Alveolar Capillary Membrane Surface Area

Question 0

How much surface area of the pulmonary capillaries is available for gas exchange?

Answer 0

70 meters squared

Question 1

How much alveolar surface is available for gas exchange?

Answer 1

80 meters squared

Question 2

Can you maintain adequate gas exchange if you lose a large quantity of surface area due to disease processes?

Answer 2

No; must compensate by increasing RR and tidal volume

Question 3

Can you think of any medical problems acute or chronic that would cause a loss of surface area?

Answer 3

Emphysema, pulmonary edema, atelectasis, pneumonia, pneumothorax and pleural effusion

Question 4

Would you expect hypoxemia to occur and CO2 retention to occur if surface area was decreased?

Answer 4

Yes

Question 5

What is the purpose of alveolar type II cells?

Answer 5

Produce surfactant

Question 6

What is the function of the pores of Kohn?

Answer 6

They are the communication between local alveoli and aid in gas exchange. They are a channel that allows gas to move from one alveoli to another

Question 7

How can smoking and macrophages together result in the development of emphysema?

Answer 7

Macrophages are debris cleaners and are released when a person smokes. As they are cleaning up debris they release chemicals, which break down alveolar structure and lead to emphysema

Question 8

What is surfactant, what does it do and why’s it so important in keeping us alive?

Answer 8

Surfactant breaks down or prevents surface tension from overwhelming the alveoli (overwhelming the alveoli would result in them collapsing)

Question 9

How long do you think you could live without surfactant? What would happen to you if you did not have enough?

Answer 9

We could not live long without it. Alveoli will implode of themselves if there is not enough surfactant, which ultimately results in no gas exchange

Question 10

An increase in capillary hydrostatic pressure can cause pulmonary edema. What is the mechanism of edema, where does the swelling occur? How does it affect gas diffusion?

Answer 10

Capillaries swell up with too much blood and create pressure, pushing plasma against endothelium and into the basement membrane. The basement membrane becomes thicker so less gas diffusion occurs.

Question 11

What are the four layers of the alveolar capillary membrane, starting with the surfactant layer?

Answer 11

Surfactant layer, alveolar epithelium, interstitial space and capillary endothelium

Question 12

What is the connection between surfactant deficiency and the VQ mismatch known as shunting? Describe the cause and effect relationship and the mechanics of it all.

Answer 12

Without surfactant, there is no gas exchange and you don’t get ventilation to that alveolus. It becomes the same value as venous blood

Question 13

Describe the relation of surfactant deficiency to VQ mismatch and shunting

Answer 13

Without surfactant, the radius becomes smaller and the alveoli will snap shut

Question 15

Relate and explain the pressure, volume change, critical opening/closing pressure, hypoxemia and work of breathing of an alveolus without surfactant.

Answer 15

Pressure will increase with no volume change until you reach s critical pressure and a bubble forms. When the bubble actually forms is when you start seeing volume expansion and that’s when you reach critical opening pressure. The bubble expands until it collapses, which signifies the critical closing pressure. Once the bubbles close (alveoli collapsing), the surface area for gas exchange decreases and the amount of work to open it increases. Work of breathing becomes harder and gas exchange no longer occurs, leading to hypoxemia

Question 16

Relate surfactant deficiency to lung compliance change.

Answer 16

Surfactant determines lung compliance and the lungs become very stiff without it

Question 17

Explain alveolar surface tension change and its relationship to lung volume change between end expiration and end inspiration. Why is surface tension at its lowest at the end of expiration?

Answer 17

During expiration without surfactant, surface tension increases and the smaller the radius. If you add surfactant, the smaller molecules become closer together and repel each other to produce pressure and keep the alveoli open

Question 18

Describe the interstitial space in its natural state.

Answer 18

Area that separates the basement membrane of alveolar epithelium from the basement membrane of capillary endothelium, and contains fluid

Question 20

How does an increase in capillary hydrostatic pressure affect the interstitial space?

Answer 20

Hydrostatic pressure increases fluid in the interstitial space and increases the distance oxygen has to travel and decrease diffusion

Question 21

In a normal healthy state what causes oxygen to diffuse across the alveolar capillary gas exchange membrane?

Answer 21

Hemoglobin affinity and a lower diffusion gradient

Question 22

List three pathological problems that can increase the thickness of the “alveolar capillary gas exchange membrane.”

Answer 22

Fluid overload and hyler membrane

Question 23

Fick’s law of diffusion

Answer 23

Vgas = A x D x (P1-P2)
———————-
T

Question 24

What can cause an increase in hydrostatic pressure?

Answer 24

Over hydration; anything in the left side of the heart fails to function properly and fluid starts to build up

Question 25

How does fluid in the interstitial space cause hypoxemia?

Answer 25

Capillary hydrostatic pressure in the interstitial space is low. If you increase the pressure, water will leak into the interstitial space. This space will swell up with fluid and accumulate (pulmonary edema). Interstitial space is emptied by the lymph system. Eventually the lymph system cannot keep up, fluid leaks into sir space and into alveoli. During this whole time, you’re getting lower and lower oxygen diffusion. Low oxygen diffusion results in hypoxemia