Ventilatory acclimatization and csf acid-base balance in carotid chemodenervated dogs at 3550 m

In three awake dogs in a hypobaric chamber at 140 m and at 3550 m, resting ventilation, pulmonary gas exchanges, respiratory gases and pH of the arterial blood, acid-base status in the cerebrospinal fluid (csf), and ventilatory responses to transient O2-inhalation were studied before (intact) and after chronic bilateral carotid body denervation (cbd). 1. The hypoxic chemoreflex drive of ventilation was reduced by about half in cbd dogs. 2. At low altitude, sino-carotid body denervation resulted in hypoventilation and respiratory acidosis in the arterial blood and csf. 3. At high altitude, initial hypoxic hyperventilation, and the related alkalosis in blood and csf, occurred within 30 min in intact dogs, but was not observed in cbd ones. 4. Further increase in ventilation was achieved upon 3 hrs of altitude exposure in intact animals, while a delayed hyperventilation occurred after 24 hrs in cbd ones. 5. Neither in intact nor in cbd dogs, the ventilatory changes at altitude were related to the changes in csf pH. It is concluded that the rate of ventilatory acclimatization to altitude is dependent upon the strength of the arterial chemoreceptor drive. Integrity of this chemoreflex drive of breathing is essential in determining the eupneic level of ventilation and normal acid-base status of the blood and csf at low altitude and at high altitude.