Effect of Age on Oxygen-Binding in Normal Human Subjects

1. Oxygen-binding, plasma and intra-erythrocytic pH, and haemoglobin, 2,3-diphosphoglycerate and inorganic phosphate concentrations were measured in sixty-two healthy non-smokers aged between 18 and 89 years.

2. P₅₀ (oxygen tension at 50% oxygen saturation) expressed at plasma pH 7·40 and Pco₂ 5·33 kPa showed a positive correlation with age.

3. This correlation of P₅₀ with age was closer when P₅₀ was expressed at a constant intra-erythrocytic pH 7·20. On average P₅₀ at intra-erythrocytic pH 7·20 increased from 3·59 kPa at 20 years to 3·96 kPa at 90 years of age.

4. 2,3-Diphosphoglycerate, inorganic phosphate, haemoglobin and mean corpuscular haemoglobin concentrations did not correlate with P₅₀ or with age.