Space motion sickness

Space motion sickness, presumably triggered by sudden entry into a weightless environment, occurred with unexpected frequency and severity among astronauts who flew the Skylab missions. Recovery from symptoms was complete within 3-5 days, and as revealed by the Skylab M131 Human Vestibular Function Experiment, all crewmembers were immune to experimentally induced motion sickness after mission day 8. This syndrome has been recognized as a possible threat to the early mission well-being and operational efficiency of at least some individuals who will fly space missions in the future. The causes of space motion sickness are not clearly understood, nor have satisfactory methods been identified to date for its prediction, prevention and treatment. In order to minimize the potential impact of this syndrome on Space Shuttle crew operations the National Aeronautics and Space Administration has organized a broad program of inter-disciplinary research involving a large number of scientists in the United States. Current research on the etiology of space motion sickness is based to a large extent on the so called sensory conflict theory. Investigations of the behavioral and neurophysiological consequences of intralabyrinthine, as well as intermodality sensory conflict are being performed. The work in this area is being influenced by the presumed alterations that occur in otolith behavior in weightlessness. In addition to sensory conflict, the possible relationship between observed cephalad shifts of body fluids in weightlessness and space motion sickness is being investigated. Research to date has failed to support the fluid shift theory. Research underway to identify reliable test methods for the prediction of susceptibility to space motion sickness on an individual basis includes attempts to (a) correlate susceptibility in different provocative environments; (b) correlate susceptibility with vestibular and non-vestibular response parameters, the latter including behavioral, hemodynamic and biochemical factors and (c) correlate susceptibility with rate of acquisition and length of retention of sensory adaptation. Controlled studies are also being performed during parabolic flight as a means of attempting to validate predictive tests for susceptibility to this syndrome. Research to develop new or improved countermeasures for space motion sickness is underway in two primary areas. One of these involves anti-motion sickness drugs. Significant achievements have been realized with regard to the identification of new highly efficacious drug combinations, dose levels and routes of administration. Although pronounced individual variations must be accounted for in selecting the optimum drug and dose level, combinations of promethazine plus ephedrine or scopolamine plus dexidrine are presently the drugs of choice. Work is also underway to identify side effects associated with anti-motion sickness drug use and to identify new drugs which may selectively modify activity in central neural pathways involved in motion sickness. In addition to research on drugs, efforts are being made to develop practical vestibular training methods. Variables which influence rate of acquisition of adaptation, length of retention of adaptation and transfer of protective adaptation to new environments are being evaluated. Also, included in this area is the use of biofeedback and autogenic therapy to train individuals to regulate autonomic responses associated with motion sickness. While valuable new knowledge is expected to evolve from these combined research programs, it is concluded that the final validation of predictive tests and countermeasures will require a series of controlled space flight experiments.     

Nausogenic properties of various dynamic and static force environments.

Motion sickness can occur when an accelerating force acting on the human body repeatedly changes amplitude and direction or both. It also can occur without any motion after transfer into a constant force field significantly different from Earth-gravity. Dynamic and static causes of motion sickness can be distinguished accordingly. Space sickness, too, has dynamic as well as static aspects. Dynamic space sickness might depend on increased bilateral differential sensitivity of the peripheral and central vestibular apparatus, whereas static space sickness may be caused by erroneous compensation of bilaterial asymmetries of the otolith-system in the microgravity environment. Experiments in airplanes, cars and on a vestibular sled have shown that the susceptibility to motion sickness is highest for changes of acceleration in the negative X-axis (as compared to the other axes) of the body. During reciprocating linear accelerations on the vestibular sled, standstill periods of movement and the direction of movement cannot correctly be indicated, because the peripheral vestibular apparatus lacks true motion detectors.     

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.     

Coping with space motion sickness in Spacelab missions.

A substantial number of persons, around 75%, making their first transition into orbital flight will need to adapt to this unique environment. The two most powerful instruments in the prevention of space motion sickness reside in the selection process and in acquiring adaptation-prelaunch. Today, neither of these means is practical. One logical alternative is to administer preventative medication to all or none. One candidate drug is a high-potency transdermal therapeutic system (TTS)-scopolamine. This is marketed in the nature of a patch that is affixed to the skin behind the ear 12 hr before need and delivers scopolamine into the blood stream for three days. We are systematically evaluating all claims for its high potency and low side effects. We are also evaluating new antimotion sickness remedies and new combinations of homergic drugs.     

Spacelab experiments on space motion sickness

Recent research results from ground and flight experiments on motion sickness and space sickness conducted by the Man Vehicle Laboratory are reviewed. New tools developed include a mathematical model for motion sickness, a method for quantitative measurements of skin pallor and blush in ambulatory subjects, and a magnitude estimation technique for ratio scaling of nausea or discomfort. These have been used to experimentally study the time course of skin pallor and subjective symptoms in laboratory motion sickness. In prolonged sickness, subjects become hypersensitive to nauseogenic stimuli. Results of a Spacelab-1 flight experiment are described in which four observers documented the stimulus factors for and the symptoms/signs of space sickness. The clinical character of space sickness differs somewhat from acute laboratory motion sickness. However SL-1 findings support the view that space sickness is fundamentally a motion sickness. Symptoms were subjectively alleviated by head movement restriction, maintenance of a familiar orientation with respect to the visual environment, and wedging between or strapping onto surfaces which provided broad contact cues confirming the absence of body motion.     

A new goldfish model to evaluate pharmacokinetic and pharmacodynamic effects of drugs used for motion sickness in different gravity loads.

This paper proposes a new goldfish model to predict pharmacodynamic/pharmacokinetic effects of drugs used to treat motion sickness administered in differing gravity loads. The assumption of these experiments is that the vestibular system is dominant in producing motion sickness and that the visual system is secondary or of small import in the production of motion sickness. Studies will evaluate the parameter of gravity and the contribution of vision to the role of the neurovestibular system in the initiation of motion sickness with and without pharmacologic agents. Promethazine will be studied first. A comparison of data obtained in different groups of goldfish will be done (normal vs. acutely and chronically bilaterally blinded vs. sham operated). Some fish will be bilaterally blinded 10 months prior to initiation of the experiment (designated the chronically bilaterally blinded group of goldfish) to evaluate the neuroplasticity of the nervous system and the associated return of neurovestibular function. Data will be obtained under differing gravity loads with and without a pharmacological agent for motion sickness. Experiments will differentiate pharmacological effects on vision vs. neurovestibular input to motion sickness. Comparison of data obtained in the normal fish and in acutely and chronically bilaterally blinded fish with those obtained in fish with intact and denervated otoliths will differentiate if the visual or neurovestibular system is dominant in response to altered gravity and/or drugs. Experiments will contribute to validation of the goldfish as a model for humans since plasticity of the central nervous system allows astronauts to adapt to the altered visual stimulus conditions of 0-g. Space motion sickness may occur until such an adaptation is achieved.     

Function-morphological investigations of fish inner ear otoliths as basis for interpretation of human space sickness

In man, altered gravity may lead to a vestibular dysfunction causing space motion sickness. A hypothesis was developed, according to which asymmetric inner ear statoliths might be the morphological basis of space sickness. The animal model, fish, revealed further information: inner ear "stone" (otolith) growth is dependent on the amplitude and the direction of gravity, regulated by a negative feedback mechanism. The present study was focused on the question, where the regulation centre of adaptive otolith growth may be situated. Therefore, the vestibular nerve was unilaterally transected in neonate swordtail fish (Xiphophorus helleri). As growth marker, the calcium tracer alizarin-complexone was used. It was found that otolith growth had ceased on the operated head sides indicating that the brain is significantly involved in regulating otolith growth. About 2 weeks after nerve transection, otoliths had regained normal growth, probably due to nerve regeneration. Concerning fish, it has now to be tested, if this regeneration is affected by altered gravity, e.g. in a long-term experiment on the International Space Station. Regarding mammals, it has to be proved if asymmetric statoliths are the basis of kinetosis and whether or not the mammalian brain has an effect on statolith growth in the course of compensating altered gravity.     

Dexamethasone mimicks the antimotion sickness effects of amphetamine and scopolamine

Based on preliminary suggestions that individual differences in susceptibility to stressful motion might be related to physiological differences in responses of the hypothalamic-pituitary-adrenal axis, we tested the efficacy of dexamethasone and metyrapone in subjects exposed to cross-coupled accelerative semicircular canal stimulation on a rotating chair. Subjects given 0.5 mg of dexamethasone every 6 h for 48 h could endure 80% more stressful motion (P = 0.03) in a within-subjects design study, whereas, no improvement followed treatment with 750 mg of metyrapone[correction of metryapone] every 4 h for 24 h. The efficacy of dexamethasone might be explained in terms of its neurochemical actions on several neurotransmitter systems which are also modulated by such classical antimotion sickness drugs as amphetamine and scopolamine. Because dexamethasone induces adaptive changes within the central nervous system it may prove superior to scopolamine and amphetamine which possess significant side effects, are short acting, and rapidly tolerated.     

Vestibular factors influencing the biomedical support of humans in space

This paper will describe the biomedical support aspects of humans in space with respect to the vestibular system. The vestibular system is thought to be the primary sensory system involved in the short-term effects of space motion sickness although there is increasing evidence that many factors play a role in this complex set of symptoms. There is the possibility that an individual's inner sense of orientation may be strongly coupled with the susceptibility to space motion sickness. A variety of suggested countermeasures for space motion sickness will be described. Although there are no known ground-based tests that can predict space motion sickness, the search should go on. The long term effects of the vestibular system in weightlessness are still relatively unknown. Some preliminary data has shown that the otoconia are irregular in size and distribution following extended periods of weightlessness. The ramifications of this data are not yet known and because the data was obtained on lower order animals, definitive studies and results must wait until the space station era when higher primates can be studied for long durations. This leads us to artificial gravity, the last topic of this paper. The vestibular system is intimately tied to this question since it has been shown on Earth that exposure to a slow rotating room causes motion sickness for some period of time before adaptation occurs. If the artificial gravity is intermittent, will this mean that people will get sick every time they experience it? The data from many astronauts returning to Earth indicates that a variety of sensory illusions are present, especially immediately upon return to a 1-g environment. Oscillopsia or apparent motion of the visual surround upon head motion along with inappropriate eye motions for a given head motion, all indicate that there is much to be studied yet about the vestibular and CNS systems reaction to a sudden application of a steady state acceleration field like 1-g. From the above information it is obvious that the vestibular system does have unique requirements when it comes to the biomedical support of space flight. This is not to say that other areas such as cardiovascular, musculo-skeletal, immunological and hematological systems do not have their own unique requirements but that possible solutions to one system can provide continuing problems to another system. For example, artificial gravity might be helpful for long term stabilization of bone demineralization or cardiovascular deconditioning but might introduce a new set of problems in orientation, vestibular conflict and just plain body motion in a rotating space vehicle.     

Male and female characteristics in vestibular testing: a step toward the selection of the best participants for space flight

Vestibular disturbances in connection with space flight were reported by a majority of participating astronauts and cosmonauts. These include motion sickness symptoms in the first few days of the space flight, as well as standing, gait and orientation disturbances after the return to Earth. The Aerospace Medical Community has been trying to select those people that are particularly adapted to the above stresses or that can be further adapted through training programs. As the circle of selectees extends to women, the problem arises as to whether differences between men and women exist under the conditions of space flight. In seeking answers to this question we studied a group of 42 women and 44 men, who were further subdivided according to their subjective motion sickness sensitivity, as determined by a questionnaire. Using this material, 26 men and 22 women were designated as motion sickness resistant, and 18 men and 20 women were designated as nonresistant. The vestibular test battery given these test subjects consisted of caloric, rotatory, optokinetic, vestibulo-spinal and vestibulo-vegetative testing. Because of the mixed orthostatic and vestibular problems seen after space flights, we also studied the response of the vestibular apparatus during peripheral blood pooling as induced by lower body negative pressure. The collected historical and test data are analyzed in this paper with emphasis on the relationship to motion sickness tendency.     

Pharmacological approaches

The use of drugs as countermeasures in the United States and Russian space programs is examined. Pharmacological tools for short and extended space flights are reviewed. Medications flown on the Shuttle are listed. Considerations for the use of pharmacological countermeasures include pharmacokinetics and pharmacodynamics, drug interactions, therapeutic interventions, space motion sickness, the musculoskeletal system, radiation protection, space flight anemia, and cardiovascular disorders.     

U.S. manned space flight: the first twenty years, a biomedical status report.

In the last 20 years, the biomedical problems facing man in space have been brought into sharper focus. Space motion sickness is presently our most serious problem. Its etiology remains obscure, but the "sensory conflict" theory appears most plausible. No valid predictive tests of susceptibility exist and presently we must rely on medication for prevention or mitigation of symptoms. Adaptation/biofeedback techniques may prove useful. Cardiovascular "deconditioning" may be effectively attenuated by use of anti-g suits or plasma expanding techniques. Recent bedrest simulation studies would seem to indicate that concerns about chronically elevated central venous pressure during space flight are unfounded. The loss of red cell mass in space flight appears to be self-limited, independent of mission duration, and not of clinical concern, based on recent Soviet experiences. And finally, clodronate, a new diphosphonate effective in preventing hypercalciuria and negative calcium balance in normal human bedrested subjects, may prove effective in preventing or lessening skeletal mineral loss in space.     

The main results of EVA medical support on the Mir Space Station

The aim of this paper is to review the main results of medical support of 78 two-person extravehicular activities (EVAs) which have been conducted in the Mir Space Program. Thirty-six male crewmembers participated in these EVAs. Maximum length of a space walk was equal to 7 h 14 min. The total duration of all space walks reached 717.1 man-hours. The maximum frequency of EVA's execution was 10 per year. Most of the EVAs (67) have been performed at mission elapsed time ranging from 31 to 180 days. The oxygen atmosphere of the Orlan space suit with a pressure of 40 kPa in combination with the normobaric cabin environment and a short (30 min) oxygen prebreathe protocol have minimized the risk of decompression sickness (DCS). There has been no incidence of DCS during performed EVAs. At the peak activity, metabolic rates and heart rates increased up to 9.9-13 kcal/min and 150-174 min-1, respectively. The medical problems have centred on feeling of moderate overcooling during a rest period in a shadow after the high physical loads, episodes with tachycardia accompanied by cardiac rhythm disorders at the moments of emotional stress, pains in the muscles and general fatigue after the end of a hard EVA. All of the EVAs have been completed safely.     

The Special Purpose Dexterous Manipulator (SPDM) Systems Engineering Effort – A successful exercise in cheaper,faster and (hopefully) better systems engineering

The Special Purpose Dexterous Manipulator (SPDM) is the latest Space Robot developed by the Canadian Space Agency (CSA) and McDonald Detwiller Space and Advanced Robotics (MD Robotics, previously Spar Aerospace) for the International Space Station (ISS). The SPDM has presented its designers with a number of new challenges in performing the Systems Engineering effort required for a complex robotic system:(1) The SPDM initial design was started and attained various levels of maturity for various components under the Space Station Freedom environment, then the Program was stopped and finally restarted under the harsher environment in which the International Space Station is being built.(2) The SPDM is the first space robot to utilize previously developed and space certified robotic components, as well as components with high-commonality to the previously developed ones (electronics, S/W).(3) New requirements levied by the Customer during the negotiations leading to the Program re-start necessitated significant architectural changes versus the SPDM configuration `frozen' when the Program was shut down.(4) The SPDM is the first robotic system of this complexity that is being built under a Firm Fixed Price contract, with the commonality assumptions as one of the cost drivers.This combination of components of various pedigree, coupled with the constraints imposed by an FFP contract have been addressed by the designers through the definition of a novel approach to integrated Systems and Design Engineering.     

KIBO (Japanese Experiment Module in ISS) operations—2008/3–2009/10

Japan Aerospace Exploration Agency (JAXA) launched its own first manned experiment facility in space called the KIBO (Japanese Experiment Module, JEM) in 2008 and 2009 and started operations as part of International Space Station (ISS). To accomplish this Operation, JAXA made its own ground facility in Tsukuba, Japan, called Space Station Integration and Promotion Center (SSIPC). Ground personnel at SSIPC called the JEM Flight Control Team (JFCT) operate the KIBO and have learnt many lessons during its operation. In this presentation, some topics are chosen and explained such as (1) crew/ground personnel interaction and (2) planning lessons learned for manned space activities.     

Space and maritime security–strategies for countering the pirates

Following previous work on space and internal security as part of the European Space Policy Institute's (ESPI) Space and Security programme, ESPI initiated a workshop dealing with an issue of high political as well as public concern – using space as an instrument in the broader strategic context of maritime security – together with the Austrian Institute for European and Security Policy (AIES), which has special expertise in security matters related to Europe. Over 50 high-ranking professionals took part in the 30 November 2009 event, “Space and Maritime Security - Strategies and Capabilities to Counter Piracy”, held at the Austrian Chamber of Commerce (WKÖ) in Vienna. The use of space assets for maritime security has moved up the political agenda as a result of the reliance of the EU ATALANTA NAVFOR mission on services and data provided by the European Union Satellite Centre (EUSC). The workshop therefore addressed technological capabilities as well as industrial approaches in the context of the political framework conditions. It provided a dialogue between space and non-space security communities.     

Life science experiments during the German-Russian MIR '97 mission

Manned spaceflight has been an important element of the German space program over the last decades. This is demonstrated by the nationally managed space missions Spacelab D-l (1985), D-2 (1993), and MIR '92 as well as by the participation in the 1st Spacelab mission FSLP (1983), the NASA missions IML-1 (1992) and IML-2 (1994), as well as in the ESA missions EUROMIR '94 and '95. On February 12th, this year, the German cosmonaut Reinhold Ewald was launched together with his Russian colleagues Wasilij Zibliew and Alexander Lasudkin onboard of a Soyuz spacecraft for another stay of a German cosmonaut onboard of the Russian Space Station MIR. This mission--the so-called German/Russian MIR '97--was, of course, another cornerstone with regard to the cooperation between Russian and German space organizations. The cooperation in the area of manned missions began 1978 with the flight of the German cosmonaut Sigmund Jahn onboard of Salyut 6, at that time a cooperation between the Soviet Union and the German Democratic Republic in the frame of the Interkosmos Program. In March 1992, it was followed by the flight of Klaus Dietrich Flade with his stay onboard of MIR. After two further successful ESA missions, EUROMIR '94 and '95 with the two German cosmonauts Ulf Merbold and Thomas Reiter and with a marked contribution of German scientists, the decision was taken to perform another German/Russian MIR mission, the so-called MIR '97. In Germany, MIR'97 was managed and performed in a joint effort between several partners. DARA, the German Space Agency, was responsible for the overall program and project management, while DLR, the German Aerospace Research Establishment, was responsible for the cosmonaut training, for medical operations, for the mission control at GSOC in Oberpfaffenhofen as well as for user support.     

Development of space motion sickness in a ground-based human centrifuge

Adaptation of the vestibular system, specifically the otolith organs, to a non-terrestrial environment can result in space motion sickness-like symptoms when the human is reintroduced to the normal, 1 Gz, terrestrial environment. This premise was investigated by exposing nine subjects to 90 min of sustained 2 Gz acceleration in a human centrifuge and then observing and evaluating them at 1 Gz. Five of the subjects developed slight SMS symptoms, three developed moderate, and one developed frank sickness. Postural instabilities in two of the most affected subjects were also observed using the Equitest System post exposure. Long duration exposure to a non-terrestrial G(2Gz) appears to be a potential means for developing SMS-like symptoms in a ground-based human centrifuge.     

Individual differences in susceptibility to motion sickness among six Skylab astronauts

One of the Skylab experiments dealt with motion sickness, comparing susceptibility in the workshop aloft with susceptibility preflight and postflight. Tests were conducted on and after mission-day 8 (MD 8) by which time the astronauts were adapted to working conditions. Stressful accelerations were generated by requiring the astronauts, with eyes covered, to execute standardized head movements (front, back, left, and right) while in a chair that could be rotated at angular velocities up to 30 rpm. The selected endpoint was either 150 discrete head movements or a very mild level of motion sickness. In all rotation experiments aloft, the five astronauts tested (astronaut 1 did not participate) were virtually symptom free, thus demonstrating lower susceptibility aloft than in preflight and postflight tests on the ground when symptoms were always elicited. Inasmuch as the eyes were covered and the canalicular stimuli were the same aloft as on the ground, it would appear that lifting the stimulus to the otolith organs due to gravity was an important factor in reducing susceptibility to motion sickness even though the transient stimuli generated under the test conditions were substantial and abnormal in pattern. Some of the astronauts experienced motion sickness under operational conditions aloft or after splashdown, but attention is centered chiefly on symptoms manifested in zero gravity. None of the Skylab-II crew (astronauts 1 to 3) was motion sick aloft. Astronaut 6 of the Skylab-III crew (astronauts 4 to 6) experienced motion sickness within an hour after transition into orbit; this constitutes the earliest such diagnosis on record under orbital flight conditions. The eliciting stimuli were associated with head and body movements, and astronaut 6 obtained relief by avoiding such movements and by one dose of the drug combination 1-scopolamine 0.35 mg + d-amphetamine 5.0 mg. All three astronauts of Skylab-III experienced motion sickness in the workshop where astronaut 6 was most susceptible and astronaut 4, least susceptible. The higher susceptibility of SL-III crewmen in the workshop, as compared with SL-II crewmen, may be attributable to the fact that they were based in the command module less than one-third as long as SL-II crewmen. The unnatural movements, often resembling acrobatics, permitted in the open spaces of the workshop revealed the great potentialities in weightlessness for generating complex interactions of abnormal or unusual vestibular and visual stimuli. Symptoms were controlled by body restraint and by drugs, but high susceptibility to motion sickness persisted for 3 days and probably much longer; restoration was complete on MD 7. From the foregoing statements it is clear that on and after MD 8 the susceptibility of SL-II and SL-III crewmen to motion sickness under experimental conditions was indistinguishable. The role played by the acquisition of adaptation effects prior to MD 8 is less clear and is a subject to be discussed.     

Changes in the vestibular function during space flight

An analysis of observations and investigations carried out in space flight has shown that some cosmonauts and astronauts have experienced vestibular disorders during the transition to weightlessness. Vestibular-sensory disorders include: Spatial illusions (the feelings of falling down, being in an upside-down position, the sensations of rotation of the craft or the body) and vertigo occurring during the onset of the orbital flight and head movements; Feelings, similar to those experienced in response to Coriolis accelerations on the Earth, which occasionally develop in weightlessness during the spacecraft rotation upon abrupt head and body movements and restrained feet; Feelings "of the load on the vestibular analyser which is unlike any Earth-bound effects" upon abrupt head movements during the first hours of an orbital flight and "a prolonged movement" during the switch-off of thrusters in weightlessness. Vestibular-vegetative disorders comprise a complex of symptoms similar to those of motion sickness: loss of appetite, stomach awareness (12%), hypersalination, nausea (9.6%) and vomiting (4.8%). Soviet studies suggest that the vestibular tolerance to the flight effects depends on the natural stability and training to the cumulative effect of adequate vestibular stimuli. This has been used in the development of the system of vestibular selection. Changes in the vestibular function seem to play the major role in the development of motion sickness in weightlessness, extra-labyrinthine factors being contributory. The current hypotheses have not yet been adequately confirmed in experiments. A detailed physiological analysis allows the conclusion that the decisive factor in the development of motion sickness may be the disturbance of the function of analysers responsible for spatial orientation which take the form of sensory conflicts as well as an altered reactivity of the organism due to the hemodynamic rearrangement.