Sleep apnea is an involuntary cessation of breathing during sleep. There are three types of sleep apnea: obstructive, central, and mixed. OSA occurs when the patient's breathing efforts are intact but air movement is blocked by a temporary obstruction. Central sleep apnea is characterized by the absence of any breathing effort and is associated with brain disease rather than airway blockage. Mixed sleep apnea combines characteristics of both central and OSA types.