L8 Blood Gas Exchange

Question 1

How do you measure the partial pressure of teach component in air?

Answer 1

Multiply it’s percentage by 760 mmHg (atmospheric pressure).

e.g. O2 is 21% of air. Therefore,

PO2 = 0.21 x 760 = 159.5 mmHg

Question 2

What is Henry’s Law?

Answer 2

Gases dissolve into liquids until the reach equilibrium.

Dissolved gas conc. = partial pressure of gas x solubility coefficient

Question 3

What is the solubility coefficient of oxygen in water?

Answer 3

0.024

Question 4

What is the solubility coefficient of carbon dioxide in water?

Answer 4

0.57

Question 5

Which is more soluble in water?

A) Carbon Dioxide
B) Oxygen
C) Nitrogen
D) Equally soluble in water

Answer 5

A) Carbon Dioxide

With relation to Henry’s Law, the solubility coefficient of CO2 in water is 0.57, while O2’s is 0.024. Therefore, CO2 is much more soluble in water than O2 is.

Nitrogen’s solubility coefficient in water is about half that of oxygen.

Question 6

What causes nitrogen narcosis?

Answer 6

Respiring in a high-pressure environment (like an exam?) induces nitrogen diffusion across the respiratory membrane.

E.g. the deeper divers go the greater the partial pressure of nitrogen = more diffusion = nitrogen narcosis

Question 7

What are the symptoms of decompression sickness?

Answer 7

Joint pain, dizziness, SOB, fatigue, paralysis, loss of consciousness.

Question 8

What causes decompression sickness?

Answer 8

Rapid decrease in pressure (decompression) can cause dissolved gases to come out of solution. They can form bubbles in tissues which cause the symptoms.

Question 9

What conditions can you treat with hyperbaric oxygenation?

Answer 9

Infections caused by anaerobes, like the bacteria that cause gangrene and tetanus.

Carbon monoxide poisoning

Gas embolisms (decompression sickness)

Bone infections

Smoke inhalation

Near drowning

Circulatory problems

Question 10

Starting in the alveolus, what route is taken by an O2 molecule as it diffuses across the respiratory membrane into the capillary?

Answer 10

Alveoli

Thin layer of fluid

Squamous epithelial cells of the alveoli

Epithelial basement

Interstitial space

Basement membrane of the capillary endothelium

Capillary endothelium

Lumen of capillary

Question 11

What factors affect the diffusion of gases across the respiratory membrane?

A) The thickness of the membrane
B) The diffusion coefficient
C) The surface area
D) The partial pressure difference across the membrane
E) All of the above

Answer 11

E) All of the above

Diffusion of gases across the respiratory membrane depends on:

• The thickness of the membrane
• The diffusion coefficient
• The surface area
• The partial pressure difference across the membrane

Question 12

How can the body manipulate the partial pressures in the alveoli?

Answer 12

Hyperventilation will flush out the CO2, drawing more CO2 out of the blood.

Depressed respiration will allow CO2 to build up in the alveoli and therefore, blood CO2 levels will rise.

Question 13

What is the physiological shunt?

Answer 13

too much of the blood supplying the lung tissues via the bronchial arteries is being returned via the pulmonary veins without undergoing gas exchange.

This means blood is not sufficiently saturated with O2.

Occurs when blood supply exceeds ventilation rate.

Question 14

True or false: A standing person at rest will usually ventilate using the upper portion of the lungs.

Answer 14

True.

PO2 within the alveoli of the upper part of the lungs will drop and PCO2 within the alveoli will rise. Causes vasoconstriction of arterioles supplying the affected alveoli with deoxygenated blood, which in turn decrease the flow of blood to these regions.