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Wireless Core Temperature Measurement during Extreme Environmental Exposure


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): OPERATIONAL MEDICINE OBJECTIVE: Develop a wireless technical solution and data logging system for measuring real-time core temperatures in humans during hot and cold exposure, to include water immersion, for up to 24 hours in resting and exercising individuals. DESCRIPTION: Warfighters are exposed to austere environmental conditions during training and combat. They are at risk of suffering from hyperthermia and hypothermia, as well as peripheral cold injuries. For example, from 2017-2021, there were ~2,500 incidences of heat stroke and 9,700 heat exhaustion casualties across the Armed Forces and 2,466 cold injuries in active and reserve components across all the Services. Medical costs for heat injuries are greater than $6M per year and result in significant lost duty time. Methodologies are needed to measure core temperature during training in real-time so that the risk of an environmental injury is reduced. Identification of real-time temperatures could prevent these injuries. This technology needs to be robust so that specific individuals can be identified. There have been technologies developed in the past, but the companies are no longer manufacturing these products. Although a robust and accurate core body real-time wireless thermometer system is the focus of this effort; solutions that offer the ability to measure additional sites/locations of temperature concurrently, inherently provide additional context and thus can lead to better assessments of environmental injury. Currently this capability does not exist in a commercial form, and hampers the ability of leadership to monitor their personnel. Furthermore, this technology is also very important for DOD researchers to collect this critical temperature information so that improved health-state algorithms can be developed that prevent injuries due to environmental stressors. There are technologies currently on the market to measure core body temperature, but they are unable to wirelessly measure core temperature and produce real-time continuously-updating temperature data during water immersion. No product exists that can measure temperatures to reduce the possibility of freezing cold injuries in extreme cold conditions. The envisioned system would employ technology using an innovative engineering approach that enables core body and other temperature locations to be measured, collected, and visualized in real-time with the data also logged to allow easy post-measurement evaluation and download. Accuracy of measurement will be a trade-off between this and simplicity of implementation. In the civilian community, this product can be used by firefighters, homeland security personnel (hazardous material cleanup), researchers in the exercise physiology community, and athletes. Military users for this product include all Warfighters exposed to extreme environmental conditions. If fielded, the technology may require secured communication methods. PHASE I: The contractor will use novel/innovative concepts to design and develop a breadboard prototype to measure core body and any additional sites during environmental exposure during hot- and cold-weather operations, to include water immersion. Innovative technological designs are required as the specifications for this include high precision measurements, ability to operate in extreme and varied environments, such as the Arctic, desert, jungle, and underwater, need to be comfortable and transparent to the Warfighter so as not to encumber them, and the requirement for long battery life with infrequent recharging. The technology will be supported by documentation of proof-of-concept and data regarding scientific validity of the proposed solution. PHASE II: The contractor will construct and demonstrate, in laboratory conditions, the operation of a core temperature measurement device/prototype and devices/prototypes that measure temperature at other locations s in real time and records data on a logger for later downloading. Demonstration of the prototypes will require laboratory experiments using human volunteers exposed to hot (> 90 °F air), cold (< 40 °F air), and water immersion (between 50-80 °F) for 2 h. The prototype will also include any hardware/software interfaces that are required for system functionality. At the end of phase II, 20 prototypes suitable for phase III field evaluations will be manufactured. System requirements for Phase 2 include: (1) not interfere with other physiological functions; (2) digitally identify specific individuals; (3) waterproof; (4) transmit temperature signal from underwater environment to data logger (~3 meters); (5) data must be continuously logged to ensure minimal loss of data with sampling frequencies as low as 5 seconds and be time synchronized; and (6) core body temperature must have accuracy of +/- 0.01 °C and precision of +/- 0.02 °C; other temperature locations must have an accuracy and precision of 0.05 °C. PHASE III DUAL USE APPLICATIONS: The prototypes will be extensively tested in field studies to demonstrate a reliable and robust solution for civilian and military application. In the civilian community, this product can be used by firefighters, homeland security personnel (hazardous material cleanup), researchers in the exercise physiology community, and athletes. Military users for this product include all Warfighters exposed to austere environmental conditions (e.g., infantrymen). System requirements for Phase 3 include: (1) light-weight; (2) low-power requirements/long battery life; (3) non-flammable; (4) rugged enough to withstand routine use in military and civilian settings; (5) user friendly technology with the potential to be used in field operations; (6) The system must scale for use. Typically the system will need to be used in the field from a squad size (~10 Warfighters) all the way up to a company size (~100-200 Warfighters). Wireless technologies must be designed and managed to accommodate large numbers of personnel within a confined space. Additionally testing environments may not allow for research staff to be in close proximity (less than 3 meters) to volunteers; wireless technology must be scalable to accommodate long range communications without interfering with other military communication systems; and (7) Must meet MIL-STD-810G standard ( It will be used to measure, in real-time, core temperatures, as well as log data for up to 24 hours. The device should seek to generate data that could be submitted to the FDA for 510K equivalency for a temperature measurement system. The end-state of the Phase III effort will be a product suitable for use by civilian communities that have elevated risks of heat/cold injuries to include first responders and athletes. For the military community, this technology could be inserted into the Physiological Status Monitoring/Health Readiness and Performance program. REFERENCES: 1. Buller MJ, Davey T, Fallowfield JL, Montain SJ, Hoyt RW, Delves SK. (2020). Estimated and measured core temperature responses to high-intensity warm weather military training: implications for exertional heat illness risk assessment. Physiol Meas., 41:065011. doi: 10.1088/1361-6579/ab934b; 2. Buller MJ, Delves SK, Fogarty AL, Veenstra BJ. (2021). On the real-time prevention and monitoring of exertional heat illness in military personnel. J Sci Med Sport. 24:975-981. doi: 10.1016/j.jsams.2021.04.008; 3. Buller MJ, Welles AP, Friedl KE. (2018). Wearable physiological monitoring for human thermal-work strain optimization. J Appl Physiol (1985). 2018 Feb 1;124(2):432-441. doi: 10.1152/japplphysiol.00353.2017; 4. O'Brien C, Hoyt RW, Buller MJ, Castellani JW, Young AJ. (1998) Telemetry pill measurement of core temperature in humans during active heating and cooling. Med Sci Sports Exerc., 30:468-72. doi: 10.1097/00005768-199803000-00020; 5. van Marken Lichtenbelt WD, Daanen HA, Wouters L, Fronczek R, Raymann RJ, Severens NM, Van Someren EJ (2006). Evaluation of wireless determination of skin temperature using iButtons. Physiol. Behav., 88:489-497 KEYWORDS: cardiovascular strain, core body temperature, heat illness, hyperthermia, hypothermia, water immersion
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