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CVR Lectures > Pulmonary Vascular Physiology > Flashcards

Pulmonary Vascular Physiology Flashcards

1
Q

How is the blood supplied/circulated to the lungs?

A

Through a dual blood supply:
- Pulmonary circulation
- Bronchial circulation

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2
Q

Where does pulmonary circulation occur?

A

From the right ventricle

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3
Q

How much of the blood flow is pulmonary circulation?

A

100%

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4
Q

How much is the bronchial circulation and where is it from?

A

2% of Left ventricular output, which perfuses lung tissue itself.

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5
Q

Describe the root of the pulmonary circulation?

A
  • Blood leaves the right ventricle via a single large artery, the pulmonary trunk, which divides into the two pulmonary arteries, one supplying the right and one supply the left lung.
  • In the lungs the arteries continue to branch and
    connect to arterioles, leading to capillaries that unite into venules and then veins.
  • The blood leaves the lungs via four pulmonary veins, which empty into the left atrium
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6
Q

How long does a RBC take to pass through the pulmonary circulation?

A

5 seconds (quite slow)

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7
Q

what is the difference in vessel wall thickness between pulmonary and systemic circulation?

A

Pulmonary - Thin
Systemic - Thick

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8
Q

what is the difference in muscularization between pulmonary and systemic circulation?

A

Pulmonary - Minor
Systemic - Significant

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9
Q

what is the difference in need for redistribution between pulmonary and systemic circulation?

A

Pulmonary - Not in the normal state
Systemic - Yes

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10
Q

What is systemic circulation?

A

Provides the functional blood supply to all body tissue. Via the aorta, which then divides into
progressively smaller vessels. The smallest arteries branch into arterioles, which
branch into roughly 10 billion very small vessels, the capillaries, which unite to form
larger-diameter vessels known as venules. The arterioles, capillaries & venules
are collectively referred to as the MICROCIRCULATION.

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11
Q

What is Pouiseuille’s Law?

A

Resistance = (8 x L x Viscosity)/ ( Pie x r^4)

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12
Q

What is the importance of Pouiseuille’s Law?

A

Shows that a small change in radius causes a big change to resistance due to the r^4

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13
Q

What is Ohm’s Law?

A

V = IR
Voltage across circuit = Current X resistance

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14
Q

How do we use Ohm’s Law for pressure across Pulmonary Circulation?

A

V = IR
Pressure across circuit (mPAP - PAWP) = Cardiac Output x Resistance (PVR)

mPAP (mean pulmonary arterial pressure)
PAWP (Pulmonary arterial wedge pressure ;eft atrial pressure)
CO (cardiac output)
PVR (Pulmonary vascular resistance)

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15
Q

What happens to the mean pulmonary arterial pressure when we exercise?

A

On exercise mPAP remains stable in normal subjects but CO increases significantly. This is possible because the resistance falls

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16
Q

How can we reduce resistance?

A
  • Recruit more capillaries
  • Distend some vessels (bulging of vessels)
17
Q

What is Type I respiratory failure defined by?

A
  • pO2 < 8kPA
  • pCO2 <6 kPA
18
Q

What is Type II respiratory failure defined by?

A
  • pO2 < 8kPA
  • pCO2 >6 kPA
19
Q

What are some causes of hypoxaemia (O2 levels are low)

A
  • Hypoventilation (reduced ventilation/ air coming in)
  • Diffusion impairment
  • Shunting
  • V/Q mismatch
20
Q

What is hypoventilation the cause of?

A
  • Type I Respiratory failure
    (failure to excrete the CO2)
  • Failure to ventilate the alveoli
  • Muscular weakness
  • Obesity
  • Loss of respiratory drive
21
Q

What are the three different diffusion impairments?

A
  • Gaseous diffusion: pulmonary oedema (Diffusion in alveoli)
  • Membrane diffusion: Interstitial fibrosis
    (from alveoli to blood vessel)
  • Blood diffusion: Anaemia (through the blood vessel wall)
22
Q

What is the V/Q mismatch?

A

Ventilation/ Perfusion mismatch

23
Q

What is the V/Q mismatch like in the lungs?

A

Perfusion increases as we go down the lungs as at the top of the lungs there is very little flow

24
Q

What are the pressures like at the top of the lungs?

A

The alveolar pressure Pa is greater than the arterial and venous pressure. Therefore very little flow/ perfusion

25
Q

What are the pressures like at the bottom of the lung?

A

The arterial and venous pressure is bigger than the alveolar pressure. Therefore more perfusion and blood flow

26
Q

What happens if we have a complete shunt in the alveoli?

A

Means the alveoli are blocked off so V/Q = 0 as there would be no ventilation but there would be perfusion.
If it was partially blocked there would be small ventilation so just a lower V/Q

27
Q

What happens if we have a complete shunt in the capillary?

A

Ventilation maintained but perfusion is 0
V/Q = infinity. Called alveolar dead space
If partially blocked, there would be an increase in the V/Q

28
Q

What can cause shunting? (blood going through one lung/ part of the lung, but no gas transfer)

A

Physiological:
- Bronchial arteries
- Thesebian veins

Intracardiac (through a hole in heart):
- E.g VSD R-L Shunt

Pulmonary:
- ArterioVenous Malformation (AVM)
- Complete Lobar collapse

29
Q

What is Eisenmenger’s Sydrome?

A

Blood high in left ventricle
- Cyanosis (look blue)
- Clubbing (the soft tissue under nails gets bigger)
- Polycythaemia (lots of cells in blood)
- Erythrocytosis (body responds by creating lots of blood to maintain the O2 delivery)

30
Q

What is hypoxic pulmonary vasoconstriction?

A
  • All arteries narrow down (disadvantageous)
  • High pressure in right side
  • Aims to maintain V/Q
    Hypoxia helps by:
  • Redistributing arterial blood flow to areas still being ventilated
31
Q

What is a pulmonary embolism?

A
  • Often in the right leg: red and swollen
  • blood vessel in lung is blocked
  • DVT (deep vein thrombosis)
  • Clot in veins
32
Q

What is a lung infarction minor PE?

A
  • Pleuritic pain (sharp pain which is worse when breathing)
  • Peripheral arteries
33
Q

What is a central major PE (pulmonary embolism)?

A
  • Shock
  • Central Chest pain
  • Hypoxia
  • Risk of immediate mortality
34
Q

How is a V/Q scan performed?

A
  • Inject albumin
  • Breathe in radioactive gas
  • Compare the scans and if there is a significant difference then there is a V/Q mismatch
35
Q

What is Virchow’s Triad?

A

The more likely you have:
- Endothelial injury
- Hypercoagulable state
- Circulatory stasis
The more likely you are to develop thrombosis

CVR Lectures (28 decks)

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