amnion. the innermost fetal membrane, which forms a sac filled with amniotic fluid that surrounds the embryo and later the fetus; as it enlarges it gradually obliterates the chorionic cavity and enfolds the umbilical cord. Called also bag of waters.
cluster breathing. cluster breathing. a breathing pattern in which a closely grouped series of respirations is followed by apnea. The activity is associated with a lesion in the lower pontine region of the brainstem. See also Biot's respiration, Cheyne-Stokes respiration.
Sleep apnea (or sleep apnoea in British English) is a sleep disorder characterized by pauses in breathing or instances of shallow or infrequent breathing during sleep. Each pause in breathing, called an apnea, can last for several seconds to several minutes, and may occur, by definition, at least 5 times in an hour. Similarly, each abnormally shallow breathing event is called a hypopnea.