Abstract

Background: Increased sympathetic activity is a part of the integrated physiological response to a hypoxic stimulus but it is not clear if it plays a role in the genesis of acute mountain sickness (AMS).

Aims and Objectives: This study was conducted to evaluate the role of the autonomic nervous system in AMS during the initial phase of acute high-altitude exposure.

Materials and Methods: The study was conducted on 42 lowlanders ascended at an altitude of 3500 m by airplane. Autonomic function tests of 20 subjects who suffered from AMS were studied, and the results were compared with 22 healthy individuals. AMS was diagnosed using the Lake Louise score, and autonomic cardiovascular functions were evaluated using non-invasive cardiovascular reflex tests.

Results: At high-altitude, the diastolic blood pressure (DBP) rise in response to sustained handgrip was higher in AMS subjects than the control group. The rise in DBP in cold pressor test was higher in AMS subjects than controls. The valsalva ratio was also significantly higher in AMS patients than controls.

Conclusion: Sympathetic hyperactivity on induction to high altitude is positively associated with the development of AMS.

Key words: High Altitude; Autonomic Nervous System; Acute Mountain Sickness