Respiratory mechanics and lung histology in normal rats anesthetized with sevoflurane

Respiratory system, lung, and chest wallmechanical properties were subdivided into their resistive, elastic,and viscoelastic/inhomogeneous components in normal rats, to define thesites of action of sevoflurane. In addition, we aimed to determine theextent to which pretreatment with atropine modified theseparameters. Twenty-four rats were divided into four groups ofsix animals each: in the P group, rats were sedated (diazepam) andanesthetized with pentobarbital sodium; in the S group, sevoflurane wasadministered; in the AP and AS groups, atropine was injected 20 minbefore sedation/anesthesia with pentobarbital and sevoflurane,respectively. Sevoflurane increased lung viscoelastic/inhomogeneouspressures and static elastance compared with rats belonging to the Pgroup. In AS rats, lung static elastance increased in relation to theAP group. In conclusion, sevoflurane anesthesia acted not at the airwaylevel but at the lung periphery, stiffening lung tissues and increasing mechanical inhomogeneities. These findings were supported by the histological demonstration of increased areas of alveolar collapse andhyperinflation. The pretreatment with atropine reduced central andperipheral airway secretion, thus lessening lung inhomogeneities.