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Indices of Increased Decompression Stress Following Long-Term Bed Rest
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
SLB Consulting, Newbiggin On Lune, Cumbria, England..
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
Jozef Stefan Inst, Dept Automat Biocybernet & Robot, Ljubljana, Slovenia.;Simon Fraser Univ, Dept Biomed Physiol & Kinesiol, Burnaby, BC, Canada..
2018 (English)In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 442Article in journal (Refereed) Published
Abstract [en]

Human extravehicular activity (EVA) is essential to space exploration and involves risk of decompression sickness (DCS). On Earth, the effect of microgravity on physiological systems is simulated in an experimental model where subjects are confined to a 6 degrees head-down bed rest (HDBR). This model was used to investigate various resting and exercise regimen on the formation of venous gas emboli (VGE), an indicator of decompression stress, post-hyperbaric exposure. Eight healthy male subjects participating in a bed rest regimen also took part in this study, which incorporated five different hyperbaric exposure (HE) interventions made before, during and after the HDBR. Interventions i-iv were all made with the subjects lying in 6 degrees HD position. They included (C1) resting control, (C2) knee-bend exercise immediately prior to HE, (T1) HE during the fifth week of the 35-day HDBR period, (C3) supine cycling exercise during the HE. In intervention (C4), subjects remained upright and ambulatory. The HE protocol followed the Royal Navy Table 11 with 100 min spent at 18 m (280 kPa), with decompression stops at 6 m for 5 min, and at 3 m for 15 min. Post-HE, regular precordial Doppler audio measurements were made to evaluate any VGE produced post-dive. VGE were graded according to the Kisman Masurel scale. The number of bubbles produced was low in comparison to previous studies using this profile [Kisman integrated severity score (KISS) ranging from 0-1], and may be because subjects were young, and lay supine during both the HE and the 2 h measurement period post-HE for interventions i-iv. However, the HE during the end of HDBR produced significantly higher maximum bubble grades and KISS score than the supine control conditions (p < 0.01). In contrast to the protective effect of pre-dive exercise on bubble production, a prolonged period of bed rest prior to a HE appears to promote the formation of post-decompression VGE. This is in contrast to the absence of DCS observed during EVA. Whether this is due to a difference between hypo- and hyperbaric decompression stress, or that the HDBR model is a not a good model for decompression sensitivity during microgravity conditions will have to be elucidated in future studies.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2018. Vol. 9, article id 442
Keywords [en]
bed rest, extravehicular activity, decompression sickness, venous gas emboli, space simulation
National Category
Physiology
Identifiers
URN: urn:nbn:se:kth:diva-232766DOI: 10.3389/fphys.2018.00442ISI: 000439071300001Scopus ID: 2-s2.0-85050226774OAI: oai:DiVA.org:kth-232766DiVA, id: diva2:1236596
Funder
Swedish National Space Board, 151-12
Note

QC 20180803

Available from: 2018-08-03 Created: 2018-08-03 Last updated: 2018-08-06Bibliographically approved

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Gennser, MikaelEiken, Ola

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