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MD3001 Week 8 > Ventilation and Diffusion > Flashcards

Ventilation and Diffusion Flashcards

1
Q

What is Dalton’s Law?

A

A mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases

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2
Q

What is atmospheric pressure?

A

760mmHg

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3
Q

If oxygen makes up 21% of the gas in air, what is its partial pressure?

A

159mmHg- 21% of 760mmHg

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4
Q

What is used to give oxygen as it is toxic at high levels?

A

Given with inert gases such as nitrogen and helium

This reduces its partial pressure

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5
Q

What is Henry’s Law?

A

Henry’s Law states that the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid

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6
Q

What is the ratio of dissolving if the partial pressure of a gas increases from 1kPa to 10kPa above a solution?

A

Increases by 10x

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7
Q

What happens if the partial pressure in a liquid is greater than the air?

A

Gas will move out of the liquid

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8
Q

What is the absolute level of gas dissolved dependent on?

A

Depends on the solubility of the gas

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9
Q

Explain the difference In solubility of gases and that relation to partial pressures?

A

Carbon dioxide is most soluble with oxygen around 1/20th as soluble

Nitrogen is barely soluble in atmospheric pressure despite having the highest partial pressure

This is down to solubility in liquids

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10
Q

When does nitrogen in blood become a problem?

A

During deep diving where the partial pressure increases so much, nitrogen is forced into the blood

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11
Q

Why is atmospheric position not seen in alveoli?

A

Conducting passageways humidify the air and moistened

Pressure drops to 713mmHg

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12
Q

What must oxygen do once it enters the alveoli?

A

Dissolve in the aqueous layer

Diffuse across the membranes

Enter the blood

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13
Q

What is the rate of diffusion proportional to?

A

Surface area

Solubility

Concentration gradient

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14
Q

What is rate of diffusion inversely proportional to?

A

Tissue thickness

Square root of molecular mass

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15
Q

What is the surface area of the lungs?

A

50-100m2

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16
Q

What Is the difference between the partial pressures of oxygen between the alveolar air and the venous blood?

A

104mmHg

40mmHg

17
Q

At rest, how long does it take for blood to pass through pulmonary capillaries?

A

1 second

18
Q

In exercise, how long does it take for blood to pass through pulmonary capillaries?

A

0.3s

19
Q

What are the different partial pressures of carbon dioxide between the alveolar air and the venous blood?

A

Alveolar is 40mmHg

Venous is 45mmHg

20
Q

How does oedema effect diffusion?

A

Thickeness of membrane increases

This means full transit time may not be sufficient to complete gas exchange

This has a greater effect on oxygen as carbon dioxide is more soluble

21
Q

How does emphysema effect diffusion?

A

Gas exchange is reduced to the surface area decreasing

22
Q

What is gas movements in tissues?

A

In reverse

Movement of gases in opposite direction than in the lungs

CO2 moves into blood from tissues

Oxygen moves out of blood into tissues

23
Q

What differences occur in high altitudes?

A

Atmospheric pressure is reduced so partial oxygen pressure is reduced

Haemoglobin saturation is reduced and there is an increase release of erythropoietin

24
Q

What are the different pressures in Denver?

A

Atmospheric pressure is 632 mmHg (down from 760 mmHg)

Inspired PO2 – 125 mmHg (down from 149 mmHg)

Alveolar PO2 – 84 mmHg (down from 104 mmHg)

Alveolar PCO2 – 34 mmHg (down from 40 mmHg)

25
Q

How does the body compensate for high altitudes?

A

Average male haemoglobin rises from 150g/l to 190 g/l

26
Q

How does diving change breathibg?

A

Atmospheric pressure increases by 1 atmosphere every 10m depth

Air enters lung at increased pressure which forces nitrogen into the blood stream

As you then ascend to the surface gas bubbles of nitrogen starts to form

27
Q

What problems occur with nitrogen bubbles?

A

Can form lethal emboli

Bubbles in the pulmonary circulation

Joins are extremely painful

Strokes

Decompression sickness

28
Q

How do we treat someone with nitrogen poisoning?

A

Hyperbaric chambers to slowly decompress divers who come up too quickly

29
Q

What occurs when someone rapidly ascends without exhaling?

A

As you move to shallow water, atmospheric pressure decreases

Volume of air in the lungs increases

This causes ruptures of alveoli and gas bubbles enter circulation (arterial gas embolism)

Usually lodge in cerebral circulation

Can cause seizures, fits, unconsciousness

30
Q

How long does it take for full gas exchange of oxygen?

A
  1. 25s

0. 75s to pass through capillary bed

31
Q

What is the oxygen and carbon dioxide pressures in the alveoli?

A

104mmHg lower- O2

40mmHg higher

32
Q

Why does carbon dioxide pressure increase in the alveoli?

A

There is left over air after expiration

MD3001 Week 8 (7 decks)

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