VASOCONSTRICTION OF RETINAL ARTERIES DURING O2-BREATHING

97th DOG Annual Meeting 1999

K681
VASOCONSTRICTION OF RETINAL ARTERIES DURING O2-BREATHING

M. Blum, C. Scherf, K. Bachmann, J. Strobel

Background: The newly developed Retinal-Vessel-Analyzer offers the unique opportunity of non-invasive online measurements of retinal vessel diameters. A blood pressure rise due to isometric exercise is followed by an autoregulative vasoconstriction. Breathing of 100% oxygen is another method to test vessel contractility. In the following study healthy volunteers underwent both procedures to compare both methods.

Methods: After a 3-minute baseline measurement healthy volunteers were exposed to 100% oxygen breathing for a 5-minute period. The diameter of a retinal artery was measured by the use of the Retinal-Vessel-Analyzer continuously during this time. The same volunteers went as well through a 9-minute experimental protocol with standardized isometric exercise resulting in a rise in mean arterial pressure (MAP) to provoke a vasoconstriction (Bayliss-effect).

Results: 20 volunteers ( age 22 to 59 yrs.) went through both protocols. In 19 subjects a vasoconstriction of -9,5(±6,9)% was measured over the 5 minutes of oxygen breathing. The amount of vasoconstriction was strongly correlated to age with a linear regression of R²=0,6. Under isometric exercise the same subjects had an MAP-rise of 22,8 (±6,0) mmHg which was answered by a vasoconstriction of -5,5 (±2,2)%. No age correlation was found in these results.

Conclusion: Vasoconstriction as a reaction to 100% oxygen breathing is age-correlated, whereas vasoconstriction as a reaction to changes in blood pressure is not age-correlated. 100% oxygen breathing seems to offer a good provocation test for vascular reactivity. However, the age-correlation should be kept in mind when used in older patients.

Dept. of Ophthalmology, University of Jena, Bachstr. 18, D - 07743 Jena

Supported by Ernst Abbe Foundation, Jena, Germany

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