<prompt> The factor responsible for the left shift of Hb-O2 dissociation curve isIncrease in 2, 3 DPG in RBCFall in temperatureFall in pHIncrease level of CO2 blood  <response>: Hb-O2 dissociation curve shift to left indicates more affinity of Hb to O2 and thus less delivery of O2 to tissues.Shift to left seen in- Increased pH- Decreased 2,3 DPG, temperature, PCO2- HbF FetalShift to right seen in- Decreased pH- Increased 2,3DPG, temperature, PCO2- HbS Sickle cell 