Acclimatization to altitude

At high altitude the partial pressure of oxygen is reduced in the inspired air. Various adaptive processes occur if there is chronic exposure to oxygen levels at high altitude.

Acclimatisation is the process of the body adjusting to the decreasing availability of oxygen.

Acclimatisation (biochemical changes) usually occurs from about 1500m (5000ft)

• acute adaption
  • increased respiratory rate } mediated by peripheral
  • hypocapnia } chemoreceptors which are sensitive to oxygen (respiratory alkalosis)
  • arterial oxygen saturation drops
  • hyperventilation is reversible if oxygen is administered during the first 5-10 days. After this period hyperventilation is unaffected by inspiration of increased partial pressure oxygen
• other changes
  • polycythaemia - may take months to develop fully
  • oxygen dissociation curve is shifted to the right - thus the oxygen affinity for haemoglobin is reduced and this facilitates oxygen delivery to the tissues. The shift of the oxygen dissociation curve is mediated by the increased levels of 2,3 diphosphoglycerate in red cells produced as a result of hypoxia