physiologic dead space

Throughout this paper, the term physiological dead space will be used to refer to the volume of the conducting airway down to the location at which a large change in gas composition occurs.

Bohr's method measures the volume of the lung which does not eliminate CO₂. Because this is a functional measurement, the volume is called the physiologic dead space.

...the effective respiratory dead space is made up of two principal components. The first component is associated with the volume of the respiratory passages leading to the lung.... A second component is the ... well ventilated, but poorly perfused alveoli are in parallel with the respiratory passages and it is convenient to designate this component as the ‘parallel’ dead space.