Investigators and Ethic Committee endorsed early suspension of the protocol because of superiority and safety. For the interim analysys, the statistical methodology presented by Pocock was followed.

The severity of COVID-19 is related to the level of hypoxemia, respiratory failure, how long it lasts and how refractory it is at increasing concentrations of inspired oxygen. The inability to perform hematosis due to edema that occurs from acute inflammation could be attenuated by the administration of hyperbaric oxygen (HBO). Recently, it has been reported benefits in this matter in patients with SARS-CoV-2 hypoxemic pneumonia in China; where the administration of repeated HBO sessions decreased the need for mechanical ventilation (MV) in patients admitted to the Intensive Care Unit due to COVID-19. Hyperbaric oxygen is capable of increasing drastically the amount of dissolved oxygen in the blood and maintain an adequate supply oxygen to the tissues. In addition to this, it can influence immune processes, both humoral and cellular, allowing to reduce the intensity of the response inflammatory and stimulate antioxidant defenses. HBO is considered safe and it has very few adverse events, it is a procedure approved by our authorities regulatory for several years. In the current context of the pandemic by COVID-19 and worldwide reports of mortality associated with severe cases of respiratory failure, it is essential to propose therapeutical strategies to limit or decrease respiratory compromise of severe stages by COVID-19. That is why, it is proposed to carry out this research to assess whether HBO treatment can improve the evolution of patients with COVID-19 severe hypoxemia.

Inclusion Criteria:

• 18 years, all sexes.
• No previous hospitalizations in the last 6 months.
• Positive diagnostic test for COVID-19 according to the guidelines of the Argetine Ministry of Health at the time of enrollment.
• Patient in Intensive Care Unit with oxygen need: Need for continuous supply of oxygen to maintain saturation by oximetry pulse (SpO2) greater than or equal to 93% or arterial gas with PaO2 value greater than 60 mmHg

Exclusion Criteria:

• 18 years of age.
• Person unable to give consent.
• Person who refuses to participate.
• Pregnancy and lactation
• Participating in other study
• Requirement for mechanical ventilation.
• Inability to maintain prolonged sitting position (at least 2 hours)
• Subject with contraindications to HBOT (pulmonary shock, bullae, emphysema or untreated pneumothorax, severe seizures, uncontrolled hypertension, chronic obstructive disease of grade III or IV).