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 is a breathing disorder that occurs during sleep and results when the brain fails to activate the respiratory muscles. This leads to a brief pause in breathing that may last 10 seconds or longer. Unlike the more standard obstructive sleep apnea - which is caused when the upper airway becomes temporarily obstructed - in central sleep apnea, the effort to breathe stops and there is no clear obstruction of the airway. Though the cause is slightly different, the outcome of central sleep apnea is the same.