Ventilation heterogeneity in ex-smokers without airflow limitation

Area of Science:

• Pulmonary Medicine
• Radiology
• Medical Imaging

Background:

• Hyperpolarized helium-3 MRI reveals ventilation abnormalities in ex-smokers without airflow limitation.
• The clinical significance of these ventilation defects is not fully understood.

Purpose of the Study:

• To phenotype healthy ex-smokers based on normal versus abnormally elevated ventilation defect percent (VDP) using hyperpolarized helium-3 MRI.
• To investigate the relationship between VDP and imaging markers of emphysema and airway morphology.

Main Methods:

• Sixty ex-smokers underwent hyperpolarized helium-3 MRI, CT scans, and pulmonary function tests.
• Measurements included VDP, apparent diffusion coefficients (ADCs), emphysema (RA950), and airway morphology (WA%, LA, LA/BSA).

Main Results:

• 42 ex-smokers had elevated VDP, showing no significant differences in pulmonary function or CT measures compared to 18 with normal VDP.
• Elevated VDP correlated with increased regional (3)He ADC, suggesting altered gas diffusion.
• Regional VDP also correlated with specific CT airway morphology parameters.

Conclusions:

• Abnormally elevated VDP in ex-smokers without airflow limitation is associated with subclinical lung changes.
• These findings suggest a phenotype of subclinical obstructive lung disease characterized by mild emphysema and regional airway remodeling.