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CVR > Pulmonary Vascular Physiology > Flashcards

Pulmonary Vascular Physiology Flashcards

1
Q

Pulmonary circulation

A

From right ventricle
Receives 100% of cardiac output (4.5-8 L/min)
Low pressure system

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2
Q

Bronchial circulation

A

2% of left ventricular output

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3
Q

Red cell transit time of pulmonary circulation

A

5 seconds

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4
Q

Number of capillaries and alveoli in pulmonary circulation

A

280 billion capillaries
300 million alveoli
Surface area for gas exchange 50-100 m^2

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5
Q

Pulmonary artery vessel walls

A

Thin
Minor muscularisation
No need for redistribution in normal state

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6
Q

Systemic artery vessel walls

A

Thick as high pressure system
Significant muscularisation
Need for redistribution

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7
Q

Pulmonary circulation right atrial pressure

A

5 mmHg

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8
Q

Pulmonary circulation right ventricular pressure

A

25/0 mmHg

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9
Q

Pulmonary circulation pulmonary arterial pressure

A

25/8

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10
Q

Systemic circulation left atrial pressure

A

5 mmHg

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11
Q

Systemic circulation left ventricular pressure

A

120/0 mmHg

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12
Q

Systemic circulation aortic pressure

A

120/80 mmHg

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13
Q

Ohm’s law

A

Voltage = current x resistance
Pressure across circuit = cardiac output x resistance

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14
Q

Mean pulmonary arterial pressure - pulmonary arterial wedge pressure left atrial pressure =
mPAP - PAWP =

A

Cardiac output x pulmonary vascular resistance

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15
Q

Pulmonary arterial wedge pressure

A

Pressure of left atrium

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16
Q

Pouiseuille’s law

A

Resistance = (8 x length x viscosity)/ (3.14… x r^4)

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17
Q

Why does on exercise CO increase significantly but mPAP remains stable/increases slightly

A

Reduced pulmonary vascular resistance
Recruitment of closed vessels to perfuse a larger amount of capillary bed
distention (expand radius of vessels)
in response to increased pulmonary artery pressure

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18
Q

Potential Causes of increased viscosity of blood

A

Erythrocytosis (over-production of RBCs)

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19
Q

Type I respiratory failure

A

pO2 < 8 kPa
pCO2 < 6 kPa

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20
Q

Type II respiratory failure

A

pO2 < 8 kPa
pCO2 > 6 KPa
Failure to ventilate alveoli

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21
Q

Causes of hypoxaemia (low oxygen)

A

Hypo ventilation
Diffusion impairment
Shunting
V/Q mismatch

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22
Q

Causes of Hypoventilation

A

Type II respiratory failure
Muscular weakness
Obesity
Loss of respiratory drive

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23
Q

Gaseous Diffusion impairment

A

Pulmonary oedema

24
Q

Blood Diffusion impairment

A

Anaemia

25
Q

Membrane Diffusion impairment

A

Interstitial fibrosis- layering of connective tissue (increases thickness of membrane)
Emphysema- destruction of alveolar bed

26
Q

Perfusion- zone 1 (top of lung)

A

Alveolar pressure > arterial pressure> venous pressure
At resting state- minimal perfusion of lungs
High V/Q ratio

27
Q

Perfusion zone 2 (middle of lungs)

A

Arterial pressure > alveolar pressure > venous pressure
Flow during systole

28
Q

Why does perfusion of lung increase down lung

A

Change in pressures and gravity

29
Q

Perfusion zone 3 (bottom of lung)

A

Arterial pressure > venous pressure > alveolar pressure
Low V/Q ratio
Flow always

30
Q

How does ventilation change down the lung from apex to base

A

Increases

31
Q

How does V/Q (ventilation/blood flow relationship) change throughout lung

A

At bottom of lung, blood flow greater than ventilation (low V/Q)- wasted perfusion
At top of lung, ventilation greater than blood flow (High V/Q)- wasted ventilation

32
Q

Average V/Q

A

0.8

33
Q

Complete shunt

A

Lobar collapse
V/Q = 0

34
Q

Decreased V/Q

A

Narrowing of bronchioles (shunting)
Decreases V/Q
Pneumonia
COPD

35
Q

Pulmonary shunts

A

Complete Lobar Collapse
ArterioVenous Malformation (AVM)

36
Q

Intracardiac shunts

A

eg VSD - R-L Shunt (Eisenmenger’s Syndrome)

37
Q

Physiological shunts

A

Bronchial arteries

38
Q

Eisenmenger’s syndrome

A

Intracardiac shunt due to hole in interventricular septum
Shunt reverses because of high right ventricle pressure
High pulmonary artery pressure- which damages them causing narrowing. Increases pressure

Symptoms: cyanosis., clubbing, erythrocytosis

39
Q

Hypoxic pulmonary vasoconstriction

A

Blood is redistributed away from area of lung which are poorly ventilated - not perfusing not ventilated lungs
Local action of hypoxia on pulmonary artery wall
Weak response as little muscle
Aims to maintain V/Q matching
-Local hypoxia (eg peanut)
-Generalised hypoxia (eg altitude)

40
Q

Dead space ventilation v V/Q mismatch

A

Reduction in perfusion
Causes: peripheral pulmonary embolism
Increase V/Q as ventilation maintaining by Q decreases

41
Q

Alveolar dead space ventilation

A

Central pulmonary embolism
V/Q = infinity as ventilation continues but no blood perfusion

42
Q

Diseases of the Pulmonary Circulation

A

Pulmonary Embolism
Pulmonary Hypertension
Pulmonary AVMs

43
Q

Pulmonary embolism

A

Begins with clot in veins in legs which breaks off and travels to lungs
Central = ischaemia
Peripheral = infarction
Lung infarction: ‘minor’ PE- sharp pleuritic pain and peripheral arteries
Central ‘major’ PE- shock, central chest pain, hypoxia, risk of immediate mortality, affects ability of right ventricle to pump blood

44
Q

Virchow’s triad

A

Thrombosis (clots in blood) = circulatory stasis (eg laying in bed, reduced blood flow) + endothelial injury + hypercoaguable state

45
Q

Ventilation/perfusion scan

A

Shows ventilation and perfusion of lungs

46
Q

Pulmonary Arterial Hypertension

A

Increased Pulmonary Vascular Resistance
Eg uncontrolled proliferation of vessel of wall —> decreases lumen of vessel —> increases after load —> increased size of RV and decreased LV

47
Q

Pulmonary Arteriovenous Malformation

A

Shunt between artery and vein so large amount of blood is going through the lungs without passing capillaries and alveoli
Causes low oxygen, capillaries normally filter blood eg small clots

48
Q

How is CO2 transported in circulation

A

23% bound to Hb
Dissolved in plasma
As HCO3 -

49
Q

Hb is fully saturated……. Of the way through capillary bed

A

25%

50
Q

LA and RA pressure

A

5 mmHg

51
Q

RV pressure

A

25/0 mmHg

52
Q

LV pressure

A

120/0 mmHg

53
Q

Aorta pressure

A

120/80 mmHg

54
Q

Pulmonary artery pressure

A

25/8 mmHg

55
Q

Mean pulmonary arterial pressure - left arterial pressure=

A

CO x pulmonary vascular resistance

56
Q

Pulmonary arterial hypertension

A

Increased pulmonary vascular resistance due to decreased lumen size

57
Q

Which pressure gradient best describes the pressure that drives pulmonary blood flow in an upright lung base

A

Arterial pressure is greater than venous pressure

CVR (22 decks)

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