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Electrodermal Activity for Prediction and Detection of Symptoms Related to the Central Nervous System Oxygen Toxicity Including Seizures


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Military Operational Medicine OBJECTIVE: Develop a means to detect the onset of seizures due to CNS-OT for real-time monitoring of divers immersed underwater. DESCRIPTION: Divers breathing hyperbaric oxygen (HBO2) are at risk for developing Central Nervous System Oxygen Toxicity (CNS-OT), which can manifest as symptoms that might impair a diver’s performance, such as headache, nausea, tinnitus, lip twitching, tingling of the limbs, or even more serious symptoms such as seizure or altered consciousness(1,2). Oxygen seizures themselves are not harmful, the environmental conditions greatly influence the risks associated with losing consciousness or convulsing; being underwater could result in the dislodgement of the diver’s air supply from his or her mouth, possibly leading to drowning(3,4). Furthermore, the risk of CNS-OT dictates strict diving protocols greatly limiting mission capabilities (depth and duration of a dive are impacted by risk of CNS-OT). Developing a means to detect the onset of seizures due to CNS-OT would provide great safety monitoring that has been absent from risk of CNS-OT in diving. If proven, mitigation strategies to prevent CNS-OT and detection of the consequential seizures in some subjects could reduce risk to divers. The risk of CNS-OT occurrence is highly variable between individuals, making it hard to predict the onset of seizures, and to determine the safety of exposure to HBO2. Being able to establish an individual safe level of exposure would maximize the therapeutic and operational uses of HBO2 in hyperbaric, diving, and submarine medicine (e.g. healing problematic wounds or preventing DCS), by enabling the extension of exposure time in individuals with more neurological tolerance to HBO2. Previous studies have suggested that electrodermal activity (EDA) can be used to predict seizures in rodents exposed to HBO2(5). PHASE I: Demonstrate feasibility through analysis and limited laboratory demonstrations, a device that is capable of measuring electrodermal activity (EDA) to be worn by: pool swimmers/divers, surface supplied divers, free swimming divers, and patients receiving hyperbaric oxygen treatment in dry chambers. The device shall provide full function and data processing while immersed in salt water and exposed to increased hyperbaric pressures of 100 feet of sea water (FSW) (threshold)/300 FSW (objective) at a temperature range of 32-95 Degrees F, Provide cost-effective designs and reliability estimates, including lifetime expectancy and lifetime cost estimate. The required Phase I deliverables will include: 1) a research plan for the engineering design of the physiologic monitor; 2) a preliminary prototype, either physical or virtual, capable of demonstrating effectiveness of the proof-of-concept design; and 3) a test and evaluation plan to validate accuracy of data collection including identification of proper controls. Important considerations should include location, minimization of motion artifacts, enhanced comfort and wearability (minimization of wired elements), and on-board processing. Device should detect EDA while submerged underwater. Phase I will provide key information about the uses and limitations of the system and could include rapid prototyping and/or modeling and simulation. PHASE II: Develop, demonstrate, and validate the underwater EDA prototype based on the Phase I design concept. The system should be used under the expected extreme environmental conditions (as cited in the description section) to collect and analyze data and test algorithms against the known physiological alterations during diving activity. Device shall collect data continuously for up to 24 hours at minimum with on-board processing capability to enable feedback to individual. Initial prototype may be designed for use on the body of a diver with or without a wetsuit or drysuit using traditional scuba or rebreather life support. Device should include onboard data processing enabling real-time feedback to diver. No data transmission will be included under the initial development. A lithium battery may be used but alternative power sources that have minimal safety hazards and can function submerged in ocean water should be considered. Initial design may be intended for experimental or training use and need not be adapted for operational use. Phase II deliverable of, at minimum, two prototype units that includes detailed design specifications and technical data package drawings (level 2/3) established through this STTR to ONR that ensures IP protection. Interest by military customer would be defined by validation through testing and confidence in predictive measures. Successful devices would need to be tested either at a Naval dive unit such as Naval Experimental Diving Unit (NEDU) if possible or another acceptable dive facility, which could include commercial dive centers. If NEDU is preferred, it is advisable to plan well in advance to ensure they are able to accommodate testing schedule. PHASE III DUAL USE APPLICATIONS: If successful, transition prototype to a functional unit to the US Navy’s Naval Sea Systems Command Supervisor of Salvage and Diving (NAVSEA SUPSALV), which maintains diving equipment authorized for Naval use. Operationally relevant conditions will necessitate additional testing and may require greater depths, prolonged data collection, and security considerations. If successful, the small business shall support the Navy in transitioning the resulting technology for use in operational environments. The small business shall develop a plan to transition and commercialize the technology and its associated guidelines and principles. Private Sector Commercial Potential: This SBIR would provide much needed understanding of objective measures for detecting early signs of neurologic distress and generally monitoring brain health across recreational and commercial diving populations during mixed gas dives for use in hyperbaric treatments by medical professionals. REFERENCES: 9. R. Arieli, T. Shochat, and Y. Adir, "CNS Toxicity in Closed-Circuit Oxygen Diving: Symptoms Reported from 2527 Dives," Aviation, Space, and Environmental Medicine, vol. 77, no. 5, pp. 526-532, 2006/05/01/ 2006. 10. K. Donald, Oxygen and the diver. Images, 1992. 11. J. M. Clark and T. S. Neuman, "Physiology and Medicine of Hyperbaric Oxygen Therapy," 2008 2008. 12. M. J. Natoli and R. D. Vann, "Factors Affecting CNS Oxygen Toxicity in Humans," DUKE UNIV MEDICAL CENTER DURHAM NC FG HALL LAB FOR ENVIRONMENTAL RESEARCH1996 1996, Available: 13. Posada-Quintero HF, Landon CS, Stavitzski NM, Dean JB, Chon KH. Seizures Caused by Exposure to Hyperbaric Oxygen in Rats Can Be Predicted by Early Changes in Electrodermal Activity. Front Physiol. 2022 Jan 5;12:767386. doi: 10.3389/fphys.2021.767386. PMID: 35069238; PMCID: PMC8767060. KEYWORDS: Electrodermal Activity, waterproof, oxygen toxicity, diving medicine, hyperbaric medicine
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