Lung sound analysis helps localize airway inflammation in patients with bronchial asthma

Abstract

PurposeAirway inflammation can be detected by lung sound analysis (LSA) at a single point in the posterior lower lung field. We performed LSA at 7 points to examine whether the technique could identify the location of airway inflammation in patients with asthma.Patients and methodsBreath sounds were recorded at 7 points on the body surface of 22 asthmatic subjects. Inspiration sound pressure level (ISPL), expiration sound pressure level (ESPL), and the expiration-to-inspiration sound pressure ratio (E/I) were calculated in 6 frequency bands. The data were analyzed for potential correlation with spirometry, airway hyperresponsiveness (PC20), and fractional exhaled nitric oxide (FeNO).ResultsThe E/I data in the frequency range of 100–400 Hz (E/I low frequency [LF], E/I mid frequency [MF]) were better correlated with the spirometry, PC20, and FeNO values than were the ISPL or ESPL data. The left anterior chest and left posterior lower recording positions were associated with the best correlations (forced expiratory volume in 1 second/forced vital capacity: r=−0.55 and r=−0.58; logPC20: r=−0.46 and r=−0.45; and FeNO: r=0.42 and r=0.46, respectively). The majority of asthmatic subjects with FeNO ≥70 ppb exhibited high E/I MF levels in all lung fields (excluding the trachea) and V50%pred <80%, suggesting inflammation throughout the airway. Asthmatic subjects with FeNO <70 ppb showed high or low E/I MF levels depending on the recording position, indicating uneven airway inflammation.ConclusionE/I LF and E/I MF are more useful LSA parameters for evaluating airway inflammation in bronchial asthma; 7-point lung sound recordings could be used to identify sites of local airway inflammation.

<p>Lung Sound Analysis Provides A Useful Index For Both Airway Narrowing And Airway Inflammation In Patients With Bronchial Asthma</p>

“…Therefore, the E/I MF is useful not only as an index of airway narrowing but also as an index of mild eosinophilic airway inflammation. In addition, we have previously reported that the E/I MF is useful as an index of neutrophilic inflammation and mixed-type inflammation involving both eosinophils and neutrophils8 and it is useful as an index for the localization of airway narrowing and airway inflammation by examining lung sounds at seven sites in the thoracic wall 7…”

“…We have previously reported that the expiration-to-inspiration sound power ratio in a midfrequency range (E/I MF), a parameter of lung sound analysis (LSA), is a useful index of airway narrowing and airway inflammation in asthma without treatment 5–8. We have also reported that the E/I MF increases not only in cases of eosinophilic inflammation in bronchial asthma but also in cases of neutrophilic inflammation and mixed-type inflammation with them 7,8. However, the E/I MF correlates with the forced expiratory volume in one second (FEV 1 ), which is an index of airway narrowing, as well as with the sputum eosinophil count and fractional exhaled nitric oxide (FeNO), which are known as indices of airway eosinophilic inflammation.…”

Lung and Heart Sounds Analysis: State-of-the-Art and Future Trends

“…According to the literature on lung sound analysis, the most common respiratory diseases that are studied include COPD , 53,54,65,75,79,83,86,87,94,101,105,144 asthma, 53,54,65,71,72,85,87,105,107,110,117 and pulmonary emphysema. 58,70,93,99,106,112 However, lung sounds recorded during pneumonia, 54,65,76,79,103 pulmonary fibrosis, 56,70,76 chronic bronchitis, 56 idiopathic pulmonary fibrosis, 63 congestive heart failure, 76,79 parenchymal pathology, 75,90 and interstitial lung disease 79,87,104 appear less frequently in the literature.…”

Lung sounds in bronchial asthma

“…[6][7][8] Recent studies show that lung sounds are useful tools to assess the airway inflammation in asthma even in asymptomatic and not wheezing asthma patients. 3,4,[9][10][11] Nomenclature of lung sounds An international agreement on lung sounds was reached at an International Symposium on Lung Sounds held in 1986 12 (Table 1). Lung sounds were divided into breath sounds and adventitious sounds.…”