Averaged and Time-Gated Spectral Analysis of Respiratory Sounds: Repeatability of Spectral Parameters in Healthy Men and in Patients With Fibrosing Alveolitis

doi:10.1378/chest.109.5.1283

Chest

Volume 109, Issue 5, May 1996, Pages 1283-1290

https://doi.org/10.1378/chest.109.5.1283 Get rights and content

Study objective

To obtain a basis for assessment of changes in breath sound spectra in patients with pulmonary diseases, short-term and day-to-day repeatability of spectral parameters was studied.

Design

Breath sounds were recorded simultaneously from the trachea and from the chest twice at an interval of 15 min (short-term repeatability) and of 1 to 3 days (day-to-day repeatability). During recordings, air flow at the mouth was controlled, the target inspiratory and expiratory peak flow being 1.25 L/s. Inspiratory and expiratory breath sound spectra were averaged over 7 to 10 successive respiratory cycles. The repeatability of sound intensity (RMS), frequency of maximum intensity (Fmax), and median frequency (F50) was analyzed with analysis of variance.

Participants

Short-term repeatability was studied in 10 healthy nonsmoking men (age 25 to 44 years), and day-to-day repeatability was studied in 10 healthy nonsmoking men (age 23 to 41 years) and in 12 patients with clinically stable fibrosing alveolitis (age 35 to 82 years).

Results

Short-term coefficient of variation (CoV) of Fmax and F50 was 2.6 to 6.7% when recorded from the chest, and 6.2 to 8.7% when recorded from the trachea. Day-to-day CoV of Fmax and F50 in healthy subjects was 4.7 to 8.5% and 5.0 to 8.7% recorded from the chest or from the trachea, respectively. Inspiratory day-to-day variation in those parameters was higher in patients with fibrosing alveolitis. CoV of RMS was high, ranging from 18 to 47% in different subject groups and sampling situations.

Conclusions

Repeatability of F50 of averaged flow-controlled lung sound spectra is good both in healthy subjects and in patients with fibrosing alveolitis. Thus, F50 of respiratory sound spectra may be useful in monitoring of changes induced by respiratory diseases and interventions. These results emphasize the importance of standardization of recording conditions and of analyzing techniques.

Section snippets

MATERIALS AND METHODS

The short-term repeatability of the frequency spectral variables of breath sounds was studied in ten healthy nonsmoking men. Their anthropometric and lung function data are presented in Table 1. Two recordings of breath sounds were made for each subject at an interval of 15 min. The day-to-day repeatability of the breath sound variables was studied in an other group of 10 healthy nonsmoking men and in 12 patients with stable fibrosing alveolitis (Table 1). Recordings were performed twice at an

RESULTS

The overall mean values and intraindividual variation of peak tidal air flow values and the duration of respiratory cycles during breath sound recordings are shown in Table 2. The CoV of PTIF and PTEF in healthy subjects was around 4% and that in patients with fibrosing alveolitis, 8 to 12%. The mean PTIF and PTEF during recordings varied between 1.37 L/s and 1.47 L/s. Compared with healthy individuals, the patients with fibrosing alveolitis had slightly lower PTIF values during the recordings

DISCUSSION

Knowledge of the repeatability of breath sound parameters is essential if such measurements are used on two or more occasions to monitor the effects of a respiratory disease, its treatment, or interventions such as bronchodilator or challenge tests. A test variable with a good discrimination property shows small within-subject variation both during the short term and long term. Variability in respiratory sound parameters obtained by computerized analyses derives from many sources. The

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The spectrum curve indices, A₃/A_T, B₄/A_T, RPF₇₅, and RPF₅₀, showed statistically significant increase following β₂-agonist inhalation. The increase in RPF₅₀ was correlated with the decrease in the difference between resistance at 5 Hz and 20 Hz, R5-R20, measured by FOT. In the multiple regression analysis adjusted for the effect of ΔRPF₇₅, the changes in A₃/A_T and B₄/A_T were positively correlated with that in the forced expiratory volume in one second.
The spectrum curve indices indicated bronchodilation, and may be useful for the assessment of bronchial reversibility in children with asthma.
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The common parameters were significantly increased after methacholine inhalation, whereas the spectrum curve indexes significantly decreased after methacholine inhalation (Fig. A1a–e in Appendix). Changes in respiratory sounds during bronchial challenges have been evaluated [5,21], and the potential of using breath sound analyses for noninvasive pulmonary function testing has been demonstrated [22,23]. We have been interested in the breath sounds of childhood asthma patients without typical asthma attacks.
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Regional Breath Sound Distribution Analysis in Single-lung Transplant Recipients
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Perfusion scintigraphy has been used to evaluate and monitor graft function in single-lung transplant recipients. In this study, our objective was to determine whether quantitatively measured regional breath sounds, using a computerized breath sound analysis device, correlate with the standard methods of monitoring graft function used at our facility for single-lung transplant patients.
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Tracheal and lung sounds measurements for clinical applications depends on their intrasubject repeatability. Our objectives were to characterize tracheal and lung sounds and to investigate the temporal variability in normal adults. Tracheal sounds were studied in 7 subjects and lung sounds in 10 adults. Acoustic measurements were done in five occasions over a month for tracheal sounds and on seven occasions over a year for lung sounds. Sounds were recorded using contact sensors on the suprasternal notch and on the posterior right lower lobe. Subjects breathed through a pneumotachograph at flows of 0.9–1.1 l/s. Signals were low-pass filtered, amplified and Fourier analysis was applied to sounds within a target flow range. We measured the frequencies below which 25% (F25), 50% (F median), 75% (F75) and 99% (SEF99) of the spectral power between 100 and 2000 Hz. There were no differences between the measurements obtained at different days comparing each subject (P=ns, ANOVA). Our results show that the spectral pattern of tracheal and lung sounds are stable with low intrasubject variability.

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Chest

Averaged and Time-Gated Spectral Analysis of Respiratory Sounds: Repeatability of Spectral Parameters in Healthy Men and in Patients With Fibrosing Alveolitis

Study objective

Design

Participants

Results

Conclusions

Section snippets

MATERIALS AND METHODS

RESULTS

DISCUSSION

Chest

Chest

Chest

Chest

Chest

Respir Physiol

Chest

Chest

Chest

Chest

Phonopneumography

Am Rev Respir Dis

Chest auscultation in the diagnosis of pulmonary asbestosis

J Occup Med

Visual lung-sound characterization by time-expanded wave-form analysis

N Engl J Med

Diagnosis of asbestosis by a time expanded wave form analysis, auscultation and high resolution computed tomography: a comparative study

Thorax

Respiratory health screening using pulmonary function tests and lung sound analysis

Eur Respir J

Variation of breath sound and airway caliber induced by histamine challenge

Am Rev Respir Dis

Effect of methacholine induced bronchoconstriction on the spectral characteristics of breath sounds in asthma

Thorax

Changes in frequency spectra of breath sounds during histamine challenge test in adult asthmatics and healthy controls

Chest