Capnography Flashcards
Advanced Monitoring and Procedures
Chapter 26 - Capnography
What is a capnogram
a continuous plot of respired CO2 of time
Whats the difference between a capnometer and a capnograph?
Capnometer - detects highest and lowest values (numbers)
Capnograph - graphical display
What is the difference between mainstream and sidestream capnography?
Mainstream - sample cell in-line - no sampling line needed. Crisper graphs are analysed in real time and gases in the sampling line are not diluted. can be bulky - easily broken
Sidestream - pump pulls gas up to sensor - can reduce deadspace - accuracy will depend on aspiration speed and sampling line length and diameter
How does moisture affect capnograph readings and how is this abated in the different systems?
Causes falsely increased - Mainstream - heated to reduce moisture.
Sidestream - moisture traps
What does ETCO2 represent?
Alveolar partial pressure of CO2 reflects a balance
between CO2 delivery to the alveoli by the cardiovascular
system and its removal by ventilation.
What is a normal Pco2?
35-45mmHg
What PaCO2 is generally considered significant enough to warrant IPPV under GA
60mmHg
What techniques of CO2 measurement exist?
IR absorption, Raman scattering and mass spec
How does IR work
CO2 has a specific absorption of light - capnograph measures light absorption and compares it to a reference standard –> what increases absorption light absorption therefore will falsely increase ETCO2
What are some indications for capnography?
- ETT placement
- detect apnea
- monitor ventilation
- pulmonary perfusion
- malfunctioning equipment detection
- NGT detection - lol ok
what are the 4 phases on a capnograph?
I - inhalation and dead space exhalation
II- dead space exhalation and alveolar gas exhalation
III - plateau, alveolar gas exhalation
IV - downstroke with inspiration
