Predictive value of basal exhaled nitric oxide and carbon monoxide for acute mountain sickness

The purpose of this study was to examine the relationship between acute mountain sickness (AMS) and the fraction of exhaled nitric oxide (Fe(NO)) and carbon monoxide (Fe(CO)) before ascent to high altitude and to evaluate their predictive value for AMS.

A total of 314 healthy young male recruits were voluntarily enrolled. Before ascent to an elevation of 4300 m, their Fe(NO) and Fe(CO) values, demographic factors, drinking and smoking history, vital capacity, and forced vital capacity were obtained. The investigators followed the subjects in the first exposure week to obtain their Lake Louise Score (LLS) each day. Subjects with LLS > 4, headache, and at least 1 other symptom were diagnosed with AMS, and the highest LLS of each individual during 7 days was considered the final LLS score.

The AMS group had lower Fe(NO) (P = .003) and Fe(CO) (P < .001) values, and a lower smoking rate (P < .001) than the non-AMS group. Mean Fe(NO) and Fe(CO) values were 11.03 ppb (95% CI, 9.07 to 12.98) and 4.39 ppm (95% CI, 3.76 to 5.02), respectively, in the AMS group, and 14.74 ppb (95% CI, 13.25 to 16.23) and 6.10 ppm (95% CI, 5.49 to 6.72), respectively, in the non-AMS group (P < .0001). Using linear regression, both Fe(NO) and Fe(CO) were found to be significantly associated with the group's maximal LLS. Using logistic regression, Fe(NO) and Fe(CO) were also found to be significantly associated with AMS.

Basal Fe(NO) and Fe(CO) are significantly negatively correlated with AMS development. However, the gases have only modest predictive value for the development of AMS.