Gas analysis principles

Sampling anaesthetic gases

Side stream vs mainstream

Side stream analysis

• Mixing of gases in the sample tubing may occur
• Small lag (usually not significant)
• Used for many gases

Mainstream analysis

• No lag (nil transit time)
• Bulky
• May increase dead space
• Limited to CO2 and O2

Radiation absorption

2 laws describes how radiations are absorbed as it passes through a solution

Beer's law

The absorption of radiation by a given thickness of a solution of a given concentration is the same as that of twice the thickness of a solution of half the concentration.

Lambert's law

aka Bouguer's law

Each layer of equal thickness absorbs an equal fraction of radiation which passes through it.