Esophageal elastance in awake and anesthetized recumbent dogs

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 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. Therefore, 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 to 80% total lung capacity. However, we did not find a significant change in esophageal elastance between awake and anesthetized conditions or between positions during spontaneous breathing at functional residual capacity.