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KLowe Anesthesia Physiology 1: Respiratory > Lecture 8: Pulmonary Intraop Monitoring/Difficult Airway Algorithm > Flashcards

Lecture 8: Pulmonary Intraop Monitoring/Difficult Airway Algorithm Flashcards

1
Q

940 nm

A

Infrared light, oxyhemoglobin absorbs more of this light, corresponds to 100% saturation

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2
Q

660 nm

A

Red light, deoxyhemoglobin absorbs more of this light, corresponds to 50% saturation

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3
Q

Very rough rule—PaO2 40, 50, 60 for sat ___, ___, ___

A

70, 80, 90

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4
Q

Sat 100, PaO2 ___

A

100

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5
Q

Sat 95, PaO2 ___

A

75

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6
Q

Sat 90, PaO2 ___

A

60

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7
Q

Sat 75, PaO2 ___

A

40 (mixed venous blood in pulmonary artery)

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8
Q

Sat 60, PaO2 ___

A

30

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9
Q

Sat 50, PaO2 ___

A

27

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10
Q

Can a standard pulse ox. Be used in MRI?

A

No—may burn patient, dedicated MRI probe needed

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11
Q

Endobronchial intubation will usually go undetected by pulse ox. In…

A

The absence of lung disease or low FiO2

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12
Q

Limitations of pulse ox—hemoglobin variants

A

Carboxyhemoglobin (COHb)

Methemoglobin (MetHb)

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13
Q

Carboxyhemoglobin

A
  • From CO poisoning

- CO is viewed as oxyhemoglobin by pulse ox. And shows a SPO2 of 100% (overestimation of oxygenation)

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14
Q

What is used to distinguish between oxyhemoglobin and carboxyhemoglobin?

A

A co-oximeter

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15
Q

Methemoglobin

A

Fe 2+ (ferrous) in Hb is oxidized to Fe 3+ (ferric) form and cannot transport O2

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16
Q

Methemoglobin—Cyanosis seen when ___ of Hb is in methemoglobin form

A

15%

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17
Q

Methemoglobin is caused by…

A
  • Nitrates
  • Nitrites
  • Sulfonamides
  • Benzocaine (hurricane spray)
  • Nitroglycerine (NTG)
  • Nitroprusside (SNP)
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18
Q

Methemoglobin—does it absorb equally at both wavelengths?

A

Yes—1:1

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19
Q

Methemoglobin—shows a SPO2 of ___ regardless of true oxygen saturation

A

85%

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20
Q

Treatment for methemoglobin

A

Methylene blue or ascorbic acid

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21
Q

What two things do not affect pulse oximetry?

A

Fetal hemoglobin and bilirubin

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22
Q

Severe hypoxemia—poor accuracy at SPO2 < ___

A

30%

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23
Q

Pulse ox won’t function well if Hb < ___

A

3-4 gm/dL

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24
Q

Pulse ox is designed to assume pulsation are ___

A

Arterial—why right heart failure (for pulmonale) or tricuspid regurgitation disturb SPO2, seen in dependent (down) limb

25
Q

What dyes interfere with SPO2?

A

Methylene blue and idocyanine green—will drop SPO2 for 5-10 minutes

26
Q

Malpositioned sensor effect on SPO2

A

Penumbra effect, shows SPO2 of 90-95%

27
Q

Capnography rapidly and reliably indicates ___ but does not reliably detect ___

A

Esophageal intubation, endobronchial intubation

28
Q

What is the gold standard for tracheal intubation?

A

+ ETCO2

29
Q

Capnometer

A

Measures CO2

30
Q

Capnograph

A

Records and displays CO2

31
Q

Not all capnometers display a ___

A

Capnogram

32
Q

All capnographs are in part ___

A

A capnometer

33
Q

CO2 is depicted graphically as a ___

A

Capnogram

34
Q

CO2 is recorded by a ___

A

Capnograph

35
Q

CO2 is measured by a ___

A

Capnometer

36
Q

Normal capnograph components

A 
AB segment
BC segment
CD segment
D point
DE segment
37
Q

AB segment =

A

Beginning exhalation, dead space gas

38
Q

BC segment =

A

Upstroke

Exhalation, mixing of gases (dead space + alveolar gas)

39
Q

CD segment =

A

Alveolar plateau, alveolar rich gas

40
Q

D point =

A

Highest CO2–end tidal CO2 measurement

41
Q

DE segment =

A

Start inspiration

42
Q

Shark fin ETCO2

A

Obstructive pattern—COPD, bronchospasm

43
Q

Curare cleft

A

Early spontaneous breath

44
Q

Normal end-tidal CO2 to arterial CO2 gradient (dCO2) is ___

A

2-5 mm Hg

45
Q

ETCO2/arterial CO2 (dCO2) gradient reflects…

A

Alveolar dead space—alveoli ventilated but not perfused

46
Q

What increases dCO2?

A

Any significant reduction in lung perfusion/increases in alveolar dead space

47
Q

PaCO2 will always be ___ than ETCO2 due to ___

A

Higher, d/t mixing and dilution with the dead space gases

48
Q

Causes of increased dCO2 (7):

A
  • Decreased pulmonary artery pressure
  • Upright posture
  • Pulmonary emboli (PE)—air, fat, thrombus, amniotic fluid
  • COPD—causes no vascular air spaces at alveolar level
  • Mechanical obstruction of pulmonary artery
  • Ventilated gas leaving normal pathway—cuff leak, tracheal disruption, bronchopleural fistula
  • Decreased CO or hypotension
49
Q

Causes of increased ETCO2 (9):

A
  • Malignant hyperthermia
  • Hypoventilation
  • Bicarbonate
  • Laparoscopy (CO2 inflation)
  • Hyperthermia
  • Improved blood flow to lungs after hypotension or resuscitation
  • Tourniquet released
  • Water in capnograph sensor
  • Breathing circuit error—CO2 absorber exhausted, rebreathing, inadequate fresh gas flow, faulty valves in circuit
50
Q

Causes of decreased ETCO2 (9):

A
  • Hyperventilation
  • Airway leak, leak around cuff
  • Decreased blood flow to lungs
  • Pulmonary embolism
  • Decreased CO, arrhythmia
  • Incipient pulmonary edema
  • Hypothermia
  • Inadequate sample volume
  • Sample catheter misplaced
51
Q

What is malignant hyperthermia?

A

Rare, inherited skeletal muscle syndrome

52
Q

MH presents as a ___

A

Hypermetabolic reaction

53
Q

MH is triggered by…

A

Exposure to volatile anesthetic gases or depolarizing muscle relaxant (succinylcholine)

54
Q

Incidence of MH

A

1/5,000-1/100,000

55
Q

Early signs of MH (11):

A
  • Abrupt increase in ETCO2
  • Cardiac arrhythmias
  • Generalized muscle rigidity
  • Hypoxia
  • Profuse sweating
  • Trismus/masseter muscle rigidity (MMR)
  • Metabolic-respiratory acidosis
  • Mottling of the skin
  • Tachycardia
  • Tachypnea in spontaneously breathing patients
  • Unstable arterial pressure
56
Q

Late signs of MH (11):

A
  • Acute renal failure
  • Circulatory failure
  • Dark colored urine due to myoglobinuria
  • Disseminated intravascular coagulation
  • Elevated blood creative phosphokinase (CPK) levels
  • Elevated blood myoglobin levels
  • Hyperkalemia
  • Hyperthermia (> 38.8 degrees Celsius)***
  • Hypotension
  • Rhabdomyolysis
  • Severe cardiac arrhythmias and cardiac arrest
57
Q

Treatment of MH

A

Dantrolene

58
Q

Initial dose of dantrolene

A

2.5 mg/kg

59
Q

Alternative to dantrolene

A

Ryanodex 2.5 mg/kg—expensive

KLowe Anesthesia Physiology 1: Respiratory (13 decks)

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