Acute chest syndrome is a severe complication of sickle cell disease. Several factors can contribute to this complication including infections, vaso-occlusive crisis, important pain that may give shortness of breath and morphinic treatments as they may cause hypoventilation.~The standard prevention of this dangerous complication is incentive spirometry in wich patient is required to take deep breaths trough a little device several times a day. This treatment is compromised when pain in important or when the patient is asleep and cannot participate.~In patients who have had surgery who have also pain and morphinic treatments, non invasive ventilation have proven a good option for preventing pulmonary complications.~Besides, our experience in non invasive ventilation for treatment of acute chest syndrome show a good tolerance and efficiency. It also seems to help with pain management.~The investigators hypothesised that non invasive ventilation in wich patient have no effort to take might be a better prevention than incentive spirometry and may improve pain and quality of sleep.~After informed consent, patients aged from 6 to 20 years old with SS or S-Beta sickle cell disease with vaso-occlusive crisis necessitating morphinic treatment hospitalised in intensive care unit in Necker Hospital for Sick Children (Paris) will be randomly assigned with either spirometry or ventilation. It is a monocentric study.~Patients with acute chest syndrome, oxygen needs, pneumonia or other condition requiring ventilation at presentation will not be included.~Spirometry will be realised through volumetric devices, every two hours during the day with 10 maximum inspirations and at night if the patient is awake.~Non invasive ventilation will be applied through a nasal mask with VS III machines from Resmed®, at least one hour every four hour but may be maintained more if the patient chooses to or is asleep with the machine on.~The investigators will monitor for occurrence of acute chest syndrome, pain, morphinic requirements, length of hospital stay, comfort, quality of sleep The treatment will be continued until morphinic treatment is stopped. The investigators intend to include 60 patients in each arm to show a difference of 25% in the occurrence of acute chest syndrome (primary judgement criteria).~Acute chest syndrome will be defined according to the criteria used by Vichinsky (Vichinsky, E. P. et al. Acute chest syndrome in sickle cell disease: clinical presentation and course. Cooperative Study of Sickle Cell Disease. Blood 89, 1787-1792 (1997) The investigators will aslo compare morphinic requirements, length of hospital stay and quality of sleep as secondary judgment criteria.
Acute chest syndrome is a severe respiratory complication of sickle cell disease.~The standard prevention of this dangerous complication is spirometry in wich patient is required to take deep breaths trough a little device several times a day. This treatment is compromised when pain in important or when the patient is asleep and cannot participate.~The investigators hypothesised that non invasive ventilation in wich patient have no effort to take might be a better prevention than spirometry and may improve pain and quality of sleep.~Children with vaso-occlusive crisis necessitating morphinic treatment will be randomly assigned with either spirometry or ventilation and the investigators will monitor for occurrence of acute chest syndrome, pain and quality of sleep.