The main types of sleep apnea are: Obstructive sleep apnea (OSA), which is the more common form that occurs when throat muscles relax and block the flow of air into the lungs Central sleep apnea (CSA), which occurs when the brain doesn't send proper signals to the muscles that control breathing Treatment-emergent central sleep apnea, also known as complex sleep apnea, which happens when someone has OSA — diagnosed with a sleep study — that converts to CSA when receiving therapy for OSA