Class 11 NEET Biology Breathing and Exchange of Gases

(c) : At high altitudes composition of air remains almost same as at sea level, but density (barometric pressure) of air gradually decreases due to which arterial pO2 is also decreased (hypoxemia). High altitudes presents with complex conditions to which human body has to acclimatize. Number of red blood cells per unit volume of blood is likely to be higher in a person living at high altitudes. This is in response to the air being less dense at high altitude. More number of red blood cells are needed to trap O2, from rarefied air having low pO2 (partial pressure of oxygen).