The closed circuit calorimeter uses a volumetric spirometer, a mixing chamber, a carbon dioxide analyzer and a carbon dioxide absorber. The spirometer is filled with a known volume of oxygen. As the patient rebreathes, oxygen is consumed and carbon dioxide is produced. Carbon dioxide is removed from the system by a carbon dioxide absorber. Expired gas from the patient is analyzed for the fractional concentration of carbon dioxide in expired gas (F E CO2). The volume of the spirometer is monitored to measure tidal volume (VT). The difference between end-expiratory volumes is calculated by a microprocessor to determine V O2. If the patient is mechanically ventilated, a bag-in-the-box system is used as a part of the inspiratory limb of the calorimeter. The bellows is pressurized by the ventilator, resulting in ventilation of the patient. Leaks from the closed circuit system result in erroneously high V O2 measurements (uncuffed airway, bronchopleural fistula, sidestream capnograph). Another problem with this technique is related to ventilatory support, where compressible volume is increased and trigger sensitivity is decreased. The major advantage of the closed circuit method over the open circuit method is its ability to make measurements at a high FiO2 (up to 1.0). It’s your turn to find cialis super active online pharmacy for treatment to see how advantageous your shopping can be.