N. Shinozuka et al., ISOVOLUME BRONCHOCONSTRICTION BY VAGAL-STIMULATION IN DOGS - EFFECTS OF LUNG-INFLATION PRESSURE, Respiration physiology, 111(1), 1998, pp. 79-88
The changes elicited in lung mechanics by a given stimulus to the airw
ay smooth muscle depend significantly on end-expiratory lung volume. H
owever, the precise quantitative relationship between volume (or infla
tion pressure) and airway responsiveness remains to be elucidated. We
measured the changes in lung elastic recoil pressure and impedance at
1 and 8 Hz, produced in anesthetized, paralyzed, open-chest dogs over
periods of 32 sec, when the vagus nerves were continuously electricall
y stimulated at constant lung volume. The increases in lung elastic re
coil pressure increased with PEEP, which we interpret as being due to
parenchymal distortions produced by the contracting airways acting aga
inst parenchymal attachment forces that increase with lung volume. In
contrast, the increases in lung resistance al 1 and 8 Hz and elastance
at I Hz all decreased by several-fold as PEEP was increased, which we
interpret as reflecting the decreased airway smooth muscle shortening
that was achieved with increasing parenchymal load. (C) 1998 Elsevier
Science B.V.