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Reevaluation of the relationship between within-day bronchial variability and bronchial responsiveness in asthmatic
Insights
Bronchial variability in children with asthma correlates with bronchial responsiveness to allergens and irritants. This finding supports using bronchial variability as a clinical indicator for asthma management.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Allergy and Immunology
Background:
- Previous research indicated a link between diurnal bronchial variability and bronchial responsiveness (BR) in asthma.
- Severe bronchial obstruction often occurs overnight, potentially causing diurnal variability to underestimate true within-day changes.
Purpose of the Study:
- To re-evaluate the correlation between bronchial variability and BR.
- To more accurately assess within-day bronchial caliber variability in children with episodic asthma.
Main Methods:
- Forty-three children (8-12 years) with episodic asthma underwent FEV1 measurements every 4 hours for 48 hours.
- Bronchial variability was quantified using the coefficient of variation (CV) of forced expiratory volume in 1 second (FEV1).
- Bronchial responsiveness was measured using house-dust allergen, histamine, and a 7-minute free running exercise challenge.
Main Results:
- Significant correlations were found between bronchial variability (CV) and BR to house-dust (r = -0.663, p < 0.01) and histamine (r = -0.661, p = 0.01).
- A marginally significant correlation was observed between bronchial variability and BR to running (r = -0.496, 0.05 < p < 0.1).
Conclusions:
- The study confirms that bronchial variability is a reliable indicator of bronchial responsiveness to various stimuli in asthmatic children.
- Bronchial variability measurements can serve as a valuable clinical index in managing asthma.
Abstract:
Earlier studies demonstrated a correlation between diurnal bronchial variability and bronchial responsiveness (BR) in asthmatic patients. However, since the most severe bronchial obstruction tends to occur from midnight to early morning, diurnal bronchial variability might underestimate within-day bronchial variability. This study was undertaken to reevaluate the correlation after assessing more precisely the within-day variability of bronchial caliber in 43 children with episodic asthma (23 boys, 20 girls), aged 8-12 years. Seven FEV1 measurements were made every 4 h between 10:00 and 10:00 for 2 consecutive days. The coefficient of variation (CV) of the last six FEV1 was defined as the amplitude. Just after measurement of FEV1 at 10:00 on day 2, measurements of BR to house-dust allergen, histamine, and 7-min free running were made in 14, 14, and 15 patients, respectively. The BR was expressed as the percent change in FEV1 from the baseline value in house-dust inhalation and running challenges, and as the provocative concentration causing a 20% fall in FEV1 (PC20), transformed into a logarithmic scale, in histamine challenge. There were significant correlations between CV [mean (SD), 8.1 (5.3)%] and BR to house-dust [mean (SD), -19.0 (11.8)%] (r = -0.663, p < 0.01), and between CV [mean (SD), 7.4 (5.5)%] and histamine PC20 (geometric mean, 0.38 mg/ml) (r = -0.661, p = 0.01). There was a marginally significant correlation between CV [mean (SD), 6.4 (3.7)%] and BR to running [mean (SD), 28.5 (16.6)%] (r = -0.496, 0.05 < p < 0.1). These results confirmed the reliability of earlier studies that suggested that the bronchial variability may be one of clinical indices of BR to various stimuli in asthmatic patients.