PSC1002/L16 Gas Exchange Flashcards
Define ventilation.
The exchange of air between the atmosphere and lungs
Define alveolar ventilation.
The movement of air in and out of alveoli
Define anatomic dead space.
Volume of the conducting airways
Define physiologic dead space.
Anatomic dead space & alveolar dead space
Define alveolar dead space.
In unhealthy or elderly people, not all alveoli function properly
I.e., they are insufficiently perfused and not all O2 and CO2 is exchanged
Define pulmonary ventilation with an equation.
TPV = ventilation rate x tidal volume
What is movement of gas directly proportional to? (3)
Pressure gradient of gas
Solubility of gas in liquid
Temperature
Define Dalton’s Law.
The total pressure exerted by a mixture of gases is equal to the sum of the pressure exerted by the individual gases
How does the composition of alveolar air compare to air at sea level? (4)
Little change in N2
Decreased O2
Increased CO2
Increased H2O
Define Henry’s Law.
At constant temperature, the amount of a gas that dissolves in a liquid depends on the solubility of the gas in the liquid and the partial pressure of the gas.
At identical partial pressures, how much more CO2 would be dissolved than O2?
20x
Give 2 characteristics of pulmonary circulation.
Low pressure system
High flow
What is the equation for flux?
Flux = (P x DeltaC)/X
How does hyperventilation affect PPO2 and PPCO2?
PPO2 increased
PPCO2 decreased
How does hypoventilation affect PPO2 and PPCO2?
Decreased PPO2
Increased PPCO2
Describe hyperbaric oxygen therapy. (2)
Person placed in chamber with high PO2
Leads to increased PAO2 levels and O2 exchange
Give a condition that can be treated using hyperbaric oxygen therapy.
Severe blood loss
Crush injuries
Anemia
Chronic wounds
Certain infections
Burns
Recovery
Describe decompression sickness and how it is alleviated with hyperbaric oxygen therapy. (2)
Caused by dissolved gases in blood coming out of solution and forming bubbles in bloodstream
Therapy forces gases back into solution, eliminating bubbles
Give 3 pathological changes which adversely affect gas exchange.
Decrease in SA
Increased thickness of alveolar membrane
Increased diffusion distance
What factors can influence alveolar ventilation? (3)
Posture
Rate of inspiration
Amount of air inspired
Give 3 factors that influence lung perfusion.
Hydrostatic pressure in pulmonary arteries
Pressure in pulmonary veins
Alveolar air pressure
What is V/Q mismatch? (2)
When alveolar ventilation (VA) does not match Q (lung perfusion)
Blood is shunted from right to left side of heart without adequate oxygenation
