Why cant nitrous oxide be given to a pneumothorax patient?

Answer 1

because nitrous oxide is very soluble and although not normally present in the pleural space it will rapidly be transported into the space if th epatient is given nitrous oxide to breathe.

Answer 2

Nitrous oxide can expand in the pneumothorax space and worsen the condition by increasing the size of the collapsed lung. It's important to avoid any gas that can further distend the pneumothorax during treatment.