<unk>  is characterized by incomplete lung expansion leading to diminution of lung volume. It affects the whole lung or a part of it.<unk>  may be classified based on etiology into obstructive and non-obstructive types. Obstructive<unk> , which is the most common type of<unk>  may develop due to obstruction by foreign bodies, tumors and mucus plugs. Causes of non obstructive<unk>  include lung scarring caused by necrotizing pneumonia or granulomatous diseases, lung infiltration, extrinsic lung compression and diminished levels of surfactant. The most common cause of<unk>  is postoperative<unk> , due to the effect of surgical manipulation or general anaesthesia on the patient. Chest trauma, general anaesthesia, thoracic surgery, cystic fibrosis, prematurity and respiratory distress syndrome are some of the common risk factors that predispose patients to developing<unk> . Common symptoms of<unk>  include breathlessness, chest pain, and cyanosis. Symptoms in patients with<unk>  depend upon rapidity of bronchial occlusion, lung area affected and presence of any overlying infection. Physical examination of patients with<unk>  is usually remarkable for decreased chest expansion, mediastinal displacement towards the affected side and elevation of the diaphragm. Patients may develop dullness to percussion over the involved area, wheezing and diminished or absent breath sounds on auscultation. An x-ray may be helpful in the diagnosis of<unk> . Findings on an x-ray suggestive of<unk>  include displacement of fissures, rib crowding, elevation of ipsilateral diaphragm, volume loss on ipsilateral hemithorax, hilar displacement and compensatory hyperlucency of the remaining lobes. CT scan of the chest without contrast is the gold standard diagnostic modality.The primary treatment for<unk>  is management of the underlying cause. Besides this, supportive therapy for<unk>  includes chest physiotherapy, breathing and coughing exercises, early ambulation, nasotracheal suctioning, humidifiers, nebulized bronchodilators and supplemental oxygen in order to maintain an arterial oxygen saturation of greater than 90 percent. Intubation, mechanical support, positive pressure ventilation and continous positive airway pressure (CPAP) help in the prevention of alveolar collapse, thereby assisting in lung inflation in patients with<unk> .
Atelectasis
Pleurisy
Emphysema
Trapped lung
Pleural effusion
Hydrothorax
Round pneumonia
Atypical pneumonia