Gilmore Edward D, Hudson Chris, Venkataraman Subha T, Preiss David, Fisher Joe
Multi-disciplinary Laboratory for the Research of Sight-Threatening Diabetic Retinopathy, Department of Ophthalmology and Vision Science, University of Toronto, Ontario, Canada.
Invest Ophthalmol Vis Sci. 2004 Sep;45(9):3207-12. doi: 10.1167/iovs.03-1223.
To compare the impact of three different techniques used to induce hyperoxia on end-tidal CO2 (PETCO2). The relationship between change in PETCO2 and retinal hemodynamics was also assessed to determine the clinical research relevance of this parameter.
The sample comprised 10 normal subjects (mean age, 25 years; range, 21-49 years). Each subject attended for three sessions. At each session, subjects initially breathed air followed by O2 only; O2 plus CO2, using a nonrebreathing circuit (with CO2 flow continually adjusted to negate drift of PETCO2); or air followed by O2, using a sequential rebreathing circuit. In addition, using a separate sample of eight normal subjects (mean age, 26.5 years; range, 24-36 years), a methodology that initially raised PETCO2 and then returned to homeostatic levels was used to determine the impact, if any, of perturbation of PETCO2 on retinal hemodynamics.
The difference in group mean PETCO2 between baseline and elevated O2 breathing was significantly different (t-test, P = 0.0038) for O2-only administration with a nonrebreathing system. The sequential rebreathing technique resulted in a significantly lower difference (i.e., before and during hyperoxia) of individual PETCO2 (t-test, P = 0.0317). The PETCO2 perturbation resulted in a significant (P < 0.005) change of retinal arteriolar diameter, blood velocity, and blood flow.
The sequential rebreathing technique resulted in a reduced variability of PETCO2. A relatively modest change in PETCO2 resulted in a significant change in retinal hemodynamics. Rigorous control of PETCO2 is necesssary to attain standardized, reproducible hyperoxic stimuli for the assessment of retinal vascular reactivity.
比较三种不同的诱导高氧方法对呼气末二氧化碳分压（PETCO2）的影响。还评估了PETCO2变化与视网膜血流动力学之间的关系，以确定该参数的临床研究相关性。
样本包括10名正常受试者（平均年龄25岁；范围21 - 49岁）。每位受试者参加三个阶段的测试。在每个阶段，受试者最初呼吸空气，然后仅呼吸氧气；使用非重复呼吸回路呼吸氧气加二氧化碳（持续调整二氧化碳流量以消除PETCO2的漂移）；或使用顺序重复呼吸回路，先呼吸空气然后呼吸氧气。此外，使用另一组8名正常受试者（平均年龄26.5岁；范围24 - 36岁）的样本，采用一种先升高PETCO2然后恢复到稳态水平的方法，以确定PETCO2的扰动对视网膜血流动力学是否有影响。
对于使用非重复呼吸系统仅给予氧气的情况，基线和高氧呼吸时组平均PETCO2之间的差异有显著统计学意义（t检验，P = 0.0038）。顺序重复呼吸技术导致个体PETCO2（即高氧之前和期间）的差异显著更低（t检验，P = 0.0317）。PETCO2的扰动导致视网膜小动脉直径、血流速度和血流量发生显著（P < 0.005）变化。
顺序重复呼吸技术降低了PETCO2的变异性。PETCO2相对适度的变化导致视网膜血流动力学发生显著变化。为评估视网膜血管反应性，要获得标准化、可重复的高氧刺激，必须严格控制PETCO2。
