Data Analysis
Four volume compartments were defined from the formatted gray-scale MRI images according to a previously published analysis platform (see E-supplement) 11, 21. VH indicators included the Vdef % (non-ventilated volume/total lung volume), and the VHI % (non-ventilated +hypoventilated volume/total lung volume).
To examine whether the magnitude of VH informed clinical features, the sample was stratified into three sub-groups according to the quartile distribution of the VHI %. Sub-group one, mild VH, was < 25th %ile VHI %, sub-group two, moderate VH, middle 25th -75th %ile, and sub-group three, severe VH, was > 75th %ile. Between sub-group comparisons among scaled and categorical variables are described in the E-supplement. BAL granulocyte patterns were defined as isolated eosinophilia, isolated neutrophilia, mixed granulocytic, and pauci-granuolocytic based on published criteria 19, 23. A p value of < .05 was used to refute the null hypothesis.