Methods for reducing, partially preventing or completely preventing nitric oxide (NO) inhalation-related impairment of HPV in a mammal are disclosed. The methods include administering a therapeutically effective amount of NO by inhalation, and co-administering an effective amount of an anti-reactive oxygen species (anti-ROS) agent, e.g., N-acetyl-cysteine, or a leukotriene blocker. Methods for reducing, partially preventing or completely preventing loss of pulmonary vasodilatory responsiveness to NO inhalation in a mammal are also disclosed. The methods include administering a therapeutically effective amount of NO by inhalation, and co-administering an effective amount of an anti-ROS agent a therapeutically effective amount of a leukotriene blocker.