Obstructive Sleep Apnea is caused by repetitive upper airway obstruction during sleep as a result of narrowing of the breathing passages.
When a person is awake the airway muscle tone helps to keep the airways patent. Decreased airway muscle tone during sleep, and the pull of gravity in the supine position, results in some prolapse of the airway structures and further decrease its size. This can impede airflow during respiration. Snoring can occur during the initial stages, caused by partial obstruction in the airway. As tissues collapse further or the patient rolls over on his or her back, the airway may become completely obstructed.
When the nature of obstruction is partial it is termed as hypopnea, whereas, a complete obstruction in the airway is called Apnea. Both hypopnea and apnea cause disruption in victims’ sleep several times during night, though the disturbance may go unrecognized by patients. The obstructive episodes are often associated with a reduction in blood oxygen levels.