Critical dependence of respiratory rhythmicity on metabolic CO2 load

Abstract

The dependence of respiratory rhythm generation on the rate of CO2 production (.ovrhdot.VCO2) in 6 awake sheep using a venous-to-venous extracorporeal perfusion circuit that included 2 CO2 membrane lungs (CDML) designed to facilitate the removal of CO2 from blood. As progressively greater proportions of the resting .ovrhdot.VCO2 of the sheep were removed from the venous blood by the CDML, there were proportional reductions in pulmonary CO2 excretion and in minute volume of ventilation (.ovrhdot.VE); when CO2 was removed by the CDML at a rate equal to its metabolic production by the sheep, .ovrhdot.VE fell to zero, with normal values of arterial PCO2 [CO2 partial pressure] pH and PO2. Effective respiratory rhythm generation evidently is critically dependent on stimuli related to .ovrhdot.VCO2.