Blood supply, gas exchange, ventilation & perfusion

Question 1

What does the bronchial circulation supply?

Answer 1

Supplies oxygenated blood via bronchial arteries from the systemic circulation to airway smooth muscle, nerves and lung tissue.

Question 2

Where do the Left and right pulmonary arteries arise from?

Answer 2

The right ventricle

Question 3

What does the Left and Right pulmonary artery carry?

Answer 3

Entire cardiac output from RV

Question 4

What does the pulmonary artery supply?

Answer 4

The dense capillary network surrounding the alveoli

Question 5

Where does the blood travel after the capillary network surrounding the alveoli?

Answer 5

Travels to the left atrium via the pulmonary vein

Question 6

How is the pulmonary circulation described?

Answer 6

High flow low pressure system.

Question 7

What is the partial pressure of Oxygen in the alveoli?

Answer 7

100mmHg

Question 8

What is the partial pressure of CO2 in the alveoli?

Answer 8

40 mmHg

Question 9

How does the air diffuse across the membranes between the alveoli and the blood circulation?

Answer 9

Diffusion across the partial pressure gradient

Question 10

What does A stand for?

Answer 10

Alveolar

Question 11

What does a stand for?

Answer 11

Arterial blood

Question 12

What does ṽ stand for?

Answer 12

Mixed venous blood (e.g pulmonary artery)

Question 13

What are the missing values from the table?

Answer 13

Question 14

What is the rate of diffusion across the membrane directly proportional to?

Answer 14

Partial pressure gradient

Gas solubility

Available surface area

Question 15

What is rate of diffusion across the membrane indirectly proportional to?

Answer 15

The thickness of the membrane

Question 16

When is the rate of diffusion of gas across the membrane most rapid?

Answer 16

Over short distances

Question 17

Look at this slide

Answer 17

Question 18

What is the surface area of an alveoli in emphysema?

Answer 18

Reduced surface area

Question 19

What are the features of Fibrotic lung disease?

Answer 19

Thickened alveolar membranes slows gas exchange. Loss of lung compliance may decrease alveolar ventilation.

Question 20

What are the features of pulmonary edema?

Answer 20

Fluid in interstitial space increases diffusion distance. Arterial pCO2 may remain normal due to higher solubility in water.

Question 21

Describe asthma

Answer 21

Increased airway resistance decreases airway ventilation

Question 22

Which picture represents fibrotic alveoli, normal alveoli and pulmonary oedema?

Answer 22

Fibrotic, normal, oedema

Question 23

What is ventilation linked to?

Answer 23

Perfusion - (local blood flow L/min)

Question 24

What is distribution of blood flow in the lung influenced by?

Answer 24

Hydrostatic pressure and alveolar pressure

Question 25

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

Answer 25

Arterial pressure exceeds alveolar pressure and vascular resistance is therefore low.

Question 26

Why is blood flow low at the at the apex of the lung? (in pulmonary capillaries?)

Answer 26

Arterial pressure is less than alveolar pressure. This compresses the arterioles and vascular resistance is increased.

Question 27

What is the optimal condition for ventilation?

Answer 27

Ventilation = blood flow

Question 28

Which of the mismatches has

1. Under oxygenated blood
2. Too much breathing taking place compared to the rate of blood flow

Answer 28

1. Mismatch 2
   
   1. Mismatch 1

Question 29

Where does majority of the mismatch take place?

Answer 29

Apex of the lung

Over 75% of the height the healthy lung performs quite well in matching blood and air

Question 30

What happens if ventilaiton decreases in a group of alveoli?

Answer 30

PCO2 increases and PO2 decreases. Blood flowing past those alveoli does not get oxygenated.

Question 31

What decreased PO2 around underventilated alveoli cause?

Answer 31

Constricts their arterioles, diverting their blood to better ventilated alveoli

Constriction in response to hypoxia is particular to pulmonary vessels (systemic vessels dilate)

Question 32

What does increased PCO2 cause?

Answer 32

Mild bronchdilation

Question 33

Ultimately this response increases perfusion and, to a lesser extent, decreases ventilation, bringing the ratio back towards 1.What happens when you get ventilation > blood flow?

Answer 33

Question 34

What is shunt?

Answer 34

Shunt is a term used to describe the passage of blood through areas of the lung that are poorly ventilated (ventilation << perfusion

Shunt is the opposite of alveolar dead space

Question 35

What are is alveolar dead space?

Answer 35

Alveolar Dead Space refers to alveoli that are ventilated but not perfused.

Question 36

What is anatomical dead space?

Answer 36

Anatomical Dead Space refers to air in the conducting zone of the respiratory tract unable to participate in gas exchange as walls of airways in this region (nasal cavities, trachea, bronchi and upper bronchioles) are too thick.

Question 37

What is physiological dead space?

Answer 37

Physiological Dead Space = Alveolar DS + Anatomical DS

Question 38

What does the low pressure circuit cause?

Answer 38

More susceptible to the effects of gravity and this gives rise to a great degree of variability in blood flow within the lung.

Question 39

Why are the overall rates of equilibrim between O2 and CO2 similar? Despite the fact CO2 is more soluble?

Answer 39

Because of the greater pressure difference for O2