Figure 6. Curvature of the anterior border of the vertebral bodies of the thoracic spine, measured in a midsagittal section. Solid lines denote the curvature while awake and are duplicated for each subject for clarity; dashed lines show curvature during anesthesia, either during spontaneous breathing (S) or during mechanical ventilation with paralysis (M). Note that anesthesia with spontaneous breathing consistently increased spinal curvature, and the paralysis caused no further changes.