Capnography

Question 1

What is capnography?

Answer 1

The monitoring of the concentration or partial pressure of carbon dioxide (CO₂) in respiratory gases.

Question 2

In what settings is capnography primarily used?

Answer 2

During resuscitation, anaesthesia and intensive care.

Question 3

How is capnography usually displayed?

Answer 3

As a graph of expiratory CO₂ (in mmHg) plotted against time or expired volume.

Question 4

What does the capnogram show during rebreathing?

Answer 4

Inspired CO₂, which is important in rebreathing systems.

Question 5

What is end-tidal CO₂ (ETCO₂)?

Answer 5

The CO₂ measurement taken at the end of a breath (exhalation).

Question 6

What does a capnogram monitor directly?

Answer 6

Inhaled and exhaled concentrations or partial pressures of CO₂.

Question 7

What does a capnogram monitor indirectly?

Answer 7

The partial pressure of CO₂ in arterial blood.

Question 8

How different is expired gas CO₂ from arterial CO₂ in healthy individuals?

Answer 8

The difference is very small.

Question 9

What is ETCO₂ a measurement of?

Answer 9

Exhaled carbon dioxide (CO₂), a byproduct of cellular metabolism.

Question 10

What is ETCO₂ used for in the field?

Answer 10

To guide ventilator settings and monitor respiratory and pulmonary status.

Question 11

What is the normal ETCO₂ range?

Answer 11

35–45 mmHg.

Question 12

What is ETCO₂ used for during cardiac arrest?

Answer 12

To evaluate cardiac output and the effectiveness of chest compressions.

Question 13

What does the capnography waveform represent?

Answer 13

Exhaled CO₂.

Question 14

What are the phases of the capnogram?

Answer 14

Upstroke (CO₂ rises), Plateau (CO₂ stabilizes), Downstroke (start of inspiration).

Question 15

What is tidal volume?

Answer 15

The volume of air in a single breath, either spontaneous or assisted.

Question 16

When is ETCO₂ measured?

Answer 16

At the end of the tidal volume’s exhalation.

Question 17

What does the horizontal axis of a capnogram represent?

Answer 17

Time.

Question 18

What does a shorter waveform indicate?

Answer 18

A faster respiratory rate.

Question 19

What is the target ETCO₂ during compressions?

Answer 19

≥ 10 mmHg.

Question 20

What does ETCO₂ ≤ 10 mmHg indicate?

Answer 20

Poor chest compressions.

Question 21

What can a sudden ETCO₂ spike > 40 mmHg indicate?

Answer 21

Return of spontaneous circulation (ROSC).

Question 22

Why does ETCO₂ spike during ROSC?

Answer 22

Built-up CO₂ is rapidly pumped to the lungs when the heart starts beating.

Question 23

What is the post-ROSC target ETCO₂?

Answer 23

35–40 mmHg.

Question 24

What does ETCO₂ provide regarding ETT?

Answer 24

Continuous breath-by-breath confirmation of placement.

Question 25

What might a sudden ETCO₂ drop from 30 to 0 mmHg indicate?

Answer 25

ETT dislodgement.

Question 26

Why is ETCO₂ preferred over pulse oximetry during arrest?

Answer 26

It responds faster (immediate vs. 30–60 seconds).

Question 27

Why use ETCO₂ during arrest?

Answer 27

To assess chest compressions, detect ROSC, and monitor ETT placement.

Question 28

What does rapid breathing waveform look like?

Answer 28

Shortened waveform.

Question 29

What does breath-holding show?

Answer 29

A flat waveform.

Question 30

What is a colorimetric detector?

Answer 30

A paper device that changes color when exposed to CO₂.

Question 31

What color does the paper change from and to?

Answer 31

From purple to gold/yellow.

Question 32

What does 'Gold is golden' mean?

Answer 32

It indicates the presence of exhaled CO₂.

Question 33

Is the colorimetric detector 100% reliable for ETT placement?

Answer 33

No, it only confirms presence of exhaled CO₂.

Question 34

Where is the colorimetric detector placed?

Answer 34

Between the ETT and Ambu bag.

Question 35

What does it mean if it stays purple?

Answer 35

No CO₂ detected—possible poor perfusion or bad tube.

Question 36

What does it mean if it turns gold during resuscitation?

Answer 36

Possible ROSC.

Question 37

What are other ways to confirm tube placement?

Answer 37

Visualizing cords, no epigastric sounds, equal breath sounds, chest rise.

Question 38

What are the key reasons to use ETCO₂ in ACLS?

Answer 38

Assess perfusion, evaluate compressions, and confirm airway placement.