Effect of breathing 12% oxygen in nitrogen on retinal blood flow and oxygen saturation

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Abstract

Purpose

It has been reported that altering the fraction of oxygen in inhaled air changes retinal arterial and venous oxygen saturation. In the present study we set out to study the effects of 12% oxygen in nitrogen breathing on retinal blood flow and retinal oxygen saturation.

Methods

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

Results

Breathing 12% oxygen in nitrogen caused systemic hypoxia as evidenced from the reduced systemic oxygen tension (p < 0.01). In addition, a reduction in both arterial and venous oxygen saturation was seen in retinal vessels (p < 0.01 each), which was more pronounced 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).

Conclusion

The results of the present study indicate good validity of retinal oxygen saturation measurements using the DVA. In addition, the results are compatible with unchanged retinal oxygen extraction during hypoxia.

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