Brain hypoxia and control of breathing: role of the vagi

an important role in the generation of respiratory responses to various stimuli. This study examined the role of vagally medi-ated mechanisms in the generation of the respiratory responses to progressive brain hypoxia secondary to carboxyhemoglobi-nemia (HbCO O-55%) in six unanesthetized goats. Ventilation, respiratory cycle timing, and the lung inflation reflex were measured before and during CO inhalation in intact and bilat-erally vagotomized animals. Our results indicate that vagal reflexes contribute a small magnitude of the hyperpnea. caused by carboxyhemoglobinemia. Furthermore, in contrast to that reported for CO, inhalation, the tachypneic nature of the venti-latory response to CO is not a vagally mediated phenomenon. CO inhalation had a biphasic influence on the strength of the lung inflation reflex measured as the ratio of inspiratory time during occlusion (TIN & to inspiratory time of the precedin