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Frequency distribution of breath sounds as an indicator of bronchoconstriction during histamine challenge test in
L P Malmberg1, R Sorva, A R Sovijärvi
1Department of Pulmonary Medicine, Helsinki University Central Hospital, Finland.
Insights
Spectral analysis of children's breath sounds can indicate airway obstruction during asthma challenges. Changes in expiratory breath sound frequency correlate with forced expiratory volume in 1 second (FEV1) changes.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Biomedical Engineering
Background:
- Asthma in children presents challenges for objective airway obstruction assessment.
- Histamine challenge tests are used to evaluate airway hyperresponsiveness.
- Respiratory sound analysis offers a non-invasive method to study lung function.
Purpose of the Study:
- To investigate changes in respiratory sound frequency spectra during bronchoconstriction and bronchodilatation in children with asthma.
- To compare spectral analysis of breath sounds with forced expiratory volume in 1 second (FEV1) measurements.
- To determine if breath sound analysis can serve as an indicator of airway obstruction in pediatric asthma.
Main Methods:
- Breath sounds were recorded from the chest and trachea of 11 children (10-14 years) with asthma.
- Recordings were taken during a histamine challenge test and after bronchodilatation.
- Changes in breath sound frequency spectra were compared with simultaneous FEV1 measurements.
Main Results:
- A significant relationship was found between percentage change in FEV1 and percentage change in median frequency (F50) of expiratory breath sounds (r=0.865-0.888, P<0.0001).
- An increase in F50 was significantly larger in children responsive to histamine.
- A 15% decrease in FEV1 corresponded to an 8% increase in expiratory F50, with related provocative doses (PD15FEV1 and PD8F50).
Conclusions:
- Spectral analysis of breath sounds is a viable method to indicate airway obstruction during bronchial challenge tests in children.
- This technique may be adaptable for use in pre-school children.
- Airflow limitation induced by histamine in asthmatic children is associated with increased frequency content in their breath sounds.
Abstract:
In order to study changes in respiratory sounds associated with acute bronchoconstriction and -dilatation, breath sounds of 11 children with asthma (age range, 10-14 years) were recorded at the chest and at the trachea during histamine challenge test and after subsequent bronchodilatation. The changes in frequency spectra of breath sounds were compared with simultaneous changes in forced expiratory volume in 1 second (FEV1). In seven children who responded to histamine with a decrease in FEV1 of more than 15%, there was a significant relationship between percentage change in FEV1 (delta FEV1) and percentage change in median frequency (delta F50) of expiratory breath sounds recorded at the chest (r = 0.865; beta = -0.706, P = 0.0001) and at the trachea (r = 0.888; beta = -1.12, P = 0.0001). The association between breath sound intensity and FEV1 was weaker. Based on ANOVA, the increase of F50 during the challenge test was significantly larger in children who responded to histamine than in those who were non-responsive (P = 0.0016). At the chest, a decrease of 15% in FEV1 corresponded to an increase of 8% in expiratory F50. The provocative dose of histamine inducing a decrease of 15% in FEV1 (PD15FEV1) and the provocative dose causing an increase of 8% in F50 (PD8F50) were significantly related (r = 0.927, P = 0.003). We conclude that spectral analysis of breath sounds can be used to indicate airway obstruction during bronchial challenge tests in children, and may be adapted for tests in pre-school children. The results suggest that the same mechanisms that induce airflow limitation due to inhaled histamine may generate an increase in frequency content of breath sounds in children with asthma.