L09: Alveolar Gases And Diffusion

Question 1

What is Pa

Answer 1

Partial pressure of arterial

Question 2

What is PA

Answer 2

Alveolar partial pressure

Question 3

What is the PA(o2)

Answer 3

13

Question 4

What is the PA(co2)

Answer 4

5

Question 5

What is Pv

Answer 5

Venous partial pressure

Question 6

What is Pv(o2)

Answer 6

5

Question 7

What is Pv(co2)

Answer 7

6

Question 8

What is pa(o2)

Answer 8

13

Question 9

What is pa(co2)

Answer 9

5

Question 10

Which process increases PA(co2)

Answer 10

Metabolism

Question 11

What decreases PA(CO2)

Answer 11

Ventilation

Question 12

What is ventilation

Answer 12

Breathing out

Question 13

What is hyperpnoea

Answer 13

When there is an increase in metabolism, ventilation increases to MATCH it

Question 14

When does hyperpnoea occur

Answer 14

During exercise

Question 15

What is hyperventilation

Answer 15

When there is an increase in ventilation above the requirement of metabolism

Question 16

What factor do we need for diffusion to occur

Answer 16

Partial pressure gradient

Question 17

What are the 3 layers of the alveolar capillary membrane

Answer 17

Alveolar epithelium
Basal lamina
Capillary endothelium

Question 18

What does the grahams law state

Answer 18

Diffusion of gases is dependent on partial pressure gradient and bigger molecules diffuse slower

Question 19

Does oxygen or carbon dioxide diffuse slower

Answer 19

Carbon dioxide

Question 20

Why does carbon dioxide diffuse slower than oxygen

Answer 20

Carbon dioxide has a higher molecular weight than oxygen

Question 21

Does carbon dioxide or oxygen more soluble in liquid

Answer 21

Carbon dioxide

Question 22

Which gas will show a diffusion limitation

Answer 22

Oxygen

Question 23

What can diffusion limitation of oxygen result in

Answer 23

Hypoxia (low oxygen)

Question 24

What does Henry’s law state

Answer 24

The concentration of gas in liquid is equal to to the partial pressure times solubility coefficient

Question 25

In general what does diffusion of a gas into blood depend on

Answer 25

Concentration gradient

Question 26

What is partial pressure gradient of a gas dependent on

Answer 26

``` Solubility Chemical combination (form a molecule with haem) ```

Question 27

What does it mean to have a diffusion limited gas

Answer 27

Gas has high solubility and high chemical combination (binds readily with haemoglobin)

Question 28

What does it mean to have a perfussion limited gas

Answer 28

Gas has a low solubility and no chemical combination

Question 29

Name an example of a diffusion limited gas

Answer 29

Carbon monoxide

Question 30

Name an example of a perfusion limited gas

Answer 30

Oxygen | Carbon dioxide

Question 31

What are the 2 main ways of a reduced pulmonary diffusing capacity

Answer 31

Reducing surface area | Increasing diffusion path length

Question 32

How can you reduce surface area

Answer 32

Loss of lung tissue Airway obstruction Capillary obstruction Ventilation/perfusion mismatch

Question 33

How can you increase the diffusion path length

Answer 33

Thickened alveolar capillary membrane Accumulation of lung fluid Increased intracapillary distance

Question 34

When can you get a thickened alveolar capillary membrane

Answer 34

Fibrosis

Question 35

When can you get an increased intracapillary distance

Answer 35

Low haemoglobin

Question 36

If carbon monoxide is diffusion limited what will happen to the other carbon monoxide in the atmosphere

Answer 36

It will move into the lung and never reaches equilibrium

Question 37

How can you increase a perfusion limited gas into the body

Answer 37

Increase the blood flow

Question 38

How can you increase a diffusion limited gas into the body

Answer 38

Increase the alveolar partial pressure of that gas

Question 39

What is a pulmonary diffusing capacity

Answer 39

The ability to diffuse gases across the lungs

Question 40

What is flow of a gas across a diffusion barrier proportional to

Answer 40

Diffusibility of a gas Area Partial pressure gradient Thickness (inversely proportional)

Question 41

What gas do we use to measure the diffusion constant

Answer 41

Carbon monoxide

Question 42

After calculating the diffusion constant with carbon monoxide how do we convert it to a value representing oxygen

Answer 42

Use a conversion factor of 1.25

Question 43

When might we use diffusion constant

Answer 43

When there is a problem with the way the oxygen moves in the lungs and NOT ventilation