Hemoglobin's affinity for oxygen is how much oxygen is actually currently held by the hemoglobin. so, if hemoglobin has high oxygen saturation, hemoglobin's affininty for oxygen is high. what do you think happens to hemoglobin's affinity for oxygen as it moves through the systemic capillaries? as the rbc moves through the systemic capillary, hemoglobin's affinity for oxygen increases. as hemoglobin moves through the systemic capillary, hemoglobin's affinity for oxygen stays the same. as the rbc moves through the systemic capillary, hemoglobin's affinity for oxygen decreases.