BACKGROUNDExhaled 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.

METHODSLevels 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.

RESULTSExhaled 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).

CONCLUSIONSThere is a correlation between exhaled H2S and exhaled NO. The role of exhaled H2S in airway inflammation in COPD still needs further investigation.