Neuropsychological considerations for long-duration deep spaceflight.

The deep space environment far beyond low-Earth orbit (LEO) introduces multiple and simultaneous risks for the functioning and health of the central nervous system (CNS), which may impair astronauts' performance and wellbeing. As future deep space missions to Mars, moons, or asteroids will also exceed current LEO stay durations and are estimated to require up to 3 years, we review recent evidence with contemporary and historic spaceflight case studies addressing implications for long-duration missions. To highlight the need for specific further investigations, we provide neuropsychological considerations integrating cognitive and motor functions, neuroimaging, neurological biomarkers, behavior changes, and mood and affect to construct a multifactorial profile to explain performance variability, subjective experience, and potential risks. We discuss the importance of adopting a neuropsychological approach to long-duration deep spaceflight (LDDS) missions and draw specific recommendations for future research in space neuropsychology.

Optic nerve sheath diameter and spaceflight: defining shortcomings and future directions.

Neuro-ocular changes during long-duration space flight are known as spaceflight-associated neuro-ocular syndrome (SANS). The ability to detect, monitor, and prevent SANS is a priority of current space medicine research efforts. Optic nerve sheath diameter (ONSD) measurement has been used both terrestrially and in microgravity as a proxy for measurements of elevated intracranial pressure. ONSD shows promise as a potential method of identifying and quantitating neuro-ocular changes during space flight. This review examines 13 studies measuring ONSD and its relationship to microgravity exposure or ground-based analogs, including head-down tilt, dry immersion, or animal models. The goal of this correspondence is to describe heterogeneity in the use of ONSD in the current SANS literature and make recommendations to reduce heterogeneity in future studies through standardization of imaging modalities, measurement techniques, and other aspects of study design.

Increased cerebral blood volume pulsatility during head-down tilt with elevated carbon dioxide: the SPACECOT Study.

Astronauts aboard the International Space Station (ISS) have exhibited hyperopic shifts, posterior eye globe flattening, dilated optic nerve sheaths, and even optic disk swelling from spaceflight. Elevated intracranial pressure (ICP) consequent to cephalad fluid shifts is commonly hypothesized as contributing to these ocular changes. Head-down tilt (HDT) is frequently utilized as an Earth-based analog to study similar fluid shifts. Sealed environments like the ISS also exhibit elevated CO2, a potent arteriolar vasodilator that could further affect cerebral blood volume (CBV) and cerebral blood flow, intracranial compliance, and ICP. A collaborative pilot study between the National Space Biomedical Research Institute and the German Aerospace Center tested the hypotheses that 1) HDT and elevated CO2 physiologically interact and 2) cerebrovascular pulsatility is related to HDT and/or elevated CO2 In a double-blind crossover study (n = 6), we measured CBV pulsatility via near-infrared spectroscopy, alongside noninvasive ICP and intraocular pressure (IOP) during 28-h -12° HDT at both nominal (0.04%) and elevated (0.5%) ambient CO2 In our cohort, CBV pulsatility increased significantly over time at cardiac frequencies (0.031 ± 0.009 µM/h increase in total hemoglobin concentration pulsatility amplitude) and Mayer wave frequencies (0.019 ± 0.005 µM/h increase). The HDT-CO2 interaction on pulsatility was not robust but rather driven by one individual. Significant differences between atmospheres were not detected in ICP or IOP. Further work is needed to determine whether individual differences in pulsatility responses to CO2 relate to visual changes in space.NEW & NOTEWORTHY Cerebral blood volume (CBV) pulsatility-as measured by near-infrared spectroscopy-increases over time during -12° head-down tilt at both cardiac and Mayer wave frequencies. CBV pulsatility appeared to increase more under elevated (0.5%) CO2 at Mayer wave frequencies in some individuals. If similar dynamic pulsatility increases occur in astronauts, there is the potential to initiate vascular and possibly other remodeling processes that lead to symptoms associated with sustained increases in intracranial pressure.

Point-of-Care Ultrasound Utility and Potential for High Altitude Crew Recovery Missions.

INTRODUCTION: Flights to high altitude can lead to exposure and unique pathology not seen in normal commercial aviation. METHODS: This paper assesses the potential for point-of-care ultrasound to aid in management and disposition of injured crewmembers from a high altitude incident. This was accomplished through a systematic literature review regarding current diagnostic and therapeutic uses of ultrasound for injuries expected in high altitude free fall and parachuting. RESULTS: While current research supports its utility in diagnostics, therapeutic procedures, and triage decisions, little research has been done regarding its utility in high altitude specific pathology, but its potential has been demonstrated. DISCUSSION: An algorithm was created for use in high altitude missions, in the event of an emergency descent and traumatic landing for an unconscious and hypotensive pilot, to rule out most life threatening causes. Each endpoint includes disposition, allowing concise decision-making.Galdamez LA, Clark JB, Antonsen EL. Point-of-care ultrasound utility and potential for high altitude crew recovery missions. Aerosp Med Hum Perform. 2017; 88(2):128-136.

Emergency Medical Considerations in a Space-Suited Patient.

INTRODUCTION: The Stratex Project is a high altitude balloon flight that culminated in a freefall from 41,422 m (135,890 ft), breaking the record for the highest freefall to date. Crew recovery operations required an innovative approach due to the unique nature of the event as well as the equipment involved. The parachutist donned a custom space suit similar to a NASA Extravehicular Mobility Unit (EMU), with life support system mounted to the front and a parachute on the back. This space suit had a metal structure around the torso, which, in conjunction with the parachute and life support assembly, created a significant barrier to extraction from the suit in the event of a medical emergency. For this reason the Medical Support Team coordinated with the pressure suit assembly engineer team for integration, training in suit removal, definition of a priori contingency leadership on site, creation of color-coded extraction scenarios, and extraction drills with a suit mock-up that provided insight into limitations to immediate access. This paper discusses novel extraction processes and contrasts the required medical preparation for this type of equipment with the needs of the prior record-holding jump that used a different space suit with easier immediate access. Garbino A, Nusbaum DM, Buckland DM, Menon AS, Clark JB, Antonsen EL. Emergency medical considerations in a space-suited patient. Aerosp Med Hum Perform. 2016; 87(11):958-962.

Clinical Validation of a Transcranial Doppler-Based Noninvasive Intracranial Pressure Meter: A Prospective Cross-Sectional Study.

BACKGROUND: Noninvasive intracranial pressure (ICP) measurement would represent a major advance for patients with neurological problems. The Vittamed ICP meter is an ultrasound-based device reported to have high agreement with lumbar puncture cerebrospinal fluid (CSF) pressure measurement. However, previous studies included mostly patients with normal levels of ICP. The purpose of our study was to perform an independent clinical validation study of a transcranial Doppler-based noninvasive ICP meter in patients anticipated to have a wide range of ICP. METHODS: In a prospective cross-sectional design, we simultaneously measured ICP with the Vittamed device and the invasive lumbar CSF pressure. The operator of each procedure was blinded to the result of the other method. Data were analyzed using Bland-Altman plots, Pearson correlation coefficients, and receiver operator characteristic curves. RESULTS: Twenty-four independent paired measurements of Vittamed and lumbar CSF pressure were obtained; with mean absolute difference between paired measures of 4.5 mmHg (standard deviation 3.1). The 95% limits of agreement were -10.5 to +11.0. The systematic bias (mean of paired differences) was negligible at 0.25 mmHg. The sensitivity, specificity, and area under the curve for ICP >20 mmHg were 0.73, 0.77, and 0.71, respectively. CONCLUSIONS: The Vittamed ICP meter had fair agreement with lumbar CSF pressure measurement. The wide limits of agreement would preclude using this version of the device as a stand-alone method for ICP determination, but may be useful if combined with other ICP screening methods. Ongoing improvements to the Vittamed hardware and software may lead to improvements in accuracy and clinical utility of this device.

Assessing Sensorimotor Function Following ISS with Computerized Dynamic Posturography.

INTRODUCTION: Postflight postural ataxia reflects both the control strategies adopted for movement in microgravity and the direct effects of deconditioning. Computerized dynamic posturography (CDP) has been used during the first decade of the International Space Station (ISS) expeditions to quantify the initial postflight decrements and recovery of postural stability. METHODS: The CDP data were obtained on 37 crewmembers as part of their pre- and postflight medical examinations. Sensory organization tests evaluated the ability to make effective use of (or suppress inappropriate) visual, vestibular, and somatosensory information for balance control. This report focuses on eyes closed conditions with either a fixed or sway-referenced base of support, with the head erect or during pitch-head tilts (± 20° at 0.33 Hz). Equilibrium scores were derived from peak-to-peak anterior-posterior sway. Motor-control tests were also used to evaluate a crewmember's ability to automatically recover from unexpected support-surface perturbations. RESULTS: The standard Romberg condition was the least sensitive. Dynamic head tilts led to increased incidence of falls and revealed significantly longer recovery than head-erect conditions. Improvements in postflight postural performance during the later expeditions may be attributable to higher preflight baselines and/or advanced exercise capabilities aboard the ISS. CONCLUSIONS: The diagnostic assessment of postural instability is more pronounced during unstable-support conditions requiring active head movements. In addition to supporting return-to-duty decisions by flight surgeons, the CDP provides a standardized sensorimotor measure that can be used to evaluate the effectiveness of countermeasures designed to either minimize deconditioning on orbit or promote reconditioning upon return to Earth.

Innovative Methods for the Benefit of Public Health Using Space Technologies for Disaster Response.

Space applications have evolved to play a significant role in disaster relief by providing services including remote sensing imagery for mitigation and disaster damage assessments; satellite communication to provide access to medical services; positioning, navigation, and timing services; and data sharing. Common issues identified in past disaster response and relief efforts include lack of communication, delayed ordering of actions (eg, evacuations), and low levels of preparedness by authorities during and after disasters. We briefly summarize the Space for Health (S4H) Team Project, which was prepared during the Space Studies Program 2014 within the International Space University. The S4H Project aimed to improve the way space assets and experiences are used in support of public health during disaster relief efforts. We recommend an integrated solution based on nano-satellites or a balloon communication system, mobile self-contained relief units, portable medical scanning devices, and micro-unmanned vehicles that could revolutionize disaster relief and disrupt different markets. The recommended new system of coordination and communication using space assets to support public health during disaster relief efforts is feasible. Nevertheless, further actions should be taken by governments and organizations in collaboration with the private sector to design, test, and implement this system.

Emergency medical support for a manned stratospheric balloon test program.

INTRODUCTION: Red Bull Stratos was a commercial program that brought a test parachutist, protected by a full-pressure suit, in a stratospheric balloon with pressurized capsule to over 127,582 ft (38,969 m), from which he free fell and subsequently parachuted to the ground. Given that the major risks to the parachutist included ebullism, negative Gz (toe-to-head) acceleration exposure from an uncontrolled flat spin, and trauma, a comprehensive plan was developed to recover the parachutist under nominal conditions and to respond to any medical contingencies that might have arisen. In this report, the project medical team describes the experience of providing emergency medical support and crew recovery for the manned balloon flights of the program. METHODS: The phases of flight, associated risks, and available resources were systematically evaluated. RESULTS: Six distinct phases of flight from an Emergency Medical Services (EMS) standpoint were identified. A Medical Support Plan was developed to address the risks associated with each phase, encompassing personnel, equipment, procedures, and communications. DISCUSSION: Despite geographical, communications, and resource limitations, the medical team was able to implement the Medical Support Plan, enabling multiple successful manned balloon flights to 71,615 ft (21,828 m), 97,221 ft (29,610 m), and 127,582 ft (38,969 m). The experience allowed refinement of the EMS and crew recovery procedures for each successive flight and could be applied to other high altitude or commercial space ventures.

Physiological monitoring and analysis of a manned stratospheric balloon test program.

INTRODUCTION: The Red Bull Stratos Project consisted of incremental high altitude parachute jumps [maximum altitude 127,852 ft (38,969 m)] from a pressurized capsule suspended from a stratospheric helium-filled balloon. A physiological monitoring system was worn by the parachutist to provide operational medical and acceleration data and to record a unique set of data in a supersonic environment. METHODS: Various physiological parameters, including heart rate (HR), respiratory rate (RR), skin temperature, and triaxial acceleration, were collected during the ascent, high altitude float, free fall, and parachute opening and descent stages of multiple low- and high altitude jumps. Physiologic data were synchronized with global positioning system (GPS) and audiovisual data for a comprehensive understanding of the environmental stressors experienced. RESULTS: HR reached maximum during capsule egress and remained elevated throughout free fall and landing. RR reached its maximum during free fall. Temperature data were unreliable and did not provide useful results. The highest accelerations parameters were recorded during parachute opening and during landing. During each high altitude jump, immediately after capsule egress, the parachutist experienced a few seconds of microgravity during which some instability occurred. Control was regained as the parachutist entered denser atmosphere. DISCUSSION: The high altitude environment resulted in extremely high vertical speeds due to little air resistance in comparison to lower altitude jumps with similar equipment. The risk for tumbling was highest at initial step-off. Physiological responses included elevated HR and RR throughout critical phases of free fall. The monitoring unit performed well despite the austere environment and extreme human performance activities.

Optic nerve sheath diameter measurement techniques: examination using a novel ex-vivo porcine model.

BACKGROUND: Ultrasound (U/S) and MRI measurements of the optic nerve sheath diameter (ONSD) have been proposed as intracranial pressure measurement surrogates, but these methods have not been fully evaluated or standardized. The purpose of this study was to develop an ex-vivo model for evaluating ONSD measurement techniques by comparing U/S and MRI measurements to physical measurements. METHODS: The left eye of post mortem juvenile pigs (N = 3) was excised and the subdural space of the optic nerve cannulated. Caliper measurements and U/S imaging measurements of the ONSD were acquired at baseline and following 1 cc saline infusion into the sheath. The samples were then embedded in 0.5% agarose and imaged in a 7 Tesla (7T) MRI. The ONSD was subsequently measured with digital calipers at locations and directions matching the U/S and direct measurements. RESULTS: Both MRI and sonographic measurements were in agreement with direct measurements. U/S data, especially axial images, exhibited a positive bias and more variance (bias: 1.318, 95% limit of agreement: 8.609) compared to MRI (bias: 0.3156, 95% limit of agreement: 2.773). In addition, U/S images were much more dependent on probe placement, distance between probe and target, and imaging plane. CONCLUSIONS: This model appears to be a valid test-bed for continued scrutiny of ONSD measurement techniques. In this model, 7T MRI was accurate and potentially useful for in-vivo measurements where direct measurements are not available. Current limitations with ultrasound imaging for ONSD measurement associated with image acquisition technique and equipment necessitate further standardization to improve its clinical utility.

Intracranial pressure and optic nerve sheath diameter as cephalic venous pressure increases in swine.

BACKGROUND: Nontraumatic, nonhydrocephalic increases in intracranial pressure (ICP) are often difficult to diagnose and may underlie spaceflight-related visual changes. This study looked at the utility of a porcine animal model of increasing cephalic venous pressure to mimic acute changes in ICP and optic nerve sheath diameter (ONSD) from cephalic venous fluid shifts observed during spaceflight. METHODS: Anesthetized juvenile piglets were assigned to groups of either naïve (N = 10) or elevated superior vena cava pressure (SVCP; N = 20). To elevate SVCP, a 6F custom latex balloon catheter was inserted and inflated to achieve SVCP of 20 and 40 mmHg for 1 h at each pressure. In both groups, serial measurements of ICP, internal jugular pressure (IJP), and external jugular pressure (EJP) were made hourly for 3 h, and ONSD of the right eye was measured hourly by ultrasound (US). RESULTS: There was a significant linear correlation between IJP and ICP (slope: 0.9614 +/- 0.0038, r = 0.9683). With increasing SVCP, resulting ONSD was also well correlated with the ICP (slope: 0.0958 +/- 0.0061, r = 0.7841). The receiver operating characteristic curve for ONSD in diagnosing elevated ICP had an area under the curve of 0.9632 with a sensitivity and specificity of 92% and 91%, respectively, for a cutoff of 5.45 mm. CONCLUSIONS: Increases in SVCP result in ICP changes that are well correlated with alteration in ONSD. These changes are consistent with observed ONSD changes monitored during spaceflight.

Flat spin and negative Gz in high-altitude free fall: pathophysiology, prevention, and treatment.

INTRODUCTION: Red Bull Stratos was a commercial program that brought a test parachutist protected by a full pressure suit to 127,852 ft (38,964 m), via a stratospheric balloon with a pressurized capsule, from which he free fell and subsequently parachuted to the ground. In light of the uniqueness of the operation and the medical threats faced, medical protocols specific to distinctive injury patterns were developed. One unique threat was that of a flat spin during free fall with resultant exposure to -Gz (toe-to-head) acceleration. In preparation for stratospheric free fall, the medical team conducted a review of the literature on the spectrum of human and animal injury patterns attributable to -Gz exposures. Based on the findings, an emergency medical field response protocol was developed for the rapid assessment, diagnosis, and treatment of individuals suspected of -Gz injury. METHODS: A systematic review was conducted on available literature on human and animal studies involving significant -Gz exposure, with subsequent development of an applicable field treatment protocol. RESULTS: The literature review identified pathophysiologic processes and mitigation strategies that were used to develop a prevention and treatment protocol, outlining appropriate interventions using current best medical practices. A medical field treatment protocol was successfully established for the high-altitude balloon program. DISCUSSION: Available literature provided insight into best medical practices for the prevention and treatment of significant -Gz exposures during high-altitude parachute activity. Using the protocol developed for the field medical response, injuries from sustained -Gz exposure can be effectively managed in similar high-altitude and space operations.

Potential anesthesia protocols for space exploration missions.

In spaceflight beyond low Earth's orbit, medical conditions requiring surgery are of a high level of concern because of their potential impact on crew health and mission success. Whereas surgical techniques have been thoroughly studied in spaceflight analogues, the research focusing on anesthesia is limited. To provide safe anesthesia during an exploration mission will be a highly challenging task. The research objective is thus to describe specific anesthesia procedures enabling treatment of pre-identified surgical conditions. Among the medical conditions considered by the NASA Human Research Program Exploration Medical Capability element, those potentially necessitating anesthesia techniques have been identified. The most appropriate procedure for each condition is thoroughly discussed. The substantial cost of training time necessary to implement regional anesthesia is pointed out. Within general anesthetics, ketamine combines the unique advantages of preservation of cardiovascular stability, the protective airway reflexes, and spontaneous ventilation. Ketamine side effects have for decades tempered enthusiasm for its use, but recent developments in mitigation means broadened its indications. The extensive experience gathered in remote environments, with minimal equipment and occasionally by insufficiently trained care providers, confirms its high degree of safety. Two ketamine-based anesthesia protocols are described with their corresponding indications. They have been designed taking into account the physiological changes occurring in microgravity and the specific constraints of exploration missions. This investigation could not only improve surgical care during long-duration spaceflights, but may find a number of terrestrial applications in isolated or austere environments.

Overview of medical operations for a manned stratospheric balloon flight.

INTRODUCTION: Red Bull Stratos was a commercial program designed to bring a test parachutist protected by a full-pressure suit via a stratospheric balloon with a pressurized capsule to 120,000 ft (36,576 m), from which he would freefall and subsequently parachute to the ground. On March 15, 2012, the Red Bull Stratos program successfully conducted a preliminary manned balloon test flight and parachute jump, reaching a final altitude of 71,581 ft (21,818 m). In light of the uniqueness of the operation and medical threats faced, a comprehensive medical plan was needed to ensure prompt and efficient response to any medical contingencies. This report will serve to discuss the medical plans put into place before the first manned balloon flight and the actions of the medical team during that flight. METHODS: The medical operations developed for this program will be systematically evaluated, particularly, specific recommendations for improvement in future high-altitude and commercial space activities. RESULTS: A multipronged approach to medical support was developed, consisting of event planning, medical personnel, equipment, contingency-specific considerations, and communications. DISCUSSION: Medical operations were found to be highly successful when field-tested during this stratospheric flight, and the experience allowed for refinement of medical operations for future flights. The lessons learned and practices established for this program can easily be used to tailor a plan specific to other aviation or spaceflight events.

Pathophysiology, prevention, and treatment of ebullism.

INTRODUCTION: Ebullism is the spontaneous evolution of liquid water in tissues to water vapor at body temperature when the ambient pressure is 47 mmHg or less. While injuries secondary to ebullism are generally considered fatal, some reports have described recovery after exposure to near vacuum for several minutes. The objectives of this article are to review the current literature on ebullism and to present prevention and treatment recommendations that can be used to enhance the safety of high altitude activities and space operations. METHODS: A systematic review was conducted on currently available information and published literature of human and animal studies involving rapid decompression to vacuum and ebullism, with subsequent development of an applicable treatment protocol. RESULTS: Available research on ebullism in human and animal subjects is extremely limited. Literature available identified key pathophysiologic processes and mitigation strategies that were used for treatment protocol design and outlining appropriate interventions using current best medical practices and technologies. DISCUSSION: Available literature suggests that the pathophysiology of ebullism leads to predictable and often treatable injuries, and that many exposures may be survivable. With the growing number of high altitude and space-related activities, more individuals will be at risk for ebullism. An integrated medical protocol can provide guidance for the prevention and treatment of ebullism and help to mitigate this risk in the future.

Gypsy endogenous retrovirus maintains potential infectivity in several species of Drosophilids.

BACKGROUND: Sequences homologous to the gypsy retroelement from Drosophila melanogaster are widely distributed among drosophilids. The structure of gypsy includes an open reading frame resembling the retroviral gene env, which is responsible for the infectious properties of retroviruses. RESULTS: In this study we report molecular and phylogeny analysis of the complete env gene from ten species of the obscura group of the genus Drosophila and one species from the genus Scaptomyza. CONCLUSION: The results indicate that in most cases env sequences could produce a functional Env protein and therefore maintain the infectious capability of gypsy in these species.

Head-eye coordination during simulated orbiter landing.

BACKGROUND: Orbiter landing data show decrements in pilot performance following spaceflight compared to preflight simulated landings. This study aimed to characterize pilot head-eye coordination during simulated orbiter landings, and relate findings to microgravity-related spatial disorientation. METHODS: Orbiter landings were simulated in an A340-300 simulator flown by six pilots. Turns about the Heading Alignment Circle (HAC) to align the orbiter with the runway were simulated by 45 degrees banking turns. Final approach was simulated with an 11 degrees glide slope from an altitude of 4267 m, with preflare at 610 m and touchdown at 200 kn. Orbiter landings were also performed in the Vertical Motion Simulator (VMS) at NASA Ames by a NASA test pilot. RESULTS: A340: During the HAC maneuver the head and eyes rolled toward the visual horizon with a combined gain of 0.14 of bank angle. Pilots alternated fixation between the instruments and the runway during final approach, almost exclusively focusing on the runway after preflare. Optokinetic nystagmus was observed during rollout. VMS: Head and eye roll tilt when rounding the HAC were of similar magnitude to that observed in the A340. During final approach the Heads-Up Display (HUD) reduced pitch head and eye movement. CONCLUSIONS: Roll tilt of the head and eyes during the HAC tended to align the retina with the visual horizon. Overlaying critical flight information and the approaching runway with the HUD reduced pitch head and eye movement during orbiter final approach in the VMS relative to the A340 (no HUD installed).