This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Anaesthesia
A 74-year-old woman with a history of a previous total abdominal hysterectomy presents with abdominal pain and distention for 3 days. She is noted on plain films to have dilated small-bowel and air-fluid levels. She is taken to the operating room for a small-bowel obstruction. Which of the following inhalational anesthetics should be avoided because of accumulation in air-filled cavities during general anesthesia? 
Select and explain. 
A. Diethyl ether, B. Nitrous oxide, C. Halothane, D. Methoxyflurane
B: Nitrous oxide
Answer: B: Nitrous oxide 
Explanation: Nitrous oxide has a low solubility compared with other inhalation anesthetics; nitrous oxide is more soluble in blood than nitrogen and is the only anesthetic gas less dense than air. As a result of these propeies, nitrous oxide may cause progressive distension of air-filled spaces during prolonged anesthesia. Since nitrous oxide diffuses into gas-filled compaments faster than nitrogen can diffuse out, its use can lead to worsened distention, which may be undesirable (eg, in an operation for intestinal obstruction).