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Related Experiment Videos

The effect of simulated weightlessness on hypobaric decompression sickness.

Ulf I Balldin1, Andrew A Pilmanis, James T Webb

  • 1Air Force Research Laboratory, Biodynamics and Protection Division, Brooks Air Force Base, TX 78235-5104, USA. ulf.balldin@brooks.af.mil

Aviation, Space, and Environmental Medicine
|August 17, 2002
PubMed
Summary

Simulated weightlessness did not affect decompression sickness (DCS) incidence during hypobaric exposure. However, simulated weightlessness reduced venous gas emboli (VGE) formation, suggesting gravity influences bubble formation during spaceflight simulations.

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Area of Science:

  • Space Medicine
  • Aerospace Physiology
  • Human Physiology

Background:

  • A notable discrepancy exists between ground-based simulated extravehicular activity (EVA) decompression sickness (DCS) incidence (20-40%) and zero reported cases during actual EVA.
  • This difference may be attributed to the influence of gravity in ground-based DCS studies.

Purpose of the Study:

  • To investigate the incidence of hypobaric DCS at EVA suit pressures (29.6 kPa) under simulated weightlessness conditions.
  • To compare DCS incidence and venous gas emboli (VGE) formation between a control group and a group in a supine position simulating weightlessness.

Main Methods:

  • Male subjects were exposed to 29.6 kPa hypobaric pressure for up to 4 hours.
  • The control group (n=26) pre-oxygenated while walking, whereas the test group (n=39) remained supine for 3 hours prior to and during pre-oxygenation and hypobaric exposure.
Keywords:
NASA Discipline Environmental HealthNon-NASA Center

Related Experiment Videos

  • DCS symptoms and VGE were monitored throughout the hypobaric exposure.

    • Main Results:

    • No significant difference in DCS incidence was observed between the control group (42%) and the simulated weightlessness group (44%).
    • Venous gas emboli (VGE) occurred significantly less frequently in the simulated weightlessness group (51%) compared to the control group (81%) (p=0.02).
    • Severe VGE also trended lower in the simulated weightlessness group (33% vs. 58%).

    Conclusions:

    • Simulated weightlessness does not alter the incidence of DCS during hypobaric exposure at EVA suit pressures.
    • Simulated weightlessness appears to reduce the formation of VGE, particularly during movements that could release bubbles.