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Peak Performance - Ventilation and perfusion

6 important questions on Peak Performance - Ventilation and perfusion

What is the ventilation:perfusion?

= Va/Q
when Va = 0, the ratio is 0
when Q= 0, the ratio is infinity
In both cases, gas exchange is impaired.
It is a way of measuring the efficacy of gas exchange.

What happens when either Va or Q is 0?

If Va = 0, the ratio is 0.
If there is no ventilation, then the alveoli composition reaches equilibrium with the blood capillaries.
If Q=0, the ratio is infinity.
If there is no perfusion, then the alveoli composition reaches equilibrium with the atmospheric pressure.

What are the normal pO2 and pCO2 if Va/Q is normal?

pO2= 104mmHg
pCO2= 40mmHg
This is the intermediate between the atmospheric air and the venous blood.

What is the physiological shunt?

If the Va/Q it too low i.e. there is not enough ventilation, some of the venous blood will not become oxygenated. This blood is called SHUNTED blood. The total amount of shunted blood passing per minute is called the physiological shunt.

What is physiological dead space?

If the Va/Q is too high i.e. there is more ventilation than flow of blood, much of the alveoli ventilation and that in the respiratory passage is wasted. The sum of these wastages is called physiological dead space.

What is the Va/Q in the normal lung?

In the upper part of the lung, both the Va and Q is lower than in the lower part. However, Q is significantly lower than Va. This means that Va:Q is higher at the top of the lung and show moderate signs of physiological dead space.

In the lower part of the lung, Va is lower than Q. This means that there is slightly too little ventilation at the bottom of the lung as the Va:Q is slightly low. This means that the lower parts of the lung show moderate signs of physiological shunt.