INTRODUCTION Chronic obstructive pulmonary disease （COPD） is one of the leading causes of death in the developed world and associated with a high individual and socioeconomic burden. It is characterized by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response in the airways and the lung to noxious panicles or gases. Peri-bronchiolar fibrosis was occurred in small airways in the early state of COPD, and then followed by structure changes, and finally became persistent airflow limitation？21 Recent researches have shown that epithelial-mesenchymal transition （EMT） is one of the leading causes of fibrosis in various diseases.
Background Exhaled nitric oxide （NO） is a noninvasive biomarker of airway inflammation in pulmonary diseases. Hydrogen sulfide （H2S）, as the third member of the gasotransmitter family, is involved in the pathophysiological process in lung diseases. H2S also exists in exhaled breath and can be sampled non-invasively. The study investigated the level of exhaled H2S in patients with chronic obstructive pulmonary disease （COPD） and its correlation with exhaled NO. Methods Levels of exhaled NO and H2S, lung function, and cell differential counts in induced sputum were studied in 19 patients with acute exacerbation of COPD （AECOPD）, 19 patients with stable COPD and seven healthy smoke controls. Results Exhaled H2S levels were similar in patients with AECOPD （10.0 parts per billion （ppb）, 8.0-13.0 ppb）, stable COPD （10.0 ppb, 9.0-12.0 ppb）, and healthy controls （9.0 ppb, 8.0-16.0 ppb） （P 〉0,05）. Exhaled NO levels were similar in patients with AECOPD （155.0 ppb, 129.0-190.0 ppb）, stable COPD （154.0 ppb, 133.0-175.0 ppb） and healthy controls （165.0 ppb, 112.0-188.0 ppb） （P 〉0.05）. Exhaled H2S levels correlated positively with exhaled NO in all healthy controls and patients with COPD （r=0.467, P 〈0.01）. No significant correlation was found between the exhaled H2S level and percentage of predicted FEV1 （P 〉0.05） and proportion of different cell types in induced sputum （P 〉0.05）. Conclusions There is a correlation between exhaled H2S and exhaled NO. The role of exhaled H2S in airway inflammation in COPD still needs further investigation.
SUN YunWANG Xin-maoCHEN Ya-hongZHU Rui-xiaLIAO Cheng-cheng
