A complex lipoprotein lining the air sacs in the lungs, which stabilises the
alveoli (i.e., the small gas-exchange units in the lungs) against collapse and enhances expansion of lungs during inhalation. Some preterm infants lack a sufficient amount of this substance, thus affecting respiratory function. Its application can reduce the need for supplemental oxygen and ventilatory support
. See Alveoli, Preterm infant, Respiratory distress syndrome (RDS)