Acute Mountain Sickness Symptoms After Rapid Ascent to 4900 m

Abstract

Introduction: Acute mountain sickness (AMS) is a common condition in individuals ascending rapidly to high altitudes and often presents with headaches, fatigue, and gastrointestinal symptoms. AMS is prevalent above 13,000 ft (4000 m), but some individuals experience it at lower elevations. This pilot study assessed the prevalence and timing of AMS symptoms in unacclimatized individuals exposed to 16,000 ft (4900 m) in a controlled hypobaric environment.

Methods: A total of 10 healthy, unacclimatized men and women were exposed to an altitude of 16,000 ft (4900 m) for 5 h. Physiological parameters, including heart rate (HR), oxygen saturation (Spo2), and respiratory rate (RR), were recorded alongside AMS symptom severity using the 2018 Lake Louise Questionnaire (LLQ) and divided into low, moderate, and high responders based on severity.

Results: All subjects experienced some degree of AMS symptoms, with LLQ scores increasing over time. Two subjects could not complete the full exposure due to moderate and severe symptoms. HR increased (Δ = 7.0 ± 0.6), while Spo2 remained stable but lower than baseline (Δ = 9 ± 4.2). LLQ score increases were strongly correlated with HR, Spo2, and RR. RR remained stable across subjects but varied between AMS severity groups.

Discussion: This pilot study demonstrated that unacclimatized individuals rapidly exposed to 13,000 ft (4900 m) develop AMS symptoms in a controlled environment. The correlation between LLQ scores and physiological changes offers insight into AMS pathophysiology, supporting the need for further research into AMS susceptibility and genetic factors. Murphey JT, Hess HW, Schwob J, Monaco BA, Clemency BM, Hostler D. Acute mountain sickness symptoms after rapid ascent to 4900 m. Aerosp Med Hum Perform. 2025; 96(11):958-963.

Keywords: acute mountain sickness; altitude sickness; hypobaric chamber; hypoxia; symptoms.