Capnography Exam I Flashcards
(47 cards)
1
Q
What capnography measurement was mandated by the ASA in July of 1989?
A
- CO2 was identified in expired gas to confirm placement of ETT or LMA.
- Ventilation/CO2 had to be assessed in every general anesthetic case.
2
Q
What capnography measurement was mandated by the ASA in July of 2011?
A
- CO2 must also be monitored for any patient undergoing moderate to deep sedation.
3
Q
What is capnography?
A
The measurement and quantification of inhaled or exhaled CO2 concentrations.
4
Q
How is capnometry measured?
A
by a capnometer
5
Q
What is capnography?
A
- A method of CO2 measurement and a graphic display over time.
- A detection of CO2 breath by breath.
6
Q
What is the best method to confirm endotracheal intubation?
A
capnography
7
Q
What is a side-stream measurement of capnography?
A
- Aspirates the gas sample and analyzes it away from the airway at a rate of 50-200mL/min.
- Has a transport time delay and rise time delay
8
Q
What is a main-stream measurement of capnography?
A
- Analyzes gas sample directly from the circuit.
- No time delay
- Rise time is faster
9
Q
Which capnography measurement is most common?
A
Side stream
10
Q
What are the effects of hypercarbia seen from capnography? (5)
A
- Respiratory acidosis
- Increases cerebral blood flow (CBF)
- Increases ICP in susceptible patients
- Increases pulmonary vascular resistance
- Potassium shifts from intracellular to intravascular (increases in serum K)
11
Q
What are the effects of hypocarbia seen from capnography? (5)
A
- Respiratory alkalosis
- Decreases cerebral blood flow (CBF)
- Decreases pulmonary vascular resistance
- Potassium shifts from intravascular to intracellular (decrease in serum K)
- Blunts the normal urge to breathe
12
Q
What factors decrease ETCO2? (7)
A
- hypothermia
- PE (pulmonary hypoperfusion)
- cardiac arrest
- hemorrhage
- hypotension
- hyperventilation
- Equipment malfunction
13
Q
What equipment malfunctions decrease ETCO2? (5)
A
- ventilator disconnect
- esophageal intubation
- airway obstruction
- poor sampling
- ETT cuff leak
14
Q
What factors increase ETCO2? (10)
A
- increased metabolic rate
- fever
- sepsis
- seizures
- thyrotoxicosis
- increased cardiac output
- bicarbonate administration
- hypoventilation
- COPD (due to air trapping, alveolar CO2 will be much higher than normal, what little gas that is expired will have a higher ETCO2 content)
- equipment malfunction
15
Q
What equipment malfunctions increase ETCO2? (4)
A
- rebreathing
- exhausted CO2 absorber
- leak in ventilator circuit
- faulty inspiratory/expiratory valves
16
Q
When you have an equipment malfunction, will you hear the alarm first or see the waveform change first?
A
See the waveform change first
17
Q
What is the normal difference in mmHg between PaCO2 and ETCO2?
A
5mmHg
18
Q
What is normal PaCO2?
A
40mmHg
19
Q
What is normal ETCO2?
A
35mmHg
20
Q
What problems can increase the difference between PaCO2 and ETCO2? (3)
A
- V/Q mismatching such as PE and endobronchial intubation.
- Breathing patterns that don’t deliver alveolar gas to the sampling line such as COPD and bronchospasms.
- capnograph problems such as sampling leaks and slow sampling response time.
21
Q
CO2 measurement most commonly relies on ___ light absorption techniques.
A
IR (infrared) **light absorption
22
Q
The ___ the CO2 in the sample, the ___ infrared light reaches the detector.
A
- Greater
- less
23
Q
Describe the color change with a CO2 chemical indicator
A
- purple = no CO2 (you aren’t in the trachea)
- Yellow = CO2 (you are in the trachea)
24
Q
What is the pH paper called inside the CO2 chemical indicator?
A
Litmus paper
25
What are the monitor requirements for measuring capnography? (4)
* CO2 reading of + or - 12% of actual value.
* Manufacturers must disclose interference caused by ethanol, acetone, and halogenated volatiles.
* Must have a high CO2 alarm for inhaled and exhaled CO2
* Must have an alarm for low exhaled CO2.
26
Label the phases of a normal capnograph
27
What is phase 1 of capnography?
* Inspiration ends
* Lungs recoil
* Gas in the circuit and anatomic dead space exits.
* Respiratory baseline
* ETCO2 should be 0mmHg
28
What is phase 2 of capnography?
* CO2 rich alveolar gas
* normally steep
* Expiratory upstroke
29
What is the alpha angle of capnography?
* Emptying of the alveoli and transition to dead space
* normally 100-110 degree angle
30
What is phase 3 of capnography?
* Uneven emptying of last alveoli
* slope should rise gently
* There will be a greater slope with airflow obstruction. EX: COPD, bronchospasm, ETT kinking
31
What is the beta angle of capnograpgy?
* Begins the inspiratory phase
* 90 degree angle
* angle increases with inspiratory valve malfunction, rebreathing, or low tidal volume with rapid RR.
32
What is phase 0 of capnography?
* inspiration
* CO2 falls abruptly to 0
* Inspiratory downstroke
33
What are the expiratory phases of the capnograph?
Phases I, II, and III
34
What is the inspiratory phase of the capnograph?
Phase 0
35
What phase on the capnograph will an ETCO2 be measured?
* Beta angle
* The end point of phase 3
36
What should your ETCO2 be everytime you inhale?
0mmHg (back to baseline)
37
Describe the capnograph
* Normal capnograph
* Mechanical ventilation
38
Describe the capnograph
* Inadequate seal around ETT (cuff leak, not properly seated LMA, crack in sampling tubing, forgot to inflate cuff)
* After first inspiration you have a shorter plateau phase and a wonky inspiratory downstroke.
* The machine doesn't see the full ETCO2 because of the leak.
39
Describe the capnograph
* Hypoventilation
* Gradually increasing waveforms due to increased ETCO2 (retaining CO2 with hypoventilation)
* You need to increase minute ventilation either through Vt or RR
40
Describe the capnograph
* Hyperventilation
* Gradually decreasing waveforms due to decreased ETCO2 (Expiring too much CO2 with hyperventilation)
* You need to decrease minute ventilation by either decreasing Vt or RR.
41
Describe the capnograph
* Esophageal intubation
* Rapidly decreasing ETCO2. (There is no ETCO2 in the esophagus, you are just picking up some CO2 from the back of the throat initially)
* Pull the tube and reintubate
* Could **very rarely** be a severe laryngospasm if you really are in the trachea. Give some gas and a bronchodilator and wait for the bronchospasm to subside.
42
Describe the capnograph
* Early loss of paralysis
* Presence of a curare cleft. The cleft is a little tiny inspiration due to the wearing off of the paralytic.
* May need to give a top off dose of paralytic/sedation if you are still mid case.
43
Describe the capnograph
* Patient overbreathing the vent (breath stacking)
* There is a spontaneous breath between the mechanical breath.
* Give more sedation/paralytic depending on where you are in the case.
* Could also change your vent settings.
44
Describe the capnograph
* airway obstruction
* Obstruction to ETCO2 measurement. You are not able to exhale correctly
* EX: Bronchospasm, too much PEEP, kinked tubing, COPD, mucous plugging, Hx of smoking.
* This pattern will be normal for a COPD patient due to physiology.
* Inspiratory downstroke will look normal, expiratory upstroke will look abnormal.
*** Also called a sharkfin waveform**
45
Describe the capnograph
* Rebreathing
* bad soda lime (soda lime is dried up and can no longer absorb CO2)
* Capnograph does not return to baseline at 0mmHg.
* Change the soda lime canister.
46
Describe the capnograph
* Cardiac oscillations (interference from the movement of the heart)
* Often seen in pediatric patients because the heart is so close to the trachea
* Can also be seen in really skinny cachectic patients.
* No defined plateau
47
Describe the capnograph
* ROSC achieved
* During compressions your ETCO2 will be very low until ROSC is achieved. The waveform will be normal, during compressions, the CO2 value will just be very low.
