The Tec 6 desflurane vaporiser
Desflurane needs to be heated by a electrically powered heating element (H) to 39 °C, at which its SVP is approximately 1300 mmHg. The carrier gas flow is restricted by an orifice (O) so that the pressure of the carrier gas within the vaporiser is proportional to gas flow. This pressure is sensed by a differential pressure transducer (P), which adjusts a resistor (R1) so that the flow of desflurane out of the vaporising chamber is proportional to the carrier gas flow. This enables the output concentration to be made independent of carrier gas flow rate. The control dial adjusts a second resistor (R2), which controls the output of desflurane gas, and thus the output concentration.
Source: http://www.frca.co.uk/article.aspx?articleid=100151
