Since the beginning of COVID-19 pandemic situation, several modes of ventilation have been tried to correct the hypoxaemia induced by SARS-CoV-2 virus. A few recent studies have concluded that high-flow nasal oxygen therapy (OptiFlow™) is beneficial in COVID-19. All mainly conclude that the use of OptiFlow™ avoid intubations and decrease hospitalization duration in critical care services.

At the emergency medical service 83 (SAMU 83), it has been decided to extend this ventilation mode during patient secondary transfers (transfer from an intensive care unit/other hospital unit/emergency department to another hospital's intensive care unit).

The emergency medical service 83 has equipped its intensive-care ambulances with OptiFlow™ in order not to interrupt this ventilation mode during transport.

The hypothesis is that patients with a severe respiratory form of COVID-19 transported from one health facility to another by the emergency medical service 83 on high-flow nasal oxygen therapy has a reduced risk of intubation compared to the other modes of non-invasive ventilation (NIV) and High Concentration oxygen Masks (HCM).

Retrospective observational study in France including COVID-19 infected patients taken care of by the emergency medical service 83 (SAMU 83) for a secondary transport between1st March 2020 and 31th December 2021.

Inclusion Criteria:

• COVID-positive patient diagnosed either by positive Polymerase Chain Reaction (PCR) or radiological interpretation of chest CT
• Patient in respiratory distress treated during transport by high flow nasal oxygen or HCM (with a minimum flow of 15 L/min) or other NIV modes
• Patient taken care of by the emergency medical service 83 (SAMU 83) for secondary transport (transfer from an intensive care unit/other hospital unit/emergency department to another hospital's intensive care unit) between1st March 2020 and 31th December 2021

Exclusion Criteria:

• Pre-transport intubation
• Patient opposition to participate in the study

Patients more than 18 year old taken care of by the emergency medical service 83 (SAMU 83) for secondary transport (transfer from an intensive care unit/other hospital unit/emergency department to another hospital's intensive care unit) between1st March 2020 and 31th December 2021 and without pre-transport intubation