EtCO2 Theory

Question 1

What is the definition of respiration?

Answer 1

The process by which oxygen and carbon dioxide diffuse in and out of the blood

Question 2

What is the definition of ventilation?

Answer 2

Ventilation is the act or process of inhaling and exhaling – “movement of air”.
Pulmonary ventilation is the process by which oxygen enters and carbon dioxide exits the alveoli.

Question 3

What is the definition of oxygenation?

Answer 3

Refers to the process of adding oxygen to the body system – how we get O2 to the tissues.

Question 4

What are the positives of using EtCO2 monitoring?

Answer 4

• Provides reading for every breath – so results are within seconds
• Not affected by motion/circulatory status
• 100% sensitive and 100% specific

Question 5

What is dead air space/dead space?

Answer 5

Ventilated Areas that do not participate in gas exchange. Can be extended or made smaller based on airway interventions (example: extended by tubing, made smaller by inflated King LT cuff).

Question 6

What is a normal EtCO2 measurement?

Answer 6

35-45 mmhg

Question 7

If EtCO2 is lower than 35 mmHg, what does this generally mean?

Answer 7

Hyperventilation/hypocapnia

Question 8

If EtCO2 is higher than 45 mmHg, what does this generally mean?

Answer 8

Hypoventilation/hypercapnia

Question 9

What is quantitative ETCO2?

Answer 9

A measurement tool that gives us a number (ex: 38mmHg)

Question 10

What is qualitative ETCO2?

Answer 10

Devices that give a range (“low” “medium” “high”), often associated with a colour, instead of a number.

Question 11

What does PaCO2 stand for?

Answer 11

Partial Pressure of Carbon Dioxide in arterial blood gases.

Question 12

How will we know what the PaCO2 is?

Answer 12

PaCO2 should equal EtCO2 if ventilation and perfusion are stable.

Question 13

What does point D represent?

Answer 13

Where ETCO2 is measured.

Question 14

What does a low ETCO2 mean early in a code?

Answer 14

Likely Poor CPR (or extended down time).

Question 15

What does a low ETCO2 mean later in a code run?

Answer 15

Decreased likelihood of ROSC/extended downtime.
Low survivability.

Question 16

Why does bronchospasm result in the sloped “shark fin” waveform?

Answer 16

Because the movement of air at the alveoli is delayed in a person with bronchospasm, the rise to the plateau is more gradual and the plateau itself becomes sloped.

Question 17

What is a sidestream ETCO2 measurement?

Answer 17

• An indirect method of measuring exhaled CO2 in non-intubated patients.
• Pt’s with Respiratory complaints.

Question 18

What is a mainstream/inline ETCO2 measurement?

Answer 18

Direct method of measuring exhaled CO2 with intubated patients, or pts being ventilated with a BVM, SGA, or OPA

Question 19

Can ETCO2 be used with CPAP?

Answer 19

Yes, both sidestream and mainstream can be used, sidestream preferred.

Question 20

What are some reasons for low ETCO2?

Answer 20

• Anxiety
• Bronchospasm
• Pulmonary embolus
• Cardiac arrest
• Hypotension
• Decreased cardiac output
• Cold

Question 21

What are some reasons for high ETCO2 measurements?

Answer 21

• Overdose
• Sedation
• Intoxication
• Postictal states
• Head trauma
• Stroke
• Tiring CHF
• Fever
• Sepsis
• SOB

Question 22

What does ETCO2 measure when Cardiac output (blood flow) is normal?

Answer 22

Ventilation

Question 23

What does ETCO2 measure when Cardiac Output (blood flow) is decreased?

Answer 23

Cardiac output
(This is why ETCO2 is a good indicator of compression quality in CPR)

Question 24

During CPR, what ETCO2 is considered too low?

Answer 24

Under 10-15 mmHg.

Question 25

Why does ETCO2 spike in ROSC?

Answer 25

Large amounts of acidic blood are suddenly returned to the lungs and high amounts of CO2 diffuses into the alveoli. This flood of CO2 causes a sharp rise in ETCO2 levels, much higher then normal.