Sudden onset of cough followed by increased dyspnea is typical of-

Causes of pneumothorax: 1. Primary spontaneous: a)rupture of apical blebs b)smokers 2.secondary : a)copd and any other lung disease 3. Traumatics secondary to thoracentesis,central intravenous catheters 4.tension pneumothorax: during mechanical ventilation may cause decreased venous return and decreased cardiac output.