Permeability changes in cerebral, iridic, and retinal vessels during experimental decompression sickness in the rat.

An investigation has been made of the effect of acute decompression sickness upon the permeability of the cerebral, iridic, and retinal vessels of the rat, with sodium-fluorescein as intravenous tracer. No permeability changes were observable during the first 15 min subsequent to decompression, following exposure to 5.1 bar for 50 min. Focal leaky areas were found in the brain parenchyma after exposures to 5.1 bar for 120 min. Although sodium-fluorescein partially permeated the pial vessels in controls, the treatment in a hyperbaric chamber seems to increase the diffusion of the tracer from the pia into the cerebral cortex. Nevertheless, both the iridic and retinal vessels remained "tight." The factors which increase the permeability of microvasculature in brain and possible reasons for the negative results obtained with the iris and retina in decompression sickness are discussed.