Facilitated diffusion of carbon dioxide in whole blood and hemoglobin solutions

The values of effective permeability (Krogh's diffusion coefficient) for carbon dioxide have been measured in horizontal stationary layers of whole blood and hemoglobin solutions in quasi-steady state, with the goal of understanding the specific nature of facilitated diffusion of carbon dioxide occurring in these media. The average partial pressure of carbon dioxide within the layer ranged from 0.74 kPa (5.6 mm Hg) to 15.7 kPa (118 mm Hg). Facilitation effects were significant in hemolysed blood and in hemoglobin solutions at low pCO₂; the facilitation factor was up to 2.3. Facilitation effects were considerably less for intact blood; the facilitation factor of intact blood with hematocrit 45% was 0.3. The presence of the red cell membrane appears to have a negative effect on facilitation of carbon dioxide transport.