Geiser M H, Riva C E, Dorner G T, Diermann U, Luksch A, Schmetterer L
Institute de Recherche en Ophthalmologie, Sion, Switzerland.
Curr Eye Res. 2000 Aug;21(2):669-76.
Arterial carbon dioxide tension and arterial oxygen tension are important determinants of retinal and cerebral blood flow. In the present study the hypothesis that changes in arterial blood gases also influence choroidal blood flow was tested.
The effect of breathing different mixtures of oxygen (O(2)) and carbon dioxide (CO(2)) on choroidal blood flow in the foveal region was investigated in healthy subjects. The study was performed in a randomized, double-masked four way cross-over design in 16 subjects. Using a compact laser Doppler flowmeter, red blood cell velocity (ChBVel), volume (ChBVol), and flow (ChBF) in the choroidal vasculature were measured during the breathing of various mixtures of O(2)and CO(2) (hyperoxia-hypercapnia): 100% O(2), 97%O(2)+3%CO(2), 95%O(2)+5%CO(2) (carbogen) and 92%O(2)+8%CO( 2). Arterial oxygen tension (pO(2)) and carbon dioxide tension (pCO(2)) were measured from arterialized blood samples from the earlobe.
Breathing 100% O(2) had no significant effect on ChBVel (-3.7%), ChBVol (+1.7%) and ChBF (-4.3%). Addition of 3% CO(2) to O(2) also produced no significant change on these blood flow parameters. In contrast, carbogen significantly increased ChBVel (10.0 +/- 4.4%, 95% CI, p < 0.001) and ChBF (12.5 +/- 11.7%, p = 0.002). The effect of 92% O(2) + 8% CO(2) was more pronounced since it significantly increased ChBVel and ChBF by 15.5 +/- 7.5% (p < 0.001) and 16.2 +/- 11.0% (p < 0.001), respectively. None of the gas mixtures induced a significant change in ChBVol. The increase in ChBF was approximately 1.5% per 1 mmHg increase in pCO(2).
This study demonstrates that, in healthy subjects, pCO(2) is an important determinant of foveal choroidal blood flow, whereas pO(2) has little impact on it.
动脉血二氧化碳分压和动脉血氧分压是视网膜和脑血流的重要决定因素。在本研究中，对动脉血气变化也会影响脉络膜血流这一假说进行了验证。
在健康受试者中，研究呼吸不同氧（O₂）和二氧化碳（CO₂）混合气体对黄斑区脉络膜血流的影响。该研究采用随机、双盲四交叉设计，纳入16名受试者。使用紧凑型激光多普勒血流仪，在呼吸不同O₂和CO₂混合气体（高氧 - 高碳酸血症）期间，测量脉络膜血管系统中的红细胞速度（ChBVel）、体积（ChBVol）和流量（ChBF），这些混合气体包括：100% O₂、97% O₂ + 3% CO₂、95% O₂ + 5% CO₂（卡波金）和92% O₂ + 8% CO₂。从耳垂处采集动脉化血样，测量动脉血氧分压（pO₂）和二氧化碳分压（pCO₂）。
呼吸100% O₂对ChBVel（-3.7%）、ChBVol（+1.7%）和ChBF（-4.3%）无显著影响。在O₂中添加3% CO₂对这些血流参数也无显著变化。相比之下，卡波金显著增加了ChBVel（10.0±4.4%，95%可信区间，p<0.001）和ChBF（12.5±11.7%，p = 0.002）。92% O₂ + 8% CO₂的效果更显著，因为它分别使ChBVel和ChBF显著增加了15.5±7.5%（p<0.001）和16.2±11.0%（p<0.001）。没有一种气体混合物能引起ChBVol的显著变化。ChBF的增加约为每pCO₂升高1 mmHg增加1.5%。
本研究表明，在健康受试者中，pCO₂是黄斑区脉络膜血流的重要决定因素，而pO₂对其影响较小。
