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

N2O use is contraindicated in pneumothorax and volvulus because it may lead to the development of high pressure in the closed cavities in the body (like an obstructed loop of bowel, intraocular air bubble, a pulmonary bulla, pneumothorax, ob­structed middle ear, air embolus, intracranial air and pneumoperitoneum).