Capnography

Question 1

Describe and define the components of waveform capnography

Answer 1

Phase I - INSPIRATORY BASELINE: inspired gas very low CO2

Phase II - EXPIRATORY ASCENT: transition between anatomic dead space gas and alveolar gas (from alveoli and respiratory alveoli) transition

Phase III - ALVEOLAR PLATEAU: Last of the alveolar gas is sampled = PETCO2

alpha angle (between II and III) -

Phase IV - SMALL AIRWAY CLOSURE: Pronounced in patients with reduced chest wall compliance (pregnancy and obesity)

Phase 0 - INSPIRATORY DESCENT - beginning of inspiration

http://www.emdocs.net/interpreting-waveform-capnography-pearls-and-pitfalls/

Question 2

What is the mnemonic used for post-intubation deterioration and hypoxia

Answer 2

DOPES

Displacement of the ETT

Obstruction of the airway/ETT

Pneumothorax

Equipment Failure

Stacking (AutoPEEP)

Question 3

What are the causes of capnograph flat line

Answer 3

1. Displacement/disconnection of ETT
2. Obstruction of ETT
3. Pneumothorax
4. Equipment failure
5. Stacking (autoPEEP) - end stage

Capnography not connected
Cardiorespiratory Arrest
Apnoea brain bead test
Obstruction of capnography
Esophageal intubation

Question 4

How is autoPEEP / breath stacking diagnosed on capnography and what are the causes

Answer 4

Progressive elevation of the inspiratory baseline and the alveolar plateau

1. Insufficient expiratory time
2. Faulty expiratory valve

Question 5

What are the causes of increased CO2 production

Answer 5

1. Fever (Sepsis/ SIRS/ Iatrogenic overwarming)
2. Thyroid Storm
3. Malignant Hyperthermia
4. NaHCO3
5. Laparoscopic surgery
6. Tourniquet release
7. Overfeeding syndrome

Question 6

What are the causes of decreased CO2 removal

Answer 6

1. Inadequate Ve IPPV: RR/Vt inadequate
2. Inadequate Ve Spont: Drug induced
   - opioids, benzo, induction agents, volatiles

Question 7

What are the causes of CO2 rebreathing

Answer 7

1. Insufficient expiratory time
2. Inadequate FGF
3. Faulty expiratory valve
4. Exhausted soda lime