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 dimensions were determined in rabbits in the prone, supine, and right and left lateral positions with a high-speed electron beam X-ray computed 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 after surgery: sham-operated controls, left pneumonectomized, and left pneumonectomized with wax plombage. The magnitudes of the gradients in each direction (lung length, width, and height) depended on lung volume and body position. The vertical gradient in air content was the largest in each group in each posture. In general, pneumonectomy did not influence the effects of the prone and supine positions on lung volume and volume distribution but did influence the effects of the right and left lateral positions on those variables. These results may be attributed to the variable effects of the mediastinal and abdominal contents on regional distending pressures.