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Principles of Anesthesia I - Summer 24 > Capnography - Exam 1 (Ericksen) > Flashcards

Capnography - Exam 1 (Ericksen) Flashcards

1
Q

What 3 things does capnography give us information about?

A
  • Ventilation
  • metabolism: how effectively CO2 is being produced @ cellular level
  • CV: how effectively the CO2 is moving in the vascular system & out of pulmonary system
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2
Q

General Effects of Hypercarbia

A
  1. Respiratory acidosis
  2. increases CBF - increased ICP (vasodilation)
    – chemoreceptors in brainstem to help pt blow off CO2
  3. increases pulmonary vascular resistance (vasoconstricts in the lungs) - increases PA pressures
    – NO PULM HTN
  4. potassium shift from intracellular - intravascular (hyperkalemia)
  5. can be used to get pts to start breathing again
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3
Q

General Effects of Hypocarbia

A
  1. respiratory alkalosis
  2. decreases CBF (low limit of 28mmHg) - vasoconstriction
  3. decrease pulm. vascular resistance (vasodilation in lungs)
  4. potassium shifts into the intracellular space
  5. blunts normal urge to breathe (manual ventialtion or over-breathing)
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4
Q

What other information can capnography tell us?

A
  1. pulmonary blood flow
  2. aerobic metabolism
  3. placement of ETT/LMA
  4. integrity of breathing circuit (leaks, disconnects, sample line leak)
  5. estimates adequacy of CO in CPR
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5
Q

BOHR equation - what is it calculating?

A
  1. physiologic DS (anatomic + alveolar)
  2. Vt
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6
Q

Anatomic DS:

A
  • conducting zones of airway (nose, trachea, bronchi)
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7
Q

Physiological DS:

A

airway DS + alveolar DS

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8
Q

7 conditions that increase alveolar DS (V/Q mismatching)

A
  1. hypovolemia (poor perfusion)
  2. pulmonary HoTN (poor perfusion)
  3. PE - obstructed flow
  4. ventilation of nonvascular airspace (not getting blood)
  5. obstruction of pre-capillary pulm vessels
  6. obstruction of pulmonary circulation by external forces
  7. overdistention of alveoli (PEEP)
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9
Q

What is capnometry?

A

measurement & quantification of inhaled or exhaled CO2 concentrations
* measured w/ capnometer

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10
Q

What is capnography?

A
  • method of CO2 measurement & a graphic display of time
  • detects CO2 breath-breath
  • best method to confirm ETT intubation
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11
Q

What is time capnography?

A
  • pressure vs time plot
  • most common representation of capnometry
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12
Q

time capnography

High speed

A
  • can interpret info breath-breath
  • not looking @ trends
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13
Q

time capnography

slow speed

A
  • looks @ trends
  • expired & inspired trend
  • waveform looks fast
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14
Q

Side-stream capnography

A
  • aspirates gas sample and analyzes away
  • rate of 50-200mL/min
  • most common
  • transport time delay/rise time is slower
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15
Q

Mainstream capnography

A
  • detected in airway @ circuit
  • analyzes gas sample directly in breathing circuit
  • no time delay; rise time faster
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16
Q

Where is ETCO2 measured @ in the waveform?

A
  • end of phase III
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17
Q

3 Broad causes of Increased PetCO2:

A
  1. increased CO2 production & delivery to lungs
  2. decreased alveolar ventilation
  3. equipment malfunction
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18
Q

increased PetCO2

causes of increased CO2 production & delivery to lungs (8)

A
  1. increased metabolic rate
  2. fever
  3. sepsis
  4. seizures
  5. MH
  6. thyrotoxicosis
  7. increased CO - CPR, thyroid problems
  8. bicarb admin - converted to CO2
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19
Q

increased PetCO2

Causes of decreased alveolar ventilation (6)

A
  1. hypoventilation
  2. resp. center depression (drugs)
  3. partial muscle paralysis
  4. NM disease
  5. high spinal anesthesia - knock out resp. drive
  6. COPD
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20
Q

increased PetCO2

Equipment malfunction causes (4)

A
  1. rebreathing - normalish
  2. exhausted CO2 absorber
  3. leak in vent circuit (old vents)
  4. faulty inspiratory/expiratory valve (traps CO2)
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21
Q

Broad causes of decreased PetCO2

A
  1. decreased CO2 production & delivery to the lungs
  2. increased alveolar ventilation
  3. equipment malfunction
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22
Q

decreased PetCO2

Causes of decreased CO2 production and delivery to lungs (6)

A
  1. Hypothermia
  2. pulmonary hypoperfusion (less delivered)
  3. cardiac arrest
  4. PE
  5. hemorrhage
  6. hypotension
23
Q

decreased PetCO2

Increased Alveolar Ventilation

A
  • Hyperventilation - if we are breathing faster for pt or if the pt is breathing faster
24
Q

decreased PetCO2

Equipment Malfunctions (5)

A
  1. ventilator disconnect
  2. esophageal intubation
  3. complete airway obstruction
    – laryngospasm, tube plugged
  4. poor sampling - breathing too rapid
  5. leak around endotracheal tube cuff (mixing RA)
25
Q

What is the normal difference b/w PaCO2 & ETCO2 (PACO2)?

A

5mmHg
* Ex: ETCO2 35mmHg = PaCO2 40mmHg

26
Q

Problems that increase the difference b/w PaCO2 & ETCO2 (2)

A
  1. V/Q mismatch (PE, endobronchial intubation)
  2. breathing patterns that fail to deliver alveolar gas to the sampling site
    – ex: infants/neonates, COPD (bronchi collapse before alveoli empty), bronchospasm
27
Q

Problems w/ the capnograph increase the difference b/w ________ & ________.

A

true ETCO2 & measured ETCO2
* ex: sampling cath leaks, calibration error, side-streaming slow response

28
Q

Clinical measurement techniques (ETCO2)

A
  1. IR light absorption - greater CO2 in sample = less IR hitting detector
  2. chemical indicator (yellow mellow)
    – could still verify esophageal intubation
29
Q

What are the capnograph monitor requirements?

A
  1. CO2 reading w/i +/- 12% of actual value
  2. Manufacturers disclose interference from ethanol, acetone, halogenated volatiles
  3. must have a high CO2 alarm for inhaled & exhaled CO2 (rebreathing)
  4. must have an alarm for low exhaled CO2
30
Q

What can we interpret when looking at a time capnogram?

A
  1. CO2 values
  2. approximate blood CO2 levels
  3. pulmonary blood flow
  4. alveolar ventilation
31
Q

Differential diagnoses of loss of exhaled CO2 – things we want to rule out/possible causes

A
  1. esophageal intubation
  2. accidental extubation
  3. disconnection or failure of sampling/device (leak, failure of sampling pump)
  4. apnea (drugs), bronchospasm (loss of exhaled CO2), cardiac arrest
32
Q

Normal Capnograph

Phase I

A
  • baseline should be 0mmHg - unless rebreathing
  • represents exhalation of anatomic DS & apparatus
  • essentially no CO2
33
Q

Normal Capnograph

Phase II

A
  • expiratory upstroke
  • CO2 rich alveolar gas being expired
  • sampling of alveolar gases
  • normally steep
34
Q

Normal capnograph

Phase III:

A
  • plateau phase
  • representative of CO2 in the alveolus
  • ventilation heterogeneity - alveoli closing @ diff times
  • gives the slight increasing slope
35
Q

Normal capnograph

Phase 0

A

sometimes called phase IV
* inspiration of fresh gas - remaining CO2 washed out
* downstroke returns to baseline

36
Q

Normal Capnograph

Occasional Phase IV

A

different from phase 0
* sharp upstroke in PCO2 @ end of phase III
* resulting from closure of lung units w/ lower PCO2
* allows for regions w/ higher CO2 to contribute more to exhaled sample

37
Q

Who is the occasional phase IV seen in?

Why?

A
  • pregnant & obese
  • decreased FRC & lung capacity
  • things are emptying & last little bit goes “pewwww”
  • also called phase IV’
38
Q

What is the alpha angle?

A
  • separates phase II & III
  • 100-110 degrees
39
Q

What causes the alpha angle to increase?

A
  • expiratory airflow obstruction
  • end of the alveoli obstruct & close before emptying
  • give shark fin appearance & the angle widens

COPD, bronchospasm, kinked ETT

40
Q

What is the beta angle?

A
  • separates phase III & 0
  • 90 degrees
41
Q

What causes the beta angle to increase?

A
  • malfunctioning inspiratory unidirectional valves
  • rebreathing of CO2
  • low Vt w/ rapid RR (fast & shallow)
42
Q

Mechanical Ventilation Capnograph

A
43
Q

Spontaneous Ventilation Capnograph

A
  • sometimes see all phases
  • sometimes see bumps/hills
44
Q

Inadequate seal around ETT capnograph

A
  • B angle opens and widens
  • RA is also entering
  • Phase III cut short b/c its going out around the lost seal as well
45
Q

Faulty Inspiratory Valve Capnograph

A
  • inspiratory valve gets stuck - causes rebreathing of CO2
  • expiratory valve can also get stuck
  • phase I now starts @ 5-8mmHg instead of 0mmHg
  • this capnograph also has the little step up @ the end of phase 0!!!!
46
Q

Sample Line Leak Capnograph

A
  • atmospheric air being aspirated into sampling line
  • dilutes ETCO2 & decreases the value
  • has a peak that looks like phase IV’ but it is not
  • this capnograph does not reach 40mmHg for phase III
47
Q

Hyperventilation Capnograph

A
  • decrease in ETCO2
  • @ least 3 capnographs decreasing in size or trend going down
  • Causes: decreased anesthesia/metabolic acidosis
48
Q

Hypoventilation Capnograph

A
  • Increase in ETCO2
  • cause: hypoventilation, fever, narcotics
  • capnograph waves are getting bigger and trend is going up
49
Q

Airway Obstruction Capnograph

A

shark fin
* phase II & III connected
* alpha angle pretty much gone (opened up)

50
Q

Cardiogenic Oscillations Capnograph

A
  • seen in peds - Heart close to trachea & beating against lungs
    – causes emptying @ different times of lung regions
  • see at end of exhalation as flow decreases to 0
  • age this goes away - depends on anatomy as they get bigger (8-10)
51
Q

Rebreathing/Soda Lime Exhaustion Capnograph

A
  • cannot get back to baseline
  • this does not have the step up like faulty inspiratory valve
  • baseline gets higher & higher
  • phase 0 does not change - gets as low as it can
  • inspiratory baseline higher but valve not broken
52
Q

NMBD wearing off capnograph

A
  • Curare cleft
  • little divot at the end of phase III
  • can we flip off the vent & let them breathe or do we need to reparalyze?
53
Q

Overbreathing Capnograph

A
  • getting mechanical breath but taking own spontaneous breath as well
  • weaker vs. stronger
  • can let them breathe - feel bad and give PS by closing APL valve a little
  • titrate narcotics to RR
54
Q

Esophageal Intubation Capnograph

A
  • spontaneous looking waveform that goes away
  • if mechanically ventilated wave that goes away = accidental extubation/kink/self-extubation

Principles of Anesthesia I - Summer 24 (14 decks)

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