Acid-base disturbance and ventilatory response to changes in plasma osmolality in Pekin ducks

Abstract

The effects of acute changes in plasma osmolality on blood acid-base status and ventilation were investigated in the Pekin duck, Anas platyrhynchos. Hyperosmolality due to intravenous infusion of hypertonic NaCl or sucrose caused a prolonged acidosis (so-called dilution acidosis), which was attributable to a decrease in estimated strong ion difference due to a fall in the plasma [ Na +] : [ Cl −] ratio. Ventilation did not increase in response to the acidosis, and was actually depressed in some birds. Pa CO 2 increased by 3.5 ± 1.5 Torr and Pa O 2 decreased by 4 ± 2 Torr over the 2 h experimental period in all animals. It is suggested that the extracellular acidosis due to hyperosmolality is accompanied by an intracellular alkalosis which may suppress chemoreceptor stimulation, resulting in no ventilatory increase. Hyposmolality had no effect on acid-base status or respiration.