Oxygen-hemoglobin Dissociation Curve

only a few questions left.... any help on the question below would be wonderful!! 


You have decided to ascend to the summit of Mount Everest where the partial pressure of oxygen in the atmosphere has been estimated to be about 54 mmHg. Once you breathe in this air, the partial pressure of oxygen in the alveoli drops even lower than this due to displacement by the partial pressure of carbon dioxide and water vapor. The arterial concentration of oxygen at the pulmonary capillaries is measured and found to be 25 mmHg.
How would the hemoglobin saturation curve shift in this situation? How would this help?