Development of U.S.-Russian medical support procedures for long-duration spaceflight: the NASA-Mir experience.

As the Russian Space Agency and the U.S. National Aeronautics and Space Administration began in the mid-1990s to plan a preliminary cooperative flight program in anticipation of the International Space Station, programmatic and philosophical differences became apparent in the technical and medical approaches of the two agencies. This paper briefly describes some of these differences and the process by which the two sides resolved differences in their approaches to the medical selection and certification of NASA-Mir crewmembers. These negotiations formed the basis for developing policies on other aspects of the medical support function for international missions, including crew training, preflight and postflight data collection, and rehabilitation protocols. The experience gained through this cooperative effort has been invaluable for developing medical care capabilities for the International Space Station.

Thyroid function changes related to use of iodinated water in the U.S. Space Program.

BACKGROUND: The National Aeronautics and Space Administration (NASA) has used iodination as a method of microbial disinfection of potable water systems in U.S. spacecraft and long-duration habitability modules. A review of thyroid function tests of NASA astronauts who had consumed iodinated water during spaceflight was conducted. METHODS: Thyroid function tests of all past and present astronauts were reviewed. Medical records of astronauts with a diagnosis of thyroid disease were reviewed. Iodine consumption by space crews from water and food was determined. Serum thyroid-stimulating hormone (TSH) and urinary iodine excretion from space crews were measured following modification of the Space Shuttle potable water system to remove most of the iodine. RESULTS: Mean TSH significantly increased in 134 astronauts who had consumed iodinated water during spaceflight. Serum TSH, and urine iodine levels of Space Shuttle crewmembers who flew following modification of the potable water supply system to remove iodine did not show a statistically significant change. There was no evidence supporting association between clinical thyroid disease and the number of spaceflights, amount of iodine consumed, or duration of iodine exposure. CONCLUSIONS: It is suggested that pharmacological doses of iodine consumed by astronauts transiently decrease thyroid function, as reflected by elevated serum TSH values. Although adverse effects of excess iodine consumption in susceptible individuals are well documented, exposure to high doses of iodine during spaceflight did not result in a statistically significant increase in long-term thyroid disease in the astronaut population.

Selected contribution: redistribution of pulmonary perfusion during weightlessness and increased gravity.

To compare the relative contributions of gravity and vascular structure to the distribution of pulmonary blood flow, we flew with pigs on the National Aeronautics and Space Administration KC-135 aircraft. A series of parabolas created alternating weightlessness and 1.8-G conditions. Fluorescent microspheres of varying colors were injected into the pulmonary circulation to mark regional blood flow during different postural and gravitational conditions. The lungs were subsequently removed, air dried, and sectioned into approximately 2 cm(3) pieces. Flow to each piece was determined for the different conditions. Perfusion heterogeneity did not change significantly during weightlessness compared with normal and increased gravitational forces. Regional blood flow to each lung piece changed little despite alterations in posture and gravitational forces. With the use of multiple stepwise linear regression, the contributions of gravity and vascular structure to regional perfusion were separated. We conclude that both gravity and the geometry of the pulmonary vascular tree influence regional pulmonary blood flow. However, the structure of the vascular tree is the primary determinant of regional perfusion in these animals.

Design and current status of the longitudinal study of astronaut health.

BACKGROUND: Information has been collected regarding the immediate physiological effects of spaceflight on humans. However, little is yet known regarding long-term effects. The purpose of this paper is to describe the Longitudinal Study of Astronaut Health (LSAH) and report current mortality data. METHODS: All astronauts selected for the United States Space Program are followed from selection throughout their lifetime or until the end of the study. Comparisons are ground-based Johnson Space Center (JSC) employees matched to the astronauts at a 3:1 ratio by sex-specific age and body mass index. They are followed in the same manner as astronauts. Morbidity and mortality data are obtained from medical records supplemented with study questionnaires. Checks for death certificates are made to ascertain death of participants who miss routine examinations. RESULTS: Current cause-specific mortality rates for astronauts selected from 1959 through 1991 are not statistically different from rates for comparison participants for cardiovascular (p = 0.8112), cancer (p = 0.2382), or other disease (p = 0.5040) mortality. Astronauts have a significantly higher mortality rate due to accidents and injuries (p < 0.0001). CONCLUSIONS: Astronauts have a similar risk of death due to chronic diseases as ground-based participants, but are at greater risk for occupational-related accidental death.

A strategic vision for telemedicine and medical informatics in space flight.

This Workshop was designed to assist in the ongoing development and application of telemedicine and medical informatics to support extended space flight. Participants included specialists in telemedicine and medical/health informatics (terrestrial and space) medicine from NASA, federal agencies, academic centers, and research and development institutions located in the United States and several other countries. The participants in the working groups developed vision statements, requirements, approaches, and recommendations pertaining to developing and implementing a strategy pertaining to telemedicine and medical informatics. Although some of the conclusions and recommendations reflect ongoing work at NASA, others provided new insight and direction that may require a reprioritization of current NASA efforts in telemedicine and medical informatics. This, however, was the goal of the Workshop. NASA is seeking other perspectives and views from leading practitioners in the fields of telemedicine and medical informatics to invigorate an essential and high-priority component of the International Space Station and future extended exploration missions. Subsequent workshops will further define and refine the general findings and recommendations achieved here. NASA's ultimate aim is to build a sound telemedicine and medical informatics operational system to provide the best medical care available for astronauts going to Mars and beyond.

Risk of cancer mortality among the Longitudinal Study of Astronaut Health (LSAH) participants.

BACKGROUND: The potential for occupational radiation exposures in the U.S. Space Program makes cancer risk a major health concern. METHODS: The NASA Medical Operations Branch and KRUG Life Sciences Epidemiology Section at the Johnson Space Center (JSC) investigated the rate of cancer mortality among the astronauts and the comparison participants of the Longitudinal Study of Astronaut Health (LSAH). Medical records are maintained by the JSC Flight Medicine Clinic, JSC Occupational Medicine Clinic, and LSAH. Cause of death data from death certificates were reviewed for cancer mortality. These data were compared with cancer mortality data for the general population residing in the Texas Gulf Coast area. RESULTS: The astronauts had a higher age-specific risk of cancer mortality than the comparison group (SMR = 345; 95% CI = 69.5-756.2), but the difference did not reach statistical significance. Both the astronauts and the comparison group had lower age-specific rates than the general population (SMR = 47, 95% CI = 9.6-105.1; SMR = 17, 95% CI = 3.5-37.9, respectively).

Medical considerations for extending human presence in space.

The prospects for extending the length of time that humans can safely remain in space depend partly on resolution of a number of medical issues. Physiologic effects of weightlessness that may affect health during flight include loss of body fluid, functional alterations in the cardiovascular system, loss of red blood cells and bone mineral, compromised immune system function, and neurosensory disturbances. Some of the physiologic adaptations to weightlessness contribute to difficulties with readaptation to Earth's gravity. These include cardiovascular deconditioning and loss of body fluids and electrolytes; red blood cell mass; muscle mass, strength, and endurance; and bone mineral. Potentially harmful factors in space flight that are not related to weightlessness include radiation, altered circadian rhythms and rest/work cycles, and the closed, isolated environment of the spacecraft. There is no evidence that space flight has long-term effects on humans, except that bone mass lost during flight may not be replaced, and radiation damage is cumulative. However, the number of people who have spent several months or longer in space is still small. Only carefully-planned experiments in space preceded by thorough ground-based studies can provide the information needed to increase the amount of time humans can safely spend in space.

Clinical characterization and etiology of space motion sickness.

An inflight, clinically-oriented investigation of SMS was begun on STS-4 and revealed the following: compared to motion sickness on Earth, autonomic signs are significantly different in space motion sickness (SMS) vs. motion sickness (MS) in that sweating is not present, pallor or flushing may be present, and vomiting is episodic, sudden, and brief. Nausea may be present but is more often absent. Onset ranges from minutes to hours, plateaus, and rapidly resolves in 8-72 h with 36 h as average. Postflight reactions have been mild unless deliberately provoked in the early period of re-exposure to gravity. Postflight there is a period of resistance to all forms of motion sickness. There is some evidence for individual reduction in sensitivity on repeated flights. Etiology could not be proven objectively; however, the sensitivity to angular motion, often pronounced in pitch, and theoretical considerations make an intravestibular conflict the most likely cause. Electro-oculogram (EOG), audio-evoked potentials, measurement of fluid shifts, and other studies are inconsistent with a transient vestibular hydrops or increased intracranial pressure as a cause.

Gastrointestinal motility in space motion sickness.

Gastrointestinal (Gl) symptoms in space motion sickness (SMS) are significantly different from those in ordinary motion sickness (MS). Vomiting is sudden, often unexpected, infrequent, never prolonged and usually without nausea. Inflight bowel sounds are absent in those with SMS but present after recovery and in those not affected. Recording and tabulation of sounds was the only technique that could be used as a measure of motility during spaceflight operations. There were 17 subjects, 6 unaffected by SMS, who made ambulatory recordings pre- and inflight. With one exception, all those affected had sharply reduced sounds while those unaffected had increases or moderate reductions. The mechanism of vomiting in SMS appears to be secondary to this ileus in contrast to vomiting in ordinary MS, where the emesis center is thought to be directly triggered by the vestibular system. This ileus appears to be the only consistent and reliable indicator for SMS to date.

Fluid shifts in weightlessness.

Studies of leg volumes in space by multiple girth measurements showed reductions of 1.9 L (12.8% of leg volume) with 1.1 L from the non-dominant leg on Skylab 4. On landing, 65% of postflight leg volume increase was complete at 1.5 h. Measurement of the dominant leg during the equivalent period on Shuttle showed a mean loss of 0.9 L which was 90% complete at 150 min. Postflight increases were 87% complete at 1.5 h postlanding. Mass measurements during and after Skylab 4 showed a loss of 2.5 kg over the first 4 d on-orbit with a gain of 2.7 kg over the first 4 d of recovery. These changes are assumed to be tissue fluids secondary to changes in hydrostatic pressures and are much greater than those seen in bed rest. Rate and magnitude of inflight and postflight changes have significant operational impact.

Electronystagmography and audio potentials in space flight.

Beginning with the fourth flight of the Space Transport System (STS-4), objective measurements of inner ear function were conducted in near-zero G conditions in earth orbit. The problem of space motion sickness (SMS) was approached much like any disequilibrium problem encountered clinically. However, objective testing techniques had built-in limitations superimposed by the strict parameters inherent in each mission. An attempt was made to objectively characterize SMS, and to first ascertain whether the objective measurements indicated that this disorder was of peripheral or central origin. Electronystagmography and auditory brain stem response recordings were the primary investigative tools. One of the authors (W.E.T.) was a mission specialist on board the orbiter Challenger on the eight shuttle mission (STS-8) and had the opportunity to make direct and personal observations regarding SMS, an opportunity which has added immeasurably to our understanding of this disorder. Except for two abnormal ENG records, which remain to be explained, the remaining ENG records and all the ABR records made in the weightless environment of space were normal.

[Biomedical results of the Space Shuttle Orbital Flight Test Program]. / Rezul'taty mediko-biologicheskikh issledovanii v ispytatel'nykh orbital'nykh poletakh po programme "Speis Shattl".

On July 4, 1982 the Space Shuttle Columbia landed at Edwards Air Force Base, California, thus successfully completing the fourth and last in a series of Orbital Flight Tests (OFT) of the Space Transportation System (STS). The primary goal of medical operation support for the OFT was to assure the health and well-being of flight personnel during all phases of the mission. To this end, the crew health status was evaluated preflight, inflight and postflight. Biomedical flight test requirements were completed in the following areas: physiological adaptation to microgravity, cabin acoustical noise, cabin atmospheric evaluation, radiation dosimetry, crew exercise equipment evaluation and a cardiovascular deconditioning countermeasure assessment.

[Principles of NASA longitudinal medical studies]. / Printsipy perspektivnykh meditsinskikh issledovanii NASA.

This paper describes approaches to longitudinal studies of the changes in the health status of the US astronauts. The methods include acquisition and analysis of biomedical data accumulated in one and repeated space missions, detection of potential occupational diseases inflight and evaluation of mortality cases associated with them. It is suggested to use pilots and flight controllers as controls. It is indicated that annual physical examinations can be an important source of relevant scientific information.

Biomedical results of the Space Shuttle orbital flight test program.

On July 4, 1982, the Space Shuttle Columbia landed at Edwards Air Force Base, CA, thus successfully completing the fourth and last in a series of Orbital Flight Tests (OFT) of the Space Transportation System (STS). The primary goal of medical operations support for the OFT was to assure the health and well-being of flight personnel during all phases of the mission. To this end, crew health status was evaluated preflight, inflight, and postflight. Biomedical flight test requirements were completed in the following areas: physiological adaptation to microgravity, cabin acoustical noise, cabin atmospheric evaluation, radiation dosimetry, crew exercise equipment evaluation, and a cardiovascular deconditioning countermeasure assessment.

Concepts for NASA longitudinal health studies.

Clinical data collected from a 15-year study of the homogeneous group of pre-Shuttle astronauts have revealed no significant long-term effects from spaceflight. The current hypothesis suggests that repeated exposures to the space environment in the Shuttle era will similarly have no long-term health effects. However, a much more heterogeneous group of astronauts and non-astronaut scientists will fly in Shuttle, and data on this group's adaptation to the space environment and readaptation to Earth are currently sparse. In addition, very little information is available concerning the short- and long-term medical consequences of long duration exposure to space and subsequent readaptation to the Earth environment. In this paper, retrospective clinical information on astronauts is reviewed and concepts for conducting epidemiological studies examining long-term health effects of spaceflight on humans, including associated occupational risks factors, are presented.

A new technique for measuring intestinal calcium absorption in the rat.

A double-isotope technique that does not necessitate urine and fecal collections but requires only the extraction of the incisor teeth for isotopic analysis has been devised. A precalibrated dose of 45Ca in solution with stable carrier calcium is administered to the rat orally. An intraperitoneal injection delivers a precalibrated dose of 47Ca in isotonic saline. The ratio of the percentage uptake of the two radionuclides in the incisor tooth is equal to the fraction of the 45Ca and, therefore, the calcium absorbed by the gut. The fraction of calcium absorbed by 5-mo-old rats, as determined by collection and measurement of excreta, was found to be 39.1%. The ratio of uptake of the two calcium radionuclides in the incisor teeth yields an absorption measurement of 38.8%, nonsignificantly different from the value obtained from the excretion data. The measurement of radiocalcium uptake in the incisor tooth affords one an accurate in vivo determination of intestinal calcium absorption without the collection of excreta or multiple blood sampling.