To the Editor:
We appreciate the interest that our article “Post-exercise Peripheral Oxygen Saturation After Completion of the Six-minute Walk Test Predicts Successfully Reaching the Summit of Aconcagua” has generated. We agree with Dr Lankford that lower post-exercise peripheral oxygen saturation (SpO2) may be secondary to poor acclimatization or subclinical and/or reversible high altitude pulmonary edema.
Dr Lankford rightly states that ascent rate and prior acclimatization likely were factors in an individual's rate of acclimatization. As one of the seven summits, Aconcagua is an international destination attracting climbers with varying itineraries. While we did not standardize the acclimatization profiles of the volunteers in our study, we did report the mean (95% CI) for the time spent between camps. Although itineraries vary, the most common expedition profile was as follows: Day 0, acquire permit at Mendoza (746 m), spend night at Mendoza; Day 1, ground travel from Mendoza to Horcones (2955 m), spend night at Horcones; Day 2, trek from Horcones to Confluencia (3415 m), spend night at Confluencia; Day 3, rest day at Confluencia or day hike to Plaza Francia (4300 m), spend second night at Confluencia; Day 4, trek from Confluencia to Plaza de Mulas base camp (4365 m). Abbreviated itineraries would place climbers at increased risk of complications from suboptimal acclimatization.
Like Dr Lankford, we would expect post-exercise SpO2 to increase with improved acclimatization. The decision to continue an expedition or remain at base camp for further acclimatization is ultimately up to the individual climber. A number of factors, including individual health, time available, weather, supplies, and group dynamics, play into this decision. Objective information obtained at base camp such as post-exercise SpO2 may be part of this decision-making process but should not form the entire basis for this decision. The use of serial provocative tests, as suggested by Dr Lankford, is a novel idea that makes physiologic sense. Longer stays at base camp and improved post-exercise SpO2 after a subsequent test may improve a climber's odds of successfully reaching the summit and prevent high altitude complications. Continued cooperation on Aconcagua among park officials, healthcare personnel with high altitude experience, and climbers provides an excellent opportunity for future validation studies of the predictive ability of post-exercise SpO2.