Ventilatory adaptation to a step change in PCO2 at the caotid bodies.

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Abstract
An overshoot in ventilation with subsequent adaptation was observed in response to a sustained step increase in PCO2 (CO2 pressure) of blood perfusing the carotid bodies of dogs in the absence of a significant change in PCO2 elsewhere in the body. The magnitude of adaptation was greater with increasing increments of PcOsi but proportionally was uniform at approximately 41% of the peak ventilation. Probably a rapidly changing PCO2 amplifies the chemical stimulus to ventilation through the carotid body mechanism. There was a significantly greater ventilatory response when the control PCO2 just prior to the step change was above 30 mm Hg. The onset of the amplified ventilatory response was delayed when the stimulus reached the carotid bodies during expiration. However, the information from the stimulus was not extinguished, since it expressed itself during the next breath. There was no undershoot of the mean ventilatory response following a step decrease in PCO2 at the termination of the perfusions. During isobicarbonate perfusions, the adaptation was still observed.