Chest
Volume 105, Issue 1, January 1994, Pages 122-131
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Clinical Investigations: Tumors
Changes in Frequency Spectra of Breath Sounds During Histamine Challenge Test in Adult Asthmatics and Healthy Control Subjects

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Air-flow standardized breath sounds were recorded at the chest and at the trachea during histamine challenge test and after subsequent bronchodilation in 12 asthmatics and 6 healthy controls for spectral analysis, to be compared with simultaneous changes in spirometric variables. Of all the lung sound variables measured, the changes in median frequency of the power spectrum (F50) of tracheal expiratory sounds were found to correlate best (r = −0.853, p < 0.0001) with changes in FEV1. The increase of F50 during histamine challenge was significantly larger in asthmatics than in healthy control subjects (p < 0.005). The provocative dose of histamine inducing a decrease of 15 percent in FEV1 (PD15FEV1) and the provocative dose causing an increase of 30 percent in tracheal expiratory F50 (PD30F50) were significantly related (r = 0.754, p = 0.012). In asthmatics, the breath sound frequency distribution in terms of median frequency reflected acute changes in airways obstruction with high sensitivity and specificity. The present method for breath sound analysis can be applied for patients with limited cooperation during bronchial challenge tests.

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Patients and Subjects

Twelve asthmatics with increased bronchial hyperresponsiveness and 6 healthy volunteers were selected for the study. Their anthropometric and lung function data are presented in Table 1. The asthmatics were diagnosed according to the American Thoracic Society (ATS) criteria;11 they had had intermittent dyspnea, cough, or wheezing and showed an increase in FEV1 of 15 percent or more in a spirometric bronchodilation test or a diurnal variation in peak expiratory flow of at least 20 percent. At

Results

The results of the breath sound analysis and FEV1 at the basal stage, after histamine challenge, and after bronchodilation treatment in healthy subjects and asthmatics are shown in Table 2. None of the healthy subjects responded significantly (decrease of FEV1 at least 15 percent) to any dose of histamine. The median decrease in FEV1 after the maximum dose of histamine (1.6 mg) was −6.5 percent (range, from −1 to −9 percent); the decrease in FEV1 was statistically significant (p < 0.01). The

Discussion

Significant changes in averaged breath sound frequency spectra were demonstrated in this study following histamine-induced bronchoconstriction and subsequent bronchodilatation. The median frequency of spectrum energy (F50) was shifted toward higher frequencies during bronchoconstriction, and returned to lower frequencies after bronchodilatation. The observed changes were parallel whether recorded at the trachea or at the chest. The spectral changes observed both in inspiration and in expiration

ACKNOWLEDGMENTS

The authors are grateful to Mr. Kari Kallio, B.Sc.(Eng.) and Ms. Sari Paukku, M.Sc.(Eng.), for their collaboration, and to Professor Lauri Laitinen, M.D., for reading the manuscript. The help of professor Seppo Sarna for guidance in statistical problems is appreciated.

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  • Cited by (0)

    This study was supported by the Ida Montin Foundation, Finland.

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