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New insights into ocular blood flow at very high altitudes


Bosch, M M; Merz, T M; Barthelmes, D; Petrig, B L; Truffer, F; Bloch, K E; Turk, A; Maggiorini, G; Hess, T; Schoch, O D; Hefti, U; Sutter, F K P; Pichler, J; Huber, A; Landau, K (2009). New insights into ocular blood flow at very high altitudes. Journal of Applied Physiology, 106(2):454-460.

Abstract

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.

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.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic for Pneumology
04 Faculty of Medicine > University Hospital Zurich > Clinic and Policlinic for Internal Medicine
04 Faculty of Medicine > University Hospital Zurich > Ophthalmology Clinic
04 Faculty of Medicine > Center for Integrative Human Physiology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2009
Deposited On:11 Mar 2009 16:40
Last Modified:05 Apr 2016 13:04
Publisher:American Physiological Society
ISSN:0161-7567
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:10.1152/japplphysiol.90904.2008
PubMed ID:19057000
Permanent URL: http://doi.org/10.5167/uzh-15963

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