Response of intrapulmonary chemoreceptors in the duck to changes in PCO2 and pH

We have estimated the relative importance of changes in blood PCO2 and pH in determining activity of intrapulmonary chemoreceptors (IPC) in the unidirectionally ventilated duck. The response of single unit vagal afferents from IPC to changing lung gas PCO2 was tested before and after changing blood pH by intravenous infusion of NaHCO3. Using multiple linear regression analysis, we calculated how much of the change in IPC activity for a given change in PCO2 was due to the changing PCO2 at constant pH (CO2 sensitivity) or to the change in pH concomitant with the change in PCO2 (H+ sensitivity). For 10 IPC, the CO2 sensitivity was on the average 2.3 times larger than the H+ sensitivity. Changes in pH as well as PCO2 of lung blood should be considered in assessing the role of IPC in control of breathing.