Apneas, Hypopneas and OSA
Similarly in people with OSA the airway muscles relax too much, however the airway narrowing is more significant than in snoring and causes a slight or full reduction in airflow to the lungs. A partial airway collapse associated with a reduction in airflow is called a "hypopnea". A complete airway collapse associated with complete cessation of airflow to the lungs is called an "apnea".
When the airway is blocked OSA sufferers will wake either partially or completely to breathe again. This can occur up to several hundred times a night, causing severe disruption to their sleep and daytime sleepiness. Often the sleeper is completely unaware of these repeated awakenings and it is the bed-partner that observes them struggling for breath in their sleep. However, some people may experience a feeling of choking or gasping for breath. Untreated OSA may lead to serious health problems such as high blood pressure, heart attack and stroke. The daytime sleepiness can also lead to road or workplace accidents.
(The terms hypopnea and apnea are derived from the Greek words "HYPO", meaning below normal, "A", meaning absence or lack of, and "PNEA", meaning to breathe. (literally "below normal breath" and "absence of breath").