capnography

Question 1

Effects of Hypercarbia

Answer 1

Respiratory acidosis
Increases cerebral blood flow (CBF)
Increases pulmonary vascular resistance by causing vasoconstriction
Potassium shifts from intracellular to intravascular

Question 2

Effects of Hypocarbia

Answer 2

Respiratory alkalosis
Decreases CBF
Decreases pulmonary vascular resistance
Potassium shifts to the intracellular space
Blunts normal urge to breathe

Question 3

Bohr equation

Answer 3

calculates physiologic dead space

(VD/VT) = (PACO2 -PECO2) / PACO2

Question 4

Volume of each breath inhaled that does not participate in gas exchange

Answer 4

dead space
anatomic or physiologic

Question 5

airway dead space + alveolar dead space

Answer 5

Physiologic dead space

Question 6

portion of the physiologic dead space that does not take part in gas exchange but is within the alveolar space

Answer 6

alveolar ds

Question 7

Measurement and quantification of inhaled or exhaled CO2 concentrations

Answer 7

Capnometry

Question 8

Conditions that increase alveolar dead space (V/Q mismatching)

Answer 8

-Hypovolemia- poor CO = less bf to ventilating area
-Pulmonary hypotension= not good flow
-Pulmonary embolus= blocking bf
-Ventilation of nonvascular airspace
-Obstruction of precapillary pulmonary vessels
-Obstruction of the pulmonary circulation by external forces
-Overdistension of the alveoli

Question 9

Detection of CO2 breath-by-breath

Answer 9

Capnography
Best method to confirm endotracheal intubation

Question 10

user can interpret information about each breath

Answer 10

High speed time capnography

Question 11

appreciation of the expired and inspired trend

Answer 11

Slow-speed time capnography

Question 12

Aspirates gas sample and analyzes away from airway at a rate of 50 to 200 mL/min

Answer 12

Side-stream

most common but slower

Question 13

Analyzes gas sample directly in the breathing circuit

Answer 13

Main-stream

No time delay; rise time is faster

Question 14

Measured at end-point of Phase III

Answer 14

End-Tidal CO2

Question 15

Causes of increase PETCO2

Answer 15

MH
sz
inc metabolic rate
thyrotocisosis,
inc CO
Bicarb admin

Question 16

Causes of decreased alv ventilation

Answer 16

resp center depression
paralysis
nm dz
high spinal
COPD

Question 17

Causes of dec PETCO2

Answer 17

hypothermia
pulm hypoperf
cardiac arrest
PE
hemm
hypotens

Question 18

Difference between PaCO2 and ETCO2 is approx…

Answer 18

5mmhg

Question 19

V/Q mismatching increases the difference between

Answer 19

PaCO2 and PACO2

Question 20

Breathing patterns that fail to deliver alveolar gas at the sampling site, increase the difference between……

Answer 20

PACO2 and true ETCO2 (alveolar gas)

Ex: neonates and infants; COPD, bronchospasm

Question 21

Problems with the capnograph increase the difference between______

Answer 21

true ETCO2 (alveolar gas) and measured ETCO2 (capnograph)

Ex: sampling catheter leaks, calibration error, slow response time relative to breathing pattern

Question 22

Color change of pH sensitive paper

Answer 22

Purple – No CO2
Yellow – CO2

Sensitive to low levels of CO2

Question 23

Capnography Monitor Requirements

Answer 23

CO2 reading within +/- 12% of actual value

Manufacturers must disclose interference caused by ethanol, acetone, halogenated volatiles

Must have a high CO2 alarm for inhaled and exhaled CO2

Must have an alarm for low exhaled CO2

Question 24

ETCO2 phase 1

Answer 24

respiratory baseline (should be 0)

Exhalation of anatomic dead space and the apparatus
no CO2

1/3 to vt exits

Question 25

ETCO2 phase 2

Answer 25

expiratory upstroke

CO2-rich alveolar gas
Sampling of alveolar gases
Normally steep

Question 26

ETCO2 phase 3

Answer 26

Alveolar plateau

Normally representative of CO2 in the alveolus
Can be representative of ventilation heterogeneity, slight increasing slope

Question 27

ETCO3 phase 0

Answer 27

inspiratory downstroke

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

Question 28

Occasional Phase IV

Answer 28

A sharp upstroke in PCO2at the very end of phaseIII
Upstroke probably results fromthe closure of lung units with lower PCO2
Allows for regions with higher CO2to contribute to more of the exhaled gas sample

Seen in pregnant and obese pts
Decreased FRC and lung capacity

Question 29

Alpha angle

Answer 29

Separates phase II and phase III
100 – 110 degrees
Angle increases with an expiratory airflow obstruction

Question 30

Beta angle

Answer 30

Separates phase III and phase 0
90 degrees
Angle increases with malfunctioning inspiratory unidirectional valves, rebreathing, and low tidal volume with rapid respiratory rate

Question 31

Obstruction COPD, bronchospasm, or kinked ETT causes what to ETCO2

Answer 31

short phase 2
increases alpha angle
Rise in phase 3 but not plateaued
Shark fin

Question 32

Faulty inspiratory valve causes…

Answer 32

Wider beta angle and the inspiratory down stroke is wider
Malfunctioning inspiratory valve = extension of the downslope and if the pt rebreaths because they aren’t down to 0.
Never return to baseline – rebreathe thought the inspiratory limb

Question 33

Sample line leak causes…

Answer 33

Occasional phase 4.
Only getting half the et coming out -> small wave form

Question 34

Hyperventilation causes…..

Answer 34

decrease in ETCO2

Question 35

Hypoventilation causes…..

Answer 35

increase in ETCO2

Question 36

Causes of rebreathing

Answer 36

soda-lime exhaustion
Co2 getting back to inspiratory limb because not scavenged
Incompetent expiratory valve
Flutter valves need flipped

ETCO2 doesnt go back to 0.

Question 37

Curare cleft

Answer 37

muscle relaxants wearing off
spont breath during a mechanically ventilated breathe

Question 38

overbreathing

Answer 38

spont breathe between mechanical breathe

Question 39

Esophageal intubation

Answer 39

decreased ETCO2, poor waveform