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Astronaut Care for Exploration Missions
Copyright © 2001 National Academy of Sciences
All right reserved.
Space travel is inherently risky. Space beyond Earth orbit is an extreme and isolated unique environment. Currently, not enough is known of the risks of prolonged travel in deep space to enable humans to venture there for prolonged periods safely. To support safe human exploration of space, the National Aeronautics and Space Administration (NASA) should pursue a two-component strategy: (1) it should pursue a comprehensive health care system for astronauts to capture all relevant epidemiological data, and (2) it should pursue a long-term, focused health care research strategy to capture all necessary data on health risks and their amelioration. An occupational health model should apply to the first pursuit, and a modification of the interpretation of the Common Rule (45 C.F.R., Part 46, Subpart A) for human research participants should apply to the second one. One special focus of research should be the complex behavioral interactions of humans in extreme, isolated microenvironments such as inside spacecraft. To accomplish this strategy, there should be an organizational component within NASA that has authority over and accountability for all aspects of astronaut health.
Space travel is inherently risky, and space travel on long-duration missions (those of a year or longer) beyond Earth orbit (beyond the orbital band of launched satellites and the International Space Station [ISS]) entails special risks to humans. Deep space is a unique environment. It is unique for several reasons: (1) it likely has unknown risks, (2) there are no validated effective responses to most of the known risks that humans will encounter there, and (3) it isolates humans, in that humans in deep space will not have the capability for either real-time communication with Earth or a timely return. The acquisition of a fundamental understanding of these risks and the development of solutions to the problems that they present are the subjects of this report.
TASK OF THE COMMITTEE
The general charge to the Committee on Creating a Vision for Space Medicine During Travel Beyond Earth Orbit was to develop a vision for space medicine for long-duration space travel. With the important exception of the ISS, such travel is many years in the future. During the interim, innumerable changes will occur, many of which are unpredictable. As new knowledge is developed, humans will learn much that is directly applicable to the task of enabling safe space travel. Institutional arrangements will shift, and as priorities change, new management principles will be applied; often, these will be affected by political realities. In this report, the committee focuses on the development of principles that should guide future approaches to the issues.
In planning for long-duration space travel beyond Earth orbit, the National Aeronautics and Space Administration (NASA) is undergoing a transition from the relatively known (e.g., the space shuttle has flown more than 100 missions) to the unknown. In addition, a second transition is occurring: from an emphasis on the machinery of spaceflight to an increased emphasis on the biology of spaceflight. For both NASA and the engineering community this is a conceptual shift that has important practical implications as biology adds to chemistry, mathematics, and physics as guiding sciences in engineering in general and in NASA's mission. The challenges afforded by these twin transitions offer NASA a strategic opportunity to reexamine its processes and structure and to build on its successes.
In addition to the general charge to the committee, NASA gave the committee several specific tasks. Chapter 1 introduces the health problems that may confront humans in deep space. Chapter 2 addresses what is known about the risks to health during space travel and where clinical research opportunities exist. Chapters 3 and 4 review what is known about health care during space travel and where opportunities may exist for the development of effective approaches to health care during travel in deep space. Chapters 5 and 6 highlight two specific areas that the committee believes are critical: (1) behavioral, cultural, and social issues (Chapter 5) and (2) an approach to the collection of the clinical data necessary to ensure the safety of space travel beyond Earth orbit (Chapter 6). Chapter 7 suggests ways in which an effective health care system for astronauts might be organized.
Two themes run throughout the report: (1) that not enough is yet known about the risks to human health during long-duration missions beyond Earth orbit or about what can effectively mitigate those risks to enable humans to travel and work safely in the environment of deep space and (2) that everything reasonable should be done to gain the necessary information before humans are sent on missions of space exploration.
Throughout its history, NASA has dealt successfully with transition: the transition from atmospheric flight, to supersonic flight, to suborbital flight, to orbital flight (which culminated with the space shuttle), and to orbital missions, both with Mir and, more recently, with the ISS. Long-duration missions beyond Earth orbit represent another transition and another opportunity. Such missions are not merely quantitatively different; they are also qualitatively different.
The three most important health issues that have been identified for long-duration missions are radiation, loss of bone mineral density, and behavioral adaptation. First, although exposure to radiation is of concern during missions in low Earth orbit, its potential effects become more acutely worrisome during extravehicular activity and are chronically worrisome for those living on the ISS. Longer-duration missions increase the risk at least arithmetically because of the length of the mission and the changing character of radiation in the environment. This is a formidable challenge for engineering, basic biomedical, and clinical research, as discussed in the section Environmental and Occupational Health in Chapter 3. Second, loss of bone mineral density, which apparently occurs at an average rate of 1 percent per month in microgravity, is relatively manageable on the short-duration missions of the space shuttle, but it becomes problematic on the ISS, as described in Chapter 2. If this loss is not mitigated, interplanetary missions will be impossible. Finally, human interactions aboard a spacecraft, isolated in time and space from Earth, may well be one of the more serious challenges to exploratory missions by humans (Chapter 5).
Risk is of high priority to NASA, and determination of what risks to humans exist and what countermeasures should be taken are addressed through NASA's Critical Path Roadmap project ("countermeasure" is NASA's designation for preventive and therapeutic interventions before or during space missions). Nevertheless, risk should be addressed at other levels. At the level of the individual astronaut, for example, how may an astronaut come to a personal decision in a truly informed way to accept the risk of a maiden voyage to Mars? To make an informed personal decision, astronauts should be involved in the process that identifies risks and their amelioration, not only from the standpoint of immediate countermeasures over which they might have control while in flight but also from the standpoint of those risks for which they have no personal or immediate control. At the level of society, on the other hand, risks should be addressed explicitly. The successes of the space program may have fostered the impression that space travel has few associated risks. Making potential problems and overall risks clear and openly disclosing them will allow NASA to gain continuing public understanding, trust, and support for exploration-class space missions. NASA can tailor the amount of detail disclosed in relation to the anticipated severity and prevalence of the risks to astronaut health and safety and the level of support that NASA is seeking. At the extreme, the public must be prepared for the possibility that all countermeasures may tragically fail, that a crew may not return from a prolonged mission, or that individuals may not be able to function physically or mentally upon their return.
There is a profound professional and ethical responsibility to evaluate honestly the risk to human life that accompanies long-duration space travel. This risk should be evaluated through clinical research (Box 1) in the context of the benefit to humans, but it should be stated at the level of the individual in terms that can be plainly understood.
Space travel is inherently hazardous. The risks to human health of long-duration missions beyond Earth orbit, if not solved, represent the greatest challenge to human exploration of deep space. The development of solutions is complicated by lack of a full understanding of the nature of the risks and their fundamental causes.
The unique environment of deep space presents challenges that are both qualitatively and quantitatively different from those encountered in Earth orbit. Risks are compounded by the impossibility of a timely return to Earth and of easy resupply and by the greatly altered communications with Earth.
The successes of short-duration space missions may have led to misunderstanding of the true risks of space travel by the public. Public understanding is necessary both for support of long-duration missions and in the event of a catastrophe.
Recommendation 1 NASA should give increased priority to understanding, mitigating, and communicating to the public the health risks of long-duration missions beyond Earth orbit.
The process of understanding and mitigating health risks should be open and shared with both the national and the international general biomedical and health care research communities.
The benefits and risks-including the possibility of a catastrophic illness or death-of exploratory missions should be communicated clearly, both to astronauts and to the public.
To understand, prevent, and mitigate risks, knowledge of the risks is necessary. Because of the relatively few opportunities to acquire and analyze data from studies conducted in microgravity environments, every possible opportunity to do so must be exploited. Opportunities for the collection of two types of data exist: clinical data on the astronauts and the results of astronaut health care research (Box 2).
Clinical data, including personal health data, have been collected over the 40 years that humans have flown in space, but data collection has not been done in a systematic way, nor have the data been fully analyzed. A comprehensive health care system for astronauts-both active and retired-should ensure that all data relevant to space travel are collected. Combined with a strategic health care research plan that would enable the analysis of those data, such a system would foster data-driven decisions about health risks, prevention, and mitigation.
"Comprehensive" means that all health care for astronauts is coordinated through an astronaut health care system and covers all periods while the astronaut is active, including the selection, premission, intramission, postmission, and intermission phases. "Comprehensive" also means that there is retrospective as well as prospective collection and analysis of clinical data. The astronaut health care system should include not only a health care component but also health care research and training components. The standard of clinical care for a health care system for astronauts should be equivalent to the best clinical care available on Earth for those problems that occur before and after a mission. The goals of the health care system should be to maximize the astronaut's ability to function as a productive member of the crew while in deep space and to maintain or to restore normal function in the premission and the postmission phases.
Crew health has not received the attention that it must receive to ensure the safety of astronauts on long-duration missions beyond Earth orbit, nor has NASA sufficiently integrated astronaut health care into mission operations.
Currently, there is no comprehensive and inclusive strategy to provide optimum health care for astronauts in support of long-duration missions beyond Earth orbit, nor is there sufficient coordination of health care needs with the engineering aspects of such missions.
An effective health care system is founded on data that are accumulated, analyzed, and used to continuously improve health care for astronauts on future space missions. Inherent in an appropriate health care system is a mechanism that can be used to gather and analyze data relevant to key variables. NASA could have collected and analyzed many more medical data had a comprehensive health care system focused on astronauts been in place and been given the priority and resources that it needed.
Although the equipment and expertise that will be needed to provide health care during future long-duration missions beyond Earth orbit cannot be reliably predicted, a health care system that is data driven and linked to a research strategy will position NASA to better monitor pertinent developments and meet future challenges.
NASA should develop a comprehensive health care system for astronauts for the purpose of collecting and analyzing data while providing the full continuum of health care to ensure astronaut health. A NASA-sponsored health care system for astronauts should
care for current astronauts, astronauts who are in training, and former astronauts, as well as, where appropriate, their families;
cover all premission, intramission, and postmission aspects of space travel;
incorporate innovative technologies and practices-including clinical practice guidelines-into prevention, diagnosis, treatment, and rehabilitation, including provision for medical care during catastrophic events and their sequelae;
be uniform across the international space community and cooperatively developed with the international space community; and
receive external oversight and guidance from prominent experts in clinical medicine.
The goal of NASA-sponsored health care research is, first, to learn how to send and keep humans safely in space and have them return to Earth in good health. In Chapter 7 of this report, the committee recommends a comprehensive health care system that will enable the collection of all relevant clinical information. Such clinical information-the results of natural experiments that reveal common physiological responses to the microgravity environment-may be thought of as epidemiological data. The results of targeted and planned experimentation provide a second element of the health care research plan, broadly construed. Chapter 2 reviews what is known from both epidemiological and targeted research and suggests opportunities for further research.
The principle underlying a health care research strategy is that it have a steadfast, prospective, and methodologically sound approach to the collection of data. Although some work on assessing the efficacies of countermeasures has been done, none has been shown to be effective in reducing the most significant effects of microgravity (bone mineral density loss, muscle loss, and neurovestibular maladaptation). Although artificial and analog environments on Earth have been useful in predicting certain effects of microgravity and isolation on humans, there is no substitute for the microgravity environment for clinical research. The ISS represents the single most important test bed for that research.
Excerpted from Safe Passage Copyright © 2001 by National Academy of Sciences. Excerpted by permission.
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|1||Astronaut Health Beyond Earth Orbit||23|
|2||Risks to Astronaut Health During Space Travel||37|
|3||Managing Risks to Astronaut Health||75|
|4||Emergency and Continuing Care||117|
|5||Behavioral Health and Performance||137|
|6||Exploring the Ethics of Space Medicine||173|
|7||Planning an Infrastructure for Astronaut Health Care||189|
|App. A||Background and Methodology: Letter from Daniel S. Goldin, Administrator, NASA||261|
|App. B: Committee and Staff Biographies||263|