Viva - physiological formulae

Question 1

Bohr equation for physiological dead space

Answer 1

VD = VT * (PACO2 - PECO2) / (PACO2)

Dead space = Tidal volume * (Alveolar CO2 - end tidal CO2) / Alveolar CO2

This differs from anatomical dead space (measured by Fowler’s method) as it also includes alveolar dead space.

Can you derive it…?

Question 2

Shunt equation

Question 3

Alveolar gas equation