Article,
Model of forced expiratory flows and airway geometry in infants
JOURNAL OF APPLIED PHYSIOLOGY, 96 (2): 688-692 (February 2004)
DOI: {10.1152/japplphysiol.00843.2003}
Abstract
Early measurements of autopsied lungs from infants, children, and adults
suggested that the ratio of peripheral to central airway resistance was
higher in infants than older children and adults. Recent measurements of
forced expiration suggest that infants have high flows relative to lung
volume. We employed a computational model of forced expiratory flow
along with physiological and anatomic data to evaluate whether the
infant lung is a uniformly scaled-down version of the adult lung. First,
we uniformly scaled an existing computational model of adult forced
expiration to estimate forced expiratory flows (FEF) and density
dependence for an 18-mo-old infant. The values obtained for FEF and
density dependence were significantly lower than those reported for
healthy 18-mo-old infants. Next, we modified the model for the infant
lung to reproduce standard indexes of expiratory flow forced
expiratory volume in 0.5 s (FEV0.5), FEFs after exhalation of 50 and
75\% forced vital capacity, FEF between 25 and 75\% expired volume for
this age group. The airway sizes obtained for the infant lung model that
produced accurate physiological measurements were similar to anatomic
data available for this age and larger than those in the scaled model.
Our findings indicate that the airways in the infant lung model differ
from those in the scaled model, i.e., middle and peripheral airway sizes
are larger than result from uniform downscaling of the adult lung model.
We show that the infant lung model can be made to reproduce individual
flow-volume curves by adjusting lumen area generation by generation.
