 The investigators study will focus on the types of RBC exchange therapy currently utilized in the investigators Infusion Clinic at T.C. Thompson Childrens Hospital. The investigators will determine which transfusion method is best for each participant for achieving the hematologic parameters of lower hemoglobin S quantification.The investigators will also measure the amount of nursing time for each procedure and which method is preferred by participants. The investigators will share the institutional observations with other institutions who may intend to switch between RMPET and ST. 