Diffusivity of various inert gases in rat skeletal muscle

Abstract

Krogh's diffusion constant (K) was determined for various inert gases in isolated rat abdominal muscle at 37° C by measuring the amount of gas diffusing per unit time and partial pressure difference through a portion of the muscle of known surface area and thickness. The following mean values forK, in 10⁻⁹ mmol·min⁻¹·cm⁻¹·torr⁻¹, were obtained: C₂H₂, 41.2; N₂O, 20.0; CHClF₂, 18.8; H₂, 1.67; He, 1.42; CH₄, 1.27; SF₆, 0.081. From Krogh's diffusion constant, the diffusion coefficient (D) was calculated using the solubility coefficient determined previously in the same preparation. TheD values thus obtained were found to be about half theD values in water at 37° C. Model calculations show that for gases with high lipid/water partition coefficient,D in tissues containing lipid is underestimated by this method. Graham's law (inverse proportionality betweenD and square root of molecular mass) was found to represent a useful approximation for these gases. A better correlation, however, was obtained betweenD and the molecular diameter.