Chemoreflex drive of ventilation during exercise in ducks

To determine if arterial chemoreceptors contribute to the ventilatory response during exercise, we measured minute ventilation ( \(\dot V\) ₁) in spontaneously breathing Pekin ducks (Anas platyrhynchos) during rest and running exercise when the inspired gas was switched from either 21% or 12% O₂ to 100% O₂ for 45 s (O₂-test). In normoxia at rest (PaO₂=99 Torr), inhaling 100% O₂ reduced \(\dot V\) ₁ by 30%, while during resting hypoxic conditions, (PaO₂=56 Torr), 100% O₂ inhalation reduced \(\dot V\) ₁ by 66%. During exercise, abruptly inhaling 100% O₂ decreased \(\dot V\) ₁ by only 14% and 33% in normoxic and hypoxic conditions, respectively. Thus, only a small fraction of the ventilatory response during exercise under normoxic conditions is due to an arterial chemoreceptor input. However, during exercise in hypoxic conditions, arterial chemoreceptors provide a substantial portion of the total drive to ventilation.