title: Avian ventilatory responses to dynamic CO2 signals.
abstract: This study uses an awake unidirectionally ventilated avian preparation to examine the effects of dynamic CO2 signals on the respiratory drive. Results show that minute ventilation is affected by both 1) mean CO2 level and 2) amplitude of CO2 oscillations at the frequency of breathing. An increase in mean CO2 level increased minute ventilation. Comparisons of the effects of CO2 oscillations at the same mean CO2 level, however, showed minute ventilation to be less with the larger amplitudes of oscillations than with smaller ones. Graphs of minute ventilation (V)  versus mean CO2 for families of oscillation sizes (0.5%, 1% and 2%) showed that the ventilatory sensitivity (slop) was least for the 2% oscillations and greatest for the 0.5% oscillations. Therefore, a static model for the respiratory regulator is not adequate. However, the apneic level of CO2 (V = O intercept) was independent of the size of the CO2 oscillations.
mesh_terms: D000818:Animals; D001717:Birds / Q000502:physiology*; D002245:Carbon Dioxide; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D010993:Plethysmography, Whole Body; D012119:Respiration; D012125:Respiratory Center / Q000502:physiology; D013990:Tidal Volume; D014692:Ventilation-Perfusion Ratio
chemical_list: D002245:Carbon Dioxide