VIX: Gas Exchange Flashcards
Definition of diffusion
Random movement of particles from a place of high concentration to a place of low concentration
In the higher concentration section is there more or less energy
More
Definition of net motion
Difference between tendency to move in one direction and tendency to move in the opposite
Composition of air, N2
78%, 600mmHg
Composition of air, O2
21%, 160mmHg
Composition of air, NOBLE GASES
1%
Atmospheric/barometric pressure equals to the
Sum of partial pressures of gases
What does partial pressure of a gas depend on
On its concentration and solubility coefficient
What does diffusion depend on
Area and thickness of membrane
HENRY’S LAW is used to calculate
Partial pressure
What do you need to know to calculate partial pressure of a gas using Henry’s law
The concentration of the other components in the air
HENRY’S LAW,
Partial pressure = [Dissolved gas] / solubitlity coefficient
Solubility coefficient of O2
0.024
Coefficient solubility CO2
0.57
Coefficient solubility CO
0.018
From less to most, solubility coefficient of O2, CO2, CO
CO, O2, CO2
Therefore, is CO2 is 20x more soluble than O2, how is are the pO2, pCO2 related
PCO2 will be 20x less than PO2
This is because according to Henry’s law, a greater solubility coefficient will lead to a smaller partial pressure. Therefore since the solubility coefficient of CO2 is 20x more than for O2, that will mean that the PCO2 is 20x less than for PO2
Relationship between inflow/outflow of a gas into alveolar space/blood and partial pressure of the gas
DIRECTLY PROPORTIONAL
Gas diffusion direction depends on
Differences in gas partial pressures between the 2 systems
Time it takes for erythrocyte to travel capillary surrounding an alveolus is
0.75s
Alveolar PO2, PCO2
PO2 - 105mmHg
PCO2 - 40mmHg
In deoxeginated blood, PCO2 and PO2
PO2 - 40mmHg
PCO2 - 45mmHg
Why does gas exchange take place
Because of the differences in partial pressure
Relationship between alveolar membrane thickness and gas diffusion
INVERSERLY PROPORTIONAL
So an increase in thickness of alveolar membrane will lead to a decreased gas exchange and viceversa
Relationship between alveolar membrane surface area and gas diffusion
DIRECTLY PROPORTIONAL
Relationship between gas diffusion coefficient and gas exchange
DIRECTLY PROPORTIONAL
Relationship between pressure gradient and gas diffusion
DIRECTLY PROPORTIONAL
Relationship between contact time and gas exchange
DIRECTLY PROPORTIONAL
Interstitial edema, COPD, pneumonia, pulmonary fibrosis are examples of
Increased alveolar membrane thickness resulting in DECREASED RATE OF DIFFUSION
Pulmonary emphysema (smoking) is an example of
Reduced surface area resulting in DECREASED GAS EXCHANGE RATE
Ficks law
Vgas = [(P1-P2)/X] x A x D
P1-P2 is the pressure gradient
A is area
X is thickness
D is diffusion coefficient
