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Respiratory System > Blood Flow, Gas Exchange and Transport > Flashcards

Blood Flow, Gas Exchange and Transport Flashcards

1
Q

What are the bronchial arteries?

A

Arteries, arising from the systemic circulation, supplying oxygenated blood to airway smooth muscle, nerves and lung tissue

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2
Q

Define Dalton’s Law

A

Total pressure of gas mixture = sum of pressure of individual gases

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3
Q

Define Boyle’s Law

A

Increase volume = decrease pressure

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4
Q

What is the pulmonary system in terms of flow and pressure?

A

High flow, low pressure system
High flow as all the blood in the body must pass through the lungs at the same rate as it travels round the systemic system
Low pressure due to reduce resistance to flow

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5
Q

What is the partial pressure of oxygen in the alveoli and arterial system?

A

100 mmHg

13.3 kPa

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6
Q

What is the partial pressure of oxygen in the tissue cells and venous system?

A

40 mmHg

5.3kPa

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7
Q

What is the partial pressure of carbon dioxide in the alveoli and the arterial system?

A

40 mmHg

5.3 kPa

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8
Q

What is the partial pressure of carbon dioxide in the tissue cells and the venous system?

A

46 mmHg

6.2 kPa

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9
Q

What are 5 factors that affect the rate of diffusion?

A

Proportional to:
Partial pressure of gas
Solubility of gas
Available surface area

Inversely proportional to thickness of membrane - most rapid over short distances

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10
Q

Function of Type on pneumocytes?

A

Specialised for diffusion - provide large surface area and have a thin membrane

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11
Q

How is efficiency of gas exchange maximised?

A

Capillaries are always adjacent to type I alveolar cells
and not beside type II
Elastic fibres are not found between capillaries and alveolar walls
Alveoli have a large surface area
Alveoli have thin membranes

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12
Q

How does emphysema affect gas exchange?

A

Destruction of alveoli tissue reduces surfaces area for gas exchange

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13
Q

How does fibrotic lung disease affect gas exchange?

A

Thickened alveoli membranes show gas exchange

Loss of lung compliance decrease alveolar ventilation

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14
Q

How does pulmonary oedema affect gas exchange?

A

Fluid in the interstitial space increased diffusion distance - however, arterial PCO2 is normal due to high solubility of CO2 in water

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15
Q

How does asthma affect gas exchange?

A

Increased airway resistance decreases airway ventilation

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16
Q

What is the ideal V/Q relationship and is it possible across the whole lung?

A

Ventilation = perfusion

At the base, blood flow is high as arterial pressure > alveolar pressure and vascular resistance decreased (Q > V)

At the apex, blood flow is flow as arterial pressure < alveolar pressure, which compresses the arterioles and increases vascular resistance (V > Q)

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17
Q

State the V/Q ratios

A

V/Q = 1 : perfectly matched
V/Q > 1 : mismatch 1 (less perfusion)
V/Q < 1 : mismatch 2 (less ventilation)

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18
Q

Where does the majority of V/G mismatch occur?

A

At the apex

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19
Q

What is a shunt?

A

When perfusion of alveoli normal, but ventilation of alveoli fails so blood passing it is deoxygenated - V/Q < 1

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20
Q

What are two mechanism when V < Q?

A

Decrease PO2 and underventilated alveoli constrict their arterioles, diverting blood to better ventilated alveoli

Increase PCO2 causes mild bronchodilation

(Constriction of arterioles due to hypoxia is specific to pulmonary vessel, systemic vessels dilate)

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21
Q

Autoregulation when V > Q?

A

Creates alveolar dead space

Increase alveolar PO2 -> pul. vasodilation
Decreased alveolar PCO2 -> bronchial constriction

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22
Q

What is alveolar dead space?

A

Alveoli that are V but not Q

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23
Q

What is anatomical dead space?

A

Air in conducting zone of respiratory tract unable to participate in gas exchange as walls are too thick

24
Q

What is physiological dead space?

A

Anatomical DS + alveolar DS

25
Q

What determines the percentage of saturation of Hb with O2?

A

Arterial PO2

26
Q

What are 3 factors in establishing arterial PO2?

A

Composition of inspired air
Alveolar ventilation rate
Efficiency of gas exchange

27
Q

What is blood’s oxygen carrying capacity with and without haemoglobin?

A

3ml/L

200ml/L

28
Q

Name 4 type of Hb in RBCs

A

HbA most abundant
HbA2
HbF
Glycosylated Hb

29
Q

How does alveolar PO2 indirectly determine Hb saturation with O2?

A

PAO2 = PaO2 which determines % saturation

30
Q

How is the partial pressure gradient maintained at the alveoli?

A

O2 moves into the arterial blood then binds to Hb, removing it from solution and maintaining a low PO2 in solution

31
Q

What does the sigmoidal O2/Hb dissociation curve tell us about % saturation of O2 of 100 to 60 mmHg?

A

When PO2 is high, a small decrease in PO2 doesn’t cause a large decrease in saturation

Allows normal uptake of O2 by Hb when PO2 is reduced

32
Q

Why does foetal haemoglobin have a greater affinity for O2 than HbA?

A

To extract O2 from maternal blood

33
Q

Why does myoglobin have a greater affinity for O2 than HbA?

A

So that it can strip oxygen from HbA in the blood when the skeletal muscle it is contained in is working hard

34
Q

What is anaemia?

A

Any condition where the carrying capacity of the blood is compromised

I.e. iron deficiency, haemorrhage, vit B deficiency

35
Q

What is the PO2 in arteries in someone who has anaemia?

A

Normal PaO2 and gas exchange occurs as normal, but as there are less O2 transporters, O2 dissolves int he plasma and O2 content is decreased

36
Q

How does pH affect Hb affinity for O2?

A

Alkanosis - increase

Acidosis - decrease

37
Q

How does PCO2 affect Hb affinity for O2?

A

Increase PCO2 - deceases affinity

Decrease PCO2 - increases affinity

38
Q

How does temp affect Hb affinity for O2?

A

Increase = decrease

Decrease temp = increase

39
Q

How does DPG affect Hb affinity for O2?

A

Increase DPG = decrease

40
Q

Under what conditions do 2,3-DPG levels increase?

A

Situations with inadequate blood supply:
Heart or lung disease
Living at high altitude

41
Q

Why is co dangerous?

A

Hb has an affinity that is 250 times greater for CO than O2, but it binds readily and dissociated slowly so hard to remove and O2 levels will decrease

42
Q

What are symptoms of CO poisoning?

A

Hypoxia and anaemia
Nausea and headaches
Cherry red skin and mucous membranes
Potential brain damage and death

43
Q

Management for CO poisoning?

A

100% O2 to increase PaO2

44
Q

What are the 5 types of hypoxia?

A 
Hypoxaemia 
Anaemic
Stagnant 
Histotoxic
Metabolic
45
Q

What is hypoxaemia hypoxia?

A

Reduced O2 diffusion in lungs

46
Q

What is anaemic hypoxia?

A

Reduced O2 carrying capacity

47
Q

What is stagnant hypoxia?

A

Heart disease -> inefficient pumping of blood

48
Q

What is histotoxic hypoxia?

A

CO poisoning prevents cells utilising O2

49
Q

What is metabolic hypoxia?

A

O2 delivery does not meet demand (increased during exercise)

50
Q

How does the CO2 split up after it diffuses out of cells into systemic circulation?

A

7% remains dissolved in plasma
23% binds to Hb -> carbaminohemoglobin
70% converted to bicarbonate (HCO3) and H+ ions (which are buffered by Hb -> HbH)

51
Q

What happens in CO2 transport after it splits up?

A

HCO3 enters plasma in exchange for Cl- - choline shift

52
Q

How is the CO2 excreted?

A

7% of CO2 that dissolved in blood diffuses into alveoli
CO2 bound to Hb, unbinds and diffuses into lungs
HCO3 brought back into RBC, converted back into CO2 and diffuses into lungs

53
Q

How does hypoventilation affect pH?

A

Causes CO2 retention and build up, leads to increased [H+] causing respiratory acidosis

54
Q

How does hyperventilation affect pH?

A

Decrease in CO2, leads to decreased [H+] causing alkanosis

55
Q

Define Charle’s Law

A

Volume of gas is related to absolute temperature

56
Q

Define Henry’s Law

A

The amount of gas dissolved is determines by the pressure of the gas and it’s solubility in the liquid

Respiratory System (29 decks)

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