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KLowe Anesthesia Physiology 1: Respiratory > Lecture 7: Pulmonary Function Tests > Flashcards

Lecture 7: Pulmonary Function Tests Flashcards

1
Q

High risk PFT results—FEV1

A

< 2L

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2
Q

High risk PFT results—FEV1/FVC

A

< 0.5

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3
Q

High risk PFT results—VC

A

< 15 cc/kg in adult or < 10 cc/kg in child

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4
Q

High risk PFT results—VC

A

< 40 to 50% than predicted

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5
Q

Severe emphysema requires longer ___

A

Expiratory times

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6
Q

Normal I:E

A

1:2

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7
Q

COPD I:E

A

1:3 (longer expiratory time)

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8
Q

CO2 retainers—ETCO2 should be kept near…

A

The patient’s baseline; rapid correction will lead to metabolic alkalosis

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9
Q

Bronchospasm, avoid ___

A

Histamine releasing drugs—Pentothal, morphine, atracurium, mivacurium, neostigmine, antibiotics

Treat bronchospasm with nebulized albuterol

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10
Q

Extubation—If FEV1 is > 50% predicted…

A

Then extubation probably will not be affected

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11
Q

Extubation—If FEV1 is between 25-50% with some hypoxemia and hypercarbia…

A

Prolonged intubation probable

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12
Q

Extubation—If FEV1 is <25% predicted…

A

Only life saving procedures should be done, regional anesthesia if possible, long term ventilatory support, possible inability to wean from ventilator, tracheostomy probably

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13
Q

Extubation criteria—ABG on FiO2 40%, PaO2 and PaCO2 should be…

A

PaO2 > 70 and PaCO2 < 55

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14
Q

Extubation criteria—NIF is…

A

More negative than -20 cm H2O

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15
Q

Extubation criteria—Vital capacity

A

> 15 cc/kg

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16
Q

Intubation criteria—Mechanics

A

RR>35, VC<15 cc/kg in adult or <10 cc/kg in child, NIF more negative than -20 cm H2O

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17
Q

Intubation criteria—PaO2

A

PaO2 < 70 mm Hg on FiO2 of 40%,

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18
Q

Intubation criteria—A-a gradient

A

A-a gradient > 350 mm Hg on 100% FiO2

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19
Q

Intubation criteria—PaCO2

A

> 55 (except in chronic hypercarbia)

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20
Q

Intubation criteria—Vd/Vt

A

Vd/Vt > 0.6 (remember normal dead space is 30%)

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21
Q

Intubation criteria—Clinical

A

Airway burn, chemical burn, epiglottitis, mental status change, rapidly deteriorating pulmonary status, fatigue

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22
Q

ABG must be measured within ___

A

15 minutes, or glycolysis will occur with lactic acid production, decreased pH, and increased PCO2

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23
Q

ABG sample can be stored ___

A

On ice for 1 to 2 hours

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24
Q

Heparin may significantly lower ___

A

PCO2 by dilution, especially in children when small sample is taken

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25
Q

PH

A

7.35-7.45

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26
Q

PCO2

A

35-45 mm Hg

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27
Q

PO2

A

75-105 mm Hg

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28
Q

Bicarbonate

A

20-26 mmoles/L

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29
Q

Base excess

A

-3 to +3 mmoles/L

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30
Q

An increase of PCO2 by 10 mm Hg causes a decrease in pH by ___; likewise, a decrease of PCO2 by 10 mm Hg will increase pH by ___

A

0.08

So an acute increase in CO2 to 60 mm Hg should cause a drop in pH to 7.24

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31
Q

Hypoxemia

A

Decrease PO2 in blood, < 75

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32
Q

Hypoxia

A

A low O2 state

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33
Q

A-a gradient

A

Measure of efficiency of lung

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34
Q

Formula to calculate PaO2

A

(PB-PH2O) * (FiO2) - (PaCO2/0.8)

Example: PaO2 = (760-47) * (0.21) - (40/0.8) = 100

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35
Q

Normal A-a =

A

Approximately (Age/3)

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36
Q

A-a gradient is widened (2 things)….

A

During anesthesia and with intrinsic lung disease—PTX, PE, V/Q mismatch, diffusion problems

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37
Q

A-a gradient is normal with (2 things)…

A

Hypoventilation or low FiO2

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38
Q

Treatment of widened A-a gradient

A
  • Supplemental O2
  • Adjust ventilation
  • Treat atelectasis
  • Add PEEP
  • Treat underlying cause
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39
Q

Base excess is calculated directly using…

A

PaCO2, pH, and bicarbonate values

40
Q

Rule: A decrease in bicarbonate by 10 mmoles decreases the pH by ___; likewise, an increase in bicarbonate by 10 mmoles increases pH by ___

A

0.15

Example: A bicarbonate of 13 would result in a pH of 7.25

41
Q

Respiratory acidosis = ___ pH and ___ PaCO2

A

Low pH and high PaCO2

42
Q

Causes of respiratory acidosis (5)

A
  • Hypoventilation with hypercarbia
  • CNS depression—trauma, drugs
  • Decreased FRC—obesity
  • Upper or lower airway obstruction
  • COPD, asthma, pulmonary fibrosis
43
Q

After 1-2 days of respiratory acidosis, ___ occurs

A

Renal compensation—H+ excreted by kidney and HCO3- reabsorbed into blood to partially correct pH

44
Q

Respiratory alkalosis— ___ pH and ___ PaCO2

A

High pH and low PaCO2

45
Q

Causes of respiratory alkalosis (10)

A
  • Hyperventilation with hypocarbia
  • Hypoxic respiration
  • CNS disease
  • Encephalitis
  • Anxiety
  • Narcotic withdrawal
  • Pregnancy
  • Early septic shock
  • Hypermetabolic states
  • Artificial ventilation
46
Q

Renal compensation of respiratory alkalosis

A

Increased excretion of HCO3- and decreased secretion of H+, which partially corrects pH

47
Q

Metabolic acidosis— ___ pH and ___ HCO3-

A

Low pH and low HCO3-

48
Q

Causes of metabolic acidosis (6)

A
  • Lactic acidosis from hypoperfusion
  • DKA
  • Renal disease with bicarbonate loss (anion gap and K+)
  • HCO3- loss in diarrhea
  • ASA ingestion
  • High protein intake
49
Q

Respiratory/renal compensation for metabolic acidosis

A
  • Central chemoreceptors with hypocarbia, more rapid than renal compensation, partial correction
  • Kidneys may increase H+ excretion
50
Q

Metabolic alkalosis— ___ pH and ___ HCO3-

A

High pH and high HCO3-

51
Q

Causes of metabolic alkalosis (3)

A
  • Bicarbonate infusion
  • Metabolism of lactate or citrate
  • Loss of H+ from vomiting or excessive NGT suctioning
52
Q

Respiratory/renal compensation for metabolic alkalosis

A
  • Limited hypoventilation due to eventual hypoxic drive, partial correction
  • Kidneys may increase bicarbonate excretion in urine
53
Q

Pulmonary volumes (4)

A
  • Tidal volume
  • Inspiratory reserve volume
  • Expiratory reserve volume
  • Residual volume
54
Q

Tidal volume

A

Amount of inspired air with a normal breath; amounts to about 500 ml in the avg adult male

55
Q

Inspiratory reserve volume

A

Extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force; usually equals 3000 ml

56
Q

Expiratory reserve volume

A

Maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration; about 1100 ml

57
Q

Residual volume

A

Volume of air remaining in the lungs after the most forceful expiration; about 1200 ml

58
Q

Pulmonary capacities (4)

A
  • Inspiratory capacity
  • Functional residual capacity
  • Vital capacity
  • Total lung capacity
59
Q

IC =

A

TV + IRV

The amount of air a person can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount ~3500 ml

60
Q

FRC =

A

ERV + RV

The amount of air that remains in the lungs at the end of normal expiration ~2300 ml

61
Q

VC =

A

TV + IRV + ERV

The maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent ~4600 ml

62
Q

TLC =

A

VC + RV

Max volume to which the lungs can be expanded with the greatest possible effort ~5800 ml

63
Q

TV =

A

500 ml

64
Q

IRV =

A

3000 ml

65
Q

ERV =

A

1100 ml

66
Q

RV =

A

1200 ml

67
Q

IC =

A

3500 ml

68
Q

FRC =

A

2300 ml

69
Q

VC =

A

4600 ml

70
Q

TLC =

A

5800 ml

71
Q

Forced vital capacity (FVC)

A

The volume of air which can be forcibly and maximally exhaled out of the lungs after the patient has taken in the deepest possible breath

72
Q

Forced expiratory volume in one second (FEV1)

A

The volume of air which can be forcibly exhaled from the lungs in the first second of a forced expiratory maneuver

73
Q

FEV1/FVC-FEV1 percent (FEV1%)

A

This number is the ratio of FEV1 to FVC and it indicates what percentage of the total FVC was expelled from the lungs during the first second of forced exhalation

74
Q

Forced expiratory vital capacity (FVC)

A

Forced vital capacity (FVC) is the total amount of air exhaled during the FEV test

75
Q

FEV-1 second

A
  • After maximal inspiration, the volume of air that can be forcefully expelled in one second
  • Effort dependent
76
Q

FEV-1 second is normally between ___

A

3-5 L

77
Q

FEV-1 second is also reported as…

A

Percent predicted; percent of FVC—FEV1/FVC is normally > 75%

78
Q

FEV-1 second is most important clinical tool in assessing…

A

The severity of airway obstructive disease

79
Q

Normal FEV1/FVC

A

> 75

80
Q

Mild FEV1/FVC

A

60-75

81
Q

Moderate FEV1/FVC

A

45-60

82
Q

Severe FEV1/FVC

A

35-45

83
Q

Extreme FEV1/FVC

A

< 35

84
Q

Flow-volume loops help distinguish between…

A

Upper airway obstruction (extrathoracic) and generalized pulmonary disease (intrathoracic)

85
Q

An extrathoracic obstruction decreases ___

A

Inspiratory flow

86
Q

An intrathoracic obstruction decreases ___

A

Expiratory flow

87
Q

Flow volume loops in obstructive lung disease

A

> normal

Increased TLC, FRC, RV

88
Q

Flow volume loops in restrictive lung disease

A

< normal

Decreased TLC, FRC, RV

89
Q

In obstructive, FEV1 is more dramatically ___ compared with FVC, leading to ___ FEV1/FVC ratio

A

Dramatically reduced; decreased FEV1/FVC ratio

90
Q

In restrictive, FVC is more ___ or ___ compared with FEV, leading to ___ FEV1/FVC ratio

A

FVC is more reduced or close to same compared with FEV1, leading to increased or normal FEV1/FVC ratio

91
Q

FEF 25-75

A
  • Forced expiratory flow at 25-75% of FVC

- Effort independent

92
Q

FEF 25-75 reflects…

A

Collapse of small airways, peripheral airways

93
Q

FEF 25-75 is a sensitive indicator of…

A

Early airway obstruction

94
Q

MVV or MBC

A

Maximal voluntary ventilation, maximal breathing capacity

“Will to live test”

95
Q

What is MVV/MBC?

A

The maximal amount of air a pt can exhale in one minute at maximal effort (hyperventilation)

Extremely effort dependent, nonspecific

96
Q

MVV or MBC tests…

A

Motivation, mechanics, strength, and endurance

97
Q

A decrease in MVV or MBC has been shown to predict…

A

Increased morbidity and mortality in patients undergoing thoracic surgery

KLowe Anesthesia Physiology 1: Respiratory (13 decks)

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