Blood supply, gas exchange, ventilation & perfusion

Question 1

What pulmonary blood vessel travels away from the heart? what does it carry?

Answer 1

Pulmonary artery - CO2 to the lungs

Question 2

What pulmonary blood vessel travels towards the heart? What does it carry

Answer 2

O2 from the lungs to be pumped to the systematic circulation

Question 3

What circulation delivers oxygenated blood to airway smooth muscle, nerves and lung tissue?

Answer 3

Bronchial circulation (nutritive)

Question 4

What is the bronchial circulation supplied by?

Answer 4

The bronchial arteries that arise from the systematic circulation

Question 5

The entire cardiac output from the right ventricle is carried by what circulation

Answer 5

Pulmonary circulation (gas exchange)

Question 6

What does the pulmonary circulation consist of?

Answer 6

Left and right pulmonary arteries

Question 7

What does the pulmonary circulation supply/do?

Answer 7

The dense capillary network surrounding the alveoli and returns oxygenated blood to the left atrium via the pulmonary vein

Question 8

Is the pulmonary circulation a high or low flow and pressure

Answer 8

High flow, low pressure

Question 9

What gradients drive gas exchange?

Answer 9

Partial pressure gradients

Question 10

What do these abbreviations stand for: A a ṽ in relation to blood?

Answer 10

A - alveolar
a - arterial blood
ṽ - mixed venous blood

Question 11

What kind of membrane do gases move across?

Answer 11

Permeable

Question 12

The rate of diffusion across the membrane is directly proportional to what?

Answer 12

The partial pressure gradient (similar to conc. gradient)
The gas solubility
The available surface area

Question 13

The rate of diffusion across the membrane is inversely proportional to what?

Answer 13

The thickness of the membrane

Question 14

When is diffusion most rapid?

Answer 14

Over short distances

Question 15

What is more soluble in water, carbon dioxide or oxygen?

Answer 15

Carbon Dioxide

Question 16

What do systolic/diastolic mean?

Answer 16

Systolic - max blood presssure when the heart is contracted

Diastolic - min blood pressure when the heart is relaxed

Question 17

What are the normal systolic pressures?

Answer 17

Pulmonary systolic pressure = 25mmHg

Systemic systolic pressure = 120mmHg

Question 18

Whats the diference between the pressure of the pulmonary vein and artery that causes blood to flow? And why is it clinically important?

Answer 18

About 10mmHg as it is small it only takes a little patholgy to disrupt the blood flow. (Systemic is normally 100mmHg)

Question 19

What happens in emphysema?

Answer 19

The destruction of the alveoli reduces surface area for gas exchange

Question 20

In Emphysema, what are the values of Alveolar PO2 and Capillary PO2 relative to normal values?

Answer 20

Alveolar PO2 – normal or low Capillary PO2 –low

Question 21

What happens in fibrotic lung disease?

Answer 21

The alveolar membrane thickens which slows don gas exchange

Also the loss of lung compliance may decrease alveolar ventilation

Question 22

In Fibrotic Lung Disease, what are the values of Alveolar PO2 and Capillary PO2 relative to normal values?

Answer 22

Alveolar PO2 – normal or low Capillary PO2 – low

Question 23

What happens in a pulmonary oedema

Answer 23

The fluid in the interstitial space increases which causes the diffusion space to increase in distance

Question 24

In Pulmonary Oedema, what are the values of Alveolar PO2 and Capillary PO2 relative to normal values?

Answer 24

Alveolar PO2 – normal Capillary PO2 –low

Question 25

In a pulmonary Oedema, why might arterial PCO2 remain normal?

Answer 25

CO2 has a higher solubility in water

Question 26

How does asthma affect gas exchange?

Answer 26

Bronchioles constrict which increases airway resistance which decreases airway ventilation

Question 27

In asthma, what are the values of Alveolar PO2 and Capillary PO2 relative to normal values?

Answer 27

Alveolar PO2 – low | Capillary PO2 –low

Question 28

What pressures influence the distribution of blood flow in the lungs?

Answer 28

Hydrostatic blood pressure and alveolar pressure

Question 29

What is blood flow inversely proportional to?

Answer 29

Vascular resistance

Question 30

At the base of the lungs, blood flow is BLANK because?

Answer 30

High because arterial pressure exceeds alveolar pressure and vascular resistance is therefore low.

Question 31

At the apex of the lungs, blood flow is BLANK because?

Answer 31

Low because arterial pressure is less than alveolar pressure. This compresses the arterioles and vascular resistance is increased.

Question 32

When arterial pressure is less than alveolar pressure, blood flow will be

Answer 32

Reduced

Question 33

There is a mismatch in Ventilation:Perfusion when the ratio is

Answer 33

Greater or lower than 1.0

Question 34

If ventilation decreases in a group of alveoli, what effect will this have on PCO2 and PO2?

Answer 34

PCO2 - increases | PO2 - decreases

Question 35

What is "shunt"?

Answer 35

The passage of blood flow through areas of the lung that are poorly ventilated

Question 36

What effect is there on arterioles when there is decreased tissue PO2 around under-ventilated alveoli?

Answer 36

Arterioles will constrict to divert blood to better ventilated alveoli

Question 37

Constriction in response to hypoxia is particular to what vessels?

Answer 37

Pulmonary vessels only | The systematic vessels dilate

Question 38

Alveolar dead space is...

Answer 38

Alveoli that are ventilated but not perfused, opposite to a shunt

Question 39

What happens to alveolar partial pressures during alveolar dead space?

Answer 39

PA O2 increases | PA CO2 decreases

Question 40

What does a PA O2 increase lead to in alveolar dead space?

Answer 40

Pulmonary vasodilation

Question 41

What does a PA CO2 decrease lead to in alveolar dead space?

Answer 41

Bronchial constriction

Question 42

What is the purpose of these two responses?

Answer 42

To increase perfusion and to a lesser extent decrease ventilation, bringing the ratio back towards 1

Question 43

Physiological Dead Space is...

Answer 43

The alveolar dead space + anatomical dead space