End-tidal carbon dioxide (CO₂) monitoring in small animals

A simple modification of a commericially available capnometer (Traverse Medical Monitors model 2000) is described which suits it for use with small animals such as rats. The modification involves the omission of the fluids separator from the gas pathway, while maintaining a connection to the separator to permit the continued function of the "automatic zero" feature, which corrects for any zero-drift. The capnometer has several functions which recommend its use even when artificial ventilation is not required.