Sleep apnea is a condition in which breathing is temporarily suspended during sleep. There are several forms of sleep apnea, including central, complex and obstructive sleep apnea, of which the latter is the most common. Obstructive sleep apnea (OSA) may involve two different types of breathing interruption: apnea and hypopnea. Apnea occurs when the upper airway becomes obstructed due to collapse of the muscles and soft tissues of the throat during inspiration. Hypopnea is said to occur when the blockage is only partial, resulting in a significant reduction in airflow.