Loss of consciousness and seizure during normobaric hypoxia training

Loss of consciousness is a symptom with a broad differential diagnosis. Distinguishing between syncope and seizure in a patient with a history of loss of consciousness can be equally difficult as their presentation can be very similar. We present the case of a naval electronic countermeasures officer who experienced a loss of consciousness while undergoing hypoxia training with the reduced oxygen breathing device (ROBD). During the episode the patient experienced tonic-clonic contractions with subsequent vertebral fractures, resulting in a prolonged grounding period. The patient's work-up focused on ruling out inherent cardiac and neurologic etiologies. After extensive examination and consultation with neurology, the patient was diagnosed with hypoxia-induced seizure, but was not felt to have an underlying seizure disorder. After reviewing his case, the Naval Aerospace Medical Institute felt that this incident represented a physiologic event and not a medical condition inherent to the aviator. It was, therefore, determined that this episode was not considered disqualifying and did not require a waiver for return to duties involving flight. Our discussion details the appropriate work-up for loss of consciousness, examines possible physiologic explanations for this event, and describes aeromedical considerations. The authors include the patient's physiology instructor, one, of the primary witnesses for the event, and the patient's flight surgeon, who was extensively involved in his care.