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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
PH
7.35-7.45
26
PCO2
35-45 mm Hg
27
PO2
75-105 mm Hg
28
Bicarbonate
20-26 mmoles/L
29
Base excess
-3 to +3 mmoles/L
30
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 ___
0.08 So an acute increase in CO2 to 60 mm Hg should cause a drop in pH to 7.24
31
Hypoxemia
Decrease PO2 in blood, < 75
32
Hypoxia
A low O2 state
33
A-a gradient
Measure of efficiency of lung
34
Formula to calculate PaO2
(PB-PH2O) * (FiO2) - (PaCO2/0.8) Example: PaO2 = (760-47) * (0.21) - (40/0.8) = 100
35
Normal A-a =
Approximately (Age/3)
36
A-a gradient is widened (2 things)....
During anesthesia and with intrinsic lung disease—PTX, PE, V/Q mismatch, diffusion problems
37
A-a gradient is normal with (2 things)...
Hypoventilation or low FiO2
38
Treatment of widened A-a gradient
- Supplemental O2 - Adjust ventilation - Treat atelectasis - Add PEEP - Treat underlying cause
39
Base excess is calculated directly using...
PaCO2, pH, and bicarbonate values
40
Rule: A decrease in bicarbonate by 10 mmoles decreases the pH by ___; likewise, an increase in bicarbonate by 10 mmoles increases pH by ___
0.15 Example: A bicarbonate of 13 would result in a pH of 7.25
41
Respiratory acidosis = ___ pH and ___ PaCO2
Low pH and high PaCO2
42
Causes of respiratory acidosis (5)
- Hypoventilation with hypercarbia - CNS depression—trauma, drugs - Decreased FRC—obesity - Upper or lower airway obstruction - COPD, asthma, pulmonary fibrosis
43
After 1-2 days of respiratory acidosis, ___ occurs
Renal compensation—H+ excreted by kidney and HCO3- reabsorbed into blood to partially correct pH
44
Respiratory alkalosis— ___ pH and ___ PaCO2
High pH and low PaCO2
45
Causes of respiratory alkalosis (10)
- Hyperventilation with hypocarbia - Hypoxic respiration - CNS disease - Encephalitis - Anxiety - Narcotic withdrawal - Pregnancy - Early septic shock - Hypermetabolic states - Artificial ventilation
46
Renal compensation of respiratory alkalosis
Increased excretion of HCO3- and decreased secretion of H+, which partially corrects pH
47
Metabolic acidosis— ___ pH and ___ HCO3-
Low pH and low HCO3-
48
Causes of metabolic acidosis (6)
- Lactic acidosis from hypoperfusion - DKA - Renal disease with bicarbonate loss (anion gap and K+) - HCO3- loss in diarrhea - ASA ingestion - High protein intake
49
Respiratory/renal compensation for metabolic acidosis
- Central chemoreceptors with hypocarbia, more rapid than renal compensation, partial correction - Kidneys may increase H+ excretion
50
Metabolic alkalosis— ___ pH and ___ HCO3-
High pH and high HCO3-
51
Causes of metabolic alkalosis (3)
- Bicarbonate infusion - Metabolism of lactate or citrate - Loss of H+ from vomiting or excessive NGT suctioning
52
Respiratory/renal compensation for metabolic alkalosis
- Limited hypoventilation due to eventual hypoxic drive, partial correction - Kidneys may increase bicarbonate excretion in urine
53
Pulmonary volumes (4)
- Tidal volume - Inspiratory reserve volume - Expiratory reserve volume - Residual volume
54
Tidal volume
Amount of inspired air with a normal breath; amounts to about 500 ml in the avg adult male
55
Inspiratory reserve volume
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
Expiratory reserve volume
Maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration; about 1100 ml
57
Residual volume
Volume of air remaining in the lungs after the most forceful expiration; about 1200 ml
58
Pulmonary capacities (4)
- Inspiratory capacity - Functional residual capacity - Vital capacity - Total lung capacity
59
IC =
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
FRC =
ERV + RV The amount of air that remains in the lungs at the end of normal expiration ~2300 ml
61
VC =
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
TLC =
VC + RV Max volume to which the lungs can be expanded with the greatest possible effort ~5800 ml
63
TV =
500 ml
64
IRV =
3000 ml
65
ERV =
1100 ml
66
RV =
1200 ml
67
IC =
3500 ml
68
FRC =
2300 ml
69
VC =
4600 ml
70
TLC =
5800 ml
71
Forced vital capacity (FVC)
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
Forced expiratory volume in one second (FEV1)
The volume of air which can be forcibly exhaled from the lungs in the first second of a forced expiratory maneuver
73
FEV1/FVC-FEV1 percent (FEV1%)
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
Forced expiratory vital capacity (FVC)
Forced vital capacity (FVC) is the total amount of air exhaled during the FEV test
75
FEV-1 second
- After maximal inspiration, the volume of air that can be forcefully expelled in one second - Effort dependent
76
FEV-1 second is normally between ___
3-5 L
77
FEV-1 second is also reported as...
Percent predicted; percent of FVC—FEV1/FVC is normally > 75%
78
FEV-1 second is most important clinical tool in assessing...
The severity of airway obstructive disease
79
Normal FEV1/FVC
> 75
80
Mild FEV1/FVC
60-75
81
Moderate FEV1/FVC
45-60
82
Severe FEV1/FVC
35-45
83
Extreme FEV1/FVC
< 35
84
Flow-volume loops help distinguish between...
Upper airway obstruction (extrathoracic) and generalized pulmonary disease (intrathoracic)
85
An extrathoracic obstruction decreases ___
Inspiratory flow
86
An intrathoracic obstruction decreases ___
Expiratory flow
87
Flow volume loops in obstructive lung disease
> normal Increased TLC, FRC, RV
88
Flow volume loops in restrictive lung disease
< normal Decreased TLC, FRC, RV
89
In obstructive, FEV1 is more dramatically ___ compared with FVC, leading to ___ FEV1/FVC ratio
Dramatically reduced; decreased FEV1/FVC ratio
90
In restrictive, FVC is more ___ or ___ compared with FEV, leading to ___ FEV1/FVC ratio
FVC is more reduced or close to same compared with FEV1, leading to increased or normal FEV1/FVC ratio
91
FEF 25-75
- Forced expiratory flow at 25-75% of FVC | - Effort independent
92
FEF 25-75 reflects...
Collapse of small airways, peripheral airways
93
FEF 25-75 is a sensitive indicator of...
Early airway obstruction
94
MVV or MBC
Maximal voluntary ventilation, maximal breathing capacity “Will to live test”
95
What is MVV/MBC?
The maximal amount of air a pt can exhale in one minute at maximal effort (hyperventilation) Extremely effort dependent, nonspecific
96
MVV or MBC tests...
Motivation, mechanics, strength, and endurance
97
A decrease in MVV or MBC has been shown to predict...
Increased morbidity and mortality in patients undergoing thoracic surgery

KLowe Anesthesia Physiology 1: Respiratory (13 decks)

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