Effect of carbogen (95% O2/5% CO2) on retinal oxygenation in dark-adapted anesthetized cats

This work assessed the relative effects of inspiring carbogen (95% O(2)/5% CO2) and 100% O2 on intraretinal PO2 and oxygen consumption in the cat retina. Oxygen microelectrodes were used to measure the distribution of oxygen in the central retina of dark-adapted anesthetized cats during normoxia, 100% O2 breathing, and carbogen breathing. Profiles of oxygen tension (PO2) as a function of retinal depth were recorded. Changes in PO2 caused by the transient administration of carbogen and 100% oxygen were also measured at selected retinal depths. Average PO2 values at the choroid, at the boundary between the inner and outer retina, and across the inner retina were significantly higher during inspiration of carbogen than 100% O2. There were no significant differences among conditions in outer retinal oxygen consumption. During the transient gas administration, average changes in PO2 generally increased with depth. At the end of gas administration, the decay of PO2 within the retina occurred quickly, meaning that short-term gas administration may have little therapeutic value.