Changes in Arterial pCO₂ and Retinal Vessel Size with Oxygen Breathing

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Abstract

Arterial blood gas and pH measurements were correlated with changes in retinal vessel diameterin healthy young men during oxygen breathing at elevated atmospheric pressure and during hyperventilation at normal atmospheric pressure. The marked retinal vasoconstriction observed with oxygen breathing was not the result of simultaneous arterial hypocapnia. Hypocapnia produced by hyperventilation while breathing air was not as effective in producing retinal vasoconstriction as was hyperoxia without hyperventilation. These conclusions apply to vessels large enough to be measured on fundus photographs and do not necessarily apply to the smaller vessels and capillaries or to the choroidal vessels.