Hemoglobin Desaturation in Sickle Cell Disease

As part of routine care for SCD, some people are found to have low oxygen levels (≤ 88%) while sleeping, at rest, or with exercise. Testing is done with a small portable device positioned on the finger that measures oxygen levels during sleep, at rest, or following exercise. The investigators start oxygen treatment for people with low levels of oxygen. As a part of this study, the investigators will find out if any changes in cell "stickiness" occur with low oxygen levels (at rest, at night, or with exertion) and if cells become "less sticky" with oxygen treatment. Study subjects will be seen before testing and 2 months after testing. In some cases (people with low oxygen levels during testing), study subjects will have been prescribed oxygen, and the investigators will test the effects of that treatment on the stickiness of red cells.