Isoflurane was delivered to a section of corrugated tubing (∼150 ml, gray cylinder) in series with a pair of spring-loaded bellows (as shown on the right in the schematic), ventilated with tidal volume 500 ml and rate 20 min⁻¹: (a) characteristic trace of flow measured for two breaths; (b) corresponding tidal volume (solid) with real-time generation of actuating signal denoting anesthetic delivery window at the end of inspiration (dashed). The delivery threshold (V_th) was set to 300 ml to account for the delay in switching between sublimbs and engaging the anesthetic vaporizer; and (c) three traces of isoflurane concentration characterizing anesthetic distribution throughout the dead space compartment. Isoflurane concentration detected at the interface between dead space and alveolar compartments was negligible.