Acid–base results normally report arterial values: overall acidity (pH), Paco2, and Standard Base Excess (SBE). Although numerical values are customary, an interactive diagram (http://www.acid-base.com/interactive.php, accessed September 25, 2020) helps recognition by displaying results over zones radiating out from a normal center based on a meta-analysis of relevant papers (figs. 1 and 2). The numerical values and the text are appropriate for managing patients at or near sea level. However, as altitude increases, the ventilatory response to hypoxia induces chronic respiratory alkalosis, leading to a reduction in serum bicarbonate and thus progressively misleading results.

One author (I.S.) recognized the critical need for altitude-appropriate values, diagram, and text interpretations. He provided the equation relating altitude to acid–base diagrams, as well as the concept that in healthy altitude-adapted individuals, the metabolic...

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