COVID-19 may cause severe pneumonitis that require ventilatory support in some patients, the ICU mortality is as high as 62%. Hospitals do not have enough ICU beds to handle the demand and to date there is no effective cure. We explore a treatment administered in a randomized clinical trial that could prevent ICU admission and reduce mortality. The overall hypothesis to be evaluated is that HBO reduce mortality, increase hypoxia tolerance and prevent organ failure in patients with COVID19 pneumonitis by attenuating the inflammatory response.