Exam 1 - Capnography Flashcards by Jennifer Valenciano

What are some effects of Hypercarbia? Select 3

A. K+ shifts from intracellular to intravascular
B. increases cerebral blood flow
C. increases PVR
D. decreases ICP
E. decreases PVR

A. Potassium shifts from intracellular to intravascular
B. Increases cerebral blood flow (CBF) which… Increases ICP in susceptible patients
C. Increases pulmonary vascular resistance (b/c of vasoconstriction)
and also, Respiratory acidosis can develop over time

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Some effects of Hypocarbia include: select 3
A. decreased ICP
B. increased PVR
C. K+ shifts from intracellular to intravascular
D. blunts normal drive to breathe
E. vasodilation

A. Decreases CBF, which decreases ICP
D. Blunts normal urge to breathe
E. Decreases pulmonary vascular resistance, b/c of vasodilation

Also:
Potassium shifts into the intracellular space (serum K decreases)
and could also cause Respiratory alkalosis

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Capnography provides information primarily on ventilation but can give info on:
A. pulm blood flow
B. integrity of breathing circuit
C. estimation of adequacy of CO
D. all of the above
E. only A and B

D. all of the above
* Integrity of breathing circuit
* Estimates the adequacy of cardiac output
* Pulmonary blood flow

and:
* Aerobic metabolism
* Placement of ETT/LMA (presence of ETCO2)

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The Bohr equation calculates:
A. alveolar dead space
B. physiologic dead spce
C. anatomic dead space
D. airway dead space

B. Physiologic dead space (airway ds + alveolar ds)

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What makes up anatomical dead space? select 2.
A. respiratory zone
B. conducting zone
C. nose, trachea, bronchi
D. alveoli not partaking in gas exchange

B. conducting zones of the airway
C. nose, trachea, bronchi

normal ADS = 150 mL

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The portion of physiologic dead space that does not take part in gas exchange but is within the alveolar space is called:
A. airway DS
B. anatomic DS
C. alveolar DS
D. physiologic DS

C. alveolar dead space

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Some conditions that increase alveolar dead space (V/Q mismatching) include: select 2.
A. underinflation of alveoli
B. pulmonary hypertension
C. hypovolemia
D. pulmonary embolus

C. Hypovolemia
D. Pulmonary embolus
and:
* Pulmonary hypotension
* Ventilation of nonvascular airspace
* Obstruction of precapillary pulmonary vessels
* Obstruction of the pulmonary circulation by external forces
* Overdistension of the alveoli

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What is the best method to confirm endotracheal intubation?
A. breath sounds
B. capnometry
C. capnography
D. CXR

C. capnography

detection of CO2 breath by breath

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Time capnography is a pressure vs time plot for ETCO2 waveform. What is the difference between high-speed vs slow-speed?
A. high-speed can show info about each breath while slow-speed shows more of a trend
B. slow-speed shows info about each breath while high-speed shows more of a trend
C. there is no difference between the two

A.
* High-speed – user can interpret information about each breath
* Slow-speed – appreciation of the expired and inspired trend

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What is the most common gas sampling system?
A. mainstream
B. side-stream
C. flow-over
D. blow-by

B. Side-stream gas analyzer (downside: there’s a transport and rise time delay!)

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What phase on a capnograph will an ETCO2 be measured at?

at end-point of phase 3.

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What can increase ETCO2? select 3.
A. seizures
B. hypothermia
C. cardiac arrest
D. MH
E. thyrotoxicosis
F. pulmonary embolism

A. sz
D. MH
E. thyrotoxicosis

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What can cause decreased ETCO2? select 3.
A. sepsis
B. fever
C. hyperventilation
D. hypotension
E. leak around ET cuff
F. rebreathing

C. hyperventilation
D. hypotension
E. leak around ET cuff

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Difference between PaCO2 and ETCO2 is approx ____ mmHg.

5 mmHg

Ex: ETCO2 of 35 mm Hg = PaCO2 of approx. 40 mm Hg

so normal A-a difference is 5 mmHg

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What are some V/Q mismatching problems that would increase the difference (aka widen the gap) between PaCO2 and ETCO2? Select 3.
A. MH
B. seizures
C. endobronchial intubation
D. aging
E. pulmonary embolism
F. hyperventilation

C. endobronchial intubation
D. aging
E. PE

also, breathing patterns that fail to deliver alveolar gas at the sampling site (like COPD, neonates/infants, bronchospasm), increases the difference between PACO2 and true ETCO2 (alveolar gas)!

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Fill in the blank:

CO2 measurement most commonly relies on infrared light absorption techniques. The __ the CO2 in the sample, the less IR light that reaches the detector.

A. greater
B. less
C. unchanged

A. The greater the CO2 in the sample, the less IR light that reaches the detector

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Describe the color change with a CO2 chemical indicator: select 2.
A. purple - CO2 present
B. yellow - CO2 present
C. purple - no CO2
D. yellow - no CO2

B. Yellow – CO2
C. Purple – No CO2

Sensitive to even low levels of CO2
so ETT placement still needs verification by alternative means

ETCO2 monitor must have an alarm for:
A. high exhaled CO2
B. high inhaled CO2
C. low exhaled CO2
D. low inhaled CO2
E. all of the above
F. all but D

F. all but D
-high inhaled CO2 alarm
-high exhaled CO2 alarm
-low-exhaled CO2 alarm

What are differential diagnoses of loss of exhaled CO2? select 3.
A. bronchospasm
B. apnea
C. endobronchial intubation
D. coughing
E. COPD
F. accidental extubation

A. bronchospasm
B. apnea
F. accidental extubation

also: esophageal intubation, cardiac arrest, or disconnection/failure of sampling line

What are the inspiratory and expiratory segments of a normal capnograph?

Inspiratory – Phase 0
Expiratory – Phases I, II, and III

Describe Phase I of a normal capnograph: select 2
A. alveolar plateau
B. no CO2
C. first expiratory upstroke
D. exhalation of anatomic DS

B. Essentially no CO2
D. Exhalation of anatomic dead space and the apparatus dead space (ETT, LMA)

phase 1 = baseline!

Describe Phase II of a normal capnograph.

Expiratory upstroke begins (CO2-rich alveolar gas)
Sampling of alveolar gases
Normally steep uprise

Describe Phase III of a normal capnograph.

Alveolar Plateau phase
Normally representative of CO2 in alveolus
Can be representative of ventilation heterogeneity, slightly increasing slope

Describe Phase 0 of a normal capnograph.

Sometimes called phase IV
Inspiration of fresh gas, remaining CO2 washed out
Downstroke returns to baseline

Describe the Occasional Phase IV (Phase IV’) of a capnograph: select 2
A. sharp upstroke in PCO2 at the very end of phase II
B. inspiration of fresh gas
C. from closure of lung units with lower PCO2
D. remaining CO2 being washed out
E. seen in pregnant and obese patients

C. Upstroke probably results from the closure of lung units with lower PCO2 … Allows for regions w/ higher CO2 to contribute to more of the exhaled gas sample
E. Seen in pregnant and obese pts (decreased FRC and lung capacity)
* sharp upstroke in PCO2 at the very end of phase III
* Decreased FRC and lung capacity

The alpha angle of the capnograph increases with:
A. inspiratory airflow obstruction
B. rebreathing
C. expiratory airflow obstruction
D. low Vt with rapid RR

C. Angle increases with an expiratory airflow obstruction such as COPD, bronchospasm, or kinked ETT
alpha angle defined as:
* Separates phase II and phase III
* 100 – 110 degrees

The beta angle of the capnograph increases with:
A. rebreathing
B. malfunctioning inspiratory unidirectional valves
C. low Vt with rapid RR like with neonates
D. All of the above
E. All but B

D. all of the above- angle increases with malfunctioning inspiratory unidirectional valves, rebreathing, and low tidal volume with rapid respiratory rate (like w/ neonates)

Beta angle defined as:
- Separates phase III and phase 0; and 90 degrees