Abstract
Background
As United States and allied armed forces maintain a presence in high altitude regions such as eastern Afghanistan, a better understanding of the prevention, diagnosis, and treatment of altitude illness has become increasingly important. This preventable form of disease/nonbattle injury presents a significant issue to readiness for warfighter performance in the field.
Objective and Results
At the Marine Corps Mountain Warfare Training Center in Bridgeport, California (operational altitudes: 2061 to 3383 m), 1036 unacclimatized Marines participated in battalion-level mountain warfare exercises in July 2010. Several unexpected, clear-cut cases of severe anxiety were observed at the Battalion Aid Station (BAS), located at 2061 m, over the first 6 days after training proceeded above 2000 m. These cases occurred among otherwise healthy Marines, some having had no prior history of psychiatric illness, and others having had a history of well-controlled panic disorders or combat stress-related psychiatric illness. All patients presented with similar symptoms of mild to moderate tachycardia, tachypnea, and diaphoresis; some presented with extremity numbness and tingling. Acute cardiopulmonary events could not be decisively ruled out by electrocardiogram, chest radiograph, or lab studies (given the equipment limitation of the BAS); however, patients were monitored clinically with vital signs, pulse oximetry, and chest auscultation/palpation. All patients responded clinically to oxygen, rest, and benzodiazepine management; all returned to baseline psychiatric function within the same day.
Conclusions
The near-simultaneous and unexpected onset of 7 cases of acute anxiety, coincident with new arrival at moderate to high altitude, represents a highly unusual incidence, prevalence, and temporal distribution suggestive of hypobaric hypoxemia as the proximal cause. Based upon the authors' extensive combined clinical experience and review of emerging peer-reviewed literature, High Altitude Anxiety is proposed as a diagnostic entity for consideration in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Further research is indicated.