Respiratory Physiology Lecture 4: Gas Transport in the Blood – Part 1

Question 1

What order of oxygen partial pressure from highest to lowest is the Gas, tissues, Arterial, air, pulmonary capillary.

Answer 1

Air(atmosphere), gas,(slightly less) pulmonary capillary, (slightly less) arterial, tissues.

Question 2

What is the symbols used for oxygen partial pressures?

Answer 2

P(small O2) kPa

Question 3

What is Henry’s law?

Answer 3

The amount of a given gas dissolve in a given type and volume of liquid at a constant temp is proportional to the partial pressure of the gas in equilibrium.

Question 4

What is the partial pressure of a gas in solution?

Answer 4

The partial pressure of the gas in the mixture with which it is in equilibrium.

Question 5

How does dissolved oxygen in the blood fit into Henry’s law?

Answer 5

The O2 amount dissolves in blood is proportional to the partial pressure.

Question 6

How much dissolved O2 per litre of blood is at a P02 of 13.3 kPa?

Answer 6

3ml

Question 7

How much dissolved O2 is taken to tissues at resting conditions on average?

Answer 7

15ml/min

Question 8

How much dissolved O2 is taken to tissues at strenuous exercise in a average person?

Answer 8

90ml/min

Question 9

How much O2 consumption at rest on a average person?

Answer 9

250ml/min way too much for just dissolved oxygen!!

Question 10

During strenuous exercise how much oxygen is consumed compared to resting?

Answer 10

up to 25 times!

Question 11

What other mechanism is involved in O2 transport in the blood other than dissolved oxygen?

Answer 11

Haemoglobin

Question 12

Normal O2 concentration in the blood is what? and what is the normal haemoglobin (Hb) concentration?

Answer 12

200ml per L of O2 and 150g of Hb per L

Question 13

What are the percentages of O2 carried bound to haemoglobin and in dissolved form?

Answer 13

Haemoglobin is 98.5% while dissolved oxygen is 1.5%.

Question 14

What does Hb do?

Answer 14

It can form a reversible combination with oxygen.

Question 15

What is Hb made from?

Answer 15

4 haem groups

Question 16

When is haemoglobin considered fully saturated?

Answer 16

When all Hb present is carrying its maximum oxygen load.

Question 17

What is the primary factor which determins the percent saturation of Hb with O2?

Answer 17

P(small O2)

Question 18

What is the average resting P02 of blood at systemic capillaries?

Answer 18

5.3 kpa

Question 19

What is the normal PO2 at pulmonary capillaries?

Answer 19

13.3

Question 20

What happens to the Hb saturation when Hb concentration increases?

Answer 20

Nothing!

Question 21

What is the oxygen delivery index?

Answer 21

An equation that tells how much oxygen is being delivered to tissue.

Oxygen delivery index (DO2L)=Oxygen content of arterial blood (CaO2) times by cardiac index (Cl)

Question 22

In the oxygen delivery index, what is the units for each bit?

Answer 22

DO2l - ml/min/metre(squared)
CaO2 - ml/L
Cl - L/min/metre(squared)

Question 23

What is the cardiac index?

Answer 23

The cardiac output in relation to the body surface area.

Question 24

How is the O2 content of the arterial blood (CaO2) determined?

Answer 24

CaO2=1.34 times by concentration of Hb times by SaO2.

The 1.34 comes from how much O2 1 gram of Hb can carry when fully saturated.

Question 25

What 3 things can impare oxygen delivery to the tissues?

Answer 25

Respiratory disease, heart failure, or anaemia.

Question 26

What happens to the atmospheric pressure when altitude increases?

Answer 26

It decreases.

Question 27

How do you find out the partial pressure of oxygen in the alveolar air?

Answer 27

PAO2 (partial pressure of O2 in alveolar air) = PiO (Partial pressure of O2 in inspired air) take away the (PaC2/0.8)

Question 28

What is the 0.8 in the partial pressure of oxygen in the alveolar air equation?

Answer 28

The respiratory exchange rate - ratio of CO2 produced/02 consumed in a person with a mixed diet

Question 29

How does Respiratory disease impair oxygen delivery to the tissues?

Answer 29

These can decrease aterial PO2 and hence decrease Gb saturation with O2 and O2 content of the blood.

Question 30

How does Anaemia impair oxygen delivery to the tissues?

Answer 30

This decreases Hb concentration and hence decreases O2 content of the blood.

Question 31

How does heart failure impair oxygen delivery to the tissues?

Answer 31

This decreases cardiac output.

Question 32

What does the binding of one O2 to Hb do?

Answer 32

Co-operativity - increases the affinity for Hb for O2 on other haem molecules

Question 33

What pattern is the increasing blood P02 have on the percentage of haemoglobin saturation? what is this significance?

Answer 33

A sigmoid - This has a flat upper portion which means that moderate fall in alveolar PO2 will not affect oxygen loading much. - The steep lower part means that the peripheral tissue gets a lot of oxygen from a small drop in capillary PO2.

Question 34

What is the Bohr effect?

Answer 34

This is the shift of the curve to the right in the sigmoid for Hb saturation and P02.

Question 35

What does the Bohr effect cause?

Answer 35

An increase in PCO2, H+ CONC, temp, 2,3-biphosphoglycerate.

Question 36

What is foetal haemoglobin?

Answer 36

Haemoglobin used in the stage of a foetus (and a few months after birth). It has 2 alpha and 2 gamma subunits while adult haemoglobin has two alpha and two beta subunits.

Question 37

How does feotal haemoglobin function differently from adult?

Answer 37

It interacts less with 2,3-biphosphoglycerate in red blood cells and so has a higher affinity. This means the O2-Hb dissociation curve is shifted to the left and so allows O2 to transfer from mother to feotus even if the PO2 is low.

Question 38

What is myoglobin?

Answer 38

This is present in skeletal and cardiac muscle to act as a storage of O2 for anaerobic conditions. It also fully saturates very quickly.

Question 39

What is the structure of myoglobin?

Answer 39

It is a single haem group per myoglobin and so no cooperativity binding of O2.

Question 40

What does myoglobin in the blood indicate?

Answer 40

Muscle damage.