Nitric Oxide Therapy for Acute Chest Syndrome in Sickle Cell Disease Children

Inclusion Criteria: * child between 1 and 18 years old * Sickle cell anemia or equivalent (sickle beta 0 thalassemia)whoe weight is between 10kg and 65kg * presenting acute chest syndrome as defined a new radiological infiltrate with tachypnea, respiratory discomfort, cough, chest wall pain and fever more than 38.5°C * hypoxaemia with transcutaneous oxygen saturation equal or less than 92% * informed consent signed by parents and approved by the child able to express his consent * insured by the National social security system or by the universal medical insurance * previous medical physical examination Exclusion Criteria: * respiratory distress with hypoxaemia with transcutaneous oxygen saturation equal or less than 92% under more than 5l/min of oxygen or 40% oxygen inhaled, hypercapnia signs 'sweating, altered consciousness, paCO2 more than 60mmHg) with need of emergency exchange transfusion and/or tracheal intubation with mechanical ventilation * Isolated acute asthmatic crisis * stroke or priapism with emergency acute transfusion needed * acute anemia with hemoglobin drop of more than 20% as compared to steady state hemoglobin * chronic long term transfusion therapy * nitric oxyde hypersensitivity * patients with right-left extra-pulmonary cardiac shunt * patient previously included in the protocol * patient participating in another interventional protocol * pregnancy or breast feeding