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.