The collapse of the lung is called

Atelectasis (collapse) Atelectasis refers to:- Incomplete expansion of lungs → Neonatal atelectasis. or The collapse of previously inflated lung → Acquired atelectasis. This results in areas of relatively airless pulmonary parenchyma. Acquired atelectasis may be divided into 1.   Resorption (obstruction) atelectasis It is a consequence of complete obstruction of an airway. With time trapped oxygen in the affected alveoli is resorbed and collapse occurs. Resorption atelectasis is caused principally by obstruction due to excessive secretions (mucus plug) or exudates within small bronchioles as seen in Bronchial asthma, chronic bronchitis, Bronchiectasis and foreign body aspiration. 2.   Compression atelectasis The collapse of lung occurs due to external pressure on the lung. It is seen most commonly in patients with cardiac failure who develop pleural effusion and in patients with neoplastic pleural effusion. 3.   Contraction atelectasis The collapse is due to contracture in the lung because of fibrotic changes. Except for contraction atelectasis, atelectasis is a reversible disorder, i.e. collapsed lung parenchyma can be re-expanded.