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MD3001 - Respiratory Physiology > Ventilation and Diffusion > Flashcards

Ventilation and Diffusion Flashcards

1
Q

How do you convert from mmHg to kPa?

A

mmHg x 0.133322

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2
Q

What is atmopheric pressure at sea level?

A

760mmHg

101.325kPa

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3
Q

What are the partial pressure of nitrogen, oxygen and carbon dioxide at normal atmopshier pressure?

A

Nitrogen = 593mmHg

Oxygen = 159mmHg

Carbon Dioxide = 0.29mmHg

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4
Q

What happens to partial pressure if atmopsheric pressure changes?

A

partial pressure changes?

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5
Q

Oxygen can be toxic at high levels. What can be used to replaced it?

A

trimix - nitrogen-oxygen-helium

Heliox - oxygen-helium

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6
Q

What is dalton’s law of partial pressure?

A

in 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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7
Q

What is Henry’s Law?

A

when a mixture of gases is in contact with a lquid, each gas will dissolve in the liquid in proportion to its partial pressure

partial pressure = 10kPa vs 1kPa

x10 more gas will go into solution if its partial pressure is 10kPa compared to 1kPa

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8
Q

What occurs if the partial pressure in the liquid becomes greater than in the air?

A

gas will move out of the liquid

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9
Q

What does the abolsute level of gas dissolved in liquid also depend on?

A

solubility of the gas

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10
Q

Rate the gases in order of solubility at atmopsheric pressure

A

CO2 = most soluble

O2 = 1/20th as soluble

N2 = barely soluble

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11
Q

What occurs if a gas enters a chemical reaction?

A

the total amount of gas in the liquid is the amount of gas dissolved plus that chemically bound in solution

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12
Q

What is alveolar gas not?

A

atmopsheric air

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13
Q

How do the conudtcing passages of the respiratory system alter atmopsheric air?

A

humidify the air so it is warm and moistened

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14
Q

What is the water vapour pressure of warm and moistened air?

A

47mmHg

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15
Q

What is the partial pressure of alveolar gas?

A

760-47 = 713mmHg

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16
Q

What is the partial pressure of O2 and CO2 in the lungs and give an explanation for these values

A
  • O2 = 104mmHg
  • CO2 = 40mmHg
  • alveolar air is made up of fresh air plus the air that remained in the lungs after the last breath
17
Q

What must happen for gas exchange to occur between the alveolar air and the blood?

A
  • dissolve in the aqueous layer (surfactant lining the alveoli)
  • diffuse across the capillary membrane
  • enter the blood
18
Q

What are the major factors that affect the rate of diffusion?

A
  • proportional to surface area, solubility, concentration gradient (difference in partial pressure)
  • inversly proprtional to tissue thickness, √molecular mass
19
Q

What is the main impact of the rate of diffusion

A

limitis how much air gets into the blood

20
Q

How are the lungs adapted to maximase gas exchange?

A
  • surface area is large
  • large number of alveoli
  • small thickness
  • concentration gradient is large
  • molecular mass between gases is insignficiant
  • CO2 is much more soluble than O2
21
Q

Draw a diagram showing the change in PO2 from the start of the capillary to the end

22
Q

Why does CO2 need a smaller concentration gradient into flow into and out of the blood compared to O2

A

More soluble than O2

23
Q

How does oedema alter the respiratory membrane?

A

thickness increases

Full transmit time may not be sufficient enough to complete full gas exchange

More marked effect on O2 than CO2 due to difference in solubility

24
Q

In what condition is the surface area of the lungs decreased and how does this affect gas exchange?

A

Empheysema

gas exchange is reduced

25
Q

In what conditions is gas entry inhibited? And how does this affect gas exchange?

A
  • mucus
  • inflammation of airway
  • tumours

Gas exchange is reduced

26
Q

What are the gas movements at tissue level?

A
  • partial pressure gradients reserved
  • movement of gases is in the oppsoite direction than in the lungs
    • CO2 moves into the blood from tissues
    • O2 moves out of the blood into tissues
27
Q

How is atmospheric pressure affected at altitude?

A

Atmopsheric pressure is reduced so PO2 is also reduced

28
Q

How is the body affected at altitude?

A
  • Hb saturation is reduced
  • Increased release of EPO
29
Q

What are the main health risks of diving?

A
  • air embolism
  • decompression sickness
30
Q

Problems associated with N2 bubbles

A
  • can form lethal emboli
  • bubble in pulmonary circulation
  • joints - painful
  • brain - stroke
  • decompression sickness
31
Q

How are divers who come up too quickly decompressed?

A

Hyperbaric chambers

32
Q

What does rapid ascension without exhaling cause?

A

rupture of alveoli and gas bubbles which enter circulation

MD3001 - Respiratory Physiology (8 decks)

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