Letters Section Editor: Jody W. Zylke, MD, Senior Editor.
Author Affiliations: Department of Critical Care Medicine, Instituto Nacional de Cancerología, Mexico City, Mexico (Dr Namendys-Silva; firstname.lastname@example.org); and Department of Anesthesiology, American British Cowdray Medical Center, Mexico City, Mexico (Dr Hernandez-Garay).
To the Editor: The updated and revised Berlin Definition for acute respiratory distress syndrome (ARDS)1 suggested correction of the ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO2/FIO2) if the altitude is higher than 1000 m. We agree with this recommendation; however, we believe that it applies only to patients spontaneously breathing room air. People who live at high altitudes have ventilatory acclimatization to low PaO2.2 Pérez-Padilla3 estimated in 2002 that in Mexico, approximately 5% of the population lived at altitudes 2500 m above sea level, and half lived above 1550 m. In normal persons, upon exposure to an altitude such as that of Mexico City (2240 m), an increase in the FIO2 returns the PaO2 to levels achieved at sea level.2
Namendys-Silva SA, Hernández-Garay M. Definition of Acute Respiratory Distress Syndrome. JAMA. 2012;308(13):1321. doi:10.1001/2012.jama.11889