Specific ventilation

{{Short description|Measure of gas entering a region of the lung}}

{{Orphan|date=October 2017}}

{{lead too short|date=July 2013}}

In respiratory physiology, specific ventilation is defined as the ratio of the volume of gas entering a region of the lung (ΔV) following an inspiration, divided by the end-expiratory volume (V₀) of that same lung region:

SV = {{frac|ΔV|V₀}}

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 (MBW) experiments [http://jap.physiology.org/content/44/3/416.abstract?sid=d898c725-6248-486d-9103-1e7f3984a37d Lewis et al], S. M. Lewis, J. W. Evans, and A. A. Jalowayski. Continuous distributions of specific ventilation recovered from inert gas washout, Journal of Applied Physiology, 1978 vol. 44 no. 3 416-423 or imaging techniques such as Positron Emission Tomography (PET) using ¹³N, Magnetic Resonance Imaging (MRI) using either hyperpolarized gas (³He, ¹²⁹Xe) or proton MRI (oxygen enhanced imaging).