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Mixed Gas Hypoxia Training in Low Pressure Chambers
Navy SBIR 2008.2 - Topic N08-139 NAVAIR - Mrs. Janet McGovern - [email protected] Opens: May 19, 2008 - Closes: June 18, 2008 N08-139 TITLE: Mixed Gas Hypoxia Training in Low Pressure Chambers TECHNOLOGY AREAS: Air Platform, Biomedical, Human Systems ACQUISITION PROGRAM: PMA 205: Aviation Survival Training, Aviation Physiology, Aviation Safety OBJECTIVE: Improve the Safety and Effectiveness of Hypoxia Training in Low Pressure Chambers by Incorporating Mixed Gas DESCRIPTION: Currently, the U. S. Navy uses low pressure chambers for hypoxia recognition and recovery training. The training consists of exposure to hypobaric environments at or above 20,000 feet. Nearly 10,000 students receive hypobaric training in the U.S. Navy annually. The risk of decompression sickness (DCS) increases substantially at altitudes above 18,000 feet. Because of the risk of DCS, inside observers receive hazardous duty incentive pay ($150.00 per month X 80 inside observers = $12000.00 per month). The incidence of decompression illness resulting from hypobaric chamber training has been reported by a number of military training organizations. A review of 10 of these reports reveals a range of incidence in various populations from 0.3 to 2.9 cases per 1000 exposures, with a mean incidence of 1 case per 1000 exposures (or 0.1%). The Navy has on average 4 cases of DCS annually in its hypobaric chambers with an associated cost of several thousand dollars per treatment, with the possibility of long term medical complications for the patient. The U.S. Navy has recently reported the success of using mixed gas (normobaric hypoxia) for the hypoxia recognition and recovery training for tactical jet aviators using the Reduced Oxygen Breathing Device (ROBD). One advantage of using mixed gas is that the risk of decompression sickness is eliminated. ROBD training uses a mask delivered gas mixture to individual aviators. The Navy has identified this as a shortcoming for the training of aircrews that fly multi crew aircraft because the hypoxia scenario most likely experienced by multi crew aircraft aircrew would involve "mask off" hypoxia. Additionally, hypoxia recovery training for multi crew aircraft aircrew involves crew communication and coordination. This is not feasible with ROBD training. As a result, the U. S. Navy continues to use low pressure chamber training for multi crew aircraft aircrew. Additionally, practicing pressure equalization in a hypobaric environment is a required objective of U. S. Navy Indoctrination Aviation Survival Training. A preferred training approach would be a combination of hypobaric and normobaric (mixed gas) hypoxia for multi crew aircraft aircrew training. Hypobaric exposure need not exceed 8-10,000 feet, eliminating the risk of decompression sickness, but allowing the practicing of pressure equalization. The normobaric exposure should allow exposure to up to 35,000 feet of simulated altitude (in combination with 8-10,000 feet of hypobaric exposure). An additional benefit of this approach is that fewer inside observers can be used, freeing up space to reconfigure the inside of the low pressure chamber to increase training realism. The low pressure chambers can be equipped with aircrew task stations to mimic the types of duties that they would normally engage in while flying (i.e., navigation, flying, operating weapons systems) to increase training fidelity. PAST EFFORTS, CHALLENGES, AND RISKS: The Navy has investigated the use of mixed gas for hypoxia training in its altitude chambers in the past. However, at that time, the technology was not available to provide sustainable altitudes in excess of 25K feet. Recently the Navy has instituted mixed gas training at altitudes of 25K feet and above, but the technology being used provides enough mixed gas for one to two students receiving the gas mixture through an oxygen mask. The Australian armed (Newman, DG, 2007) forces are using mask delivered mixed gas in their low pressure chambers. As previously discussed, the use of a mask to deliver mixed gas is not appropriate training for aircrew that do not fly with a mask. The previous technological challenges are being solved with newer technology. Several companies are now able to deliver larger quantities of mixed gas and have even constructed large space, mixed gas rooms that are capable of maintaining altitudes in excess of 25K feet. What remains is to integrate the mixed gas technology with low pressure technology so that hypoxia can be trained with mixed gas and low pressure can be used to train the effects of pressure changes. This integration appears to be within reach of the current technology. PHASE II: Design, develop and demonstrate a prototype mixed gas system that integrates into existing low pressure chambers. PHASE III: Transition the technology to a commercially available retrofit system capable of transforming low pressure chambers into a mixed hypobaric, normobaric training system for use by the U.S. Navy and other military and private interests. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The U. S. military services currently use hypobaric chambers for hypoxia recognition and recovery training. In addition, many foreign services and a multitude of civilian organizations around the world are using hypobaric chambers for hypoxia training and research. This technology has the potential to increase the effectiveness and safety of this type of training and research. REFERENCES: 2. Ohrui N, Takeuchi A, Tong A, et al. Physiological incidents during 39 years of hypobaric chamber training in Japan. Aviat Space Environ Med 2002; 73: 395-398. 3. Rice GM, Vacchiano CA, Moore JL, Anderson DW. Incidence of decompression sickness in hypoxia training with and without 30-min O2 prebreathe. Aviat Space Environ Med 2003; 74: 56-61. 4. Artino Jr AR, Folga RV, Swan BD. Mask-on hypoxia training for tactical jet aviators: evaluation of an alternate instructional paradigm. Aviat Space Environ Med 2006; 77:857-863. 5. Sausen KP, Bower EA, Stiney ME, et al. A closed-loop reduced oxygen breathing device for inducing hypoxia in humans. Aviat Space Environ Med 2003; 74:1190 �7. 6. Vacchiano CA, Vagedes K, Gonzalez D. Comparison of the physiological, cognitive, and subjective effects of sea level and altitude-induced hypoxia [Abstract]. Aviat Space Environ Med 2004; 75(4, Suppl.):B56. 7. Ostrander GB. Hypoxia in the Hornet: what we know, and what we�re doing. Approach Magazine 2005 May-Jun:10�12 8. Ostrander, GB. Physiological episodes and related mishaps: FY 2001�2005. Norfolk, VA: Naval Safety Center, Department of the Navy; 2005 Oct. 9. Cable GG. In-flight hypoxia incidents in military aircraft: causes and implications for training. Aviat Space Environ Med 2003; 74:169 �72. 10. Newman, DG, Pilot Incapacitation: Analysis of Medical Conditions Affecting Pilots Involved in Accidents and Incidents 1 January 1975 to 31 March 2006. ATSB Transport Safety Report Aviation Research and Analysis Report B2006/0170 Australian Government Australian Transport Safety Bureau January 2007. KEYWORDS: hypoxia; safety; aviation physiology; human factors; hypobaric; training
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