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HUBS192 2024 > Lecture 18: O2 and CO2 EXCHANGE > Flashcards

Lecture 18: O2 and CO2 EXCHANGE Flashcards

1
Q

What is the formula for respiratory minute volume?

A

Tidal volume x respiratory rate

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2
Q

What are the units of respiratory minute volume?

A

L/min

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3
Q

What are the units of tidal volume?

A

L/breath

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4
Q

What are the units of respiratory rate?

A

Breaths/min

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5
Q

What is tidal volume also known as?

A

Breathing strength

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6
Q

What is respiratory rate also known as?

A

Breathing speed

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7
Q

Can all the respiratory minute volume be used?

A

No, some of the air never gets to the alveoli and so cannot gas exchange

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8
Q

What is the air which can’t gas exchange called?

A

Dead space (Vd)

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9
Q

How much is dead space?

A

About 150mL

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10
Q

What is dead space interpreted as?

A

About 150mL of each breath just fills upper airways (conducting airways) and is of no use for gas exchange

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11
Q

What is really important?

A

The amount of air that gets into the alveoli (alveolar ventilation)

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12
Q

What is the formula for alveolar ventilation?

A

(tidal volume - dead space) x respiratory rate

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13
Q

What are the units of dead space?

A

L/breath

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14
Q

What is dead space also known as?

A

Air that can’t be used. It is constant

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15
Q

What does each gas do in a gas mixture (air?

A

Exert its own own individual pressure, called a partial pressure

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16
Q

What is the pressure of a mixture of gases equal to?

A

The sum total of the pressures of each individual gas

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17
Q

What is inhaled air?

A

Dry and as it becomes filled with water vapour and moistened, the partial pressure of nitrogen and oxygen decrease

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18
Q

What is the goal?

A

To move gas back and forth between the alveoli and the capillaries

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19
Q

Where is inhaled oxygen transported?

A

Into the capillaries

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20
Q

Where is carbon dioxide transported?

A

Into the alveoli to be exhaled

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21
Q

Where do gases move?

A

Across the membranes between the alveoli and the capillaries by diffusion

22
Q

What determines rate of diffusion?

A

Surface area of the membranes, thickness of the membranes and pressure difference between the two sides

23
Q

What is the formula for flux (amount flowing)?

A

F=(A/T)*D(P1-P2)

24
Q

What is A?

A

Surface area

25
Q

What is T?

A

Thickness

26
Q

What is diffusion constant?

A

D

27
Q

What os P1-P2?

A

Pressure difference

28
Q

What does the diffusion constant depend on?

A

Gas solubility (S) and its molecular weigth

29
Q

How do carbon dioxide and oxygen differ in diffusion speed?

A

On a per molecule basis, carbon dioxide diffuses about 20 times faster than oxygen due to higher solubility of carbon dioxide

30
Q

Does diffusion constant affect flux?

A

Not usually

31
Q

What is the surface area?

A

Bulbous structure of alveoli and the high density of capillaries creates lots of surface area for gas exchange

32
Q

What is emphysema?

A

A disease characterised by dilation of the alveolar spaces and destruction of the alveolar walls

33
Q

What does reduction in surface area mean?

A

Less contact between the air and capillaries so oxygen exchange is greatly reduced

34
Q

What is the relationship between flux and thickness?

A

Flux is inversely proportional to thickness

35
Q

What is the blood air barrier mostly comprised of?

A

The alveolar and capillary walls

36
Q

What is the distance between the alveolar air and the blood?

A

Very small

37
Q

What happens in pulmonary fibrosis?

A

Thicker walls so diffusion decreases

38
Q

What does gas transfer by diffusion depend on?

A

Alveolar area for diffusion and thickness of alveolar membrane

39
Q

What is the main factor of gas transfer by diffusion?

A

Pressure difference is driven by diffusion (alveolar - arterial)

40
Q

What does alveolar partial pressure of oxygen depend on?

A

Partial pressure of oxygen in inspired air, alveolar ventilation and oxygen consumption - blood oxygen

41
Q

What is most important in alveolar partial pressure of oxygen?

A

Balance between oxygen consumption and alveolar ventilation because the atmospheric partial pressure of oxygen is usually constant

42
Q

What does low activity do to blood oxygen?

A

Reduced oxygen consumption by cells so higher levels of oxygen in the venous blood

43
Q

What does high activity do to blood oxygen?

A

Increased oxygen consumption by cells so lower levels of oxygen in the venous blood

44
Q

What does alveolar partial pressure of carbon dioxide depend on?

A

Partial pressure of carbon dioxide in inspired air, alveolar ventilation and carbon dioxide production

45
Q

What is alveolar partial pressure of carbon dioxide usually determined by?

A

The balance between carbon dioxide production and alveolar ventilation because atmospheric partial pressure of carbon dioxide is negligible

46
Q

What is the partial pressure of oxygen in the capillaries and alveolus?

A

It is high in the alveolus and low in the capillary

47
Q

Where does oxygen diffuse?

A

Down the pressure gradient from alveolus to capillaries until a balance of the partial pressure of oxygen is reached

48
Q

What is the partial pressure of carbon dioxide in the capillaries and alveolus?

A

High in the capillaries and low in the alveolus

49
Q

Where does carbon dioxide diffuse?

A

Down the pressure gradient from capillaries to alveolus until a balance of partial pressure of carbon dioxide is reached

50
Q

What are the gradients in external respiration?

A

Gradient for oxygen to move into capillaries and carbon dioxide to diffuse into the alveolus

51
Q

What are the gradients in internal respiration?

A

Gradient for oxygen to move into the cells and carbon dioxide to diffuse into the capillaries

HUBS192 2024 (38 decks)

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