Arterial hydrogen ion versus CO2 on depth and rate of breathing in decerebrate cats

Arterial blood hydrogen ion concentration (Ha+) was altered over the range of 25 to 110 nM (pH 7.60 to 6.96) by slow intravenous infusion of 1.0 N NaHCO3 or 0.5 N HC1 at controlled levels of Paco2in unanesthetized decerebrate cats. Respiratory f varied as a single function of Vt irrespective of a lterations in Paco2 and Ha+ even after interruption of the carotid sinus nerves. The dependence of f upon Vt was abolished by vagotomy. However, Vt continued to respond to changes in Ha+ over its entire range after combined section of the vagus and carotid sinus nerves. In all statxceeded by 5 to 10 times the delta Vt/delta Ha+ response to acid or bicarbonate infused under isocapnic control. Increases and decreases of ha+ caused downward and upward shifts, respectively, in the operating setpoint of the CO2 regulation system.