Peripheral bronchial obstruction evaluation in patients with asthma by lung sound analysis and impulse oscillometry

BackgroundComputer-aided lung sound analysis (LSA) has been reported to be useful for evaluating airway inflammation and obstruction in asthma patients. We investigated the relation between LSA and impulse oscillometry with the evaluation of peripheral airway obstruction.MethodsA total of 49 inhaled corticosteroid-naive bronchial asthma patients underwent LSA, spirometry, impulse oscillometry, and airway hyperresponsiveness testing. The data were analyzed to assess correlations between the expiration: inspiration lung sound power ratio (dB) at low frequencies between 100 and 195 Hz (E/I LF) and various parameters.ResultsE/I LF and X5 were identified as independent factors that affect V˙50,%predicted. E/I LF showed a positive correlation with R5 (r = 0.34, p = 0.017), R20 (r = 0.34, p = 0.018), reactance area (AX, r = 0.40, p = 0.005), and resonant frequency of reactance (Fres, r = 0.32, p = 0.024). A negative correlation was found between E/I LF and X5 (r = −0.47, p = 0.0006). E/I LF showed a negative correlation with FEV1/FVC(%), FEV1,%predicted, V˙50,%predicted, and V˙25,%predicted (r = −0.41, p = 0.003; r = −0.44, p = 0.002; r = −0.49, p = 0.0004; and r = −0.30, p = 0.024, respectively). E/I LF was negatively correlated with log PC20 (r = −0.30, p = 0.024). Log PC20, X5, and past smoking were identified as independent factors that affected E/I LF level.ConclusionsE/I LF as with X5 can be an indicator of central and peripheral airway obstruction in bronchial asthma patients.