Naturally produced in the LUNGS by cells called pneumocytes, this substance is a mixture of phospholipids (see PHOSPHOLIPID) and LIPOPROTEINS. Present in fluid lining the alveoli (see ALVEOLUS) in the lungs, its action helps keep them open, rather than sticking together, particularly after breathing out. Premature babies may have a deficiency of surfactant, a disorder which causes severe breathing difficulties – RESPIRATORY DISTRESS SYNDROME or hyaline membrane disease – and HYPOXIA. They may need urgent respiratory support, which includes oxygen, artificial ventilation and the administration (via an endotracheal tube) of a specially prepared surfactant such as beractant (bovine lung extract) or edfosceril palmitate.