Effect of Cooling the Cervical Vagi on the Work of Breathing

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

Intrathoracic pressures and tidal volumes were measured simultaneously in anesthetized dogs while the vagi were warm (intact) and cooled (blocked). Pressure-volume loops constructed from these tracings showed that both elastic and viscous work increased during vagal cooling. The magnitude of the increase in work per breath was such that respiratory work per minute also increased even though respiratory frequency was reduced. It is suggested that the regulation of depth and frequency of breathing by the respiratory center is less economical when afferent discharges from pulmonary receptors are blocked.