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Y2 - Resp > Lecture 3 -Properties Of Gases And Diffusion > Flashcards

Lecture 3 -Properties Of Gases And Diffusion Flashcards

1
Q

What is Dalton’s law?

A

States that each gas in a mix of gasses exerts its own pressure called a partial pressure

The total of all the partial pressures of gases in a mixture it the total pressure

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2
Q

What makes a gas move from one area to another?

A

A partial pressure gradient

A gas will move from an area where theres a higher partial pressure to a lower partial pressure

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3
Q

What affects the speed which gases diffuse from one area to another?

A

Steeper the gradient the faster the movement

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4
Q

What does pAO2 refer to?

A

Partial pressure of O2 in alveolar air

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5
Q

What does paO2 refer to?

A

Partial pressure of O2 in arterial blood

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6
Q

Why is the partial pressure of oxygen that gets inhaled different to the partial pressure of oxygen in the trachea?

A

The air gets humidified so some of the oxygen ends up as water vapour

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7
Q

What is the name given to the partial pressure exerted by water vapour at body temperature?

A

Saturated vapour pressure

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8
Q

When doing partial pressure calculations how do you need to consider saturated vapour pressure?

A

You need to subtract the saturated vapour pressure (6.28KPa) from the total/atmospheric pressure

You need to essentially work it from the humidified atmospheric pressure in the body

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9
Q

What is Henrys constant (KH)?

A

Describes how soluble a gas is in a liquid at a certain temperature

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10
Q

What is Henrys law?

A

The amount of gags dissolved in a liquid is proportional to the gases partial pressure above the liquid and its solubility in that liquid

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11
Q

What are the units for concentration of a gas in a liquid?

A

mmol/L

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12
Q

What is the normal partial pressure of oxygen in alveolar air?

A

13.3KPa

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13
Q

What happens to the partial pressure of oxygen in the pulmonary capilaries when the partial reassure of O2 in the alveolar air is 13.3KPa?

A

The partial pressures equilibrates causing the partial pressure of oxygen in the blood in the capillaries to also be 13.3KPa

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14
Q

How is partial pressure of a gas different from the amount of a gas dissolved?

A

Partial pressure is the force of the gas exerted

Amount of gas dissolved is the amount of molecules of a gas dissolved in a solvent

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15
Q

What is the equation for amount of a gas dissolved?

A

Amount dissolved = partial pressure x solubility coefficient of gas

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16
Q

What units measure partial pressures?

A

KPa

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17
Q

What 2 components need to be considered when determining he total gas content?

A

The amount of the gas dissolved in the plasma and the amount of gas bound to. Carrier like Haemoglobin

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18
Q

How does partial pressure of O2 and CO2 change as the air travels from the trachea into the alveoli?

A

pO2 gets lower
pCO2 gets higher

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19
Q

Why is the partial pressure of Oxygen of the alveolar air lower than inhaled air and pCO2 of alveolar air higher than inhaled air?

A

Inhaled air mixes with the old residual air (old air has lower pO2 higher pCO2)

O2 diffuses across alveolar wall

CO2 enters into alveoli from pulmonary capillaries

20
Q

What determines alveolar pO2?

A

Rate at which O2 is taken up by the blood from the alveoli (Q) and rate at which its replenished by alveolar ventilation (V)

21
Q

What is the V:Q ratio?

A

The ratio by which the alveoli is ventilated to the which the alveoli is perfused with blood

22
Q

What layers does oxygen have to diffuse across to reach a red blood cell?

A

Fluid film lining alveolus
Epithelial cell of alveolus
Interstitial space
Endothelial cell of capillary
Plasma
Red cell membrane

23
Q

What factors affect rate of diffusion across the alveolus into the blood?

A

Partial pressure gradient

SA available for diffusion/gas exchange

Thickness/distance molecules must diffuse

Diffusion coefficient for that gas

24
Q

How does Pulmonary fibrosis affect gas exchange?

A

Leads to lots of thick fibrotic tissue being deposited in the interstitium of the lungs

This increases they diffusion distance molecules must diffuse reducing gas exchange rate

25
What are the 2 main properties of a gas affecting the rate of diffusion of the gas?
Solubility of the gas in the liquid Molecular weight of the gas
26
What diffuses faster, O2 or CO2 and why? What has a greater affect on rate of diffusion, solubility or molecular weight?
CO2 since despite having a larger molecular weight than O2 it is much more soluble in plasma than oxygen Solubility has a much greater affect on rate of diffusion than molecular weight
27
Why is the partial pressure gradient of oxygen from the alveolar air compared to the capilaries very steep compared to the partial pressure gradient of CO2?
O2 diffuses much slower so needs more compensation since it’s solubility is much lower
28
In diseased lungs, the exchange of which gas is affected more, oxygen or carbon dioxide and why?
Oxygen Since CO2 diffuses much more easily since its way more soluble
29
How does Emphysema impair difffusion/gas exchange?
Leads to destruction of alveoli so reduces surface area for gas exchange
30
How does pulmonary oedema impair diffusion/gas exchange?
Fluid in the interstitial space increases the diffusion distance impairing gas exchange
31
What is a a normal ventilation/perfusion ratio?
Normal V/Q = 0.8
32
What is the V in V/Q ratio?
V = alveolar ventilation
33
What is the Q in V/Q ratio?
Q = pulmonary blood flow (perfusion
34
How does the Ventilation perfusion ratio differ in different parts of the lung?
Apex of lung the ventilation is good but the amount of blood its receiving (perfusion) is less due to gravity keeping the capillaries closed At bottom of lung the Q is better but the Ventillation isn’t as good
35
When an area of the lung is poorly ventilated how does the body react to try and maintain V/Q?
Vasoconstriction of blood vessels leading to the poorly ventilated area to keep blood away (Hypoxic pulmonary vasoconstriction)
36
During exercise what does the body due to get the ventilation/perfusion matching to reach 1?
Exercise increases cardiac output leading to vasodilation of the apical arteries in the lungs increasing its perfusion
37
Will the value of V:Q (ventilation:perfusion) be lesser or greater than 1 if a poorly ventilated alveolus is perfused?
V decreases Q stays the same So V:Q would decrease so would be less than 1
38
Will the value of V:Q (ventilation:perfusion) be lesser or greater than 1 if we ventilate a poorly perfused alveolus?
V stays the same Q decreased V:Q therefore is higher meaning V:Q > 1 V:Q>1
39
What are some conditions that cause a ventilation perfusion mismatch where the ventilation is reduced? (V:Q < 1)
Pneumonia Asthma COPD
40
What is a condition that cause a ventilation perfusion mismatch where the perfusion is reduced? (V:Q > 1)
Pulmonary embolism (The alveoli still gets good air but less blood?)
41
What is Lung Hypoxic vasoconstriction?
When blood vessels near poorly ventilated areas vasoconstrict to direct blood away
42
What happens to capillary partial pressures of CO2 and O2 if theres inadequate ventilation?
pO2 falls pCO2 rises
43
Why does lung hypoxic vasoconstriction not fully compensate the gas exchange?
The haemoglobin in the well ventilated alveolar capillaries will already be saturated with O2 So the red cells will be unable to bind additional O2 to increase the pO2
44
If pO2 is low in the blood, what can the body try and do to compensate? How does this affect CO2 levels?
Hyperventilation Can lead to normal or low CO2 levels
45
What is a Shunt?
When an alveolus that isn’t ventilated gets perfused with blood leading to no gas exchange occurring Essentially an area that does undergo gas exchange

Y2 - Resp (23 decks)

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