Ventilation and Diffusion

Question 1

What is Dalton’s Law?

Answer 1

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

Question 2

What is atmospheric pressure?

Answer 2

760mmHg

Question 3

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

Answer 3

159mmHg- 21% of 760mmHg

Question 4

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

Answer 4

Given with inert gases such as nitrogen and helium

This reduces its partial pressure

Question 5

What is Henry’s Law?

Answer 5

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

Question 6

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

Answer 6

Increases by 10x

Question 7

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

Answer 7

Gas will move out of the liquid

Question 8

What is the absolute level of gas dissolved dependent on?

Answer 8

Depends on the solubility of the gas

Question 9

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

Answer 9

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

Question 10

When does nitrogen in blood become a problem?

Answer 10

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

Question 11

Why is atmospheric position not seen in alveoli?

Answer 11

Conducting passageways humidify the air and moistened

Pressure drops to 713mmHg

Question 12

What must oxygen do once it enters the alveoli?

Answer 12

Dissolve in the aqueous layer

Diffuse across the membranes

Enter the blood

Question 13

What is the rate of diffusion proportional to?

Answer 13

Surface area

Solubility

Concentration gradient

Question 14

What is rate of diffusion inversely proportional to?

Answer 14

Tissue thickness

Square root of molecular mass

Question 15

What is the surface area of the lungs?

Answer 15

50-100m2

Question 16

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

Answer 16

104mmHg

40mmHg

Question 17

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

Answer 17

1 second

Question 18

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

Answer 18

0.3s

Question 19

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

Answer 19

Alveolar is 40mmHg

Venous is 45mmHg

Question 20

How does oedema effect diffusion?

Answer 20

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

Question 21

How does emphysema effect diffusion?

Answer 21

Gas exchange is reduced to the surface area decreasing

Question 22

What is gas movements in tissues?

Answer 22

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

Question 23

What differences occur in high altitudes?

Answer 23

Atmospheric pressure is reduced so partial oxygen pressure is reduced

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

Question 24

What are the different pressures in Denver?

Answer 24

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)

Question 25

How does the body compensate for high altitudes?

Answer 25

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

Question 26

How does diving change breathibg?

Answer 26

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

Question 27

What problems occur with nitrogen bubbles?

Answer 27

Can form lethal emboli

Bubbles in the pulmonary circulation

Joins are extremely painful

Strokes

Decompression sickness

Question 28

How do we treat someone with nitrogen poisoning?

Answer 28

Hyperbaric chambers to slowly decompress divers who come up too quickly

Question 29

What occurs when someone rapidly ascends without exhaling?

Answer 29

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

Question 30

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

Answer 30

0. 25s

0. 75s to pass through capillary bed

Question 31

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

Answer 31

104mmHg lower- O2

40mmHg higher

Question 32

Why does carbon dioxide pressure increase in the alveoli?

Answer 32

There is left over air after expiration