Dynamic lung function in dogs with compensatory lung growth.

Nine puppies underwent left pneumonectomy at 10 wk of age while nine sex-matched littermates had a sham operation, and all animals were studied at 25 wk of age. Postpneumonectomy dogs demonstrated compensatory growth in that lung weight and total lung capacity (TLC) were the same as those of control animals when normalized for body weight. In postpneumonectomy dogs all lobes of the remaining right lung increased in weight, but this was most notable in the cardiac lobe which grew across the mediastinum. Subdivisions of lung volume were normal in postpneumonectomy animals except for residual volume (RV): RV/TLC was increased when compared with control animals. In intact dogs static pressure-volume curves of the lung and respiratory system did not differ between groups, and the static pressure-volume curves of excised lungs were closely similar. Maximum expiratory flow was sharply reduced in postpneumonectomy dogs, averaging 40% of flow in control dogs over the lower 50% of the vital capacity. In both groups the fractional increase in maximal expiratory flow during HeO2 breathing was substantial and similar. Regional compliances, resistances, and perfusion distribution were examined using 133Xe. Regional compliance and perfusion were reduced in the left hemithorax of postpneumonectomy dogs while regional resistances were increased.