NO is a ubiquitous intracellular and intercellular messenger and has many physiological roles in the body, such as assessing airway inflammation in asthma, predicting response to corticosteroids, or supporting respiration in pediatric patients with aspiration pneumonia and premature birth.

Aspiration pneumonia is a lung infection that occurs when a foreign body from the mouth or stomach enters the lungs. Common symptoms of aspiration pneumonia are fever and cough that occur relatively acutely.

Hypersensitivity pneumonitis is common in people who work on farms or livestock farms or who use air conditioners that are not regularly cleaned. Because of similar symptoms, hypersensitivity pneumonitis can be easily confused with other respiratory infections.

Perioperative aspiration is the phenomenon of gastric reflux into the airway before, during and after surgery. If perioperative aspiration is food particles, foreign objects, especially gastric acid, it can cause burns, thickening and obstructing the conduction and exchange of oxygen in the respiratory tract. Therefore, measures must be taken to prevent perioperative aspiration.