Pulmonary Blood Flow, Gas Exchange And Transport

Question 1

Describe bronchial circulation

Answer 1

Supplied via the bronchial arteries

Arises from systemic circulation to supply oxygenated blood to airway smooth muscle, nerves and lung tissue

Question 2

Describe pulmonary circulation

Answer 2

Consists of L & R pulmonary arteries originating from the right ventricle.

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

Question 3

Describe pulmonary circulation system in terms of flow and pressure

Answer 3

High flow

Low pressure

Question 4

What is PaO2 the abbreviation for?

Answer 4

Partial pressure of oxygen in arterial blood

Question 5

What is PACO2 the abbreviation of?

Answer 5

Partial pressure of carbon dioxide in alveolar air

Question 6

State the partial pressure gradient for O2

Answer 6

PO2 = 100 mmHg in alveoli, moves down pp gradient to PO2 = 40 mmHg in arterial blood

Question 7

State the partial pressure gradient for CO2

Answer 7

PCO2 = 46 mmHg in arterial blood and moves down pp gradient to PCO2 = 40 mmHg in the alveoli

Question 8

State the proportions of the rate of diffusion across the membrane

Answer 8

• directly proportional to the partial pressure gradient
• Directly proportional to gas solubility
• Directly proportional to the available surface area
• inversely proportional to the thickness of the membrane
• most rapid over short distances

Question 9

What is emphysema?

Answer 9

Destruction of the alveoli which reduces surface area for gas exchange

Question 10

State the alveolar and arterial PO2 in emphysema

Answer 10

PAO2 - normal or low

PaO2 - low

Question 11

Describe fibrotic lung disease

Answer 11

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

Question 12

State the alveolar and arterial PO2 in fibrotic lung disease

Answer 12

PAO2 - normal or low

PaO2 - low

Question 13

Describe pulmonary oedema

Answer 13

Fluid in interstitial space increases diffusion distance

Question 14

State the alveolar and arterial PO2 in pulmonary oedema, and the effect of diffusion distance

Answer 14

PAO2 - normal
PaO2 - low
Diffusion distance - increased

Question 15

Describe asthma

Answer 15

Increased airway resistance, decreases airway ventilation

Question 16

State the alveolar and arterial PO2 in asthma

Answer 16

PAO2 - low

PaO2 - low

Question 17

Define ventilation

Answer 17

Air getting to the alveoli L/min

Question 18

Define perfusion

Answer 18

Local blood flow L/min

Question 19

Describe the optimal relationship between ventilation and perfusion

Answer 19

Ventilation = blood flow

Question 20

Describe the factors that influence the distribution of blood flow in the lung

Answer 20

Hydrostatic (blood pressure)

Alveolar pressure

Question 21

Describe blood flow in the base of the lung

Answer 21

Blood flow is high because arterial pressure exceeds alveolar pressure and vascular resistance is therefore low

Question 22

Describe blood flow at the apex of the lung

Answer 22

Blood flow is low because arterial pressure is less than alveolar pressure, compressing the Arteriolar and vascular resistance is increased

Question 23

Describe how the ratio of ventialtion to perfusion can be changed

Answer 23

When in the upright position, the V/Q ration changes front he base to the apex due to gravity

Question 24

State the ratio of perfectly matched V/Q

Answer 24

Ventilation: perfusion = 1.0

Question 25

State the ratio in mismatch 1 V/Q

Answer 25

Ventilation > perfusion ratio > 1.0

Question 26

State the ratio in mismatch 2 V/Q

Answer 26

Ventilation < perfusion < 1.0

Question 27

Where does the majority of mismatch take place?

Answer 27

In the apex

Question 28

Define shunt

Answer 28

Opposite to alveolar dead space

Passage of blood through areas of the lung that are poorly ventilated

Alveoli are ventilated but not perfused

Question 29

Describe the control mechanisms stimulated when ‘shunt’ occurs

Answer 29

Tissue PO2 is decreased around underventilated alveoli which constricts their arterioles, diverting blood to better-ventilated alveoli

Question 30

Describe alveolar dead space

Answer 30

Opposite to shunt

Alveoli that are ventilated but not perfused

Question 31

Define anatomical dead space

Answer 31

Air in the conducting zone of the respiratory tract which is unable to participate in gas exchange as walls are too thick

Question 32

Define physiological dead space

Answer 32

Alveolar dead space + anatomical dead space