Changes in the breath sound spectrum during methacholine inhalation in children with asthma

Abstract

Background and objective: An effort-independent breath sound analysis is expected to be a safe and simple method for clinical assessment of changes in airway function. The effects of bronchoconstriction and bronchodilation on novel breath sound parameters in asthmatic children were investigated. Methods: The study population included 49 children with atopic asthma (male = 33; mean age: 10.2 years). We evaluated breath sound parameters of the highest frequency of the power spectrum (HFp), frequency limiting 50% and 99% of the power spectrum (F 50 and F 99 ) and roll-off from 600 Hz to the HFp (Slope). We also assessed new parameters obtained using the ratios of sound spectrum parameters (spectrum curve indices), such as the ratio of the third and fourth power area to the total power area (P 3 /P T and P 4 /P T ), the ratio of the third and fourth areas to the total area under the curve (A 3 /A T and B 4 /A T ) and the ratio of power and frequency at 75% of HFp and 50% of HFp (RPF 75 and RPF 50 ). This was measured before and after methacholine inhalation challenge and after β 2 agonist inhalation. Results: The parameters, F 50 and F 99 , showed no changes after methacholine inhalation. Conversely, the A 3 /A T (12.5-10.0%, P < 0.001), B 4 /A T (7.6-5.5%, P < 0.001), RPF 75 (6.7-4.0 dBm/Hz, P < 0.001) and RPF 50 (5.8-4.3 dBm/Hz, P < 0.001) were significantly decreased. These values returned to the original level after β 2 agonist inhalation. Conclusion: Spectrum curve indices indicate bronchoconstriction and bronchodilation. These parameters may play a role in the assessment of airway narrowing in asthmatic children.

Objective evaluation of wheezing in normal infants

“…In this study, there were no marked differences in any breath sound parameters, including F 99 , slope, A 3 /A T , B 4 /A T , RPF 50 and RPF 75 , between the infants with and without FW. A 3 /A T , RPF 50 and RPF 75 are decreased by methacholine inhalation and increased by β 2 agonist inhalation . It has been suggested that the induction of bronchial constriction changes the sound spectrum .…”

“…We recently investigated the potential utility of a breath sound analysis as a non‐invasive, reliable lung function test for children with asthma and infants . On analysis of a sound spectrogram, we identified and digitized the audible wheezing and FW in children .…”

“…The data were automatically calculated using a custom software program . The parameters of the total power of the power spectrum (P T )(log[mV 2 ]), the roll‐off of the middle spectrum curve (slope, −dBm/octave) and the frequency limiting 99% of the power spectrum (F 99 ) were measured in accordance with previous reports . The total area under the curve (A T ), the third area under the curve (A 3 ) and the forth area under the curve (B 4 ) were conventionally calculated using dBm and Hz (1 arbitrary unit [dBm・Hz] on a spectrum image).…”

Contemporary Concise Review 2018: Asthma and chronic obstructive pulmonary disease

“…Tabata et al . used novel breath sound analysis in children with asthma undergoing methacholine challenge . Changes in specific breath sound parameters could be readily detected in the absence of overt wheezing.…”

Acoustic analysis of neonatal breath sounds using digital stethoscope technology

“…Previous studies have demonstrated that airflow affects lung sound intensity in adults, 15 and due to the size difference between the airways of preterm and term infants, airflow may be different. Malmberg et al 16 and Tabata et al 17 were able to document changes in acoustic qualities of breath sounds during bronchoconstriction challenges in asthmatic children, with greater power at high frequencies during bronchoconstriction, suggesting an association between narrower airways and higher frequency power spectrum profiles. This could explain the higher power seen in the preterm group above 700 Hz, who inherently have narrower airways than the term cohort.…”