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Respiratory system 2017 > Pulmonary blood flow, gas exchange and transport > Flashcards

Pulmonary blood flow, gas exchange and transport Flashcards

1
Q

How does alveolar ventilation and compliance change from the apex to the base of the lung?

A

Increased alveoli ventilation and compliance in the base of the lungs

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2
Q

What circulation is responsible for supplying nutrition to the lungs?

A

Bronchial circulation - feeds airways smooth muscle, nerves and lung tissue

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3
Q

Difference between PA and Pa

A 
PA = pressure in alveolar air
Pa = pressure in arterial blood
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4
Q

What are the tissue values of P02 and PCO2

A 
PO2 = 40mmHg
PCO2 = 46mmHg
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5
Q

What are the lung values for PO2 and PCO2?

A 
PO2 = 100mmHg
PCO2 = 40mmHg
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6
Q

What affects the rate of diffusion across a membrane?

A 
Directly proportional to:
 - partial pressure gradient
 - gas solubility
 - available surface area
Inversely proportional to:
 - thickness of membrane
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7
Q

How does emphysema affect gas exchange?

A

Fewer and larger alveoli through destruction, leading to a reduction of surface area for gas exchange

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8
Q

How does fibrosis affect gas exchange?

A

Fibrotic tissue around elastic fibres separates the capillaries from the type I pneumocytes while also restricting lung expansion, affecting the uptake of O2 from air (inhalation)

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9
Q

What does mismatch of ventilation and perfusion lead to ?

A

Type 1 respiratory failure

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10
Q

Why is blood flow to the base of the lungs high?

A

Arterial pressure exceeds alveolar pressure, making vascular resistance low.

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11
Q

Why is blood flow to the apex of the lungs low?

A

Arterial pressure is lower than alveolar pressure, causing increased vascular resistance which impedes flow

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12
Q

Describe a pulmonary shunt and how the body responds to it

A

Ventilation < perfusion

Shunt is when the alveoli are perfused as normal but ventilation fails to supply there perfused region. This leads to the induction of vasoconstriction of these blood vessels to the poorly ventilated regions of the lung

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13
Q

Describe alveolar dead space and how the body responds to it

A

Ventilation > perfusion

When ventilation is taking place but perfusion isn’t, leading to the body inducing pulmonary vasodilation and bronchial constriction

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14
Q

Whats the difference between alveolar and anatomical dead space?

A

Alveolar - alveoli that are ventilated but not perfused

Anatomical - air in the conducting zone of the lungs not available for gas exchange

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15
Q

What is physiological dead space?

A

Alveolar dead space + anatomical dead space

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16
Q

Define pulmonary pressure

A

Systolic - 25mmHg
Diastolic - 8mmHg

Why its so affected by gravity

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17
Q

Why does CO2 diffuse more rapidly?

A

Greater solubility

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18
Q

How much O2 dissolves into the blood (without Hb)?

A

3ml/L

19
Q

How much does Hb increase the O2 carrying capacity of blood?

A

3ml/L to 200ml/L

20
Q

How do you calculate O2 delivery to the lungs?

A

Arterial content of O2 x cardiac output

21
Q

What % of arterial O2 is extracted by peripheral tissues at rest?

A

25% (02 demand = 250ml/min, supply is 1000ml/min)

22
Q

What % of O2 in the blood is bound to Hb?

A

98%

23
Q

How much O2 does Hb bind?

A

4 molecules of O2 = 1.34ml 02/g of Hb

24
Q

What % of total Hb is HbA?

A

92%

25
Q

How saturated is Hb at normal systemic arterial pressure (PO2 of 100mmHg)?

A

~100%

26
Q

How saturated is Hb at normal systemic venous pressure (PO2 of 40mmHg)?

A

75%

27
Q

Which has a higher affinity for O2 - myoglobin or foetal myoglobin?

A

Myoglobin

28
Q

Define anaemia

A

Any condition where the O2 carrying capacity of blood is compromised e.g. iron deficiency, B12 deficiency, haemorrhage etc

PaO2 is normal but total blood O2 is low

29
Q

What factors decrease the affinity of Hb for O2?

A

Decreased pH (acidic)
Increased PCO2
Increased temperature
Binding of 2,3 - diphosphoglycerate

30
Q

What factors increase the affinity of Hb for O2?

A

Increased pH (alkalosis)
Decreased PCO2
Decreased temperature

31
Q

What is 2,3-diphosphoglycerate?

A

Synthesised by RBCs, and is increased in situations associated with inadequate O2 supply e.g. heart/lung disease, living at high altitude. Aims to help maintain O2 release

32
Q

Where does carbon monoxide come from?

A

Incomplete combustion of carbon fuel e.g. car exhaust fumes, faulty heating appliances, lawn mowers

33
Q

How does the Hb binding affinity of CO compare to that of O2?

A

Affinity 250x greater than O2

34
Q

What PCO is required for damage?

A

0.4mmHg

35
Q

What are the symptoms of carbon monoxide poisoning?

A 
Hypoxia
Anaemia
Nausea
Headaches
Cherry red skin
Can lead to brain damage and death
36
Q

How does carbon monoxide poisoning affect RR?

A

Unaffected due to normal PCO2

37
Q

How do you treat carbon monoxide poisoning?

A

Removal from source

100% O2 till PaO2 increases

38
Q

What are the 5 types of hypoxia?

A 
Hypoxic hypoxia
Anaemic hypoxia
Ischaemic/stagnant hypoxia
Histotoxic hypoxia
Metabolic hypoxia
39
Q

How is CO2 transported in the blood?

A

70% - forms carbonic acid in RBCs, which is then broken by carbonic anhydrase into bicarbonate and H+ ions
23% - binds deoxyhaemoglobin
7% - dissolved in plasma

40
Q

What is formed when CO2 binds to deoxyhaemoglobin in RBCs?

A

Carbamino compounds

41
Q

What is the main function of carbonic anhydrase?

A

Interconverts CO2 as carbonic anhydrase and bicarbonate to maintain acid-base balance in the blood

42
Q

What does hypoventilation lead to clinically?

A

Respiratory acidosis by CO2 retention

43
Q

What does hyperventilation lead to clinically?

A

Respiratory alkalosis

44
Q

What are the possible uses of respiratory acidosis and alkalosis in the body as a beneficial phenomenon?

A

Can be used to counteract metabolic acidosis/alkalosis to help return acid-base balance to normal

Respiratory system 2017 (31 decks)

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