Respiratory System

Question 1

What happens to P_ACO₂ as minute ventilation increases linearly?

Answer 1

P_ACO₂ decreases asymptotically

Question 2

What is the most appropriate initial treatment for a patient who has a generalized seizure during hyperbaric oxygen therapy?

Answer 2

discontinue inhaled oxygen

Question 3

What factors can reduce hypoxic pulmonary vasoconstriction during one lung ventilation?

Answer 3

• ACE inhibitors, calcium channel blockers, nitroglycerin, sodium nitroprusside, acetazolamide, corticosteroids, nitric oxide, prostacyclin
• hypocapnea
• volatile anesthetics

Question 4

What factors enhance hypoxic pulmonary vasocontriction?

Answer 4

• hypercapnea
• catecholamines, phenylephrine

Question 5

What anesthetic agents do no affect hypoxic pulmonary vasocontriction?

Answer 5

propofol

nitrous oxide

Question 6

What is the effect of dexmedetomidine on the hypercapnic ventilatory response?

Answer 6

no effect

Question 7

What primarily determines the resting tone of airway smooth muscle?

Answer 7

parasympathetic tone

Question 8

What is the alveolar gas equation?

Answer 8

P_AO₂ = FiO₂ (P_atm - pH₂O) - P_aCO₂/0.8

P_atm ~ 760 mmHg

pH₂O ~ 47 mmHg

Question 9

What is the oxygen content equation?

Answer 9

C_aO₂ = (S_aO₂ x Hgb x 1.34) + (0.003 x P_aO₂)

** mL of O₂ per 100 mL blood **

Question 10

What happens to P_aCO₂ during apneic oxygenation?

Answer 10

increases by 6 mmHg in the first minute and 3 mmHg in each subsequent minute

Question 11

What is the P₅₀ of oxygen binding to hemoglobin?

Answer 11

S_aO₂ 50% -> P_aO₂ 27 mmHg

Question 12

What does a typical blood gas show in pulmonary embolism?

Answer 12

hypoxemia and respiratory alkalosis

Question 13

What are the pulmonary complications of ankylosing spondylitis?

Answer 13

pulmonary fibrosis

restrictive lung disease

Question 14

What are the approximate FiO2s delivered by nasal cannula? Simple face mask? Venturi mask? Non-rebreather?

Answer 14

2L nasal cannula ~25%

6L nasal cannula ~ 40%

simple face mask ~50%

Venturi mask - adjustable

non-rebreather ~90%

Question 15

By how much does hemidiaphragmatic paralysis decreased indices of pulmonary function?

Answer 15

~25%

Question 16

What is the intrapleural pressure at normal end expiration in a healthy person?

Answer 16

-5 cmH₂O

Question 17

Where in the lungs are ventilation and perfusion maximal?

Answer 17

Both are maximal at the base

Question 18

What are the non-cardiogenic, modifiable causes of pulmonary hypertension?

Answer 18

hypoxia

hypercarbia

acidosis

Question 19

What part of the brainstem coordinates inspiration? Expiration?

Answer 19

dorsal medullary center: inspiration

ventral medullary center: expiration

Question 20

Which receptors mediate hypoxic respiratory drive?

Answer 20

chemoreceptors in the aortic arch and carotid body

Question 21

Why shouldn’t you give a patient with severe COPD too much supplementary oxygen?

Answer 21

It will interfere with HPV and worsen V/Q matching

Question 22

How does blood in the ventricles increase respiratory rate in patients with TBI/hemorrhage?

Answer 22

Blood provides H⁺ ions and lower CSF pH

Question 23

Through what mechanism can intubation cause bronchospasm?

Answer 23

direct parasympathetic activation

Question 24

Is right heart failure more common in chronic bronchitis or emphysema?

Answer 24

chronic bronchitis

(causes elevated PA pressures earlier in the disease)

Question 25

What are the most common EKG changes with massive PE?

Answer 25

tachycardia and ischemic changes (TWIs or ST depressions) in anterior prechordial leads (esp. V1-V2)

*S1Q3T3 is very specific for right heart strain from PE, but rarely seen*

Question 26

With regard to variable intrathoracic and extrathoracic airway obstructions, which causes more obstruction to flow during inspiration? During expiration?

Answer 26

variable extrathoracic obstructions block flow more during inspiration

variable intrathoracic obstructions block flow more during expiration

Question 27

What are the flow-volume loops like for variable intrathoracic and extrathoracic obstructions? Fixed obstruction?

Answer 27