Physics of capnography
Bhavani Shankar Kodali MD
Factors affecting IR Spectrography
Oxygen does not absorb IR light
Oxygen does have affect via collision broadening effect
How does oxygen affect CO2 measurements?
|Oxygen does not absorb IR light|
|Oxygen produces collision broadening phenomena that can cause falsely low CO2 measurements.|
Although oxygen does not absorb IR light it may indirectly affect the absorption by C02 by collision with the C02 molecules and broadening the absorption peak. While it does not cause as large an effect as N20, oxygen causes a falsely low C02 reading. Some units automatically correct or have a user-actuated electronic offset for the concentration oxygen encountered.1
1. Carbon dioxide monitors. Health Devices 1986;15:255-85.