Increased hypoxic ventilatory response during 8 weeks at 3800 m altitude.

Acclimatization to chronic hypoxia (CH) increases ventilation (V(I)) and the isocapnic hypoxic ventilatory response (HVR) over 2-14 days but hypoxic desensitization blunts the HVR after years of CH. We tested for hypoxic desensitization during the first 2 months of CH by studying five normal subjects at sea level (SL) and for 8 weeks at 3800 m (CH, PI(O(2)) approximately 90 Torr). We measured the isocapnic HVR (Delta V(I)/Delta Sa(O(2)) and tested for hypoxic ventilatory decline (HVD) by stepping Sa(O(2)) to 80% after 14 min at 90%.