Table 4.

Mechanisms of Nocturnal Oxygen Desaturation in Sickle Cell Disease

•Rightward shift of the oxygen-hemoglobin dissociation curve due to dyshemoglobins, carboxyhemoglobin, and methemoglobin, which are unable to transport oxygen54, 91

•Decreased oxygen-carrying capacity due to chronic anemia

•Anemia-related rightward shift of the oxygen dissociation curve (ODC) due to the increased production of 2,3-diphosphoglycerate. This leads to less oxyhemoglobin saturation at a given Pao2 than would be predicted by a normal ODC53

•Hypoventilation secondary to upper airway obstruction and obstructive sleep apnea53

•Ventilation-perfusion mismatch due to pulmonary vascular disease, asthma/airway hyperreactivity, and micro-occlusion of parts of the vascular tree92

•Reduced effective diffusion of oxygen into sickle erythrocytes at a low Pao2

•Intracardiac shunt related to patent foramen ovale