Soviet Space Medicine Monitoring
MEDICAL MONITORING
INSTRUMENTATION
The application of electronic bioinstrumentation for monitoring a variety of cosmonaut physiological parameters aboard space ships as well as during numerous experimental situations in space was first proven to be practical during the 1957 Soviet flight of a dog aboard Sputnik 2. These initial observations of cardiac and respiratory functions under a weightless state have proven to be invaluable in demonstrating that mammals, including man, can withstand and function despite the stresses imposed by space flight. The equipment for monitoring cosmonauts has become more sophisticated and is now capable of measuring numerous physiological systems. Certain information of a physical nature that impinges on physiological function, such as cabin temperature, humidity, atmospheric pressure, and gas composition in the space cabin are continuously monitored. In addition, such vital functions as heart and respiratory rate are monitored by electrocardiography and seismocardiography. Electroencephalographic, electroculographic (eye motion), electromyographic (electric potential of muscle) and thermographic determinations are also telemetered to Earth. (67)
The Soviets have developed and utilized measuring devices, which utilize rheographic monitors to quantify parameters of body fluid shifts due to zero gravity. Rheograms of the torso, forearm, skin, as well as the left and right hemisphere of the brain have been monitored. Although marked variations were demonstrated by individual cosmonauts, data obtained on Salyut 6 flights confirm the redistribution of blood during zero gravity. Data also indicate that the quantity of blood reaching the brain and head region increased in general by 26 to 44 percent during the first 2-4 months of space flight prior to stabilizing at that level. Concurrently, blood reaching the lower extremities (thighs and legs) decreased by the same percentage.68 Blood reaching the arms and hands increased in some cases and in others did not vary from normal distribution found under terrestrial gravity.69 By means of plethysmography, a decline (25 to 79 percent) in venous blood pressure in the lower extremities was noted concurrent with an appreciable rise in jugular vein pressure. These observations clearly point to a quantitatively and qualitatively major shift in blood flow which leads to a volume load on the heart. (70) A more detailed discussion of the influence of weightlessness on the cosmonauts' circulatory system while in space and on subsequent return to Earth will be presented in section V.
By means of a mass meter, an instrument for determining the weight of a cosmonaut in zero gravity, muscle atrophy from lack of usage in space, as well as changes in body weight have been observed. (71) These observations have permitted ground support personnel to devise remedial measures for counteracting such occurrences. Countermeasures have included variations in diets, and increase in physical conditioning and activity in space.
The application of remote electronic medical monitoring has been extensively utilized both by the United States and the Soviet Union in manned space programs, as well as in a variety of biological experiments studied by both countries. Both nations have found that, by monitoring the various physiological parameters during space flight, significant information on the health status of mammals during various stages of space flight has been gained. As a result of these observations, remote sensing equipment has evolved which permits the delineation of physiological conditions encountered in space both prior to and during the time of a major biological crisis, such as motion sickness, cardiovascular impairment, bone demineralization and loss in both red cell mass and number.
As the duration of space flight increases, it is critical to determine whether the various abnormal physiological conditions observed were truly transitory and reversible or permanent and possibly life threatening.
PHYSICAL ACTIVITY
EXERCISE PROGRAMS
During the past 10 years, the duration of individual space mission has increased from days to months. In particular, the Soviet Union has had a concerted effort underway to extend the duration that cosmonauts can effectively function on a space platform. This increased tenure in space has placed additional stress on the cosmonauts. It therefore has become imperative that all conceivable effective countermeasures be employed to reduce the adverse effects of zero gravity on human physiology.
Several prominent and potentially serious problems encountered while in space have developed. Some of these are transitory and others are permanent. In some instances, the host has been able to adapt, after a few days, as in the case for motion sickness. In other instances such as the pooling of fluids in the upper portion of the body, the condition is of longer duration, and presents discomfort for several weeks and months. In the latter instance, the circulatory system eventually seems to compensate, but at the expense of stressing the cardiovascular system. (72) Experience gained over the course of extended space missions has provided the Soviets with data suggesting that adaptation in many instances is an individual phenomenon and that certain countermeasures may be prophylactic.
The Soviets claim that rigorous physical training prescribed for the cosmonaut while in terrestrial training and followed during the actual space flight, may reduce the physiological abnormalities encountered in space. By establishing a prescribed physical training format, they have also noted that readaptation to gravity occurs more rapidly after returning to Earth. (73) In fact, the Soviet process of readjusting to Earth gravity takes the form of both physical exercise, physiotherapy, and psychotherapy (see fig. 47). In regard to specific exercise in their more recent space flights lasting over 6 months, the Soviets have required the crew to perform exercises three times daily. These exercises utilize an exercise bicycle which is rated for increasing physical loads and tailored to the individual cosmonaut. In general, the cosmonaut performed exercises consisting of 3,750 kg-m within 5 minutes and a speed of 60 revolutions per minute. (74) The treadmill exercises were performed under load conditions by utilizing tension straps (bungee cords) of approximately 50 kg along the longitudinal axis of the body. The cosmonauts were monitored telemetrically not only for the load being utilized and distance covered (3.9-4.3 km) on the treadmill, but also for their vital signs during their exercise periods. (75) The 3 day exercise cycles are followed by a day of rest when exercise is optional. This protocol is followed throughout the space mission. Even though there have been variations in the frequency and duration of the exercise regime,76 dictated by the details of the mission and the desires of the cosmonaut, the overall concept of strenuous physical training during space flight has proven beneficial in helping the cosmonauts to maintain good physical conditioning and to reduce the difficulties in readaptation after return to Earth.
FIGURE 47.—Chart and Names of Main Rehabilitation and Therapeutic Measure Used at Different Phases and States of the Readaptation Period.
GRAVITY SIMULATION
In addition to the aforementioned methods of maintaining a good physiological profile, the Soviets utilize a special elastic suit (penguin suit). This is attached by elastic bands from the waist and shoulders to the floor of the space station in order to provide artificial gravitational pull on the skeletal musculature, thus hopefully reducing the problems of bone demineralization. Data available to date does not indicate that this practice has reduced demineraliyfltion
Three weeks prior to the termination of the long term space flights (over 6 months), the cosmonauts begin to use a lower body negative pressure suit (chibis vacuum suit). (79) The negative pressure to the lower half of the body causes a redistribution of body fluids from the upper part of the body downward. This redistribution permits the reestablishment of vascular tone for subsequent post flight orthostatic stability. The application of negative pressure is performed every fourth day for a 20 minute interval at negative pressures ranging from -10 to -45 mm of mercury. During the last 2 days of a flight, the negative pressure exposure is extended to a total of 50 minutes at a negative pressure ranging from 25-40 mm of mercury. During this phase of pre-readaptation exercises the cosmonauts drink 300 ml of saline water (3 gm of sodium chloride to 400 ml of water) prior to donning their antigrayity suits This suit is worn prior to descent, in order to create additional pressure to the lower part of the body. This prevents the pooling
of blood in that area immediately after landing and permits more rapid othostatic compensation. (80) .
Therefore during the evolution of both the Soviet and American space program, it has become clear that certain countermeasures can be instituted to counteract some of the deconditionmg processes that set in due to zero gravity. The Soviets have found these exercises and associated protocols successful. Many of the physiological parameters, such as body mass, heart rate, arterial pressure and leg volume, remain relatively constant when compared to preflight values. . , .
A variety of exercises and conditioning equipment has found its place aboard Soviet crafts. These are briefly described in table 16.
TABLE 16.—Physical conditioning equipment on Soviet Space Stations 1
Equipment Application
EMERGENCY AND PROPHYLACTIC DRUGS
PROPHYLACTIC DRUGS
Even though, prior to space flight, the cosmonaut is in optimum physical and mental condition, medical emergencies cannot be
counted. In order to permit the adequate management of such episodes, both Soviet and American spacecraft are equipped with emergency medical kits. These kits consist of medication used to counteract motion sickness, fatigue, nasal congestion, bacterial infection, pain, diarrhea, as well as minor lacerations. (81)
During the more recent long term space flights, the Soviets have utilized prophylactic medication during various stages of their space flight. For example, on two separate occasions during the flight, cardiac muscle prophylaxis was practiced aboard the 175-day Salyut-6 by providing the crew with Inozia-F and Panagin at midpoint and at the end of the mission. Once more, during the last 2 weeks of the flight, the cosmonauts also utilized supplementary Deka vitamins, methionine and glutamic acid. The Soviets claim that these supplements intensify the metabolic process, enhance catacholamine synthesis, normalize the intestinal flora and lipid metabolisms. (82, 83)
The Soviets have not published data about space crew injuries or other medical emergencies; (84) however, they have most likely encountered similiar types of illnesses and injuries to those reported by the United States up through the Apollo Soyuz program. The space missions have encountered mostly minor injuries and infligh medical problems, a list of which are shown on table 17. This table does not include the reported motion sickness difficulties encountered. (85)
TABLE 17.—Illness/injury occurrence in U.S. space crews l
Inflight Illnesses/Injuries: Number
Dysbarism.....................................................................................................2
Eye-skin irritation (fiberglass)......................................................................3
Skin infection...................................................................................... 2
Contact dermatitis................................................................................ 2
Urinary tract infection.......................................................................... 2
Arrhythmias......................................................................................... 2
Serious otitis........................................................................................ 1
Eye and finger injury............................................................................ 1
Sty.
Boil...................................................................................... 1
Rash................................................................................................... 1
Illness/Injury During Recovery and Landing:
Trauma (scalp laceration from detached cornera)................................. 1
Toxic pneumonia (inadvertent atmosphere contamination by N204).... 3
Injury Discovered Postflight: Back strain (due to lifting of heavy object)... 1
(1) Furukawa, S. and A. Nicogossian, P. Buchanan, P. Pool, S. Medical Support and Technology for Long Duration Space Missions. 33rd Int. Astro. Fed. Sept. 22, 1982.
Both the Soviet Union and the United States have considered procedures that might be utilized in the event of more serious injuries. In the case of the United States, procedures are under consideration for the transfer of an injured crew member via a rescue system to a rescue vehicle. (86) The United States also has considered means of restraining a crewmember in the event of spinal injury or for other medical episodes requiring immobilization. (87)
EMERGENCY DRUGS
The Soviets, in view of their flight duration, have given serious consideration to protocols and equipment necessary in the event of medical emergencies that might require surgery and/or resuscitation. (88) They have come to the conclusion that the traditional methods of dealing with medical emergencies are not applicable in space flight. In particular, difficulties would be encountered in an emergency that could require surgical intervention. In that case, the conventional means of anesthesiology would not be possible due to changes in pulmonary physiology that occur during space flights and because it would not be practical to utilize inhalation anesthetics due to the limited space aboard the space vehicle. The close proximity of other crewmembers must be considered since they could also be influenced by the anesthetic being administered. Due to zero gravity the use of intravenously administered anesthetics also would not work well, because there is reduced blood circulation throughout the body. They therefore conclude that the most practical anesthetics would be those that could be given to the local area requiring the surgical procedure. In fact, they propose the possibility of utilizing auriculoacupuncture combined with electroanalgesic particularly for extracavital surgical intervension. In those instances requiring regional anesthesia, this technique seems to be satisfactory. They indicate that surgery should be employed only as a last resort and recommend local hypothermia as a conservative approach until the individual can be brought back to Earth. (89)
However, proceeding on the premise that they may, at one point, have no alternative to surgical intervention in space, the Soviets are developing lightweight surgical equipment, and means of sterilizing this equipment. Methods are also being developed for localized sterile containment of those areas of the body undergoing surgery. (90) In the latter instances, they suggest the use of isolation chambers constructed of transparent plastics having sleeve ports so that the surgery could be performed under more sterile conditions. The surgical procedures and patient isolation presumably would be similar to the techniques currently employed on Earth, where certain medical conditions require the isolation of the patient from his surroundings due to increased risk of infection. (91)
The Soviets are also considering means of removing toxic substances from body fluids that may accumulate during certain medical conditions occurring on space flights. (92) For this procedure they are studying the feasibility of using various sorbents through which the fluids would be passed and then reintroduced into the body. Because of the potential of medical emergencies in space, additional research needs to be performed in these areas in order to come up with practical solutions that could be applied. (93) The need for the resolution of these problem areas is becoming even more apparent as the duration of space flight is extended.
BIORHYTHM PROBLEMS
A human being on Earth maintains a 24-hour cycle. This rhythm may be altered as the individual crosses time zones, in that the work-rest cycle as well as the day-night cycle may be modified by extending or contracting these intervals during the time of crossing such time zones. Even relatively moderate changes in the normal 24-hour cycle upsets the normal physiological, emotional and/or psychological health of an individual. This daily rhythm is linked to the well recognized light-dark cycle of Earth, which regulates the animal's biorhythm. Usually an eight-hour sleep cycle is followed by a 16-hour work cycle. When such a routine rhythm is even moderately interrupted the well-recognized "jet lag" develops. This is characterized by fatigue, lack of attention span and other manifestations of physiological and psychological changes. In some people the change in rhythm is demonstrated by an enhanced susceptibility to infection, intestinal upset and general malaise. (94)
Such vital functions as pulse and heart rate, brain activity, body temperature, renal function, metabolism, as well as changes in endocrine activity are altered at times of light-darkness cycle changes. (95)
The response to the consumption of drugs and alcohol is very dependent on when they are administered during our normal biorhythm. Similarly, emotional disorders are more readily manifested during alteration in the usual biorhythm. In view of the dramatic effects observed on Earth during moderate alteration to biorhythm, the question of how an individual responds to the much more severe changes in the biorhythm in space needs to be studied. Under that situation, the individual may undergo day-night changes every IVa hours; therefore the 24-hour rhythm normally encountered on Earth is severely modified and can bring about appreciable stress response. Therefore, both the Soviets and the United States have had a keen interest in studying the influence of such drastic changes on the biorhythm and developing means for ameliorating these effects. The Soviets, particularly during their longer missions (Soyuz/Salyut) have attempted to maintain a 24-hour cycle for their cosmonauts. They have assumed that the biorhythm is a conditioned reflex and therefore on Salyut 6 they maintain the crews on a 24-hour day, 5-day work week synchronized to Moscow time. (96) Based on their studies, the Soviets also believe that biorhythm is somewhat individualistic and therefore select cosmonauts with specific biorhythms suited for particular space missions. (97) They are also looking at the feasibility of selecting cosmonauts based on their consistency of biorhythm with the assumption that individuals with more constant rhythms adapt more readily to changes and are able to endure desynchrony more readily.(98)
In general, individuals with similar biorhythms seem to function better in a restricted environment. This certainly is the case for the cosmonauts, considering that a fairly rigid schedule, in a confined space, is adhered to by Soviet cosmonauts. Therefore, since individual biorhythms vary as to optimum individual efficiency during different times of day, crew members should be persons with similar biorhythms. This permits the coordination of various activities aboard the space station so that the crew is at optimum efficiency during the time work is required and are all then able to rest during prescribed rest periods. (99)
People can be divided into three types according to their maximum efficiency during a day. There are the "larks," those that have maximum efficiency during the morning, the "owls" whose peak efficiency is at night and others whose peak efficiency is
during the middle of the day. (100) The rather frequent day-night cycles during space flight obviously superimposes additional difficulties on biorhythmic synchrony.
A disruption of the observed individuality of biorhythm both by internal and external stimuli can lead to pathological conditions. Persons working on split-shifts, for example, have greater susceptibility to gastric and neurological disorders. (101 )
Cosmonauts' conditions differ appreciably from the normal work rest cycle of most other professions. The cosmonaut in reality cannot as readily separate himself from his work during leisure time, including the time when he sleeps. Since the cosmonauts are
totally removed from physical contact with persons on Earth, and entirely dependent on the integrity and reliability of their space capsule, they cannot readily, at any time while in space, separate themselves from the mission. The link between the spacecraft and cosmonaut is vital, with his welfare totally dependent on the perfect functioning of the systems aboard the craft. He, therefore, is continually aware of potential danger signals. All stimuli that one cosmonaut senses will be obvious to the others regardless of whether they are on duty at that particular time.
Based on the biorhythm, the Soviets suggests that a programmed schedule for the day significantly reduce the influence of many of the negative factors encountered in space during long term flights. (102) In order to facilitate the organization of such a schedule, the Soviets suggest that the spacecraft must provide specific areas reserved for recreation, sleep, rest and privacy, as well as areas where joint work is performed.(103) The proper selection of cosmonauts based on their biorhythm is therefore essential. This permits them to adapt to the radical changes encountered in space. In order to maintain a synchronous existence in space, certain acquired stimuli that contribute to this stability like the daily dynamics of light, temperature, and humidity present on Earth are very important and should also be maintained in space, if at all possible. (104)
BIOMEDICAL FINDINGS
CARDIOVASCULAR CHANGES
During the course of both the Soviet and American space effort, certain biomedical difficulties have come to the forefront. Most seem to be related to the lack of gravity in space.
Acute changes have been noted in the cardiovascular system. This condition has not lead to any permanent irreversible damage, but it is a constant concern of physicians monitoring people in space. (105) Similarly, due to the absence of gravity, one notes muscle
atrophy, with legs and the waistline appreciably decreasing in size both due to the minimal requirement for muscular activity as well as due to a shift of body fluids and internal organs toward the head.
The lack of gravity also leads to a significant and continual calcium loss. This process of bone demineralization, with a loss of potassium, magnesium, and calcium has been observed in both Soviet cosmonauts and American astronauts. Another problem is that over 50 percent of astronauts and cosmonauts have experienced motion sickness.106
Though all these conditions, except for demineralization, seem to be self-limiting once the body adapts to space or can b/e reversed after a readaption process on Earth, they do pose a potential problem and, according to some U.S. observers, may negate interplanetary manned space missions at least until there are major technical breakthroughs. (107, 108) There is no indication at this time, however, that the Soviets plan to discontinue their progress toward longer and longer flights.
Another problem area that has come to the forefront in the past few years, largely due to the observation made by the Soviets during their long term space mission, is the psychological problem associated with isolation, limited human contact and limited living space. The Soviets have countered some of these problems by developing psychological support systems in space. (109, 110)
A more detailed discussion of these biomedical difficulties seem appropriate since many have been observed virtually from the beginning of space exploration and have so far proved not readily soluble.
Soon after going into space, a variety of cardiac functions of the crew begin to deviate from normal values. There is an initial shift of blood and body fluids from the lower half of the body to the upper torso. A substantial increase in jugular vein pressure becomes apparent. The dynamics of blood propulsion from the left ventricle through the systemic artery changes with a shortening in the heart's contractile phase and associated with a less consistent blood ejection time. The amount of blood reaching the lower extremities decreases by as much as 10 percent and veinous pressure increases throughout the flight. There has, however, been no observed significant change in the biolectrical potential of the myocardium as measured by electrocardiography. (111) When cosmonauts were subjected to stress tests during space flights, the frequency of cardiac contraction increased. This was attributed by the Soviets to a deconditioning in the functional capacity of the cardiovascular system. (112)
Regardless of the duration of a flight, all cosmonauts have demonstrated some degree of cardiovascular deconditioning. This has been manifested on return to Earth by altered heart rates and blood pressure changes. In addition, fatigue has been observed, together with signs pointing towards the potential for fainting, reduced tolerance to performing exercise, as well as a reduced capacity to move about. These manifestations of altered and impaired cardiac functions, have persisted post flight for as little as a few days to as long as 1 month. Echographic studies show that there is at least a 25 percent decrease in the left venticular volume, however, this does normalize, thereby suggesting that there is, most likely, no actual or permanent loss of cardiac muscle. (113, 114)
One notes when evaluating the influence of weightlessness on the cardiovascular system, that other physiological abnormalities are manifested. These include electrolytic imbalance, altered metabolism of minerals and nutrients and modification of certain endocrine functions. Since these deviations from normal may impinge on the normal function of the cardiovascular system, one is looking at a multitude of complex interactions among diverse organ systems and functions all apparently influenced by weightlessness. (115, 116)
Table 18 lists those effects of weightlessness on the cardiovascular system observed and reported by the Soviets.
TABLE 18.—Influence of long-term Soviet space flights on the cardiovascular system
During Flight:
1. Moderate increase in heart rate.
2. Transient increase in observed ejection time.
3. Increase during first 2 to 3 weeks of stroke volume and cardiac output.
4. Increased cerebral blood flow during first 3 to 4 months; prior to stabilization.
TABLE 18.—Influence of long-term Soviet space flights on the cardiovascular system—Continued
5. Increase in jugular vein pressure.
6. A decrease in leg volume.
7. A decrease in venous blood pressure in legs.
8. A decrease in systolic arterial pressure.
Post Flight (transient, days to weeks in duration):
1. Fatigue.
2. Faintness.
3. Perception of increased body weight.
4. Tachycardia.
5. Decrease in stroke volume and ejection time.
6. Orthostatic intolerance.
7. Reduced capacity to move and coordinate.
8. Reduced capacity to endure physical stress.
Source Gazenko, O. G., A. M. Genin, A. D. Egorov. Major Medical Results of the Salyut-6/Soyuz 18 May, Space Flight, v. 2. 32nd Cong. of Int. Astro. Fed., Sept. 6, 1981.
BODY CHANGES
In addition to the cardiovascular manifestations, both during adaption to zero gravity and on readaption to Earth, the lack of gravity appreciably affects motor functions. This is manifested by a decrease in leg and trunk muscle tonicity, and decreasing muscle strength, frequently leading to muscle atrophy. One also observes changes in the normal posture of the body.117 These manifestations are to some degree controlled by strenuous physical exercise while in space.
BONE CHANGES
A major hazard associated with long-term space flight is the progressive loss of bone mass and strength. To date, the progressive nature of this demineralization does not seem to plateau, at least up to the most recently available data reported on the Salyut 6 mission lasting for 175 days. (118) In the absence of being able to stop and reverse the process of osteoporesis during space flights, a situation could arise where the cosmonaut might become susceptible to bone fracture both in space and even more so upon return to Earth and in the event of abrupt deceleration. In the event that the process of demineralization is irreversible then space flights of long duration might bring about a significant increase in bone fracture risk, in later life of the cosmonaut. (119)
DECONDITIONING COUNTERMEASURES
Attempts to reduce and control the effects of weightlessness on cardiovascular changes, muscular deconditioning and bone demineralization have involved inflight, reentry, and post flight measures. These interventions have included inflight exercise, lower body negative pressure, venous blockage, fluid and electrolyte supplementation and the use of anti-G suits. Additionally, nutritional supplements, and the administration of drugs on an experimental basis have been attempted. (120)
The Soviets feel that these countermeasures have appreciable benefits.121 However, there is no unanimity in the U.S. space science community that these are effective practices. Some researchers regard such countermeasures as only marginally effective or perhaps noneffective. (122) In the case of maintaining muscle tone and body mass, exercise does seem to have beneficial effects and warrants further investigation. (123)
BLOOD CHANGES
Blood chemistry analysis performed on cosmonauts after long term space flights showed no significant changes. However, there is a continuous elevated level of 17-hydroxycorticoids. This is a normal manifestation found in mammals during stress. However, in addition to these observations, and perhaps as a consequence of elevated steroid levels, a decreased immune cellular capacity has been observed. (124, 125, 126) After returning to Earth, within several days, there is a reversal of this deficiency. However, it should be kept in mind that there may be a time during space flight that a fully competent immune system may be needed. The Soviets have reported observing significant changes in composition of the microbiological flora of the respiratory tract with intestinal organisms populating it.(127) This could present difficulties in long-term flights where rectal-oral contamination could lead to serious disease potentials.
PSYCHOLOGICAL PROBLEMS
The close confinement imposed by space limitation of the spacecraft, monotony and reduced social contacts all contribute to both physiological as well as potential psychological difficulties. The proximity of a limited number of people, away from familiar surroundings, over a long time span, under constant stress, may in the long run be the limiting factor of interplanetary travel. (128)
Even the selection of compatible individuals, as currently practiced by the Soviet space program, leads to both conflicts as well as euphoric states during a space flight. (129) An understanding of the functions of the mind is still very rudimentary. Extensive research will be required prior to coming to grips with these problem areas.
MOTION SICKNESS
Another medical problem, usually of a transitory nature, is space motion sickness. This is the only adverse effect, thus far noted, that has significantly impaired crew effectiveness during the First few days of a flight. Usually from 30 percent to 50 percent of a crew succumb to this condition. Although pharmacological measures have been attempted, they have met with only limited success. The cause of space motion sickness is not well defined. The sequences leading to its manifestation are not understood due to a lack of information as to sequence of biological stimuli that initiates the phenomena. Motion sickness over extended flights does not seem to be of serious consequence; however, if crew alertness is required during early stages of a flight (1-5 days), it could impair the success of that type of mission. (130)
The myriad of acute biological problems thus far encountered in space flight, for missions of less than one year, seem to be manageable. The success of missions beyond such a time frame at this stage of our knowledge is unknown. (131, 132, 133. 134) Due to the infancy of space exploration, potential chronic or long term pathological consequences have as yet not been addressed or noted.
NUTRITION
DIET SELECTION
Both in the U.S. and U.S.S.R. programs, the quality and variety of food substances available during the earlier space missions have been improved substantially over the years. It became evident early in the space age that food and food selection is not only a requirement in order to maintain the space traveler's nutrient, fluid, and mineral balance, but that nutrition also contributes significantly to the psychological well-being of the space crew. The availability of rehydrated foods has made a major impact on the diversity of foods available to the crew. Beginning with Soyuz 9 (1970) the Soviets had both hot and cold water available aboard the spacecraft. Water is currently partially reconstituted from water condensed aboard the space station and the rest is brought from Earth. (135) This water is used for a variety of things, including the rehydration of foods. In view of the shortage of water, earlier flights were limited both as to types and quality of food available. However, the crews of the Salyut-6 had foods packaged in tubes, canned and dehydrated. (136)
At this time, the menu for the cosmonauts is designed so that individual taste is taken into consideration. A menu is prepared so that there is no repetition of a particular dish for at least 6 days. (137) It has been observed in several Salyut 6 flights that due to the stresses, there is a change in taste perception. (138) In order to improve the cosmonauts' acceptance of a balanced and relatively high caloric diet (3200 kcal), it has become necessary to add different spices suited to individual taste. (139) The diet must meet certain requirements so that adequate caloric and nutritional values are provided commensurate with the energy expended by the cosmonaut. Criteria have been established which dictate that the food should remain stable at 20-25 degrees C, and retain its quality of taste as well as being conveniently packaged and sized for easy manipulation. (140)
With the development of the Salyut orbital station, it became imperative that nutrition, as well as general living conditions be improved. This space station is equipped with a dining table, food heater, and hot and cold water and means of cleaning and sanitizing utensils and disposing of leftovers. (141) To provide sufficient nutrients to compensate for the additional exercise requirement performed by the cosmonauts to counteract some of the physiological effect of weightlessness, the caloric consumption of cosmonauts aboard the Salyut station has been raised to 3200 kcal. (142)
The incorporation of newer dehydrated foods also permitted a reduction in space and weight requirements taken up by foods. Better than 20 percent of foods utilized in the Salyut station are dehydrated. However, Progress cargo craft, as well as Soyuz and Soyuz-T transport ships, resupplied the Salyut 6 space station with dehydrated and canned food supplies as well as with fresh vegetables, milk and fruits. (143, 144) It has been observed that both a proper schedule of feeding as well as acceptable foods are. very important for the maintenance by the cosmonauts of an optimum work capacity. The four meals that the crew partakes in per day are spaced 3 to 5 hours apart. Intervals of 15 to 20 minutes are provided, between exercise and the intake of food, and 1 to 1.5 hours between food intake and initiation of exercises. (145)
As seen in table 19, Soviet crews on long-term Salyut space missions (75 to 185 days) have, maintained a relative stable body weight distribution. During the fourth mission (185 days) the cosmonauts gained weight, a tribute, they claim, to the meticulous adherence to preventive measures including prescribed exercise, intake of vitamins twice daily, body rehydration prior to landing and the use of appetite stimulators such as onions, garlic and other sharp seasonings. Weight gain obviously indicates that the intake of food exceeded the energy expenditure. These data also suggest that strict regulations of nutritional intake during space flight is essential. These observations have convinced the Soviets to increase the use of a variety of dehydrated foods. The typical foods available to the cosmonaut during an average day in space is given in table 20. (146)
TABLE 19—DYNAMICS OF WEIGHT OF CREWS OF MAIN MISSIONS ABOARD SALYUT-6 STATION
Mission and crew member
Body mass Change in body mass
Recommended PrE-flight After landing kg Percent
First:
CDR.............................................67.3 74.4 71.2 -3.2 4.3
FLE................................................75.5 82.0 77.6 -4.4 5.3
Second:
CDR...............................................71.3 84.5 82.4 -2.1 2.5
FLE................................................76.4 75.0 68.6 -6.4 8.5
Third:
CDR.............................................. 65.9 81.7 76.2 -5.5 6.7
FLE................................................82.3 84.0 84.2 +.2 .2
Fourth:
CDR...............................................69.1 70.2 70.8 +.6 .9
FLE................................................82.3 86.5 90.0 +3.5 4.0
Fifth:
CDR............................................ 71.3 83.0 81.2 -1.8 2.1
FLE................................................74.1 73.2 70.1 -3.1 4.2
TABLE 20.—Typical menu during average day in space
Breakfast:
pork with sweet pepper................................................................................. 40 gm
Russian cheese ............................................................................................ …100 gm
honey cake............... .................................................................................. . 45 gm
prunes........................................................................................................... 50 gm
coffee with sugar.......................................................................................... 24 gm
multivitamins lozenge..................................................................................... 1 gm
Lunch:
jellied beef tongue.......................................................................................... 100 gm
praline candies................................................................................................ 50 gm
cherry juice..................................................................................................... 40 gm
Dinner:
ham................................................................................................................. 100 gm
borsche with smoked foods............................................................................. 165 gm
tallin beef with mashed potatoes.............................................................. .... … 52.5 gm
cookies with cheese......................................................................... ........... … 25 gm
apple juice........................................................................................ .............. 30 gm
multivitamins lozenge....................................................................... .............. 1 gm
Supper:
cottage cheese with nuts.............................................................................. 50 gm
assorted meats.................................................................................................. 100 gm
wheat bread..................................................................................................... 30 gm
plum and cherry dessert ................................................................................ 50 gm
tea and sugar.................................................................................................. 23 gm
Laboratory studies performed on blood serum, urine, and fecal disgestive enzyme levels, indicate that the stress of space flight does alter the levels of enzymes such as amylase, lipase, pancreatic enzymes and pepsinogen. Soviet studies suggest that variations observed in these enzyme levels as well as other parameters of digestive function can be well controlled during long term space flights by proper dietary combinations as well as by the physical conditioning. (147)
The Soviets consider nutrition as part and parcel of the overall preparation, execution and subsequent rehabilitation of the cosmonaut. The maintenance of an optimum metabolic and energy level prepares the cosmonaut both physiologically and psychologically. This also maintains the cosmonaut at a high work capacity even in the face of adverse flight conditions and appreciable stress. (148)
The Soviets, also control the pre-flight diet. This refers to all food intake within 24 hours of lift off. Cosmonauts are prohibited from eating any food not prepared in the flight kitchen. The meals are composed of food that is easily digested and not too large in quantity. The food provided has a low capacity for developing intestinal gas, and is composed of nutrients that do not have excessive bulk and lipid content. (149) The composition of the diet while in space has already been discussed. However, the Soviets also place great emphasis on diet after the cosmonauts return to Earth. In order to accelerate rehabilitation to gravity, the cosmonaut is provided with food and fluids consisting of fruits, berry juices, fresh vegetables, stewed and dried apricots, as well as meat such as liver, kidneys, dairy products and eggs. The caloric value of the diet during the first 3 days after returning to Earth is increased gradually to preflight levels (approximately 3300 kcal). (150)
ONGOING RESEARCH
In summary, the Soviets consider nutrition as a significant part of a space mission. They feel, however, that many questions on this subject require additional investigation. (151) These include:
(1) Data to determine energy requirements of cosmonauts under space condition. Information will be provided by establishing an experimental laboratory in their oribtal station;
(2) Nutrition requirements during different phases of the space mission;
(3) Consideration of the cosmonauts individual metabolic rate at various stages of the mission;
(4) Modification of catabolic activity due to the space environment and concurrent stress by employing dietary and pharmaceutical supplements;
(5) Improvement in diets to improve long-term storage and acceptability;
(6) Further understanding of nutritional requirements both in preflight and post flight adaption; and
(7) The use of dietary substances for counteracting detrimental space conditions such as radiation, weightlessness, demineralization, and other encountered physiological difficulties.
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