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.
Central sleep apnea. Central sleep apnea is a sleep disorder in which breathing stops over and over during sleep. Central sleep apnea results when the brain temporarily stops sending signals to the muscles that control breathing. The condition often occurs in people who have certain medical problems.