Q: Define capnometry vs capnography.
A: Capnometry = CO₂ measurement (number); Capnography = graphic display (waveform)
Q: Most common technology for capnometry?
A: Infrared absorption
Q: Mainstream sampling – one advantage & one disadvantage?
A: Advantage = fast response; Disadvantage = bulky, condensation
Q: Sidestream sampling – one advantage & one disadvantage?
A: Advantage = good for nonintubated patients; Disadvantage = slower, blockage risk
Q: What are the phases of a normal capnogram?
A: Phase I (deadspace), Phase II (rise), Phase III (alveolar plateau), PETCO₂ at end
Q: How does PETCO₂ normally compare to PaCO₂?
A: PETCO₂ is 3–5 mmHg less
Q: 2 uses for capnography in clinical practice?
A: Confirm ETT placement, monitor CPR effectiveness
Q: What is a major hazard of capnography?
A: Misinterpretation → incorrect treatment
Q: What does Point A on the capnogram represent?
A: Start of exhalation (dead space gas, no CO₂).
Q: What does the upstroke (A→B) represent?
A: CO₂ rising as alveolar gas mixes in.
Q: What does the plateau (B→C) represent?
A: Alveolar gas, steady CO₂ concentration.
Q: What does Point C represent?
A: End of exhalation; EtCO₂ is measured here.
Q: What happens to the capnogram during inhalation?
A: CO₂ drops back to zero.
Q: What does PetCO₂ stand for?
A: End-tidal CO₂ – CO₂ measured at the end of exhalation.
Q: Normal PetCO₂ value?
A: 35–45 mmHg
Q: Why is PetCO₂ slightly lower than PaCO₂?
A: Because of dead space—air that doesn’t participate in gas exchange dilutes CO₂.
Q: What does a high PetCO₂ indicate?
Q: What does a high PetCO₂ indicate?
Q: What does a low PetCO₂ indicate?
A: Hyperventilation → body blowing off too much CO₂.
PaCO₂ Value?
(partial pressure of carbon dioxide in arterial blood)
35-45 mmhg
PetCO₂ stands for?
End-tidal CO₂ pressure.
