Pulmonary blood flow gas exchange and transport

Question 1

What change occurs to alveolar ventilation with height from base to apex?

Answer 1

It declines

Question 2

What change occurs to compliance with height from base to apex?

Answer 2

It declines

Question 3

Where does exchange I occur?

Answer 3

Between atmosphere and lungs

Question 4

Where does exchange II occur?

Answer 4

Between lung and blood

Question 5

Where does exchange III occur?

Answer 5

Between blood and cells

Question 6

How is Bronchial circulation (nutritive) supplied?

Answer 6

It is supplied via the bronchial arteries arsing from systemic circulation to supply oxygenated blood to airway smooth muscle, nerves and lung tissue.

Question 7

How is pulmonary circulation (gas exchange) supplied?

Answer 7

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

Question 8

How does air move across membranes?

Answer 8

Air diffuses across membranes down partial pressure gradient.

Question 9

What are alveoli composed of?

Answer 9

• Type I cells for gas exchange
• Type II cells that synthesise surfactant

Alveolar macrophages ingest foreign material that reaches the alveoli.

Question 10

Effect of Emphysema

Answer 10

Destruction of alveoli reduces surface area for gas exchange.

-Emphysema usually caused by smoking

Question 11

Effect of Fibrotic lung disease

Answer 11

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

Question 12

Effect of Pulmonary edema

Answer 12

Fluid in interstitial space increases diffusion distance. Arterial PCO2 may be normal due to higher CO2 solubility in water.

Question 13

Effect of Asthma

Answer 13

Increased airway resistance decreases airway ventilation.

Question 14

How do ventilation and perfusion affect each other?

Answer 14

Ventilation and perfusion ideally match (compliment) each other.
Ventilation in alveoli is matched to perfusion through pulmonary capillaries.

Question 15

Why is blood flow higher than ventilation at the base of the lungs?

Answer 15

Arterial pressure exceeds alveolar pressure. This compresses the alveoli.

Question 16

What is Shunt?

Answer 16

Term used to describe the passage of blood through areas of the lung that are poorly ventilated.
-Shunt is the opposite of alveolar dead space.

Question 17

Pulmonary vasodilation

Answer 17

Increase in alveolar PO2

Question 18

Mild bronchial constriction

Answer 18

Decrease in alveolar PCO2

Question 19

Alveolar dead space

Answer 19

Refers to alveoli that are ventilated but not perfused.

Question 20

Anatomical dead space

Answer 20

Refers to air in the conducting zone of the respiratory tract unable to participate in gas exchange as walls of airways in this region are too thick.

Question 21

Physiologic dead space

Answer 21

PDS = Alveolar DS + Anatomical DS

Question 22

How much does Haemoglobin in red blood cells increase O2 carrying capacity?

Answer 22

It increases the O2 carrying capacity to 200ml/L.

Question 23

Is arterial partial pressure of O2 (paO2) the same as arterial O2 concentration/content?

Answer 23

NO
-PaO2 refers purely to O2 in solution and is determined by O2 solubility and the partial pressure of O2 in the gaseous phase that is driving O2 into solution.

Question 24

Why do gases not travel in the gaseous phase in plasma?

Answer 24

If they did = bubbles in blood = fatal air embolism

Question 25

What is the major determinant of the degree to which haemoglobin is saturated with oxygen?

Answer 25

Partial pressure of oxygen in arterial blood

Question 26

How long does it take saturation to complete after contact with alveoli?

Answer 26

After 0.25s contact with alveoli (0.75s total contact time)

Question 27

What is the most efficient PO2 to maximise haemoglobin oxygen load?

Answer 27

100 mm Hg

Question 28

What is Anaemia?

Answer 28

Any condition where the oxygen carrying capacity of the blood is compromised (e.g. iron deficiency, haemorrhage, vit B12 deficiency).

Question 29

What chemical factors affect the affinity of haemoglobin for O2?

Answer 29

• pH
• PCO2
• Temperature
• DPG conc (diphosphoglycerate)

Question 30

What increase in chemical factors decrease the affinity of haemoglobin for O2?

Answer 30

-PCO2 and temperature

Decrease in pH decreases affinity for O2.

Question 31

What is formed when Carbon Monoxide binds to haemoglobin?

Answer 31

Carboxyhaemoglobin

-This has an affinity 250 times greater than O2.

Question 32

What are the 5 main types of hypoxia?

Answer 32

1. Hypoxaemic Hypoxia (most common)
2. Anaemic Hypoxia
3. Stagnant Hypoxia
4. Histotoxic Hypoxia
5. Metabolic Hypoxia

Question 33

Hypoxaemic Hypoxia

Answer 33

Reduction in O2 diffusion at lungs either due to decreased PO2atmos or tissue pathology.

Question 34

Anaemic Hypoxia

Answer 34

Reduction in O2 carrying capacity of blood due to anaemia (red blood cell loss/iron deficiency)

Question 35

Stagnant Hypoxia

Answer 35

Heart disease results in inefficient pumping of blood to lungs/around the body.

Question 36

Histotoxic Hypoxia

Answer 36

Poisoning prevents cells utilising oxygen delivered to them e.g. CO/cyanide.

Question 37

Metabolic Hypoxia

Answer 37

Oxygen delivery to the tissues does not meet increased oxygen demand by cells.

Question 38

What is a erythrocyte?

Answer 38

A red blood cell, which (in humans) is typically a biconcave disc without a nucleus
-Erythrocytes contain haemoglobin

Question 39

Normally, why is pH stable in ECF?

Answer 39

Because all CO2 produced is eliminated in expired air.

-However hypo/hyperventilation will affect this.

Question 40

What does hypoventilation cause?

Answer 40

Causes CO2 retention, leading to increased (H+) bringing about respiratory acidosis!!

Question 41

What does Hyperventilation cause?

Answer 41

Causes more CO2 loss, leading to decreased (H+) bringing about respiratory alkalosis.