This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
Muller manoeuvre is used in? 
Select and explain. 
A. To find out opening of mouth, B. To remove laryngeal foreign body, C. To find degree of obstruction in sleep disordered breathing, D. To remove foreign body from ear
C: To find degree of obstruction in sleep disordered breathing
Answer: C: To find degree of obstruction in sleep disordered breathing 
Explanation: Muller's manoeuvre: A flexible endoscope is passed through the nose and the patient asked to inspire vigorously with nose and mouth completely closed. Look for the collapse of the soft tissues at the level of the base of the tongue and just above the soft palate. Level of pharyngeal obstruction can be found. (Ref: Diseases of ENT, PL Dhingra, 7th edition, pg no. 315)