Blood-brain barrier is maximally permeable to

The permeability of carbon dioxide across the blood-brain barrier was studied in eight patients using the double indicator single injection technique. The extraction (E) was 88% and the permeability coefficient was calculated to 4.4 x 10-3 cm sec-1. The permeability of the blood-brain barrier for CO2 was compared with free diffusion of CO2, and it is concluded that the diffusion restriction by the endothelial cell is minor. Carbonic anhydrase inhibition decreased the extraction of CO2 to 71% and due to this inhibition, the mean capillary circulation time could be estimated as 1.6 sec. Carbon dioxide permeability of the blood-brain barrier in man. The effect of acetazolamide. Ref: guyton and hall textbook of medical physiology 12 edition page number:671,672,673