Respiratory mechanics in recumbent dogs anesthetized with thiopental sodium

Pressure-volume (PV) and conductance-volume (GV) curves were obtained in trained dogs awake and then anesthetized with thiopental sodium, in the prone left lateral decubitus, and supine positions. By paired analyses, induction of anesthesia had no significant effect on lung volumes, static PV curves of the lung or chest wall, or static compliance of the lung or chest wall. In addition, change of posture had little effect on these variables in either the awake or the anesthetized state. Frequently, however, individual dogs showed changes in lung PV curves after induction of anesthesia or change of posture. These PV curve shifts were not accompanied by predictable changes in GV relations. Therefore, we concluded that such changes in the lung PV curve reflect either local artifacts or local deformation of the respiratory system.