Rebuttal to the Pro Statement

Abstract

Richalet and Canoui-Poitrine (Richalet and Canoui-Poitrine, 2014) present data from a new, not-yet-published analysis of their previously reported data (Richalet, Larmignat et al., 2012) addressing the hypothesis mentioned in the con statement (Bärtsch 2014) that physiologic measurements might be more helpful in individuals with an unknown history of acute altitude illnesses. Indeed, adding data obtained by a hypoxic exercise testing to those obtained by history taking increased precision of prediction in this group by 17 percentage points from 0.72 to 0.89 (AUC) compared with an increase of only 7 percentage points from 0.84 to 0.91 in those with a history of altitude exposure. This additional analysis suggests that testing proposed by Richalet et al. might possibly be helpful in advising those who have never been to high altitude before, while it demonstrates that this testing provides little benefit in altitude-experienced individuals.

For several reasons it remains questionable, however, whether hypoxic exercise testing will prevent SHAI better in high altitude naive people than the approach recommended in various guidelines (Luks, McIntosh et al. 2010, Bartsch and Swenson 2013):

1. The same limitations discussed in my initial statement also apply to the data on which this new analysis was performed: single center study, possible selection bias due to low response rate, data based on self-observation and possible recall bias.

2. The danger of self-fulfilling prophecy in the false positive subjects and providing a false sense of security in those, who are false negative, is greatest in people with no previous experiences at high altitude.

3. Severe high altitude illnesses (SHAI) can be prevented effectively by adequately responding to early symptoms of high altitude illnesses.

Before one can recommend hypoxic exercise testing for risk assessment in people going to high altitude with no previous altitude exposure, we need controlled, prospective studies in various populations (tourists, trekkers, variability of age, fitness level, and destination) demonstrating that this procedure is significantly better for preventing SHAI compared with giving recommendations based on the present guidelines (Luks, McIntosh et al. 2010, Bartsch and Swenson 2013). In support of this approach, Richalet and Canoui-Poitrine encourage other centers involved in mountain medicine to validate their model for prediction. In order to do so, these centers need a full publication of the new analysis shown in Table 1 and the algorithm that converts the data obtained by history-taking and exercise testing to a risk score.

References

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(2014),. Con: Hypoxic cardiopulmonary exercise testing identifies subjects at risk for severe high altitude illnesses. High Alt Med Biol, 15:318–320.

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(2012). Physiological risk factors of severe high altitude illness: A prospective cohort study. Am J Respir Crit Care Med, 185:1092–1098.