LUNG-VOLUMES AND DISTRIBUTION OF REGIONAL AIR CONTENT DETERMINED BY CINE X-RAY CT OF PNEUMONECTOMIZED RABBITS

Lung volume, gradients in lung air content, and maximum in vivo lung d imensions were determined in rabbits in the prone, supine, and right a nd left lateral positions with a high-speed electron beam X-ray comput ed tomography scanner (Imatron C-100). Measurements were made at lung volumes corresponding to tracheal pressures of 0, 10, and 25 cmH(2)O. Three groups of rabbits were studied greater than or equal to 8 wk aft er surgery: sham-operated controls, left pneumonectomized, and left pn eumonectomized with wax plombage. The magnitudes of the gradients in e ach direction (lung length, width, and height) depended on lung volume and body position. The vertical gradient in air content was the large st in each group in each posture. In general, pneumonectomy did not in fluence the effects of the prone and supine positions on lung volume a nd volume distribution but did influence the effects of the right and left lateral positions on those variables. These results may be attrib uted to the variable effects of the mediastinal and abdominal contents on regional distending pressures.