Gravity on Earth has shaped the anatomy and physiology of human beings. Exposure to microgravity has been shown to affect the entire body, causing numerous changes, such as a reduction in heart size and blood volume, disturbances of the neurological system, and decreases in bone density and muscle mass. This paper aims to increase the awareness and understanding of humankind’s final frontier.
The presence of gravity on Earth has had an integral effect on the development of life over billions of years and shaped the anatomy and physiology of human beings. Exposure to microgravity has been shown to affect the entire body, causing numerous changes, such as a reduction in heart size and blood volume, disturbances of the neurological system, and decreases in bone density and muscle mass. These physiological changes can lead to undesirable health consequences and to operational difficulties, especially in emergency situations.
The growth in private space corporations, the imminent increase in numbers of space tourists, and intentions to prolong the duration and distance of space travel necessitates a greater awareness and understanding of humankind’s final frontier and its potential effects on space travellers. It is vitally important to know more about the characteristics of the space environment and how these affect our health and wellbeing, and anatomy and physiology during spaceflight, including the cardiopulmonary, neuropsychological and muscle-skeleton systems.
A discussion follows of some of the most notable alterations that take place in the body of astronauts when exposed to the environment of space.
The removal of all hydrostatic gradients when entering space (microgravity) causes a headward shift of blood and body fluids, resulting in facial oedema and decreased leg volume. This shift is believed to be the primary stimulus for many of the physiological effects of spaceflight, including a reduction in plasma volume, increase in central fluid volume, enlargement of the heart, and an increase in cardiac output on initial exposure to microgravity. However, this is subsequently followed by a decrease in heart size and cardiac output, with a drop in the circulating blood volume as part of the cardiovascular adaptation to microgravity. More recently, neurovascular changes (Spaceflight Associated Neuro-Ocular Syndrome - SANS) and decreased venous blood flow in veins in the upper body have been identified.
The symptoms of post-flight cardiovascular de-conditioning include low arterial blood pressure, inappropriate increase in resting heart rate and decreased exercise tolerance. This condition exists when there is either an excessive postural decrease in cardiac filling and stroke volume and/or an inadequate compensatory neurohumoral response, resulting in a failure to maintain adequate brain perfusion in an upright position. Post-flight orthostatic intolerance has been reported widely by astronauts and cosmonauts, especially after long-term space missions.
The effects of short and long-term microgravity exposure on lung volumes, capacities and function have been studied on the ground, in parabolic fights and during space missions.
Parabolic flights have shown that the sternum bone is displaced in the cranial direction in microgravity and is accompanied by an increase in diameter of the lower rib cage. This change in the position of the chest wall was predicted to cause the volume-pressure curve to lie between the standing upright and the supine position curves, with a net result of a reduction in lung volumes.
During the 9-day flight of the Space Life Sciences-1 mission, lung volumes were able to be measured in sustained microgravity and showed a reduction in static and dynamic volumes. The gravitational gradient also affects the distribution of ventilation and perfusion in the upright human lung. This uneven distribution of ventilation and blood flow within the lungs leads to variations in ventilation-perfusion ratios. Microgravity was expected to abolish completely apicobasal differences in perfusion and its persistence is possibly related to other mechanisms not affected by gravity, such as centralperipheral differences in blood flow and interregional differences in conductance. The diffusion capacity of the lung increased by 62 per cent in a parabolic flight study and by 28 per cent in sustained microgravity, when values were compared with pre-flight standing values.
The vestibular system, located within the inner ear, is used by the body to give us our spatial orientation and balance. It is one of the first organs to react to microgravity exposure, with a quick and sometimes intense response to the lack of gravity. This is known as space motion sickness
The psychosocial aspects faced by astronauts during space missions are also considered, addressing the coping mechanisms used to deal with confinement, monotony and isolation from family and friends. This important topic affecting humans and their interactions in space, including psychiatric, interpersonal and cultural aspects, becomes even more relevant with the imminent increase in space tourism and longer-term plans for crewed Moon and Mars missions. Astronauts on the International Space Station (ISS), for example, live in an isolated, confined and extreme environment, initiating natural pathophysiological processes of psychosocial adaptation. Although isolated, crews maintain continuous communication with the ground control Mission Support, who provide in-flight guidance and assistance at any time during the flight.
Our muscle-skeleton system is greatly affected by time spent in space and countermeasures are applied to minimise the changes that occur in bones and muscles. It is well known that the amount of weight that bones must support while in space is reduced to almost zero. At the same time, many bones that aid in movement are no longer under the same stresses that they are subjected to on Earth. Bone loss begins within the first few days in space and astronauts are able to regain most, but not all of their bone mass in the months following their return to Earth.
The lack of gravity also has the same detrimental effect on skeletal muscles, especially those that normally act against the force of gravity, such as the calf and quadricep muscles, which become weaker and atrophic. The best way of decreasing the effects of microgravity on the muscle-skeletal system is through the adoption of a routine of daily exercise during a space mission.
Exercise countermeasures require the adaptation of exercise devices and the use of restraint systems to keep the astronaut in place when performing exercises. A healthy and balanced diet plus supplementary substances, such as vitamin D, are also important for the maintenance of muscles and bones in space.
The importance of an adequate understanding of these and other physiological responses to microgravity, with a view to assuring the good health and wellbeing of astronauts in space, has grown since the beginning of human space exploration and has motivated a series of biomedical experiments in several space missions, such as the Skylab, Space Shuttle, Mir Space Station and ISS programmes. However, many factors associated with spaceflight activities complicate attempts to delineate the time course of physiological responses to microgravity, including:
Sample Size - crew sizes have ranged from 5 to 8 astronauts, with only 2 or 3 of these being allowed to participate in biomedical experiments. Any attempt to extrapolate from this small number to a larger population is unsatisfactory;
Limited Capabilities for Scientific Observations - biomedical experiments are restricted by operational limitations and the time available during a space mission
Extensive Use of Countermeasures - the prophylactic and therapeutic use of a variety of countermeasures has masked the direct effects attributable to microgravity alone on human adaptation to the space environment;
Different Mission Types - frequent changes of mission profiles make direct comparisons between flights difficult.
Therefore, space analogues on Earth, water and air have been developed, ranging from placing a volunteer on a tilt-table, immersion in a pool (neutral buoyancy facility) or studying the effects of gravitational changes in a parabolic flight. Some analogues can be established in Universities or Research Institutes, with the involvement of professors and grad/undergraduate students. The best scenario would be to have academics from different areas, creating a very inter- and multidisciplinary environment in which to study the human body and mind reactions and adaptations to some simulated aspects of a space mission.
Given the current rise in number of commercial spaceflight organisations, such as SpaceX, Virgin Galactic and Blue Origin, and predicted exponential growth in this space sector, it is vital to better understand some aspects regarding Space Tourism, particularly the medical challenges involved, and also contemplating the next steps for this developing area. The profile of the civilian space traveller, for example, is likely to be very different from that of the well selected and trained professional astronauts, which will impose a range of medical and health challenges to doctors and scientists on the ground. In the evolving spaceflight arena that will increasingly consider longer-duration spaceflights and the potential for Moon bases and Mars exploration, the human factor becomes increasingly important to long-term mission success and to the possibility of humankind living in off-Earth communities.
Besides the use of countermeasures in a space mission, a very important way to medically support astronauts and space tourists is the use of digital health, and in particular, telemedicine.
Telemedicine has been applied to space missions since the first manned spaceflight in 1961, when the ECG of Yuri Gagarin was transmitted to the mission control centre on Earth. The continuous development of digital and communication technologies has progressively improved the way these systems can help monitor the wellbeing of astronauts during space missions and treat clinical conditions.
This technology applied at the ISS has provided some inputs for the provision of healthcare in rural and remote areas of the globe. Groundbased telemedicine and digital health studies have also been conducted to evaluate how these systems could provide health assistance in the management of physical and mental issues through the evaluation of medical procedures and care of different health conditions. However, the great distances in planetary exploration, such as a trip to Mars, leads to time delays in communication with medical personnel on Earth, which can range from three minutes to 24 minutes each way, affecting the application of telehealth in space missions. In terms of telesurgery, for example, a useful tool when there is the need to invasively treat patients who are geographically separated from their physicians, it would be impossible to apply it for a medical situation on Mars, however, it is still a viable technique for missions to low-Earth orbit or the Moon.
It is in this context of the current human space exploration era that InnovaSpace, founded by myself and Administrative Director Mary Upritchard, was born!
InnovaSpace believes in a Space Without Borders and this is our driving ethos. It is a limited company, established and registered in England & Wales in April 2018, with activities in the areas of aerospace medicine, space physiology and telehealth.
A strong Advisory Board, consisting of world-leading researchers and scientists, provides further support in the space life sciences and related areas, covering a wide diversity of fields, such as space pharmacy, nutrition, psychiatry, physiology, biomechanics, aerospace medicine, human factors, parabolic flights and Space/Earth technology transfer, among others.
InnovaSpace is focused across the spectrum of society, from a governmental level through to universities and the industry, whilst also conducting outreach projects with the general public and the young, using the subject of Space and Space Exploration to inspire interest in the STEAM subjects. InnovaSpace also endeavours to assist nations in harnessing the human side of short- and long-term space program goals, as well as developing access to space knowledge and TeleHealth potential in educational institutions.
InnovaSpace has identified Six Factors that are necessary for Space Leadership and Distinction: (1) the Global Bridging of institutes, experts and talent; (2) the enablement of a Space Identity through initiatives, which form a rate of global participation; (3) the empowerment of Innovation through research that is transferable to other sectors; (4) the Facilitation of New Knowledge; (5) the Cultivation of young minds for aerospace and space science through engagement with schools and the development of aligned curricula - For example, our Kids2Mars outreach program, with a model of global participation, has introduced Space and Space Sciences in a motivational manner to children worldwide; (6) Building skilled capacity in highly-complex yet necessary areas for Space Preparedness.
In summary, InnovaSpace is a Think Tank, global and inclusive, multicultural and multidisciplinary in nature, and operating in space, aeronautics and telehealth. Through its work, InnovaSpace establishes collaborations and partnerships with governments, the business sector, academic world, research institutions, non-profit organizations and society as a whole. Its actions aim to conduct innovative activities in teaching and research, provide technical and scientific consultancy and establish a network of professionals, researchers, entrepreneurs, and students, linked by the common theme of the human presence in extreme environments, such as astronauts on orbital missions/interplanetary trips and aviators/crew members in aeronautical activities.