Haemoglobin & Gas Transport

Question 1

How much arterial O2 is extracted by arterial tissues at rest?

Answer 1

25%

Question 2

What does the PaO2 determine?

Answer 2

The degree to which haemoglobin is saturated with oxygen

Question 3

How much oxygen binds to 1g of HbA?

Answer 3

1.34mL O2 (98% of oxygen in blood, 2% dissolved in plasma)

Question 4

What is the normal PaO2 and what does it determine?

Answer 4

100mmHg = ~100% haemoglobin saturation

Question 5

What is PO2 in resting cells?

Answer 5

40mmHg = 75% haemoglobin saturation

Question 6

Order the types of haemoglobin from highest affinity to lowest

Answer 6

Myoglobin, HbF, HbA (for extracting oxygen from maternal/arterial blood

Question 7

What happens to PaO2 in anaemia?

Answer 7

Normal (if total O2 content is low, it is still possible to have normal PaO2)

Question 8

Define anaemia

Answer 8

Any condition where the oxygen carrying capacity of the blood is compromised

Question 9

What is the affect of pH on oxygen affinity for haemoglobin?

Answer 9

Alkalosis (pH 7.8) = increases affinity
Acidosis (pH 7.2, exercising muscle) = decreases affinity
Increased pH = increases affinity

Question 10

What is the affect of PCO2 on oxygen affinity for haemoglobin?

Answer 10

Increased PCO2 = decreased oxygen affinity

Question 11

What is the affect of temp on oxygen affinity for haemoglobin?

Answer 11

Increased temp = decreased oxygen affinity

Question 12

What is the affect of [DPG] on oxygen affinity for haemoglobin?

Answer 12

Increased DPG = decreased oxygen affinity

Question 13

What is DPG?

Answer 13

2,3-diphosphoglycerate synthesised by erythrocytes. Increases in situations associated with inadequate oxygen supply 9 helps maintain oxygen release.

Question 14

How does carboxyhaemoglobin form?

Answer 14

CO has a greater affinity for haemoglobin than oxygen. At a pressure of 0.4mmHg causes progressive carboxyhaemoglobin formation.

Question 15

What are the symptoms of CO poisoning?

Answer 15

Hypoxia, anaemia, nausea, headaches, cherry red skin nd mucous membranes. Respiratory rate normal due to normal PCO2. Potential for brain damage and death

Question 16

What is Hypoxic Hypoxia?

Answer 16

Reduction in oxygen diffusion in the lungs due to decreased atmospheric oxygen or tissue pathology

Question 17

What is Anaemic Hypoxia?

Answer 17

Reduction in oxygen carrying capacity of the blood due to anaemia

Question 18

What is Ischaemic (stagnant) Hypoxia?

Answer 18

Heart disease resulting insufficient oxygen transport around body

Question 19

What is Histotoxic Hypoxia?

Answer 19

Poisoning prevents cells utilising oxygen delivered to them

Question 20

What is Metabolic Hypoxia?

Answer 20

Oxygen delivery to dishes does not meet oxygen demand

Question 21

Describe carbon dioxide transport in the blood

Answer 21

• 7% remains dissolved in plasma and erythrocytes.
• 23% combines in the erythrocytes with deoxyhaemoglobin to form carbamino compounds.
• 70% combines in the erythrocytes with water to form carbonic acid, which dissociates to yield bicarbonate and hydrogen ions.

Question 22

What happens to bicarbonate?

Answer 22

Moves out of erythrocytes into plasma in exchange for chlorine ions and excess hydrogen ions bind to deoxyhemoglobin. Reverse occurs in pulmonary capillaries and CO2 moves down conc. gradient from blood to alveoli.

Question 23

What does hypoventilation cause?

Answer 23

Causes CO2 retention = decreases pH = respiratory acidosis

Question 24

What does hyperventilation cause?

Answer 24

Expelling more CO2 = increases pH = respiratory alkalosis