Capnography (Exam I)

Question 1

What are the effects of hypercarbia?

Answer 1

• Respiratory Acidosis
• ↑ CBF
• ↑ PVR
• K⁺ shift intravascularly

Question 2

What are the effects of hypocarbia?

Answer 2

• Respiratory alkalosis
• ↓ CBF
• ↓ PVR
• K⁺ shift intracellulary
• Blunts respiratory drive

Question 3

What is the Bohr equation?
What is it used for?

Answer 3

Used to calculate physiologic dead space

Question 4

What is the best method to confirm endotracheal tube placement?

Answer 4

Capnography

Question 5

Differentiate high-speed (real-time) and low speed (trend capnography).

Answer 5

Question 6

How much gas do side-stream analyzers utilize?

Answer 6

200 mL/min sample rate

Question 7

What is the most common method for capnographic sampling, side-stream or main-stream sampling?

Answer 7

Side-stream

Question 8

What are the benefits of main-stream sampling?

Answer 8

• No time delay
• quicker rise time

Question 9

What approximate difference is there between PaCO₂ and EtCO₂ ?

Answer 9

5 mmHg

ex. PaCO₂ will be 40 mmHg vs EtCO₂ at 35 mmHg

Question 10

What color is the CO₂ chemical indicator?
What color does it change to in the presence of CO₂ ?

Answer 10

purple → yellow

Question 11

When using a capnograph, how close must a CO₂ reading be to the actual value?

Answer 11

+/- 12%

Question 12

What are the inspiratory phases of the capnograph?

Answer 12

Phase 0

Question 13

What are the expiratory phases of the capnograph?

Answer 13

Phases I, II, and III

Question 14

When would the CO₂ reading of a capnograph be 0 mmHg ?

Answer 14

Phase I

Question 15

Which phase of the capnograph would be representative of alveolar CO₂ ?

Answer 15

Phase III

Question 16

Where on the capnograph is EtCO₂ measured?

Answer 16

Phase III

Question 17

What is a phase IV in the capnograph? Why does it occur?

Answer 17

Upstroke at the end of Phase III resulting from collapse of alveoli.

Question 18

What patient populations might exhibit a Phase IV on their capnograph?

Answer 18

• Obese
• Pregnant

Question 19

What phases are separated by the β angle?

Answer 19

Phase III and 0

Question 20

What degree should the α angle have?
What occurs with increase to the angle’s degree?

Answer 20

• 100 - 110°
• Increased angle occurs with expiratory airflow obstruction (COPD, ETT, bronchospasm, etc)

Question 21

What degree should the β angle have?

Answer 21

90°

Question 22

What situations/conditions would cause an increase in the β angle?

Answer 22

• Bad inspiratory valve
• Rebreathing
• Low V_T w/ tachypnea

Question 23

What type of capnograph is depicted below?

Answer 23

Mechanical Ventilation

Question 24

What type of capnograph is depicted below?

Answer 24

Spontaneous Ventilation

Question 25

What is occurring with the capnograph below?

Answer 25

Inadequate ETT seal

Question 26

What might be occurring based on the two capnographs below?

Answer 26

Faulty Inspiratory Valve

Question 27

What is occurring with the capnograph below?

Answer 27

Likely sample line leak

Question 28

What is occurring with the capnograph below?

Answer 28

Hyperventilation (resulting in a ↓ EtCO₂)

Question 29

What is occurring with the capnograph below?

Answer 29

Hypoventilation (resulting in steady ↑ EtCO₂)

Question 30

What is occurring with the capnograph below?

Answer 30

Airway obstruction or breathing circuit obstruction

Question 31

What is occurring with the capnograph below?

Answer 31

Cardiac oscillations

Question 32

What is occurring with the capnograph below?

Answer 32

Rebreathing (note the increasing baseline)

Question 33

What is occurring with the capnograph below?

Answer 33

Curare Cleft (NMBDs are wearing off)

Question 34

What is occurring with the capnograph below?

Answer 34

Ventilator overbreathing

Question 35

What is occurring with the capnograph below?

Answer 35

Esophageal Intubation (the ol’ tubed goose)