THE CAUSE OF CARDIAC SLOWING ACCOMPANYING POSTURAL APNEA IN THE DUCK

Abstract

There is a slowing of the heart during postural and submergence apnea, reaching its maximum after 15 sec. There is a corresponding rise of blood pressure at times amounting to more than 100%. The slowing of the heart and blood pressure elevation are due to insufficient ventilation and increased CO2 content of the blood. The authors advance a number of evidences to prove this contention. Among others, continuous insufflation of the animal during postural apnea prevents the appearance of cardiac inhibition and blood pressure elevation, or when these are already in evidence, it speeds up the heart rate again and lowers the blood pressure almost immediately.