This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardio thoracic surgery  , Subject name: Surgery
Heimlich valve is used for drainage of 
Select and explain. 
A. Pneumothorax, B. Hemothorax, C. Emphyema, D. Malignant plural effusion
A: Pneumothorax
Answer: A: Pneumothorax 
Explanation: The Heimlich valve(flutter valve)is a small one-way valve used for chest drainage that empties into a flexible collection device & prevents return of gases or fluids into the pleural space.The heimlich valve is less than 13 cm long and facilitates patient ambulation. Reference:SRB's manual of surgery,5th edition,page no:1116.