Abstract:

Objective To study the correlation between alveolar nitric oxide（CaNO）and small airway function in asthmatic patients with acute exacerbation and the influencing factors of alveolar nitric oxide. Methods We retrospectively selected a total of 116 acute onset asthmatic patients who were admitted into Department of Respiratory and Critical Care Medicine of our hospital from September 2019 to August 2021. The exhaled nitric oxide （NO）concentration was determined，and the concentration of NO in the alveolar（CaNO）and central airway（FeNO） was recorded. Lung function and peripheral blood eosinophils count（EOS）were tested and recorded as the observation indexes. The correlation between CaNO with small airway function in asthmatic patients and the influencing factors of CaNO were analyzed. Results CaNO was negatively correlated with MMEF%pred，FEF75%pred and FEF50%pred in acute onset asthmatic patients（r = -0.281，-0.236，-0.272，P < 0.05），but not correlated with FeNO and EOS； FeNO was positively correlated with EOS，MMEF%pred，FEF75%pred，FEF50%pred（r = 0.283，0.194，0.211，0.186， P < 0.05）. FeNO and FEF75%pred of smoking⁃asthmatic patients were lower than non⁃smokers（P < 0.05），and there was no statistical difference in CaNO between the two groups（P > 0.05）；There were negatively correlations between CaNO with MMEF%pred and FEF50%pred in non⁃smoking group（P < 0.05），but CaNO was not correlated with the parameters of small airway function in smoking group（P > 0.05）. Allergic rhinitis was the independent influencing factor of the level of CaNO in asthmatic patients. The levels of FeNO and CaNO in asthmatic patients with allergic rhinitis were higher than those without allergic rhinitis（P < 0.05）. There were negatively correlations between CaNO with the parameters of small airway function both in non⁃allergic rhinitis group and allergic rhinitis group（P < 0.05）. Conclusions The concentration of NO in different parts of the airway is different in asthmatic patients. To some extent，CaNO can evaluate small airway obstruction in asthmatic patients，and it is more valuable among non⁃smokers. Allergic rhinitis is the influencing factor of CaNO and exacerbates small airway inflammation in asthmatic patients. 

Key words:

asthma, acute exacerbation, alveolar nitric oxide, fractional exhaled nitric oxide, small airway function, influencing factors