Incidence and risk factors of acute mountain sickness during ascent to Hoh Xil and the physiological responses before and after acclimatization.

Objectives: Ascending to altitudes >2500 m may lead to acute mountain sickness (AMS).

Methods: The demographics, height, weight, body mass index (BMI), smoking, and alcohol consumption of 104 healthy controls were collected in Chengdu (500 m). Heart rate (HR), saturation of pulse oxygen (SpO2), and AMS-related symptoms were collected in Hoh Xil (4200 m). A headache with Lake Louise score ≥3 was defined as AMS.

Results: The incidence of AMS was 60.58%. AMS group had a lower SpO2 and higher HR than non-AMS group. Alcohol consumption seemed a risk factor for AMS. There was no difference in the BMI, age, height, weight, and smoking between AMS and non-AMS groups. The most common AMS symptom was headache, followed by dyspnea, insomnia, dizziness, lassitude, and anorexia. Women were prone to suffer from dizziness. The value of SpO2 and HR was improved both in AMS and non-AMS groups after hypoxia acclimatization, and the value showed greater improvement in AMS group. Oxygen therapy decreased the AMS-induced tachycardia, which had no any effect on SpO2 and symptom alleviating time.

Conclusion: Lower SpO2 and higher HR following exposure to high altitude were associated with AMS susceptibility. The anthropometric data changes were larger in AMS group than non-AMS group before and after hypoxia acclimatization.