Hello, Thanks for the query to H.C.M. Forum. Sleep apnea is defined as an intermittent cessation of airflow at the NOSE or MOUTH. Cessation of airflow means sudden stoppage of breath. two types 1 Central , in this the neural drive to all the respiratory muscles is transiently abolished. It means nerve supply of respiratory muscles stops so cessation of breath. This type of sleep apnea is transient and self limiting , require , no treatment. 2 OBSTRUCTIVE SLEEP APNEA. This is occlusion of upper airway usually at the level of OROPHARYNX ( union of wind pipe with inside of mouth). Due to cessation of breath there develops asphyxia ( sudden feeling of suffocation ) and this causes arousal from sleep i.e that s why we call it sleep apnea. In simple in patient of sleep apnea ( obstructive) there is generation of a critical subatmospheric pressure during inspiration that exceed the ability of airway dilator to maintain stability. In simple , we can say in wakeful condition this is possible ,but when patient is in sleep activities of muscles reduces hence airway airflow is not maintained and cessation of breath. Why this occurs , the structure is a natural thing so this develops in few persons. You have to consult an E N T . Hope I have answered your question. If further any question I will help. Good luck. DR. HET.