High-flow Oxygen for Vaso-occlusive Pain Crisis

Inclusion Criteria: * Age ≥ 18 years; * Patient with major sickle cell disease syndrome (SS, SC, Sβ0 or Sβ+); * VOC as defined by acute pain or tenderness, affecting at least one part of the body, including limbs, ribs, sternum, head (skull), spine, and/or pelvis, that requires opioids and is not attributable to other causes; * Intermediate-to-high risk for secondary ACS derived from the PRESEV score (Bartolucci et al, EBioMedicine 2016) as follows: a reticulocyte count \>216 G/L OR at least two of the followings : i) spine and/or pelvis CPS \>1; ii) leucocyte count \>11G/L; iii) hemoglobin ≤ 9 g/dL; in case of long-term treatment by hydroxyurea, only one of the above mentioned criteria will be needed, given its effects on hemoglobin, leucocyte and reticulocytes counts; * Informed consent; * Patient affiliated to social security Exclusion Criteria: The presence at inclusion of a primary ACS. Primary ACS is defined by the combination at time of randomization of a clinical sign \[chest pain or auscultatory abnormality (crepitants and/or bronchial breathing)\] with a new pulmonary infiltrate (on chest film, thoracic scan, or lung ultrasound); * VOC with need of parenteral opioids lasting longer than 72 hours at time of inclusion; * Known pregnancy or current lactation; Women of child bearing potential will be tested for pregnancy before inclusion; * Known cerebral vasculopathy or past medical history of stroke, due to Moya Moya or persisting visible macrovessel stenosis/occlusion; * Known ischemic heart disease or typical chest angina; * Patient who is currently enrolled in other investigational drug study; * Known legal incapacity, * Prisoners or subjects who are involuntarily incarcerated * Anatomical factors precluding placement of a nasal cannula