Medicine — Ventilation/Perfusion

\frac{\dot{V}}{\dot{Q}} \approx 0.8

P_AO_2 = P_iO_2 - \frac{P_aCO_2}{R}

\text{rate} \propto \frac{A\,\Delta P}{d}\ \text{(Fick)}

\text{A-a gradient widens in disease}