The Cardiovascular System in Space: Focus on In Vivo and In Vitro Studies

On Earth, humans are subjected to a gravitational force that has been an important determinant in human evolution and function. During spaceflight, astronauts are subjected to several hazards including a prolonged state of microgravity that induces a myriad of physiological adaptations leading to orthostatic intolerance. This review summarises all known cardiovascular diseases related to human spaceflight and focusses on the cardiovascular changes related to human spaceflight (in vivo) as well as cellular and molecular changes (in vitro). Upon entering microgravity, cephalad fluid shift occurs and increases the stroke volume (35–46%) and cardiac output (18–41%). Despite this increase, astronauts enter a state of hypovolemia (10–15% decrease in blood volume). The absence of orthostatic pressure and a decrease in arterial pressures reduces the workload of the heart and is believed to be the underlying mechanism for the development of cardiac atrophy in space. Cellular and molecular changes include altered cell shape and endothelial dysfunction through suppressed cellular proliferation as well as increased cell apoptosis and oxidative stress. Human spaceflight is associated with several cardiovascular risk factors. Through the use of microgravity platforms, multiple physiological changes can be studied and stimulate the development of appropriate tools and countermeasures for future human spaceflight missions in low Earth orbit and beyond.

Sanal Flow Choking Leads to Hemorrhagic Stroke and Other Neurological Disorders in Earth and Human Spaceflight

Evidences are escalating on the diverse neurological disorders associated with COVID-19 pandemic due to the nanoscale Sanal flow choking (PMC7267099). The Sanal flow choking occurs at relatively high and low blood viscosity. Sanal flow choking leads to aneurysm, hemorrhagic-stroke and other neurological-disorders if the vessel geometry is having divergence, bifurcation, stenosis and/or occlusion regions (PMC7933821). Nanoscale Sanal flow choking is more susceptible at microgravity condition due to altered variations of blood viscosity, turbulence and the blood pressure ratio (BPR). Astronauts/Cosmonauts experienced neurological disorders during human spaceflight and thereafter. V.R.S.Kumar et al. (2021) reported that the asymptomatic episodes in the cardiovascular system are due to the internal flow choking (Biofluid/ Sanal flow choking) at a critical blood pressure ratio (BPR), which is regulated by the biofluid/blood heat capacity ratio (BHCR). As the pressure of the nanoscale biofluid / non-continuum-flows rises, fluid viscosity increases and average-mean-free-path diminishes and thus, the Knudsen number lowers heading to a zero-slip wall-boundary condition with the compressible flow regime, which increases the risk of Sanal flow choking and the shock wave generation causing asymptomatic cardiovascular disease. Microgravity environment decreases plasma volume and increases the hematocrit compared with the situation on the Earth surface, which increases the relative viscosity of blood causing an early Sanal flow choking. Herein, we established that the disproportionate blood-thinning treatment increases the risk of the nanoscale Sanal flow choking due to the enhanced boundary-layer-blockage factor. The risk could be diminished by concurrently reducing the viscosity of biofluid/ blood and flow-turbulence by increasing the thermal-tolerance-level in terms of BHCR and/or by decreasing the BPR through new drug discovery or using companion medicine with the traditional blood thinners or other health care management. We recommend all astronauts/cosmonauts should wear ambulatory blood pressure and thermal level monitoring devices similar to a wristwatch throughout the space travel for the diagnosis, prognosis and prevention of internal flow choking leading to asymptomatic cardiovascular disease including neurological disorders.

Abstract P422: Sanal Flow Choking Leads To Hemorrhagic Stroke And Other Neurological Disorders In Earth And Human Spaceflight

Background: Evidences are escalating on the diverse neurological disorders associated with COVID-19pandemic due to the nanoscale Sanal-flow-choking (PMC7267099) . The Sanal-flow-chokingoccurs at relatively high and low blood viscosity. Sanal-flow-choking leads to aneurysm andhemorrhagic-stroke and other neurological-disorders if the vessel geometry is having divergence,bifurcation, stenosis and/or occlusion regions (PMC7933821) . Nanoscale Sanal flow choking ismore susceptible at microgravity condition due to altered variations of blood viscosity, turbulenceand the blood pressure ratio (BPR). Astronauts/Cosmonauts experienced neurological disordersduring human spaceflight and thereafter. Methods: Closed-form analytical, in vitro and in silico studies have been carried out for establishing thephenomenon of Sanal-flow-choking. Biofluid/blood heat capacity ratio (BHCR) of various healthysubjects are estimated. Results: The closed-form analytical models reveal that the relatively high and low blood viscosity arerisk factors of Sanal-flow-choking. In vitro study shows that N2, O2, and CO2 gases arepredominant in fresh-blood samples of the healthy human-being and Guinea-pig at a temperaturerange of 37-40 0 C (98.6-104 0 F), which increases the risk of Sanal-flow-choking. In silico resultsshows the Sanal-flow-choking followed by shock-waves and pressure-overshoot in a simulatedartery with the divergence region. Conclusions: As the pressure of the nanoscale biofluid/non-continuum-flows rises, fluid viscosityincreases and average-mean-free-path diminishes and thus, the Knudsen number lowers headingto a zero-slip wall-boundary condition with the compressible flow regime, which increases the riskof Sanal-flow-choking and the shock wave generation causing asymptomatic cardiovasculardisease. Microgravity environment decreases plasma volume and increases the hematocritcompared with the situation on the earth surface, which increases the relative viscosity of bloodcausing an early Sanal-flow-choking. Herein we established that the disproportionate blood-thinning treatment increases the risk of the nanoscale Sanal-flow-choking due to the enhancedboundary-layer-blockage factor. The risk could be diminished by concurrently reducing theviscosity of biofluid/blood and flow-turbulence by increasing thermal-tolerance-level in terms ofBHCR and/or by decreasing the BPR through new drug discovery or using companion medicinewith the traditional blood thinners or other health care management. We recommend allastronauts/cosmonauts should wear ambulatory blood pressure and thermal level monitoringdevices similar to a wristwatch throughout the space travel for the diagnosis, prognosis andprevention of internal flow choking leading to asymptomatic cardiovascular disease includingneurological disorders.

Nutrition as Fuel for Human Spaceflight

History books are rife with examples of the role of nutrition in determining either the success or the failure of human exploration on Earth. With planetary exploration in our future, it is imperative that we understand the role of nutrition in optimizing health before humans can safely take the next giant leaps in space exploration.

Adapting Disease Prevention Protocols for Human Spaceflight During COVID-19

BACKGROUND: The National Aeronautics and Space Administration (NASA) Flight Crew Health Stabilization Program (HSP) was historically implemented to minimize infectious disease transmission to astronauts in the immediate prelaunch period. The first ever commercial application and adaptation of the NASA HSP was implemented during the Crew Demo-2 mission in the time of the Coronavirus disease 2019 (COVID-19) pandemic. This article details and discusses the first commercial implementation and adaptation of the HSP prior to the Crew Demo-2 launch.METHODS: This is a retrospective descriptive analysis of the application of NASA disease prevention protocols for human spaceflight during the COVID-19 pandemic. In the context of the pandemic, extra precautions added to the HSP included daily symptom surveys completed by Primary Contacts of the crew, COVID-19 RT-PCR testing, and improved quarantine protocols.RESULTS: Of the 91 SpaceX Primary Contacts who completed a total of 2720 daily symptom surveys prior to launch, 22 individuals (24.2) and 198 surveys (7.3) returned positive for potential symptoms of COVID-19. Two individuals were removed due to symptoms indistinguishable from COVID-19. Through this survey, systematic quarantine, and PCR testing, the Crew Demo-2 mission was successful with no known infectious diseases transmitted.CONCLUSIONS: Overall, the commercial implementation of the NASA Health Stabilization Program by SpaceX with adjustments required during the COVID-19 pandemic was a success, with protocols allowing identification and removal of potentially infectious persons from the program. The principles of the HSP may provide an adequate infectious disease playbook for commercial spaceflight operations going forward.Petersen E, Pattarini JM, Mulcahy RA, Beger SB, Mitchell MR, Hu YD, Middleton KN, Frazier W, Mormann B, Esparza H, Asadi A, Musk ER, Alter G, Nilles E, Menon AS. Adapting disease prevention protocols for human spaceflight during COVID-19. Aerosp Med Hum Perform. 2021; 92(7):597602.