Recommending an Approach for NASA Toward Neurologic Decompression Illness

INTRODUCTION: Decompression illness, including decompression sickness and arterial gas embolism, may occur during extravehicular activity, with neurologic cases traditionally considered to pose a high risk of permanent disability or death. While developing lunar extravehicular activity denitrogenation protocols with human trials, National Aeronautics and Space Administration physicians uncovered subtle neurologic deficits in two test subjects. These findings challenged the conventional paradigm that neurologic decompression sickness is always serious and raised the question of whether mild cases could be accepted in the context of lunar extravehicular activity operations. METHODS: The literature was reviewed to characterize mild neurologic decompression illness in terms of epidemiology and clinical course in the absence of hyperbaric oxygen treatment. RESULTS: While a significant proportion of mild neurologic decompression illness cases may resolve without hyperbaric oxygen treatment, progression to severe status commonly occurs even in cases with initially mild manifestations. Furthermore, ground-level oxygen treatment has not always proven adequate to resolve deficits of neurologic decompression illness. DISCUSSION: Though mild neurologic decompression illness may resolve without hyperbaric oxygen treatment at higher rates than more severe forms, the rate of progression to functional impairment remains too high to accept in the setting of lunar exploration missions. Without a robust predictive model for deterioration, all neurologic decompression illness should receive prompt hyperbaric oxygen treatment regardless of initial presentation severity. The National Aeronautics and Space Administration should remain vigilant in their approach to neurologic decompression illness and strategize how to reduce the risk and impacts of even initially mild cases.