Lecture 18: O2 and CO2 exchange

Question 1

What is the equation used for how much air we breath?

Answer 1

Ve = Vt x f
…
Respiratory minute volume (L/min) = Tidal Volume (L/breath) x Respiratory rate (breaths/min)

Question 2

How do we figure out Alveolar Ventilation?

Answer 2

VA = (VT- VD) x f

Alveolar Ventilation (L/min) = (Tidal Volume (L/breath) - Dead Space (L/breath)) x Respiratory Rate (breaths/min)

Dead space (VD) is air that is stuck in passage way and isn’t used

Question 3

Which of the following statements about alveolar ventilation is NOT CORRECT?
A. Alveolar ventilation is measured as a volume of air
per unit time.
B. Alveolar ventilation is affected by the amount of dead
space in the respiratory system.
C. The frequency of breaths affects alveolar ventilation.
D. Alveolar ventilation is usually a bit higher than
respiratory minute volume.

Answer 3

D

Question 4

How does gas move across the membranes?

Answer 4

Gases move across the membranes between the alveoli and the capillaries by diffusion

Question 5

What effect does Emphysema have?

Answer 5

It is a disease characterized by dilation of the alveolar
spaces and destruction of the alveolar walls.

This causes a Reduction in surface area means less contact between the air and capillaries, so oxygen exchange is greatly reduced

Question 6

What determines the rate of diffusion?

Answer 6

• Surface area of the membranes
• Thickness of the membranes
• Pressure difference between the two sides

Question 7

Is the blood-air barrier thin or thick? What condition can change this?

Answer 7

Blood air barrier very thin so better diffusion.. Pulmonary fibrosis can increase thickness which decreases diffusion

Question 8

How is high SA achieved in the lungs for gas exchange?

Answer 8

bulbous alveoli and high density of capillaries allows > SA

Question 9

How is the pressure difference between gases related to gas exchange? Think of when resting vs exercise

Answer 9

Low activity
* Reduced oxygen consumption
* Higher levels of oxygen in the venous blood (less O2 diffusion into blood)
* Low CO2 being produced (less CO2 diffusion into the air)

High activity
* Increased oxygen consumption
* Lower levels of oxygen in the venous blood (more O2 diffusion into blood)
* High CO2 being produced (more CO2 diffusion into the air)

Question 10

A person with pulmonary fibrosis has increased thickness of the Blood Air Barrier. Which of the following statements is most likely to be CORRECT for this person?
A. Their breathing frequency will be reduced.
B. Their blood oxygen will be reduced.
C. Their blood carbon dioxide will be reduced.
D. Their hematocrit will be reduced.

Answer 10

B