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. 2019 Sep;16(9):e17–e32. doi: 10.1513/AnnalsATS.201906-433ST

Figure 1.

Figure 1.

Oxyhemoglobin dissociation curve. Oxyhemoglobin saturation at a given arterial oxygen pressure (PaO2) (i.e., 40 mm Hg) is lower in patients with sickle cell disease (SCD) (right dashed line) than would be predicted by a normal oxyhemoglobin dissociation curve (solid line) because of increased 2,3 diphosphoglycerate (2,3 DPG) in sickled erythrocytes, as an adaption to severe anemia to prevent tissue hypoxia, or in the setting of hypoventilation with CO2 retention from pain, opioid use, and/or sleep-disordered breathing. The oxygen pressure (Po2) at which hemoglobin (Hb) is 50% saturated is about 27 mm Hg in normal subjects and about 33 mm Hg in patients with SCD. Reprinted by permission from Reference 178.