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The Spo(2) does not appear to be predictive of AMS or summit success during rapid ascents.

Introduction-North American guidelines propose 125 mg acetazolamide twice daily as the recommended prophylactic dose to prevent acute mountain sickness (AMS). To our knowledge, a dose lower than 125 mg twice daily has not been studied. Methods-We conducted a prospective, double-blind, randomized, noninferiority trial of trekkers to Everest Base Camp in Nepal. Participants received the reduced dose of 62.5 mg twice daily or the standard dose of 125 mg twice daily. Primary outcome was incidence of AMS, and secondary outcomes were severity of AMS and side effects in each group. Results-Seventy-three participants had sufficient data to be included in the analysis. Overall incidence of AMS was 21 of 38 (55.3%) in reduced-dose and 21 of 35 (60.0%) in standard-dose recipients. The daily incidence rate of AMS was 6.7% (95% CI 2.5À10.9) for each individual in the reduced-dose group and 8.9% (95% CI 4.5À13.3) in the standard-dose group. Overall severity of participants' Lake Louise Score was 1.014 in the reduced-dose group and 0.966 in the standard-dose group (95% CI 0.885À1.144). Side effects were similar between the groups. Conclusions-The reduced dose of acetazolamide at 62.5 mg twice daily was noninferior to the currently recommended dose of 125 mg twice daily for the prevention of AMS. Low incidence of AMS in the study population may have limited the ability to differentiate the treatment effects. Further research with more participants with greater rates of AMS would further elucidate this reduced dosage for preventing altitude illness.

The purpose of this study was to compare three commonly used scoring systems of acute mountain sickness (AMS)-the 5-item Lake Louise Self-report (LLS), the 11-item abridged version of the Environmental Symptoms Questionnaire (ESQ-III), and a 100 mm visual analog scale (VAS)-on climbers (N=63; 34.6±9.9 years) making a 1-day ascent of a 5640 m peak after a rest of ~10 h at 4260 m. The prevalence of AMS was 63% when defined as LLS ≥3, 49% when defined as either LLS ≥5 or ESQ-III ≥0.7, and 41% when defined as the combined LLS and ESQ-III criteria. Despite the agreement in prevalence between the LLS ≥5 and ESQ-III ≥0.7, there was a discrepancy in AMS classification in 16% of the cases. A VAS cut-off point corresponding to the combined LLS and ESQ-III criteria was 16 mm. The sensitivity and specificity of the VAS for diagnosing AMS compared to combined LLS and ESQ-III criteria were 85% and 92%, respectively. All of the scoring systems were significantly correlated (τ=0.60 to 0.73, p<0.01); however, residual scores were large. We cannot recommend interchanging the diagnostic results from the LLS, ESQ-III, and VAS, and standardization is needed for the administration of the VAS.

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