Sunday, January 19 (2020); Respiratory system
Diffusion of respiratory gases is governed by Fick's Law and Graham's Law. As such, the main determinants of diffusion are the density of the gas, its molecular size, temperature, solubility and fluid viscosity, the partial pressure gradient between compartments, the surface area of the membrane and the speed at which the solvent is moving past it. The characteristic feature of this topic seems to be the large number of numerical values which, upon closer examination, are not particularly well supported by references, or which originate in ancient papers from the 1940s. Most textbooks are quite happy to plagiarise from one another and by some intergenerational cut-and-pasting, these values have been transmitted unchanged to the modern day. The CICM trainees are advised to regurgitate these numbers without questioning their origin.