A Qualitative Investigation of Space Exploration Medical Evacuation Risks

INTRODUCTION: Exploration beyond low Earth orbit requires innovative solutions to support the crew medically, especially as the opportunity for timely evacuation to Earth diminishes. This includes assessing the risks and benefits that a complicated medical evacuation (MEDEVAC) poses to the injured crewmember, the crew, and the mission. This qualitative study identifies common MEDEVAC risk assessment principles used in spaceflight and other extreme environments to better inform future risk assessment tools and exploration mission concepts.METHODS: Semistructured interviews were conducted with subject matter experts in spaceflight and analog domains, including polar operations, undersea operations, combat medicine, and mountaineering. Transcripts were analyzed using the qualitative method of Thematic Analysis with the technique of consensus, co-occurrence, and comparison.RESULTS: Subject matter experts described 18 themes divided into two main categories: Primary Risk Considerations (e.g., crew, mission, resources, time) and Contributing Factors (e.g., psychological considerations, medical preparation, politics).DISCUSSION: Primary Risk Considerations can assess MEDEVAC risk across mission phases, with Contributing Factors acting as premission tools to adjust those risks. Inter- and intracategory connections identified medical support considerations, MEDEVAC support considerations, and philosophy as the most impactful Contributing Factors. Medical support considerations, psychological considerations, and political considerations were found to have unique aspects given the distances and societal impact of exploration vs. low Earth orbit spaceflight. The Contributing Factor theme of decision making was determined to be unique due to its impacts across both categories. These findings expand current considerations and are important inputs for exploration mission MEDEVAC Concepts of Operations.Almand A, Ko SY, Anderson A, Keller RJ, Zero M, Anderson AP, Laws JM, Lehnhardt K, Easter BD. A qualitative investigation of space exploration medical evacuation risks. Aerosp Med Hum Perform. 2023; 94(12):875-886.

Additive Sensory Noise Effects on Operator Performance in a Lunar Landing Simulation

INTRODUCTION: Adding noise to a system to improve a weak signal's detectability is known as stochastic resonance (SR). SR has been shown to improve sensory perception and cognitive performance in certain individuals, but it is unknown whether this performance improvement can translate to meaningful macrocognitive enhancements in performance for complex, operational tasks.OBJECTIVE: We investigated human operator performance in a lunar landing simulation while applying auditory white noise and/or noisy galvanic vestibular stimulation.METHODS: We measured performance (N = 16 subjects) while completing simulation trials in our Aerospace Research Simulator. Trials were completed with and without the influence of auditory white noise, noisy galvanic vestibular stimulation, and both simultaneously in a multimodal fashion. Performance was observed holistically and across subdimensions of the task, which included flight skill and perception. Subjective mental workload was collected after completing four trials in each treatment.RESULTS: We did not find broad operator improvement under the influence of noise, but a significant interaction was identified between subject and noise treatment, indicating that some subjects were impacted by additive noise. We also found significant interactions between subject and noise treatment in performance subdimensions of flight skill and perception. We found no significant main effects on mental workload.CONCLUSIONS: This study investigated the utility of using additive sensory noise to induce SR for complex tasks. While SR has been shown to improve aspects of performance, our results suggest additive noise does not yield operational performance changes for a broad population, but specific individuals may be affected.Sherman SO, Shen Y-Y, Gutierrez-Mendoza D, Schlittenhart M, Watson C, Clark TK, Anderson AP. Additive sensory noise effects on operator performance in a lunar landing simulation. Aerosp Med Hum Perform. 2023; 94(10):770-779.

Estimation of Subjectively Reported Trust, Mental Workload, and Situation Awareness Using Unobtrusive Measures

OBJECTIVE

We use a set of unobtrusive measures to estimate subjectively reported trust, mental workload, and situation awareness (henceforth "TWSA").

BACKGROUND

Subjective questionnaires are commonly used to assess human cognitive states. However, they are obtrusive and usually impractical to administer during operations. Measures derived from actions operators take while working (which we call "embedded measures") have been proposed as an unobtrusive way to obtain TWSA estimates. Embedded measures have not been systematically investigated for each of TWSA, which prevents their operational utility.

METHODS

Fifteen participants completed twelve trials of spaceflight-relevant tasks while using a simulated autonomous system. Embedded measures of TWSA were obtained during each trial and participants completed TWSA questionnaires after each trial. Statistical models incorporating our embedded measures were fit with various formulations, interaction effects, and levels of personalization to understand their benefits and improve model accuracy.

RESULTS

The stepwise algorithm for building statistical models usually included embedded measures, which frequently corresponded to an intuitive increase or decrease in reported TWSA. Embedded measures alone could not accurately capture an operator's cognitive state, but combining the measures with readily observable task information or information about participants' backgrounds enabled the models to achieve good descriptive fit and accurate prediction of TWSA.

CONCLUSION

Statistical models leveraging embedded measures of TWSA can be used to accurately estimate responses on subjective questionnaires that measure TWSA.

APPLICATION

Our systematic approach to investigating embedded measures and fitting models allows for cognitive state estimation without disrupting tasks when administering questionnaires would be impractical.

Training augmentation using additive sensory noise in a lunar rover navigation task

Background

The uncertain environments of future space missions means that astronauts will need to acquire new skills rapidly; thus, a non-invasive method to enhance learning of complex tasks is desirable. Stochastic resonance (SR) is a phenomenon where adding noise improves the throughput of a weak signal. SR has been shown to improve perception and cognitive performance in certain individuals. However, the learning of operational tasks and behavioral health effects of repeated noise exposure aimed to elicit SR are unknown.

Objective

We evaluated the long-term impacts and acceptability of repeated auditory white noise (AWN) and/or noisy galvanic vestibular stimulation (nGVS) on operational learning and behavioral health.

Methods

Subjects (n = 24) participated in a time longitudinal experiment to access learning and behavioral health. Subjects were assigned to one of our four treatments: sham, AWN (55 dB SPL), nGVS (0.5 mA), and their combination to create a multi-modal SR (MMSR) condition. To assess the effects of additive noise on learning, these treatments were administered continuously during a lunar rover simulation in virtual reality. To assess behavioral health, subjects completed daily, subjective questionnaires related to their mood, sleep, stress, and their perceived acceptance of noise stimulation.

Results

We found that subjects learned the lunar rover task over time, as shown by significantly lower power required for the rover to complete traverses (p < 0.005) and increased object identification accuracy in the environment (p = 0.05), but this was not influenced by additive SR noise (p = 0.58). We found no influence of noise on mood or stress following stimulation (p > 0.09). We found marginally significant longitudinal effects of noise on behavioral health (p = 0.06) as measured by strain and sleep. We found slight differences in stimulation acceptability between treatment groups, and notably nGVS was found to be more distracting than sham (p = 0.006).

Conclusion

Our results suggest that repeatedly administering sensory noise does not improve long-term operational learning performance or affect behavioral health. We also find that repetitive noise administration is acceptable in this context. While additive noise does not improve performance in this paradigm, if it were used for other contexts, it appears acceptable without negative longitudinal effects.

Effects of additive sensory noise on cognition

Background

Adding noise to a system to improve a weak signal's throughput is known as stochastic resonance (SR). SR has been shown to improve sensory perception. Some limited research shows noise can also improve higher order processing, such as working memory, but it is unknown whether SR can broadly improve cognition.

Objective

We investigated cognitive performance while applying auditory white noise (AWN) and/or noisy galvanic vestibular stimulation (nGVS).

Methods

We measured cognitive performance (n = 13 subjects) while completing seven tasks in the cognition test battery (CTB). Cognition was assessed with and without the influence of AWN, nGVS, and both simultaneously. Performance in speed, accuracy, and efficiency was observed. A subjective questionnaire regarding preference for working in noisy environments was collected.

Results

We did not find broad cognitive performance improvement under the influence of noise (p > 0.1). However, a significant interaction was found between subject and noise condition for accuracy (p = 0.023), indicating that some subjects exhibited cognitive changes with the addition of noise. Across all metrics, noisy environment preference may trend to be a potential indicator of whether subjects will exhibit SR cognitive benefits with a significant predictor in efficiency (p = 0.048).

Conclusion

This study investigated using additive sensory noise to induce SR in overall cognition. Our results suggest that using noise to improve cognition is not applicable for a broad population; however, the effect of noise differs across individuals. Further, subjective questionnaires may be a means to identify which individuals are sensitive to SR cognitive benefits, but further investigation is needed.

Modeling the Design Characteristics of Woven Textile Electrodes for long-Term ECG Monitoring

An electrocardiograph records the periodic voltage generated by the heart over time. There is growing demand to continuously monitor the ECG for proactive health care and human performance optimization. To meet this demand, new conductive textile electrodes are being developed which offer an attractive alternative to adhesive gel electrodes but they come with their own challenges. The key challenge with textile electrodes is that the relationship between the manufacturing parameters and the ECG measurement is not well understood, making design an iterative process without the ability to prospectively develop woven electrodes with optimized performance. Here we address this challenge by applying the traditional skin-electrode interface circuit model to woven electrodes by constructing a parameterized model of the ECG system. Then the unknown parameters of the system are solved for with an iterative MATLAB optimizer using measured data captured with the woven electrodes. The results of this novel analysis confirm that yarn conductivity and total conductive area reduce skin electrode impedance. The results also indicate that electrode skin pressure and moisture require further investigation. By closing this gap in development, textile electrodes can be better designed and manufactured to meet the demands of long-term ECG capture.

Performance Risks During Surface Extravehicular Activity and Potential Mitigation Using Multimodal Displays

BACKGROUND: Surface extravehicular activity (sEVA) will be a critical component of future human missions to the Moon. sEVA presents novel risks to astronaut crews not associated with microgravity operations due to fundamental differences in task demands, physiology, environment, and operations of working on the lunar surface. Multimodal spacesuit informatics displays have been proposed as a method of mitigating sEVA risk by increasing operator autonomy.METHODS: A formalized literature review was conducted. In total, 95 journal articles, conference papers, and technical reports were included. Characteristics of U.S. spacesuits were reviewed, ranging from the Apollo A7L to the xEMU Z-2.5. Multimodal display applications were then reviewed and assessed for their potential in aiding sEVA operations.RESULTS: Through literature review 25 performance impairments were identified. Performance impairments caused by the spacesuit represented the greatest number of sEVA challenges. Multimodal displays were mapped to impairments and approximately 36% of performance impairments could be aided by using display interfaces.DISCUSSION: Multimodal displays may provide additional benefits for alleviating performance impairments during sEVA. Utility of multimodal displays may be greater in certain performance impairment domains, such as spacesuit-related impairments.Zhang JY, Anderson AP. Performance risks during surface extravehicular activity and potential mitigation using multimodal displays. Aerosp Med Hum Perform. 2023; 94(1):34-41.

Side-by-Side Comparison of Human Perception and Performance Using Augmented, Hybrid, and Virtual Reality

Alternative reality (XR) technologies, including physical, augmented, hybrid, and virtual reality, offer ways for engineered spaces to be evaluated. Traditionally, practitioners (such as those designing spacecraft habitats) have relied on physical mockups to perform such design evaluations, but digital XR technologies present several streamlining advantages over their physical counterparts. These digital environments vary in their level of virtuality, and consequently have different effects on human perception and performance, with respect to a completely physical mockup environment. To date, very little has been done to characterize and quantify such differences in human perception and performance across XR environments of equal fidelity for the same end application. Here, we show that perception and performance in the virtual reality environment most closely mirror those in the physical reality environment, as measured through volumetric assessment and functional task experiments. These experiments required subjects to judge the dimensions of 3D objects and perform operational tasks presented via checklists. Our results highlight the potential for virtual reality systems to accelerate the iterative design of engineered spaces relative to the use of physical mockups, while preserving the human perception and performance characteristics of a completely physical environment. These findings also elucidate specific advantages and disadvantages to specific digital XR technologies with respect to one another and the physical reality baseline. Practitioners may inform their selection of an XR modality for their specific end application based on this comparative analysis, as it contextualizes the niche for each technology in the realm of iterative design for engineered spaces.

Utility of the Full ECG Waveform for Stress Classification

The detection of psychological stress using the electrocardiogram (ECG) signal is most commonly based on the detection of the R peak-the most prominent part of the ECG waveform-and the heart rate variability (HRV) measurements derived from it. For stress detection algorithms focused on short-duration time windows, there is potential benefit in including HRV features derived from the detection of smaller peaks within the ECG waveform: the P, Q, S, and T waves. However, the potential drawback of using these small peaks is their smaller magnitude and subsequent susceptibility to noise, making them more difficult to reliably detect. In this work, we demonstrate the potential benefits of including smaller waves within binary stress classification using a pre-existing data set of ECG recordings from 57 participants (aged 18-40) with a self-reported fear of spiders during exposure to videos of spiders. We also present an analysis of the performance of an automated peak detection algorithm and the reliability of detection for each of the smaller parts of the ECG waveform. We compared two models, one with only R peak features and one with small peak features. They were similar in precision, recall, F1, area under ROC curve (AUC), and accuracy, with the greatest differences less than the standard deviations of each metric. There was a significant difference in the Akaike Information Criterion (AIC), which represented the information loss of the model. The inclusion of novel small peak features made the model 4.29×1028 times more probable to minimize the information loss, and the small peak features showed higher regression coefficients than the R peak features, indicating a stronger relationship with acute psychological stress. This difference and further analysis of the novel features suggest that small peak intervals could be indicative of independent processes within the heart, reflecting a psychophysiological response to stress that has not yet been leveraged in stress detection algorithms.

Challenges in Quantifying Heel-Lift During Spacesuit Gait

INTRODUCTION: Heel-lift is a subjectively reported fit issue in planetary spacesuit boot prototypes that has not yet been quantified. Inertial measurement units (IMUs) could quantify heel-lift but are susceptible to integration drift. This work evaluates the use of IMUs and drift-correction algorithms, such as zero-velocity (ZVUs) and zero-position updates (ZPUs), to quantify heel-lift during spacesuited gait.METHODS: Data was originally collected by Fineman et al. in 2018 to assess lower body relative coordination in the spacesuit. IMUs were mounted on the spacesuit lower legs (SLLs) and spacesuit operator’s shank as three operators walked on a level walkway in three spacesuit padding conditions. Discrete wavelet transforms were used to identify foot-flat phase and heel-off for each step. Differences in heel-off timepoints were calculated in each step as a potential indicator of heel-lift, with spacesuit-delayed heel-off suggesting heel-lift. Average drift rates were estimated prior to and after applying ZVUs and ZPUs.RESULTS: Heel-off timepoint differences showed instances of spacesuit-delayed heel-off and instances of operator-delayed heel-off. Drift rates after applying ZVUs and ZPUs suggested an upper time bound of 0.03 s past heel-off to measure heel-lift magnitude with an accuracy of 1 cm.DISCUSSION: Results suggest that IMUs may not be appropriate for quantifying the presence and magnitude of heel lift. Operator-delayed heel-off suggests that the SLL may be expanding prior to heel-off, creating a false vertical acceleration signal interpreted by this study to be spacesuit heel-off. Quantifying heel-off will therefore require improvements in IMU mounting to mitigate the effects of SLL, or alternative sensor technologies.Boppana A, Priddy ST, Stirling L, Anderson AP. Challenges in quantifying heel-lift during spacesuit gait. Aerosp Med Hum Perform. 2022; 93(8):643–648.

Isolation and confinement due to the COVID-19 pandemic: Lessons for human spaceflight

BACKGROUND

Astronauts live and work in isolated, confined, extreme (ICE) environments that create both high stress and the need for high performance. The COVID-19 pandemic created ICE-like conditions across the globe by confining people to their homes under the ever-present threat of disease. Our goal is to understand the impact of prior experience in ICE on coping, using the pandemic as a pseudo space analog environment.

METHODS

We administered a survey three times with 7 days between administrations. A total of 82 participants completed all three survey sessions, and these participants were divided into three groups for analysis. The first group is those with prior experience in an ICE environment (n = 17; 7F/10 M), the second is those aged 30-55 with a master's or doctoral degree and without prior experience (n = 22; 10F/12 M), and the third is the general population (n = 43; 27F/16 M). Linear mixed models were used for statistical analysis of the results, given the unequal sample sizes.

RESULTS

The experienced group did not show healthier mental health scores than the astronaut-like group, but both groups displayed higher scores than the general population. However, work productivity scores for the experienced group were higher on average than the other two groups.

DISCUSSION

Results suggest that prior experience in ICE may improve the capability to maintain productivity-corresponding to the idea of resilience. However, experience may not improve mental health maintenance, suggesting that other approaches are needed to prepare astronauts for the mental health stressors of long-duration exploration missions.

The influence of perceived stress on the human microbiome

Objective

Microbial dysbiosis, a shift from commensal to pathogenic microbiota, is often associated with mental health and the gut–brain axis, where dysbiosis in the gut may be linked to dysfunction in the brain. Many studies focus on dysbiosis induced by clinical events or traumatic incidents; however, many professions in austere or demanding environments may encounter continuously compounded stressors. This study seeks to explore the relationship between microbial populations and stress, both perceived and biochemical.

Results

Eight individuals enrolled in the study to provide a longitudinal assessment of the impact of stress on gut health, with four individuals providing enough samples for analysis. Eleven core microbial genera were identified, although the relative abundance of these genera and other members of the microbial population shifted over time. Although our results indicate a potential relationship between perceived stress and microbial composition of the gut, no association with biochemical stress was observed. Increases in perceived stress seem to elucidate a change in potentially beneficial Bacteroides, with a loss in Firmicutes phyla. This shift occurred in multiple individuals, whereas using cortisol as a stress biomarker showed contradictory responses. These preliminary data provide a potential mechanism for gut monitoring, while identifying targets for downstream modulation.

Detection of the Complete ECG Waveform with Woven Textile Electrodes

Wearable physiological monitoring systems are becoming increasingly prevalent in the push toward autonomous health monitoring and offer new modalities for playful and purposeful interaction within human computer interaction (HCI). Sensing systems that can be integrated into garments and, therefore, daily activities offer promising pathways toward ubiquitous integration. The electrocardiogram (ECG) signal is commonly monitored in healthcare and is increasingly utilized as a method of determining emotional and psychological state; however, the complete ECG waveform with the P, Q, R, S, and T peaks is not commonly used, due to the challenges associated with collecting the full waveform with wearable systems. We present woven textile electrodes as an option for garment-integrated ECG monitoring systems that are capable of capturing the complete ECG waveform. In this work, we present the changes in the peak detection performance caused by different sizes, patterns, and thread types with data from 10 human participants. These testing results provide empirically-derived guidelines for future woven textile electrodes, present a path forward for assessing design decisions, and highlight the importance of testing novel wearable sensor systems with more than a single individual.

Proposed mechanism for reduced jugular vein flow in microgravity

Internal jugular flow is reduced in space compared with supine values, which can be associated with internal jugular vein (IJV) thrombosis. The mechanism is unknown but important to understand to prevent potentially serious vein thromboses on long duration flights. We used a novel, microgravity‐focused numerical model of the cranial vascular circulation to develop hypotheses for the reduced flow. This model includes the effects of removing hydrostatic gradients and tissue compressive forces – unique effects of weightlessness. The IJV in the model incorporates sensitivity to transmural pressure across the vein, which can dramatically affect resistance and flow in the vein. The model predicts reduced IJV flow in space. Although tissue weight in the neck is reduced in weightlessness, increasing transmural pressure, this is more than offset by the reduction in venous pressure produced by the loss of hydrostatic gradients and tissue pressures throughout the body. This results in a negative transmural pressure and increased IJV resistance. Unlike the IJV, the walls of the vertebral plexus are rigid; transmural pressure does not affect its resistance and so its flow increases in microgravity. This overall result is supported by spaceflight measurements, showing reduced IJV area inflight compared with supine values preflight. Significantly, this hypothesis suggests that interventions that further decrease internal IJV pressure (such as lower body negative pressure), which are not assisted by other drainage mechanisms (e.g. gravity), might lead to stagnant flow or IJV collapse with reduced flow, which could increase rather than decrease the risk of venous thrombosis.

Dynamic foot morphology explained through 4D scanning and shape modeling

A detailed understanding of foot morphology can enable the design of more comfortable and better fitting footwear. However, foot morphology varies widely within the population, and changes dynamically as the foot is loaded during stance. This study presents a parametric statistical shape model from 4D foot scans to capture both the inter- and intra-individual variability in foot morphology. Thirty subjects walked on a treadmill while 4D scans of their right foot were taken at 90 frames-per second during stance phase. Each subject's height, weight, foot length, foot width, arch length, and sex were also recorded. The 4D scans were all registered to a common high-quality foot scan, and a principal component analysis was done on all processed 4D scans. Elastic-net linear regression models were built to predict the principal component scores, which were then inverse transformed into 4D scans. The best performing model was selected with leave-one-out cross-validation. The chosen model predicts foot morphology across stance phase with a root-mean-square error of 5.2 ± 2.0 mm and a mean Hausdorff distance of 25.5 ± 13.4 mm. This study shows that statistical shape modeling can be used to predict dynamic changes in foot morphology across the population. The model can be used to investigate and improve foot-footwear interaction, allowing for better fitting and more comfortable footwear.

Galvanic Vestibular Stimulation Produces Cross-Modal Improvements in Visual Thresholds

BACKGROUND

Stochastic resonance (SR) refers to a faint signal being enhanced with the addition of white noise. Previous studies have found that vestibular perceptual thresholds are lowered with noisy galvanic vestibular stimulation (i.e., "in-channel" SR). Auditory white noise has been shown to improve tactile and visual thresholds, suggesting "cross-modal" SR.

OBJECTIVE

We investigated galvanic vestibular white noise (nGVS) (n = 9 subjects) to determine the cross-modal effects on visual and auditory thresholds.

METHODS

We measured auditory and visual perceptual thresholds of human subjects across a swath of different nGVS levels in order to determine if some individual-subject determined best nGVS level elicited a reduction in thresholds as compared the no noise condition (sham).

RESULTS

We found improvement in visual thresholds (by an average of 18%, p = 0.014). Subjects with higher (worse) visual thresholds with no stimulation (sham) improved more than those with lower thresholds (p = 0.04). Auditory thresholds were unchanged by vestibular stimulation.

CONCLUSION

These results are the first demonstration of cross-modal improvement with galvanic vestibular stimulation, indicating galvanic vestibular white noise can produce cross-modal improvements in some sensory channels, but not all.

Woven electrocardiogram (ECG) electrodes for health monitoring in operational environments

Electrical signals produced within the human body can reveal information about a wide variety of physiological processes including physical activity, cardiac health, and psychological state. The industry standard for physiological signal detection is the use of adhesive electrodes that stick onto the skin. These electrodes can irritate the skin over long periods of time and are not reusable, making them a challenge for use in operational environments. Further, these electrodes often require gel to improve signal transduction, leading to changes in signal quality as these gels dry over time. Wearable sensors for operational environments should be comfortable, unobtrusive, and non-stigmatizing while maintaining signal quality high enough to allow the detection of health states. Here, we present the development and test of a set of woven textile electrodes of 8 different sizes for chest-mounted, 3-lead electrocardiogram (ECG) monitoring. Ten male subjects were tested with each of the woven electrode sizes and with one set of adhesive electrodes. A derived performance metric and signal-to-noise ratio were calculated for each set of electrodes for comparison between them. The smallest sized electrodes were found to be least effective, while the 6^th of the 8 sizes were found to be most effective.

Detecting changes in distortion product otoacoustic emission maps using statistical parametric mapping and random field theory

Distortion product otoacoustic emission (DPOAE) maps collect DPOAE emissions over a broad range of frequencies and ratios. One application of DPOAE mapping could be monitoring changes in intracranial pressure (ICP) in space, where non-invasive measures of ICP are an area of interest. Data were collected in two experiments to statistically assess changes in DPOAE maps. A repeatability study where four maps per subject were collected across four weeks to establish "normal" variability in DPOAE data, and a posture study where subjects were measured supine and prone with lower body negative pressure, lower body positive pressure (LBPP), and at atmospheric pressure. DPOAE amplitude maps were analyzed using statistical parametric mapping and random field theory. Postural changes produced regional changes in the maps, specifically in the range of 5-7.5 kHz and between primary tone ratios of 1.13-1.24. These regional changes were most pronounced in the prone LBPP condition, where amplitudes were lower from baseline for the Postural Cohort than the Repeatability Cohort. Statistical parametric mapping provided a sensitive measure of regional DPOAE map changes, which may be useful clinically to monitor ICP noninvasively in individuals or for research to identify differences within in cohorts of people.

Textile Electrocardiogram (ECG) Electrodes for Wearable Health Monitoring

Wearable health-monitoring systems should be comfortable, non-stigmatizing, and able to achieve high data quality. Smart textiles with electronic elements integrated directly into fabrics offer a way to embed sensors into clothing seamlessly to serve these purposes. In this work, we demonstrate the feasibility of electrocardiogram (ECG) monitoring with sewn textile electrodes instead of traditional gel electrodes in a 3-lead, chest-mounted configuration. The textile electrodes are sewn with silver-coated thread in an overlapping zig zag pattern into an inextensible fabric. Sensor validation included ECG monitoring and comfort surveys with human subjects, stretch testing, and wash cycling. The electrodes were tested with the BIOPAC MP160 ECG data acquisition module. Sensors were placed on 8 subjects (5 males and 3 females) with double-sided tape. To detect differences in R peak detectability between traditional and sewn sensors, effect size was set at 10% of a sample mean for heart rate (HR) and R-R interval. Paired student's t-tests were run between adhesive and sewn electrode data for R-R interval and average HR, and a Wilcoxon signed-rank test was run for comfort. No statistically significant difference was found between the traditional and textile electrodes (R-R interval: t = 1.43, p > 0.1; HR: t = - 0.70, p > 0.5; comfort: V = 15,p > 0.5).

Portable Autorefractors for Detecting Axial Length Changes in Space

INTRODUCTION

We evaluated the reproducibility of two portable, self-administered autorefractors (Netra and SVOne Pro) to assess the time course of visual changes on the ISS.

METHODS

We measured cycloplegic refractive error at 5 visits at least a week apart in 13 subjects (6 women, 7 men, 30 ± 9 yr) using both devices seated and also prone with lower body positive pressure (LBPP) applied. Axial length was measured with an optical biometer. Subjects completed a questionnaire on device preferences.

RESULTS

The SVOne seated intrasession reproducibility coefficient (RPC) was 0.37 diopters (D), while the Netra's was 0.41 D. Intersession seated results were: RPC = 0.67 D for the SVOne and RPC = 0.54 D for the Netra. The average seated to prone LBPP differences were significantly different from zero for both the SVOne and Netra. The SVOne was preferred in four out of five categories on the questionnaire and took half the time to complete a measurement set compared to the Netra.

DISCUSSION

Users preferred the SVOne and it took less time. An SVOne refraction change of 0.67 D from baseline would happen by chance less than 5% of the time. If multiple separate measurements were taken, the detection limit could be reduced (e.g., three repeated measurements could reduce it to 0.38 D). Since astronauts with visual changes show spherical equivalent changes of 0.5 to 1.0 D, in-flight autorefractors could help determine the time course of refractive changes in space from which changes in axial length could be inferred.Masterova KS, Anderson AP, Cowan DR, Fellows AM, Zegans ME, Buckey JC. Portable autorefractors for detecting axial length changes in space. Aerosp Med Hum Perform. 2018; 89(8):724-730.

Microgravity-induced ocular changes are related to body weight

On Earth, tissue weight generates compressive forces that press on body structures and act on the walls of vessels throughout the body. In microgravity, tissues no longer have weight, and tissue compressive forces are lost, suggesting that individuals who weigh more may show greater effects from microgravity exposure. One unique effect of long-duration microgravity exposure is spaceflight-associated neuroocular syndrome (SANS), which can present with globe flattening, choroidal folds, optic disk edema, and a hyperopic visual shift. To determine whether weight or other anthropometric measures are related to ocular changes in space, we analyzed data from 45 individual long-duration astronauts (mean age 47, 36 male, 9 female, mean mission duration 165 days) who had pre- and postflight measures of disk edema, choroidal folds, and manifest ocular refraction. The mean preflight weights of astronauts who developed new choroidal folds [78.6 kg with no new folds vs. 88.6 kg with new folds ( F = 6.2, P = 0.02)] and disk edema [79.1 kg with no edema vs. 95 kg with edema ( F = 9.6, P = 0.003)] were significantly greater than those who did not. Chest and waist circumferences were also significantly greater in those who developed folds or edema. The odds of developing disk edema or new choroidal folds were 55% in the highest- and 9% in the lowest-weight quartile. In this cohort, no women developed disk edema or choroidal folds, although women also weighed significantly less than men [62.9 vs. 85.2 kg ( F = 53.2, P < 0.0001)]. Preflight body weight and anthropometric factors may predict microgravity-induced ocular changes.

Intraocular pressure and cardiovascular alterations investigated in artificial gravity as a countermeasure to spaceflight associated neuro-ocular syndrome

Artificial gravity (AG) has been proposed as a countermeasure to spaceflight-associated neuro-ocular syndrome (SANS). The etiology of SANS is unknown but mimicking gravitational loading through AG may mitigate these negative adaptations. Seventeen subjects (nine men, eight women; 18-32 yr) were analyzed in four experimental conditions: 1) standing, 2) supine, 3) AG with the center of rotation at the eye (AGEC), and 4) AG with 2 Gs at the feet (AG2G). In both AG conditions, subjects were spun to produce 1 G at their center of mass. Data included self-administered intraocular pressure (IOP, Tono-pen AVIA, Depew, NY), heart rate (HR), and mean arterial blood pressure (MAP, Omron Series 10, Omron Healthcare, Kyoto, Japan). Data were analyzed with repeated measures ANOVAs with Tukey-Kramer corrections for multiple pairwise comparisons. IOP was 15.7 ± 1.4 mmHg (mean ± 95% confidence interval) standing, 18.8 ± 1.3 mmHg supine, 18.5 ± 1.7 mmHg in AGEC, and 17.5 ± 1.5 mmHg in AG2G. Postures showed a main effect [F(3,48) = 11.0, P < 0.0005], with standing significantly lower than supine ( P = 0.0009), AGEC ( P = 0.002), and AG2G (0.036). Supine, AGEC, and AG2G were not statistically different. HR and MAP were lower in supine compared with all other postures ( P = 0.002 to P < 0.0005), but there were no differences between standing, AGEC, and AG2G. IOP in supine and standing was consistent with previous studies, but contrary to our hypothesis, remained elevated in both AG conditions. Cardiovascular parameters and hydrostatic gradients determine IOP, which remain unchanged compared with standing. These results suggest additional influence on IOP from previously unconsidered factors. NEW & NOTEWORTHY This is the first study, to the authors' knowledge, to measure intraocular pressure in short-radius centrifuge artificial gravity (AG), which has been proposed as a countermeasure to the spaceflight-associated neuro-ocular syndrome (SANS). If the etiology of SANS is related to intraocular pressure, these results have implications for whether or not short-radius AG can be used to prevent ocular changes relevant to it. Our results indicate this proposed countermeasure merits further investigation.

Relaxation with Immersive Natural Scenes Presented Using Virtual Reality

INTRODUCTION

Virtual reality (VR) can provide exposure to nature for those living in isolated confined environments. We evaluated VR-presented natural settings for reducing stress and improving mood.

METHODS

There were 18 participants (9 men, 9 women), ages 32 ± 12 yr, who viewed three 15-min 360° scenes (an indoor control, rural Ireland, and remote beaches). Subjects were mentally stressed with arithmetic before scenes. Electrodermal activity (EDA) and heart rate variability measured psycho-physiological arousal. The Positive and Negative Affect Schedule and the 15-question Modified Reality Judgment and Presence Questionnaire (MRJPQ) measured mood and scene quality.

RESULTS

Reductions in EDA from baseline were greater at the end of the natural scenes compared to the control scene (-0.59, -0.52, and 0.32 μS, respectively). The natural scenes reduced negative affect from baseline ( 1.2 and 1.1 points), but the control scene did not ( 0.4 points). MRJPQ scores for the control scene were lower than both natural scenes (4.9, 6.7, and 6.5 points, respectively). Within the two natural scenes, the preferred scene reduced negative affect ( 2.4 points) more than the second choice scene ( 1.8 points) and scored higher on the MRJPQ (6.8 vs. 6.4 points).

DISCUSSION

Natural scene VR provided relaxation both objectively and subjectively, and scene preference had a significant effect on mood and perception of scene quality. VR may enable relaxation for people living in isolated confined environments, particularly when matched to personal preferences.Anderson AP, Mayer MD, Fellows AM, Cowan DR, Hegel MT, Buckey JC. Relaxation with immersive natural scenes presented using virtual reality. Aerosp Med Hum Perform. 2017; 88(6):520526.

Ocular changes over 60 min in supine and prone postures

Some astronauts are returning from long-duration spaceflight with structural ocular and visual changes. We investigated both the transient and sustained effects of changes in the direction of the gravity vector acting on the eye using changes in body posture. Intraocular pressure (IOP; measured by Perkins tonometer), ocular geometry (axial length, corneal thickness, and aqueous depth-noncontact biometer), and the choroid (volume and subfoveal thickness optical coherence tomography) were measured in 10 subjects (5 males and 5 females). Measures were taken over the course of 60 min and analyzed with repeated-measures analysis of covariance to assess the effects of posture and time. In the supine position, choroidal volume increased significantly with time (average value at <5 min = 8.8 ± 2.3 mm³, 60 min = 9.0 ± 2.4 mm³, P = 0.03). In the prone position, IOP and axial length increased with time (IOP at <5 min 15 ± 2.7 mmHg, 60 min = 19.8 ± 4.1 mmHg, P < 0.0001; axial length at <5 min = 24.29 ± 0.77 mm, 60 min = 24.31 ± 0.76 mm, P = 0.002). Each increased exponentially, with time constants of 5.3 and 14 min, respectively. Prone corneal thickness also increased with time (<5 min = 528 ± 35 μm, 60 min = 537 ± 35 μm³, P < 0.001). Aqueous depth was shortened in the prone position (baseline = 3.22 ± 0.31 mm, 60 min = 3.18 ± 0.32 mm, P < 0.0001) but did not change with time. The data show that changes in the gravity vector have pronounced transient and sustained effects on the geometry and physiology of the eye.NEW & NOTEWORTHY We show that gravity has pronounced transient and sustained effects on the eye by making detailed ocular measurements over 60 min in the supine and prone postures. These data inform our understanding of how gravitational forces can affect ocular structures, which is essential for hypothesizing how ocular changes could occur with microgravity exposure.

Autonomous, Computer-Based Behavioral Health Countermeasure Evaluation at HI-SEAS Mars Analog

INTRODUCTION

Living in an isolated, confined environment (ICE) can induce conflict, stress, and depression. Computer-based behavioral health countermeasures are appealing for training and treatment in ICEs because they provide confidentiality and do not require communication with the outside environment. We evaluated the Virtual Space Station (VSS), a suite of interactive computer-delivered psychological training and treatment programs, at the Hawaii Space Exploration Analog and Simulation (HI-SEAS) III expedition.

METHODS

Six subjects (3 male, 3 female) spent 8 mo in group-isolation and used the Conflict, Stress, and Depression modules in the VSS. Survey evaluations, data collected within the program, and postdeployment interviews were collected.

RESULTS

This crew dealt with behavioral health issues common to ICEs. The VSS proved to be a valuable resource and was used both as intended, and in unanticipated ways, to help maintain behavioral health. The Conflict and Stress Modules were rated as highly acceptable (1.8 on a 7-point Likert scale). The crew identified a total of 13 stressors and worked on 9 problems through the VSS. Opinions about the modules were highly individualized. Crewmembers identified exercises in the VSS that were applicable and not applicable to their needs. Additional content to improve the program was identified.

DISCUSSION

Autonomous, confidential training and treatment for behavioral health issues will need to be a critical component of long duration spaceflight travel. This work provides an evaluation of such a tool in a relevant ICE. Anderson AP, Fellows AM, Binsted KA, Hegel MT, Buckey JC. Autonomous, computer-based behavioral health countermeasure evaluation at HI-SEAS Mars analog. Aerosp Med Hum Perform. 2016; 87(11):912-920.

Acute effects of changes to the gravitational vector on the eye

Intraocular pressure (IOP) initially increases when an individual enters microgravity compared with baseline values when an individual is in a seated position. This has been attributed to a headward fluid shift that increases venous pressures in the head. The change in IOP exceeds changes measured immediately after moving from seated to supine postures on Earth, when a similar fluid shift is produced. Furthermore, central venous and cerebrospinal fluid pressures are at or below supine position levels when measured initially upon entering microgravity, unlike when moving from seated to supine postures on Earth, when these pressures increase. To investigate the effects of altering gravitational forces on the eye, we made ocular measurements on 24 subjects (13 men, 11 women) in the seated, supine, and prone positions in the laboratory, and upon entering microgravity during parabolic flight. IOP in microgravity (16.3 ± 2.7 mmHg) was significantly elevated above values in the seated (11.5 ± 2.0 mmHg) and supine (13.7 ± 3.0 mmHg) positions, and was significantly less than pressure in the prone position (20.3 ± 2.6 mmHg). In all measurements, P < 0.001. Choroidal area was significantly increased in subjects in a microgravity environment ( P < 0.007) compared with values from subjects in seated (increase of 0.09 ± 0.1 mm2) and supine (increase of 0.06 ± 0.09 mm2) positions. IOP results are consistent with the hypothesis that hydrostatic gradients affect IOP, and may explain how IOP can increase beyond supine values in microgravity when central venous and intracranial pressure do not. Understanding gravitational effects on the eye may help develop hypotheses for how microgravity-induced visual changes develop.

Statistical Evaluation of Causal Factors Associated with Astronaut Shoulder Injury in Space Suits

INTRODUCTION

Shoulder injuries due to working inside the space suit are some of the most serious and debilitating injuries astronauts encounter. Space suit injuries occur primarily in the Neutral Buoyancy Laboratory (NBL) underwater training facility due to accumulated musculoskeletal stress. We quantitatively explored the underlying causal mechanisms of injury.

METHODS

Logistic regression was used to identify relevant space suit components, training environment variables, and anthropometric dimensions related to an increased propensity for space-suited injury. Two groups of subjects were analyzed: those whose reported shoulder incident is attributable to the NBL or working in the space suit, and those whose shoulder incidence began in active duty, meaning working in the suit could be a contributing factor.

RESULTS

For both groups, percent of training performed in the space suit planar hard upper torso (HUT) was the most important predictor variable for injury. Frequency of training and recovery between training were also significant metrics. The most relevant anthropometric dimensions were bideltoid breadth, expanded chest depth, and shoulder circumference. Finally, record of previous injury was found to be a relevant predictor for subsequent injury. The first statistical model correctly identifies 39% of injured subjects, while the second model correctly identifies 68% of injured subjects.

DISCUSSION

A review of the literature suggests this is the first work to quantitatively evaluate the hypothesized causal mechanisms of all space-suited shoulder injuries. Although limited in predictive capability, each of the identified variables can be monitored and modified operationally to reduce future impacts on an astronaut's health.

First clinical results with a real time, electronic imager as an aid to colonoscopy

The early clinical results are described of a real time, electromagnetic imaging system as an aid to colonoscopy. After gaining experience with the use of the system, one experienced endoscopist was randomised to perform consecutive colonoscopies either with (n = 29) or without (n = 26) the imager view. All procedures were recorded on computer disk and replayed for retrospective analysis. Total colonoscopy was achieved in all patients except one (imager view not available). Comparing intubation time and duration of loop formation per patient, there was no significant difference between the two study groups. The number of attempts taken to straighten the colonoscope pre patient, however, was less when the endoscopist was able to see the imager view, p = 0.03. Hand pressure was also more effective when the endoscopist and endoscopy assistant could see the imager display, p = 0.02. Preliminary experience suggests that real time, electronic imaging of colonoscopy is safe, effective, and will improve the accuracy of the procedure.

Pharmacological properties of the natural marine product furospongin-1

1. The natural marine product, furospongin-1 (6, 12 and 24.5 mumol/L) significantly inhibited contractions of segments of guinea-pig ileum induced by submaximal concentrations (0.1 mumol/L) of acetylcholine (ACh) and histamine. Furospongin-1 (24.5 and 36.7 mumol/L) reduced both the phasic and tonic components of a contraction induced by 30 mumol/L K+ solution in the absence and presence of atropine (1 mumol/L), mepyramine (1 mumol/L) and phentolamine (1 mumol/L). Furospongin-1 also decreased basal tension and the amplitude of spontaneous phasic contractions of guinea-pig ileum. 2. The mitochondrial ATP synthase inhibitor oligomycin (0.3, 1 and 3 mumol/L) had a similar concentration-dependent action, reducing basal activity and contractions evoked by histamine and ACh. Oligomycin also reduced both the phasic and tonic components of a contraction induced by 30 mmol/L K+ solution in the absence and presence of atropine (1 mumol/L), mepyramine (1 mumol/L) and phentolamine (1 mumol/L). 3. Furospongin-1 (6 and 37.6 mumol/L) and oligomycin (3 mumol/L) had no effect on contractions of chemically skinned guinea-pig ileum longitudinal muscle segments. In this same tissue, furospongin-1 (6, 12 and 24.5 mumol/L) and oligomycin (0.3, 1 and 3 mumol/L) concentration-dependently reduced tissue levels of ATP. 4. In lyzed bovine mitochondria, oligomycin (0.1, 0.3, 1 and 3 mumol/L) inhibited conversion of ATP to ADP whilst furospongin-1 (6, 12 and 24.5 mumol/L) and carbonyl cyanide m-chlorophenylhydrazone (0.5 mmol/L) had no significant effect on ATP breakdown.(ABSTRACT TRUNCATED AT 250 WORDS)

The marine natural product 3,5-dibromo-2-(2,4-dibromo-phenoxy)phenol, inhibits contractile activity in the guinea-pig ileum

1. The tetrabrominated diphenyl ether 3,5-dibromo-2-(2,4-dibromophenoxy)phenol (BPE), a natural marine product isolated from a sponge, was tested for pharmacological activity in guinea-pig ileum. 2. BPE (2 mumol/L) decreased basal force and the frequency of spontaneous contractions of the ileum. It also significantly decreased contractions of the ileum induced by 5 mmol/L barium and to electrical stimulation at parameters which stimulated intrinsic nerves. 3. The slopes of concentration-response curves to acetylcholine (ACh), histamine and 5-hydroxytryptamine (5-HT) were significantly reduced by BPE at concentrations of 2 mumol/L or greater. 4. BPE (2 mumol/L) did not affect calcium-induced contractions of longitudinal muscle fibres from guinea-pig ileum which were stripped of their cellular membrane. It (6 mumol/L) also had no effect on ATP levels in longitudinal muscle fibres. 5. BPE (2 mumol/L) reduced both phasic and tonic components of contractions induced by raising the extracellular concentration of K+ to 15, 30, 45 or 60 mmol/L (in the presence of atropine, propranolol, phentolamine and desensitization to 5-HT to inhibit the effects of nerve transmitter release). 6. BPE (2 mumol/L) reduced carbachol-induced contractions of ileum pre-incubated in 1 mumol/L felodipine, a blocker of L-type voltage-operated calcium channels (VOCC). 7. BPE dose dependently (0.6-6 mumol/L) reduced contractions induced by Ca2+ in both K+ depolarized ileum and in tissue exposed to carbachol (10 mumol/L) in the presence of felodipine (0.1 mumol/L). 8. These results suggest that BPE affects intracellular messenger systems controlling cytosolic calcium and/or blocks entry of calcium into the cell through both VOCC and receptor-operated channels (ROC).

Non-radiological technique for three-dimensional imaging of endoscopes

A novel system is described which images in three dimensions, the total configuration of a colonoscope without the use of conventional radiological techniques. A low intensity magnetic field is used in conjunction with a miniature inductive sensor. The system intrinsically safe and it is potentially inexpensive and capable of being used in a normal hospital environment. Clinical trials are described in which the system is validated in terms of its suitability for the application. Magnetic and conventional X-ray images obtained ex vivo with the endoscope held in various configurations and comparisons in the patients confirm the practical applicability of the new system.

A robot-controlled microwave antenna system for uniform hyperthermia treatment of superficial tumours with arbitrary shape

A system for microwave hyperthermia by scanning an antenna 'footprint' over a disease site is demonstrated. A computer-controlled robot arm scans a 2.45 GHz helical antenna and controls the absorbed power distribution. The 'ideal' power distribution required to achieve steady-state temperature uniformity over a given region has been calculated and a corresponding antenna trajectory programmed to approximate this pattern. Computer models, based on the solution of the bio-heat equation, have been implemented to allow various system parameters, such as antenna beam size, scan path and velocity profile, to be optimized. Experiments on a homogeneous muscle-equivalent phantom have shown that the scanning antenna system produces uniform temperature distributions over large areas of arbitrary shape. The addition of a thermal control system, based on temperature signal feedback, would enable 'real-time' modification of the power distribution and allow inhomogeneous and perfused tissue structures to be heated more uniformly.

Quantitative assessment of impedance tomography for temperature measurements in microwave hyperthermia

The objective of this study is a non-invasive assessment of the thermal dose in microwave hyperthermia. We intend to monitor the induced temperature rise via the change in the resistivity of body tissue, and hence control the microwave power during treatment. An initial feasibility study using electrical impedance tomography in vivo has indicated that a microwave induced temperature difference of a suitable magnitude can be mapped from a knowledge of the temperature coefficient of conductivity for tissue (typically 2% per degrees C). The accuracy of the currently employed reconstruction algorithm is assessed from data simulated by finite element prediction methods. A circular arrangement of electrodes surrounding a conductive sheet is used to evaluate the voltage distribution on the boundary of the sheet. A range of regions inside the circular field are chosen and the conductivity is changed uniformly by steps of 1% up to 10%. Images of these changes are produced. It is noticed that the algorithm underestimates the values of resistivity change for the small areas and overestimates the change for the larger areas. We are studying results for a variety of shapes of surface regions of the body that undergo resistivity change with microwave heating applied. Further work is necessary to account for three-dimensional current paths. Preliminary results are also presented of experimental investigations of the microwave-induced temperature rise in layers of carbon-loaded paper sheet.

The influence of tissue layering on microwave thermographic measurements

Non-invasive thermal imaging and temperature measurement by microwave radiometry has been investigated for medical diagnostic applications and monitoring hyperthermia treatment of cancer, in the context of heterogeneous body structure. The temperature measured by a radiometer is a function of the emission and propagation of microwaves in tissue and the receiving characteristics of the radiometric probe. Propagation of microwaves in lossy media was analysed by a spectral diffraction approach. Extension of this technique via a cascade transmission line model provides an efficient algorithm for predicting the field patterns of aperture antennas contacting multi-layered tissue. A coherent radiative transfer analysis was used to relate the field pattern of a radiating antenna to its receiving characteristics when used as a radiometer probe, leading to a method for simulating radiometric data. Measurements and simulations were used to assess the effect of overlying fat layers upon radiometer response to temperature hot spots in muscle-type media. Results suggest that dielectric layering in tissue greatly influences measured temperatures and should be accounted for in the interpretation of radiometric data.

A feasibility study of microwave thermographic mapping for use during hyperthermia treatment

A study to assess the possible use of a microwave radiometric system for tomographic thermal mapping during hyperthermia treatment has been examined using a computer model. Results indicate that as few as ten waveguide probes in contact with the body may be sufficient for spatial resolution of the heated region. A single probe microwave radiometer has been constructed and used to obtain scan data in a water phantom as an initial stage in the verification of the computer results.

Studies in burns: XIV, Heling in burn wounds treated with Ethyl Linoleate alone or in combination with selected topical antibacterial agents

Studies of the efficacy, in terms of burned wound healing, of a mixture of Ethyl Linoleate (ethyl 9-12 (cis, cis) octadecadienoate) with alpha-1-histidine, alpha-tocopherol, and TBHQ (hELate) was undertaken in 12 swine. The species was selected so as to study an animal with skin anatomy similar to the human. Statistically significantly greater healing occurred in 730 C/7sec contact burns (20% BSA) treated with hELate than in untreated burns in pigs. Further, there was no contracture noted in the hELate treated lesions, while marked contracture occurred in the untreated burns. Additionally, we noted that there was a proportional increase in weight gain amongst swine studied as their burn lesions epithelialized. In order to evaluate the compatibility of hELate with selected, currently-used topical antibacterial agents, 154 rabbits with 20% 730 C/7 sec contact burns were studied. The lipid was applied (0.01 ml/cm2 burn) at 1 hour postburning; the topical agent was applied at 2 hours post-burn and every 24-hours. All animals were washed once daily. hELate was applied only once. We found no statistical difference in the number of subjects healed or in the mortality between animals treated with hELate alone and those treated with the agent plus Gentamycin cream, Neosporin cream, and silver sulfadiazine 1% in Unibase USP (compounded at Medical College of Georgia specifically and only for this study.) We suggest that Ethyl Linoleate agent (hELate) may be used safely in combination with selected antibacterial substances. Further, these selected combinations seem to be non-toxic and appear to allow the calorie-saving and healing effects of the lipid to proceed unimpeded.

Studies in burns. XIII. Effects of a topical lipid on burned subjects and their wounds

We evaluated ethyl linoleate (ethyl, (9, 12)-cic, cis-octadecadienoate), a naturally occurring cutaneous water-holding lipid, for its water-holding metabolic, healing and toxic properties in groups of unburned and burned rabbits and its toxic potentials in this species and mice. The lipid appears to reduce evaporative water loss in full-thickness burned rabbits. Associated with this effect is a proportional and related lowering of metabolic heat production. The topical application of the lipid at any time after burn appears to be associated with a significant healing in lesions that, histologically at least, would be interpreted as fullthickness. The material is highly toxic if applied daily to mice or rabbits. The details of the toxic effect (s) are being studied. The commerical-grade material (75 percent pure) contains a derivative of ricinoleci acid and chronic exposure of the EL to air may result in the formation of peroxides and epoxides. These materials exert well-defined toxicity. The obvious potential uses of this agent in treating human burn lesions need not be emphasized, but it does need to be stated categorically that, at present, (Feb 1974), the toxicity has not been defined enough for use except in experiments.