Relationship of ventilation inhomogeneity to morphologic variables in excised human lungs

Ventilation inhomogeneity, as assessed by the regional distribution of ¹³³Xe and the single breath washout (SBW) curve, is compared with the morphologic aspects in excised human lungs. Morphologic measurements include central airway diameter, bronchial gland area, peripheral airway diameter, and the alveolar surface-to-volume ratio. Lung inflation with a constant concentration of ¹³³Xe results in the relatively more ¹³³Xe distributed to the lung base than to the apex. Neither the vertical gradient in ventilation nor other interregional inhomogeneities in ¹³³Xe distribution are correlated with morphologic variations in the lung. Also, interregional inhomogeneities of ¹³³Xe distribution do not correlate with phase II slope of the SBW curve. This suggests that the phase II sloop is determined primarily by intraregional ventilation inhomogeneities. Within the phase IV region of SBW curve two distinct inflections are identified: an inflection at volume V1 and another sharper inflection at volume V2. Both the phase III slope and V2 correlate significantly (p < 0.05) with peripheral airway diameter, indicating that parameters of the SBW curve do assess peripheral airway properties.