Stereophotogrammetric analysis of changes in body volume associated with the induction of anaesthesia

Changes in the volume of the trunk were measured in seven supine patients, when anaesthesia was induced with thiopentone i.v. Stereo-photograms were taken before and after induction and measurements of volume calculated from contour plots of a reconstructed stereo image. The changes in volume of the visible part of the trunk were between -846 and +505 ml. No systematic change in total or lower trunk ("abdominal") volume was evident, but there was a significant negative linear relationship (r = -0.87) between upper trunk ("ribcage") volume change and obesity (expressed as actual weight/expected weight). Changes in volume were more evident in the upper parts of the supine subject, in both ribcage and abdomen (P less than 0.05).