Role of endogenous nitric oxide in airflow obstruction in smokers

Objective: The aim of this study was to examine the relationship between endogenous nitric oxide (NO) level and airflow obstruction in smokers using single-breath measurement of exhaled NO with the sequential breath-holding method. Setting: A university hospital. Patients: Nine nonsmoking and ten smoking healthy volunteers. Measurements: NO in exhaled air was measured using a chemiluminescence analyzer. Pulmonary function tests were performed using an autospirometer. Results: The level of exhaled NO was higher in nonsmokers than in smokers, and the difference became larger as the breath-holding time increased. To evaluate the correlation between endogenous NO level and the degree of airflow obstruction in smokers, we used a new parameter, the NO concentration difference (Delta NO). Our findings indicate that reduced level of NO in exhaled air is an indicator of decreased NO synthesis within the respiratory system and is associated with the development of airflow obstruction in smokers (r=0.678; p<0.01). Conclusions: Delta NO is a good indicator of the synthesis of endogenous NO within the respiratory system, and it appears likely that the reduced synthesis of NO may be a contributing factor to airflow obstruction in smokers.