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J-A Pournaras, S Poitry, J-L Munoz, CJ Pournaras; Effect of Carbogen (95% O2, 5% CO2) on Preretinal PO2 in Normal and in Ischemic Post Experimental Branch Vein Occlusion Retinas . Invest. Ophthalmol. Vis. Sci. 2002;43(13):517.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the variations of preretinal PO2 in normal and in ischemic post experimental branch vein occlusion (brvo) retinal areas, during normoxia, hyperoxia (100% O2) and carbogen (95% O2, 5 % CO2) breathing. Method: Preretinal PO2 measurements were obtained in intervascular retinal areas, far from the retinal vessels of anesthetized miniature pigs (n=13) with oxygen sensitive microelectrodes (10µm tip diameter) introduced through the vitreous cavity by a micromanipulator. The microelectrode tip was placed at 50 µm from the vitreoretinal interface in the preretinal vitreous. PO2 was measured continuously during 10 minutes under systemic normoxia, hyperoxia (100% O2 breathing) and carbogen (95% O2, 5 % CO2 breathing). A brvo was induced with an argon green laser, and oxygen measurements were repeated under normoxia, hyperoxia and carbogen breathing. Results: In hyperoxia, preretinal PO2 remained almost constant in both normal (Δ;PO2 = 1.33 mmHg 3.39 ; n=13) and ischemic retinas (Δ;PO2 = 3.73 mmHg 2.84 ; n=8), although systemic PaO2 significantly increased. Carbogen breathing induced a significant increase in systemic PaO2 and PaCO2. Furthermore, it increased significantly the preretinal PO2 (Δ;PO2= 23.05 mmHg 17.06 (n=12) in normal, and Δ;PO2= 22.54 mmHg 5.96 (n=6) in ischemic retinal areas). Conclusion: Systemic hyperoxia does not increase preretinal PO2 significantly in normal and ischemic post brvo retinal areas of miniature pigs, as hyperoxia induces a decrease in the retinal blood flow. Carbogen breathing significantly increases preretinal PO2 in normal and in ischemic post brvo retinal areas. This effect is probably due to the vasodilatation of the retinal arterioles induced by the intravascular PaCO2 increase.
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