Lecture 4

Question 1

What is the difference between ventilation and perfusion

Answer 1

Ventilation is airflow into the alveoli and blood flow into the alveoli is perfusion.

Question 2

What is transpulmonary pressure

Answer 2

It is the pressure difference across the wall of the lung

Intrapulmonary P - intrapleural P

Question 3

How do alveoli change from the apex to the basr

Answer 3

As you move from the apex to the base the alveoli become less inflated, more complaint and maximally inflated during inspiration

Question 4

What do you understand by compliance and why do we say alveoli in upper regions have greater volume and are less compliant

Answer 4

Compliance is the maximal expansion an alveoli can reach during inspiration. Greater volume in their natural state and less compliance because during inspiration they can’t expand as they are already big in volume.

Question 5

Between the base and the apex of the lungs which one has

• high blood flow
• high vascular resistance

Answer 5

• base of the lungs

- apex of the lungs

Question 6

The ventilation-perfusion ratio = alveolar minute ventilation (VA) / cardiac output (QT).
The normal value is 0.8, where is it lower than normal and why (apex or base of the lung)

Answer 6

It is lower than normal at the base because that’s where perfusion is greater than ventilation.

Question 7

When V/Q ratio is equal to zero , do we have an absolute shunt or an absolute dead space?

Answer 7

An absolute shunt because it means ventilation is zero and only a shunt results in no ventilation coming in.

Question 8

When ventilation is greater than perfusion which one should exceed the other between airflow and bloodflow to help balance

Answer 8

Blood flow(perfusion) should exceed ventilation in the lungs.

Question 9

What is the difference between anatomical and alveolar dead space

Answer 9

Anatomical dead space partakes in gaseous exchange and alveolar dead space does not take part in gaseous exchange