Author: Sat Sharma, MD University of Manitoba eMedicine Editor: Morley Lertzman, MD University of Manitoba BACKGROUND A 78-year-old woman with a prolonged history of chronic obstructive pulmonary disease is admitted to the hospital with an exacerbation of the disease and respiratory failure. What is the diagnosis? Hint The resident physician performed thoracentesis, which was unsuccessful. Answer Complete left lung collapse: The patient has a complete collapse of the left lung. On bronchoscopy, thick mucus plugs were removed from the left mainstem bronchus. In a complete lung collapse, complete opacification of the hemithorax is observed. The opposite lung hyperinflates, and the mediastinum herniates to the collapsed side. Misguided attempts at thoracentesis invariably fail, and urgent bronchoscopy is required. This radiograph also shows concomitant collapse of the right lower lobe.