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Undersea Warfighter Health & Performance

The submarine is one of the most physically and mentally challenging platforms in the U.S. Navy, where submariners work, sleep, eat, and play in the same environment for extended periods. Lack of natural sunlight, disrupted circadian rhythms, challenging watch schedules, limited access to physical exercise, and reduced availability of fresh produce are some of the factors that may affect submariner health and performance during long deployments. NSMRL has initiated multiple efforts to understand how the undersea environment affects Sailor health and performance. These efforts include: the creation of the Unobtrusive Performance Measures Lab to measure human performance in real-time and under various conditions without the interference of intrusive technology, development of a team task simulation bridge to assess real-time team dynamics during virtually created bridge operations, and implementation of studies on the effects of the submarine environment and lifestyle on submariner performance and physiology.

Research Activities
• Understanding microbiome changes in submariners after prolonged submarine deployment and evaluation of those changes in relation to alterations in crew health and performance
• Evaluation of the effects of underwater exercise on cognitive function
• Evaluation of commercial off-the-shelf technologies to test the impact of diving on vestibular reflex function and monitor and predict effects on performance
• Evaluation of personal light treatment devices as a countermeasure for fatigue and circadian misalignment in a submarine environment • Assessment of submariners’ sleep needs during a straight-8s, 24-hour watchbill
• Development of objective and unobtrusive measures of warfighter performance (eyetracking, galvanic skin response, heart rate variability, electroencephalography) to provide real-time indications of Sailors’ degraded performance
• Characterization of caffeine use on submarines

Submarine Atmospheric Monitoring

Submarine atmospheric monitoring research at NSMRL is composed of both the Submarine Atmosphere Health Assessment Program (SAHAP) Program of Record, which provides ongoing atmospheric monitoring support, and independent research on developing new monitoring technologies. During underway periods, submariners are in a closed environment, requiring close monitoring of the atmosphere to ensure that it does not pose a hazard to the crew. While automated systems continuously measure levels of the most critical gases, including O2 and CO2, other possible contaminants, such as oil particulates or organic compounds produced by machinery, must also be monitored on a long-term basis. As one of the Navy’s primary resources to ensure the safety of the submarine atmosphere, SAHAP provides long-term, passive monitoring for defined atmospheric compounds of concern while underway. The program also provides guidance on the effects of evolving technology that could affect the submarine environment, such as the emittance of nanoparticles from 3D printers. Additional NSMRL research related to atmosphere monitoring is focused on exploring the use of personally worn passive dosimeters to determine individual exposures to environmental contaminates in the submarine atmosphere while underway.

Research Activities
• Management of ongoing monitoring of submarine atmospheric constituents
• Provision of expertise in sampling enclosed spaces for long periods of time
• Development of wearable submarine atmosphere contaminant monitors
• Evaluation of Commercial off the Shelf instruments to develop hand-held, real-time monitoring of contaminants expected during a disabled submarine (DISSUB) event
• Development of Passive Personalized Atmospheric Monitors

Bioeffects of Underwater Sound & Blast

Divers are among the most highly trained, highly skilled Navy Sailors, and are critical for the protection, safety, and success of our submarine and surface fleets. While the divers work to protect us, NSMRL’s underwater bioeffects team works to protect them. The team conducts human effects research and provides guidance to the fleet on how underwater sound and blast from sources such as sonar, tools and equipment, and impulse sound affect human divers. Their work on underwater sound detection and localization and hearing in hyperbaric conditions has led to advancements in our understanding of the underwater hearing abilities of humans, with NSMRL researchers being the first to document that humans can detect underwater sounds as high as 190 kHz. NSMRL translates research findings into evidence-based guidance for diver exposure to underwater sound and blast. Research focuses include: physiological mechanisms for underwater sound perception, diver protection from underwater sound and blast, the use and effectiveness of underwater sound in nonlethal diver deterrence systems, creation of physical and computational models of physiological response to underwater sound, and development of tools and guidance for underwater hearing conservation.

Research Activities
• Provision of updated and expanded tables for underwater explosive safe standoff distances in the EOD 60-series publication, used across the U.S. and allied international armed forces
• Development of an interactive software application to provide recommendations for human exposure limits to underwater noise
• Development of methodology to standardize the measurement of underwater acoustic signals emitted by new technologies
• Measurement of sound transmission properties of the KM-37 diving helmet to allow evaluation of noise exposure to helmeted working divers
• Development of surrogate models for studying the effects of underwater blasts, including an artificial human torso
• Development of an ingestible pill to measure internal response to blast exposure

Submariner Psychological Fitness

Submariners face significant stressors that are unique among the military community. The confined space and isolation of the submarine can be mentally and emotionally challenging, and yet mission success depends on optimal psychological readiness of Sailors. NSMRL’s psychological screening and fitness program is dedicated to improving the psychological suitability of prospective submariners, predicting and reducing the number of unplanned losses (unexpected separation from service) from operational units, and exploring and enhancing individual and team resilience. NSMRL has an ongoing effort to maintain, administer, and score the psychological screening assessment for prospective submariners. This assessment process, known as SUBSCREEN, seeks to identify Sailors with psychological and/or motivational factors incompatible with submarine duty. NSMRL is also conducting studies to define the ideal psychological profile for successful service in submarines and other nuclear-powered Navy platforms and strives to support the psychological fitness of submariners by providing mental health support tools for use while underway.

Research Activities
• Modernization of SUBSCREEN by developing and testing an updated submariner psychological screening tool
• Evaluation of psychological factors that can predict the success of officers and enlisted service members enrolled at the Naval Nuclear Power Training Command (NNPTC)
• Identification of predictors of psychological resilience and development of a predictive model of psychological resilience indicators in submariners
• Objective assessments of anxiety-related risks and vulnerabilities in submariners
• Development of VirGIL (Virtual Reality Guide In Life): a psychology self-help software program that provides confidential cognitive behavior therapy content to deployed submariners

Human Systems Integration

With the emergence of new submarine technologies, Sailors are increasingly required to process complex information, make advanced decisions, and operate complicated equipment. Human Systems Integration (HSI) is a process NSMRL researchers use to provide tools to present information in an accessible manner, assist in decision making, and facilitate usability of hardware and software technologies. HSI combines our knowledge of human capabilities and limitations with systems development to make them more effective, efficient, and safe. By combining theory with an iterative feedback process with the line community, NSMRL applies an HSI approach to develop and improve submarine systems, enhance submariner performance, and increase readiness. The program also seeks to predict and mitigate degradation in performance through noninvasive monitoring of a variety of novel physiological measures.

Research Activities
• Prediction of degradation in performance with cognitive and machine learning models based on monitoring changes in physiological measures such as face and eye tracking, heart rate, and skin conduction
• Development of a computational model that mimics how humans process audio and visual cues • Support of the creation of a software tool that provides individualized fatigue-based schedule management of submariners for optimized watchstanding schedules
• Development of a software training and knowledge transfer platform that, based on individualized learning styles, can be used to design custom performance support that optimizes (or enhances) learning for complex submarine-based tasks
• Establishment of a submarine command and control simulation lab to evaluate team performance and identify individual tasks that are most susceptible to fatigue
• Evaluation of the effectiveness of transcranial direct current stimulation on reducing the effects of time-on-task fatigue
• Tracking cognitive performance decrements in cold environments

Diving & Hyperbaric Research

NSMRL’s diving and hyperbaric research program focuses on evidence based solutions that promote the health and enhance the performance of the undersea warfighter. At the centerpiece of NSMRL’s diving and hyperbaric research program is the one-of-a kind Genesis Hypo/Hyperbaric chamber complex. NSMRL’s diving mission is supported by a full Navy dive locker with SCUBA and Surface Supply capabilities, an indoor immersion test pool, and a command dive boat for open water diving operations. NSMRL’s diving research program has advanced the field’s understanding of saturation diving, nitrogen narcosis, CO2 toxicity, pulmonary O2 toxicity, decompression stress, NO physiology under ambient pressure extremes, temperature regulation, and disabled submarine escape and survival. In addition, it has provided knowledge about the environmental stress diving can have on warfighter health, cognition, and performance. A complete renovation of the chamber was initiated in 2019, with expected completion in 2022. As a result of the overhaul, NSMRL will have a fully-functional, state-of-the-art chamber facility to advance diving and hyper/hypobaric medicine research.

Research Activities
• Evaluation of the sensitivity and reliability of exhaled NO as a non-invasive biomarker of pulmonary hyperoxic stress and pulmonary O2 toxicity
• Investigation of undersea warfighter O2 oxygen toxicity (genetic changes): identification of genetic markers and metabolic pathways that are altered by exposure to hyperbaric oxygen

Submarine Survival, Escape & Rescue

In the rare event that a submarine becomes disabled and is unable to return to the surface (DISSUB), the crew must decide whether to remain onboard and await rescue or escape from the vessel. This decision rests on a complex set of factors including condition of the crew, the status of the submarine atmosphere, depth, and proximity of rescue assets. NSMRL maintains military and civilian expertise in submarine survival, escape, and rescue to provide NAVSEA 00C and SUBFOR fleet advice in case of a DISSUB incident. Areas of research focus include: DISSUB survival (e.g., survival times and survival equipment evaluation), DISSUB escape (e.g. saturation decompression drop out modeling, escape suit testing, medical hazards of escape), rescue procedures and equipment testing (e.g. test and evaluation of closed circuit O2 rebreathers for accelerated decompression of DISSUB survivors), and science-based recommendations to modify the GUARD Book, the manual that gives guidance to survivors of a submarine casualty.

Research Activities
• Optimization of rescue and triage of crewmembers during a DISSUB event
• Creation of medical response strategies to optimize DISSUB escapee survival
• Provision of recommendations for modifying the Guard Book to facilitate the ability of survivors to determine escape times while under stress
• Development of the eGuard book, an electronic version of the Guard Book for use during a DISSUB scenario
• Exploration of the effects of DISSUB stressors on submariner cognition
• Development of the Submarine Rescue software application that provides decompression protocols for rescuees and rescue personnel from a disabled submarine
• Critical review of casualties from historical DISSUB incidents

Hearing Conservation

Noise-induced hearing loss is one of the most prevalent occupational health hazards in the military. To help protect our service members’ hearing, NSMRL’s Regional Hearing Conservation (RHC) Program of Record (POR) provides subject matter expertise on hearing conservation, psychoacoustics, audiology, and hearing protection to the Navy and Marine Corps line communities. The program also provides support to Navy audiologists, otolaryngologists, allied health professionals, audiometric technicians, and consultants across the DoD and Defense Health Agency. NSMRL houses an expansive state of the art audiology test suite that includes one of the largest anechoic chambers in the DoD, a large reverberant room, a Real-ear Attenuation at Threshold (REAT) facility, and multiple audiology test booths. RHC POR efforts include basic to applied research. The team’s principal investigator is a member on multiple American National Standards Institute (ANSI) working groups related to speech-in-noise understanding and assessing the effects of head-worn devices on human auditory localization ability.

Research Activities
• Testing and evaluation of head-worn hearing protection devices (HPDs) for their impact on hazardous noise exposure, communication, sound localization, and attenuation of impulse (blast) noise
• Execution of large-scale shore and afloat hearing conservation field studies
• Evaluation of HPDs to determine the most effective and most appropriate forms for Sailors and Marines at accession and in positions routinely exposed to hazardous noise
• Testing and evaluation of field attenuation estimation systems’ performance for enterprise-wide DoD use

Undersea Health Research Program

This unique program maintains an epidemiologic database that cross-references a number of Navy data sources and aids in characterizing the health effects of the submarine and diving environment. With the ability to provide rapid analysis, the program can serve as a reference source for operational planning and risk mitigation. As part of this program, NSMRL initiated the first-ever epidemiological study to evaluate the medical impacts of the submarine environment on Sailors. The program recently expanded its research to include divers to assess the impact of the undersea environment on diver health. UHERP’s main objectives are: to identify any environmental or occupational exposure risk that correlate with negative health outcomes, premature separation from military service, medical evacuations, and to improve the health and warfighting capability of the undersea warfare community by harnessing information from “big-data” platforms.

Research Activities
• Development of a centralized database linking medical and personnel data for Navy divers and submariners
• Summarization of the “who,” “when,” and “why,” for submarine medical evacuations
• Assessment of mental health risk factors for unplanned losses
• Identification of risk factors for hearing loss and tinnitus in the submarine community, two of the most burdensome health conditions for the DoD and VA

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