Esophageal elastance in awake and anesthetized recumbent dogs

Abstract
Esophageal elastance was measured in trained dogs placed in the prone, supine and left lateral postures before and during sodium thiopental anesthesia. Esophageal elastance was measured from the static pressure-volume curves and during spontaneous breathing at functional residual capacity. There was a significant decrease in esophageal elastance, estimated from the pressure-volume curves, during anesthesia in both prone and lateral positions but not in the supine posture. Changes in vagal tone produced by stimulation of the vagal nerves did not alter esophageal elastance. The underlying mechanisms for these changes in esophageal elastance are not fully understood. There was an increase in esophageal elastance when lung volumes increased from 55-80% total lung capacity. There was not a significant change in esophageal elastance between awake and anesthetized conditions or between positions during spontaneous breathing at functional residual capacity.