oxyhaemoglobin dissociation curve


Also found in: Acronyms.

ox·y·he·mo·glo·bin dis·so·ci·a·tion curve

(ok'sē-hē'mŏ-glōb'in di-sō'sē-ā'shŭn kŭrv)
A graphic illustration of the relationship between oxygen saturation of hemoglobin and the partial pressure of arterial oxygen (PaO2); the position and overall shape of this sigmoidal curve are affected by the hydrogen ion concentration (pH), body temperature, partial pressure of carbon dioxide (PCO2), and organic phosphates.
Synonym(s): oxyhaemoglobin dissociation curve, oxyhaemoglobin dissociation curve.
Oxygen in the blood: the oxyhaemoglobin dissociation curve. a1, a2: arterial blood at altitudes of ∼2500m and ∼5000m.

oxyhaemoglobin dissociation curve

the graph which describes the relationship in the blood between partial pressure of oxygen ( P O2) and the percentage saturation of haemoglobin; it can also show the equivalent oxygen content of the blood when haemoglobin is in normal concentration. With normal lungs, saturation in arterial blood is determined by the P O2 in the alveolar gas with which pulmonary capillary blood equilibrates. The S-shape of the curve has important physiological advantages, e.g. a relatively small decrease in P O2 encountered where blood flows through tissues causes a 'steep' removal of oxygen from the blood; but there needs to be a relatively large decrease in P O2 in the inspired air (and therefore in the alveoli, e.g. at altitude or in a confined space) before there is a serious decline in haemoglobin saturation. ( See fig overleaf .)