Respiratory Response of Anesthetized Dogs to Progressive Anemic Hypoxia

¹ From the Department of Physiology and Pharmacology, Duke University School of Medicine, Durham, North Carolina

Breath-to-breath analyses of air-flow responses of lightly anesthetized dogs to progressive anemic hypoxia by hemodilution or by breathing dilute carbon monoxide in air reveal only moderate changes in pulmonary ventilation. However, tidal volume undergoes progressive diminution, the alveolar ventilation remaining normal or slightly above normal by the concurrent increase in breathing rate. Despite the increase in breathing rate, hypoventilation and respiratory failure ensue when but 20–30% of the blood oxygen capacity is present. Administration of oxygen of high concentration to severely hypoxic dogs increases tidal volume, usually slowing the rate. The experimental method described lends itself to the study of factors which regulate and control pulmonary ventilation in the absence of chemoreceptor activity and when diminished blood oxygen capacity is the primary disturbing factor.