment of sleep disorders, a hypopnea is not considered to be clinically significant unless there is a 30% or greater reduction in flow lasting for 10 seconds or longer and an associated 4% or greater desaturation in the person's O2 levels, or if it results in arousal or fragmentation of sleep.
However, this closure is still enough to cause a physiological effect i.e., an oxygen desaturation and/or an increase in breathing effort terminating in arousal.
Depending on the cause of obstruction, surgery may focus on the soft palate, the uvula, tonsils, adenoids or the tongue.
The most common treatment for this form is the use of non-invasive ventilation such as a bilevel positive airway pressure (BPAP) machine.