This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Acclimatization to a high altitude is associated with which of the following changes? 
Select and explain. 
A. Hyperventilation, B. Polycythemia, C. O2 dissociation curve shifts to right, D. Decreased concentration of systemic capillaries
C: O2 dissociation curve shifts to right
Answer: C: O2 dissociation curve shifts to right 
Explanation: Oxygen hemoglobin dissociation curve, is the curve relating percentage saturation of the oxygen carrying power of hemoglobin to the PO2. It has a characteristic sigmoid shape due to the T-R interconversion. In deoxyhemoglobin, globin units are tightly bound in a tense (T) configuration which reduces the affinity of the molecule for oxygen. When the first oxygen is bound, the bonds holding the globin units are released, producing a relaxed (R) configuration which exposes more oxygen binding sites. Thus, binding of one oxygen molecule increases the affinity of hemoglobin to bind other O2 molecules. Ascent to high altitude triggers a substantial rise in 2,3 DPG concentration in red blood cells. Factors causing shift of the curve to right includes: Fall in pH Rise in temperature Increase in 2, 3 BPG pH of the blood falls as its CO2 content increases, so that when PCO2 rises the curve shifts to right. Ref: Textbook of Medical Physiology By Guyton, 10th Edition, Page 466 ; Ganong's Review of Medical Physiology, 23rd Edition, Page 667-9