Abbreviations: LSA, Lung sound analysis; FeNO, fractional exhaled nitric oxide; FEV 1.0 , forced expiratory volume in one second; FVC, forced vital capacity; V 50 and V 25 , maximal expiratory flow at 50% and 25%; E/I LF, the expiration-to-inspiration sound power ratio in a low-frequency range; E/I MF, the expiration-to-inspiration sound power ratio in a mid-frequency range; PC 20 , provocative concentration of acetylcholine causing a 20% decrease in FEV1.0 a b s t r a c t Background: We

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... sly reported the results of lung sound analysis in patients with bronchial asthma and demonstrated that the exhalation-to-inhalation sound pressure ratio in the low frequency range between 100 and 200 Hz (E/I LF) was correlated with the presence of airway inflammation and airway obstruction. We classified asthma patients by airway inflammation phenotype using the induced sputum eosinophil and neutrophil ratio and determined whether this phenotype could be predicted using E/I LF and fractional exhaled nitric oxide values. Methods: Steroid-naive bronchial asthma patients were classified into four phenotypes, including "Low inflammation" (35 patients), "Eosinophilic type" (58 patients), "Neutrophilic type" (15 patients), and "Mixed type" (15 patients) based on the results of induced sputum examinations. The E/I LF data and FeNO levels were then evaluated for the four phenotype groups; the prediction powers of these two indices were then analyzed for each phenotype.