Space Nursing for the Future Management of Astronaut Health in other Planets: A Literature Review

2.1. Search strategies

The bibliographic search was carried out through the following databases: Web of Science (WoS), MEDLINE through PubMed, Scopus, SciELO, CINAHL-EBSCO and Google Scholar. The languages considered were English and Spanish. Likewise, other research studies were incorporated to keep the bibliographic review updated and obtain new perspectives, approaches, or findings that can enrich or strengthen the study. There were no restrictions on article type and publication date. The search strategy was designed for each database using DeCS and MeSH descriptors, as well as Boolean operators (“AND” and “OR”) [12]. Field labels with descriptor terms, (Table 1).

2.2. Selection Criteria

Regarding the selection criteria of the articles, after the electronic search, they were previously exported to the Rayyan QCRI application (https://rayyan.qcri.org) for selection, classification and evaluation [13]. Initially, duplicate records that were not specifically related to the research topic were eliminated. Subsequently, the titles, summaries and full articles were read. This activity has allowed us to evaluate concordance and homogenization if the identified records were relevant to the topic and met the research objectives. They imposed no restrictions on article type or publication date, suggesting that a wide range of articles were demonstrated for inclusion. The selection process is highlighted in the flowchart [12], as shown in Fig. (1).

2.3. Ethical Aspects

Ethics committee approval was not sought for the study as this study involved a review of bibliographic databases.

2.4. Limitations

This review has methodological limitations due to the lack of information and the dispersion of the types of documents found on the topic, which has made it difficult to carry out an exhaustive systematic review, which is why the decision was made to carry out a literature review. Furthermore, another important limitation was the difficulty in accessing complete documents, which affected the depth of the analysis of the results obtained.

3.1. Historical Background

The practice of caregiving has been an integral part of human history, evolving alongside the migration of humans to different environments. Florence Nightingale, a pioneer in the field, laid the theoretical foundation of care and helped establish nursing as a science [8, 14]. As human presence expands, including into space exploration, the importance of care practices becomes even more apparent [15, 16].

In the 1920s, a new era began with the inclusion of nurses as part of aircraft crews. On May 15, 1930, Ellen Church became the first nurse assistant and flight attendant [14]. After World War II ended in 1943, she continued her career as a captain in the Army Nurse Corps Air Evacuation Service. This marked the beginning of flight nursing, with the first graduates of the Evacuation School in Bowman Field, Kentucky [14, 17]. Since then, academic advancements have been made to equip nurses with new skills. Many of these skills were already part of the flight nurse section of the Aerospace Medical Association (AsMA), established in 1963. Others were assigned to support bio-astronomical operations in the U.S. Air Force Army [14, 18].

In 1959, Dee O'Hara became the first American nurse assigned to provide emergency medical care to astronauts and their families during the Project Mercury VII mission [1, 9, 15, 17, 19]. Before this assignment, she had worked at Patrick Air Force Base in Cape Canaveral, Florida. She was later recruited as a nurse to evaluate and monitor the health of astronauts in the mentioned project [15]. In 1958, a year before the creation of NASA by President Eisenhower, the institution announced the formation of the Space Nursing Program in 1962 [1].

Eight years later, Martha Rogers emphasized that the role of nurses extended beyond Earth and into extraterrestrial environments [8-10]. To put this idea into action, Linda Plush and Martha Rogers founded the Space Nursing Society (SNS) in 1991, during a private dinner held at the University of Alabama in Huntsville, near NASA's Marshall Space Flight Center. Since its inception, the SNS has grown from 10 nurses and 1 pharmacist to over 350 active members from countries such as the United States, Canada, various European countries, Greece, and Australia [14, 15]. The purpose of this organization was to create new opportunities for the specialty of space nursing and advocate for the preservation of human health beyond Earth's boundaries [1, 14].

3.2. Conceptual Models and Nursing Theories Applied to Space

Nursing, with a long history dating back to the Crimean War, has played a crucial role in creating healthcare environments that prioritize well-being [9,15,17]. Over the years, it has evolved to address different scenarios and has expanded its focus to more deeply understand the interactions between humans and their environment [8,17].

Importantly, Martha Rogers' theory has been widely recognized in the field of nursing and has contributed significantly to the spatial nursing approach [9,15,17]. Their particular approach highlights the interconnection between humans and their environment, recognizing the holistic nature of well-being [9,10,15,20]. Over time, nursing has evolved to address different scenarios and has expanded its focus to more deeply understand the interactions between humans and their environment [8,17].

Authors such as Gomez et al. [9] and Symanski [15] and others have contributed ideas and concepts to interpret, extrapolate and adapt to spatial environments. By incorporating these theories into space nursing practice, it is possible to effectively address the needs of astronauts and ensure their overall well-being during missions. The integration of multiple conceptual models and theories in nursing not only reflects the dynamic nature of the profession but also demonstrates its ability to adapt and thrive in novel and challenging environments [3,5].

• Martha Rogers: has made an important contribution with her unique approach and extensive research and debate. Their approach highlights the relevance of the connection between human beings and their environment, recognizing the integral nature of well-being [ 10 ]. According to this theory, nurses should focus on promoting harmony and balance between astronauts and their environment in space, taking into account the various factors that exist [ 21 ].
• Virginia Henderson: focuses on basic human needs and the role of nurses in helping people meet those needs. His theory can be applied to the care of astronauts in space by addressing their physiological and psychological needs. In the context of space, this theory suggests the need for nurses to support astronauts in maintaining their physical well-being, assisting them with nutrition, hygiene and mobility, and providing them with emotional support to cope with the challenges of living in a space, a confined and unique environment [9].
• Florence Nightingale: Known as the founder of modern nursing, she developed a theory that emphasized the importance of the environment in promoting healing and well-being. His theory can be applied to the care of astronauts in space by focusing on creating a favorable environment that promotes physical and psychological health [9, 17].
• Callista Roy: developed the Adaptation Model, which focuses on the individual's ability to adapt to changes in the environment. This theory can be applied to the care of astronauts in space, considering their adaptation to the microgravity environment and the challenges it poses to their physical and psychological well-being [15]. In addition, it suggests evaluating and promoting the adaptive responses of astronauts, providing interventions to support their adaptation, and evaluating the effectiveness of these interventions. This may include strategies to manage physical changes, and psychological stressors, and promote adaptation to the space environment [8, 9, 15, 17].
• Jean Watson: emphasizes the importance of the nurse-patient relationship. This theory can be applied to the care of astronauts in space by recognizing the need for compassionate and supportive care in a challenging and isolated environment. The theory also suggests that nurses should establish a caring and trusting relationship with astronauts, provide them with emotional support, and create a healing environment that promotes their well-being. This may involve activities such as active listening, therapeutic communication, and creating opportunities for meaningful connections [9, 15].
• Madeleine Leininger: on the diversity and universality of cultural care focuses on the importance of cultural competence in nursing care. While the cultural aspect may be less relevant in the context of space, Leininger's theory highlights the need to consider the unique needs and preferences of astronauts in the provision of care. This may include understanding your individual beliefs, values and preferences related to health and well-being [8, 15].
• Dorothea Orem: focuses on the ability of individuals to engage in self-care activities to maintain their health and well-being. In the context of space, it suggests that nurses should help astronauts develop and maintain their self-care capabilities in a unique and challenging environment. This may involve providing education and training on self-care techniques, assisting with the management of health conditions, and promoting independence in activities of daily living [4].

3.3. Space Environment

The space environment beyond 100 km above sea level presents multiple challenges for the human body, including acoustic noise and vibrations, extreme temperatures, ionizing radiation, microgravity, and relative geometry [1, 5]. These factors can have significant impacts on the health and well-being of astronauts during space exploration missions.

The ambient temperature in space can vary significantly depending on the location and exposure to sunlight. On the side of the spacecraft facing the sun, temperatures can reach up to 100 °C (212 °F), while in the dark shadow, temperatures can drop to as low as -55 to -100 °C (-67 to -148 °F). These extreme temperature variations pose challenges for astronauts and the equipment they use [1, 9]. To protect themselves from extreme temperatures, astronauts rely on the thermal control systems of their spacesuits and spacecraft [9]. These systems use insulation, heating elements, and cooling mechanisms to maintain a comfortable temperature range inside the spacesuit and spacecraft.

Electromagnetic and cosmic radiation from outer space pose a significant challenge for human space exploration. These radiations include Galactic radiation (coming from outside the solar system), solar radiation (high-energy protons from the sun), and particles trapped in the magnetosphere (Van Allen) [1, 4, 5, 9, 15]. These subatomic particles have high ionizing power and can penetrate living tissues, causing damage ranging from small burns to cancerous lesions in sensitive organs such as the bone marrow, lymph nodes, and testes [4, 15, 22]. The severity of the effects depends on the dose and duration of radiation exposure [5]. To protect astronauts from radiation, space craft, and spacesuits are equipped with shielding materials that can absorb or deflect a significant portion of the radiation. Additionally, astronauts are monitored for radiation exposure, and their missions are carefully planned to minimize their time in high-radiation environments [5, 22].

Microgravity, also known as zero gravity or weightlessness, is another important factor in the space environment [1, 15]. It occurs when the sum of forces on a body is zero or less than this value, causing the body to be in free fall away from the gravitational force exerted by a planet. This phenomenon is experienced by astronauts aboard the Space International Station (ISS), which orbits the Earth [8, 15, 22]. The absence of gravity in space has profound effects on the human body (see section on physiological changes) [5].

Relative geometry refers to the spatial orientation and positioning of objects and individuals in the space environment [5]. In the absence of gravity, the concept of “up” and “down” becomes relative, and astronauts must adapt to a new frame of reference. The lack of a clear sense of direction and orientation can cause disorientation and difficulties in spatial perception. Astronauts must rely on visual cues, instrumentation, and training to navigate and perform tasks in space [5, 23].

3.4. Physiological Changes in Spaceflight

For a long time, the human body has developed and evolved under the influence of Earth's gravity. However, when entering a microgravity environment, psychological and physiological changes associated with spaceflight are generated [17, 19]. For this, we describe more relevant aspects of each of them. The immediate effects begin with the loss of the acceleration vector after launch, especially with the alteration of fluid redistribution (2000 ml) from the lower extremities to the upper region of the body, causing symptoms such as facial plethora [1, 9, 22], nasal congestion, redness of the eyes [5, 19, 22], eyelid thickening, swelling of the neck [1, 3, 19] and face [1, 19].

This phenomenon generates a state of cardiovascular deconditioning due to the increase in pressure and volume in the filling of the heart chambers [5, 9, 17]. In prolonged spaceflights that exceed 6 months, some of the astronauts may present cardiac arrhythmias due to a state of dysfunctionality whose causes can be due to loss of minerals [1], ionic alterations, changes in cardiac conduction, and the presence of alternating T phenomena [15]. While at the level of the respiratory system, no major changes affecting human performance have been reported or the data are limited [1]. Despite this, there are slight modifications, such as reduced ventilation, tidal volume, and increased respiratory rate due to the decrease in the weight of the abdominal organs [9].

After the first weeks of arrival in space, space adaptation syndrome occurs and most astronauts have neuro-vestibular effects, a deficit in balance control [4, 9, 17, 22], incoordination, and motion sickness caused by alterations of fluids in the semicircular canals of the inner ear causing spatial disorientation, vertigo and illusions of posture, angular and linear movement (neurosensory conflicts) [9, 23]. In addition, symptoms of increased intracranial pressure (ICP), such as nausea, vomiting, headache, and lethargy due to fluid migration are included [4, 9]. In the sense organs, there is the disorganization of the gustatory, tactile, and visual sensory patterns [1]. The neuro-ophthalmic changes are produced by increased intraocular pressure (IOP) [4, 5, 9], distension of the optic nerve, and posterior flattening of the balloon precisely by retro-ocular edema, and which also generates difficulties in the phenomenon of accommodation [9, 19].

There are also musculoskeletal changes related to the pattern of physical activity and the protein nutritional balance they carry in space. The initial manifestation is characterized by decreased protein synthesis character- ized by an important decrease of muscular mass and loss of muscle strength [4, 9, 22], which can subsequently lead to severe muscle atrophy (disuse atrophy) of the flexor muscles and with a predominance of the posterior or extensor muscles [4, 22, 23].

The integrity of the bone system has been compromised by the disappearance of compressive forces [23], lack of mechanical stimulation, and low illumination (which produces a decrease in the synthesis of vitamin D), generating the slow loss of calcium and other minerals; being the most affected the bones of the legs and spine [1, 4, 8, 19, 22]. In this regard, many of NASA's technical reports have indicated that there is an evident loss in bone mass density of approximately 20% [5] and 25% for prolonged periods, so the skeletal structural system becomes fragile and susceptible to the risk of fracture [1, 4, 8, 19, 22].

This release of calcium from the bones not only increases the risk of fractures [9], but it has also been observed that the rapid loss of these bone minerals is released into the bloodstream, and from there, it is excreted outside through the urine, increasing the possibility of precipitation and the frequency of suffering from renal lithiasis. In some cases, the risk of urinary tract infections can be added too [4, 9, 19, 24]. The level of the digestive system has been evidenced by decreased gastrointestinal transit (probably associated with the motion sickness of the first days), changes in the mucosal barrier and imbalance or dysfunction of the intestinal microbiota [1, 3, 9, 19].

Another biological interaction affected is immune dysregulation, which generally has a multifactorial origin; the best known occurs due to various situations of stress, mostly psychological and those induced by cosmic radiation that is capable of generating oxidative stress and damaging immune cells [9]. Promoting abnormal production of interleukin function and, depressed activation of granulocytes, lymphocytes, and alteration of immunoglobulins reducing their responsiveness to pathogens [1, 4, 21]. Consequently, it has been shown that these opportunistic germs (bacterial and viral) increase their capacity for multiplication [5, 23] and virulence by mutation under space conditions [4, 22].

Finally, space is an exceptional environment that also tests the limits of human psychology [5, 9], since living for prolonged periods in closed environments and working in small spaces drastically affect the psychological sphere; especially after the breakdown of the family womb and the complex interpersonal relationship they normally had on earth [14, 15, 25]. The feeling of deep isolation and stress due to the distance that exists between the Earth and the ISS [4, 24]. Both situations influence sleep patterns, which affects cognitive function that is reflected in decreased intellectual performance, memory, concentration and physical condition regardless of the astronaut's levels of preparation [19, 25].

3.5. Health Problems and Risks in Space

During space exploration, astronauts face unusual and even catastrophic threats [19]; we have been able to identify some of them that can become medical emergencies that compromise the lives and safety of travelers [9, 15]. These problems can go unnoticed within the ISS and during the performance of Extravehicular Activities (EVA) [26]. One way to predict these situations is by analyzing the probability of occurrence and it is classified as follows:

3.6. Nursing Care in Space

Nursing is one of the largest professions in the world with many benefits in health services due to its main foundation and application of the theoretical-scientific methodological process [28]. In the space field, it has been involved as part of a multidisciplinary field with a holistic approach based on human needs and responses where human beings can live and work [9, 25]. This section, it is based on the proposals made by Gómez et al. [9]. This proposal allows us to understand and address care in a structured and synchronized manner in clinical occupation programs in weightless environments. Likewise, the exhaustive analysis of nursing care paradigms is separated into specific stages (before, during, and after) since they allow for more specialized care adapted to the needs identified in previous years in astronauts in each phase of space flight [9]. This will ensure in the future that we provide the best possible care and minimize health risks to astronauts during their space missions, Table 2:

3.7. Nursing Care Management in Space

Effective management of nursing care in space requires careful planning and consideration of the unique challenges and limitations of the space environment. Nurses must be trained to handle medical emergencies and manage patient care in the absence of gravity [1]. They must also be prepared to manage the psychological and emotional challenges that arise from being in space for extended periods. By developing specialized training programs and adapting existing nursing practices to meet the demands of space travel, healthcare providers can ensure that patients receive the best possible care, regardless of their location [1, 9]. Medical care in space is a critical issue, especially on long-duration missions where astronauts may be exposed to a variety of health risks. Nursing care management in space is crucial to ensure the health and well-being of astronauts. The evacuation system is also important in case of a medical emergency, as astronauts may need to be evacuated quickly in the event of an emergency or serious illness [5].

Gravity on Earth has had an integral effect on the development of life over billions of years, shaping the anatomy and physiology of human beings. Astronauts in space missions deal with unique hazards, including the physiological effects of microgravity, medical consequences of radiation exposure, and psychological issues linked to living in a confined, isolated, and extreme environment. Common physiological changes include a reduction in heart size and blood volume, neurological system disturbances, and decreases in bone density and muscle mass. The psychophysiological changes experienced during space missions can have undesirable health consequences and lead to operational difficulties, especially in emergencies. The human body responds to reduced gravity through different biological paths, sometimes adapting well and at other times suffering a process of deconditioning. Factors affecting the physical and mental well-being and health condition of astronauts in space include mission duration (short- vs. long-term), compliance in performing recommended daily exercise protocols (2h30min a day/6-days per week), consuming balanced nutrition and prescribed supplements (i.e., vitamin D), and maintaining an adequate 24h awake-sleep cycle [34, 35]. More than 60 years of medical, health, and scientific knowledge already acquired from low-Earth orbital missions may not be entirely sufficient to face new space challenges, especially considering space tourism. The civilian space traveler profile will vary greatly from that of the well-selected and trained professional astronaut, imposing a range of new and more complex medical and health challenges. Furthermore, the spaceflight arena is evolving to increasingly consider longer-duration flights and potential Moon bases and Mars exploration. This raises the importance of human factors in the success of longer-term space missions and potential human off-Earth settlements [35, 36].

Telemedicine and digital health play a crucial role in space nursing. These technologies involve the use of telecommunications and technological tools for the acquisition, storage, and transmission of health data, as well as enabling virtual meetings [9, 37]. They have already been used to resolve health problems during space missions, bridging the physical distance between healthcare professionals and patients. Current digital technologies, including advanced and sophisticated artificial intelligence-based systems, will progressively be applied in space nursing, making astronauts more autonomous from the care of Earth-based doctors, health professionals, and scientists. Overall, nursing care in space requires specialized training and adaptation of existing practices to address the unique challenges and limitations of the space environment. By effectively managing medical emergencies, promoting health, and preventing diseases, healthcare providers can ensure the well-being of astronauts during space missions. The use of telemedicine and digital health technologies further enhances the provision of healthcare in space, enabling remote monitoring and virtual consultations [21, 33, 37].

3.8. Future Space Nursing Challenges

Nursing has a crucial role in the future of space exploration [19]. While there are already some advancements in this area, few nurses are currently involved due to the demanding nature of their work in different healthcare settings on Earth [14]. However, the primary purpose of the nursing profession is to provide help wherever it is needed [8]. This perspective opens up opportunities for expanding the role of healthcare during astronaut launches [38], space travel, and destinations to improve human adaptation to outer space [8, 39].

In the coming years, future generations of nurses will have the chance to educate and participate in space programs that contribute to our understanding of human responses in microgravity [9, 15, 19]. The goal is to develop new hypotheses and protocols for research-based care in space [5, 19, 40]. To achieve this, nursing education should include specific content related to space topics, enabling nurses to communicate using scientific language [1, 19, 21]. Therefore, formative education will continue to be a priority [21], requiring the evaluation and integration of curricular considerations to enhance scientific production while considering ethical aspects and public and international policies [3, 19, 38].

Although there are currently only a few nursing professionals involved in space-related research, recent recommendations from NASA's life sciences strategic planning study committee indicate the potential for more opportunities and involvement in onboard service [15, 22, 38]. Aerospace nurses working in space agencies, space research programs, or medical teams should possess extensive academic and technical training, as well as exceptional skills to provide care, conservation, and health protection in the face of unexpected medical events in space [19, 23, 24].

The integration of technology into nursing practice is a rapidly evolving field that has the potential to revolutionize healthcare delivery [39]. Information technologies, such as telehealth, are becoming increasingly important in providing healthcare services in remote and dangerous locations with limited access to medical care [1, 21]. Nurses play a critical role in delivering preventive, diagnostic, and therapeutic care to individuals living and working in isolated and extreme conditions, including closed environments, Antarctica excursions, Martian analogs (Fig. 3), scuba diving, and space exploration [39]. In space, nurses are and will continue to be key components in providing preventive, diagnostic, and therapeutic care on the ISS, orbiting bases, the Moon, and Mars [9, 15, 21, 37]. Utilizing information technologies in nursing practice will allow for effective care management and the expansion of diverse activities that promote the development of this specialty [1, 14].

Looking toward the future, it is likely that humanity will eventually establish settlements beyond Earth, such as space cities, lunar bases, and bases on Mars [5], presenting unique environmental characteristics and health challenges. This expansion will allow humans to encounter unprecedented boundaries and unimaginable evolutionary diversity [1, 8, 10]. Additionally, the perception of time will be significantly influenced, as Mars, for example, has a day about an hour shorter than Earth and a year twice as long [8]. Nurses working on manned mission programs to send humans to these planets will need to use Earth's weather patterns as a reference point [15].

The future of space nursing presents numerous challenges and opportunities. By expanding the role of healthcare in space exploration, integrating technology into nursing practice, and preparing for the establishment of settlements beyond Earth, nurses can play a vital role in ensuring the well-being and health of astronauts and future space settlers.