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M. Tonini, R. Tamisier, M. Geiser, J.-L. Pepin, P. Levy, J.-P. Romanet, C. Chiquet; Choroidal Blood Flow Variations to Gas in Healthy Young Subjects Before and After Intermittent Hypoxia. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4140.
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To evaluate the effect of 14-day intermittent hypoxia on the response of the sub-foveal choroidal blood flow (ChBF) after gas inhalation, in healthy young subjects.Recent studies have emphasized the effect of the obstructive sleep apnea (OSA) on CO2 vasodilatation and O2 vasoconstriction, these abnormalities being possibly implicated in the variations of ocular blood flow. A human model of OSA has been developed in our laboratory: healthy young subjects were submitting to intermittent hypoxia during 14 consecutive nights. The aim of our study was to determine if these subjects present a dysregulation in ChBF response to hypercapnia and hyperoxia during and after exposition to intermittent hypoxia.
The ChBF was measured before, at the end (D14) and 5 days after the period of exposition to intermittent hypoxia. ChBF was measured using laser Doppler flowmetry (LDF) in 6 healthy young volunteers (20.8+/-0.9 years) exposed to night time intermittent hypoxia. LDF is based on the light scattered by the tissues and the red blood cells (RBCs); corresponding parameters are the velocity (ChBVel), the volume (ChBVol) and the flow (ChBF = ChBVel x ChBVol). We measured the variations in ChBF during 10 minutes of air inhalation (placebo), 100% O2, and carbogen (8% CO2) at each visit.
The ChBF response to carbogen was considered as normal (increase of 11%) before the exposition to intermittent hypoxia, and was reduced at the end (+5%) and after the exposition (+5%). The response to 100% O2 in these subjects was not altered by the exposition to intermittent hypoxia. Using the placebo, the ChBF remained unchanged at each visit. The sensitivity of the measurement was 6 %.
These preliminary results suggest that healthy subjects exposed to intermittent hypoxia exhibit an altered response of ChBF to carbogen. This CO2 responsiveness could be related to an alteration of the nitric oxide synthase expression.
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