Nitrous oxide is commonly used in the dental office and utilizes which system as its entry point?

• A. Pulmonary system
• B. Gastrointestinal tract
• C. Intraosseous
• D. Subcutaneous tissue

Answer: (A)

Nitrous oxide is delivered by inhalation, so the entry point is the respiratory, or pulmonary, system. In dental settings this gas is administered through a nasal hood and breathed into the lungs, where it moves from the alveoli into the bloodstream. This route explains both the rapid onset and quick recovery that characterize nitrous oxide, since the gas readily equilibrates between the alveoli and blood and is cleared when inhalation stops.

Other routes listed don’t apply because nitrous oxide isn’t taken up through the gastrointestinal tract, nor is it delivered by injecting into subcutaneous tissue or intraosseous spaces. Its effectiveness hinges on inhalation and gas exchange in the lungs.