Pilbeams Chapter 10

Question 1

The measurement of CO2 in respired gases

Answer 1

Capnometry, Capnography

Question 2

Handheld devices composed of specially treated filter paper in a plastic casing the ET tube. The amount of CO2 in the inspired and expired gas can be measured by noting the color changes in the filter paper.

Answer 2

Chemical Method (Colorimetric) Capnometers

Question 3

Based on the principle that molecules containing more than one element absorbs light in a characteristic manner.

Answer 3

Infrared Spectroscopy
-CO2 absorbs IR radiation maximally at 4.26 um
-The concentration in a gas sample can be measured estimated because its concentration is directly related to the amount of CO2 absorbed.
-The presence of other gases (H2o, Nitrous oxide) can adversely affect the accuracy of CO2 measurements.

Question 4

Physiologic Considerations

Answer 4

Inspired air contains 0.03% of CO2
Expired air contains 4.5% to 5.5% of CO2 (cellular metabolism)

Question 5

What is the normal PetCO2?

Answer 5

4 to 6 mm HG lower than the Paco2 and the PACO2 and the PaCO2 are almost equal.