SF3 Exam 2 Alveolar Ventilation

Question 1

What force acts on the lung that effects ventilation? What does this effect cause?

Answer 1

Gravity.

Imagine a slinky hanging off a point.
This is similar to the lung on the apex.

The top of the lung is stretched out, while the bottom is getting compressed.

This causes a gradient to form, with the top being more negative in pleural space than the bottom.

This gradient causes the biggest alveolar volume to be at the top of the lung and the smallest to be at the bottom.

Overall, the ones at the bottom of gravity have the most ventilation while the top ones have the least

Question 2

Other than gravity, what can alter ventilation?

Answer 2

Lung interstitial diseases ie) fibrotic disease

These diseases are uneven in the lung and cause areas to become less compliant. They are poorly ventilated and have poor gas exchange

Question 3

What does alveolar ventilation take into account that minute ventilation doesn’t?

Answer 3

Dead space

Question 4

What types of dead space are there?

Answer 4

Anatomical and physiological.

They add to make the total dead space

Question 5

Alveolar ventilation is calculated by?

Answer 5

Alv vent=freq(tidal volume*dead space)

Dead space =150

Question 6

What is the relationship between Arterial ventilation and PACO2?

Answer 6

Inverse. (Assuming CO2 prod is constant)

If Va is halved, PCO2 will double

If Va is doubled, PCO2 will be halved

Question 7

What is the relationship between alveolar ventilation and metabolism?

Answer 7

They are directly related.

A person with a higher temp needs a higher ventilation

A person with lower temp needs a lower ventilation.

The ventilation can slowly be adjusted to normal over time.