Kiss B, Dallinger S, Polak K, Findl O, Eichler H G, Schmetterer L
Department of Clinical Pharmacology, University of Vienna, Vienna, Austria.
Microvasc Res. 2001 Jan;61(1):1-13. doi: 10.1006/mvre.2000.2269.
The autoregulatory capacity of the human retina is well documented, but the pressure-flow relationship of the human choroid is still a matter of controversy. Recent data, using laser Doppler flowmetry to measure choroidal blood flow, indicate that the choroid has some autoregulatory potential, whereas most data using other techniques for the assessment of choroidal hemodynamics indicate that the choroidal pressure-flow curve is linear. We used a new laser interferometric technique to characterize choroidal blood flow during isometric exercise. Twenty healthy subjects performed squatting for 6 min during normocapnia and during inhalation of 5% CO2 and 95% air. Ocular fundus pulsation amplitude, flow velocities in the ophthalmic artery, intraocular pressure, and systemic hemodynamics were measured in 2-min intervals. To gain information on choroidal blood flow fundus pulsation amplitude was corrected for changes in flow pulsatility using data from the ophthalmic artery and for changes in pulse rate. Ocular perfusion pressure was calculated from mean arterial pressure and intraocular pressure. The ocular pressure-flow relationship was calculated by sorting data according to ascending ocular perfusion pressure values. In a pilot study in 6 healthy subjects comparable ocular pressure flow relationships were obtained when choroidal blood flow was assessed with the method described above and with laser Doppler flowmetry. In the main study isometric exercise caused a significant increase in mean arterial pressure (56%, P < 0.001), pulse rate (84%, P < 0.001), and intraocular pressure (37%, P 0.004), but decreased fundus pulsation amplitude (-36%, P < 0.001). Significant deviations from baseline choroidal blood flow were observed only at ocular perfusion pressures >69% during normocapnia and 70% during hypercapnia. Our data indicate that during isometric exercise the choroid has a high capacity to keep blood flow constant despite changes in perfusion pressure and that this pressure-flow relationship is not altered by moderate changes in arterial carbon dioxide levels.
人类视网膜的自动调节能力已有充分记录，但人类脉络膜的压力 - 血流关系仍存在争议。最近使用激光多普勒血流仪测量脉络膜血流的数据表明，脉络膜具有一定的自动调节潜力，而大多数使用其他技术评估脉络膜血流动力学的数据表明，脉络膜压力 - 血流曲线是线性的。我们使用一种新的激光干涉技术来表征等长运动期间的脉络膜血流。20名健康受试者在正常碳酸血症期间以及吸入5%二氧化碳和95%空气时进行6分钟的深蹲。每隔2分钟测量一次眼底搏动幅度、眼动脉血流速度、眼压和全身血流动力学。为了获取脉络膜血流信息，使用眼动脉数据对眼底搏动幅度进行血流搏动性变化校正以及心率变化校正。根据平均动脉压和眼压计算眼灌注压。通过按眼灌注压值升序对数据进行排序来计算眼压 - 血流关系。在一项对6名健康受试者的初步研究中，当使用上述方法和激光多普勒血流仪评估脉络膜血流时，获得了可比的眼压 - 血流关系。在主要研究中，等长运动导致平均动脉压显著升高（56%，P < 0.001）、心率显著升高（84%，P < 0.001）和眼压显著升高（37%，P = 0.004），但眼底搏动幅度降低（-36%，P < 0.001）。仅在正常碳酸血症期间眼灌注压>69%以及高碳酸血症期间眼灌注压>70%时，观察到与基线脉络膜血流有显著偏差。我们的数据表明，在等长运动期间，尽管灌注压发生变化，脉络膜仍具有保持血流恒定的高能力，并且这种压力 - 血流关系不会因动脉二氧化碳水平的适度变化而改变。
