O2 and CO2 exchange

Question 1

Measure of ventilation

Answer 1

Respiratory minute volume = Tidal volume + Respiratory rate

Ve = Vt + f

Question 2

Typical ventilation rate

Answer 2

6L/min

Question 3

What is dead space?

Answer 3

The amount of space that air occupies in the respiratory system that do not contribute to GE

Question 4

What is Dead space denoted by?

Answer 4

Vd and it is about 150ml

Question 5

Alveolar ventilation rate equation

Answer 5

(Vt - Vd) x f

Question 6

Why are tiny breaths not helpful?

Answer 6

The air may not reach the GE surfaces i.e the alveoli

Question 7

Dalton’s law

Answer 7

• In a gas mixture (air), each gas exerts its own individual
  pressure, called a partial pressure (P)

-The pressure of a mixture of gases = the sum total of the
pressures of each individual gas

Question 8

What happens to the PP of O2 as it moves from Atm to the alveoli

Answer 8

Decreases due to diffusion

Question 9

What does the air become saturated with as we breathe?

Answer 9

H2o vap

Question 10

PP of O2 in the atm(tot)

Answer 10

160mmHg

Question 11

Why do gases move across the membrane?

Answer 11

It is wet in the alveoli
- The gases have a tendency to dissolve in solution but they still have a PP

• Gases keep dissolving until the PP of O2 is at equilibrium

Question 12

Fick’s law of diffusion

Answer 12

Gases move across the membranes
between the alveoli and the capillaries by diffusion

Question 13

What determines the rate of diffusion?

Answer 13

• Surface area of the membranes
• Thickness of the membranes
• Pressure difference between the
  two sides

Question 14

Equation of Fick’s law

Answer 14

F = (A/T) x D x (P1-P2)
F = Flux (Amount flowing)
A = surface area
T = thickness
D = Diffusion constant
P1-P2 = pressure difference

Question 15

What is D

Answer 15

Diffusion constant or coefficient for substance depends on gas solubility (S) and its molecular weight

Question 16

Emphysema

Answer 16

disease characterized by dilation of the alveolar spaces and destruction of the alveolar walls

Question 17

What is the main factor of GE

Answer 17

Pressure difference

Question 18

PAO2 depends on

Answer 18

1. Partial pressure of oxygen in
   inspired air (almost negligible as most ppl are at sea level)
2. Alveolar ventilation (rate of breathing)
3. Oxygen consumption – Blood
   oxygen

Question 19

What is O2 consumption in the body?

Answer 19

Our metabolism i.e how much O2 end up in our venous blood that drive the diffusion gradient of O2 in the lungs

Question 20

PACO2 depends on

Answer 20

1. Partial pressure of CO2 in
   inspired air
2. Alveolar ventilation
3. Carbon dioxide production