Capnography has the unique ability to aid clinicians in assessing both ventilation and blood flow. In this program, a review of the physiology that allows exhaled CO2 to monitor ventilation and perfusion is presented. The emphasis in this program is using capnography to prevent over-sedation and monitoring of blood flow. Due to the ability to assess both ventilation and perfusion, capnography has been called the “15-second vital sign”. The use of capnography is likely to quickly grow throughout the hospital and even into pre-hospital settings.