Effects of High-flow Oxygen Therapy and Non-invasive Ventilation on Lung Volumes and on Upper Airway

Respiratory failure is the most frequent organ failure and cause for admission in the Intensive Care Unit (ICU) . It is a severe complication with an ICU mortality ranged from 31% to 33%. Symptomatic treatment of hypoxemic respiratory failure is a controversial topic with different options: 1) standard oxygen therapy, 2) high flow nasal cannula oxygen therapy (HFNC) and 3) non-invasive ventilation (NIV).The aim of the study is to compare HFNC versus NIV ventilation using CT scan. The hypothesis of this study is that in hypoxemic critically ill patients, the increase of lung volumes with NIV would be significantly higher than the increase of lung volumes with HFNC.

Inclusion Criteria:Patient with hypoxemia at any time of ICU stay defined as follow: standard oxygen therapy flow ≥ 3L/min to maintain a pulsed oxygen saturation ≥ 95%Adult (age ≥ 18 years)(2) A CT scan prescribed by the physician in charge of the patient as part of the exploration of the patient's pathology and not as part of a "dedicated" prescription for the study.Exclusion Criteria:NIV contraindication (need for immediate endotracheal intubation and mechanical ventilation; hemodynamic instability defined by systolic blood pressure < 90 mmHg or mean blood pressure < 65 mmHg, use of vasopressors; Glasgow Coma Scale score of 12 points or less)History of recent facial trauma not compatible with the use of nasal cannulasPregnancyRefusal of study participationprotected personPatient not affiliated to the social security system or not benefiting from such a systemLack of signed informed consent