This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
In caissons disease pain in joint is because of 
Select and explain. 
A. Nitrogen bubble, B. Oxygen bubble, C. Carbon monoxide, D. Air in joint
A: Nitrogen bubble
Answer: A: Nitrogen bubble 
Explanation: In Caisson’s disease, the gas embolism is caused by nitrogen that expands in the tissues and passes to the circulation.