Graduate School of Decision Science and Technology, Tokyo Institute of Technology, Ookayama 2-12-1-W9-1, Meguro, Tokyo 152-8552, Japan.
J Physiol Anthropol. 2013 Dec 6;32(1):23. doi: 10.1186/1880-6805-32-23.
Heat stress induces various physiological changes and so could influence ocular circulation. This study examined the effect of heat stress on ocular blood flow.
Ocular blood flow, end-tidal carbon dioxide (P(ET)CO2) and blood pressure were measured for 12 healthy subjects wearing water-perfused tube-lined suits under two conditions of water circulation: (1) at 35 °C (normothermia) for 30 min and (2) at 50 °C for 90 min (passive heat stress). The blood-flow velocities in the superior temporal retinal arteriole (STRA), superior nasal retinal arteriole (SNRA), and the retinal and choroidal vessels (RCV) were measured using laser-speckle flowgraphy. Blood flow in the STRA and SNRA was calculated from the integral of a cross-sectional map of blood velocity. PETCO2 was clamped at the normothermia level by adding 5% CO2 to the inspired gas. Passive heat stress had no effect on the subjects' blood pressures. The blood-flow velocity in the RCV was significantly lower after 30, 60 and 90 min of passive heat stress than the normothermic level, with a peak decrease of 18 ± 3% (mean ± SE) at 90 min. Blood flow in the STRA and SNRA decreased significantly after 90 min of passive heat stress conditions, with peak decreases of 14 ± 3% and 14 ± 4%, respectively.
The findings of this study suggest that passive heat stress decreases ocular blood flow irrespective of the blood pressure or arterial partial pressure of CO2.
热应激会引起各种生理变化，从而可能影响眼部循环。本研究探讨了热应激对眼部血流的影响。
12 名健康受试者穿着水灌注管衬套装，在两种水循环条件下测量了眼部血流、呼气末二氧化碳（P（ET）CO2）和血压：（1）在 35°C（正常体温）下 30 分钟；（2）在 50°C 下 90 分钟（被动热应激）。使用激光散斑血流图测量颞上视网膜动脉（STRA）、鼻上视网膜动脉（SNRA）和视网膜脉络膜血管（RCV）的血流速度。从血流速度的横截面图积分计算 STRA 和 SNRA 的血流量。通过向吸入气体中添加 5%CO2 将 PETCO2 夹在正常体温水平。被动热应激对受试者的血压没有影响。RCV 的血流速度在被动热应激 30、60 和 90 分钟后明显低于正常体温水平，90 分钟时最大降低 18±3%（平均值±SE）。STR 和 SNRA 的血流量在 90 分钟的被动热应激条件下显著降低，最大降低分别为 14±3%和 14±4%。
本研究结果表明，被动热应激会降低眼部血流量，而与血压或动脉二氧化碳分压无关。
