Chest
Clinical Investigations: TumorsChanges in Frequency Spectra of Breath Sounds During Histamine Challenge Test in Adult Asthmatics and Healthy Control Subjects
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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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This study was supported by the Ida Montin Foundation, Finland.