Ocular blood flow decreases during passive heat stress in resting humans

Journal of Physiological Anthropology

Naoyuki Hayashi²  Yuji Yamaguchi¹  Hideaki Kashima¹  Akane Miyaji²  Tsukasa Ikemura² 

[1] Graduate School of Human-Environment Studies, Kyushu University, Kasuga-koen 6-1, Kasuga, Fukuoka 816-8580, Japan;Graduate School of Decision Science and Technology, Tokyo Institute of Technology, Ookayama 2-12-1-W9-1, Meguro, Tokyo 152-8552, Japan

关键词: Hyperthermia;    Choroidal circulation;    Retinal circulation;   

Others  :  861543
DOI  :  10.1186/1880-6805-32-23

 received in 2013-09-04, accepted in 2013-11-19,  发布年份 2013

【 摘 要 】

Background

Heat stress induces various physiological changes and so could influence ocular circulation. This study examined the effect of heat stress on ocular blood flow.

Findings

Ocular blood flow, end-tidal carbon dioxide (P_ETCO₂) 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. P_ETCO₂ 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.

Conclusion

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.

【 授权许可】

   
2013 Ikemura et al.; licensee BioMed Central Ltd.

【 图 表 】

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