New insights into ocular blood flow at very high altitudes

Bosch, Martina M; Merz, Tobias M; Barthelmes, Daniel; Petrig, Benno L; Truffer, Frederic; Bloch, Konrad E; Turk, Alex; Maggiorini, Marco; Hess, Thomas; Schoch, Otto D; Hefti, Urs; Sutter, Florian K P; Pichler, Jacqueline; Huber, Andreas; Landau, Klara (2009). New insights into ocular blood flow at very high altitudes. Journal of applied physiology, 106(2), pp. 454-60. Bethesda, Md.: American Physiological Society 10.1152/japplphysiol.90904.2008

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Little is known about the ocular and cerebral blood flow during exposure to increasingly hypoxic conditions at high altitudes. There is evidence that an increase in cerebral blood flow resulting from altered autoregulation constitutes a risk factor for acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) by leading to capillary overperfusion and vasogenic cerebral edema. The retina represents the only part of the central nervous system where capillary blood flow is visible and can be measured by noninvasive means. In this study we aimed to gain insights into retinal and choroidal autoregulatory properties during hypoxia and to correlate circulatory changes to symptoms of AMS and clinical signs of HACE. This observational study was performed within the scope of a high-altitude medical research expedition to Mount Muztagh Ata (7,546 m). Twenty seven participants underwent general and ophthalmic examinations up to a maximal height of 6,800 m. Examinations included fundus photography and measurements of retinal and choroidal blood flow, as well as measurement of arterial oxygen saturation and hematocrit. The initial increase in retinal blood velocity was followed by a decrease despite further ascent, whereas choroidal flow increase occurred later, at even higher altitudes. The sum of all adaptational mechanisms resulted in a stable oxygen delivery to the retina and the choroid. Parameters reflecting the retinal circulation and optic disc swelling correlated well with the occurrence of AMS-related symptoms. We demonstrate that sojourns at high altitudes trigger distinct behavior of retinal and choroidal blood flow. Increase in retinal but not in choroidal blood flow correlated with the occurrence of AMS-related symptoms.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Department of Intensive Care, Emergency Medicine and Anaesthesiology (DINA) > Clinic of Intensive Care
UniBE Contributor:	Merz, Tobias, Barthelmes, Daniel
ISSN:	8750-7587
Publisher:	American Physiological Society
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 15:13
Last Modified:	02 Mar 2023 23:23
Publisher DOI:	10.1152/japplphysiol.90904.2008
PubMed ID:	19057000
Web of Science ID:	000263120400016
URI:	https://boris.unibe.ch/id/eprint/32219 (FactScience: 197228)