What medical gas is commonly used to treat pulmonary hypertension?

Nitric oxide is the medical gas commonly used to treat pulmonary hypertension due to its unique properties as a selective pulmonary vasodilator. When inhaled, nitric oxide diffuses quickly into the smooth muscle cells of the pulmonary vasculature, leading to relaxation and dilation of blood vessels. This effect decreases pulmonary artery pressure and improves blood flow, which is particularly beneficial for patients with conditions like pulmonary hypertension, where there is increased resistance in the pulmonary circulation.

The other gases listed do not have the same targeted therapeutic effects in treating pulmonary hypertension. Carbon dioxide is primarily used in medical settings to create a respiratory acidosis for diagnostic purposes or during certain surgeries, but it does not provide the vasodilatory properties needed to address pulmonary hypertension. Helium is often combined with oxygen to reduce airway resistance in obstructive lung diseases but does not directly influence blood vessel dilation. While oxygen is crucial for treating hypoxemia, it does not target the pulmonary vasculature specifically to alleviate the high blood pressure associated with pulmonary hypertension.