Visual Analog Scales for Assessment of Severe Acute Mountain Sickness on Aconcagua
Background.-The Lake Louise AMS Self-report Score (LL-Self) is a commonly used, validated method of assessing acute mountain sickness (AMS).
Objectives.-Compare a visual analog scale (VAS) method of quantifying AMS with the LLSelf among trekkers to 6962 m for both overall symptoms and the 5 individual constituent categories of the LLSelf.
Methods.-Setting: Plaza de Mulas base camp (4365 m), Aconcagua Provincial Park, Argentina. Inclusion criteria: volunteer trekkers to Aconcagua (6962 m) in January 2009 who provided written informed consent. Exclusion criteria: pregnancy, age ฯฝ18 years. Study protocol: Subjects were prospectively enrolled while ascending, instructed to complete a questionnaire when symptoms were maximal, and return it upon descent. The questionnaire consisted of maximum altitude reached, the LLSelf, and standard 100-mm VAS for each LLSelf component, as well as overall AMS. Statistics: means with 95% confidence interval (CI), interrater reliability with Cohen's , and correlation of VAS with LLSelf with Spearman's rank correlation coefficient (r) were computed using Stata (Stata Corp, College Station, TX).
Results.-A total of 45 subjects completed both VAS and LLSelf. Twenty-two (49%) climbers reached the summit (6962 m). Mean maximum altitude reached was 6467 m. Mean altitude of maximal symptoms was 5859 m. Mean LLSelf was 5.1 (95% CI, 4.3-5.9). Interrater reliability for measurement of VAS was high ( ฯญ 0.9998). All individual VAS categories were highly correlated with their respective LLSelf symptoms: headache r ฯญ 0.85; gastrointestinal symptoms r ฯญ 0.57; fatigue r ฯญ 0.79; lightheadedness r ฯญ 0.72; and difficulty sleeping r ฯญ 0.75. Overall VAS was also highly correlated with total LL-Self: r ฯญ 0.71.
Conclusions.-In this study of VAS and LLSelf at extreme altitude on Aconcagua (6962 m), individual VAS and overall VAS were highly correlated with both individual constituent categories of LLSelf and overall LLSelf. Further studies comparing VAS, LLSelf, and physician assessment of AMS are needed to determine optimal measurement of AMS, especially on expeditions where multiple languages are encountered.