Nitrous oxide is contraindicated in patients with pneumothorax, pneumopericardium or intestinal obstruction, because it:

Ans. (D) Causes the expansion of air filled body cavities(Ref: Goodman and Gilman 12/e p547)N2 O use is contraindicated in pneumothorax and volvulus because it may lead to development of high pressure in the closed cavities in the body (like obstructed loop of bowel, intraocular air bubble, a pulmonary bulla, pneumothorax, obstructed middle ear, air embolus, intracranial air and pneumoperitoneum).