Blood supply, gas exchange and ventilation

Question 1

Where is the biggest compliance?

Answer 1

At the base of lungs

Question 2

Where is the greatest alveolar ventilation?

Answer 2

At the base of the heart

Question 3

What is called systemic circulation in the lungs?

Answer 3

Bronchial circulation, arise from systemic, forms bronchial arteries

Question 4

Describe pulmonary circulation

Answer 4

In series with heart, pulmonary artery arise from right ventricle, to lungs, pulmonary vein to left atrium

Question 5

Describe the pressure and flow in pulmonary circulation

Answer 5

High flow, low pressure circulation

Question 6

What is the systolic and diastolic pressure in pulmonary circulation ?

Answer 6

25 mmHg and 8 mmHg

Question 7

What is the gradient between the arteries and veins?

Answer 7

10 mmHg, very small gradient, only very small change can cause big disruption

Question 8

What is PAO2, PaO2, PvO2 ?

Answer 8

Partial pressure of O2 in alveoli, arteries and veins respectively

Question 9

What is PAO2 and PACO2?

Answer 9

100 mmHg (13.3 kPa) and 40 mmHg (5.3 kPa)

Question 10

What is PaO2 and PaCO2?

Answer 10

100 mmHg and 40 mmHg

Question 11

What is PvO2, PvCO2 ?

Answer 11

40 mmHg and 46 mmHg

Question 12

What affects diffusion?

Answer 12

It is directly proportional to partial pressure gradient, gas solubility, surface area, inversely proportional to the thickness of membrane and diffusion distance

Question 13

What is the gradient between partial pressure of O2 and CO2 ?

Answer 13

60 mmHg and 6 mmHg, O2 gradient is 10 times bigger

Question 14

What is the amount of O2 absorbed and CO2 excreted ?

Answer 14

250 ml of O2 and 200 ml of CO2 per minute

Question 15

What happens to partial pressure of O2 in emphysema?

Answer 15

PAO2 is normal or low, in blood PO2 is low

Question 16

What happens to partial pressure of O2 in lung fibrosis?

Answer 16

PAO2 is normal or low, in the blood is low

Question 17

What happens to partial pressure of O2 in pulmonary oedema?

Answer 17

PAO2 is normal, in blood low

Question 18

What happens to partial pressure of O2 in asthma?

Answer 18

PO2 is low both in alveoli and blood

Question 19

Describe blood flow at the base of lungs

Answer 19

Most of the blood at the base due to gravity, compromising the alveoli, the arterial pressure is bigger than alveolar pressure, low vascular resistance, the blood flow is bigger than ventilation.

Question 20

Describe the blood flow at the apex of lungs

Answer 20

Less blood than at the bottom, arterial pressure is less than alveolar, resistance is increased, ventilation is bigger than blood flow

Question 21

On what factors is blood flow dependent upon?

Answer 21

It depends on the resistance. the biggest resistance is at the apex of lungs as the hydrostatic pressure of arteries is lower that the alveolar pressure. Blood flow declines with heigh from the bottom

Question 22

Describe what is happening to the blood flow and ventilation from the base to the apex of lungs

Answer 22

Both blood flow and ventilation decrease from base to the apex, this is due to gravity. However, the rate of decline for blood flow is bigger and so at the top the ventilation is bigger than the blood flow.

Question 23

Where does the crossover over ventilation and blood flow happens ?

Answer 23

Over rib 3

Question 24

Describe the ventilation and perfusion ratio in the lungs

Answer 24

Rib 3 and below the ratio is very close to 1, it decreases slightly as the blood flow is bigger at the base. above rib 3 the ventilation/ perfusion ratio increases and is a lot bigger than 1, there is big mismatch

Question 25

What is mismatch ratio <1?

Answer 25

The perfusion is bigger than ventilation

Question 26

What is mismatch > 1?

Answer 26

The ventilation is bigger than perfusion

Question 27

Where does the majority of mismatch happen?

Answer 27

At the apex of lungs, 75% of lung performs well in terms of the ventilation/perfusion ratio

Question 28

Describe shunt

Answer 28

Hyperventilated alveoli, there is decrease in PO2 but increase in PCO2, this results is blood not being oxygenated, this blood than mixes with oxygenated blood and dilutes it

Question 29

How is the mismatch in shunt corrected (ventilation

Answer 29

The area where hypoxia is detected the vessels constrict directing blood to bettie ventilated alveoli, this is the opposite to the systemic circulation. The increase in PCO2 causes bronchial dilation

Question 30

When is ventilation > perfusion ?

Answer 30

In pulmonary embolism

Question 31

What is alveolar dead space?

Answer 31

Alveoli that are ventilated but not perfused

Question 32

What happens when the ventilation is bigger than perfusion?

Answer 32

The PO2 in increased, but the alveolar PCO2 is decreased, this causes dilation of blood vessels and constriction of bronchi, the end result is to increase perfusion and decrease ventilation

Question 33

What is physiological dead space?

Answer 33

It is the sum of anatomical and alveolar dead space

Question 34

What is anatomical dead space?

Answer 34

The air in conduction airways