Retinal oxygen saturation and retinal blood flow during mild hypoxia

Abstract

Purpose: Previous studies have shown that changes in retinal arterial and venous oxygen saturation can be caused by altering the fraction of oxygen in inhaled air. The present study aimed to investigate the influence of 12% oxygen in nitrogen breathing on retinal blood flow and retinal oxygen saturation.

Methods: 30 healthy volunteers were included into the present study. Laser Doppler velocimetry (LDV) was used to determine the effect of 12% oxygen in nitrogen breathing on retinal blood velocities. Assessment of retinal vessel diameters was performed with the Dynamic Vessel Analyzer (DVA, Imedos, Germany). Retinal oxygen saturation was analysed using the same instrument based on spectroscopic evaluation of the data. Assessment of the effects of 12% oxygen in nitrogen breathing on systemic oxygen tension was performed on arterialized blood samples drawn from the earlobe.

Results: We observed that breathing of 12% oxygen in nitrogen caused systemic hypoxia as evidenced from the reduced systemic oxygen tension (p < 0.01). Further we saw a reduction in both arterial and venous oxygen saturation in retinal vessels (p < 0.01 each), which was more noticeable in veins. In parallel we observed an increase in retinal vessel diameters, retinal blood velocities as well as in retinal blood flow (p < 0.05 each).

Conclusions: The present study reveals good validity of retinal oxygen saturation measurements using the DVA. Further the results are compatible with unchanged retinal oxygen extraction during hypoxia.

Keywords: 635 oxygen • 688 retina • 548 hypoxia