Ch 5 Ventilation Part 2

Question 1

What is the arterial Po2 when it is measured at 101 mm Hg?

Answer 1

101 mm Hg

Question 2

What happens to the arterial Po2 due to ventilation-perfusion inequality?

Answer 2

Depression of arterial Po2

Question 3

How does the oxygen dissociation curve affect the oxygen concentration of blood from high ventilation-perfusion ratio units?

Answer 3

It does not increase the oxygen concentration significantly

Question 4

What is the normal alveolar-arterial O2 difference in the upright lung due to ventilation-perfusion inequality?

Answer 4

About 4 mm Hg

Question 5

What technique is used to assess the distribution of ventilation-perfusion ratios in patients with lung disease?

Answer 5

Infusing dissolved inert gases and measuring their concentrations

Question 6

In patients with lung disease, where does considerable blood flow occur in relation to ventilation-perfusion ratios?

Answer 6

To compartments with low ventilation-perfusion ratios

Question 7

True or False: In a lung with ventilation-perfusion inequality, both O2 uptake and CO2 output are reduced.

Answer 7

True

Question 8

What is the primary reason patients with ventilation-perfusion inequality often maintain a normal arterial Pco2?

Answer 8

Increased ventilatory drive due to chemoreceptor response

Question 9

What is referred to as wasted ventilation in the context of ventilation-perfusion inequality?

Answer 9

Ventilation in excess of normal requirements

Question 10

Fill in the blank: The ventilation-perfusion ratio V· A / Q· determines the _______ in any single lung unit.

Answer 10

[gas exchange efficiency]

Question 11

What is the relationship between ventilation-perfusion inequality and the efficiency of gas exchange?

Answer 11

It reduces the efficiency for all gases

Question 12

What is the alveolar-arterial Po2 difference used to measure?

Answer 12

Ventilation-perfusion inequality

Question 13

What are the four causes of hypoxemia?

Answer 13

• Hypoventilation
• Diffusion limitation
• Shunt
• Ventilation-perfusion inequality

Question 14

What does the alveolar-arterial Po2 difference indicate when it is abnormally high?

Answer 14

Ventilation-perfusion inequality

Question 15

What is the expected response of arterial Po2 when supplemental oxygen is administered in cases of shunt?

Answer 15

Increased, but often small

Question 16

What is the effect of increasing ventilation on arterial Po2 in patients with ventilation-perfusion inequality?

Answer 16

Only a modest increase in arterial Po2

Question 17

What is the shape of the CO2 dissociation curve in the physiological range?

Answer 17

Almost linear

Question 18

True or False: The optimal inspired Po2 is constant in all forms of oxygen administration.

Answer 18

False

Question 19

What happens to the arterial Pco2 in patients with ventilation-perfusion inequality if ventilation is increased?

Answer 19

It usually returns to normal

Question 20

What is the significance of the respiratory exchange ratio in calculating the ideal alveolar Po2?

Answer 20

It is used in the alveolar gas equation

Question 21

What is the effect of ventilation-perfusion inequality on CO2 elimination?

Answer 21

Impaired, but can be corrected by increasing ventilation

Question 22

What happens to blood flow in the case of a right-to-left shunt?

Answer 22

It bypasses the ventilated areas, leading to poor oxygenation

Question 23

What will be the arterial Po2 (in mm Hg) if the value is 0.8?

Answer 23

Approximately 60 mm Hg

This is based on the assumption of a normal physiological response.

Question 24

How much does the inspired O2 concentration (%) have to be raised to return the arterial Po2 to its original level?

Answer 24

11%

This is an estimate based on the required adjustments in oxygen levels.

Question 25

What is the shunt as a percentage of cardiac output for a patient with an arterial oxygen concentration of 18 ml·100 ml−1 and mixed venous blood of 14 ml·100 ml−1?

Answer 25

33%

Calculated from the difference in oxygen concentrations.

Question 26

What is the maximum alveolar Pco2 (in mm Hg) for a climber on the summit of Mt. Everest with an alveolar Po2 of 34 mm Hg?

Answer 26

10 mm Hg

This value is derived from the steady-state assumptions under hypoxic conditions.

Question 27

Why is the Pco2 normal in a patient with severe chronic obstructive pulmonary disease and hypoxemia?

Answer 27

Ventilation-perfusion inequality does not interfere with CO2 elimination.

This highlights the difference in gas exchange dynamics.

Question 28

The apex of the upright human lung compared with the base has a higher _______.

Answer 28

Po2

This reflects the regional differences in ventilation and perfusion.

Question 29

If the ventilation-perfusion ratio of a lung unit is decreased by partial bronchial obstruction, what will the affected lung unit show?

Answer 29

A fall in oxygen uptake.

This indicates the impact of ventilation-perfusion mismatch.

Question 30

What is the approximate alveolar-arterial difference for Po2 (in mm Hg) for a patient with arterial Po2 and Pco2 of 49 and 48 mm Hg, respectively?

Answer 30

20 mm Hg

This is determined using the respiratory exchange ratio and arterial blood gas values.

Question 31

What is the predominant mechanism(s) of hypoxemia in a patient with pneumonia and supplemental oxygen?

Answer 31

Ventilation-perfusion inequality

This indicates that the patient’s underlying lung condition affects gas exchange.

Question 32

What would you expect to see as a result of a change in shunt fraction in a patient with pneumonia?

Answer 32

Decreased alveolar Po2

This reflects the impact of increased shunting on oxygenation.

Question 33

What change would you expect when a patient with a large arteriovenous malformation changes from supine to upright position?

Answer 33

Decreased alveolar Po2

This change occurs due to altered blood flow dynamics in the lung.