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Safe Passage: Astronaut Care for Exploration Missions Landing of the space shuttle Discovery at the Kennedy Space Center on June 12, 1998, marking the end of STS-91, the final space shuttle-Mir docking mission, and 812 days of continuous U.S. presence in Earth orbit. NASA image.
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Safe Passage: Astronaut Care for Exploration Missions 1 Astronaut Health Beyond Earth Orbit …if any man could arrive at the exterior limit [deepest space],…he would see a world [universe] beyond [the Earth]; and, if the nature of man could sustain the sight, he would acknowledge that this other world [universe] was the place of the true heaven and the true light and the true earth. Socrates, c400 B.C. (from Plato’s Dialog Phaedo [109e]) BACKGROUND For more than three decades the U.S. space community has been planning to send humans on exploration-class missions to Mars (Burrows, 1998). In the post-Apollo space mission era, this would be the next “giant leap for mankind” and the first step toward human exploration of the solar system. Although Mars is a cold and inhospitable place with an extreme environment and an atmosphere with high levels of carbon dioxide that cannot support human life, it is also the nearest and most Earth-like planet in the solar system. Mars has seasons, polar ice caps, mountains and canyons, volcanoes, and evidence of ancient rivers and lakes. It is the most accessible body among the planets and moons in the solar system where a sustained human presence is believed to be possible (Hoffman and Kaplan, 1997).
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Safe Passage: Astronaut Care for Exploration Missions At the time of the public release of this report, there are no concrete plans to land humans on Mars; that event is more than a decade in the future. However, much of the engineering research and logistical planning needed to make such a mission a reality has been under way for years and continues today in many fields and on many fronts. The most recent demonstration of the human insatiable desire to explore and conquer the “outer limits” of habitability was the ascent on October 31, 2000, of Expedition 1 from a launchpad in Kazakhstan, which carried the first international astronaut-cosmonaut contingent to commence habitation of the International Space Station and a permanent human presence in Earth orbit. Since 1991 the U.S. National Aeronautics and Space Administration (NASA) has been studying how to make human exploration of Mars a “feasible undertaking for the space-faring nations of Earth” (Hoffman and Kaplan, 1997, Section 1, p. 3). The agency published the cumulative results of its thinking in Human Exploration of Mars: The Reference Mission of the NASA Mars Exploration Study Team (Hoffman and Kaplan, 1997). The report characterized the human exploration of Mars as a goal that “currently lies at the ragged edge of achievability” (Hoffman and Kaplan, 1997, Section 1, p. 5). Human exploration of this scope requires optimum functioning of both spacecraft and astronauts—of both the engineering and the human components. Failure of either could result in mission failure. Success thus requires close integration of both throughout the design, planning, and implementation process. Of all the challenges that such missions beyond Earth orbit imply, the most daunting will be to provide for the health and safety of astronauts who venture beyond Earth’s orbit for the first time. Their well-being will depend in part on future advances in medicine and engineering (SSB and NRC, 1996, 1998a,d). It will also depend upon biologically inspired technologies under development, such as nanosensors that can monitor health status, and quantum advances in informatics and robotics. On the surface of Mars, astronauts will rely for safety on advance teams of so-called smart robots that can “do the dangerous work and keep our astronauts out of harm’s way” (Goldin, 1999). Keeping astronauts out of “harm’s way” also means designing a health care system that is contemporary, practical, and portable. The system must be grounded in clinical evidence, yet it must take into account both risks that are known and predictable and those that have yet to be determined. Finally, the health care system must work in a setting that is far more remote and far more extreme in physical and other environmental conditions than
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Safe Passage: Astronaut Care for Exploration Missions anything modern health planners, practitioners, and patients have yet encountered, where neither timely resupply nor timely return to the point of departure will be possible. How to proceed toward designing a contemporary, practical, and portable health care diagnosis and delivery system to successfully meet this future necessity is the subject of this report. The challenge of designing such a system is underscored by the observations made thus far: that space travel is severely debilitating to humans in many ways (SSB and NRC, 1998a, 2000). Recovery from these extreme physiological changes is uncertain and may be incomplete at best. Moreover, NASA believes that simply landing humans on Mars and returning them safely to Earth is not enough. In fact, a safe round-trip without meaningful surface exploration would be regarded as a minimally successful space mission (Hoffman and Kaplan, 1997). Astronauts will need to be strong and healthy to explore the Martian surface and investigate the possibilities for human colonization. For this reason, the Hoffman and Kaplan report states that humans are the most valuable mission asset for Mars’s exploration and cannot become the weakest link. Any mission to Mars or another distant point beyond Earth orbit involving humans will likely be international in character and will likely include individuals from some combination of 13 countries, and because of current propulsion designs, the mission would be launched from the International Space Station or a similar orbiting platform. Crewmembers must arrive on Mars safely and in good health after a lengthy period of travel, probably 5 to 6 or more months (Figure 1–1). After the journey to Mars, astronauts must be mentally and physically prepared to spend many months on the Martian surface in their spacecraft or ancillary habitation structure and to function productively for all of that time. Crewmembers must be trained and equipped to deal en route, on Mars, and during their return with medical emergencies such as an abscessed tooth, a fractured limb, or life-threatening conditions with no possibility for emergency evacuation. Spacecraft crews cannot expect to rely totally on the presence of physician-astronauts, who, if part of the crew, may themselves become sick or disabled. Finally, advice and support from mission controllers on Earth will be delayed, which is in contrast to today’s almost instantaneous communication between mission controllers and space crews in Earth orbit. An astronaut’s medical emergency could quickly turn into a tragedy if crewmembers were forced to depend on Mars-to-Earth round-trip audio transmission times of 20 to 40 minutes depending upon how far the spacecraft is from Earth.
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Safe Passage: Astronaut Care for Exploration Missions FIGURE 1–1 Trajectory of a human mission to Mars in 2014. Source: Charles, 2000. Despite such constraints, the medical goal on exploration-class space missions is to provide health care of sufficiently high quality so that crewmembers, once their exploratory mission is completed, can reasonably anticipate a safe return to Earth and, subsequently, healthy and productive terrestrial lives. HEALTH RISKS OF SPACE TRAVEL To date, some 350 persons have “flown” in space. Of these, most have flown for less than 30 days. Two cosmonauts, Vladimir Titov (366 days) and Valeri Poliakov (400 days), each spent more than a year in space, and U.S. astronaut Shannon Lucid traveled in space for 188 days. From this limited experience, it is clear that the health risks of prolonged exposure to microgravity and the confining environment of the spacecraft during space travel can be profound. Even 30 days in space can induce dramatic physiological changes. Some are minor and temporary, such as facial edema and an increase in height of up to an inch (Nicogossian et al., in press). Others are severe and may not always be reversible. For example, bone mineral
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Safe Passage: Astronaut Care for Exploration Missions density appears to decrease at an average rate of about 1 percent a month during exposure to microgravity, while recovery on Earth appears to proceed at a slower rate (Vico et al., 2000). When the human skeleton is no longer exposed to gravity, a significant loss of bone mineral density occurs as a result of demineralization. The amount of bone demineralization varies; one Skylab astronaut lost nearly 8 percent of the mineral density in his calcaneus after 84 days in space, and a Russian cosmonaut aboard Mir reportedly lost up to 19 percent mineral density at the same site after 140 days (Vico et al., 2000). Thus, a Mars mission that exposes astronauts to microgravity for up to 3 years could theoretically result—if untreated—in a loss of bone mineral density of 50 percent or more at several structurally important skeletal sites. “Microgravity-induced bone loss—will it limit human space exploration?” This title of an editorial in The Lancet (Holick, 2000) asks a rhetorical question, for the loss of bone mineral density on long-duration space missions is one of the most serious and intractable health risks identified so far, and until this physiological effect of microgravity is resolved, a mission to Mars is unlikely to be undertaken with humans. So far, preventive interventions that NASA refers to as “countermeasures” have been only marginally effective (“countermeasure” is NASA’s designation for preventive and therapeutic interventions before or during space missions) (Lane and Schoeller, 2000). If the loss of bone mineral density as a result of space travel cannot be surmounted by biomedical means, an engineering solution, for example, artificial gravity or some other means of integration of engineering and biology, will be necessary. Radiation exposure is perhaps an even greater risk from travel beyond Earth orbit. Radiation beyond Earth’s orbit is substantially different from the ionizing radiation to which humans are generally exposed on Earth because of the presence beyond Earth’s orbit of high-energy charged solar and cosmic particles from deep space, ranging from protons to iron nuclei (SSB and NRC, 1996, 1998a,d, 2000). Little is presently known about the potential interaction of this nonionizing form of radiation with the DNA, cells, and tissues of astronauts (SSB and NRC, 1996, 1998a,d, 2000). There are no data on the effects of terrestrial exposure to such protons and high-atomic-number, high-energy particles that flood space beyond Earth orbit because of the current absence of experimental facilities on Earth. Furthermore, there is no way to predict when solar outbursts with their higher levels of radiation will occur (SSB and NRC, 1996, 1998a,d) and no current practical way to protect spacecraft crewmembers from them.
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Safe Passage: Astronaut Care for Exploration Missions Until the radiation hazards to astronauts can be controlled or otherwise mitigated by physical shielding, a 1998 National Research Council report states, long-duration space travel should be postponed (SSB and NRC, 1998a). Even if an effective physical radiation shield is developed, it in no way diminishes the need for clinical study, including monitoring of crewmembers’ exposures, long-term medical follow-up, and the development of preventive medical treatments to make astronauts more resistant to deep space-induced radiation damage. The anticipated cumulative time-dependent effects that both bone mineral density loss and radiation are anticipated to exert, furthermore, emphasize the need to develop alternative propulsion systems to decrease space travel time and the effects of microgravity and radiation from deep space. Long-duration space travel can also be expected to pose risks of psychological and social stresses because of isolation, confinement, and living in cramped quarters for long periods of time. Without significant engineering improvements to the design of the spacecraft environment so that it is more bio compatible, there will likely be high noise levels, less than optimal light, and diminished privacy. In the view of some experts, these and other psychological stresses could turn out to be the most worrisome risk of all to astronaut health (SSB and NRC, 1998a, 2000). Habitability—or, more correctly, biocompatibility—thus must be an important initial consideration in spacecraft design. Astronaut health requires a continuum of preventive, therapeutic, and rehabilitative care on the ground, during space travel, and upon the return from space travel. The continuum includes normal health maintenance and care for the physiological adaptations that humans experience as a result of the extreme environment of space (see Chapter 2). Furthermore, it must address a large variety of the minor and major medical problems, including psychiatric and behavioral health problems, and surgical problems that can develop among members of a group of individuals over extended periods of time in normal and extreme terrestrial environments (astronauts in training and between missions) and during extended periods in space beyond Earth orbit, which is the particular focus of this report (see Chapters 3, 4, and 5). Although the preventive and rehabilitative aspects of health care are of utmost importance to maintaining a healthy, active astronaut corps, this chapter focuses on principles of health care during future long-duration space travel and habitation, for example, during exploration-class missions to Mars or colonization of Earth’s moon. Other components of the continuum of astronaut health care before, during, and after space travel are
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Safe Passage: Astronaut Care for Exploration Missions covered in depth in the current report in chapters on behavioral health (Chapter 5), ethics (Chapter 6), and a comprehensive health care program for astronauts (Chapter 7). Travel into deep space beyond Earth orbit involves many unique and hazardous elements: Isolation. Great distances preclude timely evacuation and a return to Earth for health care. Therefore, the crew must be prepared to deal in flight with diverse medical situations ranging from minor cuts to death. Limited resources. The spacecraft is unable to carry elements available on Earth because of storage space, power, and weight limitations. Closed environment. The spacecraft has a closed life-support system and cramped working and living quarters. Space-specific hazards. The space environment lacks gravity and contains damaging radiation. Astronauts are a selected healthy population with low percentages of disease occurrence. However, it is still necessary to prepare for the worst case such as major trauma, appendicitis, obstructive cholelithiasis, acute myocardial infarction or disabling arrhythmia, stroke, pancreatitis, and death. Earth-based health problems will not be left behind and, thus, cannot be overlooked by relying on chance. CHARGE TO THE COMMITTEE With this as background, NASA in 1999 formally asked the Institute of Medicine (IOM) to “create a vision” for health care for astronauts traveling beyond Earth orbit. In a letter (see Appendix A) to IOM President Kenneth I.Shine, NASA Administrator Daniel S.Goldin pointed out that efforts to develop a more capable medical care delivery system in space had been internal to NASA. The focus had been on prevention, reflected in “strict” astronaut selection standards and close monitoring of their health status. So far that approach has succeeded, as astronauts have been free of major health problems during space missions, but spaceflights have been short and emergency evacuations from spacecraft in low Earth orbit have been possible. Evacuation and return to Earth will not be the case during future long-duration space missions beyond Earth orbit. NASA requested IOM’s assistance in “evaluating our current medicalcare system and recommending the type of infrastructure we will need to
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Safe Passage: Astronaut Care for Exploration Missions develop to support long-duration missions, including interplanetary travel, in which timely evacuation of crewmembers will not be an option. Medicalcare provider training, specialty mix, nonmedical crewmember skills, use of advanced technology, surgical/intensive care capability in space, rehabilitation approaches to cope with exposures to gravitational fields following exposures to microgravity, psychological/human factors challenges and use of robotics for health monitoring, education, and possible surgery are examples of the types of issues we would like you to address. We would also like you to consider the use of analog environments, such as remote Antarctic stations, for training and research. Ethical considerations in the face of limited medical-care capability are also important issues that need examination” (Goldin, 1999a). IOM asked experts in health sciences research and clinical medicine to address the health risks, medical needs, and patient care dilemmas that are likely to arise during long-duration space travel. The committee’s charge is shown in Box 1–1. THE COMMITTEE’S STUDY OF HEALTH CARE FOR ASTRONAUTS TRAVELING BEYOND EARTH ORBIT The committee has focused on the development of principles and general and developing practices for provision of the best possible health care to astronauts. This report covers the continuum of health care, from preventive services before departure, to treatment of conditions that might conceivably arise during long-duration space travel beyond Earth orbit, to health care on Mars and during the return to Earth. It also discusses the need for restorative and rehabilitative services for astronauts upon their return to Earth. On the first exploration-class mission to Mars, expected to last nearly 3 years, the goal will be to keep the astronauts healthy, productive, and reasonably comfortable in an environment that is almost unimaginably distant and unforgiving. The IOM Committee on Creating a Vision for Space Medicine During Travel Beyond Earth Orbit envisions a health care system for astronauts that can deliver high-quality medical care, extensive psychological support, and excellent (albeit basic) surgical services to a special population of astronaut-patients who are unusually fit but also uniquely vulnerable. In the course of the committee’s information gathering and data analysis five elements emerged as critical to the committee in addressing its charge. Risks to astronauts’ health The committee sought to understand the
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Safe Passage: Astronaut Care for Exploration Missions BOX 1–1 Charge to the Committee Conduct an independent assessment of the current status of scientific knowledge, paying particular attention to pharmaceutical and technology principles, to provide optimal health care for astronauts during and upon return from spaceflights beyond Earth orbit. Evaluate the most promising directions for the future of scientific progress in space medicine, which will include (1) identifying advances anticipated in related fields that might prove to be beneficial for medical practice in space and (2) exploring opportunities for finding innovative terrestrial medical care practices that have the potential to advance the theory and practice of space medicine. Recommend a strategy at the national and international levels for medical care in space that holds the greatest promise for preventing and treating health conditions expected to develop during long-term spaceflight. The committee will provide recommendations to NASA regarding the most promising avenues for medical care compatible with the adaptability status of the crew. The committee will develop recommendations regarding the direction of future medical care investments to attract interest from scientists to this area of health science and medicine. Suggest the most effective ways for NASA to address the priority areas in achieving this strategy. Assist in developing collaborative relationships between NASA and clinically prominent experts at the national level to advocate and guide the growth of space medicine, including the development of clinical practice guidelines as appropriate. Make recommendations on the distinctive contributions that could be made by the context of clinical areas supported by NASA, the federal agencies that perform health care (e.g., the U.S. Department of Veterans Affairs, the U.S. Department of Defense, and the Federal Aviation Administration), the pharmaceutical and biomedical device industries, and other organizations and agencies as appropriate. Adopt and retain a flexible approach to this task, understanding the dynamic and changing nature of emerging knowledge in fields related to space medicine and in recognition of evolving needs of the space medicine community. risks to human health during space travel, the extent to which astronauts are included in decision making about acceptable risks, and the extent to which society is informed regarding the risks and the possibility of a disaster. Astronauts as research subjects Certain data must be collected, analyzed, shared, and used to make conditions safer and better for those who follow. At the same time, what assurances do astronauts receive that any research in which they are required to participate is not only relevant but also essential? Are they informed of the risks and potential benefits? Clinical research High-quality health care for astronauts, as for any
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Safe Passage: Astronaut Care for Exploration Missions individual, must be grounded in an evidence base, that is, documented and analyzed clinical observations supplemented by designed clinical research. The committee examined NASA’s data collection and strategic plan for clinical research, the extent to which its research awards are open to the broadest possible scientific audience, the degree of hypothesis-driven research, and the degree of collaborative relationships. To what extent is the data-gathering effort ongoing, rigorous, prospective, and methodologically sound? The committee examined the potential of the International Space Station as an orbiting clinical research laboratory to focus on better understanding the effects of microgravity on humans. Astronaut health care The committee evaluated the general continuum of health care that includes premission, intramission, and postmission preventive medical and dental care and health education as well as the traditional forms of medical, surgical, and behavioral medical care focused on the unique environment of extended periods in an isolated and remote, self-contained “capsule.” Crew selection Selection of the crew for the first mission beyond Earth orbit will be critically important. The committee focused its attention on group and individual characteristics, selection, and training. These are a few of the areas the committee sought to understand in fulfilling its charge to provide a vision for space medicine during travel beyond Earth orbit. In going about its work, the IOM committee held five information-gathering meetings over the course of 15 months (October 1999 through December 2000), with one additional closed meeting held in January 2001 for discussion of the committee’s conclusions and recommendations. At least a portion of each of the first five meetings was open to the public. The committee’s first meeting featured presentations by officials from NASA headquarters in Washington, D.C., and the Johnson Space Center in Houston, Texas (see Appendix A). The committee’s second meeting, in February 2000, incorporated a site visit to the Johnson Space Center and included briefings by some 30 NASA clinicians and researchers in space medicine (see Appendix A). Two of the committee’s meetings included workshops open to the public. The first workshop, held in Washington, D.C., in April 2000, focused on the dental health needs of astronauts on long-duration space missions (see Appendix A). The second workshop, held in Woods Hole, Massachusetts, in July 2000, focused on what has been learned about
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Safe Passage: Astronaut Care for Exploration Missions maintaining the health and well-being of scientists and explorers on duty in remote and extreme environments for long periods of time (see Appendix A). The July workshop also included a panel discussion and a question-and-answer session with five physician-astronauts. This report extends the findings and recommendations of earlier National Research Council reports that are focused on a variety of basic biomedical concerns and that were developed at the request of NASA and published in 1987, 1996, 1998, and 2000 (SSB and NRC, 1987, 1996, 1998a, 2000). It extends the findings and recommendations to the issues that directly influence the well-being and delivery of health care to astronauts during space travel beyond Earth orbit. The current committee and its report differ substantially from previous National Research Council committees and reports in that the committee focused on human clinical research and astronaut health care. Each earlier report assessed the then-current state of health sciences research that appeared to be of importance to the future development of space medicine. The reports laid out long-term strategies for future biomedical research. The current report goes to the next level by focusing on principles that can be used to build a health care system that ensures the health and safety of humans during long-duration missions beyond Earth orbit. The earlier reports also cautioned, as this one does, that substantial reductions in anticipated risks must be demonstrated before humans are sent on missions beyond Earth orbit. Professionals in engineering and biomedicine must work together to make missions beyond Earth orbit succeed. In extending that caution, this committee report suggests principles and directions for space medicine (see Box 1–2 for the definition of space medicine that the committee used as its reference) that NASA should consider in its role as a leader in developing this new frontier to provide the optimal health care for individuals who will be embarking on and returning from missions beyond Earth orbit.
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Safe Passage: Astronaut Care for Exploration Missions BOX 1–2 What Is Space Medicine in Reference to Developing a Vision and Strategy for Astronaut Health? For the purpose of the present study the committee has considered space medicine to be a developing area of health care that has roots in aerospace medicine but that is focused on the health of individuals so that they can perform in and return in good health from increasingly distant extreme space environments, for example, from short-duration space capsule flights, space shuttle flights, missions to the Moon, long-term Earth-orbiting space station missions, and in the next stages, exploration-class missions beyond Earth orbit, including missions involving planetary colonization. This view of space medicine is consistent with NASA’s, in which operational space medicine is defined as “a distinct discipline of medicine focused on the unique challenges of human spaceflight and the medical risk management of associated hazards” (from the Mission Statement of the Medical Operations Branch, Johnson Space Center, 2000). Presently, the specialty of aerospace medicine includes aviation medicine and space medicine. There are approved residency programs as well as recognition by all regulatory agencies and the American Medical Association. The Aerospace Medical Association is the established professional home providing scientific meetings as well as a monthly specialty journal (Aviation Space Environmental Medicine) for all practitioners and scientists whether in aviation or space medicine. The understanding and definition of space medicine will change as space travel and medicine change. Those changes must continually be kept in mind as visions and strategies for space medicine and astronaut health and safety evolve.
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Safe Passage: Astronaut Care for Exploration Missions NOTES
Representative terms from entire chapter: