[abstract] DCS RISKS IN GROUND-BASED HYPOBARIC TRIALS VS. EXTRAVEHICULAR ACTIVITY

Rubicon Research Repository/Manakin Repository

[abstract] DCS RISKS IN GROUND-BASED HYPOBARIC TRIALS VS. EXTRAVEHICULAR ACTIVITY

Show full item record


Title: [abstract] DCS RISKS IN GROUND-BASED HYPOBARIC TRIALS VS. EXTRAVEHICULAR ACTIVITY
Author: Gernhardt, ML; Conkin, J; Vann, RD; Pollock, NW; Feiveson, AH
Abstract: BACKGROUND: Significant differences were observed in DCS incidence during ground trials (GT=8/35) and extravehicular activity (EVA) (EVA=0/141) using Shuttle prebreathe protocols (Fisher Exact Test [FET] p less than 0.05). Factors potentially contributing to the lower EVA risk include enhanced nitrogen elimination (cardiovascular/respiratory dynamics and/or safety margins incorporated into routinely longer operational prebreathes [mean time at 10.2 psi greater than 42 hrs for EVA vs. 12 hrs for GT]) and decreased nuclei formation (reductions in weight-bearing and/or joint motions in the space suit). METHODS: Differences between flight and ground tests were reviewed to develop an improved ground test bed, incorporating semi-recumbent, non-ambulatory subjects performing EVA simulations with reduced joint motions representative of EVA activity. Light prebreathe metabolic exercise (~5.9 mL kg-1 min-1), simulating normal in-suit metabolic overhead, was added to some protocols. Two-hundred-twenty test subjects performed 7 different protocols using the new test bed. Logistic Regression models (LRM) developed using recent ground test data were used to predict the "as flown" Shuttle EVA DCS risk. RESULTS: Of the 7 protocols tested only one met the conditions for acceptability for flight (Phase II). There have been no reports of DCS in 34 EVA uses of this protocol from the International Space Station (no significant difference between EVA and GT, p greater than 0.05 FET)). The LRM predicted risk of the "as flown" Shuttle protocols is within the 95percent CI of the EVA incidence. CONCLUSION: The current NASA ground tests and predictive models are more representative of EVA than previous ground tests. Ground testing remains an important step in identifying acceptable prebreathe protocols. More research is needed to understand the individual contributions of the variables affecting suited microgravity DCS risk.
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: http://archive.rubicon-foundation.org/1537
Date: 2004

Files in this item

Files Size Format View
abstract.txt 259bytes Text file View/Open

This item appears in the following Collection(s)

  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

Show full item record

Browse

My Account