Gas exchange and transfer

Question 1

What is anatomical dead space?

Answer 1

Space which does not partake in gas exchange due to anatomy - size of breath, posture, radii etc

Question 2

What is Physiological dead space?

Answer 2

Volume of gas in each breath which does not partake in gas exchange - includes anatomical and alveoli not perfused of damaged

Question 3

What are the key features of alveoli?

Answer 3

300M of them
70m^2 SA
1 cell thick
Extensive perfusion

Question 4

What are the partial pressures of O2 in different spaces?

Answer 4

PiO2 = 160mmHg
PAO2 = 100mmHg
PaO2 = 95mmHg
PvO2 = 40mmHg

Question 5

What are the partial pressures of CO2 in different spaces?

Answer 5

PvCO2 = 46mmHg
PACO2 = 40mmHg
PECO2 = 32mmHg

Question 6

What is Fick’s law?

Answer 6

Diffusion rate ~= (Alveolar SA/air-blood barrier thickness) x Pressure gradient x D

Question 7

What is the estimated volume of blood flow in the lung/min and volume of air in the lung/min?

Answer 7

Blood -6L/min

Air - 5L/min

Question 8

What is the ventilation:perfusion?

Answer 8

5: 6

0. 8:1

Question 9

What causes V:Q mismatch?

Answer 9

increase in physiological dead space due to alveolar damage, respiratory failure, perfusion occlusion, lack of O2 inspired

Question 10

What is Poiseulle’s law?

Answer 10

Flow ~= pressure difference x radius^4

Question 11

What are the normal ranges for an ABG for O2 and CO2?

Answer 11

O2 = 12-15kPa or 90-113mmHg
CO2 = 4.4-6.1kPa or 33-46mmHg