Sleep apnea surgery
Sleep apnea has been de fined as cessation of airflow at the level of nostrils and mouth lasting at least ten seconds.A sleep apnea syndrom is diagnosed if ,during seven hours of noctural sleep ,at least thirty apnoeic eleeppisodes are observed in both rapid eye moement sleep,some of which must appear in NREM sleep.It is frequently more convenient to use an apnea index of then umber of apneas per sleep-hour:using this notion five apnea /hour or more are needed to diagnose a sleep apnea syndrom
Pathological sleep apnea is classified a central,obstructive or mixed.In central apnea there are no respiratory movements.In obstructive apnea there is no airflow despite persistent respiratory effort,with paradoxical movements of chest and abdomen in an attempt to ovecome the upper airway obstruction.In mixed apnea there is initially no airflow or respiratory effort,but after an interval respiratory effort is resumed and eventually re-establishes airflow
Normal sleep
Respiration while awake is mainly under voluntary control,but during sleep mechanisms assume greater impotence.At the onset the sleep,respiration is often irregular with short apneic episodes.AS sleep becomes deeper,breathing respiration becomes more regular.During REM sleep ,howevere,there is decreased muscle tone with diminished responsiveness to hypoxia,hypercapnia and airway obstruction:there is an associated drop in oxygen saturation and a rise in PaCO2 with irregular respiration and occasional apneic episodes
Pathophysiology and aetiology
Obstructive apnea is caused by obstruction of the upper airway ,and the possible causes are the same as those already discussed .It is this type of sleep apnea which is most likely to present to the otolaryngologist.Fluroscopy and fibroptic nasoendoscopy have demonstrated that most episodes of obstructive sleep apnea are caused by pharyngeal collapse in patients in whom