Compensatory alveolar growth normalizes gas-exchange function in immature dogs after pneumonectomy

To determine the extent and sources of adaptive response in gas-exchange to major lung resection during somatic maturation, immature male foxhounds un derwent right pneumonectomy (R-Pnx, n = 5) or right thoracotomy without pne umonectomy (Sham, n = 6) at 2 mo of age. One year after surgery, exercise c apacity and pulmonary gas-exchange were determined during treadmill exercis e. Lung diffusing capacity (DL) and cardiac output were measured by a rebre athing technique. In animals after R-Pnx, maximal Oz uptake, lung volume, a rterial blood gases, and DL during exercise were completely normal. Postmor tem morphometric analysis 18 mo after R-Pnx (n = 3) showed a vigorous compe nsatory increase in alveolar septal tissue volume involving all cellular co mpartments of the septum compared with the control lung; as a result, alveo lar-capillary surface areas and DL estimated by morphometry were restored t o normal. In both groups, estimates of DL by the morphometric method agreed closely with estimates obtained by the physiological method during peak ex ercise. These data shaw that extensive lung resection in immature dogs stim ulates a Vigorous compensatory growth of alveolar tissue in excess of matur ational lung growth, resulting in complete normalization of aerobic capacit y and gas-exchange function at maturity.