Hypercapnic Spontaneous Hyperpnoea and Recovery From Sevoflurane Anesthesia

The rate of elimination of inhalation agent is directly proportional to the degree of alveolar ventilation. Using Isocapnic Hyperpnoea (IH) device, it is possible to maintain constant end-tidal CO2 with increased minute ventilation. This is achieved by passively adding a flow of CO2 to the inspirate in proportion to increases in ventilation above the baseline. In animal and human studies IH shortens the time of awakening from isoflurane and sevoflurane anesthesia when manual positive pressure ventilation is applied. IH device could be used for spontaneous hyperpnoea as well. The investigators want to compare recovery times from sevoflurane anesthesia in patients with application of hypercapnic spontaneous hyperpnoea (HSH) versus the standard anesthesia protocol (controls). 44 patients ill be randomized to either HSH facilitated recovery, or conventional recovery (controls).The time intervals from the end of anesthesia (turning off the vaporizer) until recovery milestones will be recorded.