The shift of the oxygen dissociation curve to the left is facilitated by all except

When the blood becomes slightly acidic, with the pH decreasing from the normal value, the O2-hemoglobin dissociation curve shifts, to the right. Conversely, an increase in pH from the normal shifts the curve a similar amount to the left. In addition to pH changes, several other factors are known to shift the curve. Three of these, all of which shift the curve to the right, are Increased CO2 concentration Increased blood temperatureIncreased 2,3-biphosphoglycerate (BPG)Ref: Guyton and Hall textbook of medical physiology 13th edition. Page: 532