11-3
11.2 Calibration
Every vaporizer is individually set at 22℃ and at a continuous air flow of 2 L/min without ventilation
pressure, and tested at 22℃ as well as 2 L/min.
Calibration is in % partial pressure as the depth of anesthesia depends on the patient’s uptake which is
itself determined by partial pressure. Concentration delivered in % partial pressure at normal pressure
of 101.3 kPa is identical numerically with the output given in volume percent, so the scale values on
the control dial of the vaporizer given in vol.%, shows the concentration delivered at 22℃ with dry
gases (see A Product Specifications).
The output in vol.% must be corrected for other atmospheric pressure values (see 11.6 Influence of
Atmospheric Pressure) but partial pressure always remains constant.
For simplicity, settings on the vaporizer and in the Operator’s Manual are given in the abbreviated
form of vol.%, which means vol.% at 101.3 kPa.
11.3 Influence of Temperature
The saturation concentration of the anesthetic agent rises as temperature rises. The concentration
deviation is automatically compensated by routing a higher proportion of the gas flow through the
vaporizer bypass system.
The linear change of the bypass valve changes the flow through the bypass in a non linear manner .For
the full temperature range, the non linear manner does not match perfectly the non linear variation of
the partial pressure, so that the vaporizer cannot fully compensate the concentration deviation resulting
from changes in temperature and the concentration delivered remains slightly dependent on
temperature.
WARNING
z Under no circumstances should the vaporizer ever be used at atmospheric pressure and
temperature at which the anesthetic agent could start to boil, as the concentration
delivered will rise and be uncontrolled.
To Next Page
Loading...
Need help?
General
