Effects Of Variables; Anesthetic Agent Consumption; Barometric Pressure - Datex-Ohmeda Tec 7 User's Reference Manual

Tec 7 Vaporizer

Effects of variables

Anesthetic agent
consumption
Isoflurane, Halothane
and Enflurane
Sevoflurane

Barometric pressure

7-8
The rate of consumption of anesthetic agent depends primarily on flowrate and vapor
output concentration. As an approximate working figure, 1 milliliter of liquid
anesthetic is required to provide 200 milliliters of vapor.
The approximate hourly consumption of anesthetic agents can be expressed as
3 x % x F, where % represents the setting of the vaporizer output percentage and F
represents the input flowrate in liters/minute.
Example: If a vaporizer is set to deliver 2% at 6 liters/minute total gas
input flowrate then the approximate rate of consumption
= 3 x 2 x 6 = 36 ml/hour.
The figures are approximate and are intended for general guidance only.
The rate of consumption of anesthetic agent depends primarily on flowrate and vapor
output concentration. As an approximate working figure, 1 milliliter of liquid
anesthetic is required to provide 200 milliliters of vapor.
The approximate hourly consumption of anesthetic agents can be expressed as 3.3 x
% x F, where % represents the setting of the vaporizer output percentage and F
represents the input flowrate in liters/minute.
Example: If a vaporizer is set to deliver 2% at 6 liters/minute total gas
input flowrate then the approximate rate of consumption
= 3.3 x 2 x 6 = 39.6 ml/hour.
The figures are approximate and are intended for general guidance only.
The Tec 7 Vaporizer is calibrated in percent v/v at 760 mmHg. If the ambient pressure
changes the % v/v changes, so that at an ambient pressure P mmHg the delivered
percentage (D% v/v) is calculated as follows:
% x 760
D =
where % is the nominal setting of the vaporizer.
P
To obtain a consistent depth of anesthesia when gross changes of barometric
pressure occur, the % v/v must be changed in inverse proportion to the barometric
pressure.
The vaporizer automatically makes this % v/v change and for practical clinical
purposes the effects of barometric pressure can be ignored.
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