Asymmetric lung increases particle filtration by deposition

Area of Science:

• Pulmonary physiology
• Biophysics
• Respiratory system mechanics

Background:

• Human lungs feature an asymmetric, dichotomously branched bronchial network.
• Previous studies linked lung asymmetry to airflow dynamics, but its role in defense is less explored.

Purpose of the Study:

• To investigate the role of lung asymmetry in protecting the acinus from high pathogen loads.
• To explore the structure-function relationship in realistic bronchial tree models.

Main Methods:

• Development of mathematical models of bronchial trees based on morphometric parameters.
• Simulation of particle deposition and airflow dynamics within the modeled lung structures.

Main Results:

• Symmetric lung models optimize surface area for gas exchange, minimize resistance, and reduce volume.
• Lung asymmetry enhances the deposition of inhaled foreign particles in non-terminal airways.
• Optimal asymmetry for particle filtration is close to values observed in human lungs, offering enhanced defense.

Conclusions:

• Human lung asymmetry represents a trade-off between optimal gas exchange and enhanced protection against inhaled pathogens.
• Typical human lungs exhibit increased fluidic resistance and reduced gas exchange surface area for improved particle filtration.
• This structural adaptation provides robust defense against pathogen-laden aerosols, crucial for host survival.