| PURPOSE: To determine the effects of systemic hyperoxia and hypercapnia on choroidal bood flow in anesthetized rats, during pure oxygen (100%O2) or carbogen (95%O2 + 5%CO2) breathing. METHODS: By using laser Doppler flowmery, choroid blood flow in Urethane-anesthetized adult rats were measured continuously. After basal choroidal blood flow were stable in ambient room air breathing, experimental gas (oxygen or carbogen) was given to replace the room air in the sealed cabin. When the experimental gas replaced the room air completely, choroidal blood flow was recorded for 20 minutes. At the end of experimental gas breathing, blood-gas analyses from the descending aorta were obtained to evaluate the effects of breathing. RESULTS: â‘ Compared with ambient room air breathing, the choroidal blood flow increased during carbogen breathing (P<0.01), but was not altered by pure O2 breathing(P>0.05). â‘¡ Although hemoglobin oxygen saturation level (SaO2), partial pressure of oxygen (PO2) were increased by pure O2 and carbogen breathing, they had no differences between pure O2 and carbogen breathing. Compared with room air breathing, partial pressure of carbon dioxide (PCO2) were increased after carbogen breathing (P<0.01), whereas decreased after pure O2 breathing (P<0.01). â‘¢The correlation analysis showed the choroidal blood flow just pre blood-gas analyses was positively correlated with PCO2(R=0.889,P<0.01). Conclusions : â‘ Carbogen can increase the choroidal blood flow in rats, and it can provide better oxygenation compared with pure O2. â‘¡ Choroidal blood flow in rats were not sensitive to the concentration of O2 in breathing gas, whereas the concentration of CO2 can influence choroidal blood flow remarkably.
|
PDF Full Text Request