Description of Driving Event:
Modification of Prebreathe Protocol for Extravehicular Activity (EVA) Operations
Lesson(s) Learned:
There is an initiative to modify the prebreathe protocol for EVA operations on the ISS. The target is a 2-hour prebreathe from any pressure with the same or better bends risk than the protocol currently used in Space Shuttle operations.
Recommendation(s):
Prior to authorizing any reduction in prebreathe protocol for EVA on the ISS, NASA should conduct a study to ensure that there is no increase in the risk of bends associated with the special circumstances of the proposed new protocol.
Evidence of Recurrence Control Effectiveness:
NASA concurs with the ASAP recommendation, and believes that the recommended study efforts have already been initiated. In 1997, the EVA IPT initiated a Prebreathe Reduction Program (PRP) to address the risk of decompression sickness (DCS) associated with reduced prebreathe protocols. The PRP Team developed a detailed 2-year plan to: - Develop and test an operationally implementable 2-hour prebreathe protocol
- Perform a detailed risk assessment of acceptable DCS risk to provide prospective accept/reject criteria so that there was a clear metric by which to judge the success or failure of the laboratory trials
- Develop improved methods for treating DCS on orbit
- Develop flight rules to document in advance the specific actions that would be taken to manage a DCS contingency should one occur.
Items 2,3,and 4 from above form the NASA "DCS Risk Definition and Contingency Plan." Effort required by that plan has been completed and favorably reviewed by an external review committee chaired by Dr. C. J. Lambertsen. Accept/reject criteria developed from the above plan was used in an extensive, multi-phase laboratory-testing program of an operationally implementable 2-hour prebreathe protocol. This effort was initiated in November 1997 as a multi-center effort led and managed by NASA and involving three external laboratories (Duke University, the Canadian Defense and Civil Institute of Environmental Medicine, and the University of Texas Hermann Hospital).A review of the multi-phased laboratory-testing program results and the entire PRP project conducted by medical experts of the International Partners (the Multi-Lateral Medical Operations Panel subcommittee for EVA) resulted in a committee recommendation that the 2-hour protocol should be safe to implement for EVA's from the ISS. Furthermore, additional internal and external reviews of the laboratory data are planned for June 1999. Pending the recommendations of that review, NASA believes there to be no increase in the risk of bends associated with the special circumstances of the proposed new protocol, and the 2-hour protocol will be implemented for operations on ISS Flight 7A, which includes the first U.S. space walks from the ISS joint airlock. The PRP Team has also developed a 5-year operational research plan with the goals of providing a better understanding of the underlying science of DCS in microgravity and the possibility of further reductions in prebreathe without compromise to safety. This 5-year research program will include four external laboratories, including the Brooks Air Force Base Armstrong Laboratory and the onsite NASA JSC facilities. Finally, NASA is committed to continued investigative/research efforts to address any relevant data obtained from past, current, or future testing in order to assure no increase in the risk of bends associated with the special circumstances of current or proposed new protocol.
Documents Related to Lesson:
N/A
Mission Directorate(s):
- Exploration Systems
- Space Operations
- Aeronautics Research
Additional Key Phrase(s):
- Aerospace Safety Advisory Panel
- Extra-Vehicular Activity
- Medical
- Research & Development
- Safety & Mission Assurance
Additional Info:
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