Hallen K, et al. - An inquiry was initiated regarding the utility of a technique for CO₂ delivery (DCO₂) to the inspiratory limb of a closed breathing circuit, during hyperventilation (HV), to achieve isocapnia. This study validated a DCO₂ nomogram for IHV. The patients were safely extubated shortly after discontinuing long-term sevoflurane anaesthesia. Perioperatively, no adverse effects were disclosed on arterial blood gases or post-operative cognition. This technique for IHV could be potentially used for decreasing the emergence time from inhalation anaesthesia.