This page is about modelling the ventilatory function of the lung. But first,
some attention will be given to the principles governing ventilation.
Two gases are important: oxygen (O2) and carbon dioxide (CO2)
The O2 comes from the environment, at a fixed level
The CO2 comes from the blood, at a fixed supply rate
Breathing is by in- and exhaling a volume VT at a rate fR
The standard physical gas law applies: PV=nRT
The VT is called tidal volume, normally expressed in L or mL, and the
fR respiratory frequency, mostly expressed in breaths per minute. In the
gas law, P is pressure, V volume, n number of moles, R universal gas constant
(8.3 J·K−1·mol−1) and T absolute
temperature (K).
The lung has to exchange O2 against CO2
at a sufficient rate, amount per time. It is standard to express rates by a dot
above the respective symbol, like ˙V
n˙ for volume per time
(ventilation) and moles per time respectively.
