**Sickle-cell disease** is a blood disorder that can lead to **acute chest syndrome (ACS)**, which is a serious lung problem. ACS happens when there is a blockage or infection in the lungs. **Lung ultrasound (LUS)** is a tool doctors use to help see what's happening in the lungs of kids with ACS, without having to do surgery. This study is being done to find out how LUS can help doctors understand how long a child might need help breathing when they have ACS. The study will last for 2 years and will include 60 children aged 1 month to 17 years, who are in the *Pediatric Intensive Care Unit (PICU)* at Robert-Debre Hospital with ACS.
- The study will take place over 2 years, with 60 children participating.
- Children will receive multiple lung ultrasounds during their stay.
- Data about their health and care will be collected during the study.