Abstract
After intravenous induction, six beagles were connected to a Komesaroff machine provided with a single in‐circuit vaporiser and ventilated mechanically at either nine or 14 breaths/minute while anaesthetised with either isoflurane or sevoflurane. The vaporiser was initially set at position 4/4 (fully open) and the anaesthetic concentrations were measured after one and five minutes; the vaporiser was then set at the lowest setting able to maintain anaesthesia. Cardiorespiratory variables were measured throughout the study. In most cases anaesthesia was maintained at setting 1/4 with isoflurane and at setting 1.5/4 or 2/4 with sevoflurane.