DIT review - Pulmonary 1

Question 1

What are the 3 openings in the diaphragm (including the structures that pass through and at what level)

Answer 1

• THINK: I ate ten eggs at twelve
  
  • I ate = “I” for IVC and “ate” for T8
  • Ten eggs = “Ten” for T10 and “eggs” for esophAGus and vAGus
  • At twelve = “At” for AAT (Aorta, Azygous, Thoracic) and twelve for T12
• Vena caval formamen (caval opening)
  
  • Contains IVC
  • At level of T8
• Esophageal hiatus
  
  • Contains esophagus and anterior and posterior trunks of the vagus nerve
  • At level of T10
• Aortic hiatus
  
  • Contains aorta, thoracic duct, azygos vein
  • At level of T12

Question 2

What nerves innervate the diaphragm

Answer 2

• Diaphragm is innervated by C3, C4, and C5
  
  • THINK: C3, 4, 5, keeps the diaphragm alive

Question 3

What is the surfactant ratio used to determine fetal lung maturity in utero

Answer 3

Lecithin:Sphingomyelin ratio > 2.0

Question 4

What are the main components of surfactant

Answer 4

• Lecithin
• Phosphatidylcholine

Question 5

What part of the respiratory tree marks the end of the conducting zone and beginning of the respiratory zone

Answer 5

Terminal bronchioles are end of the conducting zone

Respiratory bronchioles are beginning of the respiratory zone

Question 6

Label the lung volume graph

Answer 6

Question 7

What is functional residual capacity?

Answer 7

Volume of gas in lungs after a normal expiration

Question 8

What is the difference between vital capacity and tidal volume

Answer 8

Tidal volume = amount of air in a normal, non-labored breath

Vital capacity = max amount of air that can be expired after a maximum inspiration

Question 9

What are the components of physiologic dead space

Answer 9

• Physiologic dead space (Vd) = Anatomic dead space + functional dead space
  
  • Anatomic dead space = air in the conduction airways
  • Functional dead space = space that is capable of gas exchange, but no gas exchange is occurring

Question 10

What is the equation for physiologic dead space

Answer 10

• Vd = Vt x [(PaCO2 – PeCO2) / PaCO2]
  
  • Vd = physiologic dead space
  • Vt = tidal volume
  • PaCO2 = arterial pCO2
  • PeCO2 = expired air pCO2
• If there is zero dead space, then PaCO2 = PeCO2, and thus Vd = 0

Question 11

Describe the difference between perfusion-limited and diffusion-limited pulmonary circulation

Answer 11

• The amount of O2 being received by pulmonary circulation is depending on both perfusion (blood going to lungs) and diffusion (O2 crossing the alveolar barrier)
  
  • In healthy individuals, the amount of O2 is perfusion-limited
    
    • Gas equilibrates along the length of the capillary, and increased O2 can only occur via increased blood flow
  • In emphysema and fibrosis, the amount of O2 is diffusion-limited
    
    • Gas does not equilibrate by the time blood reaches the end of the capillary

Question 12

What values define pulmonary HTN

Answer 12

• Pulmonary arterial pressure > 25 at rest (normal = 10 mm Hg)
• Pulmonary arterial pressure > 35 during exercise

Question 13

Cause of primary pulmonary HTN

Answer 13

• AKA idiopathic pulmonary HTN
• Associated with abnormalities in BMPR2 (which normally prevents proliferation of vascular smooth muscle)
• Associated with HIV and Kaposi sarcoma
• Seen in young adult females

Question 14

Cause of secondary pulmonary HTN

Answer 14

• Causes:
  
  • Chronic lung disease
    
    • Recall that hypoxemia in pulmonary circulation causes vasoconstriction, and thus an increase in pulmonary arterial pressure
  • Mitral stenosis
    
    • Increased volume in pulmonary circuit
  • Recurrent thromboemboli
  • Autoimmune disease
  • Left-to-right shunts
  • Sleep apnea or high altitude
    
    • Hypoxic vasoconstriction

Question 15

Basic premise behind methemoglobin

Answer 15

• Methemoglobin = hemoglobin with oxidized form of Hb (Fe3+) that does not bind to O2 readily but has increased affinity for cyanide

Question 16

Presentation of methemoglobin

Answer 16

• Cyanosis
• Chocolate-colored blood

Question 17

Potential usefulness of methemoglobin

Answer 17

• You can induce methemoglobinemia with nitrites (will oxidize Fe2+ to Fe3+) in order to treat cyanide poisoning

Question 18

Treatment of methemoglobin

Answer 18

• Methylene blue
• Vitamin C

Question 19

Differentiate between the R and T form of hemoglobin

Answer 19

• Hemoglobin molecule (2a and 2b subunits) exist in 2 forms
  
  • Taut (T) form
    
    • Low O2 affinity
    • THINK: Taut in Tissues
  • Relaxed (R) form
    
    • High O2 affinity
    • THINK: Relaxed in respiratory area

Question 20

What is the basic premise behind carboxyhemoglobin

Answer 20

• Hb bound to CO instead of O2
  
  • Hb has a 200x increase affinity for CO vs. O2, so will preferentially bind CO

Question 21

Describe the Hb-O2 dissociation curve in Carboxyhemoglobin

Answer 21

• It decreases O2 bound to Hb but also causes a L shift in the curve
  
  • Hb bound to O2 is decreased because it is bound to CO instead = the height of curve is lower
    
    • Decreased O2 content in the blood
  • The heme groups NOT bound to CO have increased affinity for O2 = L shift of curve
    
    • This makes it more difficult for O2 to be unloaded in tissues

Question 22

Presentation of carboxyhemoglobin

Answer 22

• Headaches, dizziness, and cherry red skin

Question 23

Causes of carboxyhemoglobin

Answer 23

• Fires, car exhaust, gas heaters

Question 24

Treatment of carboxyhemoglobin

Answer 24

100% O2

Question 25

What is the alveolar gas equation

Answer 25

• Amount of O2 in the alveoli = amount of O2 in inspired air – amount of O2 consumed
  
  • pAO2 = pIO2 – (paCO2 / R)
    
    • pAO2 = alveolar pO2
    • pIO2 = pO2 in inspired air
    • paCO2 = arterial pCO2
  • pAO2 = 150 – (paCO2 / 0.8)

Question 26

What is the A-a gradient and what is a normal value?

Answer 26

• A-a gradient = pAO2 – paO2
  
  • Normal = 10-15 mm Hg
• Increased A-a gradient means that there is a problem with O2 equilibrating between alveoli and arteries:
  
  • Shunting or V/Q mismatch
  • Fibrosis (thickened diffusion barrier)
  • Increased FiO2 (increases pAO2 by flooding alveoli with O2, but there is still a limit as to how much O2 can go into the arteries)
  • Age

Question 27

Describe the difference between hypoxemia, hypoxia, and ischemia

Answer 27

• Hypoxemia = inadequate oxygen in the blood (decreased paO2)
• Hypoxia = inadequate O2 delivery to organs and tissue
• Ischemia = inadequate perfusion

Question 28

What are causes of hypoxemia that result in a normal A-a gradient

Answer 28

• Normal A-a gradient (low pAO2 and low paO2)
  
  • High altitude
  • Hypoventilation

Question 29

What are causes of hypoxemia that result in an elevated A-a gradient?

Answer 29

• High A-a gradient (normal pAO2 and low paO2)
  
  • Pulmonary fibrosis
  • R-to-L cardiac shunt (blood bypasses pulmonary vasculature and does not get oxygenated)
  • V/Q mismatch

Question 30

What are causes of hypoxia

Answer 30

• Hypoxemia
• Anemia (decreased O2 carrying)
• Carbon monoxide poisoning (less O2 bound to Hb)
• Low cardiac output (blood is oxygenated, but just not getting to tissues)

Question 31

What are causes of ischemia

Answer 31

• Obstruction of arterial flow
• Reduced venous drainage

Question 32

In anemia, what will you see in paO2, saO2, and oxygen content?

Answer 32

• Recall:
  
  • PaO2 = saturation of hemoglobin
  • SaO2 = O2 dissolved in blood
• Oxygen content will be decreased because hemoglobin is decreased
• SaO2 measures the saturation of the hemoglobin that you do have, so it won’t change since the remaining hemoglobin will be normally saturated
• PaO2 measures O2 dissolved in blood, which has nothing to do with Hb, so will also be normal

Question 33

In CO poisoning, what will you see in paO2, saO2, and oxygen content?

Answer 33

SaO2 = decreased (CO competes with O2)

PaO2 = normal

Total oxygen content = decreased

Question 34

In polycythemia, what will you see in paO2, saO2, and oxygen content?

Answer 34

PaO2 = normal

SaO2 = normal

Total O2 content = increased

Question 35

What is Virchow’s triad

Answer 35

Increased risk for clotting:

Stasis, hypercoagulable state, endothelial damage

Question 36

What are the EKG changes seen in pulmonary embolism

Answer 36

• EKG changes:
  
  • SIQ3T3 = wide S in lead I, large Q and inverted T in lead III

Question 37

What are the lab values seen in a PE (pO2, pCO2, and pH)

Answer 37

• Low pO2 – due to PE
• Low pCO2 – due to compensatory hyperventilation (respiratory alkalosis)
• High pH – due to low pCO2

Question 38

Causes of fat emboli

Answer 38

long bone fractures and liposuction

Question 39

Complications associated with amniotic fluid emboli

Answer 39

DIC

Question 40

Causes of air emboli

Answer 40

Caisson disease (nitrogen bubble precipitating during ascent)

IV

Question 41

What is the different between a primary spontaneous and secondary spontaneous pneumothorax

Answer 41

• Primary spontaneous pneumothorax
  
  • Occurs in tall, thin, young males
  • Due to rupture of apical blebs
• Secondary spontaneous pneumothorax
  
  • Due to disease lung (e.g. bullae in emphysema, infection) or mechanical ventilation with use of high pressure

Question 42

What is a tension pneumothorax

Answer 42

• Can be any of the above: primary spontaneous, secondary spontaneous, or traumatic pneumothorax
• Air enters the pleural space but cannot exit, and air continues to build up with each breath
• Trachea deviates away from the affected lung
• Needs immediate needle decompression