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S.P. Kresovsky, A. Harris, L. Kagemann, R. Yung, R. Dinn; Venous Oxygen Saturation Reduced During Hypoxia . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1304.
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Purpose: The purpose of this study is to compare the oxygen saturation of retinal veins during respiration of room air oxygen levels and hypoxic conditions. Method: All procedures were approved by an IRB, and informed consent obtained. Thirty-two oximetry images (12 male, 20 female) were obtained in 14 normal healthy adults (mean 37.1 years, SD=9.1) using a newly developed digital retinal oximeter. Measurements were taken while subjects were breathing room air and a mixture of room air and nitrogen. During hypoxia, arterial saturations were reduced to approximately 90%. Images were analyzed to determine arterial and venous oxygen saturation. The levels of venous oxygen saturation during normal oxygen and hypoxic conditions were compared using a Mann-Whitney unpaired u test. Arterial and venous oxygen saturations were compared by linear regression under each condition. A p>0.05 was considered significant. Results: There was a significant decrease of 3.5% (p=0.0482) in oxygen saturation of the venous blood during hypoxia. Although there was no significant correlation in venous oxygen saturation vs. arterial oxygen saturation while breathing room air, venous oxygen saturation and arterial oxygen saturation correlated significantly during hypoxia (p=0.0073, r2=0.465). Conclusion: Decreases in venous oxygen saturation during episodes of hypoxia are hypothesized to be associated with a consistent amount extraction of oxygen from arterial blood. As arterial blood oxygen saturation decreases, maintenance of oxygen extraction results in reduced venous oxygen saturation.
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