Respiratory mechanics and lung histology in normal rats anesthetized with sevoflurane

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.