Journal of Applied Physiology, Vol 51, Issue 3 699-705, Copyright © 1981 by American Physiological Society
Changes in distribution of ventilation with lung growth
D. M. Cooper, R. B. Mellins and A. L. Mansell
We systematically studied the effects of varying preinspiratory lung
volumes and expiratory flow rates on the alveolar plateau of the
single-breath oxygen test in children and adults. With inhalations of
oxygen beginning at functional residual capacity (FRC) compared with
residual volume (RV), the slope of phase III increased in 52 of 54 children
and 6 of 6 adults (mean increase 29.2%, P less than 0.001) but then
decreased at preinspiratory volumes greater than FRC. With maximal
expiratory flows, the slopes were smaller than slopes from conventional
maneuvers in 14 of 15 children by a mean 24.1%, P less than 0.001. These
data suggest that apex-to-base differences in regional lung volume are a
major determinant of the slope. Slopes (FRC maneuver) decreased as a
function of the height of the children (r = -0.73, P less than 0.001), but
differences in nitrogen concentration over the alveolar plateau increased
with height (r = 0.70, P less than 0.001). This indicates that the
apex-to-base differences in regional lung volume increase with lung size.
An estimate of mixing efficiency between resident and inspired gas derived
from the alveolar plateau increased with height for both RV (r = 0.40, P
less than 0.005) and FRC maneuvers (r = 0.45, p less than 0.005) and was
greater for FRC than RV (P less than 0.001). These increases in mixing
efficiency are consistent with previously demonstrated decreases in closing
volume with growth.
