Journal of Applied Physiology, Vol 41, Issue 2 185-190, Copyright © 1976 by American Physiological Society
Xenon and nitrogen single-breath washout curves in patients with airway obstruction
M. Demedts, M. de Roo, J. Cosemans, L. Billiet and K. P. van de Woestijne
In patients with chronic obstructive lung disease, we determined
single-breath N2 and 133 Xe washout curves, and regional distributions of
volumes (Vr) and of 133Xe boluses inhaled at residual volume (VIRV).
Patients suffering from emphysema with minimal airway obstruction
demonstrated large closing volumes and apicobasal distribution gradients,
apparently because of a steep pulmonary recoil pressure-volume curve. In
one subject with basal small airway disease there was no vertical gradient
in regional residual volume; closing volume was increased with the 133Xe
technique but almost absent with the N2 technique. Patients with
moderate-to-severe airway obstruction had upward-sloping alveolar plateaus
without distinct phase IV, and small apicobasal differences in Vr and VIRV.
The latter resulted probably from increased regional differences in time
constants counteracting the influence of gravity. Finally, patients with
severe airway obstruction and basal emphysema demonstrated a rising N2 but
a descending 133Xe plateau; the gradient for VIRV was normal, and reversed
for Vr. This pattern was attributed to nongravitational differences in time
constants causing a first in-first out distribution.
