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Intraocular pressure and cerebral oxygenation during prolonged headward acceleration
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.ORCID iD: 0000-0002-7440-2171
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
2016 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 117, no 1, 61-72 p.Article in journal (Refereed) Published
Abstract [en]

Supra-tolerance head-to-foot directed gravitoinertial load (+Gz) typically induces a sequence of symptoms/signs, including loss of: peripheral vision-central vision-consciousness. The risk of unconsciousness is greater when anti-G-garment failure occurs after prolonged rather than brief exposures, presumably because, in the former condition, mental signs are not consistently preceded by impaired vision. The aims were to investigate if prolonged exposure to moderately elevated +Gz reduces intraocular pressure (IOP; i.e., improves provisions for retinal perfusion), or the cerebral anoxia reserve. Subjects were exposed to 4-min +Gz plateaux either at 2 and 3 G (n = 10), or at 4 and 5 G (n = 12). Measurements included eye-level mean arterial pressure (MAP), oxygenation of the cerebral frontal cortex, and at 2 and 3 G, IOP. IOP was similar at 1 (14.1 +/- 1.6 mmHg), 2 (14.0 +/- 1.6 mmHg), and 3 G (14.0 +/- 1.6 mmHg). During the G exposures, MAP exhibited an initial prompt drop followed by a partial recovery, end-exposure values being reduced by ae<currency>30 mmHg. Cerebral oxygenation showed a similar initial drop, but without recovery, and was followed by either a plateau or a further slight decrement to a minimum of about -14 mu M. Gz loading did not affect IOP. That cerebral oxygenation remained suppressed throughout these G exposures, despite a concomitant partial recovery of MAP, suggests that the increased risk of unconsciousness upon G-garment failure after prolonged +Gz exposure is due to reduced cerebral anoxia reserve.

Place, publisher, year, edition, pages
Springer, 2016. Vol. 117, no 1, 61-72 p.
Keyword [en]
Cerebral anoxia reserve; Cerebral blood flow; G tolerance; G-induced loss of consciousness; Oxyhaemoglobin saturation; Retinal anoxia reserve
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:kth:diva-195347DOI: 10.1007/s00421-016-3499-3ISI: 000394313300007ScopusID: 2-s2.0-84994761979OAI: oai:DiVA.org:kth-195347DiVA: diva2:1044321
Note

QC 20161117

Available from: 2016-11-02 Created: 2016-11-02 Last updated: 2017-03-27Bibliographically approved

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