Deck 12: Ventilation-Perfusion Relationships

Question 1

Which of the following changes is consistent with hypoxemia due to hypoventilation?

A) Increased P(A-a)O₂
B) Reciprocal changes between PaCO₂ and PaO₂
C) Shunt
D) Dead space

Answer 1

Reciprocal changes between PaCO₂ and PaO₂

Question 2

What is the anticipated P(A-a)O₂ when 100% oxygen is breathed?

A) 10-20 mm Hg
B) 20-30 mm Hg
C) 40-50 mm Hg
D) >50 mm Hg

Answer 2

>50 mm Hg

Question 3

Which of the following is the major effect of a low ratio?

A) Hypercapnia
B) Acidosis
C) Hypoxemia
D) Hypocapnia

Answer 3

Hypoxemia

Question 4

Which of the following statements explains why the mere breathing of 100% oxygen increases the P(A-a)O₂?

A) Because 100% oxygen impairs gas transfer from the alveolus to the blood.
B) Because 100% oxygen improves gas transfer from the alveolus to the blood.
C) Because of the unique way hemoglobin binds O2.
D) Because 100% oxygen does not change gas transfer from the alveolus to the blood.

Question 5

Which of the following clinical conditions associated with alveolar collapse may be adversely affected by PEEP/CPAP?

A) Atelectasis
B) Pulmonary edema
C) ARDS
D) Pneumothorax

Question 6

Which of the following is the most common cause of hypoxemia?

A) mismatch
B) Hypoventilation
C) Relative shunt
D) Dead space

Question 7

Which of the following is the definition of absolute shunt?

A) When ventilation gradually decreases to zero with no change in blood flow
B) When ventilation gradually increases with no change in blood flow
C) When ventilation gradually increases with a corresponding change in blood flow
D) When ventilation gradually decreases to zero with an associated decrease in blood flow

Question 8

Which of the following is an indicator of the severity of shunt?

A) PaO₂
B) P(A-a)O₂
C) PaO₂/FIO₂
D)P CO2

Question 9

Which of the following is the explanation for the production of hyperventilation and respiratory alkalosis associated with hypoxemia?

A) Peripheral chemoreceptor stimulation
B) Central chemoreceptor stimulation
C) Hypoxic drive stimulation
D) Peripheral chemoreceptor antagonism

Question 10

Which of the following is the most common cause of chronic hypercapnia?

A) mismatch
B) Hypoventilation
C) Relative shunt
D)Dead space

Question 11

What type of patients with severe flow limitation an mismatch may be unable to increase their overall alveolar ventilation enough to sustain a normal PaCO₂?

A) Asthmatics
B) Patients with advanced COPD
C) Patients with severe pneumonia
D) Patients with bronchiectasis

Question 12

Which of the following techniques prevent alveolar collapse even during expiration?
I.PEEP
II.CPAP
III.IPAP
IV.IPPB

A) I, II
B) III, IV
C) I, II, III, IV
D) II, III

Question 13

Which of the following are causes of general hypoventilation?
I.Muscle paralysis
II.Muscle weakness
III.Drug-induced respiratory center depression
IV.Muscle spasm

A) I, II
B) I, II, III
C) II, IV
D) I, III

Question 14

Increasing the FIO₂ in patients with shunting will have which of the following effects?

A) It will dramatically improve PaO₂.
B) It will cause little improvement in PaO₂.
C) It will improve PaO₂.
D) It will dramatically decrease PaO₂.

Question 15

Which of the following is considered the best corrective treatment for intrapulmonary shunting?

A) Increase the FIO₂.
B) Eliminate CO₂.
C) Restore ventilation to the airless alveoli.
D) Increase the respiratory rate.

Question 16

Increasing the FIO₂ in patients with mismatch will have which of the following effects?

A) It will not improve PaO₂.
B) It will cause little improvement in PaO₂.
C) It will improve PaO₂.
D) It will decrease PaO₂.

Question 17

What are the major characteristics of increased alveolar dead space?
I.Pulmonary embolism
II.Increased work of breathing
III.Retractions
IV. E out of proportion with the PaCO₂

A) I, II
B) II, IV
C) I, II, III, IV
D) II, III

Question 18

What is the hallmark of intrapulmonary shunting?

A) Refractory hypoxemia
B) Refractory hypercapnia
C) Hypoxemia not refractory to oxygen therapy
D) Hypercapnia not refractory to oxygen therapy

Question 19

Which of the following conditions are associated with dead space?
I.Pulmonary embolism
II.Severe hypotension
III.Alveolar overdistension
IV.Auto-PEEP

A) I, II
B) III, IV
C) I, II, III, IV
D) II, III

Question 20

Which of the following are conditions associated with intrapulmonary shunting?
I.Pneumonia
II.Pulmonary edema
III.Pneumothorax
IV.Bronchial occlusion

A) I, II, III
B) III, IV
C) I, II, III, IV
D) II, III

Question 21

Which of the following statements are true of P(A-a)O₂?
I.Increased P(A-a)O₂ indicates increased physiological shunting.
II.Normal P(A-a)O₂ is approximately 7 to 14 mm Hg during breathing of room air.
III.P(A-a)O₂ is as high as 50 to 60 mm Hg during the breathing of 100% oxygen.
IV.The variability of P(A-a)O₂ with FIO₂ limits its usefulness as a shunt indicator when FIO₂ is changed.

A) I, II
B) III, IV
C) I, II, III, IV
D) II, III

Question 22

Assuming that cardiovascular function is unstable, which of the following is the most reliable indicator of shunt?

A) QS
B) P(A-a)O₂
C) PaO₂/FIO₂
D) PaO₂/PAO₂

Question 23

Which of the following statements are true of the PaO₂/FIO₂?
I.A normal range is approximately 380 to 475.
II.Its usefulness as a shunt indicator is limited.
III.A major problem with PaO₂/FIO₂ is that changes in PaCO₂ affect it.
IV.PaO₂/FIO₂ is the least accurate indicator of shunt.

A) I, II
B) III, IV
C) I, II, III, IV
D) II, III

Question 24

A physician is trying to determine the best index of oxygenation for a patient undergoing mechanical ventilation who has required frequent changes in FIO₂.Which of the following available indices of oxygenation should be recommended for this patient?

A) PaO₂/PAO₂
B) PaO₂/FIO₂
C) P(A-a)O₂
D) PAO₂/PaO₂

Question 25

Which of the following statements are true of PaO₂/PAO₂?
I.PaO₂/PAO₂ is more stable than P(A-a)O₂ when FIO? changes.
II.The lower normal limit for PaO₂/PAO₂ is approximately 0.75.
III.The higher normal limit for PaO₂/PAO₂ is 1.0.
IV.PaO₂/PAO₂ is less stable than P(A-a)O₂ when FIO₂ changes.

A) I, II
B) III, IV
C) I, II, III, IV
D) II, III

Question 26

Which of the following is an indicator of the severity of the dead space?

A) PaO₂
B) P(A-a)O₂
C) PaO₂/FIO₂
D)P CO₂

Question 27

Assuming that cardiovascular function is constant, which of the following is the most reliable indicator of shunt?

A) PaO₂
B) P(A-a)O₂
C) PaO₂/FIO₂
D) PaO₂/PAO₂

Question 28

The record of a patient on mechanical ventilation reveals the following information: VE = 10 L/min, PaCO₂ = 43 mm Hg , = 17 mm Hg, PaO₂ = 70 mm Hg.Can ventilation be considered efficient for this patient?

A) Yes, because the minute ventilation is within normal limits.
B) Yes, because the PaCO₂ is within normal limits.
C) No, because the does not match the P_aCO₂.
D) No, because dead space ventilation is greater than 40%.

Question 29

Which level of calculated shunt fraction is associated with the least significant clinical effect?

A) 10% or less
B) 20% or less
C) 30% or less
D) Less than 50%