Faster recovery from anesthesia is important for obese patients because they are at high risk of respiratory complications following tracheal extubation. Isoflurane has several properties that make it a preferable agent for anesthesia in obese patients. Its main limitation is a longer recovery time due to slower elimination in comparison to other agents. Elimination of isoflurane from the lungs can be accelerated by increasing in patient's minute ventilation, which decreases the level of CO2 in blood (hypocapnia).Isocapnic Hyperpnoea (IH) is a method allowing increased ventilation and therefore enhancement of the elimination of inhalation agents while maintaining a normal blood CO2 level. The investigators will compare recovery time from isoflurane anesthesia in obese patients during standard anesthesia management protocol (control) to a group treated with IH.