Study objective: To assess the effects of emphysema on
the apex-to-base gradient of lung density (D) and lung mass (M)
and to explore the relationship between M and lung function.
Methods: CT scans of whole lungs were performed in 12
healthy subjects and 29 patients who were breathing at functional
residual capacity, after which lung function tests were performed.
Whole D and M and regional D (RLD) and M (RLM) were calculated.
The degree of emphysema was scored.
The RLM for each height did not differ significantly between patients
with disease and healthy subjects, while RLD was significantly lower in
the patients with disease. A less marked nonlinear, increasing,
craniocaudal gradient of D was observed in the group with disease,
suggesting that the distension increases progressively from the apex to
the base. RLD and RLM in the 40 to 90% lung height differed
significantly among patients in the emphysema group with normal, high,
and low M compared to the healthy subjects. M did not differ
significantly between patients with centrilobular and panlobular
emphysema, which was thought to stem from the marked variations in the
results. Vital capacity was lower in the patients with low M.
Conclusions: The lower RLD in the group with low M was due
to both lung overinflation and to tissue loss, while in the groups with
high or normal M, it was due only to lung