Question:medium
Which of the following gas is used to decrease pulmonary artery pressure in adults?
Which of the following gas is used to decrease pulmonary artery pressure in adults?
Show Hint
Inhaled nitric oxide relaxes pulmonary artery smooth muscle through the cyclic GMP pathway and is inactivated by haemoglobin the moment it enters blood, so its effect stays local to the lung.
Updated On: Jul 8, 2026
- Nitrous Oxide
- Nitrogen Dioxide
- Nitric Oxide
- Nitrogen
Show Solution
The Correct Option is C
Solution and Explanation
Step 1: Separate the four gases by what they actually do in the body.
Nitrous oxide gives sedation and pain relief during anaesthesia. Nitrogen is chemically inert and just fills space in the lungs. Nitrogen dioxide is a harmful gas that injures the airway lining. None of these change blood vessel tone in the lung.
Step 2: Bring in nitric oxide's mechanism. \[ NO \rightarrow \text{guanylate cyclase} \rightarrow \uparrow cGMP \rightarrow \text{smooth muscle relaxation} \]
This pathway is the same one used by drugs like nitroglycerin, but here the gas itself is delivered directly by inhalation.
Step 3: Note the safety feature that makes it useful.
As soon as nitric oxide crosses into the blood, haemoglobin grabs it and turns it into methaemoglobin, so it cannot travel onward to dilate vessels elsewhere in the body. This means only the pulmonary vessels next to ventilated alveoli feel the drop in tone, and systemic blood pressure stays steady.
Step 4: Conclude.
This selective, lung confined vasodilation is exactly why inhaled nitric oxide is used to bring down a raised pulmonary artery pressure in adults.
\[ \boxed{\text{Nitric Oxide}} \]
Nitrous oxide gives sedation and pain relief during anaesthesia. Nitrogen is chemically inert and just fills space in the lungs. Nitrogen dioxide is a harmful gas that injures the airway lining. None of these change blood vessel tone in the lung.
Step 2: Bring in nitric oxide's mechanism. \[ NO \rightarrow \text{guanylate cyclase} \rightarrow \uparrow cGMP \rightarrow \text{smooth muscle relaxation} \]
This pathway is the same one used by drugs like nitroglycerin, but here the gas itself is delivered directly by inhalation.
Step 3: Note the safety feature that makes it useful.
As soon as nitric oxide crosses into the blood, haemoglobin grabs it and turns it into methaemoglobin, so it cannot travel onward to dilate vessels elsewhere in the body. This means only the pulmonary vessels next to ventilated alveoli feel the drop in tone, and systemic blood pressure stays steady.
Step 4: Conclude.
This selective, lung confined vasodilation is exactly why inhaled nitric oxide is used to bring down a raised pulmonary artery pressure in adults.
\[ \boxed{\text{Nitric Oxide}} \]
Was this answer helpful?
0
