Pulmonary Function Tests

Question 1

What is an FEV1?

Answer 1

Forced expiratory volume. How much volume can be forcefully exhaled in 1 second

Question 2

What are examples of “high risk PFT results”?

Answer 2

FEV1 < 2L
FEV1/FVC < 0.5
VC < 15cc/kg and < 10cc/kg
VC < 40-50% than predicted

Question 3

What drugs should be avoided in patients reactive airway?

Answer 3

Avoid histamine releasing drugs like:

Pentothal, morphine, atracurium, mivacurium, neostigmine.

Question 4

What is the drug of choice for bronchospasm?

Answer 4

Epinephrine

Question 5

What are extubation criteria?

Answer 5

VSS, awake+alert, rr<30.
MIF is more negative than -20cm H2O.
VC >15cc/kg

Question 6

What should PaO2 and PaCO2 be on ABG at 40%FiO2 prior to extubation?

Answer 6

PaO2 >70
and
PaCO2 <55

Question 7

What are the 4 intubation criteria?

Answer 7

Mechanic, Oxygenation, Ventilation, Clinical

Question 8

What are clinical reasons for intubation?

Answer 8

Epiglotitis, airway burn, chemical burn, mental status

Question 9

What are mechanics reasons for intubation?

Answer 9

RR>35, VC <15cc/kg, MIF more negative than -20cm H2O

Question 10

What are oxygenation reasons for intubation?

Answer 10

PaO2 < 70 on 40% FiO2.

A-a gradient > 350mmHg on 100% O2.

Question 11

What are ventilation reasons to intubate?

Answer 11

PaCO2 >55, Vd/Vt >0.6 (normal deadspace is 30%)

Question 12

Are you more likely to discover a pneumothorax with an inspiratory or expiratory film?

Answer 12

Expiratory Film

Question 13

Normal pH, PCO2, PO2, HCO3, Base

Answer 13

pH 7.35-7.45
PCO2 35-45
PO2 75-105
HCO3 20-26
Base -3 -- +3

Question 14

What is a buffer and what are examples?

Answer 14

Substance that can absorb or donate H+:

HCO3, Hb, serum proteins, Phosphate

Question 15

An Increase in PCO2 by 10mmHg will change the pH by how much?

Answer 15

10mmHg increase will be a 0.08 decrease in pH.

10mmHg decrease will be a 0.08 increase in pH

Question 16

What should the pH be if the PCO2 is 70?

Answer 16

7.16

Question 17

How do you calculate the expected PaO2 for a given FiO2?```

Answer 17

PaO2= (Pb - PH2O) x (FiO2) - (PaCO2/0.8)

Where Pb=760 and PH2O=47

Question 18

A decrease in Bicarb by 10mmoles will change the pH how much?

Answer 18

A decrease in Bicarb by 10mmoles will decrease pH by 0.15. And an increase in Bicarb by 10mmoles will increase pH by 0.15

Question 19

What should the pH be if the bicarb is 33?

Answer 19

7.55

Question 20

What is a good formula for calculating how much HCO3 to give a patient?

Answer 20

(Base deficit x wt in kg x 0.4) in mEq/l, usually replace half of deficit.

Question 21

What is a normal A-a gradient?

Answer 21

Age/3

Question 22

How do you treat a larger than normal A-a gradient?

Answer 22

Supplemental O2, adjust ventilation, tx atelectasis, add PEEP, tx underlying cause.

Question 23

What is an A-a gradient measure?

Answer 23

Measures the efficiency of the lung

Question 24

What causes an A-a gradient to widen?

Answer 24

Anesthesia and intrinsic lung disease (PTX, PE, Shunt, V/Q mismatch, diffusion problems),

Question 25

Respiratory acidosis is defined as what?

Answer 25

Low pH and high PaCO2

Question 26

After 1-2 days of respiratory acidosis, what happens?

Answer 26

Renal compensation occurs

Question 27

What happens during renal compensation for respiratory acidosis?

Answer 27

H+ excreted by kidneys and HCO2 reabsorbed into blood to partially correct pH

Question 28

Respiratory alkalosis is defined by what?

Answer 28

High pH and low PaCO2

Question 29

What happens during renal compensation for respiratory alkalosis?

Answer 29

Increase secretion of HCO3 and decrease secretion of H+ which partially corrects pH

Question 30

What are two reasons that respiratory alkalosis may occur?

Answer 30

Pregnancy and artificial ventilation

Question 31

Metabolic acidosis is defined by what?

Answer 31

pH low and HCO3 Low

Question 32

What are some causes of metabolic acidosis?

Answer 32

Lactic acidosis from hypoperfusion, DKA, renal disease with bicarb loss, HCO3 loss in diarrhea, ASA ingestion

Question 33

How does the body try to correct metabolic acidosis?

Answer 33

Respiratory compensation through ventilation and kidneys may increase H+ excretion

Question 34

Metabolic alkalosis is defined by what?

Answer 34

High pH and high HCO3

Question 35

What are some causes of metabolic alkalosis?

Answer 35

Loss of H+ from vomitting or excessive NGT suctioning, bicarb infusion, metabolism of lactate or citrate

Question 36

What does the body do to try to correct metabolic alkalosis?

Answer 36

Respiratory compensation through limited hypoventilation. | Kidneys may excrete HCO3 in urine

Question 37

What is the most important clinical tool in assessing the severity of airway obstructive disease?

Answer 37

FEV1-second

Question 38

What is a normal FEV1?

Answer 38

3-5L

Question 39

Does an intrathoracic obstruction decrease inspiratory or expiratory flow?

Answer 39

Expiratory flow

Question 40

Does an extrathoracic obstruction decrease inspiratory or expiratory flow?

Answer 40

Inspiratory flow

Question 41

What is test is sometimes called the "will to live" test?

Answer 41

Maximal voluntary ventilation (MVV) or Maximal breathing capacity (MBC)

Question 42

How is MVV or MBC measured?

Answer 42

Maximum amount of air one can exhale in one minute and maximal effort

Question 43

What does an FEF 25-75 measure?

Answer 43

Forced expiratory flow at 25% to 75% of FVC

Question 44

Is FEF effort dependent or independent?

Answer 44

Effort independent

Question 45

What is FEF a good indicator for?

Answer 45

Sensitive indicator of early airway obstruction

Question 46

When assessing degree of risk in obstructive lung disease, what percentage is considered normal?

Answer 46

FEV1/FVC >75

Question 47

When assessing degree of risk in obstructive lung disease, what percentage is considered moderate risk or greater?

Answer 47

FEV1/FVC <60