Since late 1990s, a new hypoxia training device using mixed gas delivered through trainee’s oxygen mask has been developed in the United States Navy. This “Reduced Oxygen Breathing Device (ROBD)”has been evaluated in many research projects and has been introduced to military aircrews training as an alternative method to traditional hypobaric hypoxia training in several countries. The purpose of this article is to review the ROBD focusing on physiological differences between normobaric and hypobaric condition. The ROBD has been reported to induce almost same physiological responses, symptoms and cognitive impairment as the hypobaric induced hypoxia. Rapid decompression familiarization, which is only produced by hypobaric chamber training, is one of the issues to consider before introducing the ROBD to aircrews training. We also summarized the ROBD training protocols combined with a flight simulator for military aircrews.

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