RESPONSES TO ALTERATIONS IN RESPIRATORY PO2 AND PCO2 IN CHICKEN

Simultaneous measurements of blood pressure, heart rate, tracheal pressure, respiratory rate and respiratory amplitude were made during the administration of various concentrations of carbon dioxide and oxygen via an unidirectional, artificial respirator to anesthetized chickens. When Flo was held constant (18 or 20%) and FCO2 was varied between 0% and 20%, blood pressure and heart rate increased as CO2 levels were increased. Respiratory rate and amplitude were zero at CO2 levels below 4%. Respiratory rate remained constant at CO2 levels above 6%, while respiratory amplitude increased continuously as CO2 levels were raised from 4% to 20%. Resistance to air flow by the intra- and/or extrapulmonary tubular system was reduced at the elevated CO2 levels. When FCO was held constant (5 %) and FO2 was varied between 50 % and 6 %, blood pressure fell at Flo below 12% while heart rate increased during hypoxia. Respiratory rate was markedly increased at low O2 levels, while respiratory amplitude was only moderately increased. The resistance to air flow of the respiratory system was decreased during hypoxia. The chicken may have separate chemoreceptor systems that cause different respiratory responses to hypercarbia than to hypoxia. © 1969.