American Journal of Roentgenology, Vol 156, 1209-1214, Copyright © 1991 by American Roentgen Ray Society
John Caffey Award. Determination of functional residual capacity from digital radiographs of the normal neonatal chest: studies in a rabbit model
KS White, AA Muelenaer Jr, CA Beam and EL Effmann
Department of Radiology, Duke University Medical Center, Durham, NC 27710.
Spirometric measurement of lung volume in an infant or uncooperative child
is often a difficult and time-consuming procedure. Previous investigators
have successfully estimated total lung capacity in adults and older
children by using chest radiography. The purpose of this study was to
assess the accuracy of functional residual capacity (FRC) determination
from chest radiographs in an animal model of the normal neonatal chest. FRC
was determined with the helium dilution (HeD) method in 13 anesthetized,
intubated, and paralyzed rabbits (weight range, 1.5-3.9 kg). FRC was then
estimated from digital frontal and lateral chest radiographs. The
radiographic estimate was made by applying measurements taken from the
radiographic film pair to a geometric model of the chest. The best-fit
model assumed an elliptical cross section for the intrathoracic cavity,
heart, paraspinal structures, and diaphragm in the axial plane. Linear
regression on independently determined HeD and radiographically determined
FRC yielded a slope of 1.02 (p less than .001), an intercept of -3.02 cm3
(p = .565), and a correlation coefficient of 0.96 (p less than .001). We
conclude that radiographic FRC estimates closely approximate HeD estimates
in a rabbit model of the normal neonatal chest.
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