The study by K. Alving, E. Weitzberg, and J.M. Lundberg investigates the levels of nitric oxide (NO) in the exhaled air of healthy individuals and those with mild atopic asthma and rhinitis. Using a chemiluminescence technique, they found that in healthy subjects, most of the NO (up to 30 ppb) originates in the nasal airways, with minimal contribution from the lower airways and oral cavity. In contrast, in mild asthmatics, the level of exhaled NO during oral breathing, indicating involvement of the lower airways, was 2-3 times higher. The study suggests that exhaled NO levels can be used to monitor ongoing bronchial inflammation, particularly when involving inducible NO synthase. The results also indicate that the nasal mucosa is the primary source of NO in normal airways, while the lower airways may be more involved in asthma and rhinitis, potentially due to increased production by activated macrophages or neutrophils.The study by K. Alving, E. Weitzberg, and J.M. Lundberg investigates the levels of nitric oxide (NO) in the exhaled air of healthy individuals and those with mild atopic asthma and rhinitis. Using a chemiluminescence technique, they found that in healthy subjects, most of the NO (up to 30 ppb) originates in the nasal airways, with minimal contribution from the lower airways and oral cavity. In contrast, in mild asthmatics, the level of exhaled NO during oral breathing, indicating involvement of the lower airways, was 2-3 times higher. The study suggests that exhaled NO levels can be used to monitor ongoing bronchial inflammation, particularly when involving inducible NO synthase. The results also indicate that the nasal mucosa is the primary source of NO in normal airways, while the lower airways may be more involved in asthma and rhinitis, potentially due to increased production by activated macrophages or neutrophils.