This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
Type 4 respiratory failure is due to? 
Select and explain. 
A. ARDS, B. Shock, C. Pneumonia, D. Perioperative atelectasis
B: Shock
Answer: B: Shock 
Explanation: Type 4 respiratory failure results from hypoperfusion of respiratory muscles in patients in shock.Normally,respiratory muscles consume<5% of the total cardiac output and O2 delivery.Patients in shock often experience respiratory distress due to pulmonary edema(eg.,patients in cardiogenic shock),lactic acidosis,and anemia. Ref:Harrison's medicine -18th edition,page no:2200.