Diffusivity of N₁ CO₂ and CO in mammalian tissue

Many previous measurements of diffusion coefficients for gases in tissue can be criticized because of inability to separate diffusion flux from metabolic consumption or production, and from fluxes through poorly stirred layers of a bathing medium. The authors circumvent these difficulties by using a tissue that has gas on both sides and by making measurements over a range of concentration differences across the tissue. Rapid diffusion in the gas phase provides a uniform gas concentration up to the edge of the tissue. Excised urinary bladders of cats are filled with a test gas mixture and suspended in air. Rate of disappearance of a particular gas from inside the bladder (cm³ STPD/min), divided by surface area and multiplied by thickness of the bladder, is plotted against partial pressure difference of the gas, inside to outside. The slope of such a plot is a measure of the Krogh constant, and is independent of gas metabolism of the tissue (except for the case of O₂ at low pO₂. Results (in cm² min^-1 atm^-1) at 25°C, CO₂ = 50 x 10^-5. Preliminary results at 37°C, CO₂ = 45 x 10^-5, N₂ = 1.05 x 10^-5, and CO = 1.66 x 10^-5.