Naval Aerospace Medical Institute

Four subjects in each of four different body orientations were exposed to periodic linear acceleration stimuli produced by simple harmonic translation of 0.2, 0.4, and 0.8 cps cyclic frequency along an Earthhorizontal axis. Highly systematic horizontal nystagmus was demonstrated in response to these stimuli as well as to linear accelerations of rotating vector form equivalent to counterrotation in a constant magnitude linear force field. Vertical nystagmus could not be demonstrated for similar stimuli. The peak velocity of the slow component of nystagmus and the phase lag of the nystagmic response behind the linear acceleration stimulus were found to differ from those associated with periodic angular stimulation of the semicircular canals in a comparable frequency range. Regardless of stimulus form, the effective stimulus element for elicitation of horizontal nystagmus appeared to be dynamic change in the linear acceleration component directed along the subject's y (left-right) head axis.

The Tactical Combat Casualty Care (TCCC) project begun by the Naval Special Warfare Command and continued by the U.S. Special Operations Command developed a set of tactically appropriate battlefield trauma care guidelines that were initially published in 1996. Transition of these guidelines into use throughout the Department of Defense has been ongoing since that time. The need for updates to the TCCC guidelines was recognized early on and has been carried out by the Committee on Tactical Combat Casualty Care established and operated by the Naval Operational Medicine Institute. The evolution of these guidelines from the 1996 recommendations to the present is described. Numerous reports in the medical literature and collected from combat first responders have documented that TCCC is saving lives on the battlefield and improving the tactical flow of missions on which casualties have occurred. Present challenges to the optimized implementation of TCCC in U.S. combat units include the need to expedite transition of new TCCC techniques and technologies to deploying units, to provide TCCC training for all U.S. combatants, and to ensure adequate funding for the Committee on TCCC.

A cohort of 1,056 normotensive, healthy, young men initially examined in 1940 at the mean age of 24 years was followed at three periodic intervals through 1964. The cohort demonstrated little rise in mean systolic blood pressure beyond age 35; a portion of this cohort showed no change of systolic blood pressure with age. If the men are classified by quintile according to systolic blood pressure in 1940, those men in the upper quintile tend to remain high; when classified by quintile in 1951, those men at the extremes maintained their relative position through 1964. Predictive utility of a systolic blood pressure may be a function of its actual level as well as the age of the individual. Two factors further influenced the systolic blood pressure of this cohort, namely, parental longevity and gain in weight. The significant effect of parental longevity became less important relative to gain in weight as time progressed and after 1940 affected primarily those men who had gained weight.

CONTEXT: With numerous US military personnel currently deployed throughout the world, military and civilian health care professionals may encounter imported malaria from this population. OBJECTIVE: To identify malaria in US Army personnel deployed to a combat zone. DESIGN, SETTING, AND PATIENTS: Case series in the US Army health care system. A total of 38 cases of malaria were identified in a 725-man Ranger Task Force that deployed to eastern Afghanistan between June and September 2002. MAIN OUTCOME MEASURES: Identification of malaria cases and soldiers' self-report of compliance with antimalarial measures. RESULTS: A total of 38 patients were infected with Plasmodium vivax, yielding an attack rate of 52.4 cases per 1000 soldiers. Diagnosis was confirmed a median of 233 days (range, 1-339 days) after return from the malaria endemic region, with additional laboratory findings noting anemia and thrombocytopenia. One case was complicated with acute respiratory distress syndrome during the patient's primary attack and a spontaneous pneumothorax during relapse. This case accounted for 1 of 2 relapse cases in the study population. From an anonymous postdeployment survey of 72% (521/725) of the task force, the self-reported compliance rate was 52% for weekly chemoprophylaxis, 41% for terminal (postdeployment) chemoprophylaxis, 31% for both weekly and terminal chemoprophylaxis, 82% for treating uniforms with permethrin, and 29% for application of insect repellent. CONCLUSIONS: Delayed clinical presentation can occur with P vivax. Symptoms are often vague, but malaria should be included in the differential diagnosis for soldiers returning from an endemic region. Suboptimal compliance with preventive measures can result in a malaria outbreak.

Ten labyrinthine defective (L-D) and twenty normal subjects were exposed to extremely severe weather conditions during a sea voyage. The effects of such a stress were complicated by a feeling of fear in all of the normal and in some of the L-D subjects. None of the latter manifested typical symptoms of motion sickness whereas all of the normal subjects did. The fact that the L-D subjects did not become sick suggests that, even in instances where motion sickness symptoms appear to be triggered by anxiety, the vestibular organs play an essential etiological role.

Eight men completed an experiment in which they were rotated about an Earth-horizontal axis at velocities of 10 and 30 rpm. Both nystagmus and subjective estimates of body position in space were modified by the higher rate of rotation. Subjects who gave essentially veridical estimates of body position at 10 rpm became disoriented at 30 rpm and gave responses closely resembling those of subjects with labyrinthine dysfunction. Subjects who produced sustained unidirectional horizontal nystagmus during constant velocity rotation at 10 rpm produced a reversing horizontal nystagmus during comparable intervals of rotation at 30 rpm. Nystagmus slow phase velocity for both 10 and 30 rpm exhibited a cyclic modulation which was related to orientation relative to gravity. As in previous studies, sickness was produced by rotation about a horizontal axis, and a relationship between mental task and incidence of sickness was again noted.

AbstractA new multi-dimensional quantitative ataxia test battery employing the "rail method" of testing was developed to assess more precisely than heretofore postural equilibrium-disequilibrium under unusual conditions and stresses such as rotating environments. Validity of the standardized test procedures in the laboratory, in the field, and in clinical situations was demonstrated, and present and future uses of the Test Battery in normals and auricular-involved individuals in vestibular research as well as in related research-clinical areas -were outlined.

<div class="htmlview paragraph">An acceleration sled carrying living human subjects was used to measure the dynamic response of the head and neck to —G <sub>x</sub> impact acceleration. Seated volunteers with complete pelvic and upper torso restraint were subjected to increasing impact accelerations beginning at 2.7 g and increasing in 1 g increments. The volunteers were selected to encompass the 5th to 95th percentile distribution of sitting height according to a selected reference.</div> <div class="htmlview paragraph">Precision inertial transducers were used to determine the linear and angular acceleration of the head and the first thoracic vertebra. The inertial system consisted of a biaxial accelerometer and rate gyroscope on a bite-plate, a biaxial acceierometer over the bregma, and a biaxial acceierometer and rate gyroscope over the spinous process of the first thoracic vertebra. The transducers on the bite-plate and over the bregma were rigidly connected to one another.</div> <div class="htmlview paragraph">Precision high-speed cameras were mounted on the sled to determine the displacements of the head and neck of the subject. One camera was mounted posteriorly and one mounted laterally with respect to the subject.</div> <div class="htmlview paragraph">Data handling was effected by recording the transducer outputs on analog tape, converting the analog tape to digital form, and calculating the pertinent trajectories by digital computer. The distance of test markings from a point of reference was measured from each photographic exposure and committed to punch cards in digital form. The inertial and photographic systems were completely redundant. The time reference axes of both systems were interlocked. The results obtained from both systems were compared for validation.</div> <div class="htmlview paragraph">Preliminary results are presented.</div>

The effectiveness of a drug in reducing susceptibility to acute motion sickness is readily determined in a slow rotation room (SRR) where the stressful Coriolis accelerations are under quantitative control and the experimenter and subject can collaborate under laboratory conditions. Fifty subjects were used, each serving as his own control, in evaluating 16 representative antimotion sickness drugs. Only the drugs with a sympathomimetic or parasympatholytic action and some of the antihistamines were notably effective. The summation effect of dextroamphetamine sulfate and 1-scopolamine hydrobromide provided far better protection than any single drug. Other classes of drugs had either a slightly favorable or slightly unfavorable action. (Author)

Spice, an herbal mixture containing synthetic cannabinoids, is a legal drug increasingly abused by adolescents and young adults for its narcotic-like effects. A paucity of English language literature exists on the clinical effects of Spice use. A case report of substance-induced psychosis and a summary of available literature follows later.

A large outbreak of acute gastroenteritis occurred over a 5-week period aboard an aircraft carrier. The estimated cumulative attack rate was 13% among the 4,500-man crew. Eight percent of the crew sought medical attention, nearly all of whom missed 1 day or more of work. The risk of developing illness was 2 to 3 times greater for individuals living in more crowded sleeping quarters (> 50 persons per compartment). Occurrence of gastroenteritis was associated with a fourfold or more rise in Norwalk virus antibody levels, as measured by an enzyme-linked immunoassay utilizing a baculovirus expressed recombinant antigen. In addition, 27 nm Norwalk virus-like particles were visualized in two of six stools examined by immune electron microscopy. The presence of a low (< 1:50) or a high (> or = 1:6,400) pre-illness antibody level was associated with a lower incidence of illness. This investigation indicates that Norwalk virus can adversely impact operations of a military vessel and that crowding is a major risk factor in transmission.

Hyperbaric oxygen therapy (HBOT) is a primary or adjunctive therapy for a variety of medical disorders including some involving the eye. This paper is the first comprehensive review of HBOT for ocular indications. The authors recommend the following as ocular indications for HBOT: decompression sickness or arterial gas embolism with visual signs or symptoms, central retinal artery occlusion, ocular and periocular gas gangrene, cerebro-rhino-orbital mucormycosis, periocular necrotizing fasciitis, carbon monoxide poisoning with visual sequelae, radiation optic neuropathy, radiation or mitomycin C-induced scleral necrosis, and periorbital reconstructive surgery. Other ocular disorders that may benefit from HBOT include selected cases of ischemic optic neuropathy, ischemic central retinal vein occlusion, branch retinal artery occlusion with central vision loss, ischemic branch retinal vein occlusion, cystoid macular edema associated with retinal venous occlusion, post-surgical inflammation, or intrinsic inflammatory disorders, periocular brown recluse spider envenomation, ocular quinine toxicity, Purtscher's retinopathy, radiation retinopathy, anterior segment ischemia, retinal detachment in sickle cell disease, refractory actinomycotiC lacrimal canaliculitis, pyoderma gangrenosum of the orbit and refractory pseudomonas keratitis. Visual function should be monitored as clinically indicated before, during, and after therapy when HBOT is undertaken to treat vision loss. Visual acuity alone is not an adequate measure of visual function to monitor the efficacy of HBOT in this setting. Ocular examinations should also include automated perimetry to evaluate the central 30 degrees of visual field at appropriate intervals. Interpretation of the literature on the efficacy of HBOT in treating ocular disorders is complicated by several factors: frequent failure to include visual field examination as an outcome measure, failure to adequately address the interval from symptom onset to initiation of HBOT, and lack of evidence for optimal treatment regimens for essentially all ocular indications. Because some ocular disorders require rapid administration of HBOT to restore vision, patients with acute vision loss should be considered emergent when they present. Visual acuity should be checked immediately, including vision with pinhole correction. If the patient meets the criteria for emergent HBOT outlined in the paper, normobaric oxygen should be started at the highest inspired oxygen fraction possible until arrangements can be made for HBOT.

INTRODUCTION: Aviation mishaps caused by maintenance factors vary in severity, but can cost untold sums in lives and equipment lost. This study proposes to demonstrate that certain specific maintenance-related human factors are significantly correlated with both mishap frequency and severity. METHODS: Using information from the Maintenance Error Information Management System (MEIMS), 1,016 aircraft mishaps caused by human factors in maintenance were examined. These mishaps were previously categorized using the Human Factors Analysis and Classification System-Maintenance Extension (HFACS-ME). Frequency analysis was used to determine the most common HFACS-ME factors seen in aircraft mishaps. Logistic regression techniques were used to describe the relationship between the dichotomized outcome of mishap severity and the human factors found in the HFACS-ME. RESULTS: Inadequate supervision, attention/memory errors, and judgment/decision errors were the factors found most often in aircraft mishaps. The factors of inadequate design, inadequate adaptability/flexibility, inadequate lighting/light, confining workspace, and attention/memory error increased odds of being associated with a higher severity mishap. DISCUSSION: Emphasis in training and education placed in the first three factors mentioned may reduce overall number of mishaps. Concentrating resources on the final five factors may decrease the number of severe mishaps.

Abstract : A group of twelve persons selected only on the basis of their visual defects were exposed to stressful Coriolis accelerations under standardized conditions. All demonstrated differences in susceptibility to acute motion sickness that bore no relation to their rank order of visual deprivation. Insofar as comparison with a group of normal subjects was made possible, no significant differences in susceptibility were demonstrable. It was concluded that vision is not an essential but rather a secondary etiologic factor in the genesis of motion sickness. This is not incompatible with the fact that symptoms characteristic of motion sickness may be visually induced in the absence of 'motion.' (Author)

When a man is accelerated on a centrifuge, the direction of gravitoinertial vertical changes relative to his body. However, a lag occurs in his perception of this change. The hypothesis has been advanced that the perceptual lag in this situation is partly the result of a conflict between signals arising from the semicircular canals and from the otolith organs. To test this hypothesis, subjects were tilted in such a way that they received consistent semicircular canal and otolith signals. This was accomplished simply by tilting them 30 deg from upright in their frontal plane. Immediately after being tilted, these subjects made estimates of the vertical which were approximately accurate, and they continued to make accurate estimates throughout a 140 sec judgment period. The absence of a perceptual lag under these circumstances supports the hypothesis.

&lt;div class="htmlview paragraph"&gt;A methodical investigation and measurement of human dynamic response to impact acceleration is being conducted as a Joint Army-Navy-Wayne State University investigation. Details of the experimental design were presented at the Twelfth Stapp Car Crash Conference in October 1968.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;Linear accelerations are being measured on the top of the head, at the mouth, and at the base of the neck. Angular velocity is also being measured at the base of the neck and at the mouth. A redundant photographic system is being used for validation. All data are collected in computer compatible format and data processing is by digital computer. Selected data in a stage of interim analysis on 18 representative human runs of the 236 human runs completed to date are presented.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;Review of the data indicates that peak accelerations measured at the mouth are higher than previous estimates. The time relationship of the peak resultant mouth accelerations to the peak sled acceleration for this particular accelerator and restraint system is described. The maximum peak resultant mouth acceleration was 47.8 g and the peak mouth angular velocity on another run exceeded 30 rad/sec, on nominal 10 g, 250 g/sec runs. Clinical evaluation of the subjects before and after the runs disclosed no evidence of unconsciousness or neurological deficit attributable to the acceleration.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;Representative plots of the human dynamic response are presented, discussed, and compared. A first-order linear regression analysis for the peak mouth resultant acceleration and the peak mouth angular velocity obtainable from the peak sled acceleration is presented.&lt;/div&gt;

A slow rotation room in a laboratory environment provides an excellent instrument for the study of motion sickness because the experimenter can control not only the stressful Coriolis accelerations, but also other important procedural and environmental variables.By exploiting this control, combined with the judicious selection of experimental subiects, i t was possible to confirm many previous findings and demonstrate that manifestations of disturbances i n the vestibular system fa1 I into two distinct categories.In the first category are reflex phenomena evoked by Coriolis accelerations when the head i s rotated out of the plane of the room's rotation, and revealed through systems which, under natural stimulus conditions, have functional articulations with vestibular receiving areas.Included here are a characteristic sensation of tumbling or rotation, the Coriolis oculogyral illusion, nystagmus, dizziness, and neuromuscular incoordination.The symptomatology i n the second category comprises an epiphenomenon superimposed on any manifestation of the first, when the unusual vestibular activity, presumably through facilitory-inhibitory processes, irradiates to cells or cel I assemblies not normally stimulated.These epiphenomena1 responses are absurd i n terms o f the needs of the organism, and there i s no evidence that their homeostatic mechanisms make any contribution toward restoring a homeostatic state in the vestibular system.The sites o f origin of these responses are not vestibular receiving areas under normal circumstances, and the Iinkage with the vestibular system must be facultative.The relations between manifestations i n the two categories suggest that the initial linkage, with certain sites a t least, may be neuronal, but that chemical stimuli must be implicated to account for 1) long latencies between stimulus and response, and 2) the long perseveration of the manifestations after the stressful accelerations have ceased.Selected experimental findings are used i n defining the characteristics of manifestations i n the two categories and i n demonstrating the nature of the facultative linkage between the otherwise independent systems underlying manifestations i n the two categories.It w i l l be shown that the experimenter, by manipulating mainly vestibular homeostatic mechanisms, can prevent the appearance of manifestations in the second category, control their severity when evoked, and lose control only when these symptoms are relatively severe or perseverate long after the stressful accelerations have ceased.Practical and theoretical implications are discussed, including the concept of "functional vestibular reserve."

The separate and combined influences of otolith and nonotolith sensory inputs upon perception of the oculogravic illusion were investigated by manipulating the visual and gravitoinertial force environments. By comparing the visually perceived direction of space by four naval aviators and four deaf persons with bilateral labyrinthine defects when dry and when immersed in water up to neck level, the contributions of (1) field force receptors in the vestibular organs and (2) nonvestibular proprio-ceptors stimulated by external contact support could be differentiated. Under these various conditions it was found that in normal persons, the vestibular contribution is predictable in terms of the direction of the gravitoinertial force vector but that the nonvestibular contribution varies; it may be relatively great or small. In persons with bilateral labyrinthine defects a nonvestibular contribution was always present but there was great individual variance. The significance of the findings in terms of tests measuring the function of the otolith organs is discussed.

In this paper, we summarize studies that used ANAM tests to assess the effects of environmental stressors. The findings document performance changes resulting from conditions relevant to military operational medicine. These conditions included radiation exposure, toxins, high altitude, undersea conditions, Marine basic training, advanced military training, and fatigue. The results of these studies demonstrate that ANAM detects cognitive changes in extreme environments.

On the earth, or in level flight, a blindfolded subject being rotated at constant velocity about his recumbent long body axis experiences illusory orbital motion of his body in the opposite direction. By contrast, during comparable rotation in the free-fall phase of parabolic flight, no body motion is perceived and all sense of external orientation may be lost; when touch and pressure stimulation is applied to the body surface, a sense of orientation is reestablished immediately. The increased gravitoinertial force period of a parabola produces an exaggeration of the orbital motion experienced in level flight. These observations reveal an important influence of touch, pressure, and kinesthetic information on spatial orientation and provide a basis for understanding many of the postural illusions reported by astronauts in space flight.