Respiratory Physiology 3

Question 1

Describe the principle of gas diffusion

Answer 1

High concentration to low concentration

Question 2

Describe the normal ranges of PAO2, PaO2 and PvO2

Answer 2

PaO2 = arterial blood oxygen partial pressure
(40)

PAO2 - partial pressure oxygen in alveoli
(104)

PvO2 - partial pressure of oxygen in mixed venous blood
(100)

the rate of diffusion is based on the difference in pp and rate in which the alveolar air is replaced.
Eg when there is less O2 in the blood at the arterial end, the rate of diffusion will be higher

Question 3

Describe the normal ranges of PaCO2, PACO2 and PvCO2

Answer 3

PaCO2 = 45

PACOs = 40

PcCO2 = 40

However solubility of CO2 is around 20x of oxygen in both blood and alveolar fluid means that the rate of diffusion is quite similar

Question 4

Explain the modes of O2 transport

Answer 4

Dissolved

Bound to Hb

Question 5

Describe the structure of haemoglobin

Answer 5

4 subunits, each subunit is bound to a heme molecule

Question 6

Describe the relationship between oxygen affinity and oxygen binding sites of haemoglobin

Answer 6

Each O2 molecule that is bound to the Hb results in a conformational change which makes the subsequent O2 binding easier. Hb now has a higher affinity to bind to O2 molecules after each O2 bound. The same in reverse.

Question 7

Explain the oxygen- haemoglobin dissociation curve

Answer 7

Question 8

Explain the conditions associated with right and left shift of the oxygen-haemoglobin dissociation curve and describe the impact this has on offloading oxygen at peripheral tissues

Answer 8

Shifting to the left or the right is based on the P50
Left = O2 binds easier to Hb, but less dissociates at the periphery tissues

Temperature increases = righter
PCO2 increased amount = right
pH decrease = right
Increase of DPG (increase in blood metabolism = righter

Question 9

Describe the modes of CO2 transport and role of bicarbonate

Answer 9

Dissolved
CO2 solubility
5-7%

Bound to Hb
- 5-23%
Related to 2 content
Hb Binding ( CO2 binds to the Hb molecule)

In form of HCO3-
carbonic anhydrase
RBC involvement
70-90%

Question 10

Describe the CO2 and Hb dissociation curve

Answer 10

Question 11

Compare the O2 and CO2 hb dissociation curves

Answer 11

CO2 is higher partial pressure in the tissue not the lungs like O2

Amount of O2 bound to Hb impacts on binding of CO2. The lower the partial pressure of O2 ( the less O2 bound) the more CO2 can be bound

Dissociation curve is linear, not sigmoid shape like the O2 curve

Pressure of CO2 in blood = 40-45mmHg