Photographic Measurement of Retinal Venous Blood Oxygen ； Values in Normal Subjects and the Effect of Change in Body Position and in the Inhalation of Low and High Oxygen Mixtures

摘要

A method is described for measuring by photographic means the percent oxygen saturation of retinal venous blood. In observations on 34 normal, seated subjects the retinal venous blood oxygen saturation was estimated to be 57 percent. S.D. 11 percent.nWhen the arterial blood oxygen is reduced by breathing a low oxygen mixture the retinal venous blood oxygen falls, but less than the arterial oxygen, with a re¬sultant decrease in the retinal arteriovenous oxygen difference. Presumably this is associated with an increased retinal blood flow, resulting from the visible dilatation of the retinal vessels. In 12 subjects, changing from the seated to the recumbent position caused an apparent small drop in retinal venous oxygen saturation, but the change was not statistically significant. In 17 subjects, breathing 100 percent oxygen caused an increase of 24 percent in the retinal venous blood oxygen saturation. This effect is much larger than anticipated and the mechanism of the increase is still obscure.