Aerosol bolus dispersion in healthy and asthmatic children-theoretical and experimental results
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Published on: April 6, 2017
1Brunnleitenweg 41, A-5061 Elsbethen, Salzburg, Austria.
Insights
Aerosol bolus dispersion increases exponentially with lung depth in children. Asthmatic children show greater dispersion than healthy children, suggesting limited diagnostic potential for aerosol bolus inhalation.
Area of Science:
- Pulmonary medicine
- Respiratory physiology
- Medical physics
Background:
- Aerosol bolus inhalation is a non-invasive technique for diagnosing lung diseases.
- Theoretical models of aerosol bolus behavior are crucial for understanding lung function.
- This study focuses on aerosol bolus dispersion in healthy and asthmatic children.
Purpose of the Study:
- To theoretically investigate aerosol bolus dispersion in healthy and asthmatic children.
- To validate model predictions with experimental findings.
- To assess the diagnostic potential of aerosol bolus inhalation.
Main Methods:
- Simulated aerosol bolus transport using a stochastic respiratory tract model.
- Scaled models for healthy and asthmatic pediatric lungs.
- Utilized effective diffusivities (Deff) for convective mixing prediction.
- Inhaled monodisperse particles (0.4 µm diameter).
- Varied volumetric lung depth (95-540 mL) and bolus half-width (50 mL).
Main Results:
- Aerosol bolus dispersion increases exponentially with volumetric lung depth in both groups.
- Asthmatic children exhibit higher bolus dispersion than healthy children, especially at depths <300 mL.
- Skewness decreases with increasing lung depth, with higher values in asthmatics.
- Model predictions show strong agreement with experimental data.
Conclusions:
- Theoretical models accurately approximate experimental aerosol bolus study results.
- Aerosol bolus inhalation and dispersion measurements have limited diagnostic value for lung diseases.
- Further research may refine the understanding of aerosol dispersion in pediatric respiratory conditions.
Introduction:
In the past decades, aerosol bolus inhalation increasingly came into the focus of medical interest due to its potential as a non-invasive technique for the diagnosis of lung diseases. The experimental studies were accompanied by the development of theoretical contributions dealing with aerosol bolus behaviour in healthy and diseased lungs. In this study, bolus dispersion in healthy and asthmatic children is subject to a theoretical approach. Model predictions are validated with related experimental findings.
Methods:
Aerosol bolus transport was simulated by using (I) a stochastic model of the human respiratory tract; (II) appropriate scaling procedures for the generation of healthy and asthmatic lungs of children; and (III) the concept of effective diffusivities (Deff) for the prediction of convective mixing processes in the conducting airways and alveoli. The aerosol injected into the inhalative air stream consisted of monodisperse particles with a diameter of 0.4 µm (ρ =1 g∙cm(-3)). Volumetric lung depth, being a measure for the position of the aerosol bolus within the inspired air stream, was varied from 95 mL (shallow bolus) to 540 mL (deep bolus). Half-width of the inhaled bolus was set to 50 mL.
Results:
According to the predictions provided by the model, dispersion of the exhaled aerosol bolus increases exponentially with volumetric lung depth in both asthmatic children and healthy controls. Asthmatics tend to develop higher bolus dispersion than healthy subjects, with significant differences between the two groups being noticeable at low volumetric lung depths (<300 mL). Skewness decreases with increasing volumetric lung depth, whereby respective values calculated for asthmatics exceed those values computed for healthy subjects. Theoretical results correspond very well with experimental findings.
Discussion And Conclusions:
Results of experimental bolus studies may be approximated by theoretical models with high accuracy. Model predictions confirm the assumption that inhalation of aerosol boluses and dispersion measurements have only a limited diagnostic potential.
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