A specific objective supplemental factor in evaluating acute mountain sickness: ΔHR in combination with SaO(2)

BACKGROUND: So far, there have been no measurements confirmed useful in diagnosing acute mountain sickness (AMS). The aim of this study was to determine the role of heart rate (HR) difference (ΔHR) and oxygen saturation ( SaO(2)) as objective risk factors in aiding the diagnosis of AMS. METHODS: A total of 1,019 participants were assigned to either the acute exposure group (AEG): from 500 m to 3,700 m by flight within 2.5 h (n = 752); or the pre-acclimatization group (PAG): ascended to 4,400 m from 3,650 m within three hours by car after adapting 33 days at 3,650 m (n = 267). The questionnaires or measurements of resting SaO(2) (oxygen saturation) and HR were completed between 18 and 24 h before departure and after arrival. RESULTS: Incidence of AMS was 61.3 % (461) in AEG, with 46.1 % (347) mild cases and 15.2 % (114) severe cases. In PAG, the incidence was 38.9 % (104), with 30.7 % (82) mild cases and 8.2 % (22) severe cases. The AMS subjects showed a significant increase in HR and a decrease in SaO(2) levels compared with the non-AMS subjects in both groups. ΔHR and post-exposure SaO(2) were significantly correlated with the Lake Louise Score (LLS) in both groups. Stepwise logistic regression analysis revealed the ΔHR >25 and SaO(2) < 88 % in AEG as well as ΔHR >15 and SaO(2) < 86 % in PAG to be independent risk factors of AMS. Combining these two measurements could specifically indicate participants with AMS, which showed a positive predictive value of 89 % and specificity of 97 % in AEG as well as 85 % and 98 % in PAG. CONCLUSION: ΔHR or SaO(2), as objective measurements, correlate with AMS. Combination of these two measurements may be useful as an additional specific and objective factor to further confirm the diagnosis of AMS.