Vaporizers

Question 0

Define Saturated Vapor Pressure

Answer 0

• The gas phase above the the liquid is aid to be saturated when it contains all the anesthetic vapor it can hold at a given temperature.
• The pressure exerted by the vapor is referred to as its SVP at that temp.

Question 1

Volatile anesthetic agents

Answer 1

• At room temperature, all gaseous forms of common anesthetic agents exist as vapors
• Volatility depends on SVP
• SVP depends on temperature

Question 2

Saturated vapor mixes with the bypass flow. Why?

Answer 2

The bypass flow will dilute it to the concentration set on the dial

Question 3

The concentration dial on the vaporizer _________…?

Answer 3

Sets the ratio of how much gas goes through the bypass and how much goes through the sump.

Question 4

Why must each vaporizer be agent specific?

Answer 4

• Because its based on the saturated vapor pressure of that agent

Question 5

What is the splitting ratio?

Answer 5

vaporizing chamber flow rate : bypass pathway flow rate

Question 6

What was developed to prevent the dilution of anesthetic agent with high flows?

Answer 6

Wicking - inside the vaporizers there are wicks that bring the anesthetic up to increase the surface area for the gas to better pick up the anesthetic agent

Question 7

Why are vaporizers temperature compensated?

Answer 7

• Heat of vaporization

- Since vaporization is a temperature process, if no heat is added, vaporizer output would decline

Question 8

Why is desflurane different?

Answer 8

• Des boils at room temperature (23.5 C)
• A conventional vaporizer would require really high flows to dilute it down to acceptable concentration
• We overcome this issue by heating Des to 2 atm to make it more stable and then inject it into the fresh gas flows.