The<unk>  is used to quantify the ratio of physiological dead space to the total tidal volume, and gives an indication of the extent of wasted ventilation. The original formulation by<unk> , required measurement of the alveolar partial pressure PA. : The modification by Enghoff replaced the mixed alveolar partial pressure of CO2 with the arterial partial pressure of that gas. The<unk> , with Enghoff's modification, is commonly stated as follows: : Here is the physiological dead space volume and is the tidal volume; :: is the partial pressure of carbon dioxide in the arterial blood, and :: is the partial pressure of carbon dioxide in the average expired (exhaled) air.
Bohr equation
Maxwell–Fricke equation
Shunt equation
Winters' formula
Paula method
Corbett's electrostatic machine
Mentzer index
Falconer's formula