Respiratory system, lung, and chest wall mechanical properties were subdivi
ded into their resistive, elastic, and viscoelastic/inhomogeneous component
s in normal rats, to define the sites of action of sevoflurane. In addition
, we aimed to determine the extent to which pretreatment with atropine modi
fied these parameters. Twenty-four rats were divided into four groups of si
x animals each: in the P group, rats were sedated (diazepam) and anesthetiz
ed with pentobarbital sodium; in the S group, sevoflurane was administered;
in the AP and AS groups, atropine was injected 20 min before sedation/anes
thesia with pentobarbital and sevoflurane, respectively. Sevoflurane increa
sed lung viscoelastic/inhomogeneous pressures and static elastance compared
with rats belonging to the P group. In AS rats, lung static elastance incr
eased in relation to the AP group. In conclusion, sevoflurane anesthesia ac
ted not at the airway level but at the lung periphery, stiffening lung tiss
ues and increasing mechanical inhomogeneities. These findings were supporte
d by the histological demonstration of increased areas of alveolar collapse
and hyperinflation. The pretreatment with atropine reduced central and per
ipheral airway secretion, thus lessening lung inhomogeneities.