Invited review: gender issues related to spaceflight: a NASA perspective.

This minireview provides an overview of known and potential gender differences in physiological responses to spaceflight. The paper covers cardiovascular and exercise physiology, barophysiology and decompression sickness, renal stone risk, immunology, neurovestibular and sensorimotor function, nutrition, pharmacotherapeutics, and reproduction. Potential health and functional impacts associated with the various physiological changes during spaceflight are discussed, and areas needing additional research are highlighted. Historically, studies of physiological responses to microgravity have not been aimed at examining gender-specific differences in the astronaut population. Insufficient data exist in most of the discipline areas at this time to draw valid conclusions about gender-specific differences in astronauts, in part due to the small ratio of women to men. The only astronaut health issue for which a large enough data set exists to allow valid conclusions to be drawn about gender differences is orthostatic intolerance following shuttle missions, in which women have a significantly higher incidence of presyncope during stand tests than do men. The most common observation across disciplines is that individual differences in physiological responses within genders are usually as large as, or larger than, differences between genders. Individual characteristics usually outweigh gender differences per se.

Gynecological and reproductive issues for women in space: a review.

Women have been an integral part of United States space crews since the initial flight of Dr. Sally Ride in 1983, and a total of 40 women have been selected as U.S. astronauts. This article examines the reproductive and gynecological aspects of selecting, training, medically certifying, and flying women in space. Gynecological data from the astronaut selection cycles in 1991 to 1997 are reviewed. In addition, the reproductive implications of delaying childbearing for a career as an astronaut and the impact of new technology such as assisted reproductive techniques are examined. The reproductive outcomes of U.S. female astronauts after spaceflight are also presented. Because women have gained considerable operational experience on the Shuttle and Mir, the unique operational considerations for preflight certification, menstruation control and hygiene, contraception, and urination are discussed. Medical and surgical implications for women on long-duration missions to remote locations are still evolving, and enabling technologies for health care delivery are being developed. There has been considerable progress in the development of zero-gravity surgical techniques, including laparoscopy, thoracoscopy, and laparotomy. The concepts of prevention of illness, conversion of surgical conditions to medically treatable conditions, and surgical intervention for long-duration spaceflights are explored in detail. There currently are no operational gynecological or reproductive constraints for women that would preclude their successful participation in the exploration of our nearby solar system.

Specialty competencies for residents in aerospace medicine.

BACKGROUND: The American College of Preventive Medicine (ACPM), with sponsorship from the Health Resources Administration (HRSA), has published core competencies that are common to all preventive medicine residencies-aerospace medicine (ASM), occupational medicine (OM), and general preventive medicine/public health (GPM/PH). Further development of specialty area competencies for ASM residents was addressed by a working group comprised of representatives from each of the four ASM residency programs. METHODS: Representatives from the U.S. Air Force School of Aerospace Medicine, Wright State University, University of Texas Medical Branch-Galveston, and the Naval Operational Medicine Institute convened to develop a set of broad competency statements for ASM residents that would encompass the breadth of ASM residency training as it is currently provided in the U.S. RESULTS: A listing of six ASM resident competencies, with supporting skill sets, are presented. In combination with the ACPM core competencies, the ASM resident competencies represent a refocusing of educational objectives on skills attainment. CONCLUSIONS: The ASM resident competencies identify the capabilities of graduating ASM residents as distinct from OM and GPM/PH residents. At the same time, they are broad enough to permit specific areas of emphasis (e.g., military, civil, or space) to be pursued within the various ASM residencies. This represents the first successful attempt to draft a consolidated statement of educational objectives that has universal acceptance and applicability across all U.S. aerospace medicine residencies.

Managing space motion sickness.

Space motion sickness is a well-recognized problem for space flight and affects 73% of crewmembers on the first 2 or 3 days of their initial flight. Illness severity is variable, but over half of cases are categorized as moderate to severe. Management has included elimination of provocative activities and delay of critical performance-related procedures such as extra-vehicular activity (EVA) or Shuttle landing during the first three days of missions. Pharmacological treatment strategies have had variable results, but intramuscular promethazine has been the most effective to date with a 90% initial response rate and important reduction in residual symptoms the next flight day. Oral prophylactic treatment of crewmembers with difficulty on prior flights has had mixed results. In order to accommodate more aggressive pharmacologic management, crew medical officers receive additional training in parenteral administration of medications. Preflight medication testing is accomplished to reduce the risk of unexpected performance decrements or idiosyncratic reactions. When possible, treatment is offered in the presleep period to mask potential treatment-related drowsiness. Another phenomenon noted by crewmembers and physicians as flights have lengthened is readaptation difficulty or motion sickness on return to Earth. These problems have included nausea, vomiting, and difficulty with locomotion or coordination upon early exposure to gravity. Since landing and egress are principal concerns during this portion of the flight, these deficits are of operational concern. Postflight therapy has been directed at nausea and vomiting, and meclizine and promethazine are the principal agents used. There has been no official attempt at prophylactic treatment prior to entry. Since there is considerable individual variation in postflight deficit and since adaptation from prior flights seems to persist, it has been recommended that commanders with prior shuttle landing experience be named to flights of extended duration.

Musculoskeletal injury review in the U.S. space program.

Astronauts in NASA's space program are expected to remain fit to complete their on-orbit tasks and to function effectively in the event of contingency operations. Due to the generally self-directed exercise program and reliance on competitive sports and running for conditioning, plus limited emphasis on training techniques and rehabilitation, there have been a surprising number of orthopedic injuries and surgeries in this small adult population. This article examines the orthopedic injury history of U.S. astronauts during the period from 1987-95. The type of injury, activity involved, and subsequent surgical interventions are cataloged. There were a total of 26 fractures, 36 serious ligament, cartilage, or soft tissue injuries, and 28 orthopedic surgical procedures in this adult group with a mean astronaut corps size of only 94. Women accounted for 16% of the study population but accounted for only 1 of 28 surgical procedures. Knee injuries required surgical intervention 19 times. Running, skiing, and basketball were most frequently associated with injuries. The descriptive data regarding frequency of adverse events and activity associated with injuries is presented. These injury patterns are analyzed and suggestions made for future improvement, including decreased reliance on running and competitive athletics for conditioning, improved personal fitness training preflight, and coordinated rehabilitation postflight. Also recommended is the use of a lap pool for preflight total body fitness training, since swimming provides conditioning to those muscle groups used during spaceflight, and for variably weighted gravity rehabilitation postflight.

Measurement of the intensity and phase of ultraweak, ultrashort laser pulses.

We show that frequency-resolved optical gating combined with spectral interferometry yields an extremely sensitive and general method for temporal characterization of nearly arbitrarily weak ultrashort pulses even when the reference pulses is not transform limited. We experimentally demonstrate measurement of the full time-dependent intensity and phase of a train of pulses with an average energy of 42 zeptojoules (42 x 10(-21) J), or less than one photon per pulse.

Comparison of treatment strategies for Space Motion Sickness.

Treatment strategies for Space Motion Sickness (SMS) were compared using the results of postflight oral debriefings. Standardized questionnaires were administered to all crewmembers immediately following Space Shuttle flights by NASA flight surgeons. Cases of SMS were graded as mild, moderate, or severe based on published criteria, and medication effectiveness was judged based on subjective reports of symptom relief. Since October 1989, medication effectiveness is reported inflight through Private Medical Conferences with the crew. A symptom matrix was analyzed for 19 crewmembers treated with oral combination of scopolamine and dextroamphetamine (scopdex) and 15 crewmembers treated with promethazine delivered by intramuscular i.m. or suppository routes. Scopdex has been given preflight as prophylaxis for SMS, but analysis showed delayed symptom presentation in 9 crewmembers or failed to prevent symptoms in 7. Only 3 crewmembers who took scopdex had no symptoms inflight. Fourteen out of 15 crewmembers treated with i.m. promethazine and 6 of 8 treated with promethazine suppositories after symptom development had immediate (within 1-2 h) symptom relief and required no additional medication. There were no cases of delayed symptom presentation in the crewmembers treated with promethazine. This response is in contrast to untreated crewmembers who typically have slow symptom resolution over 72-96 h. We conclude that promethazine is an effective treatment of SMS symptoms inflight. NASA policy currently recommends treating crewmembers with SMS after symptom development, and no longer recommends prophylaxis with scopdex due to delayed symptom development and apparent variable absorption of oral medications during early flight days.

Treatment efficacy of intramuscular promethazine for space motion sickness.

Intramuscular promethazine and its efficacy in the treatment of Space Motion Sickness (SMS) were evaluated using standardized questions administered during postflight debriefings to crewmembers immediately after their first Shuttle flight. Space Motion Sickness was graded as none, mild, moderate, or severe, based on published criteria. Immediate symptom relief (within 1-2 h) was evaluated by subjective reports; medication efficacy was based on scores derived from the four most frequently reported symptoms of SMS: nausea, vomiting, loss of appetite, and stomach awareness. Scores were given for each symptom, mild = 1, moderate = 2, and severe = 3, and added for a total score for each flight day. Following intramuscular (IM) promethazine on flight day 1, the scores were used to determine if the crewmembers were "sick" or "not sick" on flight day 2. On the basis of the scoring criteria, any subject with a score adding to greater than three, with any severe symptom, or with vomiting was defined as "sick." The comparison showed that 25% of crewmembers treated with IM promethazine were "sick" on flight day 2, compared to 50% of crewmembers who did not receive promethazine (p = 0.046). Of crewmembers treated with IM promethazine, 90% reported immediate symptom relief as well. Untreated crewmembers typically have slow symptom resolution over 72-96 h, and those treated with oral scopolamine/dextroamphetamine show delayed symptom development. This study suggests that intramuscular promethazine is an effective treatment for SMS and merits continued use and further controlled investigations.

Comparison of treatment strategies for Space Motion Sickness.

Treatment strategies for Space Motion Sickness were compared using the results of postflight oral debriefings. Standardized questionnaires were administered to all crewmembers immediately following Space Shuttle flights by NASA flight surgeons. Cases of Space Motion Sickness were graded as mild, moderate or severe based on published criteria, and medication effectiveness was judged based on subjective reports of symptom relief. Since October 1989, medication effectiveness is reported inflight through Private Medical Conferences with the crew. A symptom matrix was analyzed for 19 crewmembers treated with an oral combination of scopolamine and dextroamphetamine (scopdex) and 15 crewmembers treated with promethazine delivered by intramuscular (IM) or suppository routes. Scopdex has been given preflight as prophaxis for Space Motion Sickness but analysis showed delayed symptom presentation in 9 crewmembers or failed to prevent symptoms in 7. Only three crewmembers who took scopdex had no symptoms inflight. Fourteen out of 15 crewmembers treated with IM promethazine and 6 of 8 treated with promethazine suppositories after symptom development had immediate (within 12 h) symptom relief and required no additional medication. There were no cases of delayed symptom presentation in the crewmembers treated with promethazine. This response is in contrast to untreated crewmembers who typically have slow symptom resolution over 72-96 h. We conclude that promethazine is an effective treatment of Space Motion Sickness symptoms inflight. NASA policy currently recommends treating crewmembers with Space Motion Sickness after symptom development, and no longer recommends prophylaxis with scopdex due to delayed symptom development and apparent variable absorption of oral medications during early flight days.

Human reproductive issues in space.

Animal studies in space or analogous environments have suggested that there may be problems in the reproductive sphere; such factors might limit mankind's ability to live and work for extended periods of time in microgravity or on non-terrestrial planetary surfaces. A review of reproductive functioning in animal species studied during space flight demonstrated that most species were affected significantly by the absence of gravity and/or the presence of radiation. These two factors induced alterations in normal reproductive functioning independently of, as well as in combination with, each other. Based on animal models, we have identified several potential problem areas regarding human reproductive physiology and functioning in the space environment. While there are no current space flight investigations, the animal studies suggest priorities for future research in human reproduction. Such studies will be critical for the successful colonization of the space frontier.

Reproduction in the space environment: Part I. Animal reproductive studies.

Mankind's exploration and colonization of the frontier of space will ultimately depend on men's and women's ability to live, work, and reproduce in the space environment. This paper reviews animal studies, from microorganisms to mammals, done in space or under space-simulated conditions, which identify some of the key areas which might interfere with human reproductive physiology and/or embryonic development. Those space environmental factors which impacted almost all species included: microgravity, artificial gravity, radiation, and closed life support systems. These factors may act independently and in combination to produce their effects. To date, there have been no studies which have looked at the entire process of reproduction in any animal species. This type of investigation will be critical in understanding and preventing the problems which will affect human reproduction. Part II will discuss these problems directly as they relate to human physiology.

Reproduction in the space environment: Part II. Concerns for human reproduction.

Long-duration space flight and eventual colonization of our solar system will require successful control of reproductive function and a thorough understanding of factors unique to space flight and their impact on gynecologic and obstetric parameters. Part II of this paper examines the specific environmental factors associated with space flight and the implications for human reproduction. Space environmental hazards discussed include radiation, alteration in atmospheric pressure and breathing gas partial pressures, prolonged toxicological exposure, and microgravity. The effects of countermeasures necessary to reduce cardiovascular deconditioning, calcium loss, muscle wasting, and neurovestibular problems are also considered. In addition, the impact of microgravity on male fertility and gamete quality is explored. Due to current constraints, human pregnancy is now contraindicated for space flight. However, a program to explore effective countermeasures to current constraints and develop the required health care delivery capability for extended-duration space flight is suggested. A program of Earth- and space-based research to provide further answers to reproductive questions is suggested.

Space motion sickness during 24 flights of the space shuttle.

The incidence and severity of Space Motion Sickness (SMS) were determined from 24 flights of the Space Shuttle. A standardized questionnaire developed at the NASA-Johnson Space Center (JSC) was administered to all crewmembers postflight during an oral debriefing with the examining flight surgeon. Cases of SMS were graded mild, moderate or severe using criteria developed at the JSC. The incidence of SMS during a first Shuttle flight for 85 crewmembers was 67% (57 cases). There were 26 mild cases (30%), 20 moderate (24%), and 11 severe (13%). Differences were found between males and females, crew positions (Commander, Pilot, Mission Specialist, etc.), and age groups, which were not statistically significant (p greater than 0.05), but would suggest future research into the mechanism, prevention, and treatment of SMS. The 26 crewmembers with a second flight showed a reduction in SMS incidence to 46%, but the change was not significant compared with the first flight. Nine crewmembers (35%) showed a reduction in SMS severity comparing first and second flights, yet there was no significant difference in the mean time between flights for crewmembers with SMS versus asymptomatic crewmembers. Variability in crewmember training and flight experience may explain some of the differences observed.

Comparison of aerobic fitness and space motion sickness during the shuttle program.

Space motion sickness (SMS) is an important problem for short duration space flight and 71% of STS crewmembers develop symptoms. The search for effective countermeasures and factors that correlate with sensitivity has been extensive. Recently, several investigators have linked aerobic fitness with motion sickness sensitivity in the 1-G or high-G environment. This paper compares the aerobic fitness of 125 Shuttle crewmembers with their SMS symptom category. Aerobic fitness data were obtained from the exercise tolerance test (ETT) conducted nearest the time of launch. SMS data were derived from the medical debrief summaries. Mean VO2max for crewmembers in four SMS categories (none, mild, moderate, severe) were 44.55, 44.08, 46.5, and 44.24 ml.kg-1.min-1, respectively. Scattergrams with linear regression analysis comparing aerobic fitness and SMS symptom classification are also presented. Correlation coefficients comparing SMS categories vs. aerobic fitness for men and women reveal no definite relationship between the two factors. Due to the subjective nature of the data, further studies are suggested to corroborate these findings.

Potential crashworthiness benefits to general aviation from Indianapolis Motor Speedway technology.

General aviation crashworthiness can potentially benefit from certain advances being accomplished by the automobile industry. Progressive improvements in crash protection technology, as documented by a dramatic reduction in crash injuries and fatalities at the Indianapolis Motor Speedway, reflect improved crashworthiness. The speeds of survivable general aviation aircraft impacts are in the range of the Indianapolis Motor Speedway crashes (200-220 mph). This paper relates the declining crash death rates at Indy by decade versus the increase in speeds. The continuous rise in speeds has prompted the development of new crashworthy designs and driver protection equipment. Crashworthiness improvements include crushable surrounding structures, high-grade restraint systems, protective head gear, fire resistant clothing, break-away structural components, and a "protective cocoon" concept. Adaptation of selected advances in crashworthiness design and operations accomplished at the Indianapolis Motor Speedway to the next generation of general aviation aircraft should provide significant dividends in survival of air crashes.

Women and the hazardous environment: when the pregnant patient requires hyperbaric oxygen therapy.

Women are now being exposed in increasing numbers to environmental hazards. Normal operations in that environment plus accidents or training procedures may result in conditions such as decompression sickness, air embolus, hyperoxia, or carbon monoxide poisoning occurring in a woman who also happens to be pregnant. This article examines the animal data and human experience in these conditions in both early and late gestation. The risk of these conditions to the mother and fetus is assessed compared to the problems associated with hyperbaric oxygen therapy (HBO) in pregnancy. Suggestions are made regarding the appropriate use of HBO therapy in pregnancy. Further medical investigation is requested.