The Tec 6 vaporizer: why desflurane needs to be heated

The Ohmeda Tec 6 was designed as an agent-specific vaporizer for desflurane. Its exterior framework offers some unique features. Aside from its unique filling port, broad calibration range, and additional light-emitting diodes (LEDs), its large size literally sets it apart from all other models. As distinctive as the exterior appears, its interior design is even more unconventional; that is, it is not a variable-bypass, flow-over system. There are no mixing chambers, baffles, or temperature-sensing bellows; a differential pressure transducer system takes their place. Many modifications were made primarily to accommodate the remarkably high vapor pressure of desflurane. This is especially true in regard to the sump heating unit. Although there are many options to accommodate a high vapor pressure, a heating unit serves the purpose best. A brief review of vaporization and fundamental thermodynamics will demonstrate why this is so.