In response to Covid-19 crisis, 310 Masi ventilators were produced and validated in Lima, Peru, according to applicable standards. Four of them, were transported to Puno, in order to strengthen ICU Services there, but this set a major challenge to Masi team as effects of altitude on ventilators were unknown. Once there, ventilators were acclimated and calibrated. Volume tidal, I:E ratio, respiratory frequency and PEEP were tested, all of them presenting errors under 15%, except for tidal volume, for which a 25% negative correction was applied. After the installation of a new version of Masi software, parameters were tested again, all of them presenting results with errors below 15%, which allowed the Masi team to take them to ICU services for use.Clinical Relevance - Masi Peruvian Ventilators are able to perform according to their specifications at extremely high altitude, after the adequate calibration. These devices are an alternative to treat COVID-19 patients in the middle of the crisis.