The term atelectasis is derived from the Greek words ateles and ektasis, which mean incomplete expansion.The incomplete expansion of lung may involve part of lung or entire lung.Most symptoms and signs are determined by the rapidity with which the collapse of lung occurs,the size of the lung area affected, and the presence or absence of complicating infection. Rapid bronchial occlusion with a large area of lung collapse causes pain on the affected side, sudden onset of dyspnea, and cyanosis. Hypotension, tachycardia, fever, and shock may also occur. Slowly developing atelectasis may be asymptomatic or may cause only minor symptoms. Middle lobe syndrome often is asymptomatic, although irritation in the right middle and right lower lobe bronchi may cause a severe, hacking, nonproductive cough.

175. Middle lobe consolidation