United States Army Aeromedical Research Lab

A flash method of measuring the thermal diffusivity, heat capacity, and thermal conductivity is described for the first time. A high-intensity short-duration light pulse is absorbed in the front surface of a thermally insulated specimen a few millimeters thick coated with camphor black, and the resulting temperature history of the rear surface is measured by a thermocouple and recorded with an oscilloscope and camera. The thermal diffusivity is determined by the shape of the temperature versus time curve at the rear surface, the heat capacity by the maximum temperature indicated by the thermocouple, and the thermal conductivity by the product of the heat capacity, thermal diffusivity, and the density. These three thermal properties are determined for copper, silver, iron, nickel, aluminum, tin, zinc, and some alloys at 22°C and 135°C and compared with previously reported values.

IMPORTANCE: Prehospital blood product transfusion in trauma care remains controversial due to poor-quality evidence and cost. Sequential expansion of blood transfusion capability after 2012 to deployed military medical evacuation (MEDEVAC) units enabled a concurrent cohort study to focus on the timing as well as the location of the initial transfusion. OBJECTIVE: To examine the association of prehospital transfusion and time to initial transfusion with injury survival. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cohort study of US military combat casualties in Afghanistan between April 1, 2012, and August 7, 2015. Eligible patients were rescued alive by MEDEVAC from point of injury with either (1) a traumatic limb amputation at or above the knee or elbow or (2) shock defined as a systolic blood pressure of less than 90 mm Hg or a heart rate greater than 120 beats per minute. EXPOSURES: Initiation of prehospital transfusion and time from MEDEVAC rescue to first transfusion, regardless of location (ie, prior to or during hospitalization). Transfusion recipients were compared with nonrecipients (unexposed) for whom transfusion was delayed or not given. MAIN OUTCOMES AND MEASURES: Mortality at 24 hours and 30 days after MEDEVAC rescue were coprimary outcomes. To balance injury severity, nonrecipients of prehospital transfusion were frequency matched to recipients by mechanism of injury, prehospital shock, severity of limb amputation, head injury, and torso hemorrhage. Cox regression was stratified by matched groups and also adjusted for age, injury year, transport team, tourniquet use, and time to MEDEVAC rescue. RESULTS: Of 502 patients (median age, 25 years [interquartile range, 22 to 29 years]; 98% male), 3 of 55 prehospital transfusion recipients (5%) and 85 of 447 nonrecipients (19%) died within 24 hours of MEDEVAC rescue (between-group difference, -14% [95% CI, -21% to -6%]; P = .01). By day 30, 6 recipients (11%) and 102 nonrecipients (23%) died (between-group difference, -12% [95% CI, -21% to -2%]; P = .04). For the 386 patients without missing covariate data among the 400 patients within the matched groups, the adjusted hazard ratio for mortality associated with prehospital transfusion was 0.26 (95% CI, 0.08 to 0.84, P = .02) over 24 hours (3 deaths among 54 recipients vs 67 deaths among 332 matched nonrecipients) and 0.39 (95% CI, 0.16 to 0.92, P = .03) over 30 days (6 vs 76 deaths, respectively). Time to initial transfusion, regardless of location (prehospital or during hospitalization), was associated with reduced 24-hour mortality only up to 15 minutes after MEDEVAC rescue (median, 36 minutes after injury; adjusted hazard ratio, 0.17 [95% CI, 0.04 to 0.73], P = .02; there were 2 deaths among 62 recipients vs 68 deaths among 324 delayed transfusion recipients or nonrecipients). CONCLUSIONS AND RELEVANCE: Among medically evacuated US military combat causalities in Afghanistan, blood product transfusion prehospital or within minutes of injury was associated with greater 24-hour and 30-day survival than delayed transfusion or no transfusion. The findings support prehospital transfusion in this setting.

Abstract The physiological and psychological stressors associated with sustained work, fatigue, and sleep loss affect worker performance. This review describes findings relating to sustained work stresses commonly found in our advancing technological world. Researchers report decrements in sustained performance as a function of fatigue, especially during and following one or more nights of complete sleep loss, or longer periods of reduced or fragmented sleep. Sleep loss appears to result in reduced reaction time, decreased vigilance, perceptual and cognitive distortions, and changes in affect. Sleep loss and workload interact with circadian rhythms in producing their effects. These interactions are a major source of stress in work situations requiring sustained work in continuous operations and have implications for theoretical models of sustained perceptual and cognitive functioning. Key Words: FatigueSleep deprivationSustained workContinuous performanceContinuous operationsCircadian rhythms

Human error (HE) has been implicated in 70-80% of civil/military aviation accidents. Yet, most accident reporting systems are not designed around any theoretical framework of HE. As a result, most accident databases are not conducive to traditional HE analysis, making the identification of intervention strategies onerous. A general HE framework is required around which new investigative methods can be designed and existing accident databases restructured. A comprehensive human factors analysis and classification system (HFACS) has recently been developed to meet those needs. The HFACS framework has been used successfully within the military, commercial, and general aviation sectors to systematically examine underlying human causal factors and improve aviation accident investigations. This paper describes the development and theoretical underpinnings of HFACS in the hope that it will help safety professionals reduce the aviation accident rate through systematic data-driven investment strategies and the objective evaluation of intervention programs.

The purpose of the present study was to assess the occurrence of visual dysfunctions and associated symptoms in active duty warfighters during the subacute stage of blast-induced mild traumatic brain injury (mTBI). A comprehensive visual and oculomotor function evaluation was performed on 40 U.S. military personnel, 20 with blast-induced mTBI and 20 without. In addition, a comprehensive symptom questionnaire was used to assess the frequency of visual, vestibular, and neuropsychiatric-associated symptoms. The most common mTBI-induced visual dysfunctions were associated with near oculomotor deficits, particularly large exophoria, decreased fusion ranges, receded near point of convergence, defective pursuit and saccadic eye movements, decreased amplitude of accommodation, and monocular accommodative facility. These were associated with reduced reading speed and comprehension and an increased Convergence Insufficiency Symptom Survey score. Photosensitivity was a common visual dysfunction along with hearing, balance, and neuropsychiatric symptoms. The oculomotor testing for warfighters suspected of blast-induced mTBI should include, at a minimum, the assessment of near lateral and vertical phorias, positive fusional vergence, stereoacuity, near point of convergence, amplitude of accommodation, monocular accommodative facility, saccades, and pursuit eye movements. A reading test should be included in all routine exams as a functional assessment of the integration of oculomotor functions.

The conditions for the hydroxamic acid reaction for determining esterified fatty acids have been modified to control the variable factors involved and to obtain molar absorptivities per ester group for triglycerides, cholesterol esters of long-chain fatty acids, and phosphatides that are equivalent for amounts up to 8 μEq of ester. Control of the amount of water present during the formation of hydroxamates was the most important single factor in obtaining equivalent color values. The accuracy and precision of the method have been well defined by showing that the optical density values for five different ester standards were on the identical straight-line curve. The colored end-products gave identical spectral curves between the wavelengths of 410 mμ and 700 mμ whether they were derived from standard carboxylic acid esters, Folch extracts of rat serum, rat liver, or human serum. A long-chain cholesterol ester must be used as one of the standard esters because of its special solubility characteristics. Cholesteryl acetate cannot be used as a reliable representative in place of a long-chain cholesterol ester.

Changes in the composition of the whole body and of subcutaneous adipose tissue have been studied during weight reduction in two human subjects. The whole body lost tissues ranging in density from 0.92 to 0.96 gm/ml at body temperature, consisting of 55–85% fat. The adipose tissue fat contents fell during weight loss from 80–85% to 65–80% of the whole tissue, or by about 50% when related to the dry, defatted residue. The densities of fat depots increased, therefore, as a result of the excess loss of tissue fat. Adipose tissue densities calculated from chemical composition agreed well with the values obtained by indirect determination. From these observations it is concluded that while adipose tissues probably contributed the greatest portion of the fat and body weight loss during weight reduction, other soft tissues also contribute significantly to the body weight decrease by losing nonfat components. Adipose tissue components are not lost uniformly during body weight loss in the human. Submitted on September 13, 1957

Unpressurized aircraft routinely operate at altitudes where hypoxia may be of concern. A systematic literature review was conducted regarding hypoxic impairment, including mental functions, sensory deficits, and other pertinent research findings that may affect aviation-related duties at moderate altitude (8000 to 15,000 ft/2438 to 4572 m). The results of this review suggest that cognitive and psychomotor deficits may include learning, reaction time, decision-making, and certain types of memory. However, results are difficult to quantify and reliably reproduce. Inconsistency of results may be related to the subtlety of deficits compared to high altitude, differences among individual compensatory mechanisms, variation in methodology or sensitivity of metrics, presence or absence of exercise, heterogeneous neuronal central nervous system (CNS) response, and interindividual variation. Literature regarding hypoxic visual decrements is more consistent. Rod photoreceptors are more susceptible to hypoxia; visual degradation has been demonstrated at 4000 to 5000 ft (1219 to 1524 m) under scotopic and 10,000 ft (3048 m) under photopic conditions. Augmented night vision goggle resolution demonstrates more resilience to mild hypoxic effects than the unaided eye under starlight conditions. Hypocapnia enhances visual sensitivity and contrast discrimination. Hyperventilation with resulting respiratory alkalosis and cerebral vasoconstriction may confound both cognitive/ psychomotor and visual experimental results. Future research should include augmentation of validated neuropsychological metrics (surrogate investigational end points) with actual flight metrics, investigation of mixed gas formulations, contribution of hypocapnic vasoconstrictive effects on hypoxic performance, and further investigation into cellular- and systems-level approaches for heterogeneous CNS response. Research is also required into the contribution of mild-moderate hypoxia in human factors- and spatial disorientation-related mishaps.

Abstract The distribution of circulating blood has been studied in the arousing hibernator following the method of fractional distribution of radioactive indicators (S apirstein 1958). The results indicate a conspicuous differential vasoconstriction of the posterior part of the animal during the most active phase of arousal. The blood flow to skeletal muscle in the front of the arousing animals is more than 16 times greater than in the awake non‐hibernating animals. The perfusion rate to the myocardium is twice as large in the arousing animal. Likewise the lungs, diaphragm, and brown fat show a substantial increase in blood flow. Blood flow to gastrointestinal tissues is greatly reduced in the arousing animals, whereas flow to the skin, liver and thyroid shows insignificant differences.

The color centers and free radicals produced in irradiated solid alcohols, ketones, ethers, and other compounds have been examined experimentally by means of optical absorption and EPR spectroscopy to obtain information regarding the products of ionization and the associated electronic processes. At liquid nitrogen temperature these products of electron or x-ray bombardment are stable; however, the color centers are photosensitive and can be bleached both optically and thermally. The alcohols also show an increase in absorption near the characteristic uv bands. Removing the visible color centers increases the EPR hfs, but bleaching in the uv band markedly reduces or changes the hfs. In methanol and ethanol, free radicals are formed with good efficiency requiring about 18 and 12 ev per radical, respectively. Saturation concentrations of 2×1019 and 9×1019 spins per cc were produced in acetone and methanol, respectively. The hfs of ethanol and methanol indicate an alkyl hydrogen is missing from the radicals produced by irradiating these materials. No sign of the atomic hydrogen doublet was observed at liquid nitrogen temperature. Support for the α—β hypothesis was found in the hfs displayed by the irradiated alcohols, paraffins, ketones, and ethers.

The cells of the popliteal lymph nodes of rats were labeled for 4 days after a secondary immunological stimulus. 31 days after the last dose of tritiated thymidine, groups of rats were started on courses of daily, intraperitoneal injections of prednisone, cyclophosphamide, 6-mercaptopurine, or actinomycin D. The initially low doses of these agents were doubled in successive weeks until either lymphoid hypoplasia or death occurred. Rats from each group were killed weekly, and the percentages of persisting, labeled small lymphocytes in the popliteal nodes were determined. Sections of these nodes were examined for persisting, labeled plasma cells. The per cent of lymphocytes labeled increased while the total number of lymphocytes decreased during treatment with prednisone and cyclophosphamide. Prednisone decreased the numbers of long-lived plasma cells, but these cells were preferentially resistant to cyclophosphamide. Neither 6-mercaptopurine nor actinomycin D had an appreciable effect on lymphoid tissues histologically nor on the proportions of labeled, long-lived lymphocytes and plasma cells before causing the deaths of the rats receiving them. These results indicate that long-lived lymphocytes and plasma cells survive treatment with the immunolytic drugs studied, and that long-lived lymphocytes are specifically resistant to prednisone and cyclophosphamide. We believe these results have an application to the attempts to find drugs useful in the treatment of immunologic rejections of organ transplants, and for therapy of autoimmune diseases.

OBJECTIVES: Military service members risk acquiring posttraumatic stress disorder (PTSD) and mild-traumatic brain injury (mTBI), with high comorbidity. Owing to overlapping symptomatology in chronic mTBI or postconcussion syndrome (PCS) and PTSD, it is difficult to assess the etiology of a patient's condition without objective measures. Using resting-state functional MRI in a novel framework, we tested the hypothesis that their neural signatures are characterized by functionally hyperconnected brain regions which are less variable over time. Additionally, we predicted that such connectivities possessed the highest ability in predicting the diagnostic membership of a novel subject (top-predictors) in addition to being statistically significant. METHODS: U.S. Army Soldiers (N = 87) with PTSD and comorbid PCS + PTSD were recruited along with combat controls. Static and dynamic functional connectivities were evaluated. Group differences were obtained in accordance with our hypothesis. Machine learning classification (MLC) was employed to determine top predictors. RESULTS: From whole-brain connectivity, we identified the hippocampus-striatum connectivity to be significantly altered in accordance with our hypothesis. Diffusion tractography revealed compromised white-matter integrity between aforementioned regions only in the PCS + PTSD group, suggesting a structural etiology for the PCS + PTSD group rather than being an extreme subset of PTSD. Employing MLC, connectivities provided worst-case accuracy of 84% (9% more than psychological measures). Additionally, the hippocampus-striatum connectivities were found to be top predictors and thus a potential biomarker of PTSD/mTBI. CONCLUSIONS: PTSD/mTBI are associated with hippocampal-striatal hyperconnectivity from which it is difficult to disengage, leading to a habit-like response toward episodic traumatic memories, which fits well with behavioral manifestations of combat-related PTSD/mTBI. Hum Brain Mapp 38:2843-2864, 2017. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

The diagnosis and management of concussion can be difficult in a combat environment, especially in the absence of loss of consciousness or post-traumatic amnesia. As no validated test exists to diagnose or grade neurocognitive impairment from a concussion, the military currently employs the Military Acute Concussion Evaluation (MACE) in Iraq. This is a two-part test, which incorporates the standardized assessment of concussion (SAC) as its objective score, although it has not been shown to be valid unless administered shortly after injury. A research team deployed to Iraq between January and April 2009 to examine the validity of several tests of neurocognitive function following a concussion, including the MACE. When administered more than 12 hours after the concussive injury, the MACE lacked sufficient sensitivity and specificity to be clinically useful.

Fatigue is an insidious threat to aviation safety because of the impairments in alertness and performance it creates. The fatigue associated with sleep loss, shift work, and long duty cycles can cause aviators to become sloppy, inattentive, careless, and inefficient. The only cure for fatigue is adequate sleep; however, gaining sufficient amounts of sleep is often difficult because of work requirements, family demands, or poor sleep habits. Although it may not be possible to avoid some of these problems, pilots can improve their sleep habits and thus gain more restful and restorative sleep by using self-administered relaxation therapy, establishing consistent and soothing bedtime routines, and avoiding certain activities and substances immediately prior to sleep. When opportunities for adequate sleep are not available because of work-related factors, prophylactic naps can sustain performance until sleep is possible.

INTRODUCTION: Successful military aviation operations depend on maintaining continuous day-night operations. Stimulants are easy to use and popular for sustaining performance because their utility is not dependent upon environmental or scheduling modifications. Dextroamphetamine is authorized for use by the aircrews of all U.S. military services, but its potential for abuse and subsequent addiction is of aeromedical concern. Finding an alternative stimulant, such as modafinil, that displays a low affinity for dopamine uptake binding sites would prove extremely beneficial. This study sought to establish the efficacy and safety of modafinil during actual flying operations, thus providing the operational validity desired to approve the use of modafinil for helicopter flight operations. METHODS: During two, 40-h periods of sustained wakefulness, 18 helicopter pilots (17 men, 1 woman, mean years of age = 29.5) each completed 15 flights and other evaluations, during which they received 2 of 3 experimental conditions: 3 doses at 4-h intervals of modafinil (100 mg), dextroamphetamine (5 mg), or placebo. RESULTS: Statistical results showed that modafinil, like dextroamphetamine, maintained alertness, feelings of well-being, cognitive function, judgment, risk perception, and situation awareness of sleep-deprived aviators consistently better than placebo and without side effects of aeromedical concern. DISCUSSION: Like previous research, this study strongly suggests that both drugs can maintain acceptable levels of mood and performance during sleep deprivation. The results also confirm that modafinil is well tolerated and appears to be a good alternative to dextroamphetamine for countering the debilitating mood and cognitive effects of sleep loss during sustained operations.

Expressions are developed which give the amount of unidirectional radiation from a distant radiation source passing through a cylindrical hole in a slab of material, including the amount of radiation which penetrates the edges of the hole, as a function of angle between the radiation direction and the axis of the hole. The modifications necessary for sources at finite distances are indicated. These functions are integrated over appropriate angles for distant line sources, and for extended sources. It is shown that, to a first approximation, the results are the same as the geometrical aperture for a like diameter hole in a similar slab with one mean free path of material removed from each side. The effects due to scattering from the walls of the collimator are discussed and an approximate method of calculation is presented with results for a specific collimator.

The mandate of ASA Working Group S12/WG11 has been to develop "laboratory and/or field procedure(s) that yield useful estimates of field performance" of hearing protection devices (HPDs). A real-ear attenuation at threshold procedure was selected, devised, tested via an interlaboratory study, and incorporated into a draft standard that was approved in 1997 [J. D. Royster et at., "Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise," J. Acoust. Soc. Am. 99, 1506-1526 (1996); ANSI S12.6-1997, "American National Standard Methods for Measuring Real-Ear Attenuation of Hearing Protectors" (American National Standards Institute, New York, 1997)]. The real-world estimation procedure utilizes a subject-fit methodology with listeners who are audiometrically proficient, but inexperienced in the use of HPDs. A key factor in the decision to utilize the subject-fit method was an evaluation of the representativeness of the laboratory data vis-à-vis attenuation values achieved by workers in practice. Twenty-two field studies were reviewed to develop a data base for comparison purposes. Results indicated that laboratory subject-fit attenuation values were typically equivalent to or greater than the field attenuation values, and yielded a better estimate of those values than did experimenter-fit or experimenter-supervised fit types of results. Recent data which are discussed in the paper, but which were not available at the time of the original analyses, confirm the findings.

To explore the cross-sectional relationships between blood eicosapentaenoic acid + docosahexaenoic acid (HSOmega-3 Index(®)) and sleep disorders, depression, anxiety, and neurocognitive performance in Servicemembers deployed to Iraq.Servicemembers with mild-to-moderate depression by the Patient Health Questionnarie-9 from two US military camps were invited to participate in this study. A battery of validated psychosocial (Pittsburgh Sleep Quality Index, and Zung Depression, Zung Anxiety, Epworth Sleepiness, and Combat Experiences scales) and computerized neurocognitive tests were completed by each participant. Five neurocognitive domain scores were calculated--Processing Speed, Complex Attention, Reaction Time, Cognitive Flexibility (CF), and Executive Function (EF). A drop of blood was also collected on an anti-oxidant-treated filter paper card and sent for HS-Omega-3 Index(®) analysis. An analysis of variance contrast was used to test for linear trends between quartiles of the HS-Omega-3 Index(®) for both EF and CF.The mean HS-Omega-3 Index(®) was 3.5 ± 0.7% (n = 78). The HS-Omega-3 Index(®) was not significantly associated with scores for anxiety, depression, or sleep, whether assessed as continuous or dichotomous variables, but was directly associated with CF and EF (P < 0.02 and 0.01, respectively), especially in the 81% who reported poor sleep quality. In those with poor sleep quality (n = 63), EF and CF were higher (P = 0.005) in subjects with Omega-3 levels above versus below the mean.Optimal neurocognitive performance is essential during deployment. Our finding that EF and CF were positively related to HS-Omega-3 Index(®) suggests that improving omega-3 status through an increase in omega-3 intake may improve neurocognitive performance and confer an element of resilience to poor sleep.

Studies on animals and human subjects have proposed that urban pollutants may cause alterations of cortisol levels. The aim of this study is to evaluate whether police officers exposed to urban pollutants and possible psycho-social stressors could be at risk for alterations on plasma cortisol levels compared to a control group. Plasma cortisol levels were determined in 302 police officers with outdoor activity and administrative workers with indoor activity. The subjects were subdivided into three groups: "A" (non-smokers and non-drinkers), "B" (smokers), and "C" group (drinkers). In male and female subjects of "A" and "C" groups and in female subjects of "B" group the mean cortisol values were significantly higher in police officers compared to controls. The authors hypothesise an effect on plasma cortisol levels in police officers exposed to chemical, physical and possible psycho-social stressors.

Data on the induction of fluorescence in malignant tumors by means of the recrystallized hematoporphyrin derivative (Hp-D) are currently available. Recent improvements in the quality of available Hp-D, violet light sources, light carriers, and flexible fiberoptic bronchoscopes appear to warrant further examination of this technique for localization of early cancer. A protocol can be developed for utilization of Hp-D in the localization of in-situ and early invasive bronchogenic carcinoma.