Dang-Thi-Mai K, Le-Dong NN, Le-Thuong V, et al. - In this cross-sectional and in-hospital population-based study, researchers sought to assess the association between exhaled nitric oxide (eNO) markers and obstructive sleep apnea (OSA) severity and verify the changes in eNO profiles among mild, moderate, and severe OSA subgroups. One hundred twenty-three OSA patients (17 mild, 23 moderate and, 83 severe OSA) were examined in the department of respiratory diseases. Anthropometry, respiratory polygraphy, biological markers, spirometry, and multi-flow eNO measurements were among the data sets examined. In mild, moderate, and severe OSA, the bronchial production rate of NO (J’awNO) rose correspondingly, with median values of 11.2, 33.9, and 36.2, respectively. The current study found that J'AWNO, which represents eNO derived from the central airway, is proportionally higher in more severe OSA patients, whereas the alveolar concentration of NO, which represents eNO derived from the alveolar space, was also associated with OSA severity and was relatively lower in most severe OSA patients. Stand-alone fractional exhaled nitric oxide metrics, on the other hand, did not show a clear difference between the three severity subgroups.