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Aerosol bolus dispersion and effective airway diameters in mildly asthmatic children
1GSF - Forschungszentrum für Umwelt und Gesundheit, Institut für Inhalations, Biologie, Oberschleissheim, Germany.
Insights
Aerosol bolus dispersion shows differences in paediatric asthma patients compared to healthy children. While not improving diagnosis, it offers insights into altered gas transport in diseased lungs.
Area of Science:
- Pulmonary Medicine
- Aerosol Science
- Paediatric Respiratory Research
Background:
- Mild paediatric asthma diagnosis relies on lung function tests.
- Aerosol techniques offer novel ways to assess airway function.
Purpose of the Study:
- To investigate aerosol bolus dispersion and airway dimensions for diagnosing paediatric asthma.
- To compare aerosol technique sensitivity with conventional lung function tests.
Main Methods:
- Studied 47 children with mild asthma and 16 healthy children.
- Measured effective airway diameters using inhaled sebacate droplets.
- Analyzed intrapulmonary dispersion of inhaled particle boluses via exhaled air concentration distributions (standard deviation and skewness).
Main Results:
- Effective airway diameters did not differ between asthmatic and healthy children.
- Asthmatic children showed higher standard deviation and skewness in exhaled particle boluses.
- Bolus dispersion sensitivity was comparable to FEV1/FVC for detecting lung function alterations.
Conclusions:
- Aerosol measurements offer no clear diagnostic advantage for mild paediatric asthma.
- Bolus dispersion provides additional information on convective gas transport changes in diseased lungs.
Abstract:
The contribution of aerosol techniques, the estimation of aerosol bolus dispersion and effective airway dimensions, to the clinical diagnosis of paediatric asthma was studied. In 47 children, aged 11 +/- 2 yrs, with mild asthma (forced expiratory volume in one second (FEV1) 83 +/- 9% of forced vital capacity (FVC)) effective airway diameters were derived from the recovery of inhaled 1 micron sebacate droplets. Intrapulmonary dispersion of inhaled boluses of 0.4 micron droplets was studied, by characterizing the concentration distributions of droplets in the exhaled air by their standard deviation and skewness. Effective airway diameters increased in asthmatic subjects with increasing body size, and did not differ from those obtained in 16 healthy children of similar age and height. Standard deviation and skewness of particle boluses exhaled from shallow lung depths were higher in the asthmatic children than the healthy children (e.g. standard deviation 91 +/- 17 ml vs 79 +/- 15 ml, skewness 0.38 +/- 0.16 vs 0.23 +/- 0.16, respectively, for boluses in 140 ml lung depth). The sensitivity and specificity of bolus dispersion to detect alterations in lung function was comparable to that of FEV1/FVC, the most sensitive conventional lung function parameter in the present study. There was no correlation between body height or lung function and bolus parameters. We conclude that aerosol measurements do not provide an obvious benefit for the clinical diagnosis of mild paediatric asthma, but bolus dispersion supplies additional information on alterations in convective gas transport in the diseased lung.