If the baseline is elevated more than approximately 2 mm Hg CO2, the patient is receiving CO2 during inspiration, and this is often termed rebreathing.
• An exhausted CO2 absorber and unrecognized dye indicator
• Channeling of the gas within the CO2 absorber and unrecognized dye indicator
• An incompetent unidirectional inspiratory or expiratory valve, often in circle systems
• Accidental administration of CO2 (perhaps from a CO2 tank used for laparoscopy)
• Bicarbonate administration
• Tourniquet release
• Inadequate fresh gas flow
• Sepsis and other hypermetabolic event (fever, malignant hyperthermia)
