L09: Alveolar Gases And Diffusion Flashcards

1
Q

What is Pa

A

Partial pressure of arterial

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2
Q

What is PA

A

Alveolar partial pressure

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3
Q

What is the PA(o2)

A

13

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4
Q

What is the PA(co2)

A

5

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5
Q

What is Pv

A

Venous partial pressure

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6
Q

What is Pv(o2)

A

5

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7
Q

What is Pv(co2)

A

6

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8
Q

What is pa(o2)

A

13

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9
Q

What is pa(co2)

A

5

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10
Q

Which process increases PA(co2)

A

Metabolism

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11
Q

What decreases PA(CO2)

A

Ventilation

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12
Q

What is ventilation

A

Breathing out

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13
Q

What is hyperpnoea

A

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

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14
Q

When does hyperpnoea occur

A

During exercise

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15
Q

What is hyperventilation

A

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

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16
Q

What factor do we need for diffusion to occur

A

Partial pressure gradient

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17
Q

What are the 3 layers of the alveolar capillary membrane

A

Alveolar epithelium
Basal lamina
Capillary endothelium

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18
Q

What does the grahams law state

A

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

19
Q

Does oxygen or carbon dioxide diffuse slower

A

Carbon dioxide

20
Q

Why does carbon dioxide diffuse slower than oxygen

A

Carbon dioxide has a higher molecular weight than oxygen

21
Q

Does carbon dioxide or oxygen more soluble in liquid

A

Carbon dioxide

22
Q

Which gas will show a diffusion limitation

A

Oxygen

23
Q

What can diffusion limitation of oxygen result in

A

Hypoxia (low oxygen)

24
Q

What does Henry’s law state

A

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

25
Q

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

A

Concentration gradient

26
Q

What is partial pressure gradient of a gas dependent on

A
Solubility 
Chemical combination (form a molecule with haem)
27
Q

What does it mean to have a diffusion limited gas

A

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

28
Q

What does it mean to have a perfussion limited gas

A

Gas has a low solubility and no chemical combination

29
Q

Name an example of a diffusion limited gas

A

Carbon monoxide

30
Q

Name an example of a perfusion limited gas

A

Oxygen

Carbon dioxide

31
Q

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

A

Reducing surface area

Increasing diffusion path length

32
Q

How can you reduce surface area

A

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

33
Q

How can you increase the diffusion path length

A

Thickened alveolar capillary membrane
Accumulation of lung fluid
Increased intracapillary distance

34
Q

When can you get a thickened alveolar capillary membrane

A

Fibrosis

35
Q

When can you get an increased intracapillary distance

A

Low haemoglobin

36
Q

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

A

It will move into the lung and never reaches equilibrium

37
Q

How can you increase a perfusion limited gas into the body

A

Increase the blood flow

38
Q

How can you increase a diffusion limited gas into the body

A

Increase the alveolar partial pressure of that gas

39
Q

What is a pulmonary diffusing capacity

A

The ability to diffuse gases across the lungs

40
Q

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

A

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

41
Q

What gas do we use to measure the diffusion constant

A

Carbon monoxide

42
Q

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

A

Use a conversion factor of 1.25

43
Q

When might we use diffusion constant

A

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