Specific ventilation
In respiratory physiology, specific ventilation is defined as the ratio of the volume of gas entering a region of the lung following an inspiration, divided by the end-expiratory volume of that same lung region:
SV =
It is a dimensionless quantity. For the whole human lung, given an indicative tidal volume of 0.6 L and a functional [residual capacity] of 2.5 L, average SV is of the order of 0.24.
The distribution of specific ventilation within the lung can be inferred using Multiple Breath Washout experiments or imaging techniques such as Positron [Emission Tomography] using 13N, Magnetic Resonance Imaging using either hyperpolarized gas or proton MRI.