Stratified impairment of pulmonary ventilation in "diffuse panbronchiolitis:" PET and CT studies.

Positron emission tomography with radioactive nitrogen gas as well as CT were performed in seven patients with diffuse panbronchiolitis (DPB) to evaluate regional changes on pulmonary ventilation and lung attenuation values. Special focus of this study was on the difference between the central and peripheral parts of the lung. Mean ventilatory time constants measured in the peripheral parts of the lung were significantly greater than those in the central parts. Moreover, mean CT attenuation values in the peripheral parts were also significantly lower than those in the central parts, indicating that hyperinflation of the lung in DPB was located mainly in the peripheral parts. Such stratified distribution of ventilatory impairment is considered to be characteristic of diffuse bronchiolar narrowing because, in the peripheral parts of the lung, there are no large airways. In addition, different branching patterns of airways between the central and peripheral parts of the lung may play an important role in the mechanism of selective injury of bronchioles in the peripheral parts.