Flipped Classroom - Capnography Flashcards
What is capnography?
The continuous monitoring of end tidal carbon dioxide (EtCO2)
Elisha et al., 2022, p. 316
What is the mean PaCO2 range for adults?
35-45 mmHg
What is the mean PaCO2 range for newborns?
30-35 mmHg
How different is EtCO2 compared to PaCO2?
EtCO2 is proximately 2-5 tor lower than PaCO2
Elisha et al., 2022, Table 52.4
What is CO2 a byproduct of?
Aerobic metabolism
What do central chemoreceptors detect?
H+ resulting from CO2 combining with water
What condition results from the failure to expel CO2?
Respiratory acidosis
Butterworth et al., 2022, pp. 523, 531
What type of analysis is used in capnography?
Infrared analysis
What is the characteristic of non-diverting capnography?
Sensor in adapter between mask and circuit, minimal delays, few disposable items, no scavenging
What gases does non-diverting capnography measure?
CO2 and NO2
What is a disadvantage of non-diverting capnography?
Increased dead space, interference from secretion and condensation, added weight
What is a characteristic of diverting capnography?
Removes gas from the circuit and transports it to monitor, lightweight, minimal dead space
What is a disadvantage of diverting capnography?
Still vulnerable to secretions and condensation
What are reasons to use capnography?
Monitoring patient ventilation (EtCO2 is more sensitive to detecting hypoventilation)
Confirm ETT placement
Detecting return of ROSC
Detect pt’s adverse outcome.
What are the causes of increased EtCO2 in anesthesia?
Increased CO2 delivery/production, hypoventilation, and equipment problems.
What are the causes of decreased EtCO2 in anesthesia?
Decreased CO2 delivery/production, hyperventilation, and equipment problems.
What are the three phases of capnography?
Phase I - Dead Space, Phase II - Mixture of dead space and alveolar gas, Phase III - Alveolar gas plateau.
In which conditions is the obstructive pulmonary disease capnography waveform often seen in?
Conditions involving inability to move air, such as COPD, asthma, and bronchospasms.
What does the capnograph of a patient with severe chronic obstructive pulmonary disease show?
No plateau is reached before the next inspiration, and the gradient between end-tidal CO2 and arterial CO2 is increased.
C: Depression during phase III indicates spontaneous respiratory effort.
How can EtCO2 be used in monitoring?
EtCO2 can be used to monitor depth of sedation, but it could be detrimental depending on the procedure.
What does depression during phase III of capnography indicate?
It indicates spontaneous respiratory effort.
What is used to determine CO2 absorbent exhaustion?
Color change is used to determine whether a cannister becomes exhausted. However it is not realiable and not react immediately
However, color change is not completely reliable and does not react immediately.
What are early clinical signs of CO2 absorbent exhaustion?
Elevated EtCO2 monitor readings, respiratory acidosis, hyperventilation, activation of sympathetic nervous system, and increased hemorrhage.
What should you not do mid-case with dual canisters?
Do not change dual canister mid-case.
What should you do if CO2 absorbent exhaustion is suspected?
Increase flow rate and wait until after.
What are the advantages of capnography?
Easily implemented through technology, non-invasive, accurate, and provides improved monitoring of ventilation when combined with pulse oximetry.
Select the true statement regarding capnography:
A. Capnography is inaccurate and not a reliable source of CO2 monitoring
B. Capnography is not necessary when a pulse oximetry probe is in place
C. Capnography is accurate and only 2-5 tor lower than PaCO2
D. Capnography is moderately accurate and regular arterial blood gases must be compared to ensure EtCO2 accuracy
Answer: C, Capnography is a highly accurate method of measuring a patient’s carbon dioxide levels. EtCO2 is only lower than PaCO2 by 2-5 tor which allows anesthesia providers to use capnography to monitor their patients’ ventilation status (Elisha et al., 2022).
An anesthesia provider hears a pressure alarm, and notes increased inhaled CO2 levels with an abnormally long downstroke on the capnogram. What should the provider first check?
A. Check the inspiratory valve on the circle circuit
B. Check the expiratory valve on the circle circuit
C. Trouble shoot the scrubber on the circle circuit
D. Check the Y-piece for disconnection
Answer: A, When a unidirectional valve in a circle system is compromised, exhaled CO2 can build up causing increased inhalation of CO2. With the failure of an expiratory valve, the capnography demonstrates an elevated CO2 level, but the waveform remains unchanged. Failure of an inspiratory valve can lead to not only increased CO2 levels, but also an increased downstroke on the capnograph (Elisha et al, 2022).
All can increase EtCO2 except:
A. Incompetent expiratory valve
B. Incompetent inspiratory valve
C. Increasing fresh gas flow
D. Malignant hyperthermia
Answer: C, increasing fresh gas flow will decrease CO2 levels. Incompetent expiratory and inspiratory valves can result in rebreathing CO2. Malignant hyperthermia results in the increased production of CO2 which can result in elevated EtCO2 levels (Elisha et al., 2022).
You note an increase in CO2 and upon further inspection, the cannister color has changed. What is the best course of action?
A. Increase fresh gas flow rate and wait until after the procedure to change CO2 absorber cannister
B. Change CO2 absorber cannister immediately
C. Monitor for arrhythmias and change absorber cannister after the case
D. Disconnect patient circuit and use the Ambubag to ventilate the patient
Answer: A, Carbon dioxide absorbers are critical components of an anesthesia machine. However, it is dangerous to change an absorber mid case. Instead, the anesthesia provider should increase fresh gas flows to limit the amount of CO2 inspired and finish the case. After, the cannister can be safely changed. (Elisha et al., 2022).
While administering general anesthesia, the provider notes a waveform depression during phase III on the EtCO2 monitor. What should the provider’s next action be?
A. The patient is experiencing a bronchospasm. Deepen sedation and administer albuterol.
B. There is a blockage in the breathing circuit. Switch to ambubag and manually ventilate.
C. The circuit is disconnected. Confirm y-piece is in place.
D. The patient is attempting spontaneous breathing. Deepen sedation.
Answer: D, When there is a slight depression during phase III of a capnogram, it could indicate that the patient is trying to breath spontaneously. This could indicate that the provider needs to increase sedation (Butterworth et al., 2022)
What is not a feature of the diverting (side stream) EtCO2 monitor.
A. It measures concentrations of CO2 and anesthetic gases
B. It scavenges gas and transports it to the monitor
C. The sensor directly rests in an adapter between the circuit and mouth piece
D. It creates minimal dead space
Answer: C, In diverting (side stream) EtCO2 monitors, the exhaled gas from the patient is scavenged and transported to the monitor where the gas is analyzed. This reduces weight to the circuit, reduces the amount of dead space, and allows the monitor to analyze the concentration of other anesthetic gases, not just CO2 (Elisha et al., 2022).
